JPS6383278A - Device for forming functional deposited film by microwave plasma cvd method - Google Patents

Abstract

PURPOSE:To steadily form the functional deposited film with high efficiency by the title method by providing a gaseous atmosphere sealing means having specified surface roughness between a micro-wave introducing window for introducing microwave energy and the wall of a vacuum vessel. CONSTITUTION:The microwave 106 is introduced into the vacuum vessel through the microwave introducing window 102 consisting of a microwave transmitting substance, and the functional deposited film is formed on a substrate in the vacuum vessel by the microwave plasma CVD method. At this time, a material having <=3.2 S surface roughness is used for a gaseous atmosphere keeping gasket 103 to be used for sealing the gap between the wall surface 101 of the vacuum vessel and the microwave introducing window 102. For example, when the microwave introducing window 102 is made of an alumina ceramic, an O ring of aluminum is preferably used as the gasket 103. By this method, a good-quality deposited film can be stably formed on a long and large-sized substrate at a high film forming rate.

Description

Detailed Description of the Invention (Technical field to which the invention pertains) The present invention relates to a film deposited on a substrate, particularly a functional film, particularly a semiconductor device, a photosensitive device for electrophotography, a line sensor for human power imaging, an imaging device, a photovoltaic film, etc. The present invention relates to an apparatus for forming functional deposited films such as amorphous semiconductors used in power devices and the like.

(Description of Prior Art) Conventionally, semiconductor devices, photosensitive devices for electrophotography, line sensors for image input, imaging devices, photovoltaic elements,
Amorphous silicon, such as amorphous silicon compensated with hydrogen or/and halogen (e.g. fluorine, chlorine, etc.) (hereinafter referred to as 'a-5t (H,
) Marked as J. ) have been proposed, and some of them have been put into practical use.

These deposited films are produced using the plasma CVD method, which is a method in which a raw material gas is decomposed by direct current, high frequency, microwaves, or glow discharge to form a thin deposited film on a substrate such as glass, quartz, stainless steel, or aluminum. It is known that it can be formed by, and various devices for this purpose have been proposed.

By the way, recently, the plasma CVD method using microwave glow discharge decomposition (hereinafter referred to as r MW-PCVIl method) has been attracting attention at the industrial level, and the MW=
An apparatus for forming a deposited film by the PCVD method typically has an apparatus configuration shown in the schematic cross-sectional view of FIG. 3.

In FIG. 3, 301 indicates the entire reaction vessel, and 302
303 is a vacuum introduction window made of a dielectric material such as alumina ceramics or quartz; 30A is a microwave waveguide for transmitting microwaves; 305 is a microwave power source; 306 is a valve in an exhaust device (not shown). 307 is a ring-shaped raw material gas supply pipe that communicates with a raw material gas supply source (not shown);
08 is a substrate holding plate, 309 is a substrate, 310 is a substrate heating heater, 311 is a plasma generation region, and 312 is a microwave.

Note that the vacuum container 302 generally has a cavity resonator structure that resonates with the oscillation frequency of the microwave power source 305 in order to start the discharge by self-assisted discharge without using a discharge trigger or the like.

Formation of a deposited film using such an apparatus is performed in the following manner. That is, the inside of the vacuum container 302 is connected to the exhaust pipe 30.
At the same time, the substrate 309 is heated and maintained at a predetermined temperature by a substrate heater 310. Next, if an amorphous silicon deposited film is to be formed, for example, silane gas,
Raw material gas such as hydrogen gas is released into the vacuum chamber 302 through a plurality of gas discharge holes 307'' opened in the raw material gas supply pipe.At the same time, the microwave power source 3
Microwaves 312 having a frequency of 500 Hz or more, preferably 2.45 GHz, are generated from 0.05 to 2.45 GHz, and the microwaves are introduced into the vacuum container 302 through the waveguide 304 and the microwave introduction window 303. In this way, the raw material gas introduced into the vacuum container 302 is excited by the microwave energy and dissociated, producing neutral radical particles, ion particles, electrons, etc., which react with each other to form the substrate 3.
A deposited film is formed on the surface of 09.

However, the conventional functional deposited film forming apparatus using the MW-PCVD method as described above shows a certain level of film forming performance when the film forming area is small and the film forming rate is slow. When attempting to increase the speed and increase the area of the substrate, there is a problem in that the quality of the deposited film that is formed deteriorates.

In particular, when attempting to rapidly form a relatively thick deposited film on a large-area substrate such as an electrophotographic photoreceptor, it is difficult to consistently and stably obtain a deposited film with good characteristics. It is.

(Object of the Invention) The present invention overcomes the above-mentioned problems in the conventional deposited film forming apparatus using the MW-PCVD method, and provides semiconductor devices, photoreceptor devices for electrophotography, line sensors for manual imaging, and image pickup devices. Provides an apparatus that makes it possible to regularly and highly efficiently form functional deposited films as element structures used in devices, photovoltaic elements, various other electronic elements, optical elements, etc. using the MW-PCVD method. The purpose is to

That is, the main object of the present invention is to form a relatively thick deposited film at 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 that makes it possible to regularly form a deposited film having good film quality.

Another object of the present invention is to form a functional deposited film with excellent mass productivity, high quality, and excellent electrical, optical, or photoconductive properties by the MW-PCVD method. The goal is to provide equipment.

[Structure and effects of the invention]

The inventor of the present invention solved the above-mentioned problems in the conventional MW-PCVD deposited film forming apparatus and conducted extensive research to achieve the object of the present invention.
Problems with deposited film forming equipment using the CVD method are that when the microwave energy used for high-speed film formation is large, or when the microwave is introduced for a long time, (+) microwave (iN) Structure of the microwave introduction window; Causes include the fact that the microwave itself or the space between the reflective surface of the microwave introduction window and another reflective surface becomes a cavity resonator for the microwave to be introduced, resulting in a portion of the microwave energy being consumed. It was found that this was largely due to the fact that the temperature near the microwave introduction window could rise to over 500°C in some cases.

That is, the microwave introduction window in the above-mentioned conventional functional deposited film forming apparatus using the MW-PCVD method is generally made of a material that maintains a gas atmosphere and transmits microwaves, such as quartz or alumina ceramics. The window made of the microwave-transparent material is connected to the wall of the vacuum vessel through a gasket made of rubber such as Python or a gasket made of metal such as copper or aluminum, as in the case of a normal vacuum seal. However, when using a rubber gasket, the gasket material itself deteriorates due to the heat generated by the temperature rise, and external gas (air) can enter the vacuum container.
The quality of the deposited film deteriorates due to the contamination of the deposited film. In addition, when using a metal gasket, the difference in thermal expansion coefficient between the microwave-transparent material and the gasket causes the sealing surface to shift when the temperature rises, deteriorating the gas atmosphere retention performance, and causing air to enter and cause deposits to build up. This results in a decrease in the film quality of the film.

In order to prevent temperature rise near the microwave introduction window,
A method for cooling the microwave introduction window has been proposed, but since microwaves generate a distribution of electric lines of force depending on the mode at the time of introduction, for example, when introducing microwaves in circular T E// mode, The above problem cannot be solved simply by cooling the microwave, because the temperature locally increases only at the two diametrical ends of the microwave introduction window along the electric field of the microwave. It also became clear that

The present invention has continued research based on these findings, and has found that in order to form a deposited film of high quality stably on a long substrate at high speed in a deposited film forming apparatus using the microwave plasma CVD method, it is necessary to We found that it is essential to have a sealing means that does not deteriorate its ability to retain a gas atmosphere even when heated, and this sealing means is made by optimizing the material that makes up the gasket and the surface properties of the microwave-transparent material that comes into contact with the gasket. We have reached the conclusion that this can be achieved by

The apparatus for forming a functional deposited film using the microwave plasma method of the present invention was completed based on the above-mentioned knowledge, and it maintains a vacuum or gas atmosphere when bonding the microwave introduction window to the wall of the vacuum container. The surface roughness of the surface of the microwave transparent material constituting the microwave introduction window that comes into contact with the gasket is set to 3.2 RM.
8 or less, optimally 0.8 RMAX or less.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The deposited film forming apparatus using the microwave plasma CVD method of the present invention will be explained in detail below with reference to the embodiments of the drawings, but the deposited film forming apparatus of the present invention is not limited thereto.

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

In the figure, 101 is the wall surface of the vacuum container, 102 is a microwave introduction window 103 made of a microwave transparent material, is a gasket for maintaining a gas atmosphere, 104 is a microwave introduction window,
Reference numeral 105 indicates a microwave plasma space, and 106 indicates a microwave.

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

In addition, as a gasket for maintaining a gas atmosphere, the constituent material of the gasket is selected depending on the microwave-transmitting substance, but if the microwave introduction window is made of alumina ceramic, the gasket may be 0 where the contact surface with the microwave transparent material is made of aluminum
It is preferable to use a ring, and in particular, a ring having a structure having an elastic core or the like inside the aluminum coating and having an elastic restoring force is most suitable in terms of seal reliability and durability.

FIG. 2 is a perspective view schematically showing a functional deposited film forming apparatus using a microwave CVD method, which is suitable for manufacturing a photoreceptor drum for electrophotography, and shows the area near the microwave introduction window in the apparatus. The configuration is shown in FIG. In FIG. 2, 201 is a vacuum container, 202 is a microwave introduction window made of a microwave transparent material, 203 is a microwave waveguide, 204 is a microwave, 205 is an exhaust chamber, 206 is a drum-shaped substrate, and 207 is a plasma. The respective areas of occurrence are shown. Note that the plasma generation region 207 is
It has a microwave cavity resonant structure surrounded by the microwave introduction window 202 and the base bodies 206, 206, etc. arranged concentrically, and efficiently absorbs the energy of the introduced microwaves.

The apparatus shown in FIG. 3 is suitable for mass production of electrophotographic photosensitive drums because a plurality of drum-shaped substrates are arranged concentrically around the plasma generation area.

The raw material gas used to form the deposited film by the apparatus of the present invention is one that is excited and speciated by high frequency or microwave energy, and undergoes chemical interaction to form the desired deposited film on the substrate surface. Any one can be adopted, but for example, a-3l ()
l, Gasified materials can be used. These source gases may be used alone or in combination of two or more. Also,
These raw material gases may be used after being diluted with an inert gas such as He or Ar. Furthermore, a-3t (
H, It can be mixed with a diluent gas and introduced into the reaction chamber.

The substrate may be conductive, semiconductive, or electrically insulating, and specific examples thereof include metal, ceramics, glass, and the like. 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.

In addition, when forming a deposited film, the pressure inside the reaction chamber is set to 5 X 1O-6 Torr or less, preferably I X 1O-6 Torr or less before introducing the raw material gas, and the pressure inside the reaction chamber is set to 5 X 1O-6 Torr or less before introducing the raw material gas. lXl0-2
~I Torr, preferably 5 x 10-2 ~IT
It is desirable to set it to orr.

Note that in forming a deposited film using the apparatus of the present invention, the raw material gas is normally introduced into the reaction chamber without prior treatment (excitation speciation) as described above, where it is excited speciation by microwave energy and chemically generated. This is carried out by causing interaction, but when using two or more types of raw material gases, it is also possible to make one of them into an excited species in advance and then introduce it into the reaction chamber.

〔Example〕

Hereinafter, the formation of a functional deposited film using the apparatus of the present invention shown in Fig. 1.2 will be specifically explained using Examples and Comparative Examples, but the present invention is not limited thereto. .

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

First, the inside of the vacuum container 201 is evacuated via the exhaust pipe 205, and the cylindrical bases 206, 206,
It was heated and maintained at a predetermined temperature using a built-in heater (not shown), and was constantly rotated at a desired rotational speed using a drive motor (not shown).

To these places, raw material gases such as silane gas (Si84), hydrogen gas (+12), diborane gas (B2H6), etc. are fed into the vacuum container 201 under the conditions shown in Table 1 through a raw material gas supply pipe (not shown). IX 1O-2T.

It was discharged while maintaining the degree of vacuum below rr. Next, the circumference f
Microwaves with an i number of 2.45 GHz are introduced into the plasma generation region 207 through the waveguide 203 and the introduction window 202 made of a microwave-transparent material, and the cylindrical substrates 20B, 2
06...A charge injection blocking layer, a photosensitive layer, and a surface layer were successively formed on the drum to obtain a photosensitive drum having a blocking structure.

In this example, the surface properties of the contact surface with the gasket of alumina ceramics (purity 99.996, dielectric constant 10.5, alumina particle size 20μ), which is a microwave transparent material, are as shown in Table 2. Four different types were used. When the surface roughness of the microwave-transparent material was particularly small, such as 0.8S or less, processing was performed by lapping.

When the photosensitive drum prepared as described above was installed in a copying machine NP 7550 manufactured by Canon Co., Ltd. and an image was output, the results shown in Table 2 were obtained.

Table 2 shows the difference in image quality of the prepared photosensitive drums depending on the gasket covering material.

Regarding image quality, we mainly investigated image blurring that occurs when air is contained as an impurity in the film.

At this time, 30f of air is applied to the alumina ceramics! ,7
We also checked cases where the product was cooled and cases where it was not cooled. As a cooling method, means such as flowing liquid nitrogen were also used, but air cooling example 2 A photoreceptor drum was made in the same manner as in the example except that quartz was used as the microwave transparent material. When comparing the image properties of the prepared photoreceptor drums, it was found that Example 1
The result was the same.

From these results, if the surface roughness of the microwave transparent material is 3.2S or less, microwave plasma CVD can be performed.
It was found that a functional deposited film with excellent properties and no practical problems could be obtained by this method.

Furthermore, it has been found that if the surface roughness is set to 0.8S or less, a functional deposited film with excellent properties that does not pose any practical problems can be obtained without using other means such as cooling.

According to the present invention, especially when alumina ceramics is used as a microwave transparent material, the surface property is 3.23.
It has also been found that in order to achieve 0.8S, the alumina particle size needs to be 100μ or less, and in order to achieve 0.8S, the alumina particle size needs to be 20μ or less.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of the vicinity of the microwave introduction window. FIG. 2 is a schematic perspective view of an apparatus for forming an amorphous silicon photosensitive drum using a microwave plasma CVD method. FIG. 3 is a schematic cross-sectional view of an apparatus for forming a deposited film on a flat substrate by microwave plasma CVD. In the figure, lOl... Vacuum container mural, 102... Microwave transparent material, 103... Gasket, 10
4...Suppress, 105...Microwave plasma space, 106...Microwave, 201...
...Vacuum container, 202...Microwave introduction window, 2
03...Microwave waveguide section, 204...Microwave, 205...Exhaust pipe, 206...
Drum-shaped substrate, 207...Microwave plasma generation area, 301...Reaction vessel, 302...
Vacuum container, 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 body, 310...Base heating heater, 311...
...Plasma generation area, 312...Microwave Figure 1 Figure 2 Figure 3

Claims (1)

[Scope of Claims] A sealed vacuum container, means for holding a substrate for forming a functional deposited film in the vacuum container, means for supplying raw material gas into the vacuum container, means for evacuating the inside of the vacuum container,
and means for generating microwave discharge plasma in the vacuum container. a microwave introduction window and a gas atmosphere sealing means, and a surface roughness of the surface of the microwave transparent material that comes into contact with the gas atmosphere sealing hand is 3.2S or less. Functional deposited film forming device using microwave plasma CVD method.