JPH0519520B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a diamond thin film substrate having a uniform and dense diamond thin film and a method for manufacturing the same.

[Problems to be solved by conventional technology/invention]

Conventional, microwave CVD method, thermal filament
A diamond thin film is formed on a substrate made of diamond, silicon, Mo, W, Ti, Ta, etc. by a vapor phase synthesis method such as a CVD method. However, when a substrate other than diamond is used, the disadvantage is that the diamond nucleation density is low and film-like diamond cannot be obtained.

To solve this problem, (1) a method of polishing the substrate with diamond powder with a particle size of about 1 to 100 μm, and then forming a diamond thin film using a vapor phase synthesis method (2) using diamond powder with a particle size of about 1 to 100 μm Methods have been developed, such as a method in which a substrate is ultrasonically polished using a powder dispersed in ethanol, and then a diamond thin film is formed.

Although these methods improve the nucleation density compared to untreated substrates, it is still difficult to obtain a dense diamond thin film, and there are problems such as the inability to obtain a film with a film thickness of 1 μm or less, and the problem of uniformity. There is a problem in that the nucleation density cannot be obtained, and the nucleation density is distributed within the plane, making it impossible to form a uniform film. In addition, there is a problem in terms of electrical properties, such as the fact that due to the influence of grain boundaries, diamonds have considerably inferior properties compared to natural diamonds.

[Means to solve the problem]

As a result of intensive research to improve the drawbacks of diamond thin film substrates obtained by these conventional methods, the inventors of the present invention provided an amorphous silicon carbide film containing annealed amorphous or microcrystals as an intermediate layer. Later, it was discovered that by forming a diamond thin film under specific conditions, a uniform, dense diamond film with good electrical properties could be obtained without pre-treating the substrate with diamond paste or diamond powder. , arrived at the present invention.

That is, the present invention provides an intermediate film formed of annealed amorphous amorphous or amorphous silicon carbide containing microcrystals with a film thickness of 10 Å to 100 μm provided on a substrate, and further provided thereon with a nucleation density of 10 ⁷ /cm. A diamond thin film substrate consisting of ^two or more diamond thin films, and when manufacturing the diamond thin film substrate,
The present invention relates to a method for manufacturing a diamond thin film substrate, characterized in that a diamond thin film is formed by a CVD method.

〔Example〕

Examples of the substrate used in the present invention include
Metal substrates such as Cu, W, Mo, Ti, Ta, Cu alloy, Al alloy, Ti alloy, TiC, TiN, ceramic substrates such as Vycor, Myoceram, alumina, zirconia, magnesia, crystalline Si,
Examples include semiconductor substrates such as GaAs and InP, but are not limited to these.

In the present invention, on the substrate, a film with a thickness of 10 Å to
A substrate on which an intermediate film of annealed amorphous or amorphous silicon carbide containing microcrystals of 100 μm, preferably 100 Å to 10 μm is formed is used.

When the film thickness is less than 10 Å, a uniform annealed amorphous silicon carbide film or an amorphous silicon carbide film containing microcrystals cannot be obtained and becomes island-like.
If it exceeds 100 μm, the stress value increases and the warpage of the substrate increases.

The silicon carbide preferably has a carbon content of 40 atm% or more (ratio to the total amount of silicon and carbon, the same applies hereinafter), and more preferably 50 to 50 atm%.
70 atm%, silicon content is preferably 60 atm% or less (ratio to the total amount of silicon and carbon, the same applies hereinafter), more preferably 30 to 50 atm%, and hydrogen atoms, halogen atoms, etc. are preferably 10 atm% or less (total atoms ), more preferably 5 atm
% or less, and especially contains hydrogen atoms as hydrogen atoms, halogen atoms, etc.
The content is preferably 5 atm% or less.

Since the intermediate film is an annealed amorphous or amorphous silicon carbide film containing microcrystals, effects such as improved nucleation density can be obtained.

There is no particular limitation on the method of forming the silicon carbide film, and it may be formed by any method as long as it is formed by annealing a predetermined silicon carbide film formed on a substrate. Since the structure of the silicon carbide film formed differs depending on the conditions during film formation, etc., it is preferable to select and employ the film as appropriate.

