JPH0368948B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for forming a deposited film, and particularly to a method suitable for forming a film constituting a photoconductive member of an electrophotographic photoreceptor. [Prior art] As one of the thin film manufacturing methods, CVD (Chemical Vapor
CVD methods that utilize low-temperature plasma have been in the spotlight in recent years. In this method, the pressure inside the reaction tank is reduced to a high vacuum, the raw material gas is supplied into the reaction tank, and then the raw material gas is decomposed by glow discharge to form a thin film on the substrate placed in the reaction tank. For example, it is applied to the production of amorphous silicon films. In this method silane gas (SiH ₄ )
The amorphous silicon film prepared using amorphous silicon as a raw material gas has relatively few localized units in the forbidden band of amorphous silicon, and it is possible to control valence electrons by doping with substitutional impurities, making it suitable for electrophotography. A product with excellent physical properties has been obtained, and expectations are high. By the way, for example, an electrophotographic photoreceptor generally has a photoconductive layer provided on a cylindrical (drum-shaped) base for forming a deposited film, but plasma CVD
When producing a cylindrical electrophotographic photoreceptor by this method, an apparatus having a configuration as shown in FIG. 4 has conventionally been used. That is, this device includes a vacuum chamber container 51, an upper lid or gate 52 of the container, a DC or high frequency cathode electrode 54 connected to a power source 53, an exhaust system 55 for reducing the pressure inside the container, and a gas for forming a deposited film. It is equipped with a gas introduction system 56 for introducing gas, a heater 57 for heating the substrate, and the like. A normally conductive cylindrical base 58 housed in a vacuum chamber 51 is attached to a rotating shaft 59 for rotating the base, and the rotating shaft 59 is electrically grounded. A deposited film such as a photoconductive layer is formed by introducing gas and performing glow discharge while rotating the base 58. 60 is a shield for confining plasma, and 61 is a motor for driving the rotating shaft 59. By the way, rotating the base 58 using this type of rotation mechanism 59, 61 has conventionally been considered indispensable from the viewpoint of uniformity of film formation, but this has the following problems. . In other words, eccentricity or vibration of the rotating shaft tends to cause unevenness or deviation in the thickness and characteristics of the deposited film that is formed.Since the substrate and the rotating shaft are rotating, it is important to ensure electrical continuity between them. The rotating mechanism complicates the structure inside the reaction tank and disturbs the glow discharge, causing defects such as image defects in electrophotographic photoreceptors, for example. It is difficult to prevent gas leaks at the connection with the base, which can also cause product defects.Since the base is rotating, it is not possible to attach a temperature sensor to the base, etc., resulting in inaccurate base temperature management. The problem is that the yield rate of the product film is poor, and the provision of a rotating mechanism itself increases the cost of the equipment and film products. The inventors of the present invention have made extensive studies to solve the above-mentioned problems associated with conventional deposited film forming methods, and have found that when a deposited film is formed using an apparatus with a specific structure or configuration, unexpected results can be obtained. It was discovered that the uniformity of film formation can be maintained without using a rotation mechanism, the stability of glow discharge is improved, and it becomes easier to obtain the desired characteristics of the deposited film formed, and in order to complete the present invention. I've reached it. [Objective and Summary of the Invention] The object of the present invention is to maintain the uniformity of film formation and improve the stability of glow discharge by plasma CVD, while forming a deposited film with uniform and excellent properties. An object of the present invention is to provide a method for forming a deposited film. The above object is a method for forming a deposited film on a substrate by introducing a gas for forming a deposited film into a reaction tank containing a substrate, wherein the reaction tank is composed of a cylindrical container that acts as a cathode electrode, Further, the base is a cylindrical conductive base that is arranged substantially aligned with the axis of the reaction tank container and electrically grounded, and a deposited film is formed by keeping this base stationary and performing glow discharge. This is achieved by the deposit forming method of the present invention. [Embodiments] Hereinafter, embodiments of the present invention will be described with reference to the attached drawings. FIG. 1 is a schematic diagram showing an example of the configuration of a film forming apparatus of the present invention equipped with a cylindrical conductive substrate. The apparatus shown in FIG. 1 includes a cylindrical reaction vessel 1 which is made of a conductive structural material such as stainless steel, aluminum, nickel, or an alloy made of these materials as a substrate, and which can function as a cathode electrode.
This container 1 is a cylindrical conductive base pedestal 4 that is fixed to a container bottom plate 3 that is fixed via an annular insulator 2, and that is arranged approximately aligned with the axis of the reaction tank container 1.
A cylindrical conductive substrate 5 is placed on a substrate holder 4 with its axis substantially aligned with the reaction tank container. The base holder 4 is electrically grounded. Reference numeral 7 denotes an upper lid or gate detachably or slidably attached to the container 1 via an annular insulator 6. Note that the substrate holder does not have to be cylindrical, and may have any shape as long as it can stably place the substrate, but by making it the same cylindrical shape as the substrate,
The device structure can be simplified in terms of arranging heaters and the like. Furthermore, by making the diameter of the cylindrical pedestal substantially the same as or slightly larger than that of the base body, it is possible to contribute to stabilizing the goo discharge. 8, 8 is a gas introduction pipe for forming a deposited film;
In order to maintain uniformity of film formation, it is preferable to have a plurality of gas introduction holes 9, 9, 9, etc. uniformly distributed over approximately the same length as the substrate length, and for the same reason, the reaction tank container It is preferable that a plurality of them be arranged substantially concentrically at substantially uniform angles around the axis of the substrate in the gap between the substrate and the substrate.
In the example shown in FIG. 1, four gas introduction pipes, including those not shown, are arranged at approximately 90 degrees to each other. When carrying out the method of the present invention, the ratio R ₁ /R ₂ of the outer diameter R ₁ of the substrate and the inner diameter R ₂ of the reaction tank container is determined.
is preferably in the range of 0.2 to 0.8, more preferably 0.3 to 0.6. If R ₁ /R ₂ is less than 0.2, the discharge gap becomes too wide and the introduced gas does not efficiently reach the substrate and is not deposited thereon, which is not preferable. In addition, if it exceeds 0.8, even if the eccentricity between the substrate and the reaction tank is slight, it will be significantly affected, making it difficult to make the film properties uniform.
In addition, it is undesirable because it is easily affected by inclusions such as gas pipes and it is difficult to control discharge. Further, the outer diameter R ₃ of the gas introduction tube affects the flow of gas for discharge and deposited film formation, but it is preferably within the range of R ₃ ≦1/6 (R ₂ −R ₁ ). When R ₃ exceeds 1/6 (R ₂ - _{R 1} ), the difference in the discharge state becomes noticeable between where the gas introduction tube is present and where it is not.
This is not preferable because the uniformity of discharge or film formation deteriorates. Similarly, the diameter R ₄ of a concentric circle with the base body formed by arranging a plurality of gas introduction pipes and passing through the center of each gas introduction pipe is 1/2 (R ₂ - _{R 1} ) ≦ R ₄ - _{R 1} . It is preferable to satisfy the relationship. FIG. 5 shows R ₁ , R ₂ , R ₃ , R ₄ , 1/2 (R ₂ −R ₁ ) of the film forming apparatus used in the present invention.
shows the interrelationship between The gas introduction holes 9, 9, 9... can be opened in any direction, but in order to improve the efficiency of the flow of gas for forming a deposited film, it is necessary to open them in the direction of the substrate as shown in Figure 1. It can be opened towards. Furthermore, if it is desired to diffuse the flow of the gas for forming a deposited film to some extent in the gap between the substrate and the reaction vessel, it is possible to open the opening in a direction other than the substrate, for example, toward the inner surface of the reaction vessel. can. The flow rate of the deposited film forming gas flowing through these gas introduction holes 9, 9, 9... may be appropriately optimized according to the value of the shape factors _R1 to _R4 . When opening in the direction of , it is preferable to select the flow velocity in the range of 1.5 to 1.5×10 ⁴ m/s, more preferably 10 to 2000 m/s. Furthermore, when the gas introduction hole is opened toward the inner surface of the reaction tank, the flow rate is preferably selected within the range of 1.5 to 1.5×10 ⁴ m/s. Gas flow rate is 80~
A range of 1200 SCCM is suitable, and in order to ensure such a flow rate, it is preferable to use about 2 to 16 gas introduction pipes. Returning to FIG. 1, the respective gas inlet pipes 8, 8
The upper end is closed, and the lower end is connected to a gas introduction pipe 11 outside the reaction tank by a connector 10 which also serves as a sealing member hinged to the bottom plate 3, and this introduction pipe 11 is further connected to a gas introduction pipe 11 for forming a deposited film. It is connected to a gas supply source such as a cylinder. Further, numeral 12 in FIG. 1 is a high frequency matching box electrically connected to the reaction tank container 1, and this matching box (not shown) oscillates a high frequency in a practical high frequency band of 1 km to 1 GHz, for example. It can be connected to a high frequency oscillator to supply high frequency power to the container 1. Reference numeral 13 denotes a gas exhaust pipe, which is connected to a suitable vacuum depressurization means such as a rotary pump or a mechanical booster pump, so that the inside of the reaction tank container 1 can be depressurized. 14 more
is a resistance heating element, and the temperature can be controlled to maintain the desired substrate temperature. When carrying out the method of the present invention using such an arrangement, first open the top cover or gate 7, put the cylindrical conductive substrate 5 into the container 1, and place the container 1 and the substrate holder 4 in the shape of the substrate holder 4. Place it so that its axis is almost aligned.
Next, the upper lid or gate 7 is closed and the exhaust pipe 13 is evacuated to reduce the pressure inside the reaction tank to a degree of vacuum of about 10 ^-2 to ^{10 -6} Torr, and then the deposited film forming gas is introduced from the gas introduction pipes 8, 8. At the same time, high frequency power is supplied to the container 1 to generate a glow discharge, and the base 5 is
A deposited film is formed while keeping it stationary. Furthermore, the conditions for glow discharge are 150°C as the substrate temperature.
~350°C is preferred, and the cathode (reactor vessel) is
Cooled as desired. FIGS. 2 and 3 show a modification of the device shown in FIG. 1. FIG. If the same elements as in Fig. 1 are represented by the same symbols, the second
In the device shown in the figure, a temperature sensor (for example, a thermocouple) 31, which can measure the temperature by contacting the conductive substrate 5,
Of these, the sensors 32 and 33 are embedded in the base holder 4 and measure the temperature of the lower end of the base 5, and the sensor 33 is made of, for example, a shape memory alloy or a spring material. The temperature can be measured at any part of the inner surface of the base body. If the temperature of the substrate is directly measured using such a sensor, the temperature of the substrate can be easily controlled and the yield of product films can be improved. In the example shown in FIG. 3, a conductive internal holder 41 having approximately the same diameter as the inner diameter of the substrate 5 to be placed is attached to the substrate holder 4. As shown in FIG. Internal holder 41
has a step-like skirt that fits into the lower end of the base body 5 having a notch in the inner surface layer, and an annular flange 4 protruding from the inner surface layer.
2, and the opening 43 of this flange 42
The top of the base 5 is supported and positioned by inserting the top 44 into the bottom plate 3 of the reaction tank and pressing the support 45 fixed or seated on the bottom plate 3 of the reaction tank by the flange 42 and the spring material 46 sandwiched between the top 44 and the support 45. It is designed so that it can be done. By using such a holder, grounding can also be established from the upper part of the base, making it easier to stabilize the characteristics. According to the method for forming a deposited film of the present invention, by selecting gases for forming a deposited film and combining them as desired,
A deposited film having a single layer or multilayer structure can be formed on a cylindrical conductive substrate. Incidentally, when forming an amorphous silicon film, for example, silicon hydrides such as SiH ₄ and Si ₂ H ₆ , halides thereof, and silicon halides such as SiF ₄ and SiCl ₂ F ₂ are used as raw material gases. be able to. When forming a SiC _x film, for example, a mixed gas of SiH ₄ and CH ₄ , C ₂ H ₄ , C ₂ H ₆ , etc., and when forming a SiN _x film, use SiH ₄
When forming _{a SiO 2 film} , for example, a mixed gas of SiH ₄ and _{O 2 ,} Al ₂ O ₃
When forming a film, AlCl ₃ and O ₂ , NO, N ₂ O,
Mixed gas with NO ₂ etc., GeH ₄ etc. can be used when forming an amorphous germanium film. Hereinafter, an example of the configuration of an electrophotographic photosensitive drum will be described as an example of a photoconductive member that can be manufactured by the deposited film method of the present invention. Such a photoconductive member has, for example, a structure in which a charge injection blocking layer, a photoconductive layer (photosensitive layer), and a surface protection layer are sequentially laminated on a support that serves as a conductive substrate in the method of the present invention.Support The shape is cylindrical, and the thickness is appropriately determined so as to form a desired photoconductive member. However, if flexibility is required as a photoconductive member, the function as a support may be determined. It is made as thin as possible within the range where it can be sufficiently exhibited. However, even in such cases, from the viewpoint of manufacturing and handling of the support, as well as mechanical strength, etc.,
It is considered to be 10 μm or more. The surface of the support is given a mirror finish by, for example, mirror cutting to maintain the uniformity of the photoconductive member, and the photoreceptor is used as a light source for digital image information using coherent monochromatic light such as a laser beam. In order to prevent interference fringes when used for recording, mechanical precision processing such as diamond cutting using a lathe, milling machine, etc. or other precision processing such as chemical etching may be used to create a regular or irregular pattern, such as a spiral pattern. A fine unevenness is added. The charge injection blocking layer is made of, for example, amorphous silicon (hereinafter referred to as s-Si) containing hydrogen atoms and/or halogen atoms, and also contains periodic silicon, which is usually used as an impurity in semiconductors, as a substance that controls conductivity. It contains atoms of elements belonging to Groups or Groups of the Table of Contents. The thickness of the charge injection blocking layer is preferably 30 Å to 10 μm, more preferably 40 Å to 8 μm, and optimally 50 Å to 5 μm. Instead of the charge injection blocking layer, for example, Al ₂ O ₃ ,
A barrier layer made of an electrically insulating material such as SiO ₂ , SiN _x or polycarbonate may be provided, or a charge injection blocking layer and a barrier layer may be used together. The photoconductive layer is made of, for example, a-Si containing hydrogen atoms and halogen atoms, and optionally contains a substance controlling conductivity different from that used in the charge injection blocking layer. The layer thickness of the photoconductive layer is preferably
Desirably, the thickness is 30 Å to 10 μm, more preferably 40 Å to 80 μm, and optimally 50 Å to 50 μm. The surface protective layer is composed of, for example, SiC _x , SiN _x , etc.
The layer thickness is preferably 30 Å to 30 μm, more preferably
It is desirable that the thickness be 40 Å to 20 μm, most preferably 50 Å to 10 μm. Hereinafter, the present invention will be explained in more detail based on specific examples. Example 1, Comparative Example 1 Among the apparatuses outlined in FIGS. 1 and 2,
A photoconductive member was fabricated by the method of the present invention using an apparatus and a substrate having the following shape factors. [Shape factor] R ₁ = 80 mm R ₂ = 250 mm (R ₁ / R ₂ = 0.32) R ₃ = 12 mm R ₃ = 0.07 (R ₂ − R ₁ ) R ₄ = 220 mm R ₄ − R ₁ = 0.82 (R ₂ -R ₁ ) The discharge conditions and raw material gas for forming the deposited film are as follows. Lamination order of deposited film Raw material gas used Film pressure (μm) Charge injection blocking layer SiH ₄ , B ₂ H ₆ 0.6 Photoconductive layer SiH ₄ 20 Surface protection layer SiH ₄ , C ₂ H ₄ 0.1 Aluminum cylinder temperature: 250℃±5 Deposition chamber internal pressure: 0.3 Torr Discharge frequency: 13.56 MHz Deposited film formation rate: 8 Å/sec to 20 Å/sec Discharge power: 0.18 W/cm ² Gas flow rate: 200 m/s Gas flow rate: Charge injection Blocking layer SiH ₄ 200SCCM B ₂ H ₆ SiH 200ppm relative to ₄ Photoconductive layer SiH ₄ 200SCCM Surface protection layer SiH ₄ 10SCCM CH ₄ 200SCCM Stability of discharge during deposited film formation, gas leak prevention, manufactured photoconductive layer Yield of parts, charging ability,
Sensitivity and image defects when using the photoconductive member were evaluated by the following evaluation methods. [Evaluation method] Stability of discharge: Insert a plasma branch probe into the upper observation window and track changes over time in the emission intensity of SiH during film formation. When the luminescence intensity immediately after the start is set as 100, the variation in the luminescence intensity after that is expressed numerically. Gas leak prevention: Insert the sampling tube into the gauge port attached to the feed-through collar at the bottom of the deposition furnace and connect it to the He leak detector. Once immediately before film formation, when switching between charge injection blocking layer formation and photoconductive layer formation, and when switching between photoconductive layer/surface layer,
After the surface layer was formed, a leak check was performed by spraying He 40 times, once each time. Yield: Ten photoconductive members were repeatedly produced under the same conditions and inspected for variations in quality (charging ability, sensitivity, image defects) from lot to lot. Charging ability: The surface potential of the drum was measured at three points, 30 mm from the upper and lower ends and at the center, while the drum was being rotated in a copying machine and the amount of charge was constant. Uniformity of sensitivity: Charging was performed in the same manner as described above, and the surface potential was measured under a constant exposure dose. Image defect: Made by Canon Inc., modified so that each photoconductive member can be installed on a photosensitive drum of any diameter.
Install it on the 400RE copying machine and print the image.
−3 All image defects in the form of white dots on paper (0.3mmφ
(above) were measured. These evaluation results are shown in Table 1. For comparison, a photoconductive member was produced in the same manner as above, except that a conventional device was used in which gas was introduced toward the substrate and discharged while rotating the substrate (Comparative Example 1). The above evaluations were carried out in the same manner, and the results are shown in Table 1.

[Table] Examples 2-1 to 2-3, Comparative Examples 2-1 and 2-2
(Lower limit of R ₁ /R ₂ , upper limit of R ₃ /R ₂ - _{R 1} ) A photoconductive member was produced using the same equipment conditions as in Example 1, except that the outer diameter R ₁ of the substrate was changed as shown below. A similar evaluation was conducted. R ₁ =30, 50, 120, 160, 180mm The results are shown in Table 2-1. Examples 3-1 to 3-4, Comparative Examples 3-1 and 3-2
(Upper and lower limits of R ₁ / R ₂ ) Change the diameter R ₃ of the gas introduction pipe to 3 mm, and adjust the inner diameter of the reaction tank.
A photoconductive member was produced under the same conditions as in Example 1, except that R ₂ and the gas introduction tube arrangement diameter R ₄ were changed as shown below, and the same evaluation was performed.

