JPH0812494A - Production of oxide crystal thin film and thin-film element - Google Patents

Abstract

PURPOSE:To provide a method for producing an oxide crystal thin film having excellent ferroelectricity by which a buffer layer for preparing a c-axis oriented Bi4Ti3O12 thin film is formed on a silicon substrate with good reproducibility and produce a thin-film element. CONSTITUTION:This method for producing an oxide crystal thin film comprises forming a buffer layer 3 comprising a bismuth silicate thin film on a silicon substrate 2, then forming an oxide ferroelectric thin film Bi4Ti3O12 4 on the buffer layer. Thereby, the c-axis oriented film of the Bi4Ti3O12 can be formed with good reproducibility and a device utilizing an extremely small coercive electric field in the c-axis direction and great spontaneous polarization can be developed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an oxide crystal thin film and a thin film element, and more particularly to a method of manufacturing an oxide crystal thin film used for a ferroelectric nonvolatile memory element, a pyroelectric element, a piezoelectric element and the like. Regarding thin film devices.

[0002]

2. Description of the Prior Art Among many oxide crystalline materials, BaT
There are various materials having various functions such as ferroelectricity, high dielectricity, piezoelectricity, pyroelectricity, electro-optic effect, etc., including iO ₃ , PZT, LiNbO _{3 and the} like. Therefore, many devices utilizing these effects, such as capacitors, pressure sensors, infrared sensors, ultrasonic oscillators, frequency filters, and optical switches, have been developed using these materials. In particular, recently, by utilizing the high dielectric constant characteristics and spontaneous polarization of ferroelectric materials, miniaturization of devices, simplification of processes, development of new functional devices such as non-volatile memory through application to semiconductor devices such as DRAM. Has been done.

The oxide ferroelectric substance Bi ₄ Ti ₃ O ₁₂ is a ferroelectric substance having a layered perovskite structure belonging to the orthorhombic system. The spontaneous polarization has components in two directions of the a-axis and the c-axis, the spontaneous polarization in the a-axis direction is about 50 μC / cm ² , the coercive electric field is about 50 kV / cm, and the spontaneous polarization in the c-axis direction is about 4 μC / cm ² .
cm ² , and the coercive electric field is about 5 kV / cm. In particular, since it has a small coercive electric field in the c-axis direction, SHU YAU W
U, IEEE Trans. Electron. Dev
According to ices ED-21, 499 (1974) and the like, application to a ferroelectric non-volatile memory capable of low voltage driving is expected. For example, as a gate insulating film of a MOS type field effect transistor (FET), Bi ₄ Ti _{3 is used.}
By utilizing the fact that the source-drain current difference depends on the direction of the spontaneous polarization of the film by using the O ₁₂ crystal thin film, the direction of the spontaneous polarization maintained even when the power is off is read out as information. Therefore, a ferroelectric nonvolatile memory device can be realized. In this case, in order to realize low voltage driving, a ferroelectric thin film with a coercive field as small as possible is desirable, and Bi ₄ Ti ₃ O _{12 with} c-axis orientation is desirable.
Crystal thin films are promising. Further, in such a device structure, by utilizing the pyroelectric effect of the ferroelectric film to detect the change in the source-drain current according to the temperature change in the spontaneous polarization value due to infrared irradiation, the infrared sensor It can be applied. Bi ₄ Ti ₃ O ₁₂ thin film fabrication has hitherto been carried out by a sputtering method, a sol-gel method, a laser ablation method, a MOCVD method or the like.

[0004]

The above-mentioned FET
In order to apply to various devices such as a non-volatile memory, it is indispensable to develop a direct film formation technology of an oxide thin film with controlled orientation on the surface of a silicon substrate. Since itself is a material that is extremely susceptible to oxidation, generation of amorphous silicon oxide on the surface of the silicon substrate when forming the ferroelectric thin film poses a problem. On such an amorphous substrate, the crystal orientation of the ferroelectric thin film formed thereon is natural orientation, and it is difficult to obtain an orientation film having the most effective spontaneous polarization direction. Therefore, when a ferroelectric thin film is formed on a silicon substrate, how to suppress the generation of amorphous silicon oxide and control the orientation of the ferroelectric thin film thereon is a problem.

