WO2015115330A1 - Thin-film transistor, oxide semiconductor, and method for producing same - Google Patents

Abstract

The present invention addresses the problem of providing: a thin-film transistor that achieves a good balance between suppressing property deterioration due to light irradiation, low contact resistance, and excellent gate controllability; and a method for producing the same. The problem is solved by this thin-film transistor comprising a source electrode, a drain electrode, a semiconductor layer that is provided so as to be in contact with the source electrode and the drain electrode, a gate electrode that is provided so as to correspond to a channel between the source electrode and the drain electrode, and an insulator layer that is provided between the gate electrode and the semiconductor layer. The semiconductor layer is formed from a composite metal oxide obtained by adding, to a first metal oxide capable of generating electron carriers by means of introduction of oxygen defects, a second oxide having an oxygen dissociation energy larger than the oxygen dissociation energy of the first metal oxide by 200 kJ/mol or more; and the concentration of a specific element among the elements constituting the second oxide is the maximum value or the minimum value in the center portion of the semiconductor layer in the thickness direction.

Description

Thin film transistor, oxide semiconductor, and manufacturing method thereof

The first to third inventions of the present application relate to an oxide thin film transistor and a method for manufacturing the same.
The fourth invention of the present application also relates to a thin film transistor and a method for manufacturing the same.
Further, the fifth invention of the present application relates to an oxide semiconductor, a manufacturing method thereof, a thin film transistor using the same, and a semiconductor device.

Thin film transistors (TFTs) are widely used as switching elements for liquid crystal displays and organic electroluminescence (EL) displays that employ an active matrix drive system.

As the TFT, a semiconductor layer (channel layer) using amorphous silicon or polysilicon is known. In recent years, in order to improve various characteristics, the semiconductor layer has an In (indium) -Zn (zinc) -O (IZO) system, an In-Ga (gallium) -Zn-O (IGZO) system, or Sn (tin). A TFT using a —Zn—O (SZO) -based metal oxide has been studied (for example, see Patent Document 1).

Since such a thin film transistor has n-type conductivity and exhibits higher channel mobility than amorphous silicon or polysilicon, it can be suitably used as a switching element for a high-definition display or a large-screen display. Although there are various theories about the mechanism of n-type conduction, it is said that oxygen vacancies are mainly introduced by desorption of oxygen to the indium oxide structure, and as a result, charge is generated to serve as a semiconductor layer. In addition, since a semiconductor layer made of a metal oxide does not exhibit p-type conduction in principle and has a very small off current, the use of a thin film transistor has an advantage that power consumption can be reduced.

Further, it has been proposed to use indium oxide doped with either tin, titanium, or tungsten in place of IZO or IGZO as a metal oxide constituting the semiconductor layer of the thin film transistor (see, for example, Patent Document 2).

Furthermore, it has also been proposed to give concentration gradients in the thickness direction to elements such as various metals and nitrogen in the semiconductor layers of these thin film transistors (see, for example, Patent Documents 3 to 6).

Since the thin film transistor is preferably used as a switching element of a liquid crystal display or an organic electroluminescence display as described above, a relatively high-intensity visible light is irradiated in its use. Among them, characteristics of relatively short wavelength (high energy) components, for example, light irradiation with a wavelength of 420 nm (2.95 eV) may deteriorate characteristics such as a shift in threshold voltage of a thin film transistor. ing. Further, in the thin film transistor, it is desirable that the contact resistance at the interface between the source electrode and / or drain electrode and the semiconductor layer is low, that the electron mobility is high, and that the gate controllability is excellent, and that these characteristics are also excellent. It has been.

Further, the IZO, IGZO, and SZO metal oxides, which are metal oxides described in Patent Document 1, can easily react with the water in the Zn, Ga, and Sn contained therein. As a physical structure, unstable suboxide is formed, and the amount of oxygen vacancies cannot be adjusted, resulting in a problem of greatly degrading transistor characteristics.

In order to solve these problems, Patent Document 7 discloses, as a metal oxide, a material containing at least one element of zinc and tin, yttrium, niobium, tantalum, hafnium, lanthanum, scandium, vanadium, titanium, magnesium. It is disclosed that at least one of aluminum, gallium and silicon is used. In addition, in order to suppress fluctuations in threshold voltage caused by the destruction effect due to plasma damage and the increase in carriers due to radiation effects in the thin film transistor manufacturing stage, at least one of gallium, indium, tin, zirconium, hafnium, and vanadium is added to zinc oxide. It is disclosed to dope one ion (Patent Document 8). Furthermore, electrical characteristics of an oxide film transistor of an IZO metal oxide doped with tantalum have been reported (Non-Patent Document 1). However, in any of the above cases, since zinc is contained as a main element, there is a serious problem that a considerable limitation is imposed on the process in order to suppress the formation of suboxides in the thin film transistor manufacturing stage.

Furthermore, there is a report that indium oxide doped with either tin, titanium, or tungsten is used instead of IZO or IGZO as a metal oxide (Patent Document 2). However, in the oxide film transistor using indium oxide doped with either titanium or tungsten described in the above document as the metal oxide, the amount of oxygen vacancies introduced into the main structure indium oxide is adjusted at the metal oxide production stage. There is a big problem that the manufacturing process is limited because it is very difficult to do.

The inventors of the present invention have described that the oxygen separation energy of the metal (Me) -O bond or nonmetal-O bond to the first metal oxide such as indium oxide is 200 kJ / mol than the oxygen separation energy of the first metal oxide. A thin film transistor in which the amount of oxygen vacancies in the above problem was controlled by adding a large oxide as described above and a method for manufacturing the same were filed (Japanese Patent Application No. 2013-099284). However, in order to satisfy other various requirements while solving the above-mentioned problem, by finding a means for solving the above-mentioned problem other than the conditions described in the above-mentioned prior patent application, It remains desirable to have as much design freedom as possible.

In addition, as described above, a semiconductor layer (channel layer) using amorphous silicon or polysilicon used for a TFT is known. In recent years, various metals are used for a semiconductor layer in order to improve various characteristics. A TFT using an oxide has been studied (for example, see Patent Document 1).

Further, Patent Document 9 discloses a semiconductor device including a transistor in which a source electrode layer and a drain electrode layer are provided in contact with an oxide semiconductor film.
In Patent Document 10, in a method for manufacturing a semiconductor device using an oxide semiconductor, an oxide semiconductor film, a gate insulating film provided over the oxide semiconductor film, a gate electrode in contact with the gate insulating film, and a gate A step of forming a sidewall insulating film in contact with the electrode and a source electrode and a drain electrode in contact with the oxide semiconductor film, and the gate insulating film and the sidewall insulating film release oxygen contained in the oxide semiconductor film. A method of forming at a temperature lower than the temperature at which separation is suppressed is disclosed.

Patent Document 11 discloses a gate electrode on an insulating substrate, a gate insulating film on the gate electrode, an oxide semiconductor film containing indium on the gate insulating film, and a source / drain on the oxide semiconductor film. The XPS spectrum in the oxide semiconductor region where the peak position due to the indium 3d orbit of the XPS spectrum in the surface layer of the oxide semiconductor film where the source / drain electrodes do not overlap is present in the lower part of the surface layer. A TFT that is shifted to a higher energy side than the peak position due to the indium 3d orbital is disclosed.

JP 2011-4425 A JP 2008-192721 A JP 2013-105814 A JP 2012-134472 A JP2011-129926A JP 2010-156994 A JP 2013-70052 A JP 2010-21520 A JP 2013-138188 A JP 2013-219336 A JP 2013-41968 A

APPLIED PHYSICS LETTERS 102, 102102 (2013).

The first to third inventions of the present application have been made in view of such circumstances, and the first metal oxide capable of generating electron carriers by introducing oxygen vacancies into the semiconductor layer (channel layer), A thin film transistor using a composite metal oxide to which a second oxide having a larger oxygen dissociation energy than that of the first metal oxide is added at least 200 kJ / mol and having a specific element distribution. An object of the present invention is to provide a thin film transistor and a method for manufacturing the same, which are compatible with suppression of characteristic deterioration due to light irradiation, low contact resistance, and excellent gate controllability.

The subject of the 4th invention of this application is providing the thin-film transistor which solves the said problem on composition conditions other than having shown by the prior patent application mentioned above, and its manufacturing method.

On the other hand, a light emitting layer is used for an organic EL display or a liquid crystal display. In particular, light emission from the blue light emitting layer having the highest energy, that is, light emitted at a short wavelength has a peak at 450 nm, and the bottom of the emission spectrum extends to 420 nm on the short wavelength side. For this reason, since the thin film transistors constituting the organic EL display and the liquid crystal display are irradiated with light from the light emitting layer, it is desired that the thin film transistor be highly resistant to deterioration with respect to light irradiation having the above wavelength. It is rare. Here, it is difficult to deteriorate against light irradiation from the light emitting layer. Specifically, the oxide semiconductor constituting the thin film transistor emits light from the light emitting layer (specifically, a wavelength of 420 nm to 600 nm). “Threshold voltage shift” induced by light irradiation (where “threshold voltage shift” refers to a phenomenon in which the threshold voltage shifts to the negative side due to light emission from the light emitting layer). .) Can be suppressed. Therefore, in order to provide a highly reliable thin film transistor, an oxide semiconductor that can sufficiently suppress this “threshold voltage shift” is desired.

However, any of the oxide semiconductor films disclosed in the above-mentioned patent documents has a problem that the “threshold voltage shift” induced by light emission from the light emitting layer cannot be sufficiently suppressed.

Therefore, an oxide semiconductor used for a thin film transistor constituting an organic EL display or a liquid crystal display is desired to be able to sufficiently suppress a “threshold voltage shift” induced by light emission from a light emitting layer.

The fifth invention of the present application was made in view of such circumstances, and an oxide semiconductor capable of sufficiently suppressing a “threshold voltage shift” induced by light emission from the light emitting layer, a manufacturing method thereof, and It is an object to provide a thin film transistor and a semiconductor device using the thin film transistor.

Note that the semiconductor device in this specification includes all devices using a transistor made of a semiconductor. Therefore, for example, an organic EL display and a liquid crystal display are also included in this.

As a result of intensive studies, the present inventor has at least one element X selected from the group consisting of silicon, tantalum, zirconium, hafnium, aluminum, yttrium and rare earth elements among the elements X constituting the second oxide (XOx). It has been found that a thin film transistor in which the concentration of ¹ exhibits a maximum value in the central portion in the thickness direction of the semiconductor layer solves the above problems, and has led to the first to third inventions of the present application.
That is, the first invention of the present application is
[1] a source electrode and a drain electrode;
A semiconductor layer provided in contact with the source electrode and the drain electrode;
A gate electrode provided corresponding to a channel between the source electrode and the drain electrode;
A thin film transistor having an insulator layer provided between the gate electrode and the semiconductor layer,
The semiconductor layer has a second metal oxide that can generate electron carriers by introducing oxygen vacancies, and the second energy of oxygen is 200 kJ / mol or more higher than that of the first metal oxide. Formed of a complex metal oxide to which an oxide (XOx) is added,
Among the elements X constituting the second oxide, the concentration of at least one element X ¹ selected from the group consisting of silicon, tantalum, zirconium, hafnium, aluminum, yttrium, and rare earth elements is in the thickness direction of the semiconductor layer. The present invention relates to the above-described thin film transistor, which exhibits a maximum value at the center.

The following [2] is a preferred embodiment of the first invention of the present application. [2] In the above [1], the concentration of the element X ¹ shows a maximum value in the central portion in the thickness direction of the semiconductor layer. The thin film transistor described.

The second invention of the present application is
[3] a source electrode and a drain electrode;
A semiconductor layer provided in contact with the source electrode and the drain electrode;
A gate electrode provided corresponding to a channel between the source electrode and the drain electrode;
A thin film transistor having an insulator layer provided between the gate electrode and the semiconductor layer,
The semiconductor layer has a second metal oxide that can generate electron carriers by introducing oxygen vacancies, and the second energy of oxygen is 200 kJ / mol or more higher than that of the first metal oxide. Formed of a complex metal oxide to which an oxide (XOx) is added,
Among the elements X constituting the second oxide, the concentration of at least one element X ² that does not correspond to any of silicon, tantalum, zirconium, hafnium, aluminum, yttrium, and rare earth elements is in the thickness direction of the semiconductor layer. The present invention relates to the above-described thin film transistor that exhibits a minimum value in the center.

The following [4] is a preferred embodiment of the second invention of the present application [4] In the above [3], the concentration of the element X ² shows a minimum value in the central portion in the thickness direction of the semiconductor layer. The thin film transistor described.
The third invention of the present application is
[5] a source electrode and a drain electrode;
A semiconductor layer provided in contact with the source electrode and the drain electrode;
A gate electrode provided corresponding to a channel between the source electrode and the drain electrode;
A thin film transistor having an insulator layer provided between the gate electrode and the semiconductor layer,
The semiconductor layer has a second metal oxide that can generate electron carriers by introducing oxygen vacancies, and the second energy of oxygen is 200 kJ / mol or more higher than that of the first metal oxide. Formed of a complex metal oxide to which an oxide (XOx) is added,
The said thin film transistor is related with the said thin-film transistor in which the said semiconductor layer contains nitrogen further, and the density | concentration of nitrogen shows the maximum value in the center part of the thickness direction of the said semiconductor layer.
[6] to [17] are preferred embodiments of the first to third inventions of the present application [6].
The thin film transistor according to any one of [1] to [5], wherein the oxygen separation energy of the second oxide is greater than or equal to 255 kJ / mol than the oxygen separation energy of the first metal oxide.
[7]
The thin film transistor according to any one of [1] to [5], wherein the first metal oxide is an oxide of at least one metal selected from the group consisting of indium, gallium, zinc, and tin. .
[8]
The second oxide according to any one of [1] to [5], wherein the second oxide is an oxide of at least one metal selected from the group consisting of zirconium (Zr) and praseodymium (Pr). Thin film transistor.
[9]
The thin film transistor according to [6], wherein the second oxide is at least one oxide selected from the group consisting of silicon (Si), tantalum (Ta), lanthanum (La), and hafnium (Hf). .
[10]
The thin film transistor according to any one of [1] to [9], wherein the content of the second oxide in the semiconductor layer is greater than 0 and equal to or less than 50% by weight.
[11]
The thin film transistor according to any one of [1] to [10], wherein the content of the second oxide in the semiconductor layer is greater than 0 and 5% by weight or less.
[12]
The thin film transistor according to any one of [1] to [11], wherein the semiconductor layer is amorphous.
[13]
The thin film transistor according to any one of [1] to [12], wherein the thickness of the semiconductor layer is in the range of 5 nm to 20 nm.
[14]
The thin film transistor according to any one of [1] to [5], wherein the second oxide is an oxide of at least one element selected from the group consisting of boron (B) and carbon (C). .
[15]
The thin film transistor according to the above [14], wherein the content of boron (B) and carbon (C) in the semiconductor layer is greater than 0 and 10% by weight or less.
[16]
The semiconductor layer is formed at a temperature of 10 ° C. or higher and 400 ° C. or lower;
The method for producing a thin film transistor according to any one of [1] to [15] above.
[17]
The method for producing a thin film transistor according to [16], wherein the semiconductor layer is formed at a temperature of 10 ° C. or higher and 200 ° C. or lower.
[18]
The apparatus which has a thin-film transistor of any one of said [1] to [15].
[19]
The device according to [18], which is a liquid crystal display or an organic EL display.

[20]
Furthermore, according to one aspect of the present invention, a source electrode and a drain electrode, a semiconductor layer provided in contact with the source electrode and the drain electrode, and a channel between the source electrode and the drain electrode are supported. And an insulating layer provided between the gate electrode and the semiconductor layer. The semiconductor layer has tin oxide, an oxygen separation energy larger than that of tin oxide, and an oxide layer. A thin film transistor which is a composite metal oxide to which a metal oxide having a difference from the separation energy of oxygen of tin of less than 200 kJ / mol is added is provided.
[21]
Here, the semiconductor layer may include an additional oxide whose oxygen dissociation energy is smaller than that of tin oxide in an amount smaller than that of the metal oxide.
[22]
The content of the additional oxide in the semiconductor layer may be 20% by weight or less.
[23]
The content of the additional oxide in the semiconductor layer may be 4% by weight or less.
[24]
The semiconductor layer may be amorphous.
[25]
The semiconductor layer may have a thickness of 5 nm to 20 nm.
[26]
The additional oxide may be at least one oxide selected from the group consisting of lead, palladium, platinum, sulfur, antimony, strontium, thallium, and ytterbium.
[27]
The metal oxide may be at least one oxide selected from the group consisting of samarium, tungsten, neodymium, and gadolinium.
[28]
The content of the metal oxide in the semiconductor layer may be greater than 0 and 50% by weight or less.
[29]
Further, the content of the metal oxide in the semiconductor layer may be 5% by weight or less.
[30]
According to another aspect of the fourth invention of the present application, there is provided a method for producing any one of the above thin film transistors, wherein the semiconductor layer is formed at 10 ° C. or more and 500 ° C. or less.
[31]
Here, you may form the said semiconductor layer at 10 degreeC or more and 300 degrees C or less.