Examples of the film forming method include a sputtering method, a vapor deposition method, a CVD method, and a plasma CVD method. Among these methods, for example, a plasma CVD method using an apparatus as shown in FIG. 7 is used. This is preferable because an amorphous silicon carbide film containing dense amorphous or microcrystals is formed at a lower temperature.

FIG. 7 is a diagram for explaining an example of an apparatus for forming an amorphous silicon carbide film containing amorphous or microcrystals using RF.

RF power supply 1, matching circuit 2 and RF electrode 3
The RF oscillated by the reactant gas inlet 4 converts the reactant gas such as CH ₄ +SiH ₄ +H ₂ into plasma while controlling it by OES (plasma spectroscopy), and the substrate 6 on the heater 5 is coated with amorphous or amorphous gas. Amorphous silicon carbide containing crystals is deposited, and the exhaust gas is discharged from the exhaust gas outlet 7.

The conditions for forming an amorphous or amorphous silicon carbide film containing microcrystals using the plasma CVD method are that the substrate temperature during film formation is 300°C.
The temperature is preferably 800°C to 800°C from the viewpoint of uniformly obtaining an amorphous silicon carbide film containing dense amorphous or microcrystals, and more preferably 500 to 800°C. Further, the reaction pressure is usually about 0.1 to 10 Torr, preferably about 0.3 to 2 Torr.

Amorphous or amorphous silicon carbide films containing microcrystals formed by the plasma CVD method can be used as intermediate films without treatment, but annealing can improve the heat resistance of the film and further improve the network structure of the film. A more dense film can be obtained, and a more preferable amorphous silicon carbide film containing amorphous or microcrystals can be formed. The atmosphere during annealing is preferably vacuum or N ₂ .

The conditions for the annealing treatment are 700 to 1400
℃ for about 2 hours is common, and the temperature is 700 to 1000℃.
It is preferable to anneal for about 2 hours.

The diamond thin film substrate of the present invention is a substrate in which a diamond thin film is provided on the silicon carbide film.

The diamond thin film is a film that can be identified as diamond by Raman spectroscopy or X-ray diffraction, and diamond that does not substantially contain amorphous carbon or graphite is deposited on a desired portion of the substrate surface. It is a thin film that is formed substantially uniformly and densely, and the film thickness is usually about 0.1 to 300 μm, preferably about 0.2 to 100 μm, and the nucleation density is 10 ⁷
The number of particles/cm ² or more is about 10 8 pieces/cm 2 or more, preferably about 10 ⁸ pieces/cm ² or more.

The diamond thin film used in the present invention usually has about 10 ⁷ to ^{10 10} diamonds/cm ² as described above, so it is different from a diamond thin film obtained by polishing using a conventional diamond paste or the like. In comparison, a more uniform and denser diamond film can be obtained.

When the film thickness is less than about 0.1 μm, it tends to become difficult to form a film, and when it exceeds about 300 μm, it tends to easily peel off from the substrate due to the stress of the diamond thin film.

Next, a method for forming a diamond thin film will be explained.

Any method currently used (plasma CVD method, thermal filament method, thermal plasma method, etc.) may be used to form the diamond thin film.
The plasma CVD method, especially the microwave CVD method using the equipment shown in Figure 8, is stable.
Excellent in terms of uniformity, etc.

FIG. 8 is a diagram for explaining an example of an apparatus for forming a diamond thin film using microwave-excited plasma.

Normally, microwaves oscillated by a 2450 MHz microwave oscillator 8 pass through an isolator 9, are matched and adjusted by a matching box 11, and are then guided to a plasma zone 14 through a waveguide 12, and are introduced into the reactant gas inlet. CH ₄ + H ₂ introduced from 13
A reactive gas such as is turned into plasma while being controlled by OES (plasma spectroscopy), and deposited on a substrate 15 having an amorphous silicon carbide film containing annealed amorphous or microcrystals,
The exhaust gas is discharged from the exhaust gas outlet 16. At this time, cooling water is supplied from the cooling water inlet 17, and adjustments are made using the plunger 18 so that plasma is generated on the substrate. In addition, in the figure, 10 is a power monitor.

