JPH04247877A - Deposited film forming device - Google Patents

Abstract

PURPOSE:To provide the deposited film forming device which can form deposited films having high quality with decreased defects. CONSTITUTION:This device has a reaction vessel in which a reduced pressure can be maintained, a means for disposing plural base bodies so as to enclose a discharge space in the vessel, a gas introducing section which is so introduced as to parallel with the base bodes in the central position of the discharge space and is used to introduce gaseous raw materials, a microwave introducing means and a means for applying electric fields between a part of the gaseous raw material-introducing section and the base bodies. The gaseous raw material- introducing section is made into a multi-pipe structure and has an inside pipe 23 and an outside pipe 22. The surface of the outside pipe has 5 to 200mum roughness in ten point average roughness and the parts of the outside pipe near gas release holes 24 are formed of ceramic materials.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to films deposited on a substrate, particularly functional films, particularly semiconductor devices, photoreceptor devices for electrophotography, line sensors for image input, photographic devices,
The present invention relates to a deposited film forming apparatus for forming an amorphous deposited film used in photovoltaic devices and the like by microwave plasma CVD.

0002

[Prior Art] Conventionally, amorphous silicon, such as hydrogen or/and halogen (e.g. fluorine,
Amorphous deposited films such as amorphous silicon compensated with chlorine, etc.) have been proposed, and some of them have been put into practical use.

Conventional methods for forming such a deposited film include a sputtering method, a method of decomposing the source gas by heat (thermal CVD method), and a method of decomposing the source gas by light (optical CVD method).
D method), a method of decomposing a source gas using plasma (plasma CVD method), and many other methods are known. Among them, plasma CVD method, that is, direct current or high frequency
The method of forming a thin film-like deposited film on a substrate such as glass, quartz, heat-resistant synthetic resin film, stainless steel, aluminum, etc. by decomposing it by microwave glow discharge, etc. is currently known as the method of forming an amorphous silicon deposited film for electrophotography. Practical use is progressing very well, and various devices have been proposed for this purpose. In particular, in recent years, a plasma CVD method using microwave glow discharge decomposition, that is, a microwave plasma CVD method, has been attracting industrial attention as a deposited film forming method.

[0004] The microwave plasma CVD method has advantages over other methods in terms of high deposition rate and high raw material gas utilization efficiency. One example of microwave plasma CVD technology that takes advantage of these advantages is U.S. Patent Nos. 4 and 5.
No. 04,518. The technology described in this patent uses microwave plasma C at a low pressure of 0.1 Torr.
The VD method is used to obtain a high quality deposited film at a high deposition rate.

[0005] Furthermore, a technique for improving the utilization efficiency of raw material gas by microwave plasma CVD method was disclosed in Japanese Patent Application Laid-open No.
It is described in the publication No.-186849. The technology described in this publication is summarized as follows: A base body is arranged to surround a microwave energy introduction part to form an internal chamber (i.e., a discharge space), thereby greatly increasing raw material gas utilization efficiency. It is something.

Furthermore, Japanese Patent Laid-Open No. 61-283116 discloses an improved microwave technique for manufacturing semiconductor components. That is, the publication discloses that an electrode (bias electrode) is provided in the discharge space to control the plasma potential, and a desired voltage (bias voltage) is applied to the bias electrode to deposit a film while controlling ion bombardment on the deposited film. The present disclosure discloses a technique for improving the properties of a deposited film in this manner.

[0007] In such a microwave plasma CVD apparatus, an improvement of the gas introduction part was disclosed in Japanese Patent Application Laid-Open No. 63-57779.
No. 63-230880. The publication describes a method in which raw material gas is introduced into the discharge space from between cylindrical substrates, and by improving the shape of the raw material gas introduction part into a comb shape or a triangular prism, the raw material gas can be efficiently introduced into the plasma generation area. A technique has been disclosed that makes it possible to improve the deposition rate of a deposited film by introducing the method into the method. Furthermore, Japanese Patent Laid-Open No. 2-53073 discloses that a gas introduction section is arranged in the discharge space to introduce raw material gas, and a bias voltage is applied to the gas introduction section to improve the electrical characteristics of the deposited film. A technique has been disclosed that makes it possible to improve this.

These prior art techniques have made it possible to produce relatively thick photoconductive materials with reasonably high deposition rates and efficient raw material gas utilization. Examples of conventional deposited film forming apparatuses improved in this way are shown in FIGS. 4, 5, and 6. FIG. 4 is a schematic longitudinal cross-sectional view of this conventional device, and FIG. 5 is a schematic cross-sectional view taken along line AA' in FIG.
FIG. 6 is a schematic vertical sectional view of the raw material gas introduction section (single tube structure).

An exhaust pipe 4 is integrally formed on the side surface of the cylindrical reaction vessel 1, and the other end of the exhaust pipe 4 is connected to an exhaust device (not shown). Waveguides 3 are attached to the upper and lower surfaces of the reaction vessel 1, respectively, and the other end of each waveguide 3 is connected to a microwave power source (not shown). A dielectric window 2 is hermetically sealed at the end of each waveguide 3 on the reaction vessel 1 side. Six cylindrical substrates 5 on which deposited films are formed are arranged in parallel to each other so as to surround the center of the reaction vessel 1. Each cylindrical base 5 is held by a rotating shaft 8 and heated by a heating element 7. A rotary shaft 8 rotates via a reduction gear 10 driven by a motor 9, and the cylindrical base 5 rotates about its central axis in the generatrix direction. A space surrounded by each cylindrical base 5 and each dielectric window 2 in the reaction vessel 1 is a discharge space 6, and a gas pipe 16 is connected to the cylindrical base 5 at approximately the center of the discharge space 6. A raw material gas introduction section 11 is provided. The gas pipe 16 is made of an electrically insulating material, and the other end is connected to a raw material gas supply source (not shown) through a gas inlet 15. A cable 13 from the bias power supply 12 is introduced into a gas pipe 16 in the reaction vessel 1 through an introduction terminal 14 and connected to the source gas introduction section 11 .

