JP2680888B2 - Thin film formation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses amorphous silicon (a-Si: amorphous silic) by plasma CVD under a pressure near atmospheric pressure.
on) and a method of forming a thin film such as titanium nitride (TiN).

[Conventional technology]

Since the invention of Spear, the a-Si manufacturing apparatus has been improved, but basically, glow discharge is performed at a low pressure.

Glow discharge does not occur unless the pressure is as low as about 0.1 to 10 Torr. If the pressure is higher than this, the discharge shifts to local arc discharge, and film formation on a substrate having poor heat resistance and uniform film formation over a large area cannot be performed. Thus, such a pressure is chosen.

Therefore, the container required an expensive vacuum chamber and a vacuum pump had to be installed.

In particular, in the case of a photoelectric conversion material such as a solar cell using a-Si or the like, or a surface protective film such as TiN, it is strongly demanded from the viewpoint of cost that a large-area thin film can be formed at once.

However, the plasma CVD method maintains a stable plasma by maintaining a glow discharge. Glow discharge is carried out in a vacuum (0.1-1
Only about 0 Torr).

Since a film can be formed only in a vacuum, if a large-area product is to be manufactured, the entire vacuum container must be enlarged.

 A high-power evacuation device is required.

Then, the equipment becomes extremely expensive.

Large-area uniform film formation and uniform treatment are absolutely necessary for cost reduction, but if the equipment cost becomes high, nothing will happen.

However, recently, under atmospheric pressure, plasma CVD
An invention was made that enabled the law. JP-A-63-5047
No. 8 (S.63.3.3 released).

This is to make a thin film of carbon C. For example, CH ₄ , C
The F ₄ as a raw material gas, but to which is added 90% He gas.

Because of the large amount of He gas, glow discharge can be maintained even at atmospheric pressure.

Since it is under atmospheric pressure, a vacuum chamber and a vacuum exhaust device are unnecessary. I think this is a great invention that can significantly reduce the cost of thin film formation.

An important point of this method is that glow discharge occurs even at atmospheric pressure and stays stable when He gas is used.

The inventor explains why He is as follows.

(A) He is easily excited by discharge.

(B) He has many metastable states and can produce many active particles in an excited state.

(C) He active particles dissociate hydrocarbons and hydrogen halides.

(D) In He, ions are easily diffused. Therefore, the discharge is likely to spread.

Naturally, the mixing ratio of He and CH ₄ becomes extremely important.

According to the description of the specification, at 92: 8, the spread of the glow discharge becomes narrower, and at 90:10, the corona discharge becomes
When it becomes 9.5: 10.5, there is spark discharge.

FIG. 4 shows the apparatus disclosed in Japanese Patent Laid-Open No. 63-50478.

A cylinder 12 is suspended from above in a vertically long reaction vessel 11.

Below the cylinder 12 is the electrode 14. RF oscillator 16, cylindrical
An RF voltage is applied to electrode 14 via a metal rod that passes through 12.

A support substrate (conductor) 17, an insulator 18, and a sample substrate 19 are provided below the container. There is also an annular external electrode 20.

A mixed gas of He and CH ₄ (the case of He, CH _4, CF ₄ also)
Is supplied from the gas inlet 21 at the upper end of the cylinder 12. This gas flows down the inside of the cylinder, passes by the side of the electrode 14, hits the sample substrate 19, partially reacts to form a thin film, and the rest is discharged from the side gas outlet 22. Glow discharge occurs between the electrode 14 and the supporting substrate (sample electrode) 17.

In addition, according to this specification, the present invention can be similarly applied to the formation of other thin films such as a silicon nitride film, amorphous silicon, a silicon carbide film, and the like.

[Problem to be solved by the invention]

The invention of Japanese Patent Application Laid-Open No. 63-50478 states that, according to a claim, "a mixture gas of about 90% or more of a rare gas and a gas containing a film component is formed by glow discharge under a pressure within a range of about 200 Torr to 2 atmospheres. It is a thin film forming method characterized by forming a thin film on a substrate without forming a plasma. "

(1) The inventor tried to form a C-based thin film on a 10 cm × 10 cm substrate using a mixed gas of CH ₄ and He gas according to this disclosure.

The pressure is atmospheric pressure. However, according to this disclosure, a glow discharge can be obtained, but the discharge is unstable (or non-uniform) depending on conditions. Also, because of the atmospheric pressure, gas replacement in the center of the plasma is not effectively performed, and the raw material gas is decomposed only in the outer peripheral portion of the plasma. Almost no film could be formed at the center of the substrate, and a uniform film could not be formed over a large area.

The inventor has also tried to make a-Si according to this disclosure.

In order to produce a-Si, a mixed gas of SiH ₄ gas and He gas was used. The pressure is atmospheric pressure. Since it is sufficient that the He gas is 90%, SiH ₄ : He = 10: 90 (volume ratio).
When this was attempted, an arc discharge occurred and no glow discharge occurred.

When the ratio of SiH ₄ / He was further reduced, a stable glow discharge could be generated between the electrodes.

However, since the SiH ₄ gas is extremely easily decomposed, it does not enter the plasma region, and the SiH ₄ is decomposed at the outer peripheral portion. Dust consisting of fine powder having a particle size of about 0.05 to 0.5 μm was only deposited on the outer peripheral portion of the plasma region.

It was not possible to form a thin film of a-Si on the sample substrate. That is, from these facts, it can be seen that the invention of Japanese Patent Application Laid-Open No. 63-50478 cannot be used as it is for uniform film formation of a large area even if it can be used for plasma formation at atmospheric pressure.

Further, in the invention of Japanese Patent Laid-Open No. 63-50478, the cost is extremely high because a large amount of expensive He gas is used.

In view of the above problems, in the present invention, a-
The object is to form a thin film of Si, TiN, diamond or the like by plasma CVD on a cylindrical substrate such as a drum, with a large area, uniformly and without using a large amount of diluting gas such as He.

Configuration of the Invention [Means for Solving the Problem] The present invention has the following features.

A blade electrode having N rotary blades is arranged adjacent to the cylindrical substrate so that the distance between the tip of the rotary blade and the outer peripheral surface of the cylindrical substrate is 0.1 to 10 mm or less.

An electrode having N rotary blades is rotated at least 1 / N revolutions per second or more to supply a mixed gas composed of a raw material gas and an inert gas such as He or Ar to the discharge space between the blade electrode and the cylindrical substrate. Then, glow discharge is caused to form a thin film on the cylindrical substrate.

In order to use the inert gas more efficiently, the inert gas is enclosed in the film forming chamber and only the raw material gas is supplied, and the above steps 1 to 3 are performed.

 The present invention will be described below with reference to FIG.

FIG. 1 shows an example of a thin film forming apparatus for carrying out the present invention, but the present invention is not limited by FIG.

Inside the film forming chamber 1, a blade electrode 2 having a plurality of rotary blades and a cylindrical substrate 3 are provided. FIG. 1 shows an example in which a high frequency power source 6 is connected to the blade electrode 2. In this case, the cylindrical substrate 3 is grounded. On the contrary, when the cylindrical substrate is conductive, the blade electrode 2 may be connected to the ground and the cylindrical substrate 3 may be connected to the high frequency power source 6. Here, the distance g between the tip of the rotary blade of the blade electrode 2 and the outer peripheral surface of the cylindrical substrate 3 is set to 0.1 to 10 mm.

Only a required amount of a mixed gas obtained by diluting the source gas with an inert gas such as He or Ar is introduced into the film forming chamber 1 through the gas inlet 7 and the excess gas is discharged through the gas outlet 8 to form a film. Keep the room at atmospheric pressure.

The mixed gas is supplied to the discharge space 6 as the blade electrode 2 rotates. Further, the rotation speed of the blade electrode 2 at this time is at least every second in the case of an electrode having N rotating blades.
Make it 1 / N rotation or more. The mixed gas amount introduced into the film forming chamber depends on the consumption rate of the source gas, that is, the film forming rate, so a desired value is selected. / Because there is a problem that the value of the inert gas decreases with the film formation time, gradually increase the value of the source gas / inert gas or introduce only the source gas as appropriate. May be.

Further, when only the raw material gas is introduced and the inert gas is contained, the gas discharge port 8 becomes unnecessary. The cylindrical substrate of the present invention means that the cylindrical substrate itself serves as both the substrate and the electrode, or the cylindrical substrate is used as a holder and a flexible film or the like is attached on the outer periphery thereof, or a flat plate is processed to form a cylinder. It is also included in the case where it is arranged along the whole or a part of the outer periphery of the substrate.

[Action]

Since the raw material gas is diluted with the inert gas, the discharge sustaining voltage is low. If the inert gas is 100%, glow discharge can be maintained under atmospheric pressure. Since the mixing amount of the source gas is small, glow discharge can be performed even under atmospheric pressure.

The action of the inert gas can prevent the transition to arc discharge.

Even at the same pressure, the mean free path of gas molecules is long in an inert gas. Therefore, the plasma is easily spread.

If the raw material gas / inert gas ratio δ exceeds a certain value, glow discharge cannot be maintained. Transition to arc discharge. According to an experiment conducted by the present inventors, the value of δ that shifts to arc discharge differs depending on the ease with which the source gas is decomposed. In order to suppress the transition to the arc and obtain a stable glow discharge, it is necessary that δ ≦ 10 ⁻¹ , provided that SiH ₄ , Si ₂ H ₆ , C ₂ H ₂ , C ₂ H _{4, GeH 4, N 2 O} , it is preferred in the case of easily decomposed gas such as O ₂ is δ ≦ 10 ^-2.

On the contrary, when the ratio δ of the source gas / inert gas is smaller than 10 ⁻⁴ , the film forming rate is lowered, which is not desirable.

Spreads plasma uniformly, prevents localization of discharge, and
In order to make the film thickness distribution uniform, it is better to narrow the gap g between the cylindrical substrate 3 and the tip of the rotary blade of the blade electrode 2. The smaller the value of g, the more stable and uniform glow discharge occurs in the electrode surface.
Especially when the cylindrical substrate 3 is conductive, its effect is great.

The value of g is preferably 10 mm or less. The reason is to expand the range in which the glow discharge occurs, prevent the discharge from being localized, and make the discharge intensity uniform. However, if they are too close to each other, it becomes difficult to install the blade electrode 2 and the cylindrical substrate 3 at a uniform distance. This is because a slight inclination or unevenness becomes a problem.

Practically, the value of g should be 0.1 mm or more. Since the blade electrode 2 has a rotary blade, the mixed gas can be stably supplied into the discharge space 6 by the rotation of the rotary blade. If the flow rate of the gas supplied to the discharge space is insufficient, the raw material gas, which is easily decomposed, immediately undergoes a polymerization reaction to generate dust and a thin film cannot be formed.
Therefore, the gas flow rate must be such that at least the discharge space volume is replaced in 1 second. That is, in the case of a blade electrode having N rotary blades, the rotation speed of the blade electrode needs to be 1 / N rotations per second or higher.

The pressure P may be atmospheric pressure P ₀ or the vicinity thereof.

The greatest advantage of the present invention is that it does not require a vacuum.

The pressure P, when slightly higher than the atmospheric pressure P ₀ can prevent contamination of impurity gases into the deposition chamber 1 from the outside.

The frequency of the high frequency power supply may be between 100 KHz and 100 MHz. The optimum values of the frequency and the power can be determined by the film to be formed and the gap between the electrodes.

However, glow discharge becomes unstable below 1 KHz in terms of discharge stability. Therefore, it should not be lower than 1KHz.

The power of the high frequency power supply is 10 ^-2 W / cm ² to 10 ^-2 W / cm ²
And ^Above 10 ^-2 W / cm ² , the blade electrode 2 is sputtered by ions.

 Therefore, impurities are mixed in the thin film.

If the power is lower than 10 ^-2 W / cm ² , a substantial deposition rate cannot be obtained. The shape of the rotor blades is selected efficiently in order to introduce the mixed gas into the discharge space efficiently. For example, as shown in FIG. 3, it extends in a curved shape from the center to expand the discharge space. The shape may be such that the tip has a brim for the purpose of making it uniform. The material of the brim provided at the tip may be not only a conductive metal but also an insulating material (glass, ceramics, etc.) for the purpose of stabilizing discharge.

FIG. 2 shows another embodiment of the present invention, in which a plurality of cylindrical substrates are installed on the outer periphery of one blade electrode, the mixed gas is contained, and only the raw material gas is supplied.

[Example 1] (Dependence on distance between electrode and cylindrical substrate) A glow discharge was caused under the conditions shown in Table 1 to examine the discharge state and the film thickness distribution. The apparatus used was that shown in FIG. He was used as the inert gas.

The blade electrode had eight blades and the rotation speed was 1 rotation per second. The drum was rotated once every 20 seconds. The results are shown in Table 2.

As shown in Table 2, when g = 15 mm, non-uniform discharge was accompanied by local arc discharge, but when g ≦ 10 mm, uniform and good film thickness distribution was obtained.

Example 2 (Dependence on Rotational Speed and Rotating Blade Number) Next, g = 3 mm was set, and the film forming rate was examined by changing the rotating speed and the rotating blade number. The conditions are shown in Table 3. The mixed gas supply rate in the film forming chamber was 50 cc / min.

The results are shown in Table 4.

From Table 4, if the number of rotor blades N is 1 / N rotation or less, a
In the case of -Si, SiH ₄ is easily decomposed, so that polymerization occurs in the gas phase and dust is formed.

In addition, the film formation rate was extremely reduced even with other TiN, aC films. Therefore, the number of revolutions needs to be 1 / N revolutions per second or more.

Example 3 (Discharge state and raw material gas / inert gas gas ratio) The raw material gas / inert gas ratio was changed under the same conditions as in Example 1 to examine the state of glow discharge. The distance between the electrode and the substrate was 3 mm. He was used as the inert gas.

 The results are shown in Table 5.

Moreover, as a result of conducting the same examination as in Example 2 using the rotary blades shown in FIG. 3, the film forming rate was improved by 10 to 20% as a whole, and the supply amount of the mixed gas to the discharge space was increased. It was found to be effective for stable discharge.

Example 4 (supplying only raw material gas containing inert gas) Next, using the apparatus shown in FIG. 1, the inert gas was contained while the gas outlet 8 was closed, and only the raw material gas was supplied to the film forming chamber. The results of film formation are shown below. The distance between the electrodes was set to 3 mm, and the amount of raw material gas supplied to the deposition chamber was changed
It carried out on the same conditions as a table. The results are shown in Table 6.

As described above, continuous film formation for 30 minutes to 1 hr was possible, and the film formation rate was good.

〔The invention's effect〕

-According to the present invention, plasma CVD is performed at a pressure near atmospheric pressure.
A thin film of a-Si, TiN diamond or the like can be formed by the method.

-Because it is near atmospheric pressure, no vacuum chamber or vacuum exhaust device is required.

・ The equipment cost can be greatly reduced in coating TiN on a photosensitive drum or a cylindrical substrate that requires a large area of film formation.

-Because the pressure is high, the deposition rate can be increased compared to low pressure plasma CVD.

・ Furthermore, since gas is selectively supplied into the discharge space,
No expensive diluting inert gas is required, or the amount used can be minimized.

-A plurality of cylindrical substrates can be formed at the same time.

[Brief description of the drawings]

FIG. 1 is an example of a schematic sectional view of an apparatus used for the thin film forming method of the present invention. FIG. 2 is another example of the thin film forming method of the present invention. FIG. 3 is a schematic cross-sectional view 1 of an electrode structure used in the present invention.
Example. FIG. 4 is a sectional view of the thin film forming apparatus disclosed in JP-A-63-50478.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Shoji Nakagama, Shoji Nakagumi, 1-1, Kunyokita, Itami City, Hyogo Prefecture Sumitomo Electric Industries, Ltd. Itami Works (72) Inventor, Yuuji Tomikawa, Kunyo, Itami City, Hyogo Prefecture North 1-1-1 Sumitomo Electric Industries, Ltd. Itami Works (72) Inventor Tsunenobu Kimoto 1-1-1 Kunyo Kita, Itami City, Hyogo Prefecture Sumitomo Electric Industries Itami Works (72) Invention Person Nobuhiko Fujita 1-1-1 Kunyokita, Itami City, Hyogo Prefecture, Sumitomo Electric Industries, Ltd. Itami Works (56) References JP-A-63-50478 (JP, A) Sakukai 62-191867 (JP, U) )

Claims (2)

(57) [Claims] Claim: What is claimed is: 1. A blade electrode having N rotary blades and a cylindrical base body, wherein the distance between the tip of the rotary blade and the outer peripheral surface of the cylindrical base body is
The blade electrodes are arranged adjacent to each other so as to be 0.1 to 10 mm or less, and the blade electrodes are rotated at least 1 / N revolutions per second or more to form a film forming gas and an inert gas in the discharge space between the blade electrodes and the cylindrical substrate. A thin film forming method comprising: forming a thin film on a cylindrical substrate by causing a glow discharge to occur under a pressure near atmospheric pressure by a high frequency electric field applied to the discharge space. 2. A N-rotor blade is provided in a film-forming chamber capable of holding a mixed gas of a film-forming gas and an inert gas under a pressure near atmospheric pressure and supplying only the film-forming gas. The blade electrode and the cylindrical substrate are arranged adjacent to each other so that the distance between the rotor blade tip and the outer peripheral surface of the cylindrical substrate is 0.1 to 10 mm or less, and the blade electrode is rotated at least 1 / N per second or more. Rotating to supply the mixed gas to a discharge space between the blade electrode and the cylindrical substrate, causing a glow discharge in the discharge space by a high-frequency electric field to form a thin film on the cylindrical substrate. Method for forming thin film.