JP2001271169A - Plsma chemical vapor deposition system having fork type electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma chemical vapor deposition system having a fork type electrode with which the deposition of a film excellent in the uniformity of film thickness can be performed to a substrate having a large surface at a high speed by using an ultrahigh frequency. SOLUTION: In this plasma chemical vapor deposition system in which discharge plasma of gas for film deposition is generated on the space between an electrode and a substrate to be treated to deposit a film on the substrate, electrodes 32a, 32b and 32c have plural electric power supplying edges 44 to 51 connected to a power source circuit, a linear base 33B fitted with the plural electric power supplying edges subtantially at equal pitch intervals, and plural ribs 33R branched from the base and stretching substantially at equal pitch intervals and also in parallel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma chemical vapor deposition apparatus, and relates to various electronic devices such as amorphous silicon solar cells, microcrystalline silicon solar cells, thin film polycrystalline silicon solar cells, thin film semiconductors, optical sensors, and semiconductor protective films. The present invention relates to a plasma chemical vapor deposition apparatus (hereinafter, referred to as a plasma CVD apparatus) applied to manufacture of a thin film to be used.

[0002]

2. Description of the Related Art Amorphous silicon (hereinafter a-Si)
Thin film) or silicon nitride (hereinafter, referred to as SiNx)
In order to form a thin film, two types of plasma CVD apparatuses conventionally used are known. In other words, there are two systems, one using a ladder electrode for discharge, that is, an electrode also called a ladder inductance electrode or a ladder antenna electrode, and the other using a parallel plate electrode as electrodes used for generating discharge plasma.

First, as a publicly known document relating to a system using a ladder-type electrode, there is, for example, Japanese Patent Application Laid-Open No. Hei 4-236781. This discloses a plasma CVD apparatus using electrodes of various shapes as ladder-like planar coil electrodes. A representative example of this method will be described with reference to FIG. Reference numeral 1 in the figure denotes a reaction vessel.
Inside, a discharge ladder electrode 2 and a substrate heating heater 3 are arranged in parallel. A high frequency power of, for example, 13.56 MHz is supplied to the discharge ladder electrode 2 from the high frequency power supply 4 via the impedance matching device 5. As shown in FIG. 8, the discharge ladder electrode 2 has one end connected to a high-frequency power supply 4 via an impedance matching device 5,
The other end is connected to a ground wire 7 and grounded together with the reaction vessel 1.

The high-frequency power supplied to the discharge ladder electrode 2 generates a glow discharge plasma between the substrate heating heater 3 and the electrode 2 which are grounded together with the reaction vessel 1, and the reaction vessel passes through a discharge space. 1 and to ground via the ground wire 7 of the ladder electrode 2 for discharge. Note that a coaxial cable is used for the ground wire 7.

[0005] In the reaction vessel 1, for example, a mixed gas of monosilane and hydrogen is supplied from a cylinder (not shown) through a reaction gas introduction pipe 8. The supplied reaction gas is decomposed by the glow discharge plasma generated by the discharge ladder electrode 2, held on the substrate heating heater 3, and deposited on the substrate 9 heated to a predetermined temperature. The gas in the reaction vessel 1 is exhausted by a vacuum pump 11 through an exhaust pipe 10.

Hereinafter, a case where a thin film is manufactured using the above apparatus will be described. First, after the inside of the reaction vessel 1 is evacuated by driving the vacuum pump 11, a mixed gas of, for example, monosilane and hydrogen is supplied through the reaction gas introduction pipe 8,
The pressure in the reaction vessel 1 is maintained at 0.05 to 0.5 Torr.

[0007] In this state, the high-frequency power supply 4 is used for discharging.
When high-frequency power is applied to the electrode 2, the glow discharge plug
Zuma occurs. The reaction gas is supplied to the discharge ladder electrode 2
The glow discharge plasma generated in the substrate heating heater 3 causes
Is decomposed, resulting in SiH _Three, SiH_TwoIncluding Si
Radicals are generated and adhere to the surface of the substrate 9 to form an a-Si thin film.
A film is formed.