In addition, as a result of intensive studies to solve the above problems, the present inventor has found that the first metal oxide made of a metal oxide capable of generating electron carriers by introducing oxygen vacancies and the oxygen separation energy are the first. An oxide semiconductor into which oxygen vacancies are introduced is formed, which includes a second oxide that is 200 kJ / mol or more larger than the oxygen separation energy of one metal oxide, and further has OH as a substituent in the oxygen vacancies. When the oxide semiconductor in which at least one selected from the group consisting of a group, an H group, an F group, a Cl group, or a B group is introduced and bonded to the metal of the first metal oxide is used as a thin film transistor, It has been found for the first time that the “threshold voltage shift” induced by light emission from the light emitting layer can be sufficiently suppressed.

That is, the fifth invention of the present application has a configuration shown in the following [32] to [57].

[32] A first metal oxide made of a metal oxide capable of generating electron carriers by introducing oxygen vacancies, and an oxygen separation energy of 200 kJ / mol or more than the oxygen separation energy of the first metal oxide. An oxide semiconductor comprising a large second oxide, wherein the metal of the first metal oxide is at least selected from the group consisting of an OH group, an H group, an F group, a Cl group, or a B group The oxide semiconductor having a bond with one.
[33] The oxide semiconductor according to [32], wherein the oxygen separation energy of the second oxide is greater than or equal to 255 kJ / mol than the oxygen separation energy of the first metal oxide.
[34] The oxide semiconductor according to [32], wherein the metal of the first metal oxide is at least one selected from the group consisting of indium, gallium, zinc, and tin.
[35] The second oxide includes silicon (Si), titanium (Ti), tungsten (W), tantalum (Ta), lanthanum (La), hafnium (Hf), zirconium (Zr), and praseodymium (Pr). The oxide semiconductor according to any one of [32] to [34], which is an oxide containing at least one selected from the group consisting of:
[36] The second oxide is at least one selected from the group consisting of silicon (Si), titanium (Ti), tungsten (W), tantalum (Ta), lanthanum (La), and hafnium (Hf). [35] The oxide semiconductor according to [35].
[37] The oxide semiconductor according to any one of [32] to [36], wherein the content of the second oxide is greater than 0 and equal to or less than 50% by weight.
[38] The oxide semiconductor according to [37], wherein the content of the second oxide is greater than 0 and 5% by weight or less.
[39] The oxide semiconductor according to any one of [32] to [38], wherein the thickness of the oxide semiconductor is in the range of 5 nm to 20 nm.
[40] The oxide semiconductor according to any one of [32] to [39], wherein the second oxide is an oxide containing carbon (C).
[41] The oxide semiconductor according to [40], wherein the content of carbon (C) is greater than 0 and 10% by weight or less.
[42] The oxide semiconductor according to [32], wherein the metal of the first metal oxide is indium, and the oxygen separation energy of the second oxide is 725 kJ / mol or more.
[43] The oxide semiconductor according to any one of [32] to [42], wherein the metal of the first metal oxide has a bond with an OH group.
[44] The oxide semiconductor according to [43], wherein the content of the OH group is 0.1% or more and 10% or less.
[45] The oxide semiconductor according to any one of [32] to [42], wherein the metal of the first metal oxide has a bond with an H group.
[46] The oxide semiconductor according to [45], wherein the content of the H group is greater than 0% and 0.1% or less.
[47] Any of [32] to [42], wherein the metal of the first metal oxide has a bond with at least one selected from the group consisting of an F group, a Cl group, or a B group. The oxide semiconductor according to claim 1.
[48] The content of at least one selected from the group consisting of the F group, the Cl group, or the B group is more than 5 × 10 ¹⁸ atoms / cm ^{3 and not} more than 1 × 10 ²¹ atoms / cm ³ [47] An oxide semiconductor according to 1.
[49] The oxide semiconductor according to any one of [32] to [48], wherein the oxide semiconductor is amorphous.
[50] A thin film transistor comprising the oxide semiconductor according to any one of [32] to [49].
[51] a source electrode and a drain electrode;
A semiconductor layer provided in contact with the source electrode and the drain electrode;
A gate electrode provided corresponding to a channel between the source electrode and the drain electrode;
Providing an insulator layer provided between the gate electrode and the semiconductor layer;
A thin film transistor, wherein the semiconductor layer is formed of the oxide semiconductor according to any one of [32] to [49].
[52] A semiconductor device comprising the thin film transistor according to [51].
[53] The method for manufacturing an oxide semiconductor according to any one of [32] to [49], wherein the semiconductor layer is formed at 10 ° C. or higher and 400 ° C. or lower.
[54] The method for manufacturing an oxide semiconductor according to any one of [32] to [49], wherein the semiconductor layer is formed at 10 ° C. or higher and 200 ° C. or lower.
[55] The first metal oxide powder made of a metal oxide capable of generating electron carriers by introducing oxygen vacancies, and the oxygen separation energy of the first metal oxide is 200 kJ / day higher than the oxygen separation energy of the first metal oxide. By a physical vapor deposition method using a target composed of a sintered body of a second oxide powder larger than mol and a mixed gas composed of a rare gas and oxygen and not containing a compound having hydrogen atoms, Forming an oxide semiconductor including a first metal oxide and the second oxide;
Forming the oxide semiconductor having oxygen vacancies by heat-treating the oxide semiconductor at 150 ° C. in the atmosphere;
By heat-treating the oxide semiconductor having oxygen vacancies in a temperature range of 150 to 300 ° C. under a high humidity of 80% or more introduced with H ₂ O gas, the metal of the first metal oxide, the OH group, and The method for producing an oxide semiconductor according to [43] or [44], including a step of forming a bond.
[56] The first metal oxide powder made of a metal oxide capable of generating electron carriers by introducing oxygen vacancies, and the oxygen separation energy of the first metal oxide is 200 kJ / day higher than the oxygen separation energy of the first metal oxide. By a physical vapor deposition method using a target composed of a sintered body of a second oxide powder larger than mol and a mixed gas composed of a rare gas and oxygen and not containing a compound having hydrogen atoms, Forming an oxide semiconductor including a first metal oxide and the second oxide;
Forming the oxide semiconductor having oxygen vacancies by heat-treating the oxide semiconductor at 150 ° C. in the atmosphere;
Forming a bond between the metal of the first metal oxide and an H group by heat-treating the oxide semiconductor having oxygen vacancies in a temperature range of 300 to 400 ° C. in an H ₂ atmosphere gas. [45] or [46], The manufacturing method of the oxide semiconductor.
[57] The first metal oxide powder made of a metal oxide capable of generating electron carriers by introducing oxygen vacancies, and the oxygen separation energy of the first metal oxide is 200 kJ / day higher than the oxygen separation energy of the first metal oxide. By a physical vapor deposition method using a target composed of a sintered body of a second oxide powder larger than mol and a mixed gas composed of a rare gas and oxygen and not containing a compound having hydrogen atoms, Forming an oxide semiconductor including a first metal oxide and the second oxide;
Forming the oxide semiconductor having oxygen vacancies by heat-treating the oxide semiconductor at 150 ° C. in the atmosphere;
By ion-implanting at least one selected from the group consisting of fluorine ions, chlorine ions, or boron ions into the oxide semiconductor having oxygen vacancies, the ions of the metal of the first metal oxide are implanted. A method for forming an oxide semiconductor according to [47] or [48].

According to the first to third inventions of the present application, characteristic deterioration such as threshold current shift due to light irradiation is suppressed, contact resistance at the interface between the source electrode and / or drain electrode and the semiconductor layer is low, and electron transfer is suppressed. A thin film transistor having a high level of practically preferable characteristics of high degree and excellent gate controllability, and a method for manufacturing the same are realized.

According to the fourth aspect of the present invention, when a tin oxide having a large oxygen separation energy of 528 kJ / mol is used as a metal oxide capable of generating electron carriers by introducing oxygen defects, the metal oxide added thereto is In addition, the composite metal oxidation in which the oxygen separation energy of the added metal oxide is larger than the oxygen separation energy of tin oxide and the difference from the oxygen separation energy of tin oxide is less than 200 kJ / mol. A thin film transistor with excellent transistor characteristics can be provided by using a semiconductor layer.
According to the fourth invention of the present application, in addition to the metal oxide to be added, an oxide having an oxygen separation energy smaller than that of tin oxide is added in an amount smaller than that of the metal oxide to be added. By using a semiconductor layer of a composite metal oxide, a thin film transistor having excellent transistor characteristics can be provided.

According to the fifth invention of the present application, it is possible to provide an oxide semiconductor capable of sufficiently suppressing “threshold voltage shift” induced by light emission from the light emitting layer. Therefore, a thin film transistor using the oxide semiconductor, an organic EL display using the thin film transistor, and a liquid crystal display can have high reliability that the light emission from the light emitting layer hardly deteriorates.

Incidentally, Patent Document 9 discloses that the above oxide processed into an island shape in a semiconductor device having a transistor in which a source electrode layer and a drain electrode layer are provided in contact with an oxide semiconductor film such as an IZO or IGZO system. The concentration of fluorine, chlorine, and boron in a region not overlapping with the source electrode layer and the drain electrode layer on the side surface portion of the semiconductor film is disclosed. However, this fluorine, chlorine, and boron are impurities contained in the etching gas, and must be removed as much as possible by the impurity removal treatment by solution cleaning in order to prevent the formation of parasitic channels due to their contamination. (See paragraphs 0184 and 0185, for example). In fact, these concentrations are clearly shown to be very low, 5 × 10 ¹⁸ atoms / cm ³ or less for fluorine and chlorine and 1 × 10 ¹⁶ atoms / cm ³ or less for boron (see, for example, paragraph 0225). Therefore, in Patent Document 9, it is not recognized that the metal constituting the oxide semiconductor film is bonded to such an extremely low concentration of fluorine, chlorine, or boron. Therefore, in the oxide semiconductor film described in Patent Document 9, the above effect according to the fifth invention of the present application cannot be obtained.

Patent Document 10 discloses that in a method for manufacturing a semiconductor device using an oxide semiconductor, one or more elements selected from boron, a rare gas element, and the like are used as a dopant. However, this patent document does not describe the amount of dopant. Here, considering that this dopant is implanted only to reduce the resistance of the oxide semiconductor in contact with the source electrode and the drain electrode, the amount of this dopant is very small, 5 × 10 ¹⁸ atoms. / Cm ³ is presumed not to exceed. Therefore, even in Patent Document 10, it is not recognized that the metal constituting the oxide semiconductor film is bonded to such an extremely low concentration of boron or a rare gas element.
In addition, in the structure of the oxide semiconductor described in Patent Document 10 (see, for example, paragraph 0149), a region of the oxide semiconductor film located in a portion masked with the gate electrode contains boron or a rare gas element. Not. That is, in Patent Document 10, in a region of an oxide semiconductor film (that is, a channel region) located in a portion masked with a gate electrode, a metal that forms the oxide semiconductor film is boron used as a dopant. It does not combine with noble gas elements.
Due to such differences, the oxide semiconductor film described in Patent Document 10 cannot obtain the above-described effect of the fifth invention of the present application.

In Patent Document 11, a surface layer is formed as a separate layer different from the oxide semiconductor film in a portion where the source / drain electrodes of the oxide semiconductor film do not overlap with each other, and chemicals of indium and fluorine are formed only on the surface layer. A TFT providing a bond is disclosed. In other words, the TFT described in Patent Document 11 does not introduce fluorine into the oxide semiconductor film existing under the surface layer as a separate layer different from the surface layer. On the other hand, in the fifth invention of the present application, a region mainly on the gate electrode side of the oxide semiconductor film functions as a channel region. Therefore, in the fifth invention of the present application, the dopant exists in at least the interface region with the gate electrode in the oxide semiconductor film (of course, the dopant may also exist in other regions). Therefore, in the oxide semiconductor film described in Patent Document 11, the above effect according to the fifth invention of the present application cannot be obtained.

1 is a schematic cross-sectional view of a thin film transistor according to an embodiment of the first invention of the present application. 1 is a schematic cross-sectional view of a thin film transistor according to an embodiment of the first invention of the present application. FIG. 6 shows a relationship between the composition of an In—Si—O film and a band gap. The figure which shows element concentration distribution of one Example of this-application 1st invention. The figure which shows element concentration distribution of one Example of this-application 3rd invention. The figure which shows the shift of the electron mobility and threshold voltage of one Example of this-application 1st invention. The figure which shows the Id-Vg characteristic of one Example of this-application 3rd invention. The schematic sectional drawing of the thin-film transistor which concerns on 1st Embodiment of this-application 4th invention. The schematic sectional drawing of another thin-film transistor which concerns on 2nd Embodiment of this-application 4th invention. The schematic sectional drawing of the thin-film transistor of the Example of this-application 4th invention. The figure which shows the Id-Vg characteristic of the thin-film transistor of 1st Example (Example B1) of this-application 4th invention. Shows a first embodiment the two _{O 2 / (O 2 + Ar} ) ratio and conductive relationship sputtering semiconductor material (Example B1) of the present fourth invention. The figure which shows the X-ray-diffraction pattern for confirming that the semiconductor film used by 2nd Example (Example B2) of this invention 4th invention is amorphous. The figure which shows the Id-Vd characteristic of the thin-film transistor of 2nd Example (Example B2) of this-application 4th invention. The schematic sectional drawing of the thin-film transistor which is one Embodiment of this-application 5th invention. The schematic sectional drawing of the thin-film transistor of the Example (Example C) of this-application 5th invention. In-Si-O semiconductor of Example C and In-Si-O semiconductor having In-OH bond ((a) In3dXPS spectrum of In-Si-O semiconductor, (b) In-Si having In-OH bond) -In3dXPS spectrum of -O semiconductor). Shows the comparison results of the _I d -V _g characteristics of the In-Si-O semiconductor with or without an In-OH bonds before and after light irradiation of a wavelength of 420nm ~ 600nm ((a) before irradiation In-Si-O semiconductor and the _I d -V _g characteristics of the in-Si-O semiconductor having an in-OH bonds before the light irradiation, the in-Si-O semiconductor having an in-OH bond after (b) irradiation _I d -V _g Characteristics, (c) I _d -V _g characteristics of In—Si—O semiconductor after light irradiation).

Hereinafter, a thin film transistor and a method of manufacturing the thin film transistor according to embodiments of the first to third inventions of the present application will be described with reference to the drawings. In all the following drawings, in order to make the drawings easy to see, the dimensions and ratios of the constituent elements are appropriately changed, and the actual dimensions and the ratios do not necessarily match.

The thin film transistor of the first invention of this application is:
A source electrode and a drain electrode;
A semiconductor layer provided in contact with the source electrode and the drain electrode;
A gate electrode provided corresponding to a channel between the source electrode and the drain electrode;
A thin film transistor having an insulator layer provided between the gate electrode and the semiconductor layer,
The semiconductor layer has a second metal oxide that can generate electron carriers by introducing oxygen vacancies, and the second energy of oxygen is 200 kJ / mol or more higher than that of the first metal oxide. Formed of a complex metal oxide to which an oxide (XOx) is added,
Among the elements X constituting the second oxide, the concentration of at least one element X ¹ selected from the group consisting of silicon, tantalum, zirconium, hafnium, aluminum, yttrium, and rare earth elements is in the thickness direction of the semiconductor layer. The thin film transistor having a maximum value in the center.
Here, the concentration of the specific element X ¹ is in the thickness direction of the semiconductor layer is continuously and substantially change, that is, the element X ¹ is a concentration gradient in the thickness direction of the semiconductor layer ing. More specifically, the concentration of the element X ¹ shows a maximum value, that is, at least one peak in the central portion in the thickness direction of the semiconductor layer. Here, the “central portion” refers to both the interfaces of the semiconductor layer (usually, the interface in contact with the interlayer insulating film on the source electrode and drain electrode side and the interface in contact with the insulator layer on the gate electrode side). It refers to a location 2 nm or more, or 5% or more of the thickness of the semiconductor layer.

Preferably, the at least one concentration of the element X ¹ represents the maximum value in the central portion in the thickness direction of the semiconductor layer. That is, the concentration of the element X ¹ in any location of the central portion in the thickness direction of the semiconductor layer is preferably higher than the concentration of the element X ¹ in any position of the semiconductor layer.

In the first invention, the concentration of the element X ¹ is, by indicating a maximum value in the central portion in the thickness direction of the semiconductor layer, characteristic deterioration such as a shift in the threshold current due to light irradiation can be suppressed, the source electrode And / or a remarkable technical effect that the contact resistance at the interface between the drain electrode and the semiconductor layer is low, the electron mobility is high, and the gate controllability is excellent is realized.

The thin film transistor of the first invention of the present application is preferably manufactured by a manufacturing method including a step of forming a semiconductor layer at 10 ° C. or higher and 400 ° C. or lower.

FIG. 1 is a schematic cross-sectional view of a thin film transistor 10 according to a preferred embodiment of the first invention of the present application. As the substrate 20, a substrate formed of a known forming material can be used, and any of those having optical transparency and those having no optical transparency can be used. For example, an inorganic substrate made of alkali silicate glass, quartz glass, silicon nitride, or the like; a silicon substrate; a metal substrate whose surface is insulated; acrylic resin, polycarbonate resin, PET (polyethylene terephthalate), or PBT (polybutylene) Various substrates such as a resin substrate made of a polyester resin such as terephthalate) or a paper substrate can be used. Further, the substrate may be a composite material formed by combining a plurality of these materials. The thickness of the substrate 20 can be appropriately set according to the design.

The thin film transistor 10 of this embodiment is a so-called bottom gate type transistor. The thin film transistor 10 includes a gate electrode 30 provided on the substrate 20, an insulator layer 40 provided to cover the gate electrode 30, a semiconductor layer 50 provided on the upper surface of the insulator layer 40, A source electrode 60 and a drain electrode 70 provided in contact with the semiconductor layer 50 on the upper surface, and an interlayer insulating film 80 are provided. The gate electrode 30 is provided corresponding to the channel region of the semiconductor layer 50 (at a position overlapping the channel region in a plan view). The semiconductor layer 50 is composed of a composite metal oxide obtained by adding a second oxide (XOx) to a first metal oxide capable of generating electron carriers by introducing oxygen vacancies. As a matter of course, the semiconductor layer may contain components other than the second oxide and inevitable impurities as long as the adverse effects of the first invention of the present application are not adversely affected.

Each of the gate electrode 30, the source electrode 60, and the drain electrode 70 can be made of a generally known material. Examples of the material for forming these electrodes include aluminum (Al), gold (Au), silver (Ag), copper (Cu), nickel (Ni), molybdenum (Mo), tantalum (Ta), and tungsten (W). Examples thereof include metal materials such as these, alloys thereof, and conductive oxides such as indium tin oxide (ITO) and zinc oxide (ZnO). Moreover, these electrodes may form the laminated structure of two or more layers, for example by plating the surface with a metal material.

The gate electrode 30, the source electrode 60, and the drain electrode 70 may be formed of the same forming material or may be formed of different forming materials. Since manufacture becomes easy, it is preferable that the source electrode 60 and the drain electrode 70 are the same formation material.

The insulator layer 40 has an insulating property, and any of an inorganic material and an organic material can be used as long as it can electrically insulate the gate electrode 30 from the source electrode 60 and the drain electrode 70. It may be formed. Examples of the inorganic material include normally known insulating oxides such as SiO ₂ , SiN _x , SiON, Al ₂ O ₃ , and HfO ₂ , nitrides, and oxynitrides. Examples of the organic material include acrylic resin, epoxy resin, silicon resin, and fluorine resin. The organic material is preferably a photocurable resin material because it is easy to manufacture and process.

The semiconductor layer 50 includes a second metal oxide having energy greater than that of the first metal oxide that can generate electron carriers by introducing oxygen vacancies by 200 kJ / mol or more. It is formed of a complex oxide containing an oxide. The first metal oxide is preferably a metal oxide including at least one selected from the group consisting of indium (In), gallium (Ga), zinc (Zn), and tin (Sn), and the second The oxide is preferably zirconium (Zr), silicon (Si), titanium (Ti), tungsten (W), tantalum (Ta), hafnium (Hf), scandium (Sc), yttrium (Y), lanthanum (La). Oxide containing at least one selected from the group consisting of praseodymium (Pr), neodymium (Nd), gadolinium (Gd), other rare earth elements, aluminum (Al), boron (B), and carbon (C) It is.
Preferably, when the element of the first oxide is In, the element of the second oxide is at least selected from the group consisting of Zr, Pr, Si, Ti, W, Ta, La, Hf, B, and C. In the case where the element of the first oxide is Sn and the element of the first oxide is Sn, the element of the second oxide is at least one element selected from the group consisting of Sc, Ti, W, Nd, and Gd.

When indium oxide (In ₂ O ₃ ) is used as the first metal oxide, the oxygen separation energy of indium oxide is as small as 346 ± 30 kJ / mol, so oxygen is easily desorbed from indium oxide to generate oxygen vacancies. It's easy to do. However, if the amount of oxygen vacancies becomes too large, it changes from semiconducting properties to metallic properties, making it unsuitable as a semiconductor layer. In order to solve this problem, in order to control the oxygen deficiency of indium oxide, a second oxide (XO _x ) having an oxygen separation energy of 200 kJ / mol / greater than the oxygen separation energy of indium oxide, more specifically, The second metal oxide, which is a metal oxide, or an equivalent nonmetallic element oxide as described later may be added. The oxygen separation energy of the second oxide is preferably larger than that specified above, and an oxide having an oxygen separation energy of 725 kJ / mol or more, more preferably 780 kJ / mol or more is used as the second oxide. When used, it is preferable because the oxygen deficiency of indium oxide can be easily controlled. In addition, when materials other than indium oxide are generalized as the first metal oxide, as described above, the oxygen separation energy of the second oxide is 200 kJ / mol or more as compared with the first metal oxide. Preferably a thing larger than 255 kJ / mol may be used. In the present embodiment, a metal oxide is preferably used as the second oxide, but as a particularly suitable metal oxide, Table A1 in which oxides having an oxygen separation energy of 780 kJ / mol or more are summarized and oxygen As shown in Table A2, which summarizes metal oxides having a separation energy of 725 kJ / mol to 780 kJ / mol, zirconium oxide (Zr—O), praseodymium oxide (Pr—O), lanthanum oxide (La—O), Examples include, but are not limited to, tantalum oxide (Ta—O) and hafnium oxide (Hf—O). Similarly, silicon oxide (Si—O) described in Table A1 is also preferable as the second oxide.

 

 

 

 

In the present embodiment, the second oxide added to make the first metal oxide a semiconductor layer having an appropriate oxygen deficiency is particularly preferably a second oxide of 780 kJ / mol or more shown in Table A1. Is more preferable. Specifically, lanthanum oxide (La—O), silicon oxide (Si—O), tantalum oxide (Ta—O), and hafnium oxide (Hf—O) can be given.

Further, the content of the second oxide added to the first metal oxide in order to make the first metal oxide a semiconductor layer having a suitable oxygen deficiency is not particularly limited, but is larger than 0 and 50% by weight. The following range is recommended. In particular, when the content of the second oxide added to the first metal oxide is in the range of more than 0 and 5% by weight or less, it is practically preferable in that it can be produced at a low temperature of 200 ° C. or less.

In-Zn-O-based and In-Ga-Zn-O-based metal oxides tend to be polycrystalline when a semiconductor layer is formed. Therefore, in a generally known thin film transistor, the surface of the semiconductor layer does not become flat due to crystal grains contained in the semiconductor layer. In addition, the normally known semiconductor layer of an oxide film transistor has a reduced electrical conductivity in the plane direction due to such crystal grains. Therefore, in order to obtain planarization of the surface of the semiconductor layer 50 and high electrical conductivity, the semiconductor layer preferably has an amorphous structure.

Further, the thickness of the semiconductor layer 50 is not particularly limited, but is preferably in the range of 5 nm or more and 20 nm or less. In the present embodiment, the thickness of the semiconductor layer 50 can be measured by using a crystal oscillation type film thickness meter arranged mainly for film thickness calibration in the sputtering chamber in which the semiconductor layer 5 is formed. .

In addition, the composite metal oxide which comprises the semiconductor layer 50 is not limited to what added the metal oxide as a 2nd oxide to the 1st metal oxide, and the separation energy is 200 kJ / in comparison with the 1st metal oxide. A non-metal oxide larger than mol may be added. Specifically, the composite metal oxide may be, for example, an oxide of at least one element selected from boron (B) and carbon (C) (ie, “composite metal oxide” in the present application). Is used to mean "an oxide in which a metal oxide is combined with an element having an energy greater than a predetermined value for oxygen"). This is because the oxygen desorption energy of the B—O bond is as large as 809 kJ / mol and the oxygen desorption energy of the C—O bond is as large as 1076.38 ± 0.67 kJ / mol, so that the amount of oxygen deficiency introduced into the first metal oxide This is because it can be easily controlled.

Present in the first invention, among the element X included in the second oxide, silicon, tantalum, zirconium, hafnium, aluminum, at least one of the concentration of the element X ¹ is selected from the group consisting of yttrium and rare earth elements, semiconductor The maximum value is shown at the center in the thickness direction of the layer. As a result, in the first invention of the present application, a remarkable technical effect having a high practical value is realized in that the shift of the threshold voltage of the thin film transistor due to irradiation with short-wavelength visible light, for example, light with a wavelength of 420 nm is suppressed. The Hereinafter, the case where the first metal oxide is indium oxide (In ₂ O ₃ ) will be described as an example.

In a composite oxide containing indium oxide (In ₂ O ₃ ), oxygen in the vicinity of the valence band of the In ₂ O ₃ band gap is caused by light absorption as a factor of the threshold voltage shift of the thin film transistor due to light irradiation with a wavelength of 420 nm. It is estimated that electrons hop from a level due to defects to a trap level near the conduction band. The band gap of In ₂ O ₃ is about 3.7 eV, and the above-mentioned electron hopping is achieved by enlarging the conduction band of this band gap (from the vacuum level to 4.05 eV) (closer to the vacuum level side). It can be expected that the energy required for the above can be increased, and as a result, the shift of the threshold voltage due to light irradiation can be suppressed.

Therefore, we studied the band gap of an In-SiO film difference added _SiO 2 becomes plus (+ 3.5 eV) to _In 2 _{O 3} and the conduction band of the _In 2 _{O 3.} FIG. 3 shows the evaluation results of the band gap by photoelectron yield spectroscopy of an In—Si—O film having a thickness of 50 nm with SiO ₂ weights of 1, 3 and 10% by weight, respectively. The band gap, which was about 3.7 eV when the SiO ₂ content was 1% by weight, could be increased to 4.5 eV by increasing the SiO ₂ content to 10% by weight.

Among the second oxides XO _x , candidate oxides that can have the effect of expanding the band gap like SiO ₂ are Ta ₂ O ₅ (+0.3 eV), ZrO ₂ (+1.4 eV), HfO. ₂ (+1.5 eV), Al ₂ O ₃ (+2.8 eV), Y ₂ O ₃ (+1.3 eV) and rare earth oxides. Therefore, among the elements X constituting the first oxide XO _x , the element X ¹ added for the purpose of suppressing the threshold voltage shift is silicon, tantalum, zirconium, hafnium, aluminum, yttrium, and rare earth elements. Selected from the group of Similarly, Si ₃ N ₄ (+2.4 eV) can also have an effect of widening the band gap, and Si ₃ N ₄ can be used as a semiconductor together with or in place of the second oxide. It is also preferable to add to the composite metal oxide constituting the layer.

The concentration of the oxide of the element X ¹ introduced into the In ₂ O ₃ film is usually 3% by weight or more and 50% by weight or less. Particularly, the concentration range of 10 to 30% by weight suppresses undesirable effects due to the addition. This is preferable from the viewpoint of expanding the gap.

As described above, in the first invention, the element X ¹ of the semiconductor layer is a semiconductor layer, a high density at the central portion, having a concentration gradient of a low density at both interfaces. That is, the at least one concentration of the element X ¹ represents a local maximum value, i.e. at least one peak at the center in the thickness direction of the semiconductor layer. Here, the meaning of the “central part” is as described above.

Present in a preferred embodiment of the first invention, the concentration of oxide of the element X ¹ is the maximum value in the central portion in the thickness direction of the semiconductor layer, for example, 3 wt% or more, 50 wt% or less, preferably 10 wt% As described above, it is preferably 30% by weight or less, and preferably has a concentration gradient that decreases monotonously as it approaches both interfaces. The concentration of the oxide of the element X ^{1 at} both interfaces is not particularly limited as long as it is substantially lower than the concentration at the center, and is preferably 0.1% by weight or less, for example, substantially zero. It is particularly preferred that

In the first invention, by the concentration of the element X ¹ in both interfaces is low, the contact resistance at the interface between the source electrode and / or drain electrode and the semiconductor layer is low and excellent in high gate controllability electron mobility That is, a practically preferable characteristic can be realized.
By concentration of the element X ¹ in the composite oxide constituting the semiconductor layer at the interface between the source electrode and / or drain electrode and the semiconductor layer is low, the composite oxide will have a tendency to release oxygen . As a result, the complex oxide in the vicinity of the interface with the source electrode and / or drain electrode generates oxygen vacancies and is so-called metalized, and the contact resistance with the source electrode and / or drain electrode is reduced.
Also, low concentration of the element X ¹ in the composite oxide constituting the semiconductor layer, by high concentration of the second oxide otherwise, electron mobility tends to increase. Effect more susceptible to the gate voltage, in the vicinity of the interface between the gate electrode side of the insulating layer, by the concentration of the element X ¹ of the semiconductor layer low (high electron mobility) higher current at the same gate voltage Can be controlled, that is, the effect of improving the gate controllability can be realized.

The thin film transistor of the second invention of the present application,
A source electrode and a drain electrode;
A semiconductor layer provided in contact with the source electrode and the drain electrode;
A gate electrode provided corresponding to a channel between the source electrode and the drain electrode;
A thin film transistor having an insulator layer provided between the gate electrode and the semiconductor layer,
The semiconductor layer has a second metal oxide that can generate electron carriers by introducing oxygen vacancies, and the second energy of oxygen is 200 kJ / mol or more higher than that of the first metal oxide. Formed of a composite metal oxide to which an oxide (XO _x ) is added,
Among the elements X constituting the second oxide, the concentration of at least one element X ² that does not correspond to any of silicon, tantalum, zirconium, hafnium, aluminum, yttrium, and rare earth elements is in the thickness direction of the semiconductor layer. The thin film transistor having a minimum value in the center.

Here, the concentration of the at least one element X ² continuously and substantially varies in the thickness direction of the semiconductor layer, that is, the at least one element X ² is in the thickness direction of the semiconductor layer. It has a concentration gradient. More specifically, the concentration of the at least one element X ² has a minimum value at the center in the thickness direction of the semiconductor layer. Here, the “central portion” refers to both the interfaces of the semiconductor layer (usually, the interface in contact with the interlayer insulating film on the source electrode and drain electrode side and the interface in contact with the insulator layer on the gate electrode side). It refers to a location 2 nm or more, or 5% or more of the thickness of the semiconductor layer.
Preferably, the at least one element X ² concentration shows a minimum value at the central portion in the thickness direction of the semiconductor layer. That is, the concentration of the element X ² in any location of the central portion in the thickness direction of the semiconductor layer is preferably lower than the concentration of the element X ² in any other portion of the semiconductor layer.

The at least one element X ² is an element constituting the second oxide, that is, an element constituting the second oxide (XO _x ) that is 200 kJ / mol or more larger than the oxygen separation energy of the first metal oxide. X is an element that does not correspond to any of silicon, tantalum, zirconium, hafnium, aluminum, yttrium, and rare earth elements.
Element X ² may be any element which corresponds to the above definition, but is not imposed specifically limited otherwise, preferably titanium (Ti). Further, tungsten (W) also can be used as the element X ^2.

In the present second invention, oxides of elements X ² in the semiconductor layer is a semiconductor layer, a low density at the central portion, having a concentration gradient of high concentration both interfaces. That is, the at least one element X ² concentration shows a minimum value at the central portion in the thickness direction of the semiconductor layer.

As in the preferred embodiment of the second aspect of the present invention, the concentration of the oxide of the element X ² is preferably to have a minimum value in the central portion in the thickness direction of the semiconductor layer approaches from there to both interfaces, Each preferably has a monotonically increasing concentration gradient. There is no particular limitation on the concentration of the oxide of the element X ² in both interfaces, from the viewpoint of for increasing the mobility is preferably 20 wt% or less 1 wt% or more. The concentration of the oxide of the element X ² in the central portion is not particularly limited as long as it is substantially lower than the concentration at both interfaces, and is preferably 0.1% by weight or less, for example, substantially zero. It is particularly preferred that

In the second invention of the present application, since the concentration of the element X ^{2 at} both interfaces is high, the contact resistance at the interface between the source electrode and / or the drain electrode and the semiconductor layer is low, the electron mobility is high, and the gate controllability. It is possible to realize a practically preferable characteristic of being excellent in resistance.
Due to the high concentration of element X ² (for example, titanium) in the composite oxide constituting the semiconductor layer at the interface between the source electrode and / or drain electrode and the semiconductor layer, the composite oxide tends to release oxygen. Will have. As a result, the complex oxide in the vicinity of the interface with the source electrode and / or drain electrode generates oxygen vacancies and is so-called metalized, and the contact resistance with the source electrode and / or drain electrode is reduced.
Further, since the concentration of the element X ² (for example, titanium) in the complex oxide constituting the semiconductor layer is high, the electron mobility tends to be improved. Effect more susceptible to the gate voltage, in the vicinity of the interface between the gate electrode side of the insulating film layer, by a high high electron mobility concentration of the element X ² of the semiconductor layer to control a higher current at the same gate voltage In other words, an effect that gate controllability is improved can be realized.

The layer structure and other structures of the thin film transistor of the second invention of the present application are the same as those of the first invention of the present application. The above description of the structure of the first invention of the present application also applies to the second invention of the present application as long as it does not contradict the purpose of the second invention of the present application.

