JPH0647738B2 - Method for forming deposited film by plasma CVD method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a deposited film on a substrate, particularly a functional film, particularly a semiconductor device, a photosensitive device for electrophotography, a line sensor for image input, an imaging device, an optical device. The present invention relates to a deposited film forming method by a plasma CVD method that is most suitable for forming an amorphous deposited film used for an electromotive force element or the like.

[Description of the Prior Art and Problems]

Conventionally, semiconductor devices, photosensitive devices for electrophotography,
As element members used for image input line sensors, imaging devices, photovoltaic elements, etc., amorphous silicon, particularly amorphous silicon compensated with hydrogen atoms (H) or / and halogen atoms (X) [hereinafter referred to as "a- Si (H,
X) ". Membranes have been proposed, some of which have been put to practical use. And such a-Si
Several methods have been proposed for forming an a-Si (H, X) film together with a (H, X) film, such as a vacuum vapor deposition method, an ion plating method, a thermal CVD method, a plasma CVD method, and a photo CVD method. Among them, the plasma CVD method is put to practical use as an optimum method and is generally widely known.

By the way, in the plasma CVD method, a raw material gas for forming a deposited film (for example, SiH ₄ , Si ₂ H ₄ , SiF ₄ or the like) or a raw material gas and a diluent gas such as H ₂ gas, He gas or Ar gas are mixed. Plasma is generated in the gas by utilizing high frequency or microwave energy, and between chemically active species (radical species) such as excited species, free radicals and ions generated in the plasma, or between radical species and a raw material. It is to form a deposited film on the substrate surface by a complicated chemical action between the gases.

In such a conventional deposited film forming method by the plasma CVD method, the film quality of the formed a-Si (H, X) film may be different depending on the kind of the diluent gas used for diluting the source gas. There is a problem that the a-Si (H, X) film has different optical, electrical, or photoconductive properties.

That is, the above-described method for forming a deposited film by the plasma CVD method generally forms a-Si when an inert gas such as Ar gas, Kr gas, or Xe gas is used as the diluent gas.
When the quality of the (H, X) film is improved and the deposited film is used as a photoreceptive layer for electrophotography, it is said to have excellent electrophotographic characteristics. Even if the film forming conditions are strictly controlled, the film sometimes deposited on the surface of the substrate tends to be partially powdered depending on the direction of introduction and exhaust of the source gas, and the powder is mixed in the deposited film. In that case, if the formed deposited film is used for an electrophotographic light-receiving member, there is a problem that an image defect occurs in an image. Further, when H ₂ gas, He gas, etc. are used as the diluent gas, there is an advantage that the formation rate of the deposited film becomes relatively high, the problem of powder generation is small, and therefore the deposition latitude is wide. However, the formed a-Si (H, X) film is inferior to the above-mentioned case, and when the deposited film is used as a photoreceptive layer for electrophotography, there is a problem that sufficient electrophotographic characteristics are not exhibited. .

As described above, in the conventional deposited film forming method using the plasma CVD method, the formed a-Si (H, X) film has good film quality and various characteristics as a functional film, such as photosensitivity and charging ability. In addition to satisfying the requirements that the characteristics such as dark decay are excellent and that there is little unevenness in these various characteristics, at the same time satisfying the requirement that the film formation latitude is wide with little or no generation of powder on the substrate surface. The reality is that such a dilution gas has not been found, and especially in the present day when diversification and large area of functional membranes are required, solving these problems is one of the important issues, and an urgent solution to them is needed. Is desired.

[Object of the Invention] The present invention is based on a conventional plasma CVD method used for forming a deposited film used in a photosensitive device for electrophotography, a semiconductor device, a line sensor for image input, an imaging device, a photovoltaic device and the like. The purpose of the deposited film forming method is to solve the above-mentioned problems.

That is, a main object of the present invention is to deposit a deposited film by a plasma CVD method for constantly obtaining a deposited film having uniform film quality and film thickness and excellent optical, electrical and photoconductive properties. It is to provide a forming method.

Another object of the present invention is to widen the latitude of film formation, to improve the productivity of the deposited film and to mass-produce it.
It is an object of the present invention to provide a method for forming a deposited film by the plasma CVD method, which enables an increase in the area of a film.

[Structure of Invention]

The inventors of the present invention have conducted intensive studies to overcome the above-mentioned problems of the conventional method of forming a deposited film by the plasma CVD method and achieve the above-mentioned object. As a result, two or more diluent gases are mixed. By using it, it is possible to control the amount and energy of electrons in the discharge plasma, solve the above-mentioned problems, and obtain the knowledge that the above-mentioned object can be achieved, thus completing the present invention.