A hetero-growth technique for a ferroelectric thin film whose orientation on a silicon substrate is controlled has not been sufficiently established despite its importance in terms of application. When a Bi ₄ Ti ₃ O ₁₂ thin film is formed directly on a silicon substrate, interdiffusion of Si, Bi, Ti, and O occurs at the interface with the silicon substrate, and an amorphous silicon oxide layer is generated. In this case, B
The crystal orientation of the i ₄ Ti ₃ O ₁₂ thin film only depends on the natural orientation, and it is difficult to control the orientation. Therefore, Bi ₄ T
In order to produce a c-axis oriented film of i ₃ O ₁₂ with good reproducibility,
The problem is to suppress the mutual diffusion between the oxide thin film and the silicon substrate and the generation of the amorphous layer. In order to solve this problem, it has been attempted to insert a buffer layer between the oxide thin film and the silicon substrate, for example, spinel MgAl ₂ O ₄
(100) / Si (100) and the like are known. In this case, it is an important problem that the buffer layer itself lattice-matches the silicon substrate and the intended oxide crystal material. The present invention has been made in order to solve the above-mentioned problems, and c-axis oriented Bi ₄ Ti on a silicon substrate is used.
It is an object to provide a buffer layer for producing a ₃ O ₁₂ thin film with good reproducibility, a method for producing an oxide crystal thin film having excellent ferroelectricity, and a thin film element.

[0006]

According to the present invention, the above-mentioned object is to form a buffer layer made of a bismuth silicate thin film on a silicon substrate, and to form an oxide ferroelectric thin film Bi ₄ Ti ₃ on the buffer layer. This is achieved by the method for producing an oxide crystal thin film according to claim 1, which forms O ₁₂ .

According to the present invention, the aforementioned object is to form a buffer layer composed of the bismuth silicate thin film,
3. The method for producing an oxide crystal thin film according to claim 2, wherein the organometallic material containing Bi is vaporized by heating, and the vaporized organometallic material containing Bi is supplied onto a silicon substrate together with a carrier gas and an O ₂ gas. .

According to the present invention, the above objects are achieved by a silicon substrate, a bismuth silicate thin film buffer layer formed on the silicon substrate, and an oxide ferroelectric thin film formed on the bismuth silicate thin film buffer layer. Bi ₄ T
The thin film element according to claim 3, comprising i ₃ O ₁₂ , an upper electrode formed on the oxide ferroelectric thin film, and a lower electrode formed on the back surface of the silicon substrate.

[0009]

According to the method for producing an oxide crystal thin film of claim 1, a high quality ferroelectric crystal having a c-axis orientation of Bi ₄ Ti ₃ O ₁₂ on a silicon substrate through a buffer layer made of a bismuth silicate thin film. A thin film can be formed, Bi ₄ Ti ₃ O ₁₂
It can be applied to various electronic devices that efficiently utilize the excellent ferroelectric characteristics in the c-axis direction. For example, it is possible to develop a field-effect nonvolatile memory, a two-dimensional infrared array sensor, or the like by adding spontaneous polarization and pyroelectric characteristics of a ferroelectric substance to a semiconductor device using a silicon substrate.

According to the thin film element of claim 3, a high quality ferroelectric crystal thin film having a c-axis orientation of Bi ₄ Ti ₃ O ₁₂ can be formed on a silicon substrate via a buffer layer made of a bismuth silicate thin film. It is possible to apply Bi ₄ Ti ₃ O ₁₂ to various electronic devices that efficiently utilize the excellent ferroelectric properties in the c-axis direction.

[0011]

The first embodiment of the method for producing an oxide crystal thin film and the thin film element of the present invention will be described below with reference to the drawings. In this example, Bi ₄ T with c-axis orientation is formed on a silicon substrate.
It is an object of the present invention to provide a method for producing an oxide crystal thin film having a buffer layer for producing an i ₃ O ₁₂ thin film with good reproducibility and a thin film element.

As shown in FIG. 1, the thin film element of this embodiment comprises a lower electrode 1, a silicon substrate 2, and a silicon substrate 2.
A buffer layer 3 formed of a bismuth silicate thin film formed above, and a bismuth silicate thin film buffer layer 3
Bi ₄ Ti ₃ O ₁₂ oxide ferroelectric thin film 4 formed on top
And an upper electrode 5. The constituent elements Bi, Si, and O of the bismuth silicate thin film 3 are S of the substrate.
It is also a constituent element of i and Bi ₄ Ti ₃ O ₁₂ , and is advantageous in that it does not contain impurities that affect the film characteristics.

The bismuth silicate thin film 3 has a plurality of crystal phases depending on the composition. The buffer layer of the present invention includes (1) Bi ₂ SiO ₅ : (JCPDS data 36-2
87) Orthorhombic system Lattice constant a = 15.217Å, b =
5.477Å, c = 5.325Å (2) Bi ₁₂ SiO ₂₀ : (JCPDS data 37-4
85) Cubic system One of two types of lattice constant a = 10.1067Å is used.

On the other hand, the crystal structure of silicon is: Si: (JCPDS data 5-565) cubic lattice constant a = 5.4301Å and the oxide ferroelectric thin film Bi ₄ Ti ₃ O _{12 has} a crystal structure of Bi ₄ Ti ₃ O _12: (JCPDS data 35-79
5) Orthorhombic system lattice constant a = 5.4100Å, b = 5.
It is 4489Å and c = 32.815Å. Therefore, the value of the crystal lattice mismatch of each material is estimated as follows. Bi ₄ Ti ₃ O ₁₂ (c-face) / Bi ₂ SiO ₅ (a-face) about 0.5% Bi ₄ Ti ₃ O ₁₂ (c-face) / Bi ₁₂ SiO ₂₀ (a-face) about 7.4% Bi ₂ SiO ₅ (a-plane) / Si (a-plane) about -0.5% Bi ₁₂ SiO ₂₀ (a-plane) / Si (a-plane) about -6.9% From the value of the lattice mismatch of more than, Bi ₄ Ti ₃ O ₁₂ (c surface) / Bi ₂ SiO ₅ (a surface) /
Si (a surface) Bi ₄ Ti ₃ O ₁₂ (c surface) / Bi ₁₂ SiO ₂₀ (a surface) /
It is considered that the epitaxial crystal growth of Si (a plane) or the formation of the orientation film is sufficiently possible. Therefore, Bi ₂ can be directly deposited on the Si substrate.
If an alignment film of SiO ₅ or Bi ₁₂ SiO ₂₀ can be formed, the c of the desired ferroelectric substance Bi ₄ Ti ₃ O ₁₂ can be formed.
The axial alignment film can be prepared sufficiently.

The silicon substrate used in the present invention is preferably a P type or N type low resistance substrate in the (100) plane. The oxide crystal thin film can be formed by various methods such as a sputtering method, a sol-gel method, a laser ablation method, and a MOCVD method, and the MOCVD method is preferable. Bi ₄ Ti ₃ O ₁₂ , Bi ₂ SiO ₅ and Bi ₁₂ Si
When the O ₂₀ thin film is formed by MOCVD, an organometallic compound of these constituent elements can be used as a raw material. For example, triphenylbismuth Bi (C ₆ H ₅ )
_3, ortho-tolyl bismuth _{Bi (o-C 7 H 8} ) 3, titanium isopropoxide _{Ti (i-OC 3 H 7} ) 4 or the like is used. These organometallic materials are heated and vaporized, and Ar
It is supplied onto a substrate heated and held with a carrier gas such as. At this time, O ₂ gas is simultaneously supplied as a reaction gas. The film forming parameters include the heating temperature of the raw material, the carrier gas flow rate, the O ₂ gas flow rate, the film forming pressure, the substrate temperature and the like.

