JPH064520B2 - Manufacturing method of oxide thin film - Google Patents

Description

The present invention relates to a method for producing an oxide thin film. More specifically, it relates to a method for producing an oxide thin film useful as an insulating film, a protective film, a sensor material, etc. on the surface of various substrates such as semiconductor elements, metal materials, and plastic materials.

(B) Conventional Technology In the field of the semiconductor industry and the like, conventionally, various methods for producing a crystalline metal oxide thin film have been known. As a typical method among these methods, a sputtering method using a metal oxide prepared in advance as a target, or a thermal CV for reacting by introducing heated vaporized metal vapor into an oxygen gas atmosphere
There is a D (chemical vapor deposition) method.

However, in the vapor thermal CVD method, in order to form a crystalline thin film, the substrate is heated to a high temperature (usually 500 to 8).
However, the material of the substrate is limited, and impurities are easily mixed in.
Further, in the sputtering method, it is difficult to control the oxide composition, and it is difficult to obtain a multi-component metal oxide crystal as intended.

As a method of obtaining a multi-component metal oxide thin film, a method of applying a solution of a metal alkoxide on a substrate and then hydrolyzing, drying and heat-treating the solution is known. However, most of the oxide films obtained in this case are amorphous, and in order to obtain a crystalline oxide film, heat treatment at a higher temperature is required, and at this time, crystal grain growth occurs. There is a drawback that pinholes are easily generated in the film.

(C) Object of the invention The present invention has been made in view of the above-mentioned conventional problems, and a crystalline metal oxide thin film having no pinhole can be obtained without raising the substrate temperature to a high temperature, and a multi-component An object of the present invention is to provide a method for producing an oxide thin film, which can easily control the system.

(D) Structure of the Invention Thus, according to the present invention, a pyrolysis gas of an organometallic chelate compound having a metal alkoxide and / or oxygen as a ligand is introduced into an oxygen gas atmosphere capable of generating plasma, and plasma is generated there. Is produced to form a crystalline metal oxide thin film on the surface of a substrate placed in the atmosphere, and a method for producing an oxide thin film is provided.

The present invention is a method of forming a metal oxide film on a substrate by plasma CVD in an oxygen atmosphere, and in that case, the most point is that an organic metal compound, particularly a metal alkoxide or an oxygen-containing organometallic chelate compound is used as a raw material. This is a major feature. By using such an organometallic compound as a raw material and thermally decomposing it, it becomes possible to form a uniform crystalline metal oxide thin film on a substrate at a low temperature of room temperature to about 200 ° C. The composition of the metal oxide can be easily controlled.

Specific examples of the metal alkoxide as the raw material of this invention include Si (OCH ₃ ) ₄ , Si (OC ₂ H ₅ ) ₄ , Ti (OC ₃ H ₇ ) ₄ , V (OC ₂ H ₅ ) ₃ ,
_{Al (OC 3 H 7) 3} , Co (OC 2 H 5) 2, Ni (OC 2 H 5) 2, Fe (OC 2 H 5) 3 and the like, of course Other metal alkoxide may be used is there. On the other hand, examples of the organometallic chelate compound having oxygen as a ligand include a metal chelate compound of alkanedione or a derivative thereof, such as 2,4-pentanedione (acetylacetone) and 3-phenyl-2,4-pentanedione. (3-phenylacetylacetone), 2,4-hexanedione, 2,4 (or 3,5) -heptanedione, 2,2,6,6-tetramethyl-3,5-heptanedione (dipivaloyl) methane)
Barium, calcium, aluminum, titanium, zinc, iron, lead, zirconium, yttrium or potassium chelate compounds such as lower alkanediones.
Of course, these may be mixed and used. For example, when a metal oxide thin film having thermistor properties is intended, a mixed raw material corresponding to a mixed oxide such as Co, Ni, and Fe may be used, and when a solid electrolyte thin film is intended, for example, it is stable. A mixed raw material corresponding to zirconia (Y ₂ O ₃ + ZrO ₂ ) may be used, and when an ion selective thin film is intended, a mixed raw material corresponding to the composition of the ion selective glass electrode may be used.

The above raw material is thermally decomposed and introduced into an oxygen gas atmosphere. The thermal decomposition temperature at this time varies depending on the type, but usually room temperature to 350 ° C. is sufficient. The pressure of the oxygen gas atmosphere needs to be adjusted so that plasma due to glow discharge can be generated, and is usually supplied to the vacuum chamber at 0.5 to 2 torr.

As the means for generating plasma in the oxygen gas atmosphere, various means used in capacitive plasma generators, inductive plasma generators and the like can be applied. Usually, a method in which a pair of opposing discharge electrodes are set in a vacuum chamber and a voltage is applied between them to perform glow discharge is suitable. The plasma generation time varies depending on the film thickness to be formed, but 5 to 30 minutes is usually sufficient.

Prior to the plasma generation, in the oxygen gas atmosphere,
A substrate is installed. Examples of such a substrate include various materials such as semiconductor elements, metallic materials, plastic materials, and insulating materials, and those corresponding to the characteristics and functions of the oxide thin film to be formed are appropriately selected and used. These shapes are usually suitable as plates. Of these, the conductive substrate can be used as a part of the discharge electrode as described above.

It is usually preferable to heat the substrate. However, the heating temperature is sufficiently low as compared with the melting point of the metal oxide to be formed and the case of thermal CVD, and in some cases, it may be kept at room temperature. By reducing the substrate temperature, it becomes possible to easily form a crystalline metal oxide thin film on a metal substrate such as aluminum having a low melting point or a plastic substrate.

