JP2649333B2 - Plasma processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for enhancing a plasma chemical reaction by adding amplitude modulation, and more particularly to a photoelectric conversion device or a thin film field effect comprising a non-single-crystal semiconductor containing silicon as a main component. The present invention relates to a plasma processing apparatus using a plasma enhanced chemical vapor deposition method for mass-producing transistors and the like on a large substrate.

[0002]

2. Description of the Related Art Non-single-crystal semiconductor thin films containing silicon as a main component and insulating materials such as silicon oxide and silicon nitride formed by a plasma chemical vapor deposition method (hereinafter, referred to as a plasma CVD method). Body thin film is used for solar cells,
It is widely applied as a material for a thin film field effect transistor used for a photoelectric conversion device such as a disensor and a liquid crystal display device. These devices are configured by laminating a plurality of thin films having different properties. With the increase in size and cost, it is demanded that these laminated films be industrially manufactured in a large area and in large quantities. .

A conventional plasma CVD apparatus for achieving the above object will be described below. FIG. 1 is a schematic cross-sectional view for explaining a plasma CVD apparatus using the most common parallel plate electrode. The plasma CVD apparatus includes one vacuum preliminary chamber (1) and two reaction chambers (2) and (3). A substrate (11) on which a film is formed is placed on a substrate support (10), and together with the substrate support (10), a gate valve (8).
Through the reaction chamber (2). In the reaction chamber (2), the substrate (11) is heated by the heater (6) and after reaching a predetermined temperature, the reactive gas is decomposed by the discharge electrodes (4) and (6) and activated. To form a thin film on the substrate (11).

[0004] As is apparent from FIG.
Since (11) and the discharge electrodes (4) and (6) are parallel, when forming a thin film on a large-area substrate (11), the discharge electrodes (4)
It was necessary to increase the area of (6). Further, in the above-mentioned thin film forming method, since the film is formed only in a film area almost equal to the area of the discharge electrodes (4) and (6) in one process,
Insufficient for mass processing of (11). As one method for solving these problems, there is a plasma gas phase reactor (Japanese Patent Application No. 59-79623) by the present applicants. FIG. 2 is a schematic sectional view for explaining a film forming apparatus in a conventional example proposed by the present applicant.

In FIG. 2, a film-forming substrate (25) is overlapped between the parallel plate electrodes (21) with the film-forming surface facing the surface, and is perpendicular to the parallel plate electrodes (21). It is arranged. Compared with the above conventional example, this plasma processing apparatus can perform plasma processing 10 times or more at one time at a time, even though its floor area is almost the same as the conventional one. Further, in the plasma processing apparatus shown in FIG. 2, as the distance between the upper and lower parallel plate electrodes (21) is increased, a larger coating can be formed on the coating forming substrate (25).

[0006]

However, in practice, as the distance between the upper and lower parallel plate electrodes (21) increases, plasma discharge becomes less likely to occur. Therefore, the interval between the parallel plate electrodes (21) is usually set to be less than twice a side of the parallel plate electrode (21). The plasma gas phase reaction method for processing a large area and a large number of substrates has some disadvantages.
That is, the reduced pressure CVD method can make the film thickness relatively uniform, but it is necessary to decompose or activate a reactive gas in order to process a large area and a large number of substrates. However, to decompose or activate the reactive gas,
High-frequency power must be applied. When high-frequency power is applied to the electrode, the state of discharge differs depending on the vicinity of the electrode and the position distant from the electrode, and the film thickness distribution of the film is formed. When a large-area substrate is perpendicular to the electrodes and a large number of substrates are simultaneously coated, the distance between the parallel plate electrodes (21) is considerably long. However, except for the specific film forming condition, the film thickness distribution is provided in the direction between the parallel plate electrodes (21).

FIGS. 3 (A), 3 (B), 3 (C), and 3 (D) show a case where a non-single-crystal silicon semiconductor is formed on a film forming substrate by the plasma gas phase reaction apparatus shown in FIG. It is a figure for explaining the state where it is formed. In FIG. 3A, the magnitude of the high-frequency power is taken in the X-axis direction and the reaction pressure is taken in the Y-axis direction. 3A, when the reaction pressure is high and the input power of the high-frequency power is low, as shown in area 1 of FIG. 3A, the parallel plate electrode (25) of the film forming substrate 25 is formed as shown in FIG. 21) The coating formed near the top and bottom in the direction is
It has a thickness distribution such that it becomes thicker. During the production of this coating,
It was observed that the plasma emission region in the first reaction chamber (13) where the plasma reaction was taking place was gathered near the upper and lower parallel plate electrodes (21).

Next, when a high RF power is applied at a low reaction pressure, that is, when the relationship between the RF power and the reaction pressure is in the region 3 in FIG. 3A, as shown in FIG. The film formed near the center of the film forming substrate (25) in the direction of the parallel plate electrode (21) has a thicker film thickness distribution. Further, if the relationship between the high-frequency power and the reaction pressure is in a narrow range, but is in a relationship indicated by a region 2 in FIG. 3A, a uniform film thickness distribution as shown in FIG. Was possible. However, it has been difficult to control the relationship between the high-frequency power and the reaction pressure in the above narrow range.

As described above, if the film has a non-uniform film thickness distribution on a large-area substrate, the characteristics of the semiconductor elements formed on the same substrate, particularly the physical and electrical characteristics, vary greatly. Even if a TFT or a photoelectric conversion device is manufactured on a large-area substrate, no industrial value can be obtained.
The present invention is to solve the above problems,
An object of the present invention is to provide a plasma processing apparatus capable of forming a uniform film on a large number of large-area substrates.

[0010]

Means for Solving the Problems (First Invention) In order to achieve the above object, a plasma processing apparatus according to the present invention comprises a substrate (25) provided in a reaction space (13) maintained in a reduced pressure state. A) a high-frequency oscillator for generating high-frequency power for decomposing or activating the reactive gas, a means for amplitude-modulating the high-frequency power, and a high-frequency power modulated by the amplitude modulation means. An amplifier for amplification and the reaction space (1)
3) and a pair of electrodes (21, 23) for supplying the amplitude-modulated high-frequency power ;
High-frequency power amplitude-modulated by the electrodes (21, 23)
The substrate (25) is arranged so that is supplied in parallel planes.
And the substrate (25) is placed in the reaction space (13).
And a carrying means (15) for entering and leaving .

(Second Invention) In the plasma processing apparatus of the present invention, a large number of substrates (25) provided in a reaction space (13) include electrodes (21, 23).
It is characterized in that the film is superposed on each other so that the surface on which the film is formed becomes the surface, and is disposed so as to be perpendicular to the electrodes (21, 23).

[0012]

[Work] As in the prior art, the present applicant stopped simply applying high-frequency power with a constant amplitude, and amplitude-modulated the high-frequency power and applied it to the electrodes arranged in the reaction space, thereby obtaining a large area. It has been found that a film having a more uniform film thickness distribution can be obtained on the substrate. That is, the plasma processing apparatus of the present invention uniformly forms a coating on the surface of a substrate provided in a reaction space maintained under reduced pressure.
In the plasma processing apparatus of the present invention, high-frequency power is generated by the high-frequency oscillator and modulated to a desired modulation degree by the amplitude modulation means. This amplitude-modulated high-frequency power is amplified, and then applied to a pair of electrodes in a reaction space, so that a plane parallel to the substrate surface is formed.
Within, to increase the decomposition or activation of the reactive gas,
Or make it smaller. Such a change in the decomposition or activation of the reactive gas makes the film thickness distribution of the coating on the substrate more constant.

In addition, since the degree of decomposition or activation of the reactive gas can be adjusted in the reaction space, the reaction film is superimposed on the reaction space via a gap so that the surfaces on which the coatings are formed face each other. At the same time, the film is arranged perpendicularly to the electrodes, so that a uniform coating can be formed on a large number of substrate surfaces. Up
The substrate is transferred from the preliminary chamber to the reaction space and from the reaction space.
Arranged in transport means that can be transported to another or the same spare room
Is done. The transfer means does not require manual operation of the substrate.
And can be moved into and out of the reaction space. For example,
The degree of the amplitude modulation is 5 points from the point of the stable plasma discharge.
0% or less. When a reactive gas radical is present, amplitude modulation may be performed as repetition of the presence or absence of discharge. Thus, when the discharge is weak or not due to the modulation, the same effect as the reduced pressure CVD is exerted. For example, even on the surface of the substrate having irregularities, the side surface is also formed to the same thickness as the upper surface, or the reaction vessel This has the effect of reducing the flakes generated on the inner wall of the glass.

In addition, the number of times of amplitude modulation is one or more in five seconds due to the problem of characteristics of the formed film. That is, when the amplitude modulation degree approaches 100%, the difference between the portion where no high-frequency power is generated and the portion where the amplitude is large increases. Further, when the amplitude modulation degree is reduced, it becomes the same as the case where high frequency power is simply applied. Furthermore, if the number of times of amplitude modulation is small, it is the same as that of simply applying high-frequency power having a constant amplitude, and if it is large, the change in the decomposition or activation of the reactive gas increases. Hereinafter, the present invention will be described with reference to examples.

[0015]

EXAMPLE In this example, a non-single-crystal semiconductor film was formed on a film-forming substrate (25) made of, for example, glass using the plasma gas phase reaction apparatus shown in FIG. In FIG. 2, the substrate support tray (24) is set so that a film forming substrate (25) having a size of 300 mm × 400 mm is arranged perpendicular to the parallel plate electrodes (21). In the present embodiment, ten film-forming substrates (25) are mounted on the substrate-supporting tray (24), and the distance between the film surfaces of the film-forming substrates (25) is 20 mm. In the above case, since a discharge is generated, it is possible to form a film on a larger number of film forming substrates (25). Considering the uniformity of the film thickness of the film forming substrate (25), in the case of the present embodiment, about 10 to 15 sheets are preferable.

The interval between the film forming substrates (25) is
It is not appropriate to fix them together because they change depending on other factors such as the pressure at the time of film formation. This substrate for film formation
The substrate support tray (24) in which (25) is set is placed in the preliminary chamber (12) of the plasma CVD apparatus, and after performing vacuum evacuation, the gate valve (16) is opened and the transfer mechanism (15) By first
Move to reaction chamber (13). Thereafter, although not shown in FIG. 2, it is omitted. However, the substrate-forming heaters, which are parallel to the plane of FIG. Heated to about 300 ° C. In this state, silane gas was introduced into the first reaction chamber (13) for 50 SC.
It is introduced at the flow rate of CM, and the conductance of the exhaust system is controlled to increase the pressure in the first reaction chamber (13) to 0.01 torr to 0.1 torr.
Held.

Next, 13.56M is applied between the upper and lower parallel plate electrodes (21).
Hz high frequency power is applied, and the plasma discharge is confined in a space defined by the upper and lower electrode hoods (18) and the side surfaces of the substrate support tray (24), and the first reaction chamber (13) It has not reached the inner wall. Therefore, the film to be formed is also formed only in the above-mentioned space, and it is not necessary to clean the inner wall of the first reaction chamber (13), or it is possible to reduce the number of times of cleaning very much. It is possible. A high frequency of 13.56 MHz is supplied between the parallel plate electrodes (21). That is, the conventionally known plasma CVD method is:
It has been better to keep the power value or peak value applied to the electrode constant.

However, in the present invention, a modulating circuit (amplitude modulating means) for modulating the amplitude in the radio is added between the high-frequency transmitting circuit and the final-stage amplifier circuit (means for generating high-frequency power). It is. So-called amplitude modulation (ampr) in which amplitude modulation of a high frequency causes the peak value of the amplitude to increase or decrease (including zero)
proof modutation). The amplitude-modulated high-frequency power was supplied to a pair of electrodes which was a means for supplying the reaction space. In this embodiment, the amplitude is modulated as described above to change the decomposition or activation of the reactive gas. That is, in the conventional plasma processing method of plasma CVD, a high frequency having a constant amplitude is applied to decompose or activate a reactive gas to form a film. Therefore, when the size of the substrate on which the film is formed becomes large, the decomposed or activated reactive gas does not spread uniformly in the reaction space.

On the other hand, in the present embodiment, the reactive gas is widely dispersed by applying the amplitude-modulated high-frequency power to change the decomposition or activation.
Therefore, the reactive gas is uniformly dispersed on the film forming substrate (25) and reaches the surface on which the reactive gas is to be formed. As a result, a uniform coating can be formed. In the plasma CVD method in the conventional method, since a discharge is generated by constantly applying a high-frequency power having a constant intensity, the discharge is more easily performed where the discharge is intensified, and the discharge is performed where no discharge is performed. The variation in the film thickness distribution due to the instability of the plasma, which is difficult, resulted in an uneven film thickness. The number of times of amplitude modulation by the high frequency power applied between the parallel plate electrodes (21) is, for example, once or more every 1 to 5 seconds.

In this embodiment, the high-frequency power under the above amplitude modulation condition was discharged for about 20 minutes in total, and a non-single-crystal silicon semiconductor was formed on the substrate to a thickness of about 5000 mm. In this case, a 300 mm × 400 mm film-forming substrate (25)
The coating formed on the sample was more uniform than that without the amplitude modulation. 300 mm using the method of the present invention.
400 solar cells (element area: 1.05 cm ² ) having a P, I, N structure were fabricated on a × 400 mm film formation substrate (25). The characteristics are shown below. Photoelectric conversion efficiency (%) Quantity 11.10 to 10.6 12 10.5 to 10.1 206 10.0 to 9.6 173 9.5 to 9.1 9 9.0 to 8.6 0

Thus, when the coating formed by the method of the present embodiment and the coating formed by the conventional method are compared, the coating formed by the method of the present invention is as follows.
The variation in photoelectric conversion efficiency is very small. This is particularly because there is a deep relationship with the very small variation in the thickness of the I-type semiconductor layer of the PIN solar cell.

[0022]

As described above, according to the present invention, the amplitude-modulated and amplified high-frequency power is applied to the pair of electrodes disposed in the reaction space maintained in a reduced pressure state. The reactive gas is dispersed to form a uniform film on a large-area substrate for film formation. According to the present invention, the electrodes are overlapped with each other so that the surface on which the film is formed becomes the surface, and are disposed so as to be perpendicular to the electrodes, so that a uniform film is formed on the surface of the large substrate. It becomes possible. As a result, the number of elements that can be taken out increases from a large-area film-forming substrate, and moreover, uniform characteristics can be obtained. According to the present invention,
The substrate can be transferred from the preliminary chamber to the reaction space without manual intervention.
It is also transferred from the reaction space to another or the same
You. According to the present invention, the substrate transfer means and the reaction space
Support means can also be used. According to the present invention, since a large-area element such as a solar cell does not generate flakes on the inner wall of the reaction space, it is not necessary to clean the inner wall of the reaction chamber and the like, and a highly efficient device can be obtained. . ADVANTAGE OF THE INVENTION According to this invention, even if it has unevenness | corrugation on a large-area board | substrate, the film | membrane of the same thickness as an upper surface can be formed uniformly also on the side surface.

[Brief description of the drawings]

FIG. 1 shows a plasma C using the most common parallel plate electrode.
FIG. 2 is a schematic sectional view for explaining a VD device.

FIG. 2 is a schematic cross-sectional view for explaining a conventional film forming apparatus proposed by the present applicant.

3 (A), (B), (C) and (D) show the formation of a film when a non-single-crystal silicon semiconductor is formed on a film-forming substrate by the plasma gas phase reaction apparatus shown in FIG. FIG. 7 is a diagram for explaining a state in which the operation is performed.

[Explanation of symbols]

12 ・ ・ ・ Preparatory room 21,23 ・ ・
・ Parallel plate electrode 13 ・ ・ ・ First reaction chamber 24 ・ ・ ・ Tray for substrate support 14 ・ ・ ・ Second reaction chamber 25 ・ ・ ・ Coating substrate 15 ・ ・ ・ Transport mechanism 16, 17 ・ ・ ・ Gate valve 18, 19, 20 ... food

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Masayoshi Abe 398 Hase, Atsugi-shi, Kanagawa Prefecture Semiconductor Energy Research Institute, Inc. (72) Inventor Katsuhiko Shibata 398 Hase, Atsugi-shi, Kanagawa Semiconductor Energy Research Institute, Inc. (72) Inventor Masato Usada 398 Hase, Atsugi-shi, Kanagawa Prefecture Inside the Semiconductor Energy Laboratory Co., Ltd. (72) Inventor Noriya Ishida 398 Hase, Atsugi-shi, Kanagawa Prefecture Inside the Semiconductor Energy Laboratory Co., Ltd. (72) Inventor Akemi Satake, Atsugi-shi, Kanagawa Prefecture 398 Inside Semiconductor Energy Laboratory Co., Ltd. (72) Inventor Yasuyuki Arai 398 Hase, Atsugi-shi, Kanagawa Inside Semiconductor Energy Laboratory Co., Ltd. (56) References JP-A-63-42115 (JP, A)

Claims (2)

(57) [Claims] 1. A plasma processing apparatus for forming a film on a surface of a substrate disposed in a reaction space held under reduced pressure, comprising: a high-frequency oscillator for generating high-frequency power for decomposing or activating a reactive gas; Means for amplitude-modulating the high-frequency power, an amplifier for amplifying the high-frequency power modulated by the amplitude modulation means, and a pair of electrodes provided in the reaction space and supplying the amplitude-modulated high-frequency power The high-frequency power amplitude-modulated by the pair of electrodes is flat.
The substrate is arranged so that it is supplied in the
A transfer means for moving the substrate into and out of the reaction space . 2. The substrate according to claim 1, wherein the plurality of substrates are overlapped with each other between the electrodes so that the surface on which the film is formed is the surface, and are arranged perpendicular to the electrodes. The plasma processing apparatus as described in the above.