JPH02138472A - Method for cleaning deposited film forming device - Google Patents

Abstract

PURPOSE:To efficiently remove Si deposits in a short period of time by adding a rare gas to a gaseous mixture composed of SF6 and O2 compd. as an etching gas and effecting a plasma reaction at the time of removing the Si film deposited on the inside wall of an RF plasma CVD device which forms the Si deposited film by the plasma reaction by using a silane compd. as a raw material. CONSTITUTION:A substrate 206 made of glass is disposed in a film forming chamber 201 having an RF plasma generator 202 and the inside of the film forming chamber 201 is evacuated to a vacuum by a discharge valve 204. The substrate 206 is heated to about 250 deg.C by a heater 205 and the gaseous silane is supplied from a gas introducing pipe 208 for film formation to form the Si single crystal film in a vapor phase on the substrate 206 by the plasma reaction. The Si deposits and falls onto the inside wall of the film forming chamber 201 as well in this case and since this Si deteriorates the quality of the Si single crystal film, the cleaning gas 209 formed by mixing 5 to 60% rare gas, such as He, Ne, Ar or Kr with the gaseous mixture composed of 25 to 80% oxygen-contg. gas, such as O2 or No and the balance SF6 is supplied into the film forming chamber 201 to clean and remove the Si deposited on the inside wall of the film forming chamber 201.

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 discharge method, or an arc discharge method (hereinafter, these are collectively referred to as vapor phase methods).

[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, in the case of uniformly forming a photoconductive member on a drum 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 target 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 chamber and adhere to the substrate on which the functional deposited film is to be formed, which is one of the causes of film defects such as pinholes in the deposited film. was.

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.

[Problem to be solved by the invention] However, although the above-mentioned method removes the film and polysilane mainly composed of silicon atoms,
i02 remains as a residue, and 02, F2 molecules, etc. remain as adsorbents and are incorporated into the deposited film during the next deposition, resulting in a decrease in the usability of the material as a light-receiving member (decreased charging ability, image blurring, etc.) , or cause a decrease in photoconductive properties [decrease in photoconductivity (σ, h)/dark conductivity ((1,), decrease in mobility]. In particular, the above-mentioned use in deposited film formation where ions are generated) The properties or photoconductive properties 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, in addition to the above-mentioned cleaning, disassembly and cleaning of the reaction chamber etc. has been carried out every few cycles, or in addition to the above-mentioned cleaning, for example, a mixed gas of CF4 and F2, a mixed gas of Ar and F2, etc. each have a different reactivity. It became necessary to perform the reaction operation multiple times using multiple gases, 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 F a and oxygen compounds (02, No, NO2, etc.) has been considered, and for example, in the formation of a light-receiving member, even if deposited film formation and cleaning are alternately repeated under predetermined conditions, Good results have been obtained with no deterioration in the properties of use as a light-receiving member and photoconductive properties. However, the mixed gas of SF8 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, making it difficult to clean the entire reaction chamber. There remained the problem of an increase in the time required to complete the process and a decrease in the 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 the vapor phase method are alternately repeated. Another object of the present invention is to provide a method for cleaning a deposited film forming apparatus, which 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 conventional problems as described above, is a method for cleaning a deposited film forming apparatus that uses a reaction method when forming a deposited film containing silicon by a vapor phase method. In a method of cleaning deposits formed on the inner wall of a chamber, etc., by applying high frequency energy to gas molecules to cause a plasma reaction, and by the etching action of the active ingredient produced by the reaction, SF6 and oxygen are used as the etching gas. Compound (Ox
, NO, NO2, etc.), and the mixed gas is a mixed gas with a rare gas (0□, No, NO2, etc.), and the mixed gas is a rare gas (He, etc.).

Ne, Ar, Kr, Xs, etc.) are mixed, and the mixing ratio of the rare gas is 5-60% and the mixing ratio of the oxygen compound is 25-80%.

(Detailed Description of the Invention) As mentioned above, the mixed gas of SFs and oxygen compounds slightly lacks the stability or uniformity of the plasma in the reaction chamber. If there is a part that acts as an antenna for radio waves, plasma tends to concentrate in the antenna part or if the distance between the electrodes is close, making the plasma distribution in the reaction chamber uneven. The etching rate of deposits increases in areas where the plasma is strong, but it 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. The areas that were removed early were then etched excessively, which sometimes resulted in damage to those areas.

Therefore, as a result of intensive research, the inventors of the present invention found that the above-mentioned S
Rare gases (He, Ne,
It has been found that the stability and uniformity of the plasma in the reaction chamber can be improved without substantially reducing the etching rate by mixing etchants (Ar, Kr, Xe, etc.). By implementing the present invention, plasma can be uniformly distributed in all parts of the reaction chamber, even in devices where the distance between electrodes in the reaction chamber varies depending on the location, or in devices that have a part that serves as an antenna for high-frequency radio waves. As a result, the cleaning and removal time for deposits in the reaction chamber can be shortened, and the walls of the reaction chamber are not damaged due to excessive etching.

