JPH02129371A - Method for cleaning device for forming deposited film - Google Patents

Abstract

PURPOSE:To maintain the quality of a deposited film on a high level and to uniformly and efficiently remove deposits on the inner wall, etc., of a reaction chamber by using an etching gas prepd. by mixing a gaseous SF6-oxygen compd. mixture with a gas other than SF6. CONSTITUTION:When a deposited film is formed on a substrate in a reaction chamber by a vapor phase process, an Si atom-based film and a silane polycompound are produced on the inside of the chamber. In order to remove the deposits, an etching gas prepd. by mixing a gaseous SF6-oxygen compd. mixture with a gas other than SF6 is used. The molecules of the etching gas are brought into a plasma reaction by applying high frequency energy and the deposits on the inner wall of the reaction chamber are removed by the etching action of the resulting active component. The etching gas other than SF6 may be CF4 or NF3 and is preferably mixed by about 10-80% of the total flow rate of the mixed etching gas. The deposits in the reaction chamber can be efficiently removed in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Description of the field to which the invention pertains] The present invention relates to a deposited film forming apparatus, particularly an RF plasma CVD
The present invention relates to a cleaning method for an apparatus for forming a deposited film by a method, a microwave plasma CVD method, a thermal CVD method, a glow-glow discharge method, or a discharge method (hereinafter collectively referred to as a vapor phase method).

[Description of the Prior Art] The technique of forming a functional film on a substrate by a vapor phase method has already been widely employed, for example, when forming a film on a drum uniformly for a leading member in electrophotography. When forming a deposited film by such a vapor phase method, it is unavoidable that a part of the reaction product adheres as a film or powder to a portion other than the intended substrate, that is, to the inner wall of the reaction chamber or the like.

These films or powders that adhere to the inner walls of reaction chambers, etc.
It is easy to peel off, and these peeled off particles and powder fly inside the reaction tank and adhere to the substrate on which the functional deposited film is to be formed, and this is one of the causes of film defects such as pinholes in the deposited film. Become.

Conventionally, as an example of a deposited film formed by a vapor phase method, there is a deposited film for a light-receiving member whose main component is silicon atoms, which is formed by a plasma reaction using, for example, a silane compound. In the reaction chamber where this deposit was formed, a coating mainly composed of silicon atoms and a heavy composite of silane (
A large amount of polysilane (called polysilane) is produced as a by-product, and as a method of cleaning and removing it, a method of cleaning by plasma reaction using a mixed gas of CF4 and 02, for example, has been used.

[Problems to be Solved by the Invention] However, although the above-mentioned method removes the film and polysilane mainly composed of silicon atoms,
in2 remains as a residue, and 02, F, molecules, etc. remain as adsorbents and are incorporated into the deposited film during the next deposition formation, resulting in, for example, deterioration of the usability characteristics as a light-receiving member (decreased charging ability, image blurring, etc.) ), internal vision causes a decrease in photoconductive properties [a decrease in photoconductivity (σph)/dark conductivity (σd)] and a decrease in mobility. Particularly in the formation of a deposited film in which ions are generated, the above-mentioned usage characteristics or photoconductive characteristics are significantly deteriorated.

Therefore, if the above-described deposited film formation and cleaning are repeated in repeated cycles, the characteristics will gradually deteriorate, and the quality of the product will exceed the allowable limit in a relatively short period of time. Therefore, until now, in addition to the above-mentioned cleaning, the reaction chamber etc. had to be disassembled and cleaned every few cycles, or for example, Ar and H
It became necessary to perform the reaction operation multiple times using a plurality of gases each having a different reactivity, such as the mixed gas of No. 2, resulting in a decrease in productivity.

Therefore, S is used as an etching gas for cleaning the deposited film forming equipment.
The use of a mixed gas of F6 and oxygen compounds (02, No, NO2, etc.) has been studied. Good results have been obtained with no deterioration in the usage characteristics as a receiving member or in the photoconductive characteristics. However, the mixed gas of SF and oxygen compounds lacks plasma stability or uniformity in the reaction chamber, so depending on the configuration of the device, the cleaning area within the reaction chamber may become uneven, and the entire reaction chamber can be cleaned. There remained the problem of an increase in the time required for the cleaning to be completed, and a problem of decreased durability of the device due to excessive etching and damage to parts of the reaction chamber where cleaning was completed early.

[Object of the invention] The present invention solves the conventional problems and maintains the quality of the deposited film at a high level when forming the deposited film and cleaning the reaction chamber etc. by a vapor phase method are alternately repeated. It is an object of the present invention to provide a method for cleaning a deposited film forming apparatus that can uniformly and efficiently clean deposits formed on the inner walls of a reaction chamber, etc.

[Means for Solving the Problems] The method for cleaning a deposited film forming apparatus of the present invention, which was discovered as a means to solve the above-mentioned conventional problems, is a method for cleaning a deposited film forming apparatus that uses a vapor phase method to form a deposited film containing silicon. In a method of cleaning deposits formed on the inner wall of a reaction chamber or the like by applying high frequency energy to gas molecules to cause a plasma reaction, and using the etching action of the active ingredient produced by the reaction, the etching gas may include SF, and oxygen compounds (0
This method is characterized by using a mixed gas with other gases (e.g., No. 2, No. 2, No. 2, No. 2, No. 2, No. 2, No. 2, No.

More specifically, the method for cleaning a deposited film forming apparatus of the present invention includes:
Etching gases other than SF6, especially CF a or NF3, can be used to maintain the high quality of the deposited film and the high speed of etching when etching with SF6.
This method is characterized by achieving etching uniformity by utilizing the effect of concentrating etching on areas in the reactor where a large amount of deposits are distributed, which occurs when used in combination with etching.

As mentioned above, the mixed gas of SF6 and oxygen compounds slightly lacks the stability or uniformity of the plasma in the reaction chamber. In cases where the electrodes are close to each other, or where the electrodes are close to each other, plasma tends to concentrate on the antenna portion, resulting in non-uniform distribution of plasma within the reaction chamber. Therefore, the etching rate of deposits in the reaction chamber increases in areas where the plasma is strong, but decreases significantly in areas where the plasma is weak, resulting in an increase in the time required to clean and remove deposits throughout the reaction chamber. In addition, areas where cleaning and removal were completed quickly were subsequently etched excessively, resulting in damage to those areas.

Therefore, as a result of intensive research, the inventors of the present invention found that the above-mentioned S
SF is a mixed gas of F and oxygen compounds.

It has been found that by mixing other etching gases (such as CF4 and NF3), it is possible to improve the stability and uniformity of etching within the reaction chamber without substantially reducing the etching rate. By implementing the present invention, it is possible to make the etching time uniform in all parts of the reaction chamber, even in devices where the distance between electrodes in the reaction chamber varies depending on location, or in devices that have a part that serves as an antenna for high-frequency radio waves. As a result, it was possible to shorten the cleaning and removal time of deposits in the reaction chamber, and the walls of the reaction chamber were not damaged due to excessive etching.

In the present invention, when the mixing ratio of gases in the reaction furnace is kept constant during the etching process, if the mixing ratio of etching gases other than 5Fet in the mixed gas is up to 10% of the total etching gas flow rate, No improvement in etching stability or uniformity was observed, and if the mixing ratio exceeded 80% of the entire etching gas flow rate, the etching stability or uniformity was good, but the etching rate for deposits decreased. Therefore, the mixing ratio of etching gases other than SF is 10 to 8 with respect to the entire etching gas flow rate.
Outside the range of 0%, the cleaning removal time cannot be shortened.

In addition, when changing the mixing ratio of SF, an oxygen compound, and an etching gas other than SF during the etching process, the optimum etching for each reactor shape can be achieved by arbitrarily changing the ratio of etching gases other than SF6. You can decide the process.

Examples of devices to which the present invention can be applied include electrophotographic photoreceptors, solar cells, line sensors, etc. in which by-products such as silicon atom-containing coatings and polysilane are produced in areas other than the intended substrate during their manufacture. Examples include devices such as TPT. Examples of deposited film forming methods that can be used in the present invention include plasma CVD, microwave plasma CVD, HRCVD, and the like. The oxygen compound used in the present invention is usually O2, but other oxygen compounds such as No. 2, No. 2, etc. can also be used in the same manner as 02.

The mixing ratio of the oxygen compound is preferably 10% or more and 80% or less, and optimally 25% or more and 60% or less, in order to increase the etching gas usage efficiency and maintain the absolute value of the etching rate at a high value.

However, no matter which oxygen compound is used, SF6 and SF
Although the efficiency of using etching gases other than 6 is improved, SF
Etching stability and uniformity at each mixing ratio of etching gases other than SF6 and SF6 do not depend on the mixing ratio of oxygen compounds, but depend on the mixing ratio of SF6 and etching gases other than SF6.

As the etching gas other than SF used in the present invention, CF4 or NF is suitable, but SiF4 is also suitable.
, BF3. F2 etc. can be used similarly. It is also possible to use a mixture of two or more types of etching gas.

There is no problem with the pressure inside the reaction chamber during cleaning in the present invention as long as it is within the pressure range that can generate plasma;
-' Torr to 5 x 10 Torr is appropriate, and the flow rate of the mixed gas of SF, oxygen compound, and etching gas other than SF6 is determined from time to time depending on the volume of the reaction chamber and the capacity of the exhaust pump. 1102 from ISccm
It is used in the range of SL, and the higher the high frequency energy applied to the gas molecules, the faster the etching rate, but it is appropriately determined depending on the form of the apparatus and the power source used, and is used in the range of several watts to 10'' kW.

[Example] (Example 1) Fig. 1 is a diagram showing an outline of an RF plasma CVD apparatus used when forming a deposited film of an electrophotographic photoreceptor by a vapor phase method. 101 is a cylindrical cathode electrode, and 102 is a cylindrical anode electrode that also serves as a base. exhaust pipe 11
The raw material gas is introduced from the gas introduction hole 109 of the gas introduction pipe 108 under the conditions shown in Table 1 into the reaction chamber which is evacuated through A deposited film of A-Si was formed on the substrate by the vapor phase method using the action of plasma.
At this time, some of the reaction products also adhered to the inner walls of the reaction chamber.

The formed electrophotographic photoreceptor was taken out, a dummy substrate having the same shape as the substrate for deposit formation was attached in its place, and the gas introduction tube 10 was cleaned under the cleaning conditions shown below in the same manner as when forming the deposited film.
A mixed gas of SF6, 02, and CF4 is introduced through the gas introduction hole 109 of No. 8, and plasma is generated by high frequency radio waves introduced from the high frequency matching box 112, and the inner wall of the reaction chamber is etched by the etching action of the generated active component. The deposited film formation and cleaning were successively repeated.

<Cleaning conditions> Gas used: SF6 480 Sccm, Q,
4QOSccm.

CF4320 Sccm (Mixing ratio 40%) 0, 5 Torr 13, 56 MHz 1.5 KW Discharge frequency Deposition chamber internal pressure High frequency power Power table Comparative example 1 The deposited film formation conditions were the same as in Example 1, and SF8 was used for cleaning.
Deposited film formation and cleaning were successively repeated using a mixed gas of O2 and O2. The washing conditions are shown below.

<Cleaning conditions> Gas used: SF, 800 Sccm, 02
400 Seem.

Deposition chamber internal pressure: 0.5 Torr Discharge frequency: 13.56 MHz High frequency power: 1.5 KW If the deposition chamber in Fig. 1 is divided into three parts: upper, middle, and lower, in Comparative Example 1, during cleaning, the plasma in the upper and lower parts was stronger in the center. Because the upper and lower parts of the inner wall of the deposition chamber are weaker, the deposits on the upper and lower parts of the inner wall of the deposition chamber are cleaned and removed relatively quickly, but the deposits in the center are the slowest to clean and remove, and the cleaning and removal time for the upper deposits is standardized as 1. Then, the cleaning and removal time for the central part was 1.8, which is the time required to finish cleaning the entire deposition chamber, and the upper and lower parts, where cleaning and removal were completed earlier, were still partially damaged due to excessive etching. It was seen. Example 1
In cleaning, the distribution of plasma intensity at the top, center, and bottom is the same as in Comparative Example 1, but the cleaning removal rate of deposits depends on the amount of deposits remaining or the surface area of deposits due to the addition of CF4. As etching progresses, the etching rate gradually increases in areas where the plasma intensity is weak, so the cleaning and removal times for the upper, middle, and lower parts of the reactor were almost the same. Therefore, the cleaning time for the entire deposition chamber was significantly shortened, and there was no damage to the interior of the deposition chamber.

The results are shown in Figure 2. In this way, deposited film formation and cleaning were repeated for 20 cycles each, and the image deletion of the electrophotographic photoreceptor was evaluated at the initial cycle, the 10th cycle, and the 20th cycle (one with an excellent image condition is designated as A, and A, B, C,
evaluation on a 5-level scale of D and E), image defect evaluation (◎ = extremely high level, O = practically sufficient, △ = practically insufficient), and photoconductive properties and overall practical use as an electrophotographic photoreceptor. evaluation(
◎ = extremely high level, ○ = practically sufficient, △ = practically insufficient). The results are shown in Table 2.

Table 2 shows that by carrying out the present invention, the cleaning time of the deposition chamber can be shortened, and even if deposited film formation and cleaning are repeated, there is no change in the deposited film characteristics, and the quality can be maintained at a high level. I understand.

Knee-' (Examples 2 to 10) The deposited film forming conditions were the same as in Example 1, and Tables 3 and 4
The cleaning was carried out under the conditions shown in the table, and the cleaning time for each part of the deposition chamber and the cleaning time for the entire deposition chamber are shown in Tables 3 and 4.

(Examples 11 and 12) The deposited film forming conditions were the same as in Example 1, and cleaning was performed under the conditions shown in Table 4 using SF, a mixed gas of 02, and NF3 as the cleaning gas, and each part in the deposition chamber was cleaned. Table 4 shows the cleaning removal time and the cleaning time for the entire deposition chamber.

[-11 (Example 13) Using the apparatus shown in FIG. 3, a deposited film of an electrophotographic photoreceptor was formed by the following operations.

In FIG. 3, 301 is a deposition chamber as a film forming space, and a 705 film manufactured by Corning Co., Ltd. is placed on a substrate support stand 310 inside.
9 glass substrate 306 was installed.

Next, the exhaust valve 304 is opened, and a vacuum pump (not shown) is used to pump the inside of the reactor to 10''To
The temperature of the substrate surface was controlled to be 250° C. by exhausting the air to rr and generating heat by the heater 305 for heating the substrate.

Next, under the deposited film formation conditions shown below, the gas supply period 3
From 08, a film forming gas was introduced into the reactor through the introduction pipe 307, and at the same time, discharge power was introduced using the discharge energy generator 302 to generate plasma and form a deposited film.

In addition, the present invention was carried out under the following cleaning conditions to clean the subcomponents in the reaction chamber, and the deposited film formation and cleaning were successively repeated.

SiH450Sccm O,3 Torr 13, 56MHz 　W　W 250℃ 3.2 people/s e c 1μm <Deposited film formation conditions> Gas used Deposition chamber internal pressure discharge frequency high frequency power Substrate temperature Deposited film formation rate Film thickness Washing conditions> Gas used SF6 3505ccm 02 270Sccm.

CF 4 150Sccm (mixing ratio 30%) Deposition chamber internal pressure 0.5 Torr Discharge frequency 13.56 MHz High frequency power 100.0 W (Comparative Example 2) The deposited film formation conditions were the same as in Example 13, and conventional SF6 and cleaning were used. Deposited film formation and cleaning were continuously and repeatedly performed using a mixed gas with o2. The washing conditions are shown below.

<Cleaning conditions> Gas used: S F6500 S c c m.

02 270Sccm Deposition chamber internal pressure 0.5Torr Discharge frequency 13.56MHz High frequency power 1000W In the deposition chamber shown in Figure 3, the part near the gas introduction pipe is the front, the central part of the base support is the center, and the part near the exhaust pipe 311 is the rear. In Comparative Example 2, the plasma in the central part was strong and the plasma in the front and rear parts were weak during cleaning, so the deposits in the central part were cleaned relatively quickly, but the deposits in the front and rear parts were cleaned relatively quickly. The cleaning removal was slowest in the rear part. If the cleaning and removal time at the center is 1, then the front is 1.9 and the rear is 2.
1, and the central part, where cleaning and removal was completed earlier, was then excessively etched until the rear part was finished, resulting in partial damage. In example
As the ratio of residual deposits on the front and rear increases, the front,
A phenomenon was observed in which the etching speed at the rear part became faster than at the beginning of etching, and the final cleaning time for deposits was almost equal, so the cleaning time for the entire deposition chamber could be significantly shortened, and there was no damage inside the deposition chamber. Ta.

Thus, the deposited film formation and cleaning were repeated 20 cycles each, and the characteristics of the A-3i:H semiconductor film at the initial cycle, 10th cycle, and 20th cycle were evaluated, and the results are shown in Table 5.

Table 5 shows that by implementing the present invention, the cleaning time of the deposition chamber can be shortened, and even if deposited film formation and cleaning are repeated, electrophotographic photoreceptors, solar cells, line sensors, TPT, etc. It was found that an extremely high quality A-Si:H semiconductor film with good reproducibility that can be used in devices can be obtained.

(Example 14) FIG. 4 is a diagram showing an outline of an apparatus used to form a deposited film on an electrophotographic photoreceptor by a plasma CVD method using microwaves (hereinafter referred to as "rMw-PCVD method"). It is.

The inside of the vacuum container 401 is evacuated via the exhaust pipe 405, and the cylindrical substrate 407 is heated by the substrate heating heater 40.
8, the sample was heated to a predetermined temperature and maintained. Next, a raw material gas such as silane gas or hydrogen gas is fed into the vacuum container 401 via a raw material gas supply pipe 406 through a plurality of gas discharge holes 406' opened in the raw material gas supply pipe. Released. At the same time, a microwave power source (not shown) generates a microwave 404 with a frequency of 2.45 GHz, and the microwave is transmitted through the waveguide 403 and into the vacuum container 401 via the electric window 402. It was introduced in

Thus, according to the manufacturing conditions shown in Table 6, the vacuum container 401
The introduced raw material gas is excited and dissociated by microwave energy to generate neutral radical particles, ion particles, electrons, etc., which react with each other to form an electrophotographic photoreceptor on the surface of the cylindrical substrate 407. A deposited film was formed.

In addition, the present invention was carried out under the following cleaning conditions to clean by-products in the reaction chamber, and deposited film formation and cleaning were successively repeated.

<Cleaning conditions> Gas used: SF8 300sccm O, 210 sccm.

CF4 100100S c mixing ratio 25%) mTorr 2, 45GHz 1.6KW Deposition chamber internal pressure discharge frequency microwave power (blank below) Funeral table (Comparative example 3) The conditions for forming the deposited film were the same as in Example 14, and SF was used for cleaning.
Deposited film formation and cleaning were successively repeated using a mixed gas of 6 and O2. The washing conditions are shown below.

