JPH01100275A - Functional deposit film-forming apparatus by microwave plasma cvd method - Google Patents

Abstract

PURPOSE:To homogenize a functional deposit film and also to increase deposition velocity by substituting plural square resonators made of metal having dielectric windows, respectively, on the film-forming chamber side for a part of the peripheral wall surface of the film-forming chamber and supplying a gaseous raw material from the other surface-wall parts. CONSTITUTION:At least two and even-numbered peripheral wall-surface parts, of a film-forming chamber, coaxially facing the central axis of the film-forming chamber are selected. These selected peripheral wall-surface parts are substituted by metallic square cavity resonators 4 located on the film-forming chamber sides and having dielectric windows 3, respectively. Further, a gas is discharged toward respective surfaces of plural substrates 9 through respective gaseous raw material supply pipes 7 in the other peripheral wall-surface parts of the above film-forming chamber. Then, these substrates 9 are allowed to revolve and rotate.

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 photoreceptor device for electrophotography, a line sensor for image input, an imaging device, an optical The present invention relates to an apparatus for forming functional deposited films such as amorphous semiconductor films used in electromotive force devices and the like.

[Description of prior art]

Conventionally, amorphous silicon has been used as an element member used in semiconductor devices, electrophotographic photoreceptor devices, image input line sensors, non-life insurance devices, photovoltaic devices, and various other electronic devices, optical devices, etc. For example, deposited films of amorphous semiconductors such as amorphous silicon (rA-3i(H,X)J) compensated with hydrogen atoms and/or halogen atoms (e.g., fluorine, chlorine, etc.) have been proposed. , some of which have been put into practical use.

Then, such a deposited film is deposited using a plasma CVD method, that is,
The raw material gas is decomposed by direct current, high frequency, or microwave glow discharge, and FIII is deposited on a substrate such as glass, quartz, heat-resistant synthetic resin film, stainless steel, or aluminum.
It is known to be formed by a method of forming a Q-shaped deposited film, and various apparatuses for this purpose have also been proposed.

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

In FIG. 8, 81 indicates the entire vacuum vessel, 82 a microwave introduction window made of a dielectric material such as alumina ceramics or quartz glass, 83 a waveguide,
84 is a microwave, 85 is an exhaust pipe, 86 is a substrate for film formation, and 87 is a film formation chamber (plasma generation chamber).

Formation of a deposited film in a deposited film forming apparatus using such a conventional MW-PCVD method is performed as follows.

That is, the inside of the vacuum container 81 is evacuated via the exhaust pipe 85, and the base 86 is placed on a holder (not shown) for the base.
For example, when forming an amorphous silicon deposited film by heating and maintaining a predetermined temperature with a built-in heater (not shown) through a raw material gas supply means (not shown), , silane gas (SiF4), hydrogen gas (H2), etc., into the film forming chamber 87 of the vacuum container 81.
1X 1 (I2 Torr) or less while maintaining the vacuum level.

Next, for example, a 2.45 GHz microwave 84 is transmitted from the microwave'; The film is introduced into the film forming chamber 87. The film forming chamber 87 has a microwave introduction window 82
It has a microwave resonator structure surrounded by a conductive substrate 86 arranged on the circumference, and efficiently converts and absorbs the introduced microwave energy into plasma.

In this way, the raw material gas introduced into the film forming chamber 87 is excited by the microwave energy and dissociated, producing neutral radical particles, ion particles, electrons, etc., which react with each other to form the surface of the substrate 86. A deposited film is formed on the surface.

By the way, in such a method of forming a deposited film using the MW-PCVD method, the plasma formed is an ionized body, and therefore acts as an absorber or a reflector for microwaves that have the property of spatially propagating inside a dielectric material. This plasma density decreases as the degree of vacuum increases, as the mean free path of charged particles becomes longer. Therefore, by increasing the degree of vacuum during plasma formation, the propagation distance of microwaves can be increased.

However, when attempting to form a deposited film mainly composed of neutral radical particles, the lower limit of the degree of vacuum is on the order of 10-3 Torr. Therefore, when attempting to form a deposited film on a long substrate such as an electrophotographic drum, there is a problem in that it is difficult to generate plasma uniformly over the entire length of the substrate. For this reason, in conventional MW-PCVD equipment, microwave energy is introduced from two locations at the top and bottom ends of the drum.
It makes the plasma uniform.

Furthermore, in the MW-P CVD apparatus having the configuration shown in FIG. 8, since the plasma is surrounded by the base 86, the generated active species can be effectively deposited on the surface of the base. There was a drawback that the deposited film was formed only on a part of the surface (the area exposed to the plasma).

For this reason, in the conventional MW-PCVD apparatus, a deposited film is uniformly formed over the entire surface of the substrate by rotating the substrate 86.

However, since the same part of the substrate surface alternately passes through the deposited film formation area and the formation area, the thickness of the film deposited by the time it goes around and returns to the same position is the same as that of the film exposed to the plasma. There is a problem in that the deposition rate cannot be more than half of that, that is, the deposition rate is reduced to less than half.

Furthermore, when creating a device that requires a large film thickness (for example, 20 μm or more), such as an electrophotographic photoreceptor drum, in order to achieve such a film thickness,
It is necessary to perform the film forming operation by rotating the substrate 76 many times, but in this case, the deposited film that is formed is often in a layered state, and the resultant film is one in which there are many laminated interfaces. There is also the problem that it becomes

In particular, when a large number of lamination interfaces are formed in the photoelectric conversion layer, electron movement is obstructed, and the photoelectric conversion ability is not effectively exhibited, so that the electrophotographic photosensitive drum cannot function satisfactorily.

[Purpose of the invention]

An object of the present invention is to overcome the problems in the conventional devices as described above, and to provide an element member for use in semiconductor devices, electrophotographic photoreceptor devices, photovoltaic devices, various other electronic devices, optical devices, etc. An object of the present invention is to provide an apparatus capable of forming a functional deposited film stably and at high speed by the MW-PCVD method.

That is, the main object of the present invention is to efficiently utilize microwave energy in an apparatus for forming a functional deposited film by the MW-PCVD method to form an amorphous silicon functional film such as an A-3i:H:X film. It is an object of the present invention to provide an optimal apparatus for uniformly depositing a deposited film and at the same time improving the deposition rate.

[Structure and effects of the invention]

The present inventor has conducted intensive research to overcome the aforementioned problems in conventional methods and apparatuses and to achieve the above-mentioned object of the present invention, and has discovered that a part of the wall surface of the peripheral wall of the film-forming chamber of the apparatus concerned. If the apparatus is configured such that the part is replaced with at least two metal rectangular resonators having dielectric windows on the side of the film forming chamber, and the raw material gas is supplied from the wall surface, the substrate is used for electrophotographic photosensitive drums. Even if it has a large area like the base of
It has been found that a desired homogeneous deposited film of uniform thickness can be constantly and stably formed on all of the substrates in the system, and that the above object of the present invention can be efficiently achieved.

The present invention was completed as a result of further research by the present inventor based on this knowledge, and the device of the present invention includes:
In an apparatus for forming a functional deposited film using the MW-PCVD method, at least two and even numbered peripheral wall portions of the film forming chamber coaxially opposing the apparent central axis of the film forming chamber are each It is replaced with a metal rectangular cavity resonator having a dielectric window located on the side of the film forming chamber, and source gas is supplied from other peripheral wall portions of the film forming chamber to a plurality of This is an apparatus for forming a functional deposited film by the MW-PCVD method, which is characterized in that the discharge is directed toward each surface of the substrate.The specific contents of the apparatus having the above configuration are shown in Figures 1 to 3. It will be understood from the illustrated example of the device.

That is, FIG. 1 is a schematic cross-sectional view of one example of a functional deposited film forming apparatus using the MW-PCVD method according to the present invention.
The figure is a perspective view of the example device, and FIG. 3 is a schematic cross-sectional view of the square resonator of the example device.