In the present invention, when the mixture ratio of the rare gas in the mixed gas of SF, i, oxygen compound, and rare gas used is up to 5%,
No improvement in the stability or uniformity of the plasma in the reaction chamber was observed, and if the mixing ratio of rare gas exceeded 60%, the stability or uniformity of the plasma was good, but the etching rate for deposits decreased. Noble gas mixing ratio 5-60
%, the cleaning removal time cannot be shortened. If the mixing ratio of oxygen compounds in the mixed gas used in the present invention is up to 25%, the amount of sulfur compounds remaining in the reaction chamber will increase, and if it exceeds 80%, a solid residue of 5 in 2 will adhere to the reaction chamber.

Examples of devices to which the present invention can be applied include electrophotographic photoreceptors, solar cells, line sensors, TPT, etc. in which by-products such as silicon atom-containing films and polysilane are produced in areas other than the intended substrate during manufacture. Examples of the deposited film forming method utilized in the present invention include devices such as plasma CVD in which ions are generated.
Examples include D method, microwave plasma CVD method, HRCVD method, and the like. As the etching gas used in the present invention, 5FsH, 5F4H2, etc. can be used in addition to SFe. O2 is common as an oxygen compound, but other oxygen compounds such as No.

No. 2 and the like can also be used in the same way as O. 2, and the ratio in the mixed gas is preferably in the range of 25-80%.

As the rare gas, it is easy to use He or Ar, but other rare gases such as Ne, Kr, and Xe can be used as well, and two or more types of rare gases can also be used as a mixture.

There is no problem with the pressure inside the reaction chamber during cleaning in the present invention as long as it is within a pressure range that can generate plasma, but lXl0
The appropriate range is from 0.1 Torr to 5 x 10 Torr, and the flow rate of the mixed gas of SF8, oxygen compound, and rare gas is determined from time to time depending on the volume of the reaction chamber and the capacity of the exhaust pump. The higher the high frequency energy applied to the gas molecules, the faster the etching speed will be, but it is determined appropriately depending on the configuration of the apparatus and the power source used, and is used in the range of several watts to 10'KW.

Example 1 FIG. 1 is a diagram schematically showing an RF plasma CVD apparatus used to form a deposited film on 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 being evacuated through A deposited film of A-3i was formed on the substrate by the vapor phase method due to 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 SF, 0□, and Ar 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 etching action of the generated active component causes the reaction chamber to become The deposited film formation and cleaning were successively repeated to clean the deposits on the inner walls and the like.

<Cleaning conditions> Gas used: 5F6 700 Seem.

380 Sccm.

460 Sccm (Mixing ratio 30%) 0.5 Torr 13.56 MHz 1.5 KW r Deposition chamber internal pressure Discharge frequency High frequency power Condolence table Comparative example 1 The conditions for forming the deposited film were the same as in Example 1, and SF6 was used for cleaning.
Deposited film formation and cleaning were continuously and repeatedly performed using a mixed gas of and 02. The washing conditions are shown below.

(Cleaning conditions) Gas used: SF, 700 Sccm.

02 380 5 can.

Deposition chamber internal pressure: 0.5 Torr Discharge frequency: 13.56 MHz High frequency power: 1.5 KW If the deposition chamber in Fig. 2 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 is 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 observed.

In Example 1, the distribution of the plasma intensity in the upper, middle, and lower parts was made almost uniform during cleaning, and the cleaning removal speed of deposits was also made almost the same, so the cleaning time for the entire deposition chamber was significantly shortened. There was also no damage inside the deposition chamber. The results are shown in Figure 4.

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 was rated A;

Evaluation in 5 stages: B, C, D, E), image defect evaluation (◎
= extremely high level, O = practically sufficient, △ = practically insufficient)
A comprehensive practical evaluation of photoconductive properties and use as an electrophotographic photoreceptor (◎ = extremely high level, O = practically sufficient, △ = practically insufficient) was conducted. 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.

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 to 12 The deposited film formation conditions were the same as in Example 1, and cleaning was performed under the conditions shown in Table 4 using a mixed gas of SFa, 02, and He as the cleaning gas, and the cleaning removal time of each part in the deposition chamber was Table 4 shows the cleaning time for the entire deposition chamber.

Example 13 Using the apparatus shown in FIG. 2, a deposited film of an electrophotographic photoreceptor was formed by the following operations.

In FIG. 2, reference numeral 201 is a deposition chamber as a film forming space, and a 705 film manufactured by Corning Co., Ltd.
9 glass substrates 206 were installed.

Next, the exhaust valve 204 is opened, and the inside of the reactor is pumped through the exhaust pipe 212 by a vacuum pump (not shown)! O-'To
The temperature was evacuated to rr, the heater 205 for heating the substrate was heated, and the substrate surface temperature was controlled to be 250°C.

Next, the gas co-supply pipe 2 is
A film-forming gas was introduced into the reactor through the introduction pipe 208 from 09, and at about the same time, discharge power was introduced by the discharge energy generator 202 to generate plasma and form a deposited film.

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.

Deposited film formation conditions〉 Gas used: Internal pressure inside the deposition chamber Discharge frequency High frequency power Substrate temperature Deposited film formation speed Thick film Cleaning conditions〉 Used gas: 5iHa 50Sccm O, 3Torr 13, 56MHz QW 250℃ 3.2 people/s e 1 μnl S F e 5 0 0 S c c
m.

022 7 0 S c m.

Ar 380Secm (mixing ratio 33%) Deposition chamber internal pressure 0.5 Torr Discharge frequency 13.56MHz High frequency power iooow Comparative Example 2 The deposited film formation conditions were the same as in Example 13, and the conventional S Fa and 02 were mixed for cleaning. Deposited film formation and cleaning were successively repeated using gas. The washing conditions are shown below.

<Cleaning conditions> Gas used: SFs 500Sccm.

0, 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 part, the part near the substrate support is the center part, and the part near the exhaust pipe 212 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. Cleaning and removal of deposits was slow, and the slowest was at the rear. If the cleaning and removal time for the central part is 1, then the front part requires 1.9 times the cleaning and removal time, and the rear part requires 2.1 times the cleaning and removal time. Partial damage was seen due to etching. In Example 13, the intensity of the plasma in the front, center, and rear parts was almost uniform during cleaning, and the cleaning speed of deposits was also almost uniform, so the cleaning time for the entire deposition chamber could be significantly shortened, and the deposition There was no damage inside the room. The results are shown in Table 5.

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 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, electrophotographic photoreceptors, solar cells, line sensors, TPT, etc. It was found that an extremely high quality A-3t:H semiconductor film that can be used in devices can be obtained with good reproducibility.

Example 14 FIG. 3 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"). .

The inside of the vacuum container 21 is evacuated via the exhaust pipe 305, and the cylindrical substrate 307 is heated by a substrate heating heater 308.
Next, a raw material gas such as silane gas or hydrogen gas is heated and maintained at a predetermined temperature by a raw material gas supply pipe 30B through a plurality of gas discharge holes 3 opened to the raw material gas supply pipe.
06'306'... was discharged into the vacuum container 301. At the same time, a microwave 304 with a frequency of 2.45 GHz is generated from a microwave power source (not shown).
was generated, and the microwave was introduced into the vacuum vessel 301 through the waveguide 303 and the dielectric window 302. Thus, according to the manufacturing conditions shown in Table 6, the raw material gas introduced into the vacuum container 301 is excited and dissociated by microwave energy, generating neutral radical particles, ion particles, electrons, etc., and mutually dissociating them. The reaction occurred and a deposited film of an electrophotographic photoreceptor was formed on the surface of the cylindrical substrate 307.

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.

Washing conditions> Gas used: SF6 400Sccm.

02 210Sccm.

Ar 260Sccm (mixing ratio 30%) Deposition chamber internal pressure 0.4mTorr Discharge frequency 2.45GHz Microwave power 1゜6KW Table Comparative Example 3 The deposited film formation conditions were the same as in Example 14, and SF was used for cleaning.
Deposited film formation and cleaning were continuously and repeatedly performed using a mixed gas of No. 6. The washing conditions are shown below.

Washing conditions> Gas used: SFa 400Sccm.

02 210Sccm Deposition chamber internal pressure 0.4 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, the plasma in the upper and lower parts was removed during cleaning. Because the plasma is strong and the plasma is weak in the center, the deposits on the top and bottom were cleaned and removed relatively quickly, but the center was slow. After. In Example 14, the intensity of the plasma in the upper, middle, and lower parts of the cleaning chamber was made almost uniform, and the cleaning removal rate of deposits was almost uniform, so that the cleaning time for the entire deposition chamber could be shortened.

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. Can be done.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the configuration of a deposited film forming apparatus used in the present invention. FIG. 2 is a schematic diagram of a deposited film forming apparatus used in the present invention. Figure 3 shows the microwave used in the present invention.
1 is a schematic cross-sectional view of a deposited film forming apparatus using a PCVD method. FIG. 4 is a graph showing cleaning time. 201... Film forming chamber, 202... High frequency plasma generator, 203... Cathode electrode for high frequency introduction, 204... Exhaust valve, 205... Heater for heating the substrate, 206... Substrate, 207 ... Gas introduction pipe, 208 ... Gas introduction pipe for film formation, 209 ... Cleaning gas introduction pipe, 210 ... Substrate support stand, 211 ... Exhaust pipe, 301 ... Vacuum container, 302... Reflexive window, 303... Waveguide, 304... Microwave, 305... Exhaust pipe, 306... Raw material gas supply pipe, 307... Cylindrical base, 308...・Heating heater stiffness

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. A method for cleaning a deposited film forming apparatus, characterized in that a mixed gas of SF_6 and an oxygen compound is used as an etching gas in the method for cleaning the deposits by action, and a rare gas is mixed in the mixed gas. (2) The method for cleaning a deposited film forming apparatus according to claim (1), wherein the mixing ratio of the rare gas in the mixed gas is 5-60%. (3) The mixing ratio of oxygen compounds in the mixed gas is 25-80
%. %. The method for cleaning a deposited film forming apparatus according to claim 1.