JP4947942B2 - Sputtering target - Google Patents

Description

  The present invention relates to a sputtering target produced by sintering (hereinafter sometimes simply referred to as a sputtering target or a target) and a method for producing a sputtering target.

  In recent years, the development of display devices has been remarkable, and liquid crystal display devices (LCD), electroluminescence display devices (EL), field emission displays (FED), etc. are used in personal computers, office equipment such as word processors, and control systems in factories. It is used as a display device. Each of these display devices has a sandwich structure in which a display element is sandwiched between transparent conductive oxides.

  As such a transparent conductive oxide, as disclosed in Non-Patent Document 1, indium tin oxide (hereinafter abbreviated as ITO) formed by sputtering, ion plating, or vapor deposition. Is the mainstream.

  Such ITO consists of a predetermined amount of indium oxide and tin oxide, and is excellent in transparency and conductivity, and can be etched with a strong acid, and also has excellent adhesion to the substrate. .

  Although ITO has excellent performance as a transparent conductive oxide material, it has a problem that it must contain a large amount (about 90 atomic%) of indium that is not only a scarce resource but also harmful to living organisms. was there. Further, indium itself causes nodules (projections) during sputtering, and the nodules generated on the target surface are also a cause of abnormal discharge. In particular, when forming an amorphous ITO film for the purpose of improving the etching property, in order to introduce a small amount of water or hydrogen gas into the sputtering chamber, the indium compound on the target surface is reduced and further nodules are generated. There was a problem that it was easy. And when abnormal discharge generate | occur | produced, the problem that a scattered matter adhered as a foreign material to the transparent conductive oxide during film-forming or just after film-forming was seen.

  Thus, it was necessary to reduce indium in ITO due to problems of supply instability (rareness) and harmfulness. However, the maximum solid solubility limit of tin oxide in indium oxide is considered to be around 10%, and if the indium content in ITO is reduced to 90 atomic% or less, tin oxide remains in a cluster form in the target. . Since the resistance of tin oxide is 100 times greater than that of ITO, problems such as accumulation of charge during sputtering, arcing, destruction of the target surface, scattering of fine fragments, generation of nodules and particles have occurred (non- Patent Document 2). Therefore, it has been difficult to reduce the indium content to 90 atomic% or less.

Moreover, although the ITO target which is a sintered compact which consists of a bixbite structure compound substantially represented by In ₂ O ₃ has been studied (Patent Document 1), Sn ₃ In ₄ O ₁₂ or the like is used for the ITO target. Even if a sintered body substantially comprising a bixbite structure compound could be produced, the production condition range was narrow and it was difficult to produce stably. Further, when the content of indium was reduced, it was difficult to produce a sintered body substantially comprising a bixbite structure compound.

Further, in an IZO target composed of indium and zinc, a hexagonal layered compound represented by In ₂ O ₃ (ZnO) _m (m is an integer of 2 to 20) is generated when zinc is in the range of 15 to 20 atomic%. It is known (Non-Patent Document 3). These crystal types have the effect of lowering the resistance of the target and raising the relative density compared to ZnO. However, such a target reduces the amount of indium (increases the amount of zinc), the resistance of the target increases, the relative density decreases, the strength of the target decreases, the film formation rate decreases, etc. There was a risk of problems.

JP 2002-030429 A "Technology of transparent conductive film" (Ohm Publishing Co., Ltd., Japan Society for the Promotion of Science, Transparent Oxide Optoelectronic Materials 166th Committee, 1999) Ceramics 37 (2002) No. 9 p675-678 Journal of the American ceramic society, 81 (5) 1310-16 (1998))

  The present invention suppresses abnormal discharge that occurs when a transparent conductive film is formed by using a sputtering method and a stable target that has low resistance, high theoretical relative density, high strength, a target with reduced indium content, and sputtering. A target capable of performing sputtering and a method for manufacturing the same are provided.

  The inventors of the present invention have made extensive studies to solve the above problems, and can solve these problems by making the crystal structure of the target substantially a bixbite structure, while at the same time reducing the indium content to 60 to 75. It has been found that even if it is reduced within the range of atomic%, etching processability similar to that of IZO and film performance equivalent to that of ITO can be exhibited.

  In addition, the transparent conductive film formed by sputtering using this target is excellent in conductivity, etching property, heat resistance, etc. even if indium is reduced, and various types of displays such as liquid crystal displays, touch panels, solar cells, etc. The present invention has been completed by finding out that it is suitable for use and can be applied to film formation of a transparent oxide semiconductor typified by TFT (Thin Film Transistor) by adjusting film formation conditions.

According to the present invention, the following sputtering target and the like are provided.
[1] A sputtering target containing indium, tin, zinc, and oxygen, wherein only a peak of a bixbite structure compound is substantially observed by X-ray diffraction (XRD).
[2] The sputtering target according to [1], wherein the bixbite structure compound is represented by In ₂ O ₃ .
[3] The atomic ratio represented by In / (In + Sn + Zn) is a value within a range larger than 0.6 and smaller than 0.75, and the atomic ratio represented by Sn / (In + Sn + Zn) is 0.11 to 0.11. The sputtering target according to [1] or [2], wherein the sputtering target has a value within a range of 0.23.
[4] Regarding the peak in X-ray diffraction (XRD), the maximum peak position of the bixbite structure compound is shifted in the plus direction (wide angle side) relative to that of the single crystal powder [1] ] The sputtering target according to any one of [3].

[5] The sputtering target according to any one of [1] to [4] above, wherein the average diameter of Zn aggregates observed with an electron beam microanalyzer (EPMA) is 50 μm or less.
[6] The sputtering target according to any one of [1] to [5], wherein the Cr and Cd contents are each 10 ppm (mass) or less.
[7] The sputtering target according to any one of [1] to [6], wherein the contents of Fe, Si, Ti, and Cu are each 10 ppm (mass) or less.
[8] The sputtering target according to any one of [1] to [7] above, wherein the crystal grain size of the bixbite structure compound is 20 μm or less.

[9] The sputtering target according to any one of [1] to [8] above, wherein the bulk resistance is in the range of 0.2 to 100 mΩ · cm.
[10] The sputtering target according to any one of [1] to [9], wherein the theoretical relative density is 90% or more.
[11] A compound of indium, tin and zinc, which is a raw material of the sputtering target, has an atomic ratio represented by In / (In + Sn + Zn) within a range larger than 0.6 and smaller than 0.75, and Sn / ( A step of obtaining a blended mixture having an atomic ratio represented by (In + Sn + Zn) within a range of 0.11 to 0.23;
Pressure-molding the mixture to produce a molded body;
A step of raising the temperature of the molded body within a range of 10 to 1,000 ° C./hour;
Firing the molded body at a temperature in the range of 1,100 to 1,700 ° C. to obtain a sintered body;
Cooling the sintered body within a range of 10 to 1,000 ° C./hour;
The manufacturing method of the sputtering target characterized by including.

[12] A transparent conductive film obtained by forming the sputtering target according to any one of [1] to [10] above by a sputtering method.
[13] A transparent electrode produced by etching the transparent conductive film according to [12].
[14] The transparent electrode as described in [13] above, wherein the taper angle of the electrode end is 30 to 89 degrees.
[15] A method for producing a transparent electrode, wherein the transparent conductive film according to [12] is etched with a 1 to 10% by mass oxalic acid-containing aqueous solution in a temperature range of 20 to 50 ° C.

According to the present invention, a sputtering target having low resistance, high theoretical relative density, and high strength is provided.
ADVANTAGE OF THE INVENTION According to this invention, even if indium content is reduced, the target which can suppress the abnormal discharge generate | occur | produced when forming a transparent conductive film using sputtering method, and can perform sputtering stably is provided. .

  According to the present invention, a film formed by sputtering using the target of the present invention is excellent in conductivity, etching property, heat resistance, etc. even if indium is reduced, and a display or touch panel represented by a liquid crystal display, A transparent conductive film suitable for various uses such as solar cells is provided.

Hereinafter, the present invention will be described in detail.
I. Sputtering Target (I-1) Structure of Sputtering Target The sputtering target of the present invention (hereinafter sometimes referred to as the target of the present invention) contains indium, tin, zinc, and oxygen, and is vixed by X-ray diffraction (XRD). Only the peak of the bite structure compound is substantially observed.

Here, the bixbite structure compound will be described. Bixbyite is also called rare earth oxide C-type or Mn ₂ O ₃ (I) -type oxide. As disclosed in “Technology of Transparent Conductive Films” (Ohm Publishing Co., Ltd., Japan Society for the Promotion of Science, Transparent Oxide / Optoelectronic Materials 166th Committee, 1999), the stoichiometric ratio is M ₂ X ₃ (M is a cation, X is an anion, usually an oxygen ion), and one unit cell is composed of 16 molecules of M ₂ X ₃ , a total of 80 atoms (M is 32, X is 48) Yes. Among these, the bixbite structure compound which is a constituent component of the target of the present invention is a compound represented by In ₂ O ₃ , that is, X-ray diffraction, which is No. 06-JCPDS (Joint Committee on Powder Diffraction Standards) database. It is preferably a peak pattern of 0416 or a similar (shifted) pattern.

  The bixbite structure compound also includes a substitutional solid solution in which atoms and ions in the crystal structure are partially substituted with other atoms, and an interstitial solid solution in which other atoms are added to interstitial positions.

  The crystal state of the compound in the target can be determined by observing a sample collected from the target (sintered body) by an X-ray diffraction method.

“Substantially only the peak of the bixbite structure compound is observed by X-ray diffraction (XRD)” means that X-ray diffraction is No. 06-0416 (In _{2 in} JCPDS (Joint Committee on Powder Diffraction Standards) database). O ₃ single crystal powder) or a similar (shifted) pattern, and the maximum peak of the other structure is less than 5% of the maximum peak of the bixbite structure compound, or is sufficiently small or substantially unidentifiable Means that.
In particular, it is preferable that the peak of SnO ₂ or Sn ₃ In ₄ O ₁₂ is sufficiently small at less than 3% of the maximum peak of the bixbite structure compound by X-ray diffraction method, or it cannot be substantially confirmed. When these compounds are present, the resistance of the target becomes high, and electric charges are easily generated on the target at the time of sputtering, which may cause abnormal discharge or nodule generation.

In the target of the present invention, the atomic ratio represented by In / (In + Sn + Zn) is a value within a range larger than 0.6 and smaller than 0.75, and the atomic ratio represented by Sn / (Sn + Zn) is 0. A value within the range of .4 to 0.6 is preferable.
When the atomic ratio represented by In / (In + Sn + Zn) is expressed by an inequality,
0.6 <In / (In + Sn + Zn) <0.75
And does not include 0.6 and 0.75.
On the other hand, the atomic ratio represented by Sn / (In + Sn + Zn) is
0.11 ≦ Sn / (In + Sn + Zn) ≦ 0.23
And includes 0.11 and 0.23.

  If the atomic ratio represented by In / (In + Sn + Zn) is 0.6 or less, the bixbite structure single layer structure may become unstable and other crystal types may be generated. If it is 0.75 or more, A film formed by sputtering is likely to be crystallized, and the etching rate may be slow, or a residue may be generated after etching. In addition, the effect of reducing indium is insufficient. The atomic ratio represented by In / (In + Sn + Zn) is more preferably a value within the range of 0.61 to 0.69, and still more preferably a value within the range of 0.61 to 0.65. .

When the atomic ratio represented by Sn / (In + Sn + Zn) is smaller than 0.11, a hexagonal layered compound represented by In ₂ O ₃ (ZnO) _m (m is an integer of 2 to 20) or ZnO is generated and the target If it is larger than 0.23, Sn ₃ In ₄ O ₁₂ , SnO ₂ , SnO, etc. may be generated and the resistance of the target may be increased or nodules may be generated.
The atomic ratio represented by Sn / (In + Sn + Zn) is more preferably a value within the range of 0.11 to 0.21, and even more preferably a value within the range of 0.11 to 0.19. A value in the range of 0.12 to 0.19 is particularly preferable.

  Furthermore, the atom represented by Zn / (In + Sn + Zn) preferably has a value in the range of 0.03 to 0.3, more preferably in the range of 0.06 to 0.3. A value in the range of 0.12 to 0.3 is particularly preferable. If the number of atoms represented by Zn / (In + Sn + Zn) is less than 0.03, an etching residue may remain. If more than 0.3, the heat resistance in the atmosphere is deteriorated or the film formation rate is decreased. There is a fear.

  Here, the atomic ratio in the target of the present invention can be measured by inductively coupled plasma (ICP) emission analysis.

In the target of the present invention, the peak position of the bixbite structure compound is preferably shifted in the plus direction (wide angle side) with respect to the X-ray diffraction (XRD) peak position of the In ₂ O ₃ powder. The shift in the positive direction (wide angle side) is presumed to mean that a cation having an ion radius smaller than that of the indium ion is replaced by a solid solution and the interstitial distance is shortened. The X-ray diffraction (XRD) peak position (pattern) of In ₂ O ₃ powder is disclosed in No. 06-0416 of the JCPDS (Joint Committee on Powder Diffraction Standards) database.
If the shift of the maximum peak position of the bixbite structure compound is less than 0.1 degree, the solid solution of other atoms in the bixbite structure compound becomes insufficient, and other crystal forms may be precipitated.
The shift of the peak position of the bixbite structure compound is preferably 0.05 degree or more, more preferably 0.1 degree or more, and particularly preferably 0.2 degree or more at the maximum peak position (2θ).

Here, the peak shift angle can be measured by analyzing an X-ray diffraction chart.
FIG. 1 is an X-ray diffraction chart of the target of the present invention produced in Example 1 described later, and shows that the shift of the maximum peak position of the bixbite structure compound was 0.4 degrees.

In the target of the present invention, it is preferable that the average diameter of Zn agglomerated parts observed with an electron beam microanalyzer (EPMA) is 50 μm or less.
If the average diameter of the Zn agglomerated part is more than 50 μm, the Zn agglomerated part becomes a stress concentration point, and the strength may be reduced, or an electric charge (charge) may occur and abnormal discharge may occur, which is not preferable.
The average diameter of the Zn agglomerated part is more preferably 30 μm or less, and further preferably 15 μm or less.
The area ratio of the Zn aggregate to the target cross-sectional area is usually 10% or less, preferably 5% or less, more preferably 1% or less.

The target of the present invention preferably has a Cr and Cd content of 10 ppm (mass) or less.
Cr and Cd are impurities in the target of the present invention. When the content exceeds 10 ppm (mass), it becomes a nucleus of another crystal type and there is a possibility that it is difficult to take a bixbite structure. In addition, when a film is formed and used in a liquid crystal display device, durability may be reduced or image sticking may easily occur.
Except for the Zn agglomerated portion, it is preferable that In, Sn, and Zn are substantially uniformly dispersed.
The content of Cr and Cd is more preferably 5 ppm or less, and particularly preferably 1 ppm or less.

In the target of the present invention, the contents of Fe, Si, Ti, and Cu are each preferably 10 ppm (mass) or less.
Fe, Si, Ti, and Cu are impurities in the target of the present invention. When the content exceeds 10 ppm (mass), other crystal types are likely to be generated, and it may be difficult to take a bixbite structure. is there.
The content of Fe, Si, Ti, and Cu is more preferably 5 ppm or less, and particularly preferably 1 ppm or less.
The content of the impurity element can be measured by inductively coupled plasma (ICP) emission spectrometry.
In addition, Mg, B and Ga are added within the range not impairing the effects of the present invention, the transmittance is improved, Al is added to improve heat resistance, and Zr is added to improve chemical resistance. Also good.

In the target of the present invention, the crystal grain size of the bixbite structure compound is preferably 20 μm or less.
When the crystal grain size of the bixbite structure compound exceeds 20 μm, the grain boundary becomes a stress concentration point, and the strength may be lowered, or the smoothness of the target surface may be easily impaired.
The crystal grain size of the bixbite structure compound is more preferably 8 μm or less, and particularly preferably 4 μm or less.
The crystal grain size of the bixbite structure compound can be measured by an electron beam microanalyzer (EPMA).

The target of the present invention preferably has a bulk resistance in the range of 0.2 to 100 mΩ · cm.
If the bulk resistance is less than 0.2 mΩ · cm, the resistance is lower than the deposited film and the scattered film may cause nodules. If the bulk resistance is more than 100 mΩ · cm, sputtering may not be stable.
The bulk resistance of the target of the present invention is more preferably in the range of 0.3 to 10 mΩ · cm, further preferably in the range of 0.4 to 6 mΩ · cm, and 0.4 to 4 mΩ · cm. It is particularly preferable that the value falls within the range.
The bulk resistance of the target of the present invention can be measured by the four probe method.

The target of the present invention preferably has a theoretical relative density of 90% or more. If the theoretical relative density of the target is less than 90%, the target may break during discharge.
The theoretical relative density of the target of the present invention is more preferably 94% or more, further preferably 95% or more, and particularly preferably 98% or more.

Here, the theoretical relative density of the target is obtained as follows.
_ZnO, density SnO 2, _In 2 _{O 3} having a specific gravity of each ^{5.66g / cm 3, 6.95g / cm} 3, as 7.12 g / cm ^3, which calculates the density from the ratio was measured by the Archimedes method The ratio is calculated as the theoretical relative density.

The bending strength of the target of the present invention is preferably 10 kg / mm ² or more, more preferably 11 kg / mm ² or more, and particularly preferably 12 kg / mm ² or more. The target is required to have a certain level of bending force because a load is applied during transportation and mounting of the target, and the target may be damaged. If the target is less than 10 kg / mm ² , it cannot be used as a target. There is a fear.
The bending strength of the target can be measured according to JIS R 1601.

(I-2) Method for Producing Sputtering Target The method for producing a sputtering target of the present invention (hereinafter sometimes referred to as the target producing method of the present invention) includes a compound of indium, tin, and zinc, which are raw materials of a sputtering target, and In. The atomic ratio represented by / (In + Sn + Zn) is in the range of greater than 0.6 and smaller than 0.75, and the atomic ratio represented by Sn / (In + Sn + Zn) is in the range of 0.11 to 0.23. Obtaining a blended mixture of
Pressure-molding the mixture to produce a molded body;
A step of raising the temperature of the molded body at 10 to 1000 ° C./hour;
Firing the molded body at a temperature of 1100 to 1700 ° C. to obtain a sintered body;
Cooling the sintered body at 10 to 1000 ° C./hour;
It is characterized by including.

Hereinafter, the target manufacturing method of this invention is demonstrated for every process.
(1) Compounding process The compounding process is an essential process for mixing a metal compound that is a raw material of the sputtering target.
As a raw material, it is preferable to use an indium compound powder having a particle size of 6 μm or less, a zinc compound powder, and a tin compound powder having a particle size smaller than the particle size of those powders. When the particle size of the tin compound powder is the same as or larger than the particle size of the indium compound powder and the zinc compound powder, SnO ₂ is present (remains) in the target, making it difficult to form a bixbite structure, This is because the bulk resistance of the target may be increased.
Further, the particle diameter of the tin compound powder is preferably smaller than the particle diameter of the indium compound powder and the zinc compound powder, and the particle diameter of the tin compound powder is more preferably half or less of the particle diameter of the indium compound powder. . In addition, it is particularly preferable that the zinc compound powder has a particle size smaller than that of the indium compound powder because a bixbite structure is easily generated.
Each metal compound used as a target raw material is preferably mixed and pulverized uniformly using an ordinary mixing and pulverizing machine such as a wet ball mill, a bead mill, or an ultrasonic device.

  An oxide of indium, tin, and zinc, which is a target raw material, has an atomic ratio represented by In / (In + Sn + Zn) within a range larger than 0.6 and smaller than 0.75, and Sn / (In + Sn + Zn). It is necessary to mix the expressed atomic ratio within the range of 0.11 to 0.23. If it is out of the above range, the target of the present invention having the above effects cannot be obtained.

Examples of the indium compound include indium oxide and indium hydroxide.
Examples of the tin compound include tin oxide and tin hydroxide.
Examples of the zinc compound include zinc oxide and zinc hydroxide.
As each compound, an oxide is preferable because it is easy to sinter and it is difficult to leave a by-product.
The purity of each raw material is usually 2N (99% by mass) or more, preferably 3N (99.9% by mass) or more, more preferably 4N (99.99% by mass) or more. If the purity is lower than 2N, heavy metals such as Cr and Cd may be included. If these heavy metals are included, the durability of the transparent conductive film produced using this target may be impaired. May be harmful.

When pulverizing the metal oxide that is the raw material for producing the target, the particle size of the pulverized metal oxide is usually 10 μm or less, preferably 3 μm or less, more preferably 1 μm or less, and even more preferably 0.1 μm or less. If the particle size of the metal oxide is too large, the target density may be difficult to increase.
The particle size after pulverization of the metal compound as the target raw material can be measured according to JIS R 1619.

(2) Calcination process A calcination process is a process provided as needed, after obtaining the mixture of an indium compound, a zinc compound, and a tin compound, and calcining this mixture.

  After obtaining a mixture of an indium compound, a zinc compound and a tin compound, this mixture is preferably calcined. However, in the case of a large target such as a liquid crystal panel application, the crystal form may not be stable. In such a case, it is preferable not to undergo a calcination step.

  In the calcination step, it is preferable to heat-treat the mixture of the metal compounds at 500 to 1,200 ° C. for 1 to 100 hours. This is because the thermal decomposition of the indium compound, the zinc compound, and the tin compound may be insufficient under heat treatment conditions of less than 500 ° C. or less than 1 hour. On the other hand, when the heat treatment condition exceeds 1,200 ° C. or exceeds 100 hours, grain coarsening may occur. Therefore, it is particularly preferable to perform heat treatment (calcination) in the temperature range of 800 to 1,200 ° C. for 2 to 50 hours.

The calcined product obtained here is preferably pulverized before being molded and sintered. The calcined product is preferably pulverized by using a ball mill, a roll mill, a pearl mill, a jet mill or the like so that the particle size becomes 0.01 to 1.0 μm.
The particle size of the calcined product can be measured according to the method described in JIS R 1619.

(3) Molding process The molding process is an essential process for pressure-molding a mixture of metal oxides (or a calcined product when the calcining process is provided) to form a compact. In the forming step, the obtained calcined product is used to form a shape suitable as a target. When the calcination step is provided, the obtained calcined fine powder can be granulated and then formed into a desired shape by press molding.

Examples of the molding process that can be used in this step include mold molding, cast molding, injection molding, and the like. In order to obtain a sintered body having a high sintering density, CIP (cold isostatic pressure) or the like can be used. After the molding, it is preferable to perform a sintering process described later.
In the molding process, molding aids such as polyvinyl alcohol, methylcellulose, polywax, and oleic acid may be used.

(4) Firing step The sintering step is an essential step of granulating the fine powder obtained in the molding step and then firing the compact formed into a desired shape by press molding. The firing step includes a step of increasing the temperature of the molded body obtained in the molding step within a range of 10 to 1,000 ° C./hour, and a temperature within the range of 1,100 to 1,700 ° C. And a step of obtaining a sintered body by firing at a step of cooling the obtained sintered body within a range of 10 to 1,000 ° C./hour.
Firing can be performed by hot isostatic pressure (HIP) firing or the like.

  The firing conditions are usually in the range of 1,100 to 1,700 ° C., preferably in the range of 1,260 to 1,640 ° C., more preferably in the range of 1,310 to 1,590 ° C., particularly preferably 1. In the range of 360 to 1,540 ° C., firing is preferably performed within a range of 30 minutes to 360 hours, preferably within a range of 8 to 180 hours, and more preferably within a range of 12 to 120 hours.

  Firing is preferably performed in an oxygen gas atmosphere or under an oxygen gas pressure. When the raw material powder mixture is fired in an atmosphere not containing oxygen gas, gas components such as oxygen may be desorbed from the raw material during the firing, and the composition may change. In addition, when fired at a temperature of 1,700 ° C. or higher, the formation of hexagonal layered compounds has priority, and there is a possibility that the formation of bixbite crystals may not be sufficient, or that some of the components may gasify and control of the composition ratio may be difficult. is there. On the other hand, when the temperature is lower than 1,100 ° C., the target crystal form is not generated, and the sintered density of the target is not increased, so that the resistance of the target is increased or the strength is decreased. On the other hand, if the sintering temperature is lower than 1,100 ° C., another crystal type with high resistance may be formed, the raw material composition may remain, or the relative density of the target may be reduced. If the sintering time is shorter than 30 minutes, the raw material composition may remain or the relative density of the target may be reduced.

  Moreover, the temperature increase rate of a molded object is usually in the range of 10 to 1,000 ° C./hour, preferably in the range of 20 to 600 ° C./hour, more preferably in the range of 30 to 300 ° C./hour. If it is faster than 1,000 ° C./hour, a hexagonal layered compound or the like is produced, and the bixbite structure compound may not be produced sufficiently. If it is slower than 10 ° C./hour, it takes too much time and the productivity may decrease.

The temperature drop rate of the sintered body is usually within the range of 10 to 1,000 ° C./hour, preferably within the range of 15 to 600 ° C./hour, more preferably 20 to 300 ° C./hour, and particularly preferably 30 to Within the range of 100 ° C./hour. If it is faster than 1,000 ° C./hour, a hexagonal layered compound is produced, and there is a possibility that the formation of the bixbite structure will not be sufficient and cracks may occur in the target. If it is slower than 10 ° C./hour, it takes too much time and the productivity may decrease.
Further, the temperature lowering rate is preferably slower than the temperature rising rate, more preferably 60% or less, and particularly preferably 40% or less. If the rate of temperature decrease is slower than the rate of temperature increase, the target can be manufactured in a relatively short manufacturing time.

(5) Reduction process A reduction process is a process provided as needed which performs a reduction process in order to equalize the bulk resistance of the sintered compact obtained at the above-mentioned calcination process as the whole target.
Examples of the reduction method that can be applied in this step include a method using a reducing gas, vacuum firing, or reduction using an inert gas.

  In the case of using a reducing gas, hydrogen, methane, carbon monoxide, a mixed gas of these gases and oxygen, or the like can be used.

  In the case of reduction by firing in an inert gas, nitrogen, argon, a mixed gas of these gases and oxygen, or the like can be used.

  The reduction temperature is 100 to 800 ° C, preferably 200 to 800 ° C. The reduction time is 0.01 to 10 hours, preferably 0.05 to 5 hours.

(6) Processing step The processing step is to cut the sintered body obtained by sintering as described above into a shape suitable for mounting on a sputtering apparatus, and to mount a jig such as a backing plate. It is the process provided as needed for attaching.

  The thickness of the target is usually 2 to 20 mm, preferably 3 to 12 mm, particularly preferably 4 to 6 mm. Also, a plurality of targets may be attached to one backing plate to form a substantially single target. Further, the surface is preferably finished with a 80 to 10000 diamond grindstone, and more preferably with a 100 to 4000 diamond grindstone. It is particularly preferable to perform finishing with a 200-1000 diamond grindstone. If a diamond grindstone smaller than No. 80 is used, the target may be easily broken.

  In order to produce the target of the present invention, it is preferable to use the above-described target production method of the present invention. Other steps are not particularly limited as long as the temperature, the temperature lowering rate, the sintering temperature, and the sintering time are used. For example, JP 2002-69544 A, JP 2004-359984 A, A known method disclosed in Japanese Patent No. 3628554 and the following method can also be employed. Moreover, you may use the manufacturing method which combined some of these methods.

Manufacturing method of industrial sputtering target (1)
(i) The weighed raw materials are wet-mixed and pulverized together with water and auxiliaries using a ball mill or bead mill.
(ii) The obtained raw material mixture is dried and granulated with a spray dryer or the like to produce a granulated powder.
(iii) The obtained granulated powder is press-molded and then SIP-molded with a rubber mold.
(iv) The obtained molded body is fired under oxygen pressure to obtain a fired body.
(v) The obtained fired body is cut with a diamond cutter, a water cutter or the like and then polished with a diamond grindstone or the like.
(vi) A wax agent such as italindium is applied and bonded to a backing plate made of copper or the like.
(vii) Backing plate polishing and target surface treatment for wax agent treatment, oxide layer removal, etc.

Industrial sputtering target manufacturing method (2)
(i) The weighed raw materials are dry mixed and pulverized with a ball mill or the like to produce granulated powder.
(ii) The obtained granulated powder is press-molded.
(iii) The obtained molded body is fired at atmospheric pressure to obtain a fired body.

Manufacturing method of industrial sputtering target (3)
(i) The weighed raw materials are dry mixed and pulverized with a ball mill or the like to produce granulated powder.
(ii) The obtained granulated powder is wet-mixed and pulverized with a ball mill, V blender or the like to obtain a granulated dispersion.
(iii) A molded body is obtained by casting from the obtained granulated dispersion.
(iv) The molded body obtained is brought into contact with air on the support and dried, and then fired at atmospheric pressure to obtain a fired body.

II. Transparent conductive film (II-1) Configuration of transparent conductive film The transparent conductive film of the present invention is formed by film-forming the sputtering target of the present invention by a sputtering method.

  The transparent conductive film of the present invention is preferably amorphous or microcrystalline, and particularly preferably amorphous. If it is crystalline, the etching rate during the production of the transparent electrode described later becomes slow, the residue remains after etching, or when the transparent electrode is produced, the taper angle of the electrode end does not fall within 30 to 89 degrees. There is a risk.

  The transparent conductive film of the present invention preferably has resistance to PAN (phosphoric acid, acetic acid, nitric acid mixed acid) which is a metal wiring etching solution. When the transparent conductive film has PAN resistance, the metal wiring can be etched without dissolving the transparent conductive film after forming the metal wiring on the transparent conductive film.

(II-2) Production Method of Transparent Conductive Film There are no particular restrictions on the sputtering method and sputtering conditions for producing the transparent conductive film of the present invention, but a direct current (DC) magnetron method, an alternating current (AC) magnetron method, a high frequency ( The RF) magnetron method is preferred. For liquid crystal (LCD) panel applications, the apparatus becomes large, so the DC magnetron method and the AC magnetron method are preferable, and the AC magnetron method capable of stable film formation is particularly preferable.

As sputtering conditions, the sputtering pressure is usually in the range of 0.05 to 2 Pa, preferably in the range of 0.1 to 1 Pa, more preferably in the range of 0.2 to 0.8 Pa, and the ultimate pressure is usually 10 ^−3. 10 ⁻⁷ Pa, preferably 5 × 10 ⁻⁴ to 10 ⁻⁶ Pa, more preferably 10 ⁻⁴ to 10 ⁻⁵ Pa, and substrate temperature is usually 25 to 500 ° C. Of these, preferably in the range of 50 to 300 ° C, more preferably in the range of 100 to 250 ° C.

  As the introduction gas, an inert gas such as Ne, Ar, Kr, or Xe can be used. Of these, AR is preferable because the film forming speed is high. In addition, in the case of Zn / Sn <1, it is preferable that 0.01 to 5% of oxygen is included in the introduced gas because the bulk resistance of the target is easily lowered. In the case of Zn / Sn> 2, it is preferable that 0.01 to 5% of hydrogen is included in the introduced gas because the resistance of the obtained transparent conductive film tends to decrease.

  The transparent conductive film of the present invention is excellent in conductivity, etching property, heat resistance and the like even if indium is reduced. Further, the transparent conductive film of the present invention can be etched with a phosphoric acid-based etchant that is an etchant for metal or alloy, and has an advantage that etching can be performed together with a metal or alloy. .

The specific resistance of the transparent conductive film of the present invention is preferably 1200 μΩ · cm or less, more preferably 900 μΩ · cm or less, and particularly preferably 600 μΩ · cm or less. When the specific resistance exceeds 1200 μΩ · cm, there is a disadvantage that the film thickness must be increased in order to reduce the resistance.
The specific resistance of the transparent conductive film can be measured by a four probe method.

The film thickness of the transparent conductive film of the present invention is usually in the range of 1 to 500 nm, preferably in the range of 10 to 240 nm, more preferably in the range of 20 to 190 nm, and particularly preferably in the range of 30 to 140 nm. When the film thickness is thicker than 500 nm, there is a possibility that it may be partially crystallized, the transmittance may be reduced, or the film formation time may be long. If it is thinner than 1 nm, it is likely to be affected by the substrate and the specific resistance may not be stable.
The film thickness of the transparent conductive film can be measured by a stylus method.

III. Structure of transparent electrode (III-1) transparent electrode The transparent electrode of the present invention is produced by etching the transparent conductive film of the present invention. Therefore, the transparent electrode of the present invention has the above characteristics of the transparent conductive film of the present invention.
In the transparent electrode of the present invention, the taper angle at the end of the electrode is preferably in the range of 30 to 89 degrees, more preferably in the range of 35 to 85 degrees, and particularly preferably in the range of 40 to 80 degrees. The taper angle of the electrode end can be measured by observing the cross section with an electron microscope (SEM).

When the taper angle of the electrode end is smaller than 30 degrees, the distance between the electrode edge portions becomes long, and when the liquid crystal panel or the organic EL panel is driven, there is a case where the contrast is different between the pixel peripheral portion and the inside. On the other hand, if it exceeds 89 degrees, electrode cracking or peeling at the edge portion may occur, which may cause alignment film failure or disconnection.
The transparent electrode of the present invention is particularly suitable for the case where it is provided on an organic film where it is difficult to adjust the taper angle because it is easy to adjust the taper angle of the electrode end.

(III-2) Method for Producing Transparent Electrode The method for producing a transparent electrode of the present invention comprises etching the transparent conductive film of the present invention with a 1 to 10% by mass oxalic acid-containing aqueous solution in a temperature range of 20 to 50 ° C. Features.
The oxalic acid content of the oxalic acid-containing aqueous solution is more preferably 1 to 5% by mass.
In the method for producing a transparent electrode of the present invention, it is preferable to produce a transparent electrode having a taper angle of 30 to 89 degrees at the electrode end.

  The etching rate in the case of etching the formed transparent conductive film with a 5% by mass aqueous oxalic acid solution at 35 ° C. is usually in the range of 10 to 500 nm / min, preferably in the range of 20 to 150 nm / min, particularly preferably. It is within the range of 30 to 100 nm / min. If it is slower than 10 nm / min, not only the production tact time will be slow, but also etching residues may remain on the resulting transparent electrode. If it is faster than 500 nm / min, it may be too early to control the line width and the like.

  Also, if the formed transparent conductive film has resistance to PAN (phosphoric acid, acetic acid, nitric acid mixed acid) which is a metal wiring etching solution, the transparent conductive film is dissolved after forming the metal wiring on the transparent conductive film. The metal wiring can be etched without any problem. The PAN resistance is preferably 20 nm / min or less, more preferably 10 nm / min or less, at an etching rate of PAN of 50 nm.

EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to these Examples at all.
Example 1
(1) Production of sputtering target As raw materials, purity 4N, indium oxide with an average particle size of 2 μm, purity 4N, zinc oxide with an average particle size of 0.6 μm, purity 4N, tin oxide with an average particle size of 0.5 μm, [ The atomic ratio represented by In / (In + Sn + Zn)] is 0.64, the atomic ratio represented by [Sn / (In + Sn + Zn)] is 0.18, and the atomic ratio represented by [Zn / (In + Sn + Zn)] is 0. The mixture was fed to a wet ball mill and mixed and ground for 20 hours to obtain a raw material fine powder.
After granulating the obtained raw material fine powder, it was press-molded into dimensions of 10 cm in diameter and 5 mm in thickness, charged in a firing furnace, and subjected to 48 hours at 1,400 ° C. under oxygen gas pressure. The sintered body (target) was obtained by firing under conditions. The temperature increase rate was 180 ° C./hour, and the temperature decrease rate was 60 ° C./hour.

(2) Evaluation of target The obtained target was measured for density, bulk resistance value, X-ray diffraction analysis, crystal grain size and various physical properties. As a result, the theoretical relative density was 96%, and the bulk resistance value measured by the four-probe method was 0.6 mΩ · cm.
Further, as a result of observing the crystal state in the transparent conductive material by X-ray diffraction method for the sample collected from this sintered body, only the bixbite structure compound was confirmed in the obtained target. In particular, a peak attributed to SnO ₂ or Sn ₃ In ₄ O ₁₂ could not be confirmed. FIG. 1 shows an X-ray diffraction chart of the target obtained.

Further, the obtained sintered body was embedded in a resin, and the surface thereof was polished with alumina particles having a particle diameter of 0.05 μm, and then the electron beam microanalyzer (EPMA) JXA-8621MX (manufactured by JEOL Ltd.) was used. The maximum diameter of the crystal particles observed within a 30 μm × 30 μm square frame on the surface of the sintered body magnified 5,000 times was measured. The average value of the maximum particle diameters measured in the same manner within three frames was calculated, and it was confirmed that the crystal grain size of the bixbite structure compound of this sintered body was 2.5 / μm.
As a result of elemental analysis of the target, the content of Cr and Cd was less than 1 ppm.

  Further, the sintered body obtained in (1) was cut to produce a sputtering target having a diameter of about 10 cm and a thickness of about 5 mm, and a transparent conductive film was formed by a sputtering method.

(3) Film formation of transparent conductive oxide (transparent conductive film) The sputtering target obtained in (2) above was mounted on a DC magnetron sputtering apparatus, and a transparent conductive film was formed on a glass substrate at room temperature. .
The sputtering conditions used here were a sputtering pressure of 1 × 10 ⁻¹ Pa, an ultimate pressure of 5 × 10 ⁻⁴ Pa, a substrate temperature of 200 ° C., an input power of 120 W, and a film formation time of 15 minutes.
As a result, a transparent conductive glass in which a transparent conductive oxide having a film thickness of about 100 nm was formed on the glass substrate was obtained.

(4) Evaluation of sputtering state
(i) Number of occurrences of abnormal discharge The sputtering target obtained in (1) was mounted on a DC magnetron sputtering apparatus, and a mixed gas in which 3% hydrogen gas was added to argon gas was used. Under the same conditions as above, sputtering was continued for 240 hours and the presence or absence of abnormal discharge was monitored, but it was never confirmed.

(ii) Number of nodules generated Sputtering was performed continuously for 8 hours under the same conditions as in (i) above. Subsequently, the surface of the target after sputtering was magnified 30 times with a stereomicroscope and observed. The number of nodules generated at 20 μm or more in a visual field of 900 mm ² was measured at any three points on the target, and the average value was obtained.

(5) Evaluation of physical properties of transparent conductive film Regarding the conductivity of the transparent conductive film on the transparent conductive glass obtained in (3) above, the specific resistance was measured by a four-probe method, and was 500 μΩ · cm.
The transparent conductive film was confirmed to be amorphous by X-ray diffraction analysis. On the other hand, the smoothness of the film surface was confirmed to be good because the PV value (based on JISB0601) was 5 nm.
Furthermore, regarding the transparency of this transparent conductive film, the light transmittance for light with a wavelength of 500 nm was 90% by a spectrophotometer, and the transparency was also excellent.

Furthermore, when this transparent conductive film was etched at 35 ° C. with 5 mass% oxalic acid, the etching rate was 80 nm / min.
Moreover, the etching rate by PAN (a mixed acid of 3.3% by mass of nitric acid, 91.4% by mass of phosphoric acid, and 10.4% by mass of acetic acid) which is a typical phosphoric acid-based metal wiring etching solution is 20 nm / 50 ° C. The PAN resistance was good.
In Table 1, the PAN resistance evaluation is represented by “◯” when 50 ° C. and 20 nm / min or less, and by “X” when exceeding 50 ° C. and 20 nm / min.

The measurement conditions for X-ray diffraction measurement (XRD) were as follows.
Device: Rigaku Ultima-III
X-ray: Cu-Kα ray (wavelength 1.5406mm, monochromatized with graphite monochromator)
2θ-θ reflection method, continuous scan (1.0 ° / min)
Sampling interval: 0.02 °
Slit DS, SS: 2/3 °, RS: 0.6 mm

Examples 2, 3 and Comparative Examples 1-3
A sputtering target and a transparent conductive film were prepared and evaluated in the same manner as in Example 1 except that the composition ratio of the raw materials was adjusted to the atomic ratio as shown in Table 1. However, in Comparative Example 1, RF magnetron sputtering was used. The evaluation results are shown in Table 1.

Example 4
A large target substantially composed of a bixbite structure compound having the same composition as in Example 1 was manufactured, and an electrode of a liquid crystal display for television was formed on the organic film by DC magnetron sputtering and oxalic acid etching. When the lighting test of the panel produced using this electrode was conducted, performance comparable to that using ITO was obtained.
Also, no troubles such as burn-in occurred even after 10,000 hours of continuous lighting.

According to the present invention, it is possible to suppress abnormal discharge generated when a transparent conductive film is formed using a sputtering method and perform stable sputtering, the indium content is reduced, the resistance is low, and the theoretical relative A sputtering target having high density and high strength can be obtained.
By using the sputtering target of the present invention, it is possible to obtain a transparent conductive film and a transparent electrode which are free from nodules, have a low specific resistance, have an appropriate oxalic acid etching rate, and have PAN resistance.
The transparent electrode of the present invention is particularly useful for an active matrix display device that requires fine processing of the electrode.
In addition, since the target of the present invention can perform sputtering stably, it can be applied to film formation of a transparent oxide semiconductor typified by a TFT (Thin Film Transistor) by adjusting film formation conditions.

  The transparent conductive film according to the present invention is useful as a component constituting various display devices.

2 is a chart showing an X-ray diffraction chart of a target obtained in Example 1. FIG.

Claims (10)

A sputtering target comprising indium, tin, zinc and oxygen, wherein only a peak of a bixbite structure compound is substantially observed by X-ray diffraction (XRD). The sputtering target according to claim 1, wherein the bixbite structure compound is represented by In ₂ O ₃ .   The atomic ratio represented by In / (In + Sn + Zn) is a value within a range larger than 0.6 and smaller than 0.75, and the atomic ratio represented by Sn / (In + Sn + Zn) is 0.11 to 0.23. The sputtering target according to claim 1, wherein the sputtering target is a value within the range of 1. The peak in X-ray diffraction (XRD) is characterized in that the maximum peak position of the bixbite structure compound is shifted in the plus direction (wide angle side) with respect to that of the In ₂ O ₃ single crystal powder. The sputtering target as described in any one of 1-3.   The sputtering target according to any one of claims 1 to 4, wherein the average diameter of Zn aggregates observed with an electron beam microanalyzer (EPMA) is 50 µm or less.   The content of Cr and Cd is 10 ppm (mass) or less, respectively, The sputtering target as described in any one of Claims 1-5 characterized by the above-mentioned.   The contents of Fe, Si, Ti, and Cu are each 10 ppm (mass) or less, The sputtering target as described in any one of Claims 1-6 characterized by the above-mentioned.   8. The sputtering target according to claim 1, wherein the crystal grain size of the bixbite structure compound is 20 μm or less.   The sputtering target according to any one of claims 1 to 8, wherein a bulk resistance is in a range of 0.2 to 100 mΩ · cm. The sputtering target according to any one of claims 1 to 9, wherein a theoretical relative density is 90% or more.

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