When using this apparatus to form a deposited film for an electrophotographic photoreceptor, for example, the inside of the reaction vessel 1 is evacuated to 1×10 −7 Torr or less, and then the heating element 7 is evacuated.
The cylindrical substrate 5 is heated and maintained at a desired temperature. For example, when forming an amorphous silicon deposited film, a raw material gas such as silane gas is introduced from the gas inlet 15, passed through the gas pipe 16, and discharged from the raw material gas inlet 11 into the discharge space 6. At the same time, the bias power supply 12 applies, for example, a DC bias voltage to the raw material gas introduction section 11 . Further, microwaves having a frequency of 500 MHz or more, preferably 2.45 GHz, are made to enter the reaction vessel 1 through the waveguide 3 and the dielectric window 2. the result,
Glow discharge starts in the discharge space 6, the source gas is excited and dissociated, and a deposited film is formed on the cylindrical substrate 5. At this time, by driving the motor 9 to rotate the cylindrical substrate 5, a deposited film can be formed over the entire circumference of the cylindrical substrate 5.

[0011]

SUMMARY OF THE INVENTION By using such a conventional method for forming a deposited film, it has become possible to obtain a deposited film having practical characteristics and uniformity at a certain deposition rate. Furthermore, if the interior of the reaction vessel was cleaned strictly, it was possible to obtain a deposited film with fewer defects to some extent. However, these conventional deposited film forming methods are not suitable for producing products that require a relatively thick deposited film over a large area, such as electrophotographic photoreceptors, especially in areas where the deposition rate is high. There remains the problem that it is difficult to obtain a deposited film with a high yield (high yield) that satisfies the requirements for electrical properties and has few image defects during image formation using an electrophotographic process.

[0012]Furthermore, electrophotographic apparatuses are currently required to have even higher image quality, higher speed, and higher durability. As a result, electrophotographic photoreceptors are required to further improve their optical properties and electrical properties, and to extend their durability under all environments while maintaining high charging ability and high sensitivity.

In addition, in recent years, improvements have been made to the optical exposure system, developing device, transfer device, etc. in electrophotographic devices in order to improve the image characteristics of electrophotographic devices. There is now a need for improved characteristics. In particular, as a result of improvements in image resolution, there is a need to reduce image defects in the form of white or black dots, commonly referred to as "pockets," and in particular to reduce "pockets" of infinitesimal size, which were not much of a problem in the past. It has become possible to do so. In particular, most of the causes of "pochi" are abnormal growth of membranes called spherical protrusions, and it is extremely important to reduce their occurrence. Furthermore, when a deposited film is formed on a substrate at high speed, such as in an electrophotographic photoreceptor, a bias electrode is provided in the discharge space in order to improve the electrical characteristics of the deposited film, and a voltage is applied to this electrode for the purpose of controlling the plasma potential. It is important to apply an electric field in the discharge space in this way, but the number of spherical protrusions that occur increases rapidly depending on the voltage.

Further, in order to obtain uniformity of the deposited film formed, the internal pressure is maintained low during the formation of the deposited film, or the diameter and position of the raw material gas discharge holes are adjusted. By keeping the internal pressure low during the formation of the deposited film, the mean free path of electrons, ions, and active species in the plasma increases, resulting in uniform properties. Further, by adjusting the hole diameter, hole position, etc. of the raw material gas discharge holes, the raw material gas can flow out so as to be uniformly distributed within the discharge space, and uniformity of characteristics can be obtained. At this time, more uniformity can be obtained by reducing the hole diameter of the raw material gas discharge hole and adjusting the hole position and number of holes. However, if the internal pressure is kept low or the hole diameter is made small, the number of spherical protrusions will increase.

[0015] As described above, with conventional methods, it has been difficult to deposit at high speed a deposited film that has good electrical properties, good uniformity even over a large area, and has few spherical protrusions.

An object of the present invention is to overcome the problems in the conventional deposited film forming apparatus using the microwave plasma CVD method as described above, and to improve the production of semiconductor devices, photoreceptor devices for electrophotography, and line sensors for image input. , imaging device,
Photovoltaic devices, various other electronic elements,
It is an object of the present invention to provide a deposited film forming apparatus capable of forming a deposited film with good characteristics for use as an element member of an optical element at high speed by microwave plasma CVD.

An object of the present invention is to provide a deposited film forming apparatus that can reduce defects and form a high quality deposited film at high speed, particularly when forming an amorphous silicon deposited film having a relatively thick film thickness, by microwave plasma CVD method. It's about doing.

[0018]

[Means for Solving the Problems] The present invention provides a reaction vessel that can be depressurized, a means for arranging a plurality of base bodies in the vessel so as to surround a discharge space, and a plurality of base bodies arranged at the center of the discharge space in parallel with the base bodies. Microwave plasma CVD deposition having a gas introduction part for introducing a raw material gas and a means for introducing microwave energy, and for generating plasma and forming a deposited film on the substrate. In the film forming apparatus, the gas introduction section has multiple pipes,
The innermost pipe of the multiplex pipe is connected to a raw material gas supply source,
Each tube constituting the multiple tube is provided with a plurality of gas release holes, and the surface facing the discharge space of the outermost tube of the source gas introduction section has a ten-point average roughness of 5 μm or more and 200 μm or more.
The surface of the gas discharge hole of at least the outermost tube has an unevenness of μm or less, and is formed of a ceramic material, and has means for applying an electric field between at least a portion of the raw material gas introduction part and the base body. This is a deposited film forming apparatus.

[0019] The source gas introduction section has a multi-tube structure, each tube constituting the multiple tubes is provided with a gas release hole, and the surface of the source gas introduction section facing the discharge space is roughened, and at least the surface is roughened. The vicinity of the provided gas discharge hole is made of alumina ceramic, and the present invention has a means for applying a bias voltage between the source gas introduction part and the base body.The operation of the present invention is as follows. The same effect can be obtained whether the multiple tube is a double tube, a triple tube or more.

One of the factors that affects the yield of electrophotographic photoreceptors is image defects caused by abnormal growth of deposited films called spherical protrusions. It has been confirmed that the cause of these spherical protrusions is that dust such as dirt and dust adhering to the substrate triggers their growth. For this reason,
The substrate before film formation is precisely cleaned and placed in a reactor in a dust-controlled environment such as a clean room.
It is designed to prevent dust from adhering to the base as much as possible. However, the dust that causes the spherical protrusions is not only dust that adheres to the substrate before the start of film formation, but also dust that is generated from very slight film peeling during film formation. The deposited film is not only deposited on the substrate but also on the structures of the reactor, such as the inner wall of the vacuum chamber and the raw material gas inlet. In particular, in the devices shown in FIGS. 4 and 5, the discharge space is surrounded by the base, and the raw material gas introduction part is installed in the center of the discharge space, so that the film peeling from there may occur on the base. The effect on the deposited film is very large. In particular, since the raw material gas introduction section is constantly exposed to electric discharge, a deposited film having a thickness three times or more is formed on the surface of the substrate, which is about 1/3 of the area exposed to electric discharge. Furthermore, the surface of the raw material gas inlet is at a very high temperature due to the microwave plasma and bias current. Therefore, the film is in a state where peeling is very likely to occur.

[0021] The number of spherical protrusions generated by this dust increases by increasing the bias voltage. In microwave plasma CVD equipment, it is important to provide a bias electrode in the discharge space and apply voltage to this electrode for the purpose of controlling the plasma potential in order to improve the electrical characteristics of the deposited film. When an electric field is applied within the discharge space, the number of spherical protrusions increases rapidly depending on the voltage. The reason for this is that when dust is present in the plasma, the dust is charged to a potential corresponding to the floating potential, so that a Coulomb force acts between it and the surface of the substrate at ground potential, causing it to be electrostatically attracted. This floating potential increases in proportion to the plasma potential, so as the bias voltage increases, the Coulomb force increases, the adhesion of dust to the substrate surface increases, and the number of spherical projections increases.

The number of spherical projections increases even when the internal pressure during the formation of the deposited film is kept low or when the diameter of the gas release hole is made small. Furthermore, when the flow rate of the raw material gas is increased in order to accelerate the deposition rate, the number of spherical protrusions generated also increases. The reason for this is that either method results in an increase in the discharge pressure when the source gas flows out from the source gas discharge hole into the discharge space. When the discharge pressure increases, the deposited film near the gas discharge hole tends to peel off due to the influence of the pressure, which causes dust to be generated. Furthermore, the generated dust gains kinetic energy due to the discharge pressure and is blown into the discharge space. Therefore, as the discharge pressure increases, the kinetic energy of the blown film increases, increasing the probability that the blown film will reach the substrate. Therefore, the number of spherical projections increases.

According to the present invention, the raw material gas is supplied by the raw material gas supply source and first introduced into the inner pipe of the double pipe. The gas discharge holes provided in the inner tube are not directly exposed to plasma because the outer tube is located outside the inner tube. Therefore, the source gas does not decompose around this gas discharge hole, and no deposited film is formed there. Therefore, even if the discharge pressure increases as a result of reducing the diameter of the gas discharge hole, the number of spherical protrusions on the deposited film formed on the substrate does not increase. Therefore, the hole diameter of the gas discharge hole can be made small, so that the distribution of the raw material gas can be made more uniform by the inner tube. The source gas passes between the inner tube and the outer tube and is discharged into the discharge space from the gas discharge hole provided in the outer tube. At this time, as mentioned above, the raw material gas is uniformly distributed in the axial direction by the inner tube, so there is no need to strictly adjust the gas discharge hole in the outer tube, and the hole diameter of the gas discharge hole in the outer tube can be adjusted relatively. It can be made larger. For this reason, the pressure in the space between the inner tube and the outer tube can be considerably lower than the pressure inside the tube when a single tube structure is used for the raw material gas introduction section, so the pressure in the space between the inner tube and the outer tube can be considerably lower. The pressure can be lowered while the distribution of the source gas is more uniform. Therefore, even if the flow rate of the source gas is increased or the internal pressure of the reaction vessel is kept low during the formation of the deposited film, it is possible to suppress an increase in the number of spherical protrusions. Here, regarding the number of gas release holes provided in each tube constituting the multi-pipe, if more gas release holes are provided in the outer tube than in the inner tube, then
Furthermore, it is preferable because the pressure in the space between the inner tube and the outer tube can be lowered.

Furthermore, in the present invention, the surface of the source gas inlet facing the discharge space has a ten-point average roughness of 5 μm or more.
The surface of the raw material gas introduction part of the deposited film deposited on the surface of the raw material gas introduction part by having an unevenness of 00 μm or less and forming at least the surface of the gas release holes provided on the surface with alumina ceramics, for example. Excellent adhesion with. Therefore, dust caused by film peeling from the surface of the source gas introduction part during film formation can be reduced.

As described above, a thick deposited film is formed on the surface of the source gas inlet. Particularly when producing an electrophotographic photoreceptor with a relatively thick deposited film, a deposited film with a thickness of 100 μm or more is formed on the surface of the raw material gas introduction part. Furthermore, since the temperature of the outer tube is increased, the thermal expansion of the outer tube increases. Under these conditions, the ten-point average roughness of the surface is 5μ.
If it is less than m, sufficient adhesion cannot be obtained between the deposited film deposited on the surface of the source gas introduction section and the surface of the source gas introduction section. However, on the other hand, the ten-point average roughness of the surface is 20
If it is larger than 0 μm, film peeling will occur on the convex portions.

Furthermore, the area near the gas discharge hole is a part where the surface shape changes rapidly due to its structure, and as mentioned above, it is also affected by the discharge pressure due to the blowing of the raw material gas, so film peeling occurs. easy. Since alumina ceramic has a lower coefficient of thermal expansion than metal, by forming the vicinity of the gas release hole with alumina ceramic, the influence of film peeling due to thermal expansion can be reduced.

Furthermore, since alumina ceramics are chemically stable and have a low equilibrium vapor pressure, they do not have any adverse effect on the quality of the formed bulk film. In the present invention, the material disposed near the gas release hole is not limited to alumina ceramics, and materials having similar characteristics to the alumina ceramics described above may also be used. Examples of materials other than alumina ceramics include MgAl2O4, AlN, BN, Ti2O3
etc.

Furthermore, in the present invention, a bias voltage can be applied between the source gas introduction section and the substrate. By adjusting the bias voltage, the impact of ions on the deposited film on the substrate can be controlled, and the properties of the deposited film can be improved. Further, by applying a bias voltage, deposition of a film on the outer wall of the source gas introduction section is suppressed. As described above, the deposited film forming apparatus of the present invention makes it possible to reduce the generation of dust while maintaining excellent film quality, and to reduce image defects caused by spherical protrusions that occur on the deposited film.

Furthermore, by increasing the bias voltage and increasing the raw material gas flow rate, it has become possible to significantly improve the deposition rate while maintaining the current level of image defects and electrical characteristics. Furthermore, the selectivity of the hole diameter of the gas release holes has been increased, and since the internal pressure during the formation of the deposited film can be maintained low, it has become possible to form the deposited film with a more uniform thickness and various properties.

Furthermore, the internal pressure during the formation of the deposited film is lowered,
It has become possible to improve electrophotographic characteristics such as sensitivity while maintaining the current level of image defects. The reason for this is
By lowering the internal pressure, the mean free path of the active species increases,
Therefore, the energy possessed by the active species when deposited on the substrate increases. This is thought to be because the surface mobility on the substrate increased, the rearrangement of atoms progressed further, and the internal strain of the deposited film was relaxed.

There is no particular restriction on the shape of the raw material gas inlet, but if there is a sharp edge, the deposited film attached to the outside will peel off. Are suitable. When the raw material gas introduction part is a double pipe, the shape of the inner pipe is preferably cylindrical, and the cross-sectional diameter is preferably 30% or more and 70% or less of the outer pipe. Although there is no particular restriction on the length of the raw material gas inlet, it is preferable to set the length to 90% or more and 110% or less of the cylindrical substrate in view of the uneven thickness of the deposited film.

The material for the raw material gas inlet is preferably one that has an electrically conductive surface, can withstand high temperatures, and has a certain degree of poor thermal conductivity, but the following are practically preferable. For example, stainless steel, Ni, Cr, Mo, In, Nb, Te
In the present invention, metals such as , V, Ti, Pt, Pd, and Fe, alloys thereof, or glasses and ceramics whose surfaces are subjected to conductive treatment are generally used.

There are no particular limitations on the means for roughening the surface of the raw material gas inlet, but in practice, thermal spraying of metal or blasting means of spraying a blast material at high pressure is preferred.

There are no particular restrictions on the means for forming the vicinity of the gas release hole with a ceramic material, but high melting point metal method,
Coating methods using vapor deposition methods and thermal spraying means are preferred.

The position of the source gas inlet may be set anywhere as long as the center of the source gas inlet is within 20% of the shortest distance from the center of the discharge space to the cylindrical base. Preferably, it is installed at the center of the discharge space.

[0036] Furthermore, when the raw material gas introduction part has a cylindrical shape, the diameter of its outermost periphery is preferably about 4 to 25% of the diameter of the discharge space, and about 4 to 14% of the diameter of the discharge space. It is even more preferable.

The diameter of the gas discharge hole in the outer tube of the raw material gas introduction part is preferably about 0.4 to 2.5 mm, and preferably about 0.6 to 1.5 mm.
More preferably, the thickness is about mm.

The number of gas discharge holes in the outer tube of the raw material gas inlet is 0.09 per unit surface area of the outer tube.
~0.31 pieces/cm2 is preferable, and 0.14~0
．． About 27 pieces/cm2 is more preferable.

The substrate on which the deposited film is formed is made of a conductive material or a material whose surface has been subjected to conductive treatment. For example, stainless steel, Al, Cr, Mo, Au, In, Nb, Te,
Metals such as V, Ti, Pt, Pd, and Fe, alloys thereof, synthetic resins such as polycarbonate whose surfaces are conductively treated, glass, ceramics, paper, and the like are usually used.

When the shape of the base is cylindrical, the diameter of the base is not particularly limited, but practically it is 20 mm or more and 500 m.
m or less, and the length is 10 mm or more, 1000 mm
The following degree is preferable.

In the case of cylindrical substrates, the distance between the substrates is preferably about 1 mm or more and 50 mm or less in order to stably maintain the discharge space, and the number of substrates may be any number as long as the discharge space can be formed. is preferably 3 or more, more preferably 4 or more.

[0042]

Embodiments Next, embodiments of the present invention will be described with reference to the drawings.

As shown in FIGS. 4 and 5, an exhaust pipe 4 is integrally formed on the side surface of the reaction vessel 1, which is cylindrical and has a vacuum-tight structure, and the other end of the exhaust pipe 4 is connected to a vacuum pump or the like. Not connected to an exhaust system. Waveguides 3 are attached to the center portions of the upper and lower surfaces of the reaction vessel 1, respectively. The waveguide 3 consists of a rectangular section extending from a microwave power source (not shown) to the vicinity of the reaction vessel 1, and a circular section inserted into the reaction vessel 1, and includes a stub tuner (
(not shown) and is attached to a microwave power source (not shown) along with an isolator (not shown). At the end of each waveguide 3 on the reaction vessel 1 side, a dielectric window 2 made of a material that can transmit microwave energy with little loss and maintain vacuum tightness is provided. Specifically, the dielectric window 2 is made of alumina (Al2O3), aluminum nitride (AlN), boron nitride (BN), silicon nitride (SiN), silicon carbide (SiC), silicon oxide (Si
It is made of materials such as beryllium oxide (BeO), polytetrafluoroethylene, and polystyrene. The dielectric window 2 is hermetically sealed in close contact with the cylindrical portion of the waveguide 3 in order to maintain the atmosphere within the reaction vessel 1 . Six cylindrical substrates 5 on which deposited films are formed are arranged in parallel to each other so as to surround the center of the reaction vessel 1. Each cylindrical base body 5 is held by a rotating shaft 8, and a cylindrical heating element 7 is coaxially disposed inside the base body 5.
is arranged, and is heated from the inside by the heating element 7. The rotating shaft 8 is rotatably attached to the reaction container 1 , and one end is connected to the motor 9 via a reduction gear 10 . Therefore, by driving the motor 9, the cylindrical base body 5 can be rotated about its central axis in the generatrix direction.

A space surrounded by each cylindrical substrate 5 and each dielectric window 2 in the reaction vessel 1 is a discharge space 6, and microwaves are emitted from each waveguide 3 through each dielectric window 2 to the reaction vessel 1. When the microwave enters the discharge space 6, glow discharge due to the microwave mainly occurs in the discharge space 6. It is preferable that the discharge space 6 has a cavity resonant structure for microwaves. discharge space 6
A source gas inlet 11, which will be described later and which is connected to a gas pipe 16, is provided in the center of the cylindrical base 5 in parallel with the cylindrical base 5. The gas pipe 16 is made of an electrically insulating material, and the other end is connected to a raw material gas supply source (not shown) through a gas inlet 15. A cable 13 from the bias power supply 12 is introduced into a gas pipe 16 in the reaction vessel 1 through an introduction terminal 14 and connected to the source gas introduction section 11 . As a result, a bias voltage can be applied between each cylindrical substrate 5 and the raw material gas introduction section 11.

Next, the source gas introduction section 11 will be explained. The raw material gas introduction section 11 has a rough surface, is made of alumina ceramic near the gas discharge holes provided on the surface, and has a multi-tube structure with both ends closed. The innermost tube is connected to the gas tube 16. Each tube constituting the multiple tube is provided with a plurality of gas discharge holes, so that the raw material gas flows out from the inside of the tube to the outside. In this case, if the outer tube is provided with more gas release holes than the inner tube, the pressure distribution of the source gas in the discharge space 6 can be made more uniform. This makes it possible to make the characteristics of the deposited film uniform. Further, it is desirable that the positions of the gas discharge holes in the inner tube and the gas discharge holes in the outer tube do not overlap.

An example of the source gas introduction section 11 having a double pipe structure is shown in FIG. In this case, the inner tube 23 and the outer tube 2
2 has a double pipe structure, and the gas pipe 1 is connected by the base 21.
6. Inner tube 23 and outer tube 22
are provided with a plurality of gas discharge holes 25 and 24, respectively, but the number of gas discharge holes is greater in the outer tube 22 than in the inner tube 23. The outer surface of the outer tube 22 is a rough surface, and the surface of the gas discharge hole 24 provided on the surface and the vicinity thereof are made of a ceramic material 26 such as alumina.
It is formed of. FIG. 2 shows an enlarged view of the area around the gas release hole. The raw material gas flowing from the mouthpiece 21 flows into the inner pipe 2.
3. The gas flows out into the discharge space 6 through the gas discharge hole 25, the outer tube 22, and the gas discharge hole 24.

Similarly, FIG. 3 shows an example of the source gas introduction section 11 having a triple pipe structure. In this case, the inner pipe 34
It has a triple tube structure consisting of an inner tube 33 and an outer tube 32, and the base 3
1 to be connected to a gas pipe 16. The inner tube 34, the middle tube 33, and the outer tube 32 are each provided with a plurality of gas discharge holes 37, 36, and 35, and the number of gas discharge holes increases in the outer tube. As in the case of the double tube described above, the surface of the outer tube 32 is rough, and the vicinity of the gas release hole 35 provided on the surface is made of alumina ceramic. The raw material gas flowing from the mouthpiece 31 passes through the inner pipe 34, the gas release hole 37, the middle pipe 33, the gas release hole 36,
The gas flows out into the discharge space 6 through the outer tube 32 and the gas discharge hole 35.

Next, a method of heating the cylindrical substrate 5 will be explained. The cylindrical base 5 is heated by a heating element 7. The heating element 7 may be of any type as long as it has a vacuum specification, and specifically includes a sheath-like wrap heater, a plate heater, an electric resistance heating element such as a ceramic heater, a heat radiation lamp such as a halogen lamp, an infrared lamp, etc. A heating element using a heat exchange means using a body, liquid, gas, etc. as a heating medium may be appropriately selected and used. As the surface material of the heating element 7, metals such as stainless steel, nickel, aluminum, and copper, ceramics, heat-resistant polymer resin, and the like can be used. Alternatively, instead of providing the heating element 7, a heating-only container is provided outside the reaction container, and after the cylindrical substrate 5 is heated there, the cylindrical substrate 5 is transported into the reaction container 1 in a vacuum. A method may also be used. Furthermore, in combination with these means or alone, it is also possible to control the temperature of the cylindrical substrate 5 by the microwave itself used for glow discharge, and in this case, the intensity of the microwave can be changed as necessary. Good too.

Next, the raw material gas will be explained. There are no particular restrictions on the raw material gas for the deposited film, and for example, silane (S
iH4), disilane (Si2H6), other functional deposited film forming raw material gases such as germane (GeH4), methane (CH4), or a mixture thereof.

There is no particular restriction on the diluent gas for the source gas, and examples thereof include hydrogen (H2), argon (Ar), helium (He), and neon (Ne).

[0051] As gases for improving characteristics such as changing the band gap width of the deposited film, ammonia (NH3),
Those containing nitrogen atoms such as nitrogen (N2), oxygen (O2),
Those containing oxygen atoms such as nitrogen oxide (NO) and dinitrogen oxide (N2O), methane (CH4), ethane (C2H6),
Hydrocarbons such as ethylene (C2H4), acetylene (C2H2), propane (C3H8), silicon tetrafluoride (SiF4)
), fluorine compounds such as disilicon hexafluoride (Si2F6), germanium tetrafluoride (GeF4), or a mixed gas thereof can also be used.

Furthermore, the present invention is equally effective even if a dopant gas such as diborane (B2H6), boron fluoride (BF3), or phosphine (PH3) is simultaneously introduced into the discharge space for the purpose of impurity doping.

[0053] There are no particular restrictions on the pressure in the discharge space, but it is 100 mTorr or less, preferably 50 mTorr.
Particularly good results were obtained with good reproducibility in the following cases.

Next, the operation of this embodiment will be explained.

First, the inside of the reaction vessel 1 is evacuated via the exhaust pipe 4 by an exhaust device (not shown), and the pressure is reduced to 1×10 −7
Adjust so that it is below Torr. Next, the cylindrical substrate 5 is heated and maintained at a desired temperature by the heating element 7. For example, when forming an amorphous silicon deposited film, a raw material gas such as silane gas is introduced from the gas inlet 15, passed through the gas pipe 16, and discharged from the raw material gas inlet 11 into the discharge space 6. At the same time, the bias power supply 12
For example, a DC bias voltage is applied to the raw material gas introducing section 11 by using the following steps. Furthermore, a microwave power source (not shown) is used to generate a frequency of 500 MHz or more, preferably 2.45 GH.
A microwave of Z is made to enter the reaction vessel 1 through the waveguide 3 and the dielectric window 2. As a result, a glow discharge starts in the discharge space 6 surrounded by the cylindrical base 5, the source gas is excited and dissociated, and the electric field between the source gas introduction part 11 and the cylindrical base 5 causes the cylindrical base 5 to is constantly subjected to ion bombardment, and a deposited film is formed on the surface of the cylindrical substrate 5. At this time, the rotating shaft 8 is rotated by the motor 9, and the cylindrical substrate 5 is rotated about its central axis in the generatrix direction, so that the deposited film is uniformly formed over the entire circumference of the cylindrical substrate 5.

Next, the results of experiments conducted on the deposited film forming apparatus of this example will be explained.

Example 1, Comparative Examples 1 and 2 In the deposited film forming apparatus shown in FIG. 4, the following material gas inlet was used. Example 1 Double pipe comparative example 1 of the present invention shown in Fig. 1 Double pipe comparative example 2 similar to Example 1 except that alumina ceramic was not used near the gas release hole Single pipe structure shown in Fig. 6, and gas For each sample in which the vicinity of the discharge hole was not made of alumina ceramic (conventional example), a deposited film was formed under the conditions shown in Table 1 while changing the surface roughness (ten-point average roughness, hereinafter referred to as RZ). After taking it out, the number of spherical protrusions occurring on the deposited film was measured. The results are shown in Table 2. The number of spherical protrusions was determined by counting the number of spherical protrusions with a diameter of 20 μm or more per unit area (1 cm x 1 cm) at 10 locations in the circumferential direction at the top, middle, and bottom of the cylindrical base using an optical microscope. . Table 2 shows the results.
Shown below. In Table 2, ◎ indicates the number of spherical protrusions is less than 10; ○ indicates the number of spherical protrusions is 10 or more and less than 20; △ indicates the number of spherical protrusions is 20 or more and less than 30; × indicates the number of spherical protrusions is 30 or more. .

From Table 2, it can be seen that the raw material gas introduction part has a double pipe structure, the surface has a ten-point average roughness of 5 μm or more and 200 μm or less, and the vicinity of the gas release hole provided on the surface is made of alumina ceramic. It can be seen that this significantly reduces the number of spherical protrusions on the deposited film.

[0059]

[Table 1]

[0060]

[Table 2] Example 2 In the deposited film forming apparatus shown in FIG. 4, the double tube of the present invention shown in FIG. Each was prepared under different conditions, and an amorphous silicon electrophotographic photoreceptor was formed on an aluminum cylindrical substrate. At this time, the surface roughness (RZ) of the double tube was set to 7 μm.

The produced electrophotographic photoreceptor was manufactured by Canon Co., Ltd.
A copying machine NP-8550 was installed in an electrophotographic apparatus modified for experimental use, and the following items were measured to evaluate the electrophotographic characteristics of the produced amorphous silicon electrophotographic photoreceptor. Each item was evaluated using the following method.

Charging ability/charging ability unevenness The electrophotographic photoreceptor was installed in the experimental equipment, and +6 kV was applied to the charger.
Corona charging is performed by applying a high voltage of , and the dark area surface potential of the electrophotographic photoreceptor is measured using a surface electrometer. The dark area surface potential was measured every 3 cm from one end of the photoreceptor to the other, and the average thereof was taken as the charging ability. Then, the value farthest from the average value for one photoreceptor was determined, and the deviation of that value from the average value was defined as the charging performance unevenness. The same evaluation was performed on six photoreceptors obtained in one deposition film formation, and the following judgment was made for the one with the largest chargeability unevenness.

◎ means 10V or less, which means very good uniformity. ○ means 2
Δ, which is 0 V or less and has excellent uniformity, is 30 V or less, which poses no practical problem.

Sensitivity/Sensitivity Unevenness After the electrophotographic photoreceptor was charged to a dark area surface potential of 400 V, it was immediately irradiated with a light image. The optical image was generated using a xenon lamp light source, and a constant amount of light was irradiated using a filter, excluding light in the wavelength range of 550 nm or less. At this time, the bright area surface potential of the electrophotographic photoreceptor is measured using a surface electrometer. The bright area surface potential was measured every 3 cm from one end of the photoreceptor to the other end, and the average of the measurements was taken as the sensitivity. Then, the value farthest from the average value for one photoreceptor was determined, and the deviation of that value from the average value was defined as sensitivity unevenness. The same evaluation was performed on six photoreceptors obtained in one deposition film formation, and the following judgment was made for the one with the largest sensitivity unevenness.

◎ is 3V or less and has excellent uniformity; ○ is 6V
Δ, which indicates excellent uniformity, is 10 V or less, which poses no practical problem.

Fine line reproducibility Observe the copy image obtained when copying a test chart made by Canon Co., Ltd. (part number: FY9-9058) consisting of full text on a white background on a document table. We evaluated whether they were connected without any problems. However, if there was unevenness on the image at this time, the entire image area was evaluated and the results for the worst part were shown. The same evaluation was performed on six photoreceptors obtained in one deposition film formation, and the following judgment was made on the worst one among them.

◎: Good ○: There are some breaks △: There are many breaks, but they can be recognized as characters ×: There are some characters that cannot be recognized. FY9-9058) was placed on a document table and the resulting copy image was observed to evaluate the fogging on the white background. However, if there was unevenness on the image at this time, the entire image area was evaluated and the results for the worst part were shown. The same evaluation was performed on six photoreceptors obtained in one deposition film formation, and the following judgment was made on the worst one among them.

◎: Good ○: Slight fogging in some parts △: There is fogging over the entire surface, but it does not interfere with character recognition Part number: FY9-
9042) was placed on a manuscript table and copied, the resulting copy image was observed and the unevenness of shading was evaluated. However, if there was unevenness on the image at this time, the entire image area was evaluated and the results for the worst part were shown. The same evaluation was performed on six photoreceptors obtained in one deposition film formation, and the following judgment was made on the worst one among them.

◎: Good ○: There is a slight difference in shading in some parts △: There is a difference in shading over the entire surface, but there is no problem in practical use FY9-
9073) was placed on a document table and copied, white spots with a diameter of 0.2 mm or less within the same area of the copied image were evaluated. Further, the same evaluation was performed on six photoreceptors obtained by one deposition film production, and the following judgment was made for the worst one among them. ◎: "Particularly good" ○: "Good" △: "No practical problem" ×: "Practical problem" The above evaluation results are shown in Table 4. In Table 4, chargeability,
Regarding the sensitivity and deposition rate, relative evaluations were made for the charging ability, sensitivity, and deposition rate of the electrophotographic photoreceptor whose photosensitive layer was prepared using Condition 1. In other words, the charging ability and sensitivity of the electrophotographic photoreceptor prepared under condition 1 for the photosensitive layer are shown as (A), sensitivity (B), and deposition rate (C) when the photosensitive layer conditions are changed. , deposition rate (D),
As (E) and (F), (Charging ability) = (D)/(A) x 100 (%) (Sensitivity)
=(E)/(B)×100(%)(deposition rate)=(F
)/(C)×100(%).

Example 3 An amorphous silicon photoreceptor was prepared in the same manner as in Example 2 using the triple tube shown in FIG. 3 as the raw material gas inlet.
The evaluation was carried out in the same manner. At this time, the surface roughness of the triple tube (
RZ) was set to 7 μm. The results are shown in Table 4.

Comparative Example 3 An amorphous silicon photoreceptor was prepared in the same manner as in Example 2, using the double tube used in Comparative Example 1 as the raw material gas inlet, and evaluated in the same manner as in Example 2. At this time, the surface roughness (RZ) of the double tube was set to 7 μm. The results are shown in Table 4.

Comparative Example 4 An amorphous silicon photoreceptor was produced in the same manner as in Example 2 using a double tube similar to that in Example 2 for the raw material gas inlet, and evaluated in the same manner as in Example 2. At this time, the surface roughness (RZ) of the double tube was 4 μm. The results are shown in Table 4.

Comparative Example 5 An amorphous silicon photoreceptor was prepared in the same manner as in Example 2, using a single tube structure similar to that in Comparative Example 2 for the raw material gas inlet, and evaluated in the same manner as in Example 2. At this time, the surface roughness (RZ) of the double tube was set to 7 μm. Table 4 shows the results.
Shown below.

From Table 4, it was found that by using the deposited film forming apparatus of the present invention, an electrophotographic photoreceptor with very good uniformity of various properties and with fewer image defects could be produced. Furthermore, by using the deposited film forming apparatus of the present invention,
By increasing the bias voltage and increasing the raw material gas flow rate,
It has become possible to significantly increase the deposition rate while maintaining the current potential characteristics and keeping image defects very good. Furthermore, by lowering the internal pressure during the formation of the deposited film, it has become possible to improve electrophotographic characteristics such as sensitivity while maintaining very good image defects.

[0075]

[Table 3]

[0076]

[Table 4]

[0077]

Effects of the Invention According to the present invention, the requirements for uniform film quality, optical and electrical properties can be met in the production of a relatively thick deposited film of large area, especially in a region where the deposition rate is high, and there are very few defects. It has become possible to consistently and stably produce a small amount of deposited film at a high yield (high yield) and at a very low cost.

Furthermore, according to the present invention, it is possible to produce a deposited film that maintains excellent electrophotographic properties even under poor charging conditions such as high temperature and high humidity, or poor developing conditions such as low temperature and low humidity. became.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of a source gas introduction section in a deposited film forming apparatus of the present invention.

FIG. 2 is an enlarged view of the vicinity of the gas discharge hole of the raw material gas introduction section in FIG. 1;

FIG. 3 is a schematic diagram showing another example of the source gas introduction section in the deposited film forming apparatus of the present invention.

FIG. 4 is a schematic longitudinal sectional view showing parts common to the present invention and a conventional deposited film forming apparatus.

FIG. 5 is a schematic lateral cross-sectional view of the device shown in FIG. 4;

FIG. 6 is a schematic diagram showing a conventional source gas introduction section.

[Explanation of symbols]

1 Reaction vessel 2 Dielectric window 3 Waveguide 4 Exhaust pipe 5 Cylindrical base 6 Discharge space 7 Heating element 8 Rotating shaft 9 Motor 10 Reduction gear 11 Raw gas introduction part 12 Bias power supply 13 Cable 14 Introduction terminal 15 Gas introduction port 16 Gas pipe 21, 31, 41 Base 22, 32 Outer pipe 23, 34 Inner pipe 33 Inner pipe 24, 25, 35, 36, 37, 42 Gas discharge hole 2
6 Ceramic materials

Claims (3)

[Claims] 1. A reaction vessel that can be depressurized, means for arranging a plurality of base bodies in the vessel so as to surround a discharge space, and a source gas disposed at the center of the discharge space so as to be parallel to the base bodies. In a microwave plasma CVD deposited film forming apparatus for forming a deposited film on the substrate by generating plasma, the device has a gas introduction section for introducing gas and a means for introducing microwave energy, and the apparatus includes a gas introduction part for introducing gas and a means for introducing microwave energy, and for forming a deposited film on the substrate by generating plasma. The section has multiple tubes, the innermost tube of the multiple tubes is connected to a raw material gas supply source, each tube constituting the multiple tubes is provided with a plurality of gas release holes, and the raw material gas introduction The surface of the outermost tube facing the discharge space has an unevenness of 5 μm or more and 200 μm or less in ten-point average roughness, and at least the surface of the gas release hole of the outermost tube is formed of a ceramic material, and 1. A deposited film forming apparatus, comprising means for applying an electric field between at least a portion of a source gas introduction section and a substrate. 2. The method for forming a deposited film according to claim 1, wherein the number of gas release holes provided in each tube constituting the multiple tube increases from the inside to the outside of the multiple tube. Device. 3. The multilayer film forming apparatus according to claim 1, wherein the ceramic material is alumina ceramics.