JPS6350479A - Device for forming functional deposited film by microwave plasma cvd method - Google Patents

Abstract

PURPOSE:To steadily form a high-quality functional deposited film on a substrate at a high rate by supplying a raw gas into a vacuum vessel through a gas supply pipe consisting of a dielectric having a specified characteristic, and generating microwave plasma. CONSTITUTION:The substrate 9 is arranged on a holding plate 8 in the vacuum vessel 2 provided with an exhaust pipe 6, and heated by a heater 10 to a specified temp. The raw gas is then supplied from the raw gas supply pipe 7, and discharged from discharge holes 7'. Under such conditions, a microwave 51 from a microwave power source 5 is impressed through a waveguide 4 and a dielectric window 3. Consequently, microwave discharge is generated in the vacuum vessel 2, a plasma generating space 11 is formed in the reaction chamber, and the raw gas is deposited to form a thin film on the substrate 9. In the reaction vessel 1 of the function deposited film forming device by the microwave plasma CVD method of such a structure, the gas supply pipe 7 is formed with a dielectric member having <=10 dielectric constant epsilon and <=0.005 dielectric loss angle tan delta.

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 manual imaging, an imaging device, and a photosensitive film. 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,
Amorphous silicon, such as hydrogen and/or nitrogen (e.g. fluorine, chlorine, etc.), is used as an element member for image input line sensors, imaging devices, photovoltaic elements, and various other electronic elements, optical elements, etc.
amorphous silicon compensated by (hereinafter 'a −S
Written as i (H,X)J. ) have been proposed, and some of them have been put into practical use.

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

By the way, in recent years, the plasma CVD method using microwaves (hereinafter referred to as "r MW-PCVD method") has attracted attention, and several devices for that purpose have been proposed.
Efforts have been made to produce the above-mentioned deposited film on an industrial scale by the CVD method. One such conventionally proposed MW
- An apparatus using the PCVD method typically has a lid-forming structure shown in the schematic cross-sectional view of FIG.

In Fig. 2, 1 indicates the entire reaction vessel, 2 is a vacuum vessel, 3 is a dielectric window such as alumina ceramics or quartz, 4 is a waveguide section for transmitting microwaves, 5 is a microwave power source, and 51 is a A microwave, 6 an exhaust pipe, 7 a ring-shaped source gas supply pipe, 71 a valve, 8 a substrate holding plate, 9 a substrate, 10 a heater, and 11 a plasma generation region.

Note that the vacuum container 2 generally has a cavity resonator structure that resonates with the oscillation frequency of the microwave power source 5 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 as follows. That is, the inside of the vacuum container 2 is evacuated through the exhaust pipe 6, and the substrate 9 is heated and held at a predetermined temperature by the heater 10 built into the substrate holding plate 8.

Next, if an amorphous silicon deposited film is to be formed, for example, silane gas,
A raw material gas such as hydrogen gas is discharged into the reaction vessel 1 through a plurality of gas discharge holes 7', 7', . . . opened in the raw material gas supply pipe. Simultaneously, a microwave 51 with a frequency of 500 MHz or more, preferably 2.45 GHz, is generated from the microwave power source 5, and the microwave passes through the waveguide 4 through the dielectric window 3. Reaction vessel 1
be introduced within. In this way, the raw material gas introduced into the reaction vessel 1 is excited by the microwave energy and dissociated, producing neutral radical particles, ion particles, electrons, etc.
These react with each other to form a deposited film on the surface of the substrate 9.

Incidentally, in such a conventional deposited film forming apparatus using the MW-PCVD method, a metal member such as stainless steel is used as the raw material gas supply pipe. However, when such a gas supply pipe is used, the amount of microwaves reflected on the surface of the gas supply pipe is large, resulting in a large amount of electricity returning to the microwave power source, and as a result, plasma is generated inside the vacuum vessel. There is a problem in that the effective microwave power input into the vacuum container is smaller than the microwave power required to generate plasma, and plasma is not generated efficiently.

In order to solve this problem, it has been proposed to use an elongated electric material such as soda glass as the raw material gas supply pipe, but in such a case, the absorption of microwave power on the surface of the gas supply pipe becomes large and the plasma There is a problem that almost no plasma is generated, or that the resonance conditions within the vacuum vessel are disturbed and the generated plasma disappears midway.

[Purpose of the invention]

The present invention overcomes the above-mentioned problems in the conventional deposited film forming bag chamber by the MW-PCVD method, and provides semiconductor devices, photosensitive devices for electrophotography, line sensors for manual imaging, imaging devices, and photovoltaic devices. Functional deposited films as element components used in devices, various other electronic devices, optical devices, etc.! It is an object of the present invention to provide an apparatus that enables constant and highly efficient formation by the Aw-pcvtt method.

That is, the main object of the present invention is to enable microwaves to be used stably and efficiently without being blocked;
As an element component for semiconductor devices, photosensitive devices for electrophotography, line sensors for image input, imaging devices, photovoltaic elements, various other electronic elements, optical elements, etc. composed of a-5i (H, X) etc. An object of the present invention is to provide an apparatus that allows a useful functional deposited film to be constantly formed with high efficiency by the MW-PCVD method.

Another object of the present invention is to form a functional deposited film by MW-PCV (1 method) that is suitable for mass production, has high quality, and has excellent electrical, optical, or photoconductive properties. The goal is to provide a device that can do this.

[Structure of the invention]

The present invention solves the above-mentioned problems in the conventional deposited film forming apparatus using the MW-PCVD method, and in order to achieve the object of the present invention, the present inventor has conducted extensive research and obtained the following knowledge. This was completed after further research based on the above.

In other words, the present inventor has found that the problems in the conventional MW-PCVD deposited film forming apparatus are largely due to the dielectric properties of the member used as the gas supply pipe. .

The inventor has determined that the microwave power absorbed by the dielectric member has a dielectric constant of 6 and a dielectric loss angle of t.
It was also found that when anδ is assumed, it increases in proportion to the product of ε and tanδ.

Based on this knowledge, the inventor conducted further research and found that when a dielectric material like soda glass (tan δ of 0.06 or more) is used, microwave absorption is large, and microwave absorption at a frequency of 2.45 GHz is Microwave power is only 30cm
It was found that half of the energy is absorbed at the depth of the ocean, and is lost as heat energy.

When such a dielectric member is used, especially when a relatively thick deposited film is to be obtained on a substrate such as in an electrophotographic photosensitive device, it is difficult to efficiently obtain a deposited film having good properties. turned out to be completely impossible.

The present invention was completed based on these findings, and the apparatus of the present invention includes a vacuum container having a sealed film forming chamber, a means for holding a substrate in the film forming chamber, and a gas supply into the film forming chamber. Microwave plasma CVD comprising means for supplying source gas through a tube, means for exhausting the inside of the film forming chamber, and means for generating microwave discharge within the film forming chamber.
The functional deposited film forming apparatus is characterized in that the gas supply pipe has a dielectric constant ε of 10 or less and a dielectric loss angle ta.
It is characterized in that it is made of a dielectric member having nδ of 0.005 or less.

In the apparatus of the present invention having the above configuration, the frequency of the microwave used is 500 MHz or more, preferably 2.45 G)Iz, so the dielectric member used for the gas supply pipe is made of quartz glass, alumina ceramics,
There are Teflon, polystyrene, beryllia, steatite, etc., and these materials transmit microwaves extremely efficiently when the half-life depth of microwave power at a frequency of 2.45 GHz is 1 m or more.

Hereinafter, an apparatus for forming a functional deposited film using the MW-PCVD method of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

A schematic cross-sectional view of a typical example of an apparatus for forming a functional deposited film by the MW-PCVD method of the present invention is the same as that shown in FIG. 1 described above.

In the figure, 1 indicates the entire reaction vessel of the apparatus of the present invention. 2 is
A vacuum container for making the reaction container vacuum-tight, and 3
is a dielectric window made of a material (for example, quartz glass) that can efficiently transmit microwaves into the reaction vessel and maintain vacuum tightness. Reference numeral 4 denotes a microwave waveguide section, which is mainly made of a metal rectangular waveguide, and is connected to a microwave power source 5 via a Miki pillar matching box and an isolator (not shown). Reference numeral 6 denotes an exhaust pipe whose one end opens into the vacuum container 2 and whose other end communicates with an exhaust device (not shown). Reference numeral 8 denotes a holding section for the substrate 9, and 10 denotes a heater for heating and maintaining the substrate 9 at a temperature suitable for forming a deposited film. , 11 is plasma generated in the vacuum container by the microwave 51 transmitted through the dielectric window 3. 7 is a raw material gas supply source (
(not shown), and has a large number of gas discharge holes 7', 7', . . . . The gas supply pipe 7 is a feature of the present invention, and includes:
It is made of a specific dielectric material as mentioned above.

FIG. 2 is a schematic cross-sectional view showing another example of a functional deposited film forming apparatus using the MW-PCV[) method of the present invention, which forms a deposited film on a cylindrical substrate, and is especially suitable for mass production. This made it possible to

That is, in the apparatus shown in FIG. 2, microwave introduction windows connected to microwave generation means are installed in the center of the upper and lower parts of a vacuum container, and microwaves generated by the microwaves transmitted through the microwave introduction windows are installed. The device is characterized in that a plurality of substrate holding means for rotating the substrate are provided in the space surrounding the plasma, and in the figure, 12 is a vacuum container, 13 is a microwave-transparent glass window, and 14 is a microelectrode glass. wave guide, 1
5 is a microwave, 16 is for exhausting the inside of the vacuum container,
An exhaust pipe communicating with an exhaust means (not shown), 17 a conductive cylindrical base, and 18 a gas supply pipe communicating with a raw material gas supply source (not shown). The supply pipe 18 has a large number of gas discharge holes 18', 18'...
have. 19 indicates a plasma space. The plasma space 19 includes a visitor window 13.13 and conductive substrates 17.17.17 arranged in the surrounding space.
It has a microwave cavity resonator structure surrounded by microwaves, which efficiently absorbs the introduced microwave energy.

In the apparatus having the above configuration, gas supply pipes 18, 18,...
. . . is composed of the above-mentioned specific telephone body member, and includes a plurality of gas discharge holes 18' provided on the surface of the gas supply pipe.
1111', 18', . . . are provided so that source gas is emitted toward the plasma generation space 19, as shown in FIG.

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-5iDI,
X) If a film is to be formed, specifically, silanes and halogenated silanes in which hydrogen, halogen, hydrocarbon, etc. are bonded to silicon, or materials that are easily gasified. A gasified product can be used. One type of these raw material gases may be used,
Or 2 f! The above may be used in combination. Further, these raw material gases may be used after being diluted with an inert gas such as He or Ar. Furthermore, a −5t (H,X
) The film can be doped with a p-type impurity element or an n-type impurity element, and a raw material gas containing these impurity elements as a constituent may be used alone or with the aforementioned raw material gas and/or dilution gas. It can be mixed with 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 in the reaction chamber is set to 5 x 10-6 Torr or less, preferably 1 x 10-'Torr or less before introducing the raw material gas, and the pressure in the reaction chamber is lowered when the raw material gas is introduced. I x 10
-2 to I Torr, preferably 5 X 10-2 to I
It is desirable to set it to Torr.

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 done by causing interaction, but when using two or more raw material gases,
It is also possible to make one of them into 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. 2 will be specifically explained using Examples and Comparative Examples, but the present invention is not limited thereto.

Example In this example, a three-layer electrophotographic photosensitive drum was prepared using gas supply pipes made of various materials shown in Table 2.

First, the inside of the vacuum container 12 is evacuated via the exhaust pipe 16, heated and maintained at a predetermined temperature by a heater (not shown) built in the base 17, and the drive motor (
(not shown) was used to constantly rotate at a desired rotation speed.

To these places, raw material gas co-supply pipes 18, 18,...
Through..., silane gas (SiH4), hydrogen gas (
H2), diborane gas (82H8), etc.
Under the conditions shown in the table, 1×10 Tarr
It was discharged while maintaining the following degree of vacuum. Next, frequency 2
．． A 45 GHz microwave is introduced into the plasma space 19 through the waveguide 14 and the microwave-transparent two-body window 13, and a charge injection blocking layer, A photosensitive layer and a surface layer were formed one after another.

When the deposition rate of the photosensitive layer of the photosensitive drum thus obtained was measured and an image was output, the good results shown in Table 3 were obtained. Note that "image quality" indicates the results of examining image density, halftone sharpness, and resolution.

Comparative Example A photoreceptor drum was made under the same conditions as in the previous example, except that the materials of the gas supply pipes 18, 18, ... were changed as shown in Table 4, and the same measurements were taken. As a result of the evaluation, the results shown in Table 5 were obtained.

Table 1 Table 2 [Summary of the effects of the invention] The functional deposited film forming apparatus by the MW-PCVD method of the present invention has a gas supply pipe whose specific electric constant ε is 1O or less and whose dielectric loss angle tan δ is Since it is composed of telephone body members with a diameter of 0.005 or less, a stable plasma space can be generated, and a film can be deposited regularly and at high speed on the substrate. Further, the deposited film formed by the apparatus is dense and has excellent electrical, optical, or photoconductive properties.Furthermore, the present invention provides a deposited film forming apparatus that is highly suitable for mass production. Can be done.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing a typical example of a functional deposited film forming apparatus using the MW-PCVD method, and FIG.
- FIG. 3 is a schematic cross-sectional view showing an example of a mass production apparatus for forming a functional deposited film by the PCVD method, and FIG. 3 is a schematic view showing the state of gas discharge holes provided in the gas supply pipe in FIG. 2. In the figure, 2.12...Vacuum container, 3.13...Dielectric window, 4.14...Wave guide section, 5...Microwave power source 51, 15 ...Microwave, 6.16.
...Exhaust pipe 7.18...Gas supply pipe, 7',
18'...Gas discharge hole, 71...Gas introduction valve, 8...Base holding plate, 9.17...
Substrate, 10... Substrate heating heater, 11.19.
...Plasma generation space Figure 1 Figure 2

Claims (1)

[Claims] A vacuum container having a sealed film forming chamber, a means for retaining gas in the film forming chamber, a means for supplying source gas into the film forming chamber via a gas supply pipe, a means for exhausting the inside of the film forming chamber, and A functional deposited film forming apparatus by a microwave plasma CVD method comprising means for generating microwave discharge in the film forming chamber, wherein the gas supply pipe has a relative dielectric constant ε of 10.
An apparatus for forming a functional deposited film using a microwave plasma CVD method, characterized in that it is constructed of a dielectric member having a dielectric loss angle tan δ of 0.005 or less.