<Cleaning conditions> Gas used: SF, 400SccmO, 210S
ccm Deposition chamber internal pressure 1 mTorr Discharge frequency 2.45 GHz Microwave power 1.6 KW If the deposition chamber in Fig. 4 is divided into three parts: upper, middle, and lower, in Comparative Example 3, during cleaning, the plasma in the upper and lower parts was strong and concentrated in the center. Since the plasma in the upper and lower parts was weak, the deposits on the upper and lower parts were cleaned and removed relatively quickly, but the cleaning and removal time on the central part was slower.If the cleaning and removal time on the upper and lower parts was 1, the cleaning and removal time on the central part was 1.6. In Example 14, the plasma intensity in the upper, middle, and lower parts during cleaning was similar to that in Comparative Example 2;
Due to the effect of CF4 used in combination with SF6, as the ratio of deposits remaining on the upper and lower parts decreases, the etching speed in the center increases, and the cleaning and removal time for all deposits is almost the same. It was possible to shorten the cleaning time for the entire deposition chamber.

Thus, the deposition film formation and cleaning were repeated 20 cycles each, and the characteristics of the electrophotographic photoreceptor at the initial cycle, 10th cycle, and 20th cycle were evaluated in the same manner as in Example 1, and very good results were obtained. The results are shown in Table 7.

[Effects of the Invention] According to the present invention, deposits in the reaction chamber can be efficiently cleaned and removed in a short time when cleaning a deposited film forming apparatus, and the quality of the deposited film to be formed can be maintained at a high level. be able to.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the configuration of a deposited film forming apparatus used in the present invention. FIG. 2 is a graph showing cleaning time. FIG. 3 is a schematic diagram of a deposited film forming apparatus used in the present invention. Fourth
The figure is a schematic cross-sectional view of a deposited film forming apparatus by microwave-PCVD method used in the present invention. 101... Reaction tank container, 102... Cylindrical conductive substrate, 103... Container bottom plate, 104... Substrate holder is stand, 106... Top lid or gate, 108.108... Gas introduction Pipe, 109.109,109...Gas introduction hole, 112...
・High frequency matching box, 3... Gas exhaust pipe, 4... Resistance heating element 1... Film forming chamber, 2... High frequency plasma generator, 3... Cathode electrode for high frequency introduction, 4. ... Exhaust valve, 5... Heater for heating the substrate, 6... Substrate, 7... Gas introduction pipe, 8... Gas introduction pipe for film formation, 9... Cleaning gas introduction pipe, 0. ...Base support stand, 1...Exhaust piping, 1...Vacuum container, 2...Electrical window, 3...Wave guide, 4...Microwave, 5...Exhaust Pipe, 6... Raw material gas supply pipe, 7... Cylindrical base, 408... Heating heater

Claims (3)

[Claims] (1) When forming a silicon-containing deposited film using the gas phase method, deposits that occur on the inner walls of the reaction chamber are removed by applying high-frequency energy to gas molecules to cause a plasma reaction, and the active components produced by the reaction are etched. In the method of cleaning the deposits by action, a mixed gas of SF_6 and an oxygen compound is used as an etching gas, and S is further added to the mixed gas.
A method for cleaning a deposited film forming apparatus, characterized by mixing an etching gas other than F_6. (2) The etching gas other than SF_6 that is further mixed with the above-mentioned mixed gas of SF_6 and an oxygen compound is CF_4.
The method for cleaning a deposited film forming apparatus according to claim 1, characterized in that: (3) Etching gas other than SF_6 that is further mixed with the above-mentioned mixed gas of SF_6 and an oxygen compound is NF_3.
The method for cleaning a deposited film forming apparatus according to claim 1, characterized in that: