JP2553337B2 - Functional deposited film forming apparatus by microwave plasma CVD method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a deposited film on a substrate, particularly a functional film, particularly a semiconductor device, an electrophotographic photosensitive device, an image input line sensor, an imaging device, and a photovoltaic device. The present invention relates to an apparatus for forming a functional deposited film such as an amorphous semiconductor used for a power element or the like.

[Description of Prior Art]

Conventionally, amorphous silicon such as hydrogen or / and halogen (as a device member used for a semiconductor device, an electrophotographic photosensitive device, an image input line sensor, an imaging device, a photovoltaic device, various other electronic devices, optical devices, etc. For example, amorphous silicon (hereinafter referred to as “a-Si (H,
X) ”. ) Have been proposed, and some of them have been put to practical use.

Then, such a deposited film is formed by the plasma CVD method, that is,
It is known that the raw material gas is decomposed by direct current or high frequency, microwave, glow discharge, and is formed by a method of forming a thin film deposition film on a substrate such as glass, quartz, stainless steel, or aluminum. Various devices have been proposed.

By the way, recently, a plasma CVD method by microwave glow discharge decomposition (hereinafter, referred to as "MW-PCVD method") has been attracting attention at an industrial level, and a method for forming a deposited film by the MW-PCVD method has been attracting attention. The device typically has a device configuration shown in the schematic sectional view of FIG.

In FIG. 3, reference numeral 301 denotes the entire reaction vessel, 302 is a vacuum vessel, 303 is a microwave introduction window formed of a dielectric material such as alumina ceramics or quartz, 304 is a microwave waveguide for transmitting microwaves, and 305 is Microwave power supply, 3
Reference numeral 06 is an exhaust pipe communicating with an exhaust device (not shown) through a valve (not shown), 307 is a ring-shaped source gas supply pipe communicating with a source gas supply source (not shown), 308 is a substrate holding plate, 3
Reference numeral 09 denotes a substrate, 310 a substrate heater, 311 a plasma generation region, and 312 a microwave.

Since the vacuum container 302 can start discharge by self-excited discharge without using a discharge trigger or the like, it is generally configured to have a cavity resonator structure that resonates at the oscillation frequency of the microwave power source 305. .

The formation of the deposited film by such an apparatus is performed as follows. That is, the inside of the vacuum container 302 is evacuated through the exhaust pipe 306, and the base 309 is heated and held at a predetermined temperature by the base heater 310. Next, through the source gas supply pipe 307, in the case of forming an amorphous silicon deposited film, for example, a source gas such as silane gas or hydrogen gas is provided with a plurality of gas emission holes 307 opened in the source gas supply pipe. It is discharged into the vacuum container 302 through Simultaneously with this, a frequency of 500 MHz was output from the microwave power source 305.
A microwave 312 of z or more, preferably 2.45 GHz, is generated, and the microwave 312 is introduced into the vacuum container 302 through the waveguide 304 and the microwave introduction window 303. Thus, the introduced raw material gas in the vacuum container 302 is excited by the energy of microwaves and dissociates to generate neutral radical particles, ionic particles, electrons and the like, which react with each other to form the substrate 30.
A deposited film is formed on the surface of 9.

However, the above-described conventional functional deposited film forming apparatus by the MW-PCVD method has a predetermined film forming performance when the film forming area is small and the film forming speed is slow, but the same apparatus is used for film forming. When attempting to increase the speed and increase the basic area, there is a problem in that the quality of the deposited film that is formed deteriorates.

In particular, when a relatively thick volume film is to be formed at a high speed on a large-area substrate such as a photoconductor for electrophotography, it is difficult to consistently obtain a deposited film with good characteristics in a stable manner. Is.

[Object of the Invention] The present invention overcomes the above-mentioned problems in the deposition film forming apparatus by the conventional MW-PCVD method as described above, and is a semiconductor device, a photoconductor device for electrophotography, a line sensor for image input, and imaging. We provide an apparatus that can constantly form a functionally deposited film as an element member used for devices, photovoltaic elements, various other electronic elements, optical elements, etc. by the MW-PCVD method at a high rate. The purpose is to do.

That is, a main object of the present invention is to form a relatively thick deposited film at a high speed on a long substrate such as an electrophotographic photoreceptor in an apparatus for forming a functional deposited film by the MW-PCVD method. Another object of the present invention is to provide an apparatus capable of constantly forming a deposited film having a good film quality.

Another object of the present invention is excellent mass productivity, high quality,
An object of the present invention is to provide an apparatus capable of forming a functional deposited film having excellent electrical, optical or photoconductive properties by the MW-PCVD method.

[Constitution / Effect of Invention]

The present inventor has solved the above-mentioned problems in the deposited film forming apparatus by the conventional MW-PCVD method and has conducted earnest research to achieve the object of the present invention. Problems in the forming apparatus include (i) plasma generated by microwaves when microwave energy used for high-speed film formation is large or when microwaves are introduced for a long time. (Ii) Part of the introduced microwave is absorbed by the microwave permeable substance forming the microwave introduction window, (iii) the structure of the microwave introduction window itself, or the microwave. Microwave energy is consumed between the reflection surface of the wave introduction window and the other reflection surface, and a part of the microwave energy is consumed. Introduction window Edges in some cases been found to be due largely to become heated to above 500 ° C..

That is, the microwave introduction window in the above-mentioned conventional functional deposited film forming apparatus by the MW-PCVD method is generally formed of a substance that retains a gas atmosphere such as quartz and alumina ceramics and transmits microwaves. The window made of the microwave permeable material is a body rubber gasket such as Viton, as in the case of a normal vacuum seal.
Alternatively, it is connected to the wall of the vacuum container through a metal gasket such as copper or aluminum, but when a rubber gasket is used, the material of the gasket itself deteriorates due to the heat due to the temperature rise, and When the external gas (air) is mixed in, the quality of the deposited film deteriorates. In addition, when a metal gasket is used, the sealing surface shifts when the temperature is raised due to the difference in the coefficient of thermal expansion between the microwave permeable material and the gasket, which deteriorates the gas atmosphere retention performance and causes air to accumulate. This is where the quality of the film deteriorates.

In order to prevent such a temperature rise in the vicinity of the microwave introduction window, a method of cooling the microwave introduction window is proposed.However, since microwaves generate electric field lines distribution depending on the mode at the time of introduction, for example, When the microwave is introduced in the circular TE ₁₁ mode, only two diametrically opposite ends of the microwave introduction window are locally heated along with the electric field of the microwave, so that the microwave is simply cooled. It turns out that the above problem cannot be solved only by performing.

The present invention has been further studied based on these findings, and in order to stably deposit a high-quality deposited film at a high speed on a long substrate in a deposited film forming apparatus by a microwave plasma CVD method, We obtained the knowledge that a sealing means that does not deteriorate the gas atmosphere holding capacity even when heated is indispensable, and the sealing means optimizes the material forming the gasket and the displayability of the microwave permeable substance in contact with the gasket. We have reached the conclusion that can be achieved by.

The present invention has been completed based on the above findings. A functional deposited film forming apparatus by a microwave plasma CVD method of the present invention is a vacuum container (which can be evacuated) that can be substantially sealed, a means for holding a functional deposited film forming substrate in the vacuum container, A functional deposited film forming apparatus by a microwave plasma CVD method having a means for supplying a raw material gas into a vacuum container, and a means for exhausting the inside of the vacuum container, wherein the vacuum container is at least partially of the vacuum container. A wall having a microwave introduction window made of a microwave permeable material for introducing microwave energy provided through a sealing means, and the surface of the microwave permeable material in contact with the sealing means The surface roughness is 3.2 S or less.

The deposition film forming apparatus by the microwave plasma CVD method of the present invention will be described in detail below with reference to embodiments of the drawings, but the deposition film forming apparatus of the present invention is not limited thereto.

FIG. 1 is a schematic cross-sectional view in the vicinity of a microwave introduction window of a deposited film forming apparatus by the microwave plasma CVD method of the present invention.

In the figure, 101 is a wall surface of a vacuum container, 102 is a microwave introducing window made of a microwave permeable material, 103 is a gasket for maintaining a gas atmosphere, 104 is a microwave introducing window, 105 is a microwave plasma space, and 106 is a microwave. Are shown respectively.

In the present invention, a dielectric material such as alumina ceramics or quartz is used as the microwave transparent material forming the microwave introduction window.

Further, as the gasket for maintaining the gas atmosphere, the constituent material of the gasket is selected and used according to the microwave permeable substance, but if the microwave introduction window is made of alumina ceramic, as the gasket, It is preferable to use an O-ring whose contact surface with the microwave permeable material is made of aluminum. Particularly, a structure having an elastic core or the like inside the aluminum coating and having an elastic restoring force ensures the sealing and durability. Is the best from.

FIG. 2 is a perspective view schematically showing a functional deposited film forming apparatus by a microwave CVD method, which is suitable for manufacturing a photoconductor drum for electrophotography, and shows the vicinity of a microwave introduction window in the apparatus. The structure is as shown in FIG. In FIG. 2, 201 is a vacuum container, 202 is a microwave introduction window made of a microwave permeable material, 203 is a microwave waveguide, 204 is microwave, 205 is an exhaust officer, 206 is a drum-shaped substrate, and 207 is plasma. The generation areas are shown respectively.
The plasma generation region 207 has a microwave cavity resonance structure surrounded by the microwave introduction window 202 and the bases 206, 206, ... Absorbs efficiently.

The apparatus shown in FIG. 3 has a plurality of drum-shaped bases arranged on a concentric circle around the plasma generation region, and is therefore suitable for mass production of electrophotographic photosensitive drums.

The source gas used for forming the deposited film by the apparatus of the present invention is of a kind that forms excited deposits on the surface of the substrate by excited species by high frequency or microwave energy and chemical interaction. Any material can be adopted as long as it is a-Si (H,
X) In the case of forming a film, specifically, those in a gas state such as silanes and halogenated silanes in which hydrogen, halogen, or hydrocarbon is bonded to silicon, or those which can be easily gasified. A gasified product can be used. One of these raw material gases may be used,
Alternatively, two or more kinds may be used in combination. In addition, these raw material gases may be diluted with an inert gas such as He or Ar before use. Furthermore, the a-Si (H, X) film can be doped with a p-type impurity element or an n-type impurity element, and the source gas containing these impurity elements as constituents can be used alone or as described above. It can be introduced into the reaction chamber by mixing with the raw material gas or / and the diluting gas.

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

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

In the deposition film formation by the apparatus of the present invention, normally, as described above, the raw material gas is introduced into the reactant without pretreatment (excitation seeding), where the seed gas is excited and seeded by the energy of the microwave, and chemical reaction is performed. It is performed by causing interaction, but when using two or more source gases,
It is also possible to pre-excite one of them and then introduce it into the reaction chamber.

〔Example〕

Hereinafter, formation of a functional deposited film using the apparatus of the present invention shown in FIGS. 1 and 2 will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited thereto. .

Example 1 In this example, alumina ceramics was used as the microwave permeable substance, and an aluminum-coated O-ring was used as the gasket.

First, the inside of the vacuum container 201 is evacuated through the exhaust pipe 205, and is heated and maintained at a predetermined temperature by a heater (not shown) built in the cylindrical substrates 206, 206, ... (Not shown) was used to constantly rotate at a desired rotation speed.