[Table] The results are shown in Table 2-1. Examples 4-1 to 4-3, Comparative Example 4 (upper limit of R ₅ /R ₂ -R ₁ ) Light was applied under the same conditions as Example 1 except that the diameter R ₃ of the gas introduction pipe was changed as shown below. A conductive member was produced and evaluated in the same way. R ₃ =8, 15, 25, 30mm The results are shown in Table 2-1. Examples 5-1 to 5-2, Comparative Example 5 (R ₄ −R ₁ /R ₂ −
Lower limit of _R1 ) A photoconductive member was produced under the same conditions as in Example 1, except that the diameter _R4 of the gas introduction tube was changed as shown below, and the same evaluation was performed. R ₄ =120, 170, 220mm The results are shown in Table 2-1. Examples 6-1 to 6-5, Comparative Examples 6-1 and 6-2
(Upper and Lower Limits of Flow Rate) A photoconductive member was produced under the same conditions as in Example 1, except that the diameter of the gas introduction hole was changed and the gas flow rate was changed as shown below, and the same evaluation was performed. Flow rate = 1.0, 2.0, 10, 2×10 ² , 10 ³ , 10 ⁴ , 2×
10 ⁴ m/s The results are shown in Table 2-2. Examples 7-1 to 7-4, Comparative Examples 7-1 and 7-2
(Upper and Lower Limits of Flow Rate) A photoconductive member was produced under the same equipment conditions as in Example 1, except that the silane gas flow rate during production of the photoconductive tank was changed as follows, and the same evaluation was performed.

[Table] The results are shown in Table 2-2. From Table 2-1 and 2, each shape factor of the device, flow rate,
It has been found that if any one of the flow rates deviates from the claimed range, the result will be equal to or inferior to Comparative Example 1 in terms of comprehensive evaluation, and it is important to satisfy all the claimed ranges at the same time. I understand.

【table】

〔Effect of the invention〕

According to the present invention, the uniformity of film formation is maintained by the plasma CVD method without rotating the substrate. Further, the stability of glow discharge is increased, and a deposited film having uniform and excellent characteristics can be formed.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing a state in which a substrate is attached to an apparatus that can be used in the method of the present invention, and Fig. 2 illustrates and explains the position of installing a temperature sensor that can come into contact with the substrate in the apparatus of Fig. 1. Figure 3 is a schematic diagram showing the apparatus shown in Figure 1 with an internal holder for the substrate, and Figure 4 is a conceptual diagram for explaining a conventional deposited film forming apparatus equipped with a rotation mechanism. It is a diagram. FIG. 5 is a sectional view showing the relationship between R ₁ , R ₂ , R ₃ , R ₄ , and 1/2 (R ₂ −R ₁ ) of the film forming apparatus used in the present invention. DESCRIPTION OF SYMBOLS 1... Reaction tank container, 3... Container bottom plate, 4... Substrate pedestal, 5... Cylindrical conductive substrate, 6... Top lid or gate, 8, 8... Gas introduction pipe, 9, 9, 9
...Gas introduction hole, 12...Matching box,
13... Gas exhaust pipe, 14... Resistance heating element, 3
1, 32, 33...Temperature sensor, 41...Internal holder.

Claims (1)

[Scope of Claims] 1. A cylindrical substrate is housed in a cylindrical reaction tank that functions as an electrode with its axes substantially aligned, and a gas introduction tube having a gas introduction hole is provided between the reaction tank and the substrate. A plurality of gas inlets are arranged substantially parallel to the axis of the base body and at approximately equal intervals along a concentric circle of the axis so as to satisfy the following three equations, and the flow velocity from the gas introduction hole to the gas introduction hole is 1.5 to 1.5. ×10 ⁴ m/s, flow rate 80~
1. A method for forming a deposited film, which comprises introducing a gas for forming a deposited film to a rate of 1200 SCCM, keeping the base stationary, and performing glow discharge to form a deposited film on the base. 0.2≦R ₁ /R ₂ ≦0.8 1/2 (R ₂ - R ₁ ) ≦ R ₄ - _{R 1} R ₃ ≦ 1/6 (R ₂ - R ₁ ) R ₁ : Outer diameter of substrate R ₂ : Reaction tank Inner diameter R ₃ : Outer diameter R ₄ of the gas introduction tube: Diameter 2 of a concentric circle with the base body formed by the arrangement of the gas introduction tubes and passing through the center of each gas introduction tube The gas introduction hole opens in the direction of the base body The method for forming a deposited film according to claim 1. 3. The deposited film forming method according to claim 1, wherein the gas introduction hole opens toward the inner surface of the reaction tank.