For example, a diamond thin film has a substrate temperature of 600°C or more.
About 1000℃, preferably about 700~1000℃, more preferably about 850~900℃, reaction pressure 5~
About 300 Torr, preferably about 20 to 100 Torr,
Preferably, a method such as a microwave CVD method using microwaves of about 300 W to 1 kW is preferable.

The diamond thin film substrate thus obtained has properties such as specific resistance of 10 ¹³ to 10 ¹⁵ Ωcm, dielectric constant of 5 to 6, refractive index of 2.38 to 2.40, hardness >8000, and density of 3.4 to 3.6 g/cm ^{3 .} However, it can be suitably used for applications such as semiconductor heat sinks, protective films for cutting tools or cutter drills, antireflection films for infrared rays, and diaphragms for speakers.

Next, the substrate of the present invention will be explained based on examples.

Example 1 and Comparative Example 1 CH ₄ 75SCCM, SiH ₄ 15SCCM,
_H2 100SCCM, pressure 1Torr, substrate temperature 350℃, RF
A silicon carbide film with a thickness of 3000 Å was deposited on the single-crystal silicon surface (511) serving as the substrate under film-forming conditions with a power of 400 W.

The amount of C in the deposited film was measured using X-ray electron spectroscopy (XPS).
According to the method, it was 60 atm%, and it was reflective type.
The amount of hydrogen in the film determined by FTIR method was 10 atm%.

After that, use an electric furnace at a heating rate of 20℃/min.
The temperature was raised at 900°C, held for 2 hours, and then cooled and annealed at a cooling rate of °C/min.

The amount of hydrogen in the film after annealing was 2 atm%.
In addition, the crystallinity was examined by X-ray diffraction, but no clear peaks were found, confirming that it had an amorphous structure.

Next, microwave CVD as shown in Figure 8
Set the silicon substrate on which the silicon carbide film is formed on the BN holder of the device,
_CH4 15SCCM, _O2 3SCCM, _H2 100SCCM, pressure
A diamond thin film was formed under the deposition conditions of 40Torr, microwave (MW) power of 400W, and substrate temperature of 850℃.

When the surface of the substrate on which the obtained diamond thin film was formed was observed using a scanning electron microscope (SEM), Figures 1 and 2 (SEM photographs of the obtained diamond thin film at 5000x and 400x, respectively, As shown in the figure (showing the structure (shape), distribution state, etc. of the diamond particles constituting the thin film), a diamond thin film substrate was obtained in which diamonds were uniformly and densely formed over the entire surface. The nucleation density of the diamond thin film is 10 ⁷ to 10 ⁸
pieces/ ^cm2 .

When the obtained diamond thin film substrate was evaluated using Raman spectroscopy and X-ray diffraction, it was found to be diamond containing no amorphous carbon or graphite.

For comparison, FIGS. 3 and 4 (5000x and 400x magnification, respectively) show SEM photographs of diamond thin films produced in the same manner as described above, except that no silicon carbide film was provided. Note that the silicon substrate used was one that had not been polished with diamond paste.

From FIGS. 1 to 4, it can be seen that by providing an annealed amorphous silicon carbide film as an intermediate layer, the nucleation density increases dramatically.

Example 2 Using an apparatus as shown in Fig. 7,
A film was deposited on a single crystal silicon (111) substrate in the same manner as in Example 1 under the following film forming conditions: CH ₄ 70 SCCM, SiH ₄ 20 SCCM, H ₂ 100 SCCM, pressure 1 Torr, substrate temperature 400°C, and RF power 400 W. A 1000 Å silicon carbide film was deposited.

When the amount of C in the deposited film was examined using the XPS method, it was found to be 55 atm %, and the amount of hydrogen in the film determined by reflection type FTIR method was 8 atm %.

After that, use an electric furnace at a heating rate of 20℃/min.
After heating at 900°C for 2 hours, the cooling rate was
Annealing was performed by cooling at 20°C/min.

The amount of hydrogen in the film after annealing was 1 atm%.
Furthermore, it was confirmed by X-ray diffraction that it had an amorphous structure.

Next, the substrate on which the silicon carbide film was formed was polished for about 2 minutes using diamond paste.

The surface condition after polishing was examined using SEM (50,000x magnification), but no scratches were observed on the silicon carbide film, and no peeling of the silicon carbide film was observed at all.

Thereafter, using the apparatus shown in FIG. 8, Example 1
Similarly, CH ₄ 15SCCM, O ₂ 3SCCM,
_H2 100SCCM, pressure 40Torr, MW power 400W,
A diamond thin film was formed under film formation conditions where the substrate temperature was 850°C.

When the surface of the substrate on which the obtained diamond thin film was formed was observed using a SEM, the results were as shown in Figure 5 (SEM photograph of the obtained diamond thin film at 1000 times magnification).
As shown in Figure 2, a diamond thin film substrate was obtained with diamonds uniformly and densely formed over the entire surface. Note that the nucleation density of the diamond thin film was 10 ⁸ to ^{10 9} nuclei/cm ² .

When the crystallinity of the obtained diamond thin film substrate was evaluated in the same manner as in Example 1, it was found that the diamond thin film did not contain amorphous carbon and graphite.

For comparison, no silicon carbide film was provided.
Figure 6 shows a 1000x SEM photograph of a diamond thin film obtained by polishing a silicon wafer with diamond paste for 2 minutes and depositing diamond under the same conditions using the apparatus shown in Figure 8.

It can be seen from FIGS. 5 and 6 that a dense diamond thin film can be obtained by using an annealed amorphous silicon carbide film as an intermediate layer.

In addition, the thickness produced in the same manner as Examples 1 and 2
The 8 μm silicon carbide film had a Bitkers hardness of 3000 to 4000, which was as hard as single crystal silicon carbide.

It is thought that the effect of polishing the silicon carbide film with diamond paste is that by pasting a harder material with diamond, sharper scratches are generated and the nucleation density is increased.

〔Effect of the invention〕

The diamond thin film substrate of the present invention has an annealed amorphous silicon carbide film containing annealed amorphous or microcrystals on the substrate, and then diamond that does not substantially contain amorphous carbon or graphite is provided. This is a diamond thin film substrate. Such a substrate can be obtained by the method of the invention.

[Brief explanation of drawings]

Figures 1 and 2 are SEM photographs of the surface of the diamond thin film substrate of the present invention obtained in Example 1, observed at 5000x and 400x, respectively, showing the structure (shape) of the diamond particles constituting the thin film;
Figures 3 and 4 are SEM photographs taken at 5000x and 400x magnification, respectively, of the substrate surface obtained in Comparative Example 1, showing the structure (shape) of the diamond particles constituting the thin film. ), a photograph showing the distribution state, etc., Fig. 5 is an SEM photograph of the surface of the diamond thin film substrate of the present invention obtained in Example 2, observed at 1000x magnification, and Fig. 6 is a photograph showing the substrate obtained in Comparative Example 2. SEM photograph of the surface observed at 1000x magnification, Figure 7 is an explanatory diagram of an example of RF plasma CVD equipment used to form a silicon carbide film, and Figure 8 is MW plasma CVD used to form a diamond thin film. It is an explanatory diagram regarding an example of a device. (Main symbols in the drawings) 6: Substrate, 5: Substrate having a silicon carbide film.

Claims (1)

[Claims] 1. An intermediate film made of annealed amorphous silicon carbide or amorphous silicon carbide containing microcrystals with a film thickness of 10 Å to 100 μm provided on a substrate, and further provided thereon with a nucleation density of 10 ⁷ A diamond thin film substrate consisting of a diamond thin film of /cm ² or more. 2. A method for manufacturing a diamond thin film substrate, characterized in that, in manufacturing the diamond thin film substrate according to claim 1, the diamond thin film is formed by a CVD method.