Next, a method using parallel plate electrodes will be described with reference to FIG. Reference numeral 21 in the drawing denotes a reaction vessel, in which a high-frequency electrode 22 and a substrate heating heater 23 are arranged in parallel. High frequency electrode 2
2 is supplied with a high frequency power of, for example, 13.56 MHz from a power supply 24 via an impedance matching unit 25.
The substrate heating heater 23 is grounded together with the reaction vessel 21 and serves as a ground electrode. Therefore, glow discharge plasma is generated between the high-frequency electrode 22 and the substrate heating heater 23.

A mixed gas of, for example, monosilane and hydrogen is supplied into the reaction vessel 21 through a reaction gas introduction pipe 26 from a cylinder (not shown). The gas in the reaction vessel 21 is exhausted by a vacuum pump 28 through an exhaust pipe 27. The substrate 29 is held on the substrate heater 23 and is heated to a predetermined temperature.

Using such an apparatus, a thin film is manufactured as follows. First, the inside of the reaction vessel 21 is evacuated by driving the vacuum pump 28. Next, a mixed gas of, for example, monosilane and hydrogen is supplied through the reaction gas introduction pipe 26 to maintain the pressure in the reaction vessel 21 at 0.05 to 0.5 Torr, and a voltage is applied from the high frequency power supply 24 to the high frequency electrode 22. Then, glow discharge plasma is generated.

Among the gases supplied from the reaction gas introduction pipe 26, monosilane gas is decomposed by glow discharge plasma generated between the high-frequency electrode 22 and the substrate heating heater 23. As a result, radicals containing Si, such as SiH ₃ and SiH _2, are generated, adhere to the surface of the substrate 29, and a-
A Si thin film is formed.

[0012]

However, both the conventional method using a ladder antenna electrode for discharge and the method using a parallel plate electrode have the following problems (1) and (2).

(1) In the apparatus shown in FIG. 8, a reaction gas, for example, SiH ₄ is converted into Si, SiH, SiH ₂ , SiH ₃ , H, by an electric field generated near the discharge ladder electrode 2.
It is decomposed into H ₂ or the like, and forms an a-Si film on the surface of the substrate 9. However, in order to speed up the formation of the a-Si film, the frequency of the high frequency applied from the high frequency power supply 4 to the electrode 2 is increased from the current 13.56 MHz, for example, 30 MHz.
When the frequency is increased from MHz to 150 MHz, the electrode 2
The uniformity of the electric field distribution is destroyed in the region near the above, and as a result, the film thickness distribution of the a-Si film becomes extremely poor.

In FIG. 10, the horizontal axis represents the frequency (MHz) of the high frequency applied from the plasma power source, and the vertical axis represents the film thickness distribution (%) indicating the amount of deviation from the average film thickness.
FIG. 4 is a characteristic diagram showing a relationship between a plasma power supply frequency at 30 cm and a film thickness distribution. From the characteristic line C in FIG.
At 3.56 MHz or higher, it was found that it was difficult to ensure uniformity of the film thickness distribution. Also, from the characteristic diagram of other data not shown, the size, that is, the area of the substrate that can ensure the uniformity of the film thickness distribution (within ± 10%) is about 5 cm × 5 cm to 20 cm × 20 cm. It is known.

The reason why it is difficult to increase the frequency of the high-frequency power supply 4 by a method using a ladder electrode for discharge is as follows. As shown in FIG. 11, because of the non-uniformity of impedance due to the structure of the ladder electrode for discharge,
A portion where plasma emission is strong occurs locally. For example,
Strong plasma is generated at the periphery of the electrode, but not at the center. In particular, the decrease becomes remarkable as the frequency becomes higher than 60 MHz.

Therefore, it is very difficult to improve the film forming speed by increasing the frequency of the plasma power supply for a large area substrate of 1 m × 1 m to 2 m × 2 m size required for mass productivity improvement and cost reduction. It is said that. Since the deposition rate of the a-Si film is proportional to the frequency of the plasma power supply, researches have been actively conducted by academic societies in related technical fields, but no successful example of increasing the area has been reported yet.

(2) In FIG. 9, a reaction gas, for example, SiH ₄ is converted into Si, SiH, SiH ₂ , SiH by an electric field generated between the high-frequency electrode 22 and the substrate heating heater 23.
It is decomposed into H ₃ , H, H _2, etc., and forms an a-Si film on the surface of the substrate 9. However, in order to speed up the formation of the a-Si film, the frequency of the high-frequency power supply 24 is set to 13.56 at present.
When the frequency is higher than 30 MHz to 30 MHz to 200 MHz, the uniformity of the electrolytic distribution generated between the high-frequency electrode 22 and the substrate heating heater 23 is lost, and as a result, a-S
The thickness distribution of the i-film becomes extremely poor. FIG. 10 is a characteristic diagram showing the relationship between the plasma power frequency and the film thickness distribution (deviation from the average film thickness) at a substrate area of 30 cm × 30 cm.
It has been found from the characteristic line D in FIG. 10 that when the frequency is 13.56 MHz or more, it is difficult to ensure uniformity of the film thickness distribution. Also, from the characteristic diagram of other data not shown, in the film formation by plasma CVD using a VHF power supply, the size, that is, the area of the substrate that can ensure the uniformity of the film thickness distribution (within ± 10%) is as follows. , 5cm x 5cm or 2
It has been found that the size is about 0 cm × 20 cm.

The reason why it is difficult to increase the frequency of the high-frequency power supply 24 by the method using parallel plate electrodes is as follows. Since the parallel plate electrode has different electrical characteristics between the peripheral portion and the central portion of the electrode, a strong plasma is generated at the peripheral portion of the electrode as shown in FIG. 12A or the central portion as shown in FIG. There is a phenomenon that strong plasma is generated only in the part.

Therefore, it is extremely difficult to improve the film formation speed by increasing the frequency of the plasma power supply for a large area substrate of 1 m × 1 m or 2 m × 2 m required for mass productivity improvement and cost reduction. Have been done. Since the deposition rate of the a-Si film is proportional to the frequency of the plasma power supply, researches have been actively conducted by academic societies in related technical fields, but no successful example of increasing the area has been reported yet.

The present invention has been made in order to solve the above-mentioned problems, and is intended for a substrate having a much larger size than the conventional one, for example, a large area substrate having a size of 1 m × 1 m to 2 m × 2 m. It is an object of the present invention to provide a plasma CVD apparatus capable of realizing high-speed film formation with excellent film thickness uniformity using a very high frequency (VHF) having a large value.

[0021]

According to a plasma chemical vapor deposition apparatus having a fork-type electrode according to the present invention, power is supplied to an electrode from a VHF class high frequency power supply, and a gas for forming a film is formed between the electrode and a substrate to be processed. A plasma chemical vapor deposition apparatus for generating a discharge plasma to form a film on a substrate to be processed, wherein the electrode has a plurality of power supply terminals connected to an output circuit of the power supply, and the plurality of power supply terminals are substantially A linear base attached at equal pitch intervals, and a plurality of ribs branched from the base and extending substantially at equal pitch intervals and in parallel,
It is characterized by having.

The above-mentioned electrodes are composed of a combination of electrodes having a pair of electrode members facing each other, and it is desirable that the ribs of one electrode member and the ribs of the other electrode member are alternately arranged in substantially the same plane. . Thereby, uniform discharge plasma is generated over the entire surface of the large substrate, and the uniformity of the film thickness is improved.

A first high-frequency power supply is connected to each power supply end of one electrode member, and a second high-frequency power supply independent of the first high-frequency power supply is connected to each power supply end of the other electrode member. Preferably they are connected.

In this case, a first power distributor provided between one of the electrode members and the first high-frequency power source for distributing power to the respective power supply terminals, and the other electrode member include: A second power distributor provided between the power supply terminal and the second high-frequency power supply to distribute power to each power supply terminal.

Further, the one electrode member and the first electrode member
And a plurality of first T-type connectors provided between the second electrode member and the second high-frequency power supply for distributing power to the respective power supply terminals. And a plurality of second T-type connectors for respectively distributing power to the supply end.

It is preferable that the power supply end is attached to a place where the rib branches off from the base. Thereby, the impedance of each rib becomes substantially equivalent, and the density of the generated plasma is made uniform.

The electrode desirably comprises a single base and a plurality of ribs branching from the single base and extending substantially in parallel.

In this case, two independent high-frequency power sources connected to the power supply terminals attached to the single base and supplying power to a common electrode may be provided.

[0029] The electrodes may include a plurality of first power supply ends attached to a single base, and a plurality of first power supply ends respectively attached to free ends of the ribs corresponding to the first power supply ends. And two power supply terminals.

In the present invention, a reaction vessel, a means for supplying a reaction gas to the reaction vessel, a means for discharging the reaction gas from the inside of the reaction vessel, a discharge fork type electrode arranged in the reaction vessel, 30M frequency for fork electrode for discharge
And a heater for supporting a substrate to be processed, which is disposed in parallel with the fork-shaped electrode for discharge in the reaction vessel and is separated from the power supply. In a plasma chemical vapor deposition apparatus that generates a glow discharge by the supplied power and forms an amorphous thin film, a microcrystalline thin film, or a polycrystalline thin film on the surface of a substrate to be processed, the number of the fork electrodes is two, and As shown in FIGS. 3 (a) and 3 (b), the fork-shaped electrodes are disposed so as to face each other in the same plane or substantially the same plane, and the bar-shaped electrodes having the structure are arranged alternately with each other.
Two independent VHF (Ve
ry High Frequency: 30MHz to 200MHz)
The power of almost the same frequency is supplied from the class power supply.

As a method of supplying power to the fork-type electrode, a plurality of power supply terminals are arranged on the back of the fork-type electrode, and the power supply is connected to the power supply by using a vacuum coaxial cable through each of the terminals. The output is supplied.

[0032]

When the present inventors supply power to the back (base) of the fork-type electrode through a power supply terminal, the voltage distribution on the electrode is very high frequency (VHF). As shown by the characteristic line A in FIG. 5, it has been found that the voltage on the electrode rod gradually decreases as the distance from the power supply end increases. It is presumed that this voltage drop is caused by a phenomenon unique to VHF called the skin effect. In addition, the present inventors used one fork-type electrode as a discharge electrode of a plasma CVD apparatus, supplied VHF power to the base thereof, and formed a-Si film on a large-area glass substrate. It was found that a film thickness distribution as shown in FIG. When the fork-type electrode is arranged in an inverted shape and VHF power is supplied to its base, a film thickness distribution symmetrical to that of FIG. 6A is obtained as shown in FIG. 6B. I got the knowledge that it can be done.

Further, the two fork-type electrodes are connected to each other as shown in FIG.
As shown in FIG. 2B, two VHF power supplies independent of each other are supplied with power of substantially the same frequency to the bases of the two electrodes in the same plane or substantially the same plane as shown in FIG. When a-Si is formed on the glass substrate of
The distribution shown in FIG. 6A and the distribution shown in FIG. 6B were synthesized, and it was found that a good film thickness distribution was obtained as shown in FIG. 6C.

When the two VHF power supplies are not independent, for example, when an a-Si film is formed on a large-area glass substrate by supplying power to two fork-type electrodes by one VHF electrode. It was also found that the film thickness distribution was not uniform, as shown in FIG. The reason is that the electric fields generated by the two fork-shaped electrodes interfere with each other, and as a result, a simple distribution as shown in FIGS. 6A, 6B, and 6C cannot be formed. It is inferred.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Various preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

(Embodiment 1) The apparatus of Embodiment 1 will be described with reference to FIGS. In the figure, reference numeral 31 denotes a reaction vessel. In the reaction vessel 31, a first discharge fork electrode 32a made of stainless steel (SUS304) for generating glow discharge plasma, a second fork electrode 32b, and a glass substrate 9 as a substrate to be processed are provided. A substrate heating heater 34 that supports and controls the temperature of the substrate 9 is provided. In the reaction vessel 31, the reaction gas is supplied with the first and second fork electrodes 32a for discharge,
A reaction gas introduction pipe 37 having a reaction gas discharge hole 37a to be introduced around 32b is arranged. The first and second fork electrodes 32a and 32b for discharging are connected to the power supply end 44.
51 to 51, a base 33B to which high-frequency power is supplied from a power supply via each power supply end, and a plurality of ribs 33R that branch off from the base 33B and extend in parallel and at equal pitches in the same plane. I have.

A vacuum pump 39 is connected to the reaction vessel 31 via an exhaust pipe 38 for exhausting a gas such as a reaction gas in the reaction vessel 31. An earth shield 40 is arranged in the reaction vessel 31. This earth shield 40
Is to suppress discharge in unnecessary parts, and
Is used in combination with the vacuum pump 39 to convert the reaction gas such as SiH ₄ introduced from the reaction gas introduction pipe 37 into plasma at the first and second electrodes 32a and 32b, and then react the reaction gas and other products. And the like are discharged through the exhaust pipe 38. The pressure in the reaction vessel 31 is monitored by a pressure gauge (not shown) and is controlled by adjusting the displacement of the vacuum pump 39.

First and second fork electrodes 32 for discharge
a and 32b to generate SiH ₄ plasma, the SiH ₃ , SiH ₂ , and Si present in the plasma are generated.
Radicals such as H are diffused by a diffusion phenomenon and are adsorbed on the surface of the substrate 9, whereby an a-Si film, microcrystalline Si, or thin-film polycrystalline Si is deposited on the substrate 9. The known a-Si film, microcrystalline Si, and thin-film polycrystalline Si can be formed by optimizing the flow ratio of SiH ₄ and H ₂ , the pressure, and the power for plasma generation in the film forming conditions. Since this is a technique, an a-Si film formation using SiH ₄ gas will be described here as an example. Of course, it is also possible to form microcrystalline Si and thin-film polycrystalline Si.

Feed electrodes 40a to 40d and 41a to 4a to be described later are connected to the fork-shaped electrodes 32a and 32b, respectively.
1d, power introduction terminals 61a, 61b, 61c, 61d,
61e, 61f, 61g, 61h, the first and second power dividers 60a, 60b, and the first and second impedance matching devices 35a, 35b connect the first and second high frequency power supplies 36a, 36b. It is connected.

FIG. 2 is an explanatory diagram showing electric wiring for supplying high-frequency power to the first and second fork electrodes 32a and 32b for discharge. In FIG. 2, for example, power of a frequency of 60 MHz is supplied to the first and second high-frequency power sources 3.
6a, 36b, the first and second impedance matching devices 35a, 35b, the power distributors 60a, 60b, the coaxial cables 40a, 40b, 40c, 40d, 40e, 40
f, 40g, 40h, current introduction terminals 61a, 61b, 6
1c, 61d, 61e, 61f, 61g, 61h and vacuum coaxial cables 43a, 43b, 43c, 43d,
The power is supplied to the eight power supply terminals 44 to 51 welded to the first and second fork-shaped discharge electrodes 32a and 32b via 43e, 43f, 43g and 43h. The first and second fork-shaped electrodes 32a, 32b for discharging are used.
Are austenitic stainless steel bars having a diameter of 10 mm (for example, JIS standard SUS304, SUS304L, S
US316, SUS316L, etc.)
2000mm x 2000mm, center spacing between adjacent ribs is 26
mm.

First and second power distributors 60a, 60b
Has a function of equally dividing the input high-frequency power into four.

Next, a method for manufacturing an a-Si film using the above-configured plasma CVD apparatus will be described.

First, the inside of the reaction vessel 31 is evacuated by operating the vacuum pump 39, and the ultimate degree of vacuum is set to 2-3 × 10 ⁻⁷ To.
rr. Next, a reaction gas, for example, SiH ₄ gas is supplied from the reaction gas introduction pipe 37 at a flow rate of about 1000 to 1600 sccm. Thereafter, the pressure in the reaction vessel 31 is reduced to 0.0
While maintaining the pressure at 5 to 0.5 Torr, the first and second impedance matching devices 35a and 35b, the first and second power distributors 60a and 60b, and the power introduction from the first and second high-frequency power sources 36a and 36b. Through the terminals 61a to 61h and the vacuum coaxial cables 43a to 43h, high-frequency power, for example, 60 MHz, is supplied to the first and second discharge fork-shaped electrodes 32a and 32b. As a result, the first
And Si near the second fork-shaped electrodes 32a and 32b.
H ₄ glow discharge plasma is generated. This plasma decomposes the SiH ₄ gas to form an a-Si film on the surface of the substrate 9. However, the deposition rate is about 1 to 5 nm / sec, depending on the frequency and output of the first and second high frequency power supplies 36a and 36b.

Table 1 shows an example of the results of the film forming test of Example 1.

[0045]

[Table 1]

The data shown in Table 1 is based on the assumption that one power supply for discharging is used, for example, the first high-frequency power supply 36a shown in FIGS.
5a, 35b, and the first and second power distributors 60a, 60b, the vacuum coaxial cable 43a, respectively.
Through the first and second fork-shaped electrodes 32 through 43h.
a and 32b, and FIGS. 1 and 2
In other words, two independent power supplies 36a, 36
b is comparison data in the case where power of a frequency of 60 MHz is supplied using b. In the former case, the film forming speed is 1.
The film thickness distribution was ± 50% at 5 nm / sec. In the latter case, the film thickness distribution was ± 8% at a film formation speed of 1.5 nm / sec.

Further, it has been confirmed by experiments that the film thickness distribution does not significantly deteriorate even when the frequencies of the two power supplies are significantly different from each other, for example, 60 MHz and 50 MHz.

In the manufacture of a-Si solar cells, thin film transistors, photosensitive drums, etc., the film thickness distribution is ±
If it is within 10%, there is no problem in performance.

According to the first embodiment, the frequency of the two power supplies is 60 MHz, but a significantly better film thickness distribution can be obtained as compared with the conventional apparatus and method. In the first embodiment, the power supply frequency is only 60 MHz, but the first and second power dividers 60a and 60b and the first and second impedance matching devices 35a and 35b are sufficiently applicable to 80 MHz to 200 MHz. , A-Si film formation can be sufficiently applied in the frequency range of 80 MHz to 200 MHz.

On the other hand, in a conventional plasma deposition apparatus, 30
When a VHF power supply of not less than MHz is used, the film thickness distribution is remarkably deteriorated, and it has not been put to practical use with a large area substrate of about 5 cm × 5 cm to 30 cm × 30 cm or more.

(Embodiment 2) Reference is made to FIGS. 1, 2 and 4. FIG. In the device configuration shown in FIGS. 1 and 2, the first and second power distributors 60a and 60b are connected to T-type connectors 71, 72, 73, 74, 7 for coaxial cables as shown in FIG.
5 and 76, the outputs of the first and second impedance matching devices 35a and 35b are branched to four points, respectively.
And, via the eight coaxial cables 40a to 40h,
1 and 2, power is supplied to the first and second fork-shaped electrodes 32a and 32b.

Next, a method for manufacturing an a-Si film using the plasma CVD apparatus having the above configuration will be described. First, the vacuum pump 39 is operated to evacuate the inside of the reaction vessel 31 and the ultimate vacuum is set to 2-3 × 10 ⁻⁷ Torr. Subsequently, a reaction gas, for example, SiH
_Four gases are supplied at a flow rate of about 1000 to 1600 sccm.

Thereafter, the pressure in the reaction vessel 31 is set to 0.05
The first and second high-frequency power sources 36a and 36b maintain the impedance matching unit 35 while maintaining the pressure at about 0.5 Torr.
a, 35b, T-type connectors 71, 72, 73, 74, 7
Ultra high frequency power, for example, 60 MHz, is supplied to the first and second forked electrodes 32a and 32b via the coaxial cables 5 and 76 and the vacuum coaxial cables 43a to 43h. As a result, the first and second fork-shaped electrodes 32a, 32
Glow discharge plasma of SiH ₄ is generated near 2b. This plasma decomposes the SiH ₄ gas to form an a-Si film on the surface of the substrate 9.

An example of the results of the film forming test of Example 2 is shown in Table 2 below.

[0055]

[Table 2]

This data is based on the assumption that one power supply for discharging is used, for example, as a first high frequency power supply 36a in FIG. 4, the output of which is input to first and second impedance matching devices 35a and 35b. T-type connectors 71 to 76,
When power is supplied to the first and second fork-shaped electrodes 32a and 32b through the vacuum coaxial cables 43a to 43h, and by using the method shown in FIG. 4, that is, using two independent power supplies 36a and 36b. , Data when power is supplied to the first and second fork-shaped electrodes 32a and 32b. The former shows a film thickness distribution of ± 55% at a film formation speed of 1.8 nm / sec, and the latter shows a film thickness distribution of ± 10% at a film formation speed of 1.8 nm / sec. It was remarkably good.

In the production of a-Si solar cells, thin film transistors, photosensitive drums, etc., the film thickness distribution is ±
If it is within 10%, there is no problem in performance.

On the other hand, in a conventional plasma deposition apparatus, 30
When a high-frequency power supply at MHz or higher is used, the film thickness distribution is ± 3
Very bad, 0% to 50%, 5cm x 5cm to 20c
It has not been put to practical use with a large area substrate of about mx 20 cm or more.

(Embodiment 3) The fluctuation of the film thickness distribution is larger than in Embodiments 1 and 2, but the following example is also conceivable.

That is, as shown in FIG. 13, in one fork-shaped electrode 32c, the power from the first high-frequency power supply 36a independent of the four power supply terminals 44, 45, 46, 47 on one side is supplied. In this configuration, power is supplied from an independent second high-frequency power supply 36b to the other four power supply terminals 48, 49, 50, and 51.

Although the use of such a fork-shaped electrode 32c is slightly inferior to the above-described first and second embodiments, one high-frequency power source is branched into eight locations, and the power supply terminals 44 to 51 are connected to the power supply terminals 44 to 51. A better film thickness distribution was obtained than in the connected configuration.

[0062]

As described in detail above, according to the present invention,
A plurality of discharge fork-shaped electrodes are arranged opposite to each other in substantially the same plane, and a plurality of VHF-class power supplies, that is, 30 MHz to 200 MHz-class power supplies, which are independent from each other, are arranged behind two electrodes. By supplying these powers through the power supply terminal, a 1m × 1m to 2m × 2m size class large area substrate, which was considered impossible in the prior art, can be formed with extremely good film thickness distribution. A plasma chemical vapor deposition apparatus capable of forming a film of -Si, microcrystalline Si, or the like can be provided.

The above effect is not limited to the application of the a-Si thin film, but the plasma CVD technique using a high frequency power supply of a 30 MHz to 200 MHz class has a use as a manufacturing method of microcrystalline Si and thin film polycrystalline Si. , Solar cells, thin film transistors, photosensitive drums, and the like have an extremely large industrial value.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the outline of a plasma chemical vapor deposition apparatus (apparatus A) having a fork-type electrode according to an embodiment of the present invention.

FIG. 2 is a block perspective view showing a plasma chemical vapor deposition apparatus having a fork-type electrode according to an embodiment of the present invention.

FIG. 3A is a perspective view showing only one side of a fork-type electrode according to the embodiment, and FIG. 3B is a perspective view showing a pair of fork-type electrodes according to the embodiment;

FIG. 4 is a block perspective view showing a power supply circuit of a device (device B) according to another embodiment.

FIG. 5 is a characteristic diagram showing a correlation between a length direction distance of an electrode rod and a voltage on the electrode rod.

FIG. 6A is a three-dimensional distribution diagram of a film thickness distribution of amorphous silicon when VHF power is supplied to one side (reference electrode) of a fork-type electrode, and FIG. (C) is a three-dimensional distribution diagram of the thickness distribution of amorphous silicon when VHF power is supplied to the (opposite pole), and (c) is the third order of the thickness distribution of amorphous silicon synthesized from (a) and (b). Original distribution map.

FIG. 7 is a block sectional view showing a device (device C) of a comparative example.

FIG. 8 is a power supply circuit diagram of a comparative example device.

FIG. 9 is a block sectional view showing a device (device D) of a comparative example.

FIG. 10 is a characteristic diagram showing a correlation between a plasma power supply frequency and a film thickness distribution.

FIG. 11 is a power supply circuit diagram of a comparative example device.

12A is a schematic diagram illustrating a plasma distribution generated by a parallel plate electrode, and FIG. 12B is a schematic diagram illustrating another plasma distribution generated by a parallel plate electrode.

FIG. 13 is a perspective view showing a fork-type electrode according to another embodiment.

[Explanation of symbols]

9: substrate, 31: reactor, 32a, 32b, 32c: fork electrode, 33B: base, 33R: rib, 34: heater, 35a, 35b: impedance matching device, 36a, 36b: high frequency power supply, 37, 37a ... Reaction gas supply pipe, 38 ... supply pipe, 39 ... vacuum pump, 40 ... ground shield, 40a-40h, 41a-41h, 43a-43h ... coaxial cable, 44-47, 48-51 ... power supply end, 60a, 60b ... power distributors, 61a, 61b ... terminals, 71-76 ... T-type connectors.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hideo Yamakoshi 1-8-1 Koura, Kanazawa-ku, Yokohama-shi, Kanagawa Prefecture F-term in Mitsubishi Heavy Industries, Ltd. Basic Research Laboratory 4G075 AA24 BB02 BC01 BC04 BD14 CA47 FC13 4K030 AA06 BA29 BA30 BB04 BB05 CA06 FA03 JA18 KA15 LA15 LA16 LA17 5F045 AA08 AB03 AB04 AC01 AE15 AE17 EH04 EH06 EH09 EH20 EK21

Claims (11)

[Claims] 1. A plasma chemical vapor deposition apparatus for supplying electric power to an electrode from a high-frequency power source, generating discharge plasma of a film forming gas between the electrode and a substrate to be processed, and forming a film on the substrate to be processed. The electrode includes a plurality of power supply terminals connected to an output circuit of the power supply, a linear base on which the plurality of power supply terminals are mounted at substantially equal pitches, and a branch from the base. And a plurality of ribs extending substantially in parallel at substantially equal pitches and in parallel with each other. 2. The method according to claim 1, wherein the electrode comprises a combination electrode in which a pair of electrode members face each other, wherein ribs of one electrode member and ribs of the other electrode member are alternately arranged in substantially the same plane. The device according to claim 1, characterized in that: 3. A first power supply terminal of one of the electrode members has a first
3. The apparatus according to claim 2, wherein a second high-frequency power supply independent of said first high-frequency power supply is connected to each power supply terminal of said other electrode member. 4. A first power distributor provided between one of the electrode members and the first high-frequency power supply for distributing power to each of the power supply terminals, and the other electrode member and the first power distributor. 4. The apparatus according to claim 3, further comprising: a second power divider provided between the first and second high-frequency power sources and distributing power to the respective power supply terminals. 5. A plurality of first T-type connectors provided between one of the electrode members and the first high-frequency power supply for distributing power to the respective power supply terminals, and the other electrode member. 4. The apparatus according to claim 3, further comprising a plurality of second T-type connectors provided between the second high-frequency power supply and the power supply terminals to distribute power to the respective power supply terminals. 6. The apparatus of claim 1, wherein the power supply end is mounted where the rib branches off from the base. 7. The apparatus according to claim 1, wherein the electrode comprises a single base and a plurality of ribs branching from the single base and extending substantially in parallel. . 8. The apparatus of claim 7, comprising two independent high frequency power supplies respectively connected to a power supply end mounted on said single base and supplying power to a common electrode. 9. The electrode comprises a plurality of first power supply ends mounted on a single base, and a plurality of first power supply ends respectively attached to the free ends of the ribs corresponding to the first power supply ends. 8. The device of claim 7, comprising two power supply ends. 10. A power supply frequency of 30 MHz to 200 MHz.
2. The apparatus of claim 1, wherein z is in the range of z. 11. The apparatus according to claim 10, wherein an amorphous silicon-based film, a microcrystalline silicon-based film, and a polycrystalline silicon-based film are formed.