To form a Bi ₂ SiO ₅ or Bi ₁₂ SiO ₂₀ thin film on a silicon substrate, the substrate temperature is 550 to 550.
The film forming pressure is preferably 650 ° C. and 10 to 100 Torr. On the other hand, in order to form Bi ₄ Ti ₃ O ₁₂ , the substrate temperature is preferably 550 to 650 ° C., and the film forming pressure is preferably 1 to 10 Torr. In addition, these two types of thin films have the same CVD
It is advantageous in that it can be continuously formed in the apparatus.

Further, Pt and RuO are formed on Bi ₄ Ti ₃ O ₁₂ on the formed bismuth silicate thin film buffer layer 3.
_2. By forming the upper electrode 5 of gold black or the like, it can be applied to many devices such as a ferroelectric nonvolatile memory element, a pyroelectric infrared sensor element, a piezoelectric element, and an optical modulator.

In this embodiment, a vertical MOCVD apparatus was used. A raw material gas is supplied from a nozzle installed above a silicon substrate on a substrate heating holder placed horizontally in a vertical film forming chamber. Bi raw materials include triphenyl bismuth Bi (C ₆ H ₅ ) ₃ and orthotolyl bismuth Bi
_{(O-C 7 H 8)} 3, Ti raw material as titanium isopropoxide _{Ti (i-OC 3 H 7} ) 4, the carrier gas is Ar, the reaction gas was used O _2. Then, a bismuth silicate thin film was grown under the following film forming conditions.

Substrate: P-type silicon (100) surface, specific resistance <0.2 Ωcm Substrate temperature: 550 ° C., 600 ° C., 650 ° C. Bi raw material: Bi (o-C ₇ H ₈ ) ₃ temperature 160 ° C., carrier gas Ar flow rate 200 sccm Reaction gas: O ₂ , flow rate 400 sccm Balance gas: Ar, flow rate 200 sccm Film formation pressure: 5, 50 Torr Silicon oxide film on the surface of silicon (100) substrate was removed by HF aqueous solution and washed with pure water. After being set on the substrate holder, the film forming chamber was quickly evacuated to 1 × 10 ⁻⁷ Torr. After that, Ar gas was flowed at a total flow rate of 800 sccm to set a predetermined film forming pressure and substrate temperature. Then, film formation was performed for 10, 20, 30, and 40 minutes under the above-mentioned film formation conditions, the temperature was gradually cooled to room temperature, and the substrate was taken out. The thin film surface shows a blue interference color and the following results are obtained from the X-ray diffraction pattern. The film forming temperature is 55 when the film forming pressure is 5 Torr.
When the temperature is 0 ° C., Bi ₂ SiO ₅ (a-axis orientation) occurs, and when the film forming pressure is 5 Torr and the film forming temperature is 600 ° C., Bi ₂ SiO ₅ (a axis orientation) as shown in FIG. 2 occurs. . When the film forming pressure is 5 Torr and the film forming temperature is 650 ° C., the film becomes amorphous. Further, the film forming temperature is 55 at a film forming pressure of 50 Torr.
When the temperature is 0 ° C., Bi ₂ O ₃ (non-oriented) is generated, and when the film forming pressure is 50 Torr and the film forming temperature is 600 ° C., Bi ₂ O ₃ is generated.
When (non-orientation) occurs and the film forming pressure is 50 Torr and the film forming temperature is 650 ° C., Bi ₁₂ SiO as shown in FIG.
₂₀ (a-axis orientation) occurs.

Here, when the growth pressure becomes high, Bi ₂ O ₃
It is thought that the gas phase reaction between the Bi raw material and the O ₂ gas is likely to occur. However, as the substrate temperature rises, the reaction on the substrate surface is accelerated, resulting in Bi ₁₂ SiO 2.
_It is thought that ₂₀ were formed. On the other hand, when the growth time is longer than 30 minutes, the generation of Bi ₂ O ₃ becomes remarkable. This is because Si is supplied from the Si substrate in the growth process of the bismuth silicate crystal thin film, and when the Si film is grown to a certain thickness, the Si from the underlying Si substrate is grown.
It is considered that Bi ₂ O ₃ grows as the growth time increases because the supply becomes difficult. From the above results, the growth pressure should be 5 to produce the Bi ₂ SiO ₅ thin film.
The substrate temperature may be set to about Torr and 600 ° C. or lower.
Further, in order to form the Bi ₁₂ SiO ₂₀ thin film, the growth pressure may be about 50 Torr and the substrate temperature may be 650 ° C. or higher. Furthermore, the growth time is preferably within 30 minutes.

Next, the Bi ₂ SiO film formed as described above is formed.
₅ Oxide ferroelectric crystal thin film Bi ₄ on the thin film (a-axis orientation)
A method of forming Ti ₃ O ₁₂ will be described.

The growth pressure is about 5 Torr and the substrate temperature is about 6
Bi ₂ SiO _{5 formed} by film formation at 00 ° C. for 10 minutes
Bi ₄ Ti ₃ O ₁₂ was continuously formed on the thin film under the following film forming conditions.
Was formed.

Base plate: Bi ₂ SiO ₅ (a-axis orientation) /
Si substrate a substrate temperature: 600 ° C. Bi _{material: Bi (o-C 7 H} 8) 3 Temperature 160 ° C., carrier gas Ar flow rate 200 sccm Ti _{material: Ti (i-OC 3 H} 7) 4 temperature 50 ° C., carrier gas flow rate of Ar 100sccm reaction gas: O _2, flow rate 400sccm balance gas: Ar, flow rate 100sccm film formation pressure: 5 Torr Bi ₂ after deposition of the SiO ₅ film, and stopping the introduction into the deposition chamber the raw material gas and O ₂ gas, 10 After evacuation of the film forming chamber for a minute, the raw material gas is introduced under the above film forming conditions, and Bi ₄
The film formation of Ti ₃ O ₁₂ is started. The above film forming conditions are Bi
It was determined in advance so as to obtain the stoichiometric composition of ₄ Ti ₃ O ₁₂ . The film formation time was 60 minutes, and a thin film having a film thickness of about 200 nm was obtained. The film surface morphology and the crystal orientation were evaluated by the X-ray diffraction method.
When observed with an electron microscope (SEM), the thin film was formed of plate-shaped crystal grains. In the X-ray diffraction pattern of this thin film, as shown in FIG. 4, only (00l) reflection of Bi ₄ Ti ₃ O ₁₂ was observed in addition to the reflection from Bi ₂ SiO ₅ , and a c-axis alignment film was formed. I understand that. With respect to the Bi ₄ Ti ₃ O ₁₂ thin film sample thus produced, Pt having an area of 100 μm square was vapor-deposited as the upper electrode 5, and Pt was vapor-deposited as the lower electrode 1 also on the back surface of the silicon substrate. When the ferroelectric hysteresis curve was measured for this thin film capacitor structure, as shown in FIG.
Remanent polarization is about 2.8 μC / cm ² , coercive electric field is 20 kV /
cm was obtained. Created c-axis oriented Bi ₄ Ti ₃ O
The coercive electric field of the ₁₂ thin films is very small, and the remanent polarization is also a value sufficient to realize a field effect nonvolatile memory. As described above, since the c-axis oriented film of Bi ₄ Ti ₃ O ₁₂ can be obtained by interposing the thin buffer layer on the silicon substrate, it is possible to obtain the pyroelectric effect including the field effect type ferroelectric nonvolatile memory. It is also possible to apply to infrared sensors using.

Next, a second embodiment of the present invention will be described. In this example, Bi ₄ with c-axis orientation is formed on a silicon substrate.
An object of the present invention is to provide a method for producing an oxide crystal thin film having a buffer layer for producing a Ti ₃ O ₁₂ thin film with good reproducibility and a thin film element.

Although Bi ₂ SiO ₅ is used for the bismuth silicate thin film buffer layer 3 in the first embodiment, the present invention is not limited to this, and a Bi ₁₂ SiO ₂₀ thin film may be formed on a silicon substrate. The film forming conditions other than the substrate were the same as in Example 1 described above, the substrate temperature was 650 ° C., and the film forming pressure was 5
A Bi ₁₂ SiO ₂₀ thin film was formed by forming the film at 0 Torr for 10 minutes. Bi ₄ Ti ₃ O ₁₂ was formed on this thin film under the same film forming conditions as in Example 1 above. Film formation time is 60
In a minute, a thin film having a thickness of about 200 nm was obtained. The X-ray diffraction pattern of this thin film is as shown in FIG. 6, and it is clear that the c-axis oriented film of Bi ₄ Ti ₃ O ₁₂ is clearly formed. When an electrode was formed on this thin film in the same manner as described above and a hysteresis curve was measured, as shown in FIG. 7, the remanent polarization was about 2.5 μC / cm ² , and the coercive electric field was about 3
A value of 0 kV / cm was obtained.

The applicant also prepared Bi ₄ Ti ₃ O ₁₂ on a silicon substrate on which a bismuth silicate thin film buffer layer was not formed, for comparison. Similar to the first embodiment, after removing the oxide film on the surface of the silicon (100) substrate, it is set in the MOCVD apparatus. The film forming conditions are the same as the Bi ₄ Ti ₃ O ₁₂ thin film forming conditions described above. 6
After the deposition of 10 minutes, the measurement results of X-ray diffraction pattern of the obtained thin film, as shown in FIG. 8, Bi ₄ Ti ₃
In addition to the O ₁₂ diffraction peak, the Bichromium phase Bi ₂ Ti ₂ O ₇
Mixing of diffraction peaks is observed. In addition, Bi ₄ Ti ₃
Regarding the orientation of O ₁₂ , many diffraction peaks other than the c-axis orientation are recognized, and the orientation is insufficient. Regarding the electrical characteristics of the formed thin film, when an electrode structure similar to that described above was formed and a hysteresis curve was measured, as shown in FIG. 9, it was found to be more satisfactory than that of Bi ₄ Ti ₃ O _{12 formed} in Example 1 above. No hysteresis curve was obtained. This is because the Bi ₄ Ti ₃ O ₁₂ thin film has insufficient c-axis orientation and, moreover, the diffusion of Ti into the silicon substrate facilitates the generation of an interface-altered layer. Seem. Therefore, it was sufficiently confirmed that the bismuth silicate thin film buffer layer had an effect as a diffusion barrier between the Si substrate and the Bi ₄ Ti ₃ O ₁₂ thin film.

In the above embodiment, Bi ₄ Ti is used.
_{Although the} MOCVD method was used as the film forming method of ₃ O ₁₂ , Si having a bismuth silicate thin film buffer layer formed on the surface was used.
If a substrate is used, another film forming method, for example, a sol-gel method,
A sputtering method, a laser ablation method, a reactive vapor deposition method, a plasma MOCVD method or the like may be used.

[0028]

According to the method of manufacturing an oxide crystal thin film of claim 1, the oxide ferroelectric thin film Bi ₄ Ti is formed on the silicon substrate via the buffer layer made of the bismuth silicate thin film.
_Since the c-axis orientation of ₃ O ₁₂ is formed, the c-axis oriented film of Bi ₄ Ti ₃ O ₁₂ can be formed with good reproducibility, and a device utilizing an extremely small coercive electric field in the c-axis direction and a large spontaneous polarization will be developed. be able to. MOS type FET using silicon
It can be applied to the development of ferroelectric non-volatile memory that utilizes the difference in drain current due to the difference in the direction of spontaneous polarization. It can also be applied as an infrared sensor that utilizes the pyroelectric effect, and creates a sensor device that detects infrared light as a change in drain current due to infrared irradiation, creates a two-dimensional infrared sensor in which it is two-dimensionally arranged, The detection current can be amplified by forming a transistor on the silicon substrate of the material.

According to the thin film element of claim 3, a high quality ferroelectric crystal thin film having a c-axis orientation of Bi ₄ Ti ₃ O ₁₂ can be formed on a silicon substrate through a buffer layer made of a bismuth silicate thin film. It is possible to apply Bi ₄ Ti ₃ O ₁₂ to various electronic devices that efficiently utilize the excellent ferroelectric properties in the c-axis direction.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a thin film element according to the present invention.

FIG. 2 is a diagram showing an X-ray diffraction pattern of a Bi ₂ SiO ₅ thin film according to the first example of the present invention.

FIG. 3 is a diagram showing an X-ray diffraction pattern of a Bi ₁₂ SiO ₂₀ thin film according to the first example of the present invention.

FIG. 4 Bi ₄ Ti ₃ O _{12 according} to the first embodiment of the present invention.
It is a figure which shows the X-ray-diffraction pattern of a thin film.

FIG. 5 shows Bi ₄ Ti ₃ O _{12 according} to the first embodiment of the present invention.
It is a figure which shows the hysteresis curve of a thin film.

FIG. 6 is a Bi ₄ Ti ₃ O _{12 according} to a second embodiment of the present invention.
It is a figure which shows the X-ray-diffraction pattern of a thin film.

FIG. 7 shows Bi ₄ Ti ₃ O _{12 according} to the second embodiment of the present invention.
It is a figure which shows the hysteresis curve of a thin film.

FIG. 8: Bi ₄ Ti ₃ O ₁₂ formed on a silicon substrate on which a bismuth silicate thin film buffer layer is not formed.
It is a figure which shows the X-ray-diffraction pattern of a thin film.

FIG. 9 is a Bi ₄ Ti ₃ O ₁₂ film formed on a silicon substrate on which a bismuth silicate thin film buffer layer is not formed.
It is a figure which shows the hysteresis curve of a thin film.

[Explanation of symbols]

1 Lower electrode 2 Silicon substrate 3 Bismuth silicate thin film buffer layer 4 Bi ₄ Ti ₃ O ₁₂ Oxide ferroelectric thin film 5 Upper electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location H01L 27/108 21/8247 29/788 29/792 37/02 41/08 41/22 H01L 41 / 08 Z 41/22 Z

Claims (3)

[Claims] 1. A method for producing an oxide crystal thin film, comprising forming a buffer layer made of a bismuth silicate thin film on a silicon substrate, and forming an oxide ferroelectric thin film Bi ₄ Ti ₃ O ₁₂ on the buffer layer. 2. When forming the buffer layer comprising the bismuth silicate thin film, the organometallic material containing Bi is vaporized by heating, and the vaporized organometallic material containing Bi is deposited on a silicon substrate together with a carrier gas and O ₂ gas. The method for producing an oxide crystal thin film according to claim 1, wherein 3. A silicon substrate, a bismuth silicate thin film buffer layer formed on the silicon substrate, an oxide ferroelectric thin film Bi ₄ Ti ₃ O ₁₂ formed on the bismuth silicate thin film buffer layer, and A thin film element comprising an upper electrode formed on an oxide ferroelectric thin film and a lower electrode formed on the back surface of the silicon substrate.