The above knowledge depends on the type of gas used as the dilution gas,
There are gas that is easy to discharge and gas that is difficult to discharge, and the state of the generated plasma differs depending on whether the gas that is easy to discharge is used as the dilution gas or the gas that is difficult to discharge is used as the dilution gas, and therefore a film is formed. It is based on the fact that the film quality of the film and the various properties such as optical, electrical and photoconductive are different.

That is, gases such as Ar gas, Kr gas, and Xe have relatively small ionization energies (for example, the ionization energy of each gas is 15.76 eV for Ar gas, 14.00 eV for Kr gas, and 12.13 eV for Xe gas). Therefore, the diluent gas absorbs most of the high-frequency or microwave energy because it easily discharges, and the high-energy electrons are reduced in the plasma that is generated.
This results in the formation of an a-Si (H, X) deposited film, while H ₂ gas or He gas has a relatively high ionization energy (for example, the ionization energy of each gas is 24.59 eV for He gas, Ne gas is 21.57 eV.),
Therefore, since it is difficult to discharge, most of the high frequency or microwave energy is absorbed by the source gas such as SiH ₄ , Si ₂ H ₆ , and SiF ₄ , and the generated plasma contains many high-energy electrons. And SiH ₄ , Si ₂ H ₆ , Si
For contacting a raw material gas for F _4, etc., it is formed a-Si (H,
X) Film deposition rate increases, but a-Si formed
The (H, X) film is no longer of satisfactory film quality.

Therefore, the present inventors continued their research, and used a mixture of at least two different dilution gases, such as a gas that is easy to discharge and a gas that is difficult to discharge, and tried to change the mixing ratio of those gases. When two or more kinds of diluent gases are mixed in a specific ratio, the a-Si (H, X) deposited film formed is constantly of good quality and the desired properties are obtained. confirmed.

The present invention has been completed based on these findings,
The essence is that when forming a deposited film on the surface of a substrate by irradiating the deposited film forming raw material gas with high frequency or microwave energy, at least two kinds of diluent gases are mixed with the deposited film forming raw material gas. There is a point to use.

And, regarding the diluent gas, H ₂ gas, He gas and
At least one selected from the group consisting of Ne gas, Ar gas, Kr gas and at least one selected from the group consisting of Xe gas are mixed and used, preferably H ₂ gas, from the group consisting of He gas and Ne gas. 5 to at least one selected
50% by volume and 95 to 50% by volume of at least one selected from the group consisting of Ar gas, Kr gas and Xe gas are mixed and used.

The source gas used for forming the deposited film by the method of the present invention is of the kind that excites species by high frequency or microwave energy and chemically interacts to form the desired deposited film on the surface of the substrate. Any material can be adopted as long as it is, for example, a-Si (H, X)
In the case of forming a film, specifically, gas such as silanes and halogenated silanes in which hydrogen, halogen, hydrocarbon or the like is bonded to silicon, or those which can be easily gasified are gas. It can be used. These source gases may be used alone or in combination of two or more. Furthermore, a-Si (H,
The film X) can be doped with a p-type impurity element or an n-type impurity element, and a raw material gas containing these impurity elements as a constituent is used alone or for the above-mentioned raw material gas and / or for dilution. It can be mixed with the gas and introduced into the reaction chamber.

The substrate may be conductive, semi-conductive, or electrically insulating, and specific examples thereof include metals, ceramics, and glass. The substrate temperature during the film forming operation is not particularly limited, but is generally in the range of 30 to 450 ° C, preferably 50 to 350 ° C.

In forming the deposited film, the pressure in the reaction chamber is set to 5 × 10 ⁻⁶ Torr or less, preferably 1 × 10 ⁻⁶ Torr or less before introducing the source gas, and when the source gas is introduced, the pressure in the reaction chamber is reduced. The pressure is 1 × 10 ^-2 to 1 Torr, preferably 5
It is desirable to set it to × 10 ^{-2 to 1} Torr.

Incidentally, the deposited film formation by the apparatus of the present invention is usually introduced into the reaction chamber without pretreatment (excitation seeding) of the source gas as described above, where the seeding is excited by high-frequency or microwave energy, Although it is carried out by causing a chemical interaction, when two or more kinds of raw material gases are used, it is also possible to pre-excite one of them and then introduce them into the reaction chamber.

〔Example〕

Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited thereto.

FIG. 1 is a schematic cross-sectional view showing an example of an apparatus suitable for carrying out the deposited film forming method by the plasma CVD method of the present invention, which is used in each example.

In FIG. 1, 1 is a high frequency power supply, 2 is a matching box, 3 is a diffusion pump and a mechanical booster pump, 4 is a motor for rotating a substrate, 5 is a substrate, 6 is a heater for heating a substrate, 7 is a gas introduction pipe, and 8 is High frequency introduction cathode electrode, 9 shield plate, 10 heater power supply, 21 to 2
7, 41-47 are valves, 31-37 are mass flow controllers, 51-57 are regulators, 61 is hydrogen (H ₂ ).
A gas cylinder, 61 is an argon (Ar) gas cylinder, 63 is a silane (SiH ₄ ) gas cylinder, 64 is a diborane (B ₂ H ₆ ) gas cylinder, 65 is a nitric oxide (NO) gas cylinder, 66 is a methane (CH ₄ ) gas cylinder, and 67 is Argon (Ar) gas cylinders are shown respectively.

Hereinafter, in each of the examples, an example of forming a photoreceptive layer for electrophotography by using the apparatus shown in FIG. 1 will be described, but the use of the deposited film formed by the method of the present invention is not limited. Absent.

Example 1 In this example, a cylindrical Al support (length 357 mm, diameter (r) 80 mm) was used as a substrate, and a charge injection blocking layer, a photosensitive layer and a surface layer were formed on the Al support. It was deposited as follows.

All the main plugs of the cylinders 61 to 67 were closed, all mass flow controllers and valves were opened, and the pressure inside the deposition apparatus was reduced to 10 ⁻⁷ Torr by the diffusion pump 3. At the same time, the heater 6 heats the Al support 5 to 250 ° C.
It was kept constant at ° C. After the Al support temperature becomes constant at 250 ° C., the valves 21 to 27, 41 to 47, and 51 to 57 are closed, the main plugs of the cylinders 61 to 67 are opened, and the diffusion pump 3 is replaced with a mechanical booster pump. Regulator 5
The secondary pressure of the valve with 1 to 57 is set to 1.5 kg / cm ² , the mass flow controller 31 is set to 50 SCCM, and the valve
41 and the valve 21 were sequentially opened to introduce H ₂ gas into the deposition apparatus. Next, Ar gas in the cylinder 62 was introduced into the deposition apparatus by the same operation as the introduction of H ₂ gas, with the mass flow controller 32 set to 250 SCCM.

Next, the SiH ₄ gas in the cylinder 63 was introduced into the deposition apparatus by the same operation as the introduction of the H ₂ gas, with the mass flow controller 32 set to 150 SCCM. Next, the mass flow controller 34 is set so that the gas flow rate of the B ₂ H ₆ gas in the cylinder 64 becomes 1600 ppm of the SiH ₄ gas flow rate, and the B ₂ H ₆ gas is introduced in the same manner as the H ₂ gas. Finally, the mass flow controller 35 was set so that the gas flow rate of the NO gas in the cylinder 65 was 3.4% of the SiH ₄ gas flow rate, and the NO gas was introduced in the same manner as the H ₂ gas.

At such a place, after adjusting the internal pressure in the deposition apparatus to 0.2 Torr and stabilizing the internal pressure, the high frequency power supply 1 is turned on, the matching box 2 is adjusted, and the glow between the Al support 5 and the cathode electrode 8 is adjusted. Discharge is generated, high frequency power is 150W, a-Si: O: H: B layer (charge injection blocking layer)
Was deposited. After depositing the 5 μm thick a-Si: O: H: B layer in this way, the valves 24 and 25 are closed without shutting off the discharge and the B ₂
The inflow of H ₆ and NO gas was stopped, and an a-Si: H layer (photosensitive layer) was deposited in the same manner as in the case of forming the charge injection blocking layer described above. When the layer thickness of the a-Si: H layer became 20 μm, the discharge was stopped, the valves 21 and 22 were closed to stop the inflow of H ₂ gas and Ar gas, and the mass flow controller 33 was set to 3
Change to 5 SCCM, further CH ₄ gas flow rate and the S of the gas cylinder 66
From the mass flow controller 36 preset so that the ratio of iH ₄ gas flow rate becomes SiH ₄ / CH ₄ = 1/30,
CH ₄ gas was introduced by opening the valve 25, and a 0.5 μm layer of a-SiC (H) layer (surface layer) was deposited with a high-frequency power of 150 W.

Finally, close all the high frequency power supply 1 and the gas valve,
The inside of the deposition apparatus was evacuated, the temperature of the Al support was lowered to room temperature, and the Al support on which the light receiving layer was formed was taken out.

With respect to the electrophotographic light-receiving member thus formed, the charging ability and the image property were evaluated, and obtained when the conventional diluent gas was H ₂ gas only and the diluent gas was only Ar gas. The chargeability and imageability of the obtained electrophotographic light-receiving member were also evaluated and compared.

For these evaluations, see Canon Digital Copier NP
9030 was used to measure the charging ability and the image quality under the same charging condition. The chargeability is measured by measuring the surface potential of the dark area at the position of the developing device when the corona voltage of the primary charge is +7.5 KV, and the image quality is on the entire area of one round of the drum on the A3 image (length 251 mm x width 297 mm). The number of image defects (black circles on a white background, or white circles on a black background) having a diameter of 0.3 mm or more was generated.

As a result of the evaluation, the method of the present invention, that is, when a deposited film is formed by using a mixed gas of H ₂ gas and Ar gas as a diluent gas, a conventional method, that is, when H ₂ gas alone is used as a diluent gas, It was found that a photoreceptive member for electrophotography having excellent charging ability and almost no image defects was obtained as compared with the case where only Ar gas was used as a diluent gas.

Example 2 Mixing ratio of H ₂ gas and Ar gas used as a diluent gas (Ar / H ₂
+ Ar) was changed to 0 to 1 to form an electrophotographic light-receiving member in the same manner as in Example 1, and the respective electrophotographic light-receiving members obtained were the same as in Example 1. Then, the charging ability and the image quality were evaluated. Fig. 2 shows the results, where the horizontal axis represents Ar / H ₂ + Ar and the vertical axis represents the charging ability (V / μ) and the number of image defects (pieces).
Is represented. − ○ − indicates changes in image defects, − ●
-Indicates a change in charging ability.

As is clear from FIG. 2, regarding the charging ability, a good result of 25 V / μ or more was obtained in the region where Ar gas was 100% to 53.5%. On the other hand, with regard to image quality, Ar gas is 0%.
Approximately the same good results were obtained up to 97.5%, but 97.5%
Image defects due to film peeling and abnormal growth began to stand out from the area exceeding%, which was not practically possible. Also, the surface property of the film was gradually deteriorated.

As a result, it became clear that the Ar gas ratio must be 97.5% to 53.5%.

Similar results were obtained when He gas or Ne gas was used instead of H ₂ gas.

Furthermore, similar results were obtained when Kr gas or Xe gas was used instead of Ar gas.

Example 3 By the same operation as in Example 1, a long wavelength absorption layer, a charge injection blocking layer, a photosensitive layer and a surface layer were formed on an Al support to obtain a photoreceptive member for electrophotography. The raw material gas flow rate and layer thickness when forming each layer were set as shown in the table below.

The electrophotographic light-receiving member thus obtained was evaluated for charging ability and image property in the same manner as in Example 1. As a result, it was found that the electrophotographic light-receiving member was excellent in both chargeability and image property.

[Summary of Effect of Invention]

The method for forming a deposited film by the plasma CVD method of the present invention uses a raw material gas for forming a deposited film and a mixture of at least two or more kinds of diluent gases to use the film quality of the formed deposited film and optical, electrical or A deposited film with good photoconductive properties can be obtained, and since there is no problem of powder generation during film formation, the deposition latitude can be widened, and productivity can be improved and area can be increased. Is something that can be done.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view schematically showing an example of an apparatus suitable for carrying out the deposited film forming method by the plasma CVD method of the present invention. Figure 2 shows the mixing ratio of the diluent gas (Ar / H ₂ + A
FIG. 4 is a diagram showing changes in charging ability and image quality when r) is changed, the vertical axis represents the charging ability and the number of image defects, and the horizontal axis represents the mixing ratio (Ar / H ₂ + Ar) of the dilution gas. It represents. About Fig. 1 1 …… High frequency power source, 2 …… Matching box, 3 ……
Diffusion pump, mechanical booster pump, 4 ... Substrate rotation motor, 5 ... Substrate, 6 ... Substrate heating heater, 7 ... Gas introduction tube, 8 ... High frequency introduction cathode electrode, 9 ... Shield plate, 10 ... power supply for heater, 21
~ 27, 41-47 ... Valve, 31-37 ... Mass flow controller, 51-57 ... Regulator, 61
~ 67 …… Gas cylinder

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location H01L 31/0248

Claims (3)

[Claims] 1. When forming a deposited film on a surface of a substrate by irradiating a deposited film forming raw material gas with high frequency or microwave energy, at least two kinds of diluent gases are mixed with the deposited film forming raw material gas. A method for forming a deposited film by a plasma CVD method, characterized in that 2. The diluent gas to be mixed and used is at least one selected from the group consisting of Ar gas, Kr gas and Xe gas,
The method for forming a deposited film by the plasma CVD method according to claim (1), which is at least one selected from the group consisting of H ₂ gas, He gas, and Ne gas. 3. The method for forming a deposited film by the plasma CVD method according to claim (2), wherein the diluent gas to be mixed and used is a mixture of Ar gas and H ₂ gas.