Present a concentration distribution of elements X ¹ of the first invention, both are provided with a thin film transistor and a concentration distribution of elements X ² of the present second invention is a particularly preferred embodiment of the present first to third inventions. In this embodiment, the concentration of at least one element X ¹ selected from the group consisting of silicon, tantalum, zirconium, hafnium, aluminum, yttrium, and rare earth elements among the elements X constituting the second oxide is the semiconductor layer. And at least one element that does not correspond to any of silicon, tantalum, zirconium, hafnium, aluminum, yttrium, and rare earth elements among the elements X constituting the second oxide. the concentration of X ² indicates a minimum value at the central portion in the thickness direction of the semiconductor layer. In this embodiment, for example, the concentration of silicon that corresponds to the element X ¹ represents a maximum value in the central portion in the thickness direction of the semiconductor layer, and the concentration of titanium corresponding to the element X ² is the thickness direction of the semiconductor layer A minimum value may be shown at the center.

At this time, the silicon concentration at the central portion of the semiconductor layer exhibits a maximum value, thereby realizing a target effect of suppressing characteristic deterioration such as a shift in threshold current due to light irradiation, and both of the semiconductor layers. The high titanium concentration at the interface realizes the effect that the contact resistance at the interface between the source electrode and / or drain electrode and the semiconductor layer is low, the electron mobility is high, and the gate controllability is excellent. A thin film transistor having characteristics at a high level can be realized.

The thin film transistor of the third invention of the present application,
A source electrode and a drain electrode;
A semiconductor layer provided in contact with the source electrode and the drain electrode;
A gate electrode provided corresponding to a channel between the source electrode and the drain electrode;
A thin film transistor having an insulator layer provided between the gate electrode and the semiconductor layer,
The semiconductor layer has a second metal oxide that can generate electron carriers by introducing oxygen vacancies, and the second energy of oxygen is 200 kJ / mol or more higher than that of the first metal oxide. Formed of a complex metal oxide to which an oxide (XOx) is added,
In the thin film transistor, the semiconductor layer further contains nitrogen, and the concentration of nitrogen shows a maximum value in a central portion in the thickness direction of the semiconductor layer.
Also in the first and second inventions of the present application, it is preferable that the semiconductor layer further contains nitrogen, and the concentration of nitrogen exhibits a maximum value at the central portion in the thickness direction of the semiconductor layer.
By introducing nitrogen, particularly in the central portion of the semiconductor layer in the thickness direction, the valence band of the semiconductor layer changes, and the level caused by oxygen vacancies generated near the valence band can be suppressed. It is possible to suppress adverse effects such as threshold current shift due to irradiation. From this point of view, the nitrogen concentration is preferably low at the interface of the semiconductor layer and has a distribution showing a maximum value in the central portion in the thickness direction.

In addition, when a semiconductor layer contains Si etc., it is preferable that the said semiconductor layer contains nitrogen further, and the density | concentration of nitrogen has shown the maximum value in the center part of the thickness direction of the said semiconductor layer. In this case, the concentration of Si ₃ N ₄ (+2.4 eV) that can have the effect of expanding the band gap in addition to the above-described effect on the nitrogen concentration distribution has a maximum value in the central portion in the thickness direction of the semiconductor layer. Therefore, as in the first invention of the present application, a technical effect that characteristic deterioration such as shift of threshold current due to light irradiation is suppressed can be realized.

When the second oxide is a metal oxide, the addition of the second oxide to the semiconductor layers of the first to third inventions of the present application can be appropriately performed by employing a conventionally known method. The same applies to the case where the second oxide is an oxide of a nonmetallic element such as boron or carbon, but the specific example of the case where the first metal oxide is indium oxide (In ₂ O ₃ ) is described below. explain.
When the first metal oxide is indium oxide (In ₂ O ₃ ) and the second oxide is boron (B) oxide, the boron oxide is added to the indium oxide, for example, by ion implantation. In this addition method, the addition amount and depth can be controlled by changing the acceleration voltage. The content is more preferably greater than 0 and 10% by weight or less. In this case, ion implantation is performed by implanting boron ions instead of boron oxide into the first metal oxide. This boron ion becomes a boron oxide in the first metal oxide. As described above, when adding an oxide into the first metal oxide, it is not always necessary to add the oxide itself in the addition processing operation itself, for example, a process of adding an element other than oxygen constituting the oxide. The oxide can also be formed inside the first metal oxide. In the present application, regardless of the form of the addition treatment operation, the addition in the form of the oxide in the first metal oxide may be referred to as “adding the oxide”. Please be careful.

In addition, when the first metal oxide is indium oxide (In ₂ O ₃ ) and the second oxide is carbon (C) oxide, the addition of carbon oxide to indium oxide is, for example, In ₂ O _3. It can be carried out by a co-sputtering method using a target and a graphite target. By changing the ratio of each sputtering power, the amount of carbon oxide added can be controlled, and the content is more preferably greater than 0 and not more than 10% by weight.

As the second oxide having an oxygen separation energy of 200 kJ / mol or more higher than that of the first metal oxide, both the first metal oxide described first and the non-metal oxide described here were simultaneously used. It is also possible to form the semiconductor layer 50 with a composite metal oxide. In addition, in the second oxide addition process in the present embodiment, depending on the type of the process, the second metal oxide and the non-metal oxide of the second type are included in the semiconductor layer made of the composite metal oxide. Two oxides may inevitably coexist.
For example, when a thin film of such a semiconductor layer is manufactured by a solution method such as a sol-gel method, there is a high possibility that carbon remains in the thin film. It should be noted that such a case is also included in the first to third inventions of the present application.

(Thin Film Transistor Manufacturing Method)
Next, a method for manufacturing the thin film transistor 10 of this embodiment will be described. Although there is no restriction | limiting in particular in the method of forming the semiconductor layer of the thin-film transistor of this embodiment, It is also possible to form by using a physical vapor deposition method (or physical vapor deposition method).

Here, examples of physical vapor deposition include vapor deposition and sputtering. Examples of the vapor deposition method include vacuum vapor deposition, molecular beam vapor deposition (MBE), ion plating, and ion beam vapor deposition. Examples of the sputtering method include conventional sputtering, magnetron sputtering, ion beam sputtering, ECR (electron cyclotron resonance) sputtering, and reactive sputtering. When plasma is used in the sputtering method, a film forming method such as a reactive sputtering method, a DC (direct current) sputtering method, or a radio frequency (RF) sputtering method can be used.

Furthermore, those manufactured using the following manufacturing method are preferable. When the following manufacturing method is used, a higher quality thin film transistor can be manufactured.

In the method for manufacturing the thin film transistor 10 of the present embodiment, the gate electrode 30 and the insulator layer 40 are formed on the substrate 20 by a generally known method, and then the semiconductor layer 50 is formed. In the manufacturing method of the present embodiment, the semiconductor layer 50 includes the first metal oxide powder and the second oxide powder having an oxygen separation energy of 200 kJ / mol or more larger than the oxygen separation energy of the first metal oxide. Is produced by a physical vapor deposition method using a target that is a sintered body including a mixed gas of a rare gas and oxygen. Here, it demonstrates as using sputtering method as a physical vapor deposition method.

For example, when an In—Si—O-based metal oxide is employed as the semiconductor layer 50, a sintered body of indium oxide powder and silicon oxide powder may be employed as the target. Further, the target may be mixed with impurities such as an additive (metal oxide or the like) at a weight percent or less of silicon oxide. For example, metal oxides (such as zinc oxide) other than indium oxide and silicon oxide may be mixed into the target at a ratio (weight ratio) equal to or lower than the silicon oxide content in the entire target as unintended impurities. Absent.

In that case, the content of silicon oxide contained in the sintered body is preferably more than 0% by weight and 50% by weight or less. Moreover, it is more preferable that the content of silicon oxide is more than 0 wt% and not more than 5 wt%.

In In-Zn-O-based and In-Ga-Zn-O-based metal oxides, which are generally known oxide semiconductors, if indium oxide is the "host material" and zinc oxide or gallium oxide is the "guest material" In general, 20 to 30% of guest material (zinc oxide or gallium oxide) is mixed with the host material (indium oxide).

On the other hand, the semiconductor layer 50 of the thin film transistor 10 of the present embodiment is formed into a thin film using the sintered body as described above as a target. In the thin film transistor 10 manufactured by the manufacturing method of this embodiment, as described above, the silicon oxide content is more preferably more than 0 wt% and 5 wt% or less. Therefore, the semiconductor layer 50 in this preferable composition is used. The oxide semiconductor can have an extremely small content of the guest material (silicon oxide) with respect to the host material (indium oxide) as compared with a conventionally known oxide semiconductor.

In the method for manufacturing the thin film transistor 10, a mixed gas of a rare gas and oxygen may be used as a process gas. Examples of the rare gas include helium, neon, argon, krypton, and xenon. The process gas preferably does not contain a compound having a hydrogen atom.

In the method for manufacturing a thin film transistor of this embodiment, according to the inventors' investigation, when a semiconductor layer is formed using a target containing indium oxide and silicon oxide, the metal oxide constituting the semiconductor layer is changed to an amorphous film. It has been found that it does not require high temperatures to do. Therefore, in the method for manufacturing a thin film transistor, an amorphous semiconductor layer can be formed by performing a step of forming a semiconductor layer at 10 ° C. or higher and 200 ° C. or lower. Further, by performing the treatment at a temperature higher than 200 ° C. and lower than or equal to 400 ° C., a suitable crystallized semiconductor layer can be formed. Further, the step of forming the semiconductor layer may be performed at room temperature. Here, “implemented at room temperature” means that the semiconductor layer is not heated for the step of forming the semiconductor layer, and the temperature adjustment of the working environment is unnecessary.

As the sputtering method employed in the method for manufacturing the thin film transistor of the present embodiment, known methods such as RF sputtering and DC sputtering can be used.

When an In—Si—O-based metal oxide is used as the semiconductor layer 50, the target may be indium oxide powder and silicon oxide powder, and a mixture of these powders may be sintered. A sintered body of each powder may be sufficient. The latter is preferable from the viewpoint of controllability of the concentration distribution of silicon oxide as the second oxide. In this case, the semiconductor layer can be formed by co-sputtering using a plurality of sintered bodies.

The concentration distribution of elements X ¹ in the first invention, the concentration distribution of elements X ² in the present second invention also, it is possible to preferably control by co sputtering. For example, when the element X ¹ is silicon and the element X ² is Si, the concentration distribution of Si and Ti in the In—Si—Ti—O semiconductor layer is expressed by the In—Si—O target and the In—Ti—O target. And both targets are installed in the same chamber, and the sputtering power for each target is preferably adjusted by preferably changing continuously.

The same method as described above should be used even when a metal oxide combining zinc oxide and tin oxide or indium oxide, gallium oxide, zinc oxide and tin oxide is used as the first metal oxide instead of indium oxide. Thus, a semiconductor layer in which the amount of oxygen vacancies is controlled and the concentration gradient of the second oxide is controlled can be formed.

The case where the second oxide is silicon oxide has been described, but instead, zirconium oxide (Zr—O), praseodymium oxide (Pr—O), lanthanum oxide (La—O), tantalum oxide (Ta—O), Even when any one of hafnium oxide (Hf—O) is used, the semiconductor layer can be formed in a process range corresponding to the magnitude of the separation energy of oxygen.

According to the thin film transistor of the embodiment as illustrated in FIG. 1 as described above, the effects of the first to third inventions of the present application are appropriately achieved by using the semiconductor layer in which the concentration distribution of the specific oxide is appropriately controlled. It is possible to realize a gate that suppresses deterioration of characteristics such as threshold current shift due to light irradiation, has low contact resistance at the interface between the source electrode and / or drain electrode and the semiconductor layer, and has high electron mobility. There is provided a thin film transistor having a practically preferable characteristic of excellent controllability at a high level.

Further, according to the method for manufacturing a thin film transistor as described above, it is possible to easily and efficiently manufacture a thin film transistor in which the effects of the first to third inventions of the present application are appropriately realized.

Although the so-called bottom gate type thin film transistor has been described in this embodiment, the first to third inventions of the present application can also be applied to a so-called top gate type thin film transistor. Details of the structure and manufacturing method of a so-called top gate type thin film transistor are well known in the art as described in, for example, Japanese Patent Application Laid-Open No. 2013-219936, and based on these, those skilled in the art can apply the present application without undue trial and error. The first to third inventions can be implemented in a top gate type embodiment.

In this embodiment, a so-called top contact type thin film transistor has been described. However, the first to third inventions of the present application can also be applied to a so-called bottom contact type thin film transistor. Details of the structure and manufacturing method of so-called bottom contact type thin film transistors are also well known in the art, and those skilled in the art can implement the first to third aspects of the present invention in a bottom contact type mode without undue trial and error. Is possible.

The preferred embodiments according to the first to third inventions of the present application have been described above with reference to the accompanying drawings. Needless to say, the first to third inventions of the present application are not limited to such examples. The various shapes and combinations of the constituent members shown in the above-described examples are merely examples, and various modifications can be made based on design requirements and the like without departing from the spirit of the first to third inventions of the present application.

Next, a thin film transistor and a method for manufacturing the thin film transistor according to the fourth embodiment of the present invention will be described below with reference to the drawings. In all the drawings below, the dimensions and ratios of the constituent elements are appropriately changed in order to make the drawings easy to see.

In the fourth invention of the present application, when tin oxide having a large oxygen separation energy of 528 kJ / mol is used as an oxide for generating an electron carrier, the oxygen separation energy of the metal oxide to be added is the oxygen separation energy of the tin oxide. Based on the new knowledge of the present inventors that the amount of oxygen deficiency in the above problem can be controlled by making the difference from the energy of separation of oxygen with respect to tin oxide less than 200 kJ / mol. The thin film transistor of the first embodiment and the manufacturing method thereof are provided.

In addition to the above metal oxides, the present inventors further add an additional oxide whose oxygen separation energy is smaller than that of tin oxide, and the addition amount is less than the addition amount of the above metal oxide. The present inventors have found that the amount of oxygen vacancies can be controlled and the amorphous stable formation temperature range can be expanded. The fourth invention of the present application also provides a thin film transistor and a manufacturing method thereof according to the second embodiment based on this finding.

[Structure of thin film transistor]
The thin film transistor of the first embodiment is provided corresponding to a source electrode and a drain electrode, a semiconductor layer provided in contact with the source electrode and the drain electrode, and a channel between the source electrode and the drain electrode. A gate electrode, and an insulator layer provided between the gate electrode and the semiconductor layer, wherein the semiconductor layer is tin oxide, and the oxygen separation energy of the tin oxide is greater than the oxygen separation energy of the tin oxide, This is a composite metal oxide to which a metal oxide having a difference in oxygen separation energy of tin oxide of less than 200 kJ / mol is added.

Further, in the thin film transistor of the second embodiment, the semiconductor layer of the thin film transistor of the first embodiment further includes an additional oxidation in which the oxygen separation energy is smaller than that of tin oxide and the addition amount is smaller than that of the above metal oxide. It is a composite metal oxide to which a product is added.

In addition, the method for manufacturing a thin film transistor of this embodiment includes a step of forming the semiconductor layer at 10 ° C. or higher and 500 ° C. or lower when manufacturing the thin film transistor.

FIG. 8 is a schematic cross-sectional view of the thin film transistor 201 according to the first embodiment. As the substrate 202, a substrate formed using a known forming material can be used, and any of those having light transmittance and those having no light transmittance can be used. For example, an inorganic substrate made of alkali silicate glass, quartz glass, silicon nitride, or the like; a silicon substrate; a metal substrate whose surface is insulated; acrylic resin, polycarbonate resin, PET (polyethylene terephthalate), or PBT (polybutylene) Various substrates such as a resin substrate made of a polyester resin such as terephthalate) or a paper substrate can be used. Further, the substrate may be a composite material formed by combining a plurality of these materials. The thickness of the substrate 202 can be appropriately set according to the design.

The thin film transistor 201 is a so-called bottom gate type transistor. The thin film transistor 201 includes a gate electrode 203 provided over a substrate 202, an insulator layer 204 provided to cover the gate electrode 203, a semiconductor layer 205 provided on the top surface of the insulator layer 204, A source electrode 208 and a drain electrode 209 are provided in contact with the semiconductor layer 205 on the upper surface. The gate electrode 203 is provided so as to correspond to the channel region of the semiconductor layer 205 (at a position overlapping the channel region in plan view). The semiconductor layer 205 is composed of a composite metal oxide obtained by adding a metal oxide 207 to tin oxide 206. As a matter of course, the semiconductor layer may contain components other than the metal oxide 207 and inevitable impurities as long as the adverse effects of the fourth invention of the present application are not adversely affected. The same applies to the case of adding an oxide of a non-metallic element described in other embodiments described below. Further, in FIG. 8, for convenience of illustration, the semiconductor layer 205 (composite metal oxide) can be seen as if particles of the metal oxide 207 are scattered in the tin oxide 206. Although drawn, it should be noted that the metal oxide is actually uniformly added to the tin oxide, that is, doped, so that the composite metal oxide becomes a uniform material.

As the gate electrode 203, the source electrode 208, and the drain electrode 209, those formed of a generally known material can be used. Examples of the material for forming these electrodes include aluminum (Al), gold (Au), silver (Ag), copper (Cu), nickel (Ni), molybdenum (Mo), tantalum (Ta), and tungsten (W). Examples thereof include metal materials such as these, alloys thereof, and conductive oxides such as indium tin oxide (ITO) and zinc oxide (ZnO). Moreover, these electrodes may form the laminated structure of two or more layers, for example by plating the surface with a metal material.

The gate electrode 203, the source electrode 208, and the drain electrode 209 may be formed of the same forming material, or may be formed of different forming materials. The source electrode 208 and the drain electrode 209 are preferably made of the same material since manufacturing is easy.

The insulator layer 204 has an insulating property, and can be formed using either an inorganic material or an organic material as long as the gate electrode 203 can be electrically insulated from the source electrode 208 and the drain electrode 209. It may be formed. Examples of the inorganic material include normally known insulating oxides such as SiO ₂ , SiN _x , SiON, Al ₂ O ₃ , and HfO ₂ , nitrides, and oxynitrides. Examples of the organic material include acrylic resin, epoxy resin, silicon resin, and fluorine resin. The organic material is preferably a photocurable resin material because it is easy to manufacture and process.

The semiconductor layer 205 is obtained by adding, to tin oxide, a metal oxide in which the dissociation energy of oxygen is larger than the separation energy of oxygen in tin oxide and the difference in separation energy between the two is smaller than 200 kJ / mol.

In the fourth invention of the present application, tin oxide (SnO ₂ ) is used as the first metal oxide in the above-mentioned prior application of the present inventors. However, since the separation energy of oxygen of tin oxide is as small as 528 kJ / mol, oxygen from tin oxide is reduced. Easily desorbs and easily generates oxygen deficiency. However, if the amount of oxygen vacancies becomes too large, it changes from semiconducting properties to metallic properties, making it unsuitable as a semiconductor layer. As a result of repeated studies to solve this problem, the inventors of the present application added a metal oxide having an oxygen separation energy larger than that of tin oxide in order to control the oxygen deficiency of tin oxide. I found out that I should do it. Specific examples of the metal oxide that can be added include samarium oxide having an oxygen separation energy of 573 kJ / mol, tungsten oxide of 720 kJ / mol, neodymium oxide of 703 kJ / mol, and gadolinium oxide of 715 KJ / mol.

Also, the content of the metal oxide added to make tin oxide a semiconductor layer having an appropriate oxygen deficiency is preferably in the range of greater than 0 to 50% by weight. In particular, when the content of the metal oxide added to the tin oxide is in the range of more than 0 to 5% by weight or less, the semiconductor layer can be manufactured at a low temperature of 300 ° C. or less.

In-Zn-O-based and In-Ga-Zn-O-based metal oxides tend to be polycrystalline when a semiconductor layer is formed. Therefore, in a generally known thin film transistor, the surface of the semiconductor layer does not become flat due to crystal grains contained in the semiconductor layer. In addition, the normally known semiconductor layer of an oxide film transistor has a reduced electrical conductivity in the plane direction due to such crystal grains. Therefore, in order to obtain planarization of the surface of the semiconductor layer and high electrical conductivity, the semiconductor layer preferably has an amorphous structure.

The thickness of the semiconductor layer 205 is more preferably in the range of 5 nm to 20 nm. In the present embodiment, the thickness of the semiconductor layer 205 was measured using a crystal oscillation type film thickness meter disposed mainly for film thickness calibration in the sputtering chamber in which the semiconductor layer 205 was formed.

In the second embodiment of the fourth invention of the present application, the composite metal oxide constituting the semiconductor layer 205 is obtained by adding the above-described metal oxide to tin oxide, and further having an oxygen separation energy smaller than that of tin oxide. In addition, an additional oxide having an addition amount smaller than that of the metal oxide is added. The inventors of the present application have found that the semiconductor layer becomes amorphous even in a high temperature range of 500 ° C. by controlling the amount of oxygen vacancies by adding a metal oxide and adding an additional oxide. As the additional oxide, specifically, lead oxide having an oxygen release energy of 382.4 ± 3.3 kJ / mol, palladium oxide having 238.1 ± 12.6 kJ / mol, 418.6 ± 11.6 kJ / mol mol platinum oxide, 517.90 ± 0.05 kJ / mol sulfur oxide, 434 ± 42 kJ / mol antimony oxide, 426.3 ± 6.3 kJ / mol strontium oxide, 213 ± 84 kJ / mol thallium oxide, 387 7 ± 10 kJ / mol ytterbium oxide and the like.

The thin film transistor 201 ′ of the second embodiment of the present invention shown in FIG. 9 has basically the same structure as the thin film transistor 201 of FIG. 8, but the semiconductor layer 205 ′ corresponding to the semiconductor layer 205 of FIG. It is a composite metal oxide in which the metal oxide 207 is added to the tin 206, and an additional oxide 210 in which the oxygen separation energy is smaller than that of the tin oxide and the addition amount is smaller than that of the metal oxide. . 9 that have the same reference numerals as the elements in FIG. 8 are the same as the corresponding elements in FIG. 8, and therefore, the description thereof is omitted.

As noted in the description of the first embodiment with reference to FIG. 8, the semiconductor layer 205 ′ (composite metal oxide) is made of tin oxide 206 for convenience of illustration also in FIG. 9. It is drawn in a form that can be seen as interspersed with additional oxides 210, but here again, these oxides are actually uniformly added or doped in the tin oxide. Therefore, it should be noted that the composite metal oxide is a uniform material.

The addition of the metal oxide tungsten oxide (WO ₃ ) and the additional oxide ytterbium oxide (Yb ₂ O ₃ ) to the tin oxide (SnO ₂ ) is performed, for example, at the target preparation stage of the sputtering method.

In addition, the addition amount can be controlled by changing the ratio of sputtering power by co-sputtering method using Sn—W—O target and Yb ₂ O ₃ target, and the content is larger than 0 and 10% by weight. The following is more preferable.

[Thin Film Transistor Manufacturing Method]
Next, a method for manufacturing the thin film transistor 201 according to the first embodiment will be described. The semiconductor layer of the thin film transistor of this embodiment can also be formed by using physical vapor deposition (or physical vapor deposition).

Here, examples of physical vapor deposition include vapor deposition and sputtering. Examples of the vapor deposition method include vacuum vapor deposition, molecular beam vapor deposition (MBE), ion plating, and ion beam vapor deposition. Examples of the sputtering method include conventional sputtering, magnetron sputtering, ion beam sputtering, ECR (electron cyclotron resonance) sputtering, and reactive sputtering. When plasma is used in the sputtering method, a film forming method such as a reactive sputtering method, a DC (direct current) sputtering method, or a radio frequency (RF) sputtering method can be used.

Furthermore, what was manufactured using the following manufacturing method is preferable. When the following manufacturing method is used, a higher quality thin film transistor can be manufactured.

In the method for manufacturing the thin film transistor 201 of this embodiment, the gate electrode 203 and the insulator layer 204 are formed on the substrate 202 by a generally known method, and then the semiconductor layer 205 is formed. In the manufacturing method according to the present embodiment, the semiconductor layer 205 includes a tin oxide powder and a metal oxide having an oxygen separation energy larger than that of the tin oxide, and the oxygen of the tin oxide and the metal oxide. It is manufactured by a physical vapor deposition method using a target which is a sintered body containing a powder having a difference in separation energy of less than 200 kJ / mol and a mixed gas of a rare gas and oxygen. Here, it demonstrates as using sputtering method as a physical vapor deposition method.

For example, in the case where an Sn—W—O-based metal oxide is employed as the semiconductor layer 205, a sintered body of a tin oxide powder and a tungsten oxide powder may be employed as the target. Further, the target may be mixed with impurities such as an additive (metal oxide or the like) at a mass% or less of tungsten oxide. For example, a metal oxide (such as zinc oxide) other than tin oxide and tungsten oxide may be mixed into the target at a ratio (weight ratio) equal to or lower than the tungsten oxide content in the target as an unintended impurity. .

In that case, the content of tungsten oxide contained in the sintered body is preferably more than 0 mass% and 50 mass% or less. Further, the content of tungsten oxide is more preferably 0% by mass to 5% by mass.

In In-Zn-O-based and In-Ga-Zn-O-based metal oxides, which are generally known oxide semiconductors, if indium oxide is the "host material" and zinc oxide or gallium oxide is the "guest material" The guest material (zinc oxide or gallium oxide) is mixed with 20-30% of the host material (indium oxide).

On the other hand, the semiconductor layer 205 of the thin film transistor 201 of the present embodiment is formed into a thin film using the sintered body as described above as a target. In the thin film transistor 201 manufactured by the manufacturing method of this embodiment, as described above, the content of tungsten oxide is more preferably 0% by mass to 5% by mass, and thus the semiconductor layer 205 in the case of this preferable composition. This oxide semiconductor has an extremely small content of the guest material (tungsten oxide) with respect to the host material (tin oxide) as compared with a conventionally known oxide semiconductor.

In the method for manufacturing the thin film transistor 201, a mixed gas of a rare gas and oxygen is used as a process gas. Examples of the rare gas include helium, neon, argon, krypton, and xenon. Further, the process gas does not include a compound having a hydrogen atom.

In the thin film transistor manufacturing method of this embodiment, when the semiconductor layer is formed using a target containing tin oxide and tungsten oxide, the metal oxide constituting the semiconductor layer is changed to an amorphous film. It has been found that it does not require high temperatures to do. Therefore, in a method for manufacturing a thin film transistor, an amorphous semiconductor layer can be formed by performing a step of forming a semiconductor layer at 10 ° C. to 300 ° C. In addition, a suitable crystallized semiconductor layer can be formed by performing the process at a temperature higher than 300 ° C. and lower than or equal to 500 ° C. Further, the step of forming the semiconductor layer is preferably performed at room temperature. Here, “implemented at room temperature” means that the semiconductor layer is not heated for the step of forming the semiconductor layer, and the temperature adjustment of the working environment is unnecessary.

As the sputtering method employed in the method for manufacturing the thin film transistor of the present embodiment, known methods such as RF sputtering and DC sputtering can be used.

Further, the target may be a sintered body of a mixture of these powders or a sintered body of each powder as long as tin oxide powder and tungsten oxide powder are used. When a sintered body is formed for each metal oxide powder, the semiconductor layer can be formed by co-sputtering using a plurality of sintered bodies.

Although silicon oxide has been described as the metal oxide, samarium oxide (Sm—O), tungsten oxide (W—O), neodymium oxide (Nd—O), and gadolinium oxide (Gd—O) were used instead. Even in this case, the semiconductor layer can be formed in a process range corresponding to the magnitude of the separation energy of oxygen.

In the method for manufacturing the thin film transistor 201 of the second embodiment, the semiconductor layer 205 is formed after the gate electrode 203 and the insulator layer 204 are formed on the substrate 202 by a generally known method. In the manufacturing method according to the present embodiment, the semiconductor layer 205 has a difference of 200 kJ between the tin oxide powder and the oxygen separation energy of the tin oxide, and the oxygen separation energy of the tin oxide is 200 kJ. A metal oxide powder having an oxygen separation energy of less than / mol, and an additional oxide in an amount where the oxygen separation energy is less than the oxygen separation energy for tin oxide and less than the addition amount of the metal oxide Is produced by a physical vapor deposition method using a target that is a sintered body containing a noble gas and a mixed gas of oxygen and oxygen. Here, it demonstrates as using sputtering method as a physical vapor deposition method.

For example, in the case where a Sn—W—Yb—O-based metal oxide is used as the semiconductor layer 205, a target may be a sintered body of a tin oxide powder, a tungsten oxide powder, and a ytterbium oxide powder. Further, the amount of ytterbium oxide added to the target is always smaller than the amount of tungsten oxide added.

In that case, when the content of tungsten oxide contained in the sintered body is more than 0% by mass and 50% by mass or less, the content of ytterbium oxide is more than 0% by mass and less than 20% by mass. The content of ytterbium oxide is more preferably 0% by mass to 4% by mass.

In the method for manufacturing the thin film transistor 201, a mixed gas of a rare gas and oxygen is used as a process gas. Examples of the rare gas include helium, neon, argon, krypton, and xenon. Further, the process gas does not include a compound having a hydrogen atom.

In the method for manufacturing a thin film transistor of this embodiment, when the semiconductor layer is formed using a target containing tin oxide, tungsten oxide, and ytterbium oxide, the process of forming the semiconductor layer is 10 ° C. or higher, as studied by the inventors. It was found that an amorphous semiconductor layer can be formed by carrying out at 500 ° C. or lower. Further, the step of forming the semiconductor layer is preferably performed at room temperature. Here, “implemented at room temperature” means that the semiconductor layer is not heated for the step of forming the semiconductor layer, and the temperature adjustment of the working environment is unnecessary.

As the sputtering method employed in the method for manufacturing the thin film transistor of the present embodiment, known methods such as RF sputtering and DC sputtering can be used.

The method for manufacturing the thin film transistor of the fourth invention of the present application has been described above.

According to the thin film transistor of the fourth invention of this application as illustrated in FIGS. 8 and 9 as described above, the characteristic change is suppressed by using the novel composite metal oxide for the semiconductor layer.

Further, according to the semiconductor device having the above configuration, it has a thin film transistor in which the characteristic change is suppressed, and has high reliability.

Further, according to the method for manufacturing a thin film transistor as described above, a thin film transistor in which a change in characteristics is suppressed can be easily manufactured by using a novel composite metal oxide for a semiconductor layer.

Although the so-called bottom gate type thin film transistor has been described in the present embodiment, the fourth invention of the present application can also be applied to a so-called top gate type thin film transistor.

In the present embodiment, a so-called top contact type thin film transistor has been described. However, the fourth invention of the present application can also be applied to a so-called bottom contact type thin film transistor.

As described above, the preferred embodiment according to the fourth invention of the present application has been described with reference to the accompanying drawings, but it is needless to say that the fourth invention of the present application is not limited to such an example. Various shapes, combinations, and the like of the constituent members shown in the above-described examples are merely examples, and various modifications can be made based on design requirements and the like without departing from the gist of the fourth invention of the present application.

Further, a thin film transistor using the oxide semiconductor of the fifth invention of the present application and a method for manufacturing the thin film transistor will be described below with reference to the drawings. In all the drawings below, the dimensions and ratios of the constituent elements are appropriately changed in order to make the drawings easy to see. Therefore, the actual dimensions and ratios of the constituent elements are not limited to the drawings in which they are disclosed.
The thin film transistor using an oxide semiconductor according to the fifth invention of the present application corresponds to a source electrode and a drain electrode, a semiconductor layer provided in contact with the source electrode and the drain electrode, and a channel between the source electrode and the drain electrode. A metal oxide capable of generating electron carriers by introducing oxygen vacancies, and an insulating layer provided between the gate electrode and the semiconductor layer. An oxidation in which oxygen vacancies are introduced, comprising: a first metal oxide made of a material; and a second oxide having an oxygen separation energy greater than that of the first metal oxide by 200 kJ / mol or more. An OH group, an H group, an F group, a Cl group, wherein the metal of the first metal oxide is introduced into the oxygen deficient portion, It is formed in the oxide semiconductor which is bound to at least one group selected from the group consisting of radicals, a thin film transistor.

The method for manufacturing a thin film transistor using an oxide semiconductor according to the fifth aspect of the present invention includes a step of forming the semiconductor layer at 10 ° C. or higher and 400 ° C. or lower when manufacturing the thin film transistor. You may have the process of forming the said semiconductor layer at 10 degreeC or more and 200 degrees C or less.

FIG. 15 is a schematic cross-sectional view showing an embodiment of a thin film transistor using an oxide semiconductor according to the fifth invention.
A thin film transistor 310 in FIG. 15 is a so-called bottom-gate transistor. As shown in FIG. 15, the thin film transistor 310 includes a gate electrode 330 provided on a substrate 320, an insulator layer (gate insulator layer) 340 provided so as to cover the gate electrode 330, and an insulator layer. The semiconductor layer 350 provided on the upper surface of 340, the source electrode 360 and the drain electrode 370 provided in contact with the semiconductor layer 350 on the upper surface of the semiconductor layer 350, and the whole (specifically, the source electrode 360 and the drain electrode 370) , And a region of the semiconductor layer 350 which does not overlap with the source electrode 360 and the drain electrode 370) is covered with an interlayer insulating film 380.

<Board 320>
As the substrate 320, a substrate formed of a known forming material can be used, and any of those having light transmittance and those having no light transmittance may be used.
As a material for forming the substrate 320, for example, an inorganic substrate made of alkali silicate glass, quartz glass, silicon nitride, or the like; a silicon substrate; a metal substrate with an insulating surface; acrylic resin, polycarbonate resin, PET ( Various substrates such as a resin substrate made of a polyester resin such as polyethylene terephthalate) or PBT (polybutylene terephthalate); a paper substrate can be used. Further, the substrate may be a composite material formed by combining a plurality of these materials.
Further, the thickness of the substrate 320 can be appropriately set according to the design.

<Gate electrode 330>
The gate electrode 330 is provided so as to correspond to the channel region of the semiconductor layer 350 (at a position overlapping the channel region in plan view). That is, the channel region of the semiconductor layer 350 is in a region corresponding to the position of the gate electrode 330. Note that the semiconductor layer of the thin film transistor mainly functions as a channel on the gate electrode side. For example, MoW is used as the gate electrode 330.

<Semiconductor layer 350>
The semiconductor layer 350 is formed of the oxide semiconductor of the fifth invention of the present application. Specifically, the semiconductor layer 350 includes a first metal oxide made of a metal oxide capable of generating electron carriers by introducing oxygen vacancies, and an oxygen separation energy of the first metal oxide. An oxide semiconductor having an oxygen deficient portion, which is formed from a second oxide greater than the energy by 200 kJ / mol or more, and the oxygen deficient portion further includes an OH group, an H group, an F group, a Cl group, Alternatively, it is formed by the oxide semiconductor in which the first metal oxide and the substituent are bonded by being substituted by at least one selected from the group consisting of B groups. However, as long as the effects of the fifth invention of the present application can be achieved, the semiconductor layer 350 may contain components other than these and unavoidable impurities.

Here, the first metal oxide is a substance having a semiconductor property capable of generating electron carriers by introducing oxygen vacancies. The first metal oxide is preferably a metal oxide containing at least one selected from the group consisting of indium, gallium, zinc, and tin, and the second oxide is preferably zirconium (Zr). , Silicon (Si), titanium (Ti), tungsten (W), tantalum (Ta), hafnium (Hf), scandium (Sc), yttrium (Y), lanthanum (La), praseodymium (Pr), neodymium (Nd) , Gadolinium (Gd), other rare earth elements, aluminum (Al), and carbon (C). The oxide includes at least one selected from the group consisting of carbon (C).
Preferably, when the element of the first oxide is In, the element of the second oxide is at least one selected from the group consisting of Zr, Pr, Si, Ti, W, Ta, La, Hf, and C. When the element of the first oxide is Sn, the element of the second oxide is at least one element selected from the group consisting of Sc, Ti, W, Nd, and Gd.

As a preferable element of the first oxide, a metal oxide containing at least one of indium, zinc, and tin may be used. In particular, indium that easily introduces oxygen vacancies at a low temperature may be used. Is more preferable.
As the second oxide, silicon (Si), titanium (Ti), tungsten (W), tantalum (Ta), lanthanum (La), hafnium (Hf), zirconium (Zr), and praseodymium (Pr) are used. It is also possible to use an oxide containing at least one selected from the group consisting of silicon (Si), titanium (Ti), tungsten (W), tantalum (Ta), lanthanum (La), and hafnium. It is an oxide containing at least one selected from the group consisting of (Hf). As the second oxide, an oxide containing carbon (C) can also be used.
The content of the second oxide may be greater than 0 and 50% by weight or less, greater than 0 and 10% by weight or less, and greater than 0 and 5% by weight or less.
In the oxide semiconductor forming the semiconductor layer 350, the substituent introduced into the oxygen deficient portion is specifically selected from the group consisting of an OH group, an H group, an F group, a Cl group, or a B group. At least one is mentioned. In particular, an OH group and an H group are preferable, and an OH group is more preferable.
At that time, when OH groups are introduced, the content is preferably 0.1% or more and 10% or less, and when H groups are introduced, the content is preferably greater than 0% and 0.1% or less, F When the group, Cl group, or B group is introduced, the content is preferably more than 5 × 10 ¹⁸ atoms / cm ^{3 and not} more than 1 × 10 ²¹ atoms / cm ³ . These contents are determined using the peak area ratio of the XPS spectrum.
The OH group content (%) is calculated by the formula [OH] / ([OH] + [O]) × 100, and the H group content (%) is [H] / ([H] + [ O]) × 100. Here, [OH], [H], and [O] represent atomic ratios of OH, H, and O in the oxide semiconductor, respectively.

When indium oxide (In ₂ O ₃ ) is used as the first metal oxide, the oxygen separation energy of indium oxide is as small as 346 ± 30 kJ / mol, so oxygen is easily desorbed from indium oxide to generate oxygen vacancies. Easy to do. However, if the amount of oxygen vacancies becomes too large, it changes from semiconducting properties to metallic properties and becomes unsuitable as a semiconductor layer. As a result of repeated studies to solve this problem, the inventors of the present application added a second oxide having an oxygen separation energy larger than that of indium oxide in order to control the oxygen deficiency amount of indium oxide. I found out that I should do.
Specifically, when an oxide having an oxygen separation energy of 725 kJ / mol or more, more preferably 780 kJ / mol or more is used as the second oxide, the amount of oxygen deficiency of indium oxide can be easily controlled.

Further, when a material other than indium oxide is generalized as the first metal oxide, the oxygen separation energy of the second oxide is 200 kJ / mol or more, more preferably 255 kJ / mol compared to the first metal oxide. What is larger than mol may be used.
Therefore, the oxygen separation energy of the second oxide may be 255 kJ / mol or more larger than the oxygen separation energy of the first metal oxide.

As shown in Table C1 that summarizes metal oxides having an oxygen separation energy of 780 kJ / mol or more and Table C2 that summarizes oxides having an oxygen separation energy of 725 kJ / mol or more and 780 kJ / mol or less. Among the usable second oxides, the second oxide includes zirconium oxide (Zr—O), praseodymium oxide (Pr—O), lanthanum oxide (La—O), and silicon oxide (Si—O). Tantalum oxide (Ta—O), and hafnium oxide (Hf—O).

Among the second oxides added to make the first metal oxide a semiconductor layer 350 having a suitable oxygen deficiency in this embodiment, the second oxide is particularly 780 kJ / mol or more shown in Table C1. The second oxide is more preferable. Specifically, lanthanum oxide (La—O), silicon oxide (Si—O), tantalum oxide (Ta—O), and hafnium oxide (Hf—O) can be given.
Although not listed in the table, the oxygen separation energy of titanium oxide (Ti—O) is 666.5 ± 5.6 kJ / mol, and the oxygen separation energy of tungsten oxide (W—O) is 720 ± 71 kJ / mol.

Further, the content of the second oxide added to the first metal oxide in order to make the first metal oxide a semiconductor layer 350 having a suitable oxygen deficiency ranges from 0 to 50% by weight. preferable. In particular, it is preferable that the content of the second oxide added to the first metal oxide is in the range of more than 0 and 5% by weight or less in terms of production at a low temperature of 200 ° C. or less.

In addition, the semiconductor layer 350 (that is, the oxide semiconductor forming the semiconductor layer 350) is preferably amorphous.
In-Zn-O-based and In-Ga-Zn-O-based metal oxides tend to be polycrystalline when a semiconductor layer is formed. Therefore, in a generally known thin film transistor, the surface of the semiconductor layer does not become flat due to crystal grains contained in the semiconductor layer. In addition, the normally known semiconductor layer of an oxide film transistor has a reduced electrical conductivity in the plane direction due to such crystal grains.
Therefore, in order to obtain planarization of the surface of the semiconductor layer and high electrical conductivity, the semiconductor layer 350 preferably has an amorphous structure.

The thickness of the semiconductor layer 350 (that is, the thickness of the oxide semiconductor forming the semiconductor layer 350) is preferably in the range of 5 nm to 20 nm.
In the present embodiment, the thickness was measured using a crystal oscillation type film thickness meter disposed mainly for the purpose of film thickness calibration in the sputtering chamber in which the semiconductor layer 350 was formed.

Further, the second oxide may include an oxide of carbon (C).
Specifically, an element that forms an oxide having a larger separation energy than the first metal oxide may be added. Specifically, the oxide semiconductor into which oxygen vacancies are introduced may be one in which an oxide of carbon (C) is added to the first metal oxide. This is because the oxygen desorption energy of the C—O bond is as large as 1076.38 ± 0.67 kJ / mol, so that the amount of oxygen deficiency introduced into the first metal oxide can be easily controlled.

When the oxide is added to the first metal oxide, it is not always necessary to add the oxide itself in the addition treatment operation itself. For example, a treatment for adding an element other than oxygen constituting the oxide is performed. An oxide can also be formed inside one metal oxide. Therefore, in the present application, regardless of the form of the addition treatment operation, the addition in the form of the oxide in the first metal oxide is referred to as “adding the oxide”. Please be careful.

In addition, the addition of carbon (C) to the first metal oxide indium oxide (In ₂ O ₃ ) is to change the ratio of the sputtering power by a co-sputtering method using an In ₂ O ₃ target and a graphite target. The amount added can be controlled by the control, and the content is more preferably greater than 0 and 10% by weight or less.
Therefore, the content of carbon (C) contained as the second oxide is preferably greater than 0 and 10% by weight or less.

The states of the first metal oxide and the second oxide in the semiconductor layer 350 are uniform (that is, uniform by adding or doping the second oxide into the first metal oxide uniformly). It is a substance).

Note that, for example, in the case of using a carbon (C) oxide as the second oxide having a large oxygen separation energy, another oxide is used to form an oxide semiconductor in which oxygen deficiency is introduced. It is also possible. In addition, when the second oxide having a large oxygen separation energy is added in the fifth invention of the present application, both types of oxides inevitably coexist in the oxide semiconductor into which oxygen deficiency is introduced depending on the type of the treatment. It can happen.
For example, when such a thin film of an oxide semiconductor is manufactured by a solution method such as a sol-gel method, there is a high possibility that carbon remains in the thin film. It should be noted that such a case is also included in the fifth invention of the present application.

In the semiconductor layer 350, the source electrode 360, the drain electrode 370, and a region that does not overlap with the source electrode 360 and the drain electrode 370 and corresponds to the position of the gate electrode 330 corresponds to a channel region. In the region overlapping with the source electrode 360 and the drain electrode 370, the contact resistance is lowered by metallization.
As shown in FIG. 15, the gate electrode 330 is provided so as to correspond to the channel region of the semiconductor layer 350 (at a position overlapping the channel region in a plan view).

<Gate electrode 330, source electrode 360, drain electrode 370>
As the gate electrode 330, the source electrode 360, and the drain electrode 370, those formed of a generally known material can be used. Examples of materials for forming these electrodes include aluminum (Al), gold (Au), silver (Ag), copper (Cu), nickel (Ni), molybdenum (Mo), tantalum (Ta), and tungsten (W). Examples thereof include metal materials such as these, alloys thereof, and conductive oxides such as indium tin oxide (ITO) and zinc oxide (ZnO). Moreover, these electrodes may form a laminated structure of two or more layers (for example, Ti / Al / Ti) by, for example, plating the surface with a metal material.

The gate electrode 330, the source electrode 360, and the drain electrode 370 may be formed of the same forming material, or may be formed of different forming materials. Since manufacture becomes easy, it is preferable that the source electrode 360 and the drain electrode 370 are the same formation material.

<Insulator layer (gate insulator layer) 340>
The insulator layer (gate insulator layer) 340 is an insulating material and an organic material as long as it has insulating properties and can electrically insulate the gate electrode 330 from the source electrode 360 and the drain electrode 370. Any of the materials may be used. Examples of the inorganic material include normally known insulating oxides such as SiO ₂ , SiN _x , SiON, Al ₂ O ₃ , and HfO ₂ , nitrides, and oxynitrides. Examples of the organic material include acrylic resin, epoxy resin, silicon resin, and fluorine resin. The organic material is preferably a photocurable resin material because it is easy to manufacture and process.
Incidentally, when glass is used for the substrate 320, the insulator layer (gate insulator layer) 340 has a two-layer laminated structure in which a SiN layer is disposed at a contact portion of the substrate 320 and SiO ₂ is disposed thereon. Is preferred. This SiN layer can prevent the calcium, phosphorus, etc. generated from the substrate 320 from diffusing and deteriorating the semiconductor layer 350, and the SiO ₂ disposed thereon is caused by the diffusion of nitrogen from the SiN layer. This is because deterioration of the semiconductor layer can be prevented.

<Interlayer insulating film 380>
The interlayer insulating film 380 has insulating properties, and can electrically insulate the source electrode 360, the drain electrode 370, and the source electrode 360 and the semiconductor layer 350 in a region not overlapping with the drain electrode 370. If so, it may be formed using either an inorganic material or an organic material. Examples of the inorganic material include normally known insulating oxides such as SiO ₂ , SiN _x , SiON, Al ₂ O ₃ , and HfO ₂ , nitrides, and oxynitrides. Examples of the organic material include acrylic resin, epoxy resin, silicon resin, and fluorine resin. The organic material is preferably a photocurable resin material because it is easy to manufacture and process.

<Method for producing oxide semiconductor>
Next, a method for manufacturing the oxide semiconductor of the fifth invention of the present application will be described. In this embodiment, the semiconductor layer 350 of FIG. 15 is formed.
The oxide semiconductor of this embodiment can also be formed by using physical vapor deposition (or physical vapor deposition).
Here, examples of physical vapor deposition include vapor deposition and sputtering. Examples of the vapor deposition method include vacuum vapor deposition, molecular beam vapor deposition (MBE), ion plating, and ion beam vapor deposition. Examples of the sputtering method include conventional sputtering, magnetron sputtering, ion beam sputtering, ECR (electron cyclotron resonance) sputtering, and reactive sputtering. When plasma is used in the sputtering method, a film forming method such as a reactive sputtering method, a DC (direct current) sputtering method, or a radio frequency (RF) sputtering method can be used.
In forming the semiconductor layer 350, the first metal oxide composed of a metal oxide capable of generating electron carriers by introducing oxygen vacancies, and the oxygen separation energy of the first metal oxide is greater than the oxygen separation energy of the first metal oxide. First, an oxide semiconductor having an oxygen deficient portion, which is formed from a second oxide that is greater than or equal to 200 kJ / mol, is formed. Specifically, a target that is a sintered body including a first metal oxide powder and an oxide powder having an oxygen separation energy of 200 kJ / mol or more larger than the oxygen separation energy of the first metal oxide; It is manufactured by a physical vapor deposition method using a mixed gas of a rare gas and oxygen. Here, it demonstrates as using sputtering method as a physical vapor deposition method.

For example, a first metal oxide composed of a metal oxide capable of generating electron carriers by introducing oxygen vacancies, and the oxygen separation energy of the first metal oxide is 200 kJ / mol or more larger than the oxygen separation energy of the first metal oxide. In the case where an In—Si—O-based metal oxide is used as the oxide semiconductor formed of the second oxide and having an oxygen deficiency, the target is an indium oxide powder and a silicon oxide powder. It is preferable to employ a sintered body. Further, the target may be mixed with impurities such as an additive (metal oxide or the like) at a weight percent or less of silicon oxide. For example, metal oxides (such as zinc oxide) other than indium oxide and silicon oxide may be mixed into the target at a ratio (weight ratio) equal to or lower than the silicon oxide content in the entire target as unintended impurities. Absent.

In that case, the content of silicon oxide contained in the sintered body is preferably more than 0% by weight and 50% by weight or less. Further, the content of silicon oxide is more preferably more than 0 wt% and not more than 5 wt%.

In In-Zn-O-based and In-Ga-Zn-O-based metal oxides, which are generally known oxide semiconductors, if indium oxide is the "host material" and zinc oxide or gallium oxide is the "guest material" The guest material (zinc oxide or gallium oxide) is mixed with 20-30% of the host material (indium oxide).

In contrast, in this embodiment, a thin film is formed using the sintered body as described above as a target. In the oxide semiconductor manufactured by the manufacturing method of the present embodiment, the silicon oxide content is more preferably more than 0 wt% and not more than 5 wt% as described above. Therefore, the semiconductor layer in this preferred composition The 350 oxide semiconductor has an extremely small content of the guest material (silicon oxide) with respect to the host material (indium oxide) as compared with a conventionally known oxide semiconductor.

In the oxide semiconductor manufacturing method of this embodiment, a mixed gas of a rare gas and oxygen is used as a process gas. Examples of the rare gas include helium, neon, argon, krypton, and xenon. Further, the process gas does not include a compound having a hydrogen atom.

In addition, in the method for manufacturing an oxide semiconductor according to the present embodiment, according to the study of the inventor, the first metal oxide composed of a metal oxide capable of generating electron carriers by introducing oxygen vacancies, and the oxygen separation energy. In producing an oxide semiconductor having an oxygen deficient portion, which is formed from a second oxide having a larger oxygen dissociation energy than the first metal oxide by 200 kJ / mol or more, indium oxide and silicon oxide are used. In the case where a target including the oxide semiconductor is used, it has been found that a high temperature is not required to make the metal oxide constituting the oxide semiconductor an amorphous film. Therefore, in the method for manufacturing the thin film transistor 310 of this embodiment, an amorphous oxide semiconductor is formed by performing the step of forming an In—Si—O system into which oxygen vacancies are introduced at 10 ° C. or higher and 200 ° C. or lower. can do. In addition, by performing the treatment at a temperature higher than 200 ° C. and lower than or equal to 400 ° C., a suitable crystallized oxide semiconductor can be formed. Further, the step of forming the oxide semiconductor is preferably performed at room temperature. Here, “implemented at room temperature” means non-heating for the step of forming an oxide semiconductor, and does not require temperature adjustment of the working environment.

As the sputtering method employed in the method for manufacturing an oxide semiconductor according to this embodiment, known methods such as RF sputtering and DC sputtering can be used.

Further, the target may be a sintered body of a mixture of these powders or a sintered body of each powder, as long as the target uses indium oxide powder and silicon oxide powder. In the case where a sintered body is formed for each metal oxide powder, an oxide semiconductor in which the amount of oxygen vacancies is controlled by co-sputtering using a plurality of sintered bodies can be formed.

The same method as described above should be used even when a metal oxide combining zinc oxide and tin oxide or indium oxide, gallium oxide, zinc oxide and tin oxide is used as the first metal oxide instead of indium oxide. Thus, an oxide semiconductor in which the amount of oxygen vacancies is controlled can be formed.

Silicon oxide has been described as the second oxide, but instead zirconium oxide (Zr—O), praseodymium oxide (Pr—O), lanthanum oxide (La—O), tantalum oxide (Ta—O), and oxidation Even when hafnium (Hf—O) is used, an oxide semiconductor in which the amount of oxygen vacancies is controlled can be formed in a process range corresponding to the magnitude of the separation energy of oxygen.

Next, a substituent is introduced into the oxygen deficient portion of the oxide semiconductor having the oxygen deficient portion thus manufactured. As the substituent to be introduced, at least one selected from the group consisting of OH group, H group, F group, Cl group, or B group can be used.
In addition, when an OH group is introduced into the oxygen deficient part, it is introduced by heat treatment under high humidity. For example, it sealed 80% or more high humidity of introducing H _{2 O} gas into the quartz reaction vessel, at a temperature range of 300 ° C. from 0.99 ° C., introduced by heat treatment.
In addition, when introducing an H group into the oxygen deficient portion, it is introduced by heat treatment in an H ₂ atmosphere gas. For example, it is introduced by annealing at 300 to 400 ° C. under H ₂ atmosphere gas.
In addition, when an F group, a Cl group, or a B group is introduced into the oxygen deficient portion, it is introduced by ion implantation (ion implantation) or a plasma treatment method.

In the above, the manufacturing method of the oxide semiconductor of this embodiment was demonstrated.

<Method for Manufacturing Thin Film Transistor 310>
Next, a method for manufacturing the thin film transistor 310 using the oxide semiconductor of the fifth invention of the present application will be described.

In the method of manufacturing the thin film transistor 310 of this embodiment, the gate electrode 330 and the insulator layer (gate insulator layer) 340 are formed on the substrate 320 by a generally known method, and then the semiconductor is formed on the upper surface of the insulator layer 340. Layer 350 is formed. The semiconductor layer 350 is formed using an oxide semiconductor manufactured by the above-described manufacturing method. The gate electrode 330 is provided so as to correspond to the channel region of the semiconductor layer 350 (at a position overlapping the channel region in a plan view). Further, the source electrode 360 and the drain electrode 370 are provided on the semiconductor layer 350 so that a part of the semiconductor layer 350 overlaps the source electrode 360 and the drain electrode 370 by a generally known method, and further, the whole (specifically, Covers the source electrode 360, the drain electrode 370, and the semiconductor layer 350 in a region not overlapping with the source electrode 360 and the drain electrode 370, with the interlayer insulating film 380.
In this manner, the thin film transistor 310 with high reliability with respect to light irradiation from the light emitting layer can be manufactured.

According to the thin film transistor of the fifth invention of this application illustrated in FIG. 15 as described above, the change in characteristics is suppressed by using a novel oxide semiconductor for the semiconductor layer.

In addition, the semiconductor device using the thin film transistor having such a structure has high reliability because it has a thin film transistor in which the characteristic change is suppressed.

Further, according to the method for manufacturing a thin film transistor as described above, a thin film transistor in which a change in characteristics is suppressed by using a novel oxide semiconductor for a semiconductor layer can be easily manufactured.

In the present embodiment, a so-called bottom gate type thin film transistor has been described. However, the fifth invention of the present application can also be applied to a so-called top gate type thin film transistor.

In this embodiment, a so-called top contact type thin film transistor has been described. However, the fifth invention of the present application can also be applied to a so-called bottom contact type thin film transistor.

As described above, the preferred embodiment according to the fifth invention of the present application has been described with reference to the accompanying drawings, but it is needless to say that the fifth invention of the present application is not limited to such an example. Various shapes, combinations, and the like of the constituent members shown in the above-described examples are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the fifth invention of the present application.

Hereinafter, the first to third inventions of the present application will be described by examples, but the first to third inventions of the present application are not limited to these examples.

(Example A1)
In this example, the thin film transistor shown in FIG. 2 was manufactured and the operation was confirmed. The thin film transistor shown in the figure has substantially the same configuration as that of the thin film transistor 10 shown in FIG. 1, and instead of the gate electrode 30 included in the thin film transistor 10 shown in FIG. Is used.

The thin film transistor of the example uses a Si substrate doped with a p-type impurity, forms the insulator layer 24 by oxidizing the surface, and then forms the semiconductor layer 25 on the surface of the insulator layer 24 using a method described later. It was manufactured by doing. The source electrode 26 and the drain electrode 27 were formed by mask vapor deposition on the surface of the semiconductor layer 25.

The source electrode 26 and the drain electrode 27 were made of gold (Au) as a forming material and had a thickness of 50 nm. Further, the separation distance (gate length) between the source electrode 26 and the drain electrode 27 was 350 μm, and the length of the facing portion was 940 μm.

The oxide semiconductor layer 25 uses an In—Si—O target with a SiO ₂ concentration of 10% by weight and an In—Ti—O target with a Ti concentration of 10% by weight. Flow rate: O ₂ / Ar = 3 sccm / 20 sccm, degree of vacuum 0.25 Pa, without heating, as shown in Table A3, continuously changing the sputtering power for each target according to the film thickness formed, An In—Ti—Si—O film with a thickness of 60 nm was formed.

FIG. 4 shows the results obtained by depth resolution XPS measurement of the concentration distribution of Ti and Si elements in the fabricated In—Ti—Si—O film while Ar etching. An In—Ti—Si—O film having a high Ti concentration, a low Si concentration, and a reverse concentration gradient in the central portion was formed on the side close to the gate insulating film 24 and the source / drain electrode 26/27 side.

(Example A2)
Using an In—Si—O target similar to that in Example A1, an In—Si—O—N film was produced with a DC power of 200 W and no heating. The conditions of the sputtering gas at this time are as shown in Table A4. An In—Si—O film was formed under the conditions of O ₂ / Ar = ₂ sccm / 30 sccm, and the In—Si—O film was continuously changed while changing the composition. N ₂ gas was introduced only at the center of the —O film (N ₂ / Ar = ₂ sccm / 30 sccm). FIG. 5 shows the result obtained by measuring the N concentration distribution of this film by depth resolution XPS measurement while performing Ar etching.

(Evaluation)
In order to evaluate the characteristics of the In-Ti-Si-O thin film transistor manufactured in Example A1, the electron mobility (cm ² / Vs) is determined from the Id-Vg characteristics, in an evaluation environment of 25 ° C., in the dark, with Vds = 15 V constant. The initial threshold voltage was determined. Subsequently, FIG. 6 shows the electron mobility and threshold voltage shift (difference from the initial threshold voltage) after 1000 seconds of light irradiation with a wavelength of 420 to 600 nm.
In order to evaluate the characteristics of the In—Si—O—N thin film transistor manufactured in Example A2, the Id—Vg characteristics after an evaluation environment of 25 ° C. and light irradiation for 1000 seconds were measured. The results are shown in FIG.
For comparison, FIG. 7 also shows the Id—Vg characteristics of an In—Ti—O thin film transistor. It can be seen that by irradiation with light having a wavelength of 420 to 600 nm, the I-off value of In—Ti—O increases and the threshold voltage also shifts to the negative side. On the other hand, the In—Si—O—N thin film transistor had almost the same characteristics after light irradiation as before light irradiation, and hardly deteriorated.
Note that the Id-Vg characteristics of the In—Si—O—N thin film transistor and the In—Ti—O thin film transistor before light irradiation were substantially the same as those indicated by the broken line in FIG.

For comparison, only the metal semiconductor layer was changed to In—Ga—Zn—O (IGZO), and the other data plotted were the electron mobility and threshold voltage shift data measured for the same thin film transistor as in Example A1. The 60 nm-thick IGZO film of this thin film transistor is a DC sputtering method using an IGZO target (In ₂ O ₃ : Ga ₂ O ₃ : ZnO = 1: 1: 1 (mol ratio)) at room temperature and a sputtering gas flow rate: It was produced under the conditions of Ar / O ₂ = 21.5 sccm / 1.5 sccm and DC power of 100 W.
The results are also shown in FIG. The thin film transistor using IGZO has a large threshold voltage shift of about 2 V due to light irradiation, and the electron mobility is as small as 5 cm ² / Vs. On the other hand, the thin film transistor using In—Ti—Si—O of Example A1 showed a high threshold voltage shift smaller than 1 V and an electron mobility close to 10 cm ² / Vs.
In addition, the thin film transistor using In—Ti—Si—O of Example A1 has low contact resistance at the interface between the source electrode 26 / drain electrode 27 and the semiconductor layer 25, and has excellent gate controllability. It was.

From the above results, the operation of the thin film transistor of the first to third inventions of the present application was confirmed, and the usefulness of the first to third inventions of the present application was confirmed.

Hereinafter, the fourth invention of the present application will be described by examples, but the fourth invention of the present application is not limited to these examples.

[First Example (Example B1)]
In this example corresponding to the first embodiment, the thin film transistor shown in FIG. 10 was manufactured and the operation was confirmed. The thin film transistor shown in the figure has the same structure as that of the thin film transistor 201 shown in FIG. 8, and uses a Si layer 211 doped with a large amount of p-type impurities in place of the gate electrode 203 included in the thin film transistor 201 shown in FIG. It has become.

The thin film transistor of the example uses a Si substrate doped with a p-type impurity, forms the insulator layer 204 by oxidizing the surface, and then forms the semiconductor layer 205 on the surface of the insulator layer 204 using a method described later. It was manufactured by doing. The source electrode 208 and the drain electrode 209 were formed by mask vapor deposition on the surface of the semiconductor layer 205.

The source electrode 208 and the drain electrode 209 are made of gold (Au) and have a thickness of 50 nm. Further, the separation distance (gate length) between the source electrode 208 and the drain electrode 209 was 350 μm, and the length of the facing portion was 940 μm.

The semiconductor layer 205 was formed by a sputtering method (DC sputtering) using a sputtering apparatus and using a Sn—W—O target as a target material under the following sputtering conditions. As the Sn—W—O target, a 20% W-added Sn-based sample product was used. The thickness of the deposited semiconductor layer 205 was 20 nm.

(Sputtering conditions)
DC power: 200W
Degree of vacuum: 0.2 Pa
Process gas flow rate: Ar 20 sccm / O _{2 2} sccm
(Sccm: Standard Cubic Centimeter per Minute)
Substrate temperature: 25 ° C. Without heating

The characteristics of the thin film transistor thus fabricated were measured under the evaluation environment of 25 ° C. in a dark place and in a vacuum. FIG. 11 shows the measurement results of the transfer characteristics of this thin film transistor.

In addition, FIG. 12 shows the electrical conduction characteristics of Sn—O and Sn—W—O thin film transistors when the ratio of O ₂ / (Ar + O ₂ ) is changed in the range of 5 to 25% under the above sputtering conditions. . Sn—W—O exhibits superior electrical conductivity compared to Sn—O at all oxygen ratios in FIG. This is suitable from tin oxide (Sn—O) with high accuracy because the oxygen dissociation energy of W—O bond (720 ± 71 kJ / mol) is larger than that of Sn—O (528 kJ / mol). This is the effect of controlling the amount of oxygen deficiency by desorbing oxygen. In addition, Sn—W—O indicates that the change in electrical conduction characteristics is smaller than the change in the ratio of O ₂ / (Ar + O ₂ ). From this result, it can be seen that Sn—W—O has a larger process margin.

[Second Example (Example B2)]
Also in this example corresponding to the second embodiment, the thin film transistor shown in FIG. 10 was manufactured and the operation was confirmed. The semiconductor layer 205 was formed by a sputtering method (DC sputtering) using a sputtering apparatus and using a Sn—W—Yb—O target as a target material under the following sputtering conditions. As the Sn—W—O target, 20% W and 2% Yb-added Sn-based sample products were used. The thickness of the deposited semiconductor layer 205 was 20 nm.

(Sputtering conditions)
DC power: 150W
Degree of vacuum: 0.2 Pa
Process gas flow rate: Ar 20 sccm / O _{2 2} sccm
(Sccm: Standard Cubic Centimeter per Minute)
Substrate temperature: 25 ° C. Without heating

In order to investigate the crystal structure of the Sn—W—Yb—O film by post-heat treatment, a 20 nm-thick Sn—W—O film was formed on a glass substrate and heat-treated at 450 ° C. for 15 minutes in the atmosphere. The diffraction pattern is shown in FIG. Only a glass substrate is also shown for comparison. Even when heat-treated at 450 ° C. for 15 minutes, no peak was observed, indicating that the film was amorphous.

The characteristics of the thin film transistor manufactured using this amorphous Sn—W—Yb—O film were measured under the evaluation environment of 25 ° C. in a dark place and in a vacuum. FIG. 14 shows the results of measuring the characteristics of the thin film transistor of the fourth invention.

From the above results, the operation of the thin film transistor of the fourth invention of the present application was confirmed, and the usefulness of the fourth invention of the present application was confirmed.

Hereinafter, the fifth invention of the present application will be described by Example C, but the fifth invention of the present application is not limited to these Examples.

In Example C, the thin film transistor 400 shown in FIG. 16 was manufactured and the operation was confirmed. In the thin film transistor 400 shown in FIG. 16, a substrate 450 that is a Si layer doped with a large amount of p-type impurities is used as the gate electrode instead of the gate electrode 330 shown in FIG.

The thin film transistor of Example C uses a Si substrate 450 doped with a p-type impurity, forms an insulator layer 410 by oxidizing the surface, and then forms an oxide semiconductor on the surface of the insulator layer 410 using a method described later. The semiconductor layer 420 was formed. The source electrode 430 and the drain electrode 440 were formed by mask vapor deposition on the surface of the semiconductor layer 420 of an oxide semiconductor.

The source electrode 430 and the drain electrode 440 are made of gold (Au) and have a thickness of 50 nm. Further, the distance (gate length) between the source electrode 430 and the drain electrode 440 was 350 μm, and the length of the facing portion was 940 μm.

In this example C, an oxide semiconductor layer 420 was fabricated as follows.

<Fabrication of In—Si—O Semiconductor Semiconductor Layer 420 with In—OH Bond>
The semiconductor layer 420 of an In—Si—O semiconductor having an In—OH bond was manufactured as follows.
First, an In—Si—O semiconductor into which oxygen vacancies have been introduced is used by using a sputtering apparatus and an In—Si—O target having a SiO ₂ content of 10 wt% as a target material, and O ₂ / Ar = 3 sccm / An In—Si—O film having a thickness of 60 nm was formed under sputtering conditions of 20 sccm, a degree of vacuum of 0.25 Pa, and no heating, followed by heat treatment at 150 ° C. for 10 minutes in the atmosphere.
Next, by introducing H ₂ O gas into a sealed quartz reaction vessel under a high humidity of 80% or more in a temperature range of 150 ° C. to 300 ° C., and introducing —OH groups into oxygen deficient portions. A semiconductor layer 420 of an In—Si—O semiconductor having an In—OH bond was manufactured. The OH group content introduced in Example C was 0.5%. The confirmation was performed by an XPS spectrum derived from the indium 3d orbital (hereinafter referred to as “In3d XPS spectrum”).
FIG. 17 shows the results of In3d XPS spectra of the In—Si—O film before and after the heat treatment at 150 ° C. In FIG. 17, (a) is an In3dXPS spectrum of an In—Si—O semiconductor before the heat treatment, and (b) is an In3dXPS spectrum of an In—Si—O semiconductor having an In—OH bond after the heat treatment. As can be seen from FIG. 17, the peak position due to the In—OH bond in the In—Si—O semiconductor into which the —OH group was introduced after the heat treatment was found at 444 eV, and the In—Si—O semiconductor before the heat treatment was observed. The peak position due to the In—O bond in is observed at 443.5 eV. Therefore, the peak position due to the In—OH bond in the In—Si—O semiconductor into which the —OH group is introduced after the heat treatment is the peak position due to the In—O bond in the In—Si—O semiconductor before the heat treatment. On the other hand, it turns out that it has shifted to the high energy side.
The content of OH groups to be introduced is preferably 0.1% or more and 10% or less. If it becomes 10% or less, it is possible to avoid a source of mobile ions (herein, “mobile ions” means ions localized in the oxide corresponding to the application of positive and negative voltages). This is because the metal behavior can be prevented from being more than the property of the semiconductor.

<Fabrication of In—Si—O Semiconductor Semiconductor Layer Having In—H Bond>
Regarding introduction of H groups into an In—Si—O semiconductor into which oxygen vacancies were introduced, an In—Si—O semiconductor into which oxygen vacancies were introduced was first produced in the same manner as the introduction of OH groups.
Next, the In—Si—O semiconductor into which oxygen vacancies have been introduced is annealed at 300 to 400 ° C. in an H ₂ atmosphere gas, thereby introducing H groups into the oxygen vacancy and having In—H bonds. A semiconductor layer 420 of an In—Si—O semiconductor was manufactured. The confirmation was performed by In3d XPS spectrum.
The content of H group to be introduced is preferably greater than 0% and 0.1% or less in order to maintain semiconducting properties.

<Fabrication of In—Si—O Semiconductor Semiconductor Layer Having At least One In—F, In—Cl, In—B Bond>
Regarding the introduction of F, Cl, and B groups into an In—Si—O semiconductor into which oxygen vacancies were introduced, an In—Si—O semiconductor into which oxygen vacancies were introduced was first produced in the same manner as the introduction of OH groups.
Next, at least one ion of F, Cl, and B is added to the In—Si—O semiconductor into which oxygen vacancies are introduced at 1 × 10 ¹⁸ atoms / cm ³ or more and 1 × 10 ²¹ atoms / cm ³ or less. In the case of In which has at least one In-F, In-Cl, or In-B bond by ion-implanting within the range of the content of at least one of them, thereby introducing at least one group of F, Cl, and B into the oxygen deficient portion. A semiconductor layer 420 of —Si—O semiconductor was produced. The confirmation was performed by In3d XPS spectrum.
Incidentally, as a method for introducing these ions, a plasma processing method may be used instead of ion implantation.

<Reliability evaluation of thin film transistor using In—Si—O semiconductor having In—OH bond>
The characteristics of the thin film transistor illustrated in FIG. 16 manufactured using an In—Si—O semiconductor having an In—OH bond (OH content: 0.5%) manufactured by the above-described method are as follows: evaluation environment is 25 ° C., V _ds (Drain voltage) = 15 V (constant), and evaluation was performed based on I _d (drain current) −V _g (gate voltage) characteristics. For comparison, thin film transistors that differ only in the use of In—Si—O semiconductors into which OH groups were not introduced were also produced.
FIG. 18 shows the result of showing the I _d -V _g characteristics after irradiation with light having a wavelength of 420 nm or more and 600 nm or less for 100 seconds. FIG. 18A shows the I _d -V _g characteristics of an In—Si—O semiconductor into which OH groups have not been introduced before light irradiation and an In—Si—O semiconductor having an In—OH bond before light irradiation. (B) shows the I _d -V _g characteristics of an In—Si—O semiconductor having an In—OH bond after light irradiation, and (c) shows an In group in which no OH group has been introduced after light irradiation. The I _d -V _g characteristic of the —Si—O semiconductor is shown.
As shown in FIG. 18, the I _d -V _g characteristics of the thin film transistor using the In—Si—O semiconductor having In—OH bonds before and after the light irradiation were almost the same. On the other hand, the I _d -V _g characteristics before and after the light irradiation of the thin film transistor using an In—Si—O semiconductor into which no OH group is introduced show that the I _d curve shifts to the negative side compared to before the light irradiation, and is off. The current (I _off ) value also tended to increase.
Therefore, a thin film transistor using an In—Si—O semiconductor into which no OH group has been introduced cannot sufficiently suppress “threshold voltage shift” with respect to light irradiation having a wavelength of 420 nm to 600 nm. It was found that the “threshold voltage shift” can be sufficiently suppressed by introducing a group.

In the first to third inventions of the present application, characteristic deterioration such as shift of threshold current due to light irradiation is suppressed, contact resistance at the interface between the source electrode and / or drain electrode and the semiconductor layer is low, and electron mobility is low. It is possible to provide thin film transistors that have high practical value, such as high gate control, and can be used in various industrial fields including liquid crystal displays and organic EL displays. Have sex.

In addition, as described above, according to the fourth invention of the present application, since it is possible to realize a composite metal oxide semiconductor layer in which the amount of oxygen vacancies is controlled, it is possible to greatly contribute to improving the performance of the thin film transistor. .

Furthermore, as described above, according to the fifth invention of the present application, it is possible to provide an oxide semiconductor that can sufficiently suppress a “threshold voltage shift” induced by light emission from the light emitting layer. The present invention can be applied to a semiconductor device such as a semiconductor element such as a thin film transistor and an electronic device such as an organic EL display or a liquid crystal display for which improvement in reliability with respect to light irradiation from a layer is desired.

110, 110 'thin film transistor 120 substrate 121 p-doped Si layer 130 gate electrode 140, 124 insulating film layer 150, 125 semiconductor layer 160, 126 source electrode 170, 127 drain electrode 180 interlayer insulating film 201, 201'-thin film transistor 202- --Substrate 203 --- Gate electrode 204 --- Insulating film layer 205, 205 '--- Semiconductor layer 206 --- Tin oxide 207 --- Metal oxide 208 --- Source electrode 209 --- Drain electrode 210 --- oxide 211 --- Si substrate 310 doped with p-type impurities, 400 --- thin film transistor 320 --- substrate 330 --- gate electrodes 340, 410 --- insulator layers 350, 420-- -Semiconductor layers 360, 430--source electrodes 370, 440--drain electrodes 380--interlayer insulating film 450--Si layer substrate doped with a large amount of p-type impurities (gate Electrode)

Claims (57)

A source electrode and a drain electrode;
A semiconductor layer provided in contact with the source electrode and the drain electrode;
A gate electrode provided corresponding to a channel between the source electrode and the drain electrode;
A thin film transistor having an insulator layer provided between the gate electrode and the semiconductor layer,
The semiconductor layer has a second metal oxide that can generate electron carriers by introducing oxygen vacancies, and the second energy of oxygen is 200 kJ / mol or more higher than that of the first metal oxide. Formed of a complex metal oxide to which an oxide (XOx) is added,
Among the elements X constituting the second oxide, the concentration of at least one element X ¹ selected from the group consisting of silicon, tantalum, zirconium, hafnium, aluminum, yttrium, and rare earth elements is in the thickness direction of the semiconductor layer. The thin film transistor, which exhibits a maximum value in the center. 2. The thin film transistor according to claim 1, wherein the concentration of the element X <b> ¹ exhibits a maximum value at a central portion in a thickness direction of the semiconductor layer. A source electrode and a drain electrode;
A semiconductor layer provided in contact with the source electrode and the drain electrode;
A gate electrode provided corresponding to a channel between the source electrode and the drain electrode;
A thin film transistor having an insulator layer provided between the gate electrode and the semiconductor layer,
The semiconductor layer has a second metal oxide that can generate electron carriers by introducing oxygen vacancies, and the second energy of oxygen is 200 kJ / mol or more higher than that of the first metal oxide. Formed of a complex metal oxide to which an oxide (XOx) is added,
Among the elements X constituting the second oxide, the concentration of at least one element X ² that does not correspond to any of silicon, tantalum, zirconium, hafnium, aluminum, yttrium, and rare earth elements is in the thickness direction of the semiconductor layer. The thin film transistor, which exhibits a minimum value in the center. 4. The thin film transistor according to claim 3, wherein the concentration of the element X ² has a minimum value at a central portion in a thickness direction of the semiconductor layer. A source electrode and a drain electrode;
A semiconductor layer provided in contact with the source electrode and the drain electrode;
A gate electrode provided corresponding to a channel between the source electrode and the drain electrode;
A thin film transistor having an insulator layer provided between the gate electrode and the semiconductor layer,
The semiconductor layer has a second metal oxide that can generate electron carriers by introducing oxygen vacancies, and the second energy of oxygen is 200 kJ / mol or more higher than that of the first metal oxide. Formed of a complex metal oxide to which an oxide (XOx) is added,
The above-mentioned thin film transistor, wherein the semiconductor layer further contains nitrogen, and the concentration of nitrogen shows a maximum value at a central portion in the thickness direction of the semiconductor layer. The thin film transistor according to any one of claims 1 to 5, wherein an oxygen separation energy of the second oxide is greater by 255 kJ / mol or more than an oxygen separation energy of the first metal oxide. The thin film transistor according to any one of claims 1 to 5, wherein the first metal oxide is an oxide of at least one metal selected from the group consisting of indium, gallium, zinc, and tin. The thin film transistor according to any one of claims 1 to 5, wherein the second oxide is an oxide of at least one metal selected from the group consisting of zirconium (Zr) and praseodymium (Pr). The thin film transistor according to claim 6, wherein the second oxide is at least one oxide selected from the group consisting of silicon (Si), tantalum (Ta), lanthanum (La), and hafnium (Hf). 10. The thin film transistor according to claim 1, wherein the content of the second oxide in the semiconductor layer is greater than 0 and 50 wt% or less. 11. The thin film transistor according to claim 1, wherein the content of the second oxide in the semiconductor layer is greater than 0 and 5% by weight or less. The thin film transistor according to any one of claims 1 to 11, wherein the semiconductor layer is amorphous. The thin film transistor according to any one of claims 1 to 12, wherein a thickness of the semiconductor layer is in a range of 5 nm or more and 20 nm or less. The thin film transistor according to any one of claims 1 to 5, wherein the second oxide is an oxide of at least one element selected from the group consisting of boron (B) and carbon (C). The thin film transistor according to claim 14, wherein the content of boron (B) and carbon (C) in the semiconductor layer is greater than 0 and 10 wt% or less. The semiconductor layer is formed at a temperature of 10 ° C. or higher and 400 ° C. or lower;
The method for manufacturing a thin film transistor according to claim 1. The method for manufacturing a thin film transistor according to claim 16, wherein the semiconductor layer is formed at a temperature of 10 ° C or higher and 200 ° C or lower. An apparatus having the thin film transistor according to any one of claims 1 to 15. The apparatus according to claim 18, which is a liquid crystal display or an organic EL display. A source electrode and a drain electrode;
A semiconductor layer provided in contact with the source electrode and the drain electrode;
A gate electrode provided corresponding to a channel between the source electrode and the drain electrode;
Providing an insulator layer provided between the gate electrode and the semiconductor layer;
The thin film transistor in which the semiconductor layer is a composite metal oxide in which tin oxide is added with a metal oxide having an oxygen separation energy larger than that of tin oxide and a difference from the oxygen separation energy of tin oxide being less than 200 kJ / mol. 21. The thin film transistor according to claim 20, wherein the semiconductor layer includes an additional oxide whose oxygen dissociation energy is smaller than that of tin oxide in an amount smaller than that of the metal oxide. The thin film transistor according to claim 21, wherein the content of the additional oxide in the semiconductor layer is 20 wt% or less. 23. The thin film transistor according to claim 22, wherein the content of the additional oxide in the semiconductor layer is 4% by weight or less. The thin film transistor according to any one of claims 20 to 23, wherein the semiconductor layer is amorphous. The thin film transistor according to any one of claims 20 to 24, wherein a thickness of the semiconductor layer is 5 nm or more and 20 nm or less. 26. The thin film transistor according to claim 21, wherein the additional oxide is at least one oxide selected from the group consisting of lead, palladium, platinum, sulfur, antimony, strontium, thallium, and ytterbium. 27. The thin film transistor according to claim 20, wherein the metal oxide is at least one oxide selected from the group consisting of samarium, tungsten, neodymium, and gadolinium. 28. The thin film transistor according to claim 20, wherein a content of the metal oxide in the semiconductor layer is greater than 0 and 50% by weight or less. The thin film transistor according to claim 28, wherein a content of the metal oxide in the semiconductor layer is 5% by weight or less. 30. The method of manufacturing a thin film transistor according to any one of claims 20 to 29, wherein the semiconductor layer is formed at 10 ° C. or more and 500 ° C. or less. The method of manufacturing a thin film transistor according to claim 30, wherein the semiconductor layer is formed at a temperature of 10 ° C to 300 ° C. A first metal oxide composed of a metal oxide capable of generating electron carriers by introducing oxygen vacancies; and a second metal whose oxygen separation energy is 200 kJ / mol or more larger than the oxygen separation energy of the first metal oxide. An oxide semiconductor comprising an oxide, wherein the metal of the first metal oxide is at least one selected from the group consisting of an OH group, an H group, an F group, a Cl group, or a B group The oxide semiconductor having a bond. The oxide semiconductor according to claim 32, wherein the oxygen separation energy of the second oxide is 255 kJ / mol or more larger than the oxygen separation energy of the first metal oxide. The oxide semiconductor according to claim 32, wherein the metal of the first metal oxide is at least one selected from the group consisting of indium, gallium, zinc, and tin. The second oxide is made of silicon (Si), titanium (Ti), tungsten (W), tantalum (Ta), lanthanum (La), hafnium (Hf), zirconium (Zr), and praseodymium (Pr). The oxide semiconductor according to any one of claims 32 to 34, which is an oxide containing at least one selected from the group consisting of: The second oxide is an oxide containing at least one selected from the group consisting of silicon (Si), titanium (Ti), tungsten (W), tantalum (Ta), lanthanum (La), and hafnium (Hf). 36. The oxide semiconductor according to claim 35, wherein the oxide semiconductor is a product. The oxide semiconductor according to any one of claims 32 to 36, wherein the content of the second oxide is greater than 0 and 50 wt% or less. 38. The oxide semiconductor according to claim 37, wherein the content of the second oxide is greater than 0 and 5% by weight or less. The oxide semiconductor according to any one of claims 32 to 38, wherein the thickness of the oxide semiconductor is in the range of 5 nm to 20 nm. The oxide semiconductor according to any one of claims 32 to 39, wherein the second oxide is an oxide containing carbon (C). 41. The oxide semiconductor according to claim 40, wherein the content of carbon (C) is greater than 0 and 10% by weight or less. The oxide semiconductor according to claim 32, wherein the metal of the first metal oxide is indium, and the oxygen separation energy of the second oxide is 725 kJ / mol or more. The oxide semiconductor according to any one of claims 32 to 42, wherein the metal of the first metal oxide has a bond with an OH group. 44. The oxide semiconductor according to claim 43, wherein a content of the OH group is 0.1% or more and 10% or less. 43. The oxide semiconductor according to claim 32, wherein the metal of the first metal oxide has a bond with an H group. The oxide semiconductor according to claim 45, wherein a content of the H group is greater than 0% and 0.1% or less. 43. The oxide semiconductor according to any one of claims 32 to 42, wherein the metal of the first metal oxide has a bond with at least one selected from the group consisting of an F group, a Cl group, or a B group. . 48. The content of at least one selected from the group consisting of the F group, Cl group, or B group is more than 5 × 10 ¹⁸ atoms / cm ^{3 and not} more than 1 × 10 ²¹ atoms / cm ³ . Oxide semiconductor. The oxide semiconductor according to any one of claims 32 to 48, wherein the oxide semiconductor is amorphous. A thin film transistor comprising the oxide semiconductor according to any one of claims 32 to 49. A source electrode and a drain electrode;
A semiconductor layer provided in contact with the source electrode and the drain electrode;
A gate electrode provided corresponding to a channel between the source electrode and the drain electrode;
Providing an insulator layer provided between the gate electrode and the semiconductor layer;
50. A thin film transistor, wherein the semiconductor layer is formed of the oxide semiconductor according to any one of claims 32 to 49. 52. A semiconductor device comprising the thin film transistor according to claim 51. The method for manufacturing an oxide semiconductor according to any one of claims 32 to 49, wherein the semiconductor layer is formed at 10 ° C or higher and 400 ° C or lower. The method for manufacturing an oxide semiconductor according to any one of claims 32 to 49, wherein the semiconductor layer is formed at 10 ° C or higher and 200 ° C or lower. The first metal oxide powder composed of a metal oxide capable of generating electron carriers by introducing oxygen vacancies, and the oxygen separation energy is 200 kJ / mol or more larger than the oxygen separation energy of the first metal oxide. The first metal is obtained by physical vapor deposition using a target composed of a sintered body with a powder of the second oxide and a process gas that is a mixed gas composed of a rare gas and oxygen and does not contain a compound having a hydrogen atom. Forming an oxide semiconductor including an oxide and the second oxide;
Forming the oxide semiconductor having oxygen vacancies by heat-treating the oxide semiconductor at 150 ° C. in the atmosphere;
By heat-treating the oxide semiconductor having oxygen vacancies in a temperature range of 150 to 300 ° C. under a high humidity of 80% or more introduced with H ₂ O gas, the metal of the first metal oxide, the OH group, and 45. The method of manufacturing an oxide semiconductor according to claim 43 or 44, including a step of forming a bond. The first metal oxide powder composed of a metal oxide capable of generating electron carriers by introducing oxygen vacancies, and the oxygen separation energy is 200 kJ / mol or more larger than the oxygen separation energy of the first metal oxide. The first metal is obtained by physical vapor deposition using a target composed of a sintered body with a powder of the second oxide and a process gas that is a mixed gas composed of a rare gas and oxygen and does not contain a compound having a hydrogen atom. Forming an oxide semiconductor including an oxide and the second oxide;
Forming the oxide semiconductor having oxygen vacancies by heat-treating the oxide semiconductor at 150 ° C. in the atmosphere;
Forming a bond between the metal of the first metal oxide and an H group by heat-treating the oxide semiconductor having oxygen vacancies in a temperature range of 300 to 400 ° C. in an H ₂ atmosphere gas. The method for producing an oxide semiconductor according to claim 45 or 46. The first metal oxide powder composed of a metal oxide capable of generating electron carriers by introducing oxygen vacancies, and the oxygen separation energy is 200 kJ / mol or more larger than the oxygen separation energy of the first metal oxide. The first metal is obtained by physical vapor deposition using a target composed of a sintered body with a powder of the second oxide and a process gas that is a mixed gas composed of a rare gas and oxygen and does not contain a compound having a hydrogen atom. Forming an oxide semiconductor including an oxide and the second oxide;
Forming the oxide semiconductor having oxygen vacancies by heat-treating the oxide semiconductor at 150 ° C. in the atmosphere;
By ion-implanting at least one selected from the group consisting of fluorine ions, chlorine ions, or boron ions into the oxide semiconductor having oxygen vacancies, the ions of the metal of the first metal oxide are implanted. The method for producing an oxide semiconductor according to claim 47 or 48, further comprising a step of forming a bond with a group.

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