In the example of the functional deposited film forming apparatus by the MW-PCVD method of the present invention shown in FIGS. 1 and 2, 1 indicates a vacuum container, and the vacuum container has a structure that can be maintained vacuum-tight. . The vacuum vessel 1 has a reaction space 2 in which a substrate (substrate cylinder) 9.9. .

The surrounding wall forming the reaction space 2 has a plurality of metal rectangular resonators 4,4. ... arranged intermittently at equal intervals,
Part or all of the surrounding wall portion located between the rectangular resonators is connected to a raw material gas supply pipe 7 equipped with a valve means (not shown) from a raw material gas supply source (not shown) to supply gas. Air outlet? The structure is such that the raw material gas is discharged to the entire surface of the base 9 through the walls.

IO is a substrate holder equipped with a heater IO' for heating and maintaining the substrate 9 at a predetermined temperature.

Reference numeral 8 denotes a substrate holder support base configured to hold the substrate holder and rotate the substrate 9 placed on the substrate through a drive means (not shown) and simultaneously revolve on the same orbit. It is. In the center of the bottom wall of the vacuum vessel 1 there is an opening 6 for an exhaust pipe (not shown), which communicates with an exhaust device via valve means (currently not shown).

The rectangular cavity resonator 4 used in the example of the functional deposited film forming apparatus by the MW-PCVD method of the present invention shown in FIGS. 1 and 2 is preferably of the type shown in FIG. 3. be. That is, the rectangular cavity resonator 4 has a side wall that is a part of the peripheral wall surface forming the reaction space 2 of the vacuum container 1 and is made of quartz glass, alumina ceramics, beryllia, etc. that allows efficient transmission of microwave power into the reaction space 2. It is a rectangular cavity with a dielectric window 3 made of a material capable of keeping the inside of the system vacuum-tight, and the other walls made of a metal material. The microwave power input side of the rectangular cavity resonator 4 is connected to a microwave power source 5 via a metal rectangular waveguide, a matching box, and an isolator (not shown), which are microwave transmission parts. The other side, that is, the transmission end, has a movable short circuit plate 1) for reflecting the microwave introduced into the square cavity resonator and forming a standing wave in the system. ing. The square cavity resonator 4 thus constructed has a dielectric window 3 on its side wall, and the dielectric window forms the peripheral wall of the reaction space 2 of the vacuum vessel 1. The microwave introduced into the reaction space 2 passes through the dielectric window and enters the reaction space 2, where it decomposes the raw material gas introduced therein and generates plasma. When the density of the plasma generated at this time reaches about IQ"am-', microwave (frequency:
2.45 GHz) is blocked, part of it is used to generate plasma, and part of it is reflected. That is, the generated plasma forms a microwave reflecting wall that acts similarly to a metal wall and acts to generate and maintain standing waves within the square cavity resonator.

Power? The number of rectangular cavity resonators installed may be one if the purpose is to make the plasma act as a reflection wall for microwaves, but in that case, the purpose of acting as this reflection wall is Even if this is achieved, the electric field strength of the standing wave varies in strength at regular intervals in the microwave transmission direction, and the generated plasma will also vary in strength accordingly. The amount of active species contributing to the film increases or decreases depending on the strength of the plasma. For these reasons, the base cylinder 9.9. The films deposited on the respective surfaces of... are non-uniform, with changes in both film thickness and film quality corresponding to the amount of active species generated.

For this reason, the device of the present invention is designed to have a small number (two in total) of the above-mentioned square cavity resonators. In any case, the square cavity resonator shown in FIG. 3 is used. For example, when using two rectangular cavity resonators as shown in FIG. are respectively replaced by dielectric windows 3 of the rectangular cavity resonator 4 shown in FIG. 3 (ie, 4a and 46 in FIG. 1).

In this case, two square cavity resonators shown in FIGS. 3(A) and 3(B) are used as the square cavity resonator 4. Then, for both resonators, adjust the shorting plate 1) so that the phase of one standing wave (E) is λ/4 with respect to that of the other.
(However, λ indicates the wavelength.)
By doing this, the plasma generated in the plasma region A of the reaction space 2 becomes one whose strength is shifted by λ/4 due to the standing waves of each square cavity resonator. As a result, the base cylinders 9,9. The films deposited on the respective surfaces of... will be uniform in both film thickness and film quality.

The second point is verified by the experimental results described below.

That is, in the apparatus shown in FIGS. 1 and 2, 2
As shown by 4a and 4e, square cavity resonators are installed on the peripheral wall of the reaction space 2 of the vacuum vessel 1 at positions coaxially facing the apparent central axis of the film forming chamber. did.

In this experiment, one of the two rectangular cavity resonators is hereinafter represented by 4a, and the other rectangular cavity resonator indicated by 4e is represented by 4b.

Regarding the phase of the standing wave (E), the square cavity resonator 4
a is shown in FIG. 3(A), and the square cavity resonator 4b is shown in FIG. 3(B), which is shifted by λ/4 from the former one.

In the apparatus shown in FIGS. 1 and 2 configured as described above, (1) when only the rectangular cavity resonator 4a is operated, (
2) when only the square cavity resonator 4b is operated, and (3) when the square cavity resonators 4a and 4b are operated. ... A film was formed on the film, and the film thickness and bright/dark conductivity ratio of the formed deposited film were measured.

SiF4 50sec+W1Q Torr Substrate temperature: 250℃ The measurement results are shown in Figure 5 (8) [Film thickness measurement results] and Figure 5 (
B) The results are summarized in the figure [bright/dark conductivity ratio measurement results].

For each time, the graph a is the measurement result in case (1), the graph b is the measurement result in case (2),
Graph C shows the measurement results for the case of 3 nm.

From the experimental results shown in Figures 5(A) and 5(B), it is clear that at least two square cavity resonators are used, and the phase of the standing wave is shifted by λ/4 from one to the other. west,
It turns out that it is important to place these rectangular cavity resonators in a predetermined position on the peripheral wall of the reaction space 2.

In a preferred embodiment of the device of the present invention, eight rectangular cavity resonators 4a to 4h are provided at equal intervals, as illustrated in FIGS. 1 and 2. In the figure, 4a+ to 4h'
4a'' to 4h' indicate the electric field caused by the microwave, and 4a'' to 4h' indicate the plasma generated in the plasma region A of the reaction space 2 by the microwave power. In this case, each of the eight square cavity resonators is similar to the case where two square cavity resonators are used as described above, and the phase of the standing wave is shifted by λ/4. is as shown in Fig. 4. In Fig. 4, the vertical axis shows the electric field strength, and the horizontal axis shows the wavelength (λ
), that is, the square cavity resonator 4a
+4c+4e and 4g group standing waves and square cavity resonator 4
The standing waves of groups b, 4d, 4f and 4h are made to have a phase difference of λ/4 from each other. In this way, the phase of adjacent square cavity resonators is O or λ/4, and two square cavity resonators shifted by λ/4 from each other are set as l&li, and a total of 4 sets, that is, 8 square cavity resonators are provided. . and the standing wave and the base cylinder in the plasma region A9.9.・・・
・The relationship between the film deposition rate on the top and the standing wave of the rectangular cavity resonator 4a has a phase of 0, λ/2, λ, 3/2λ, etc.
..., the film deposition rate becomes faster at the position of Am/2 (where m is an integer), and the phase becomes λ/4.3λ/4.5λ/4,...
..., the film deposition rate becomes slow at the position of λn/4 (where n is an odd number). On the other hand, in the standing wave of the square cavity resonator 4b whose phase is shifted by λ/4 from that of the square cavity resonator 4a,
λ/4.3λ/4.5λ/4, ......, Am/4
The film deposition rate becomes faster at positions (where n is an odd number). Therefore, the combined use of two rectangular cavity resonators in which the standing waves (E) are out of phase, i.e., one is shifted by λ/4 from the other, complements the film deposition rate distribution. and make it uniform. That is, in the device example of the present invention shown in FIGS. 1 and 2, eight square cavity resonators 4a to 4h are used, and two square cavity resonators adjacent to each other generate a standing wave (E). The plasma region A of the reaction space 2, in which eight rectangular cavity resonators are installed, which have a constant phase difference of λ/4, is connected to the base cylinder 9.9. By sequentially rotating and moving the ..., the distribution of the film deposition rate for each base cylinder becomes uniform, and the deposited film deposited on the base cylinder becomes uniform in both film thickness and film quality. .

The phase relationship of the standing waves (E) of the eight installed rectangular cavity resonators 4a to 4h may be the same in 4a and 40. Also, the phase difference is λ/4, where 4b is the same phase as λ/4.4C is 2λ/4.
4d is 3λ/4.4e is 0.4f is λ/4.4g is 2λ
/4 and 4h may each have a phase difference of 3λ/4.

In the preferred embodiment of the apparatus of the present invention shown in FIGS. 1 and 2, eight rectangular cavity resonators are used as described above, but it is of course possible to increase or decrease the number depending on the scale of the apparatus. However, in any case, the number of rectangular cavity resonators whose film deposition rate becomes faster at the same position (phase) is the same as the number of rectangular cavity resonators whose film deposition rate becomes slower.

In other words, it is necessary to install an even number of them. Incidentally, if an odd number of units are installed, as described above for the case of one unit, the film deposition rate will not be supplemented, and the deposited film deposited on the base cylinder will be non-uniform in both film thickness and film quality. Become.

In the apparatus of the present invention, in addition to the requirements for the square cavity resonator to be installed as described above, it is important that the base cylinder be rotated and revolved during the film forming operation. In other words, as can be understood from the diagram in FIG. If the cylinder revolves but does not rotate, film deposition will occur only on the surface located in the plasma region A. On the other hand, when the base cylinder is rotated and revolved around its axis, a deposited film is uniformly formed in a desirable state in the circumferential direction of the base cylinder surface.

Also, during the film forming operation, the base cylinder is rotated, but
Without revolution, the film deposited on the base cylinder would be uneven both in film thickness and film quality, and the resulting product would be unusable, i.e. two rectangular Three base cylinders (9a, 9b, 9c) located between cavity resonators 4a and 4b
shall be. ), for the middle base cylinder 9b, the plasma concentration distribution becomes even more uniform due to the above-mentioned complementary effect of the two rectangular cavity resonators, and the film deposited on it becomes somewhat satisfactory. However, for the other two base cylinders 93 and 9c, the rectangular cavity resonators 4a and 4, which are at the shortest distance, respectively
The distribution of the standing wave b, that is, the generated plasma 4a#
and 4b' because it is constantly and strongly influenced by
The films deposited on these base cylinders not only become non-uniform both in film thickness and film quality, but also become defective due to the influence of the plasma.

In the above steps, only the rotation was performed under the conditions shown in Table 2 below, and the base cylinders 9, 9. ...It is easily understood from the results shown in Figures 6(A) and 6(B) that the film thickness and bright/dark conductivity ratio of the deposited film formed were measured. .

, table-m-'' engineering 5tFn 50sccm4b 4
80 4c 500 4d 500 4e 480 4r 500 4g 500 4h 480 Internal pressure: 10 Torr Meanwhile, the base cylinder 9.9 was rotated and revolved under the conditions shown in Table 2. When a film was formed on top of the film and the film thickness and bright/dark conductivity ratio of the formed deposited film were measured, the results shown in Figures 7(A) and 7(B) were obtained. . Judging from these results, when the film forming operation is performed while rotating and revolving, the base cylinders 9a and 9b.

Desirable pile M for any of 9C...! It is easily understood that a film is formed.

The speed of rotation and revolution of the base cylinder for forming a deposited film on the base cylinder by the apparatus of the present invention is not uniform depending on the scale of the apparatus, the size of the base cylinder, etc., and is determined as appropriate. Figures 1 to 2
The example device shown in the figure is, for example, a rectangular cavity resonator with a dielectric window 3 of size 961 mm (width) x 400 + u (length), and 12 base cylinders 9.9. ... is 108mm (diameter') x 400 Cao Sei (
In the case of an aluminum cylinder of size (length), the rotation speed is preferably 0.1 to l Q r
, p, m, , more preferably 1 r, p, n+,
The revolution speed is preferably 0.01 to 1 r, p, m, more preferably 0.1 r, 10 m.

An electrophotographic photoreceptor having a charge injection blocking layer, a photoconductive layer, and a surface layer was prepared using the apparatus shown in FIGS. 1 and 2 under the film forming conditions shown in Table 3.

As the rectangular cavity resonators 4a to 4h, those having a dielectric window with a size of 96 mm (width) x 400 mm (length) were used. In addition, as the base cylinder 9, 12 aluminum cylinders of size 108 (diameter) x 400 + u (length) were prepared, and each base holder 1 was prepared.
0.10, ... was installed at a predetermined position above.

Table 3 The 12 electrophotographic photoreceptors obtained were evaluated using conventional methods, and it was found that all of the photoreceptors had the desirable characteristics shown in Table 4 and had the desired film thickness. Understood.

Table 4■...Particularly good Q...Good Δ...No problem in practical terms

[Brief explanation of the drawing]

1 and 2 are explanatory diagrams of a functional deposited film forming apparatus using a typical MW-P CVD method provided by the present invention. 3(A) to CB) are explanatory diagrams of a rectangular cavity resonator used in the device. FIG. Fig. 5 is an explanatory diagram of the phase of the standing wave (E) of the square cavity resonators 4a to 4h. Figures 5 (A) to 5 (B) show experimental results regarding the number of square cavity resonators used. , 6th
Figures (A) to (B) and Figures 7 (A) to (B) are
FIG. 8, which shows experimental results regarding the rotation and revolution of the base cylinder, is an explanatory diagram of a functional deposited film forming apparatus using the conventional MW-PCVD method. Regarding Figures 1, 2, and 3 (A) to CB),
1... Vacuum container, 2... Reaction space, 3... Dielectric window, 4 (4a to 4h)... Square cavity resonator, 5...
・Microwave power supply, 6... Opening of exhaust pipe, 7... Raw material gas supply pipe, 7'... Gas blowing hole, 8... Substrate holder support, 9... Substrate (cylinder), 10・
...Substrate holder, 10'-=-heater, 1) ...
Short circuit plate, 4a' to 4h'... electric field by microwave, 4a# to 4h'... plasma, A... plasma region, B... non-plasma region. Figure 1 Source gas Figure 2 W Figure 3 (A) ] (B) Figure N4 Phase Figure 5 (A) (B) Drum shaft direction position (mm) Figure 6 (A) (B) Drum shaft Directional position (mm) Fig. 7 (A) (B) Drum axial position (mm) Fig. 8

Claims (2)

[Claims] (1) A functional deposited film forming apparatus using a microwave plasma CVD method, in which the peripheral wall surface of the film forming chamber is located at at least two, even number of positions coaxially opposing the apparent central axis of the film forming chamber. each portion is replaced with a metal rectangular cavity resonator having a dielectric window located on the side of the film forming chamber, and source gas is introduced into the film forming chamber from another peripheral wall portion of the film forming chamber. 1. An apparatus for forming a functional deposited film using a microwave plasma CVD method, characterized in that the discharge is directed toward the surfaces of each of a plurality of substrates. (2) An apparatus for forming a functional deposited film by a microwave plasma CVD method according to claim (1), characterized in that the plurality of substrates are made to rotate and revolve around each other.