The introduction of the above-mentioned organometallic compound of the raw material into the oxygen gas atmosphere is conveniently and preferably carried out by bringing powder or agglomerate of the compound into direct contact with the vacuum region through an introduction tube and spontaneously introducing it by sublimation. At this time, it is also a preferable embodiment to heat the compound slightly.

The metal oxide thin film thus formed is a non-porous thin film having a high crystallinity and substantially no pinhole, and its thickness is usually about 0.1 to 10 μm.

(E) Examples Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.

Example 1 Using an apparatus such as that shown in FIG.
A TiO ₂ thin film was formed. In the figure, (1) is a vacuum chamber, (2) and (3) are discharge electrodes, (4) is a power source for discharge, (5) is an oxygen gas cylinder, (6) is an oxygen gas flow meter, and (7) is a tetragon. Isopropoxy titanium [Ti (OC ₃ H ₇ ) ₄ ] powder, (8) oxygen gas and raw material gas introduction pipe, (9) raw material heating furnace (decomposition furnace), (10)
Is the heater, (11) is the power supply for the heater, (12) is the exhaust pipe, (1
3) vacuum pump system, (14) pyran gauge, (15) diameter 7
The figures show a disc-shaped aluminum substrate of cm.

The conditions of plasma CVD are shown below.

Aluminum substrate temperature: 130 ° C (heated by heater) Raw material decomposition temperature: 70 ° C Discharge power: 4w Electrode distance: 25mm Discharge frequency: 1KHz Discharge time: 8 minutes Oxygen gas pressure: 1torr Thus formed on the aluminum substrate The thickness of the TiO ₂ film was about 5000Å. The result of X-ray diffraction of this TiO ₂ film is as shown in FIG. 2, and it can be seen that it is an oxide having a high crystallinity mainly composed of a rutile phase. Further, the electron micrograph (× 20000) of the surface is as shown in FIG. 3, and it can be seen that it is a non-porous one having a crystal grain size of about 100Å without pinholes.

Example 2 Zirconium acetylacetonate [Zr (A
A) ₄ ] and yttrium acetylacetonate [Y (A
A) ₃ ] was used, a silicon wafer of 20 × 10 mm was used as a substrate, and a thin film was formed according to Example 1 under the following plasma CVD conditions. The raw materials were [Zr (AA) ₄ ] and [Y
(AA) ₃ ] and Y ₂ O ₃ are mixed at 8 mol%,
This was dissolved in methanol and evaporated to recrystallize, and this mixed crystal powder was used in the same manner as above.

Silicon wafer temperature: 200 ° C. Raw material decomposition temperature: 200 ° C. Discharge power: 8 w Electrode distance: 25 mm Discharge frequency: 1 KHz Discharge time: 10 minutes Oxygen gas pressure: 1 torr By treating in this way, on the silicon wafer,
An yttria-stabilized zirconia (Y ₂ O ₃ + ZrO ₂ ) thin film was obtained. This film thickness is about 1 μm, and as a result of X-ray diffraction,
As shown in FIG. 4, it was found that the cubic zirconia had a high crystallinity and was stabilized.

(F) Effect of the Invention According to the manufacturing method of the present invention, a crystalline metal oxide thin film can be formed without heating the substrate temperature to a high temperature unlike thermal CVD. Therefore, the oxide thin film can be easily formed on a metal substrate such as aluminum having a low melting point or a plastic substrate. Furthermore, the obtained metal oxide thin film is ideal because it has high crystallinity and substantially no pinholes.

The raw material (organometallic compound) used in the production method of the present invention is usually powdery and easy to handle, and if the raw materials are appropriately mixed and used, a metal oxide thin film corresponding to the composition can be obtained. Strict composition control of a multi-component system can be easily performed.

The metal oxide thin film formed by the manufacturing method of the present invention thus obtained is crystalline and thin, and therefore, for example, when it is formed as a sensor material (for example, a chemical substance sensitive film on a FET gate). Also, higher responsiveness can be expected as compared with the conventional one. Further, even when applied to a method for forming an oxide film on a semiconductor element, high temperature heating is not required, so that an improvement in yield can be expected.

[Brief description of drawings]

FIG. 1 is a structural explanatory view illustrating an apparatus used in the manufacturing method of the present invention, and FIG. 2 is a Ti obtained in Example 1 of the present invention.
An X-ray diffraction chart of the O ₂ thin film, FIG. 3 is an electron micrograph showing the crystalline state of the TiO ₂ thin film, and FIG. 4 is an X of the stabilized zirconia conjunctiva obtained in Example 2.
It is a figure showing a line diffraction chart.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Megumi Shinada, No. 1, Kuwahara-cho, Nishinokyo, Nakagyo-ku, Kyoto Prefecture, Kyoto Sanjo Plant, Sanjo Plant (56) References JP-A-56-78422 (JP, A) JP-A-SHO 56-20163 (JP, A)

Claims (1)

[Claims] 1. A pyrolysis gas of an organometallic chelate compound having a metal alkoxide and / or oxygen as a ligand is introduced into an oxygen gas atmosphere capable of generating plasma, and plasma is generated therein to generate the atmosphere. A method for producing an oxide thin film, which comprises forming a crystalline metal oxide thin film on the surface of a substrate placed inside.