A raw material gas such as silane gas (SiH ₄ ), hydrogen gas (H ₂ ), diborane gas (B ₂ H ₆ ), etc. is evacuated to such a place through a raw material gas supply pipe (not shown) under the conditions shown in Table 1. It was discharged into the container 201 while maintaining a vacuum degree of 1 × 10 ^-2 Torr or less. Next, a microwave of frequency 2.45 GHz is applied to the waveguide 2
03 and a cylindrical substrate 206, 20 introduced into the plasma generation region 207 through an introduction window 202 made of a microwave permeable substance.
A charge-injection blocking layer, a photosensitive layer, and a surface layer were successively formed on top of each other to obtain a blocking-type photosensitive drum.

In this example, alumina ceramics (purity 99.9%, relative dielectric constant 10.
5, 4 types of alumina having a particle size of 20 μ) whose surface properties of the contact surface with the gasket were changed as shown in Table 2 were used. Surface roughness of microwave permeable material, especially surface roughness of 0.
Lapping finishing was performed for those with a size of 8S or less.

When the photosensitive drum created as described above was installed in Canon Copier NP7550 and an image was output,
The results are shown in the table.

Table 2 shows the difference in the image quality of the photosensitive drum thus prepared with respect to the coating material of the gasket. As for the image quality, the image deletion mainly generated when air was contained as an impurity in the film was examined.

At this time, it was confirmed that the alumina ceramics was wiped with air at a rate of 30 / min for cooling and for not cooling.
As a cooling method, a means such as flowing liquid nitrogen was used, but the same effect as cooling by air was obtained.

Example 2 A photoconductor drum was prepared in the same manner as in Example 1 except that quartz was used as the microwave permeable substance, and the image properties of the photoconductor drums prepared were compared. became.

From these results, it was found that by setting the surface roughness of the microwave permeable substance to 3.2 S or less, a functional deposited film with excellent characteristics can be obtained without any practical problems by the microwave plasma CVD method. .

Further, it was also found that by setting the surface roughness to 0.8 S or less, a functional deposited film with excellent characteristics that does not hinder practical use without using other means such as cooling can be obtained.

According to the present invention, particularly when alumina ceramics is used as the microwave permeable substance, in order to achieve the surface property 3.2S, the particle diameter of alumina is 100 μm or less, or
It was also found that the particle size of alumina must be 20 μm or less to achieve 0.8S.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view near the microwave introduction window. FIG. 2 is a schematic perspective view of an apparatus for forming an amorphous silicon photosensitive drum by the microwave plasma CVD method. FIG. 3 is a schematic sectional view of an apparatus for forming a deposited film on a flat substrate by the microwave plasma CVD method. In the figure, 101 ... mural of vacuum vessel, 102 ... microwave permeable material,
103 ... Gasket, 104 ... Hold, 105 ... Microwave plasma space, 106 ... Microwave, 201 ... Vacuum container, 202 ... Microwave introduction window, 203 ... Microwave waveguide section, 204 ... Micro Wave, 205 ... Exhaust pipe, 206 ... Drum-shaped substrate, 207 ... Microwave plasma generation region, 301 ...
… Reaction vessel, 302 …… Vacuum vessel, 303 …… Microwave introduction window, 304 …… Waveguide, 305 …… Microwave power supply, 306 ……
Exhaust pipe, 307 ... Raw material gas supply pipe, 308 ... Substrate holding plate,
309 ... Base, 310 ... Base heater, 311 ... Plasma generation area, 312 ... Microwave

Claims (1)

(57) [Claims] 1. A substantially sealed vacuum container, a means for holding a substrate for forming a functional deposited film in the vacuum container, a means for supplying a raw material gas into the vacuum container, and an exhaust in the vacuum container. A functional deposited film forming apparatus by a microwave plasma CVD method having means for introducing microwave energy provided in at least a part of the vacuum vessel through a sealing means on a wall of the vacuum vessel. It has a microwave introduction window made of a microwave permeable substance, and the surface roughness of the surface of the microwave permeable substance that contacts the sealing means is 3.2 S or less. An apparatus for forming a functional deposited film by the microwave plasma CVD method, which is characterized by: