JP3068604B2 - Plasma CVD 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 plasma CVD (chemical vapor deposition) apparatus, and more particularly, to an amorphous silicon solar cell,
The present invention relates to a plasma CVD apparatus used for manufacturing thin films used for various electronic devices such as microcrystalline solar cells, thin-film polycrystalline solar cells, thin-film semiconductors, optical sensors, and semiconductor protective films.

[0002]

2. Description of the Related Art Amorphous silicon (hereinafter a-Si)
Two typical examples of the configuration of a plasma CVD apparatus conventionally used for producing a thin film, a microcrystalline thin film, a thin film polycrystal, and a silicon nitride (hereinafter, referred to as SiNx) thin film will be described. . That is, a method using a ladder-shaped electrode, that is, an electrode also called a ladder antenna electrode or a ladder inductance electrode or a ladder-shaped planar coil electrode, as an electrode used for generating discharge,
A method using parallel plate electrodes will be described.

First, as for a method using a ladder-type electrode, Japanese Patent Application Laid-Open No. Hei 4-236781 discloses a plasma CVD apparatus using electrodes of various shapes as a ladder-type electrode. A representative example of this method will be described with reference to FIG. Reference numeral 1 in the figure denotes a reaction vessel, in which a discharge ladder electrode 2 and a substrate heating heater 3 are arranged in parallel. The discharge ladder electrode 2 is supplied with, for example, 13.56 MHz high frequency power from a high frequency power supply 4 via an impedance matching device 5. The discharge ladder electrode 2 has one end connected to the high frequency power supply 4 via the impedance matching device 5 as shown in FIG. 22, the other end connected to the ground wire 7, and grounded together with the reaction vessel 1. I have.

The high-frequency power supplied to the discharge ladder electrode 2 generates a glow discharge plasma between the substrate heating heater 3 and the discharge ladder electrode 2 which are grounded together with the reaction vessel 1, and passes through the discharge space. Flows to the wall of the reaction vessel 1 and to the 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.

In the reaction vessel 1, a mixed gas of, for example, 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 and held on the substrate heating heater 3;
It is deposited on the substrate 9 heated to a predetermined temperature. The gas in the reaction vessel 1 is passed through the exhaust pipe 10 to the vacuum pump 1.
1 to be exhausted.

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.

In this state, when high-frequency power is applied from the high-frequency power supply 4 to the discharge ladder electrode 2, glow discharge plasma is generated. The reaction gas is decomposed by a glow discharge plasma generated between the discharge ladder electrode 2 and the substrate heating heater 3, and as a result, Si gas such as SiH ₃ or SiH ₂ is formed.
Is generated and adheres to the surface of the substrate 9 to cause a-S
An i thin 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. The high frequency electrode 22 is supplied with, for example, 13.56 MHz high frequency power from a high frequency 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 heating heater 23,
It 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, the monosilane gas is decomposed by glow discharge plasma generated between the high-frequency electrode 22 and the heater 23 for heating the substrate. As a result, radicals containing Si, such as SiH ₃ and SiH _2, are generated and adhere to the surface of the substrate 29, forming an a-Si thin film.

[0012]

However, the prior arts, that is, the method using a ladder electrode and the method using a parallel plate electrode all have the following problems. (1) In FIG. 21, a reaction gas, for example, SiH ₄ is converted to Si, SiH, by an electric field generated near the ladder electrode 2.
It is decomposed into SiH ₂ , SiH ₃ , H, H _2, etc., and forms an a-Si film on the surface of the substrate 9. However, a-Si
In order to increase the film formation speed, the frequency of the high-frequency power source is increased from the current 13.56 MHz to 30 MHz to 200 MHz.
When the frequency is increased to a very high frequency band (VHF band: Very High Frequency), the uniformity of the electric field distribution near the ladder-shaped electrode is lost, and as a result, the thickness distribution of the a-Si film becomes extremely poor. There is. FIG. 24 shows a substrate area 30c.
The relationship between the plasma power supply frequency at mx 30 cm and the film thickness distribution is shown. The size, ie, the area, of the substrate that can ensure the uniformity of the film thickness distribution (within ± 10%) is 5 cm × 5 cm to 20 cm.
About 20 cm.

The reason why it is difficult to increase the frequency of the high-frequency power supply 4 by using a ladder electrode is as follows. FIG.
As shown in FIG. 5, due to the non-uniformity of impedance caused by the structure of the ladder-shaped electrode, a portion where plasma emission is strong is localized. For example, strong plasma is generated at the periphery of the electrode, but not at the center. Especially 6
The decrease becomes remarkable as the frequency becomes higher than 0 MHz.

Therefore, it is very difficult and impossible to improve the film forming speed by increasing the frequency of the plasma power supply for a large-area substrate necessary for improving mass productivity and reducing costs. Since the deposition rate of a-Si is proportional to the square of the frequency of the plasma power supply, researches have been actively conducted by academic societies in related technical fields.
cm or more) has not yet been obtained.

(2) Referring to FIG.
Due to the electric field generated between the substrate and the heater 23,
Reaction gas, for example, SiH_FourIs Si, SiH, SiH_Two, S
iH _Three, H, H_TwoEtc., and a-
An Si film is formed. However, high a-Si film formation
In order to increase the speed, the frequency of the high frequency
More than 30MHz to 200MHz from 3.56MHz
Increase to high frequency band (VHF band: Very High Frequency)
Occurs between the high-frequency electrode 22 and the heater 23 for heating the substrate.
The uniformity of the resulting electric field distribution is lost.
The problem is that the film thickness distribution of the Si film becomes extremely poor.
You. FIG. 24 shows a plasm with a substrate area of 30 cm × 30 cm.
Relationship between power frequency and film thickness distribution (deviation from average film thickness)
FIG. Uniformity of film thickness distribution (± 10% or less
The size, that is, the area of the substrate that can secure (in) is 5 cm × 5
cm to 20 cm × 20 cm.

The reason why it is difficult to increase the frequency of the high-frequency power supply 24 by using a method using parallel plate electrodes is as follows. Since the parallel plate type electrode has different electric characteristics between the electrode peripheral portion and the central portion, a strong plasma is generated at the electrode peripheral portion as shown in FIG. 26A, or the central plasma as shown in FIG. 26B. There is a reality that a strong plasma is generated only in a part.

Therefore, it is extremely difficult and impossible to improve the film formation speed by increasing the frequency of the plasma power supply for a large-area substrate necessary for improving mass productivity and reducing costs. Since the film formation rate of a-Si is proportional to the square of the plasma power supply frequency, research has been actively conducted by academic societies in related technical fields.
(30cm or more) has not been obtained yet.

Also, as shown in FIG.
It was found that when the ground line 7 was used, the plasma at the junction between the ground line 7 and the electrode 2 was weakened, and the deposition rate was reduced.

The present invention has been made in view of such circumstances, and has a configuration in which a coaxial cable is used as a discharge electrode for a power supply line connecting a ladder-type electrode and a power source, and the ladder-type electrode is not grounded by a ground line. Accordingly, it is an object of the present invention to provide a plasma CVD apparatus capable of preventing a reduction in the film formation rate.

The present invention also provides a feed point, which is a position for connecting the ladder-type electrode and the coaxial cable, at a peripheral portion or an inner peripheral portion of the planar coil electrode, and has at least four or more power supply points. Accordingly, it is an object of the present invention to provide a plasma CVD apparatus capable of obtaining a better film thickness distribution as compared with the related art.

[0021]

[0022]

In order to achieve the object of the present onset to achieve the above purpose
The invention of claim [1] provides a reaction vessel and the reaction vessel.
Means for introducing and discharging a reaction gas into the reaction vessel;
Ladder electrode for discharge housed from
An antenna-type electrode or a ladder-like planar coil electrode
Power supply for supplying power for glow discharge generation to ladder-type electrodes
Having an amorphous surface on the surface of the substrate installed in the reaction vessel.
To form porous thin films, microcrystalline thin films, or polycrystalline thin films
In the plasma CVD apparatus, a power supply point, which is a position for connecting the ladder-type electrode and the coaxial cable, is located at a peripheral portion of the ladder-type electrode, and the number thereof is at least four. Here, the position of the power supply point is, specifically, two or more locations on the upper, lower, left, and right sides of the ladder electrode, that is, for example, two locations on each of the upper and lower sides, for a total of four locations, or each of the left and right sides. It is preferable to make a total of eight locations for each four locations.

[0023] The invention of claim 2 provides a reaction container,
A means for introducing and discharging a reaction gas into a reaction vessel;
Ladder electrode for discharge housed from inside the reaction vessel,
Ladder antenna type electrode or ladder-shaped flat coil
Provides power for glow discharge generation to the pole and this ladder electrode
And a substrate table installed in the reaction vessel.
Amorphous thin film or microcrystalline thin film or polycrystalline thin film
In the plasma CVD apparatus for forming the above, the feeding point which is a position for connecting the ladder-type electrode and the coaxial cable,
The ladder-type electrode is located inside a peripheral portion of the ladder-type electrode, and the number thereof is at least four. here,
Specifically, the positions of the power supply points are preferably four to eight at the center of the inner periphery of the peripheral part of the ladder electrode.

[0024] invention [Claim 3], according to claim 1 or 2, the frequency of the power supply for supplying power glow discharge generating the 30MHz to 200MHz on the ladder-type electrode
Characterized in that was. Here, the frequency of the power supply is 30
MHz to 150 MHz.

According to a fourth aspect of the present invention, in the third aspect , a frequency of a power supply for supplying power for generating glow discharge to the ladder-shaped electrode is 85 MHz to 200 MHz, and a ladder having a wire diameter of 0.5 to 5 mm. It is characterized in that a mold electrode is used.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A plasma CVD apparatus according to one embodiment of the present invention will be described below with reference to FIGS. Here, FIG. 1 is an overall view of the device, and FIG. 2 is an explanatory diagram showing an electric wiring for supplying high-frequency power to a discharge electrode showing one configuration of the device.

Reference numeral 31 in the drawing denotes a reaction vessel. In the reaction vessel 31, a ladder-type SUS304 discharge electrode (ladder-type electrode) 32 for generating glow discharge plasma and a substrate 33 as an object to be processed are supported, and the temperature of the substrate 33 is controlled. Substrate heating heater 34 to be controlled
Is arranged. The discharge electrode 32 is made of a SUS rod having an outer size of 572 mm × 572 mm and a diameter of 6 mm, and the center interval is 26 mm.

A high frequency power supply 36 is connected to the discharge electrode 32 via an impedance matching device 35.
For example, electric power of a frequency of 13.56 MHz to 200 MHz is supplied to the discharge electrode 32 from the high frequency power supply 36. In the reaction vessel 31, a reaction gas introduction pipe 37 having a reaction gas discharge hole 37a for introducing a reaction gas around the discharge electrode 32 is arranged. The reaction vessel 31
Is connected to a vacuum pump 39 via an exhaust pipe 38 for exhausting a gas such as a reaction gas in the reaction vessel 31.

An earth shield 40 is provided in the reaction vessel 31. The earth shield 40 suppresses electric discharge in unnecessary portions, and is used in combination with the exhaust pipe 38 and the vacuum pump 39, so that SiH ₄ or the like introduced from the reaction gas introduction pipe 37 is used. After the reaction gas is turned into plasma by the discharge electrode 32, the reaction gas and other products are discharged through the exhaust pipe 38. The pressure in the reaction vessel 31 is monitored by a pressure gauge (not shown) and controlled by adjusting the displacement of the vacuum pump 39.

As shown in FIG. 2, four power supply terminals 41, 42, 4 are provided on the upper and lower sides of the discharge electrode 32, respectively.
3, 44, 45, 46, 47 and 48 are welded.
Between the discharge electrode 32 and the impedance matching unit 35, four 2-pin current introduction terminals 49, 50, 51, 5
2 are arranged respectively. From the high-frequency power source 36, for example, power of a frequency of 60 MHz or 80 MHz is supplied via the impedance matching unit 35 and, for example, eight coaxial cables 61, 62, 63, 64, 65, 66, 67,
68, the current introducing terminals 49 to 52 and eight vacuum coaxial cables 53, 54, 55, 56, 57, 58, 5
9, 60, the power is supplied to the power supply terminals 41 to 48. Here, the number of the power supply terminals is four or more, and the ground wire is not connected.

Another example of a ladder-type discharge electrode used in the plasma CVD apparatus shown in FIG. 2 is shown in FIG.
To FIG. 9, the present invention is not limited to the following. The ladder-shaped discharge electrodes shown in FIGS. 3 to 9 have different positions and numbers of the power supply terminals. The discharge electrode 32A shown in FIG. 3 has a configuration in which two power supply terminals 32a and 32b are arranged, one each at the center of the upper side and the center of the lower side. The discharge electrode 32B shown in FIG. 4 has two power supply terminals 32a, 3 at each of three equal positions on the left side and the upper side.
2b, 32c, and 32d are arranged.
The discharge electrode 32C shown in FIG. 5 has two power supply terminals 32a at three equal positions on the upper side and the lower side, for a total of four power supply terminals 32a,
32b, 32c, and 32d are arranged.

The discharge electrode 32D shown in FIG. 6 has a total of four power supply terminals 32a, 32b, 3 at four corners.
2c and 32d are arranged. The discharge electrode 32 </ b> E shown in FIG. 7 has a configuration in which eight power supply terminals 32 a to 32 h are arranged, one each at four corners and at the center of the upper side, lower side, left side, and right side. The discharge electrode 32F shown in FIG. 8 has four corners and one at each of three equal positions on the left and right sides, for a total of 8 electrodes.
The power supply terminals 32a to 32h are arranged. The discharge electrode 32G shown in FIG. 9 has four corner portions and one at each of three equal positions on the upper side and the lower side.
The configuration is such that a total of eight power supply terminals 32a to 32h are arranged.

Next, a method for manufacturing an a-Si film using the plasma CVD apparatus having the above configuration will be described. Here, when SiH ₄ plasma is generated at the discharge electrode 32, SiH ₃ , SiH ₂ , SiH present in the plasma are generated.
And the like are diffused by a diffusion phenomenon and are adsorbed on the surface of the substrate 33, thereby forming an a-Si film or microcrystal S.
i or thin film polycrystalline Si is deposited. Note that a-Si
It is a known technique that the film or microcrystalline Si and the 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. Here, an a-Si film formation using SiH ₄ gas will be described as an example. Of course, it is also possible to form microcrystalline Si and thin-film polycrystalline Si.

First, in the apparatus shown in FIG. 1, the inside of the reaction vessel 31 is evacuated by operating the vacuum pump 39, and the ultimate vacuum degree is set to 2-3 × 10 ^-7 Torr. Subsequently, a reaction gas, for example, a SiH ₄ gas is supplied through a reaction gas introduction pipe 37 to 80.
It is supplied at a flow rate of about 200 cc / min. Thereafter, high-frequency power is supplied from the high-frequency power supply 36 to the discharge electrode 32 via the impedance matching device 35 while maintaining the pressure in the reaction vessel 31 at 0.05 to 0.1 Torr. As a result, glow discharge plasma of SiH ₄ is generated near the discharge electrode 32. This plasma decomposes the SiH ₄ gas to form an a-Si film on the surface of the substrate 33. However, the deposition rate depends on the frequency and output of the high frequency power supply 36, but is about 0.5 to 3 nm / s.

FIG. 10 shows a glass substrate having an area of 40 cm × 50 cm (trade name: Corning # 7059, manufactured by Corning Incorporated) using the discharge electrode 32 shown in FIGS. Shows the result of forming the a-Si film. Here, the film formation conditions are SiH ₄
The gas flow rate was 700 cc / min, the pressure was 0.2 Torr, and the high frequency power was 500 W. According to FIG. 10, when the number of power supply terminals is two, the film thickness distribution is ± 26%. When the number of power supply terminals is four, the film thickness distribution is ± 14%. The distribution is ± 6%, which is a very good result.

FIG. 11 shows a glass substrate having an area of 40 cm.times.50 cm (trade name: Corning # 7059, manufactured by Corning Incorporated) using the discharge electrode 32 shown in FIGS. 3 shows an example of the result of forming an a-Si film. Here, the film forming conditions are as follows: SiH ₄ gas flow rate 700 cc / min, pressure 0.2 To.
rr, high-frequency power 500 W. According to FIG. 11, when the number of power supply terminals is two, the film thickness distribution is ± 30%, but when the number is four, the film thickness distribution is ± 18%, and when the number is eight, the film thickness distribution is ± 30%. The distribution is ± 8%, which is a very good result.

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. According to the above embodiment, a total of four or more, preferably eight or more power supply terminals are provided around the ladder-shaped electrode used as the discharge electrode, so that 60 MHz and 80 MHz are used.
As compared with the conventional apparatus and method, it is possible to obtain a significantly better film thickness distribution. In particular, when the frequency of the high frequency power supply 36 is 60 MHz, the substrate size is 40 cm × 50 c.
With m, a film thickness distribution within ± 10% was realized. This means that the industrial value related to improvement in productivity and cost reduction in the field of manufacturing a-Si solar cells, thin film transistor (TFT) driven liquid crystal displays, a-Si photoconductors, etc. is extremely large. .

On the other hand, in a conventional plasma deposition apparatus, 30
When a high-frequency power supply of MHz or higher is used, the film thickness distribution is extremely poor, and it has been difficult to commercialize a large-area substrate of about 30 cm × 30 cm to 50 cm × 50 cm or more.

Next, a description will be given of a ladder-type discharge electrode capable of rapidly forming a uniform film when the frequency of the high-frequency power supply is set to an ultra-high frequency band of 100 MHz or more where the plasma density is higher. In the case where the power supply point is provided in the peripheral portion of the electrode as in the discharge electrodes of FIGS.
When using a high-frequency power supply at MHz or higher, the plasma density is good, but the film thickness distribution deteriorates. Therefore, in the present invention, a power supply point is provided in the central portion inside the peripheral portion of the discharge electrode, and this is solved. And Thereby, 30cm x 30c
A film can be satisfactorily formed even on a large area substrate of about m to 50 cm × 50 cm or more.

As a discharge electrode 32 used in the plasma CVD apparatus shown in FIG. 2, a typical ladder-type discharge electrode having a feeding point inside the peripheral portion is shown in FIGS.
3, the present invention is not limited to the following. The ladder-type discharge electrode shown in FIG. 12A is a plan view of the above-described discharge electrode 32D shown in FIG. 6, and four power supply terminals 32 are provided at four corners.
a, 32b, 32c, and 32d are arranged. A ladder-shaped discharge electrode 132 shown in FIG.
A has a configuration in which a total of four power supply terminals 132a, 132b, 132c, and 132d are arranged in a rectangular shape in the central portion inside the peripheral portion of the electrode. A ladder-shaped discharge electrode 132B shown in FIG. 12C has a total of four power supply terminals 132a and 132 at the center inside the periphery of the electrode.
b, 132c and 132d are arranged, and
Four terminals 132e obliquely between the terminal 2a and the terminal 132c.
~ 132h are arranged, and a total of eight power supply terminals are arranged.

The ladder-shaped discharge electrode 132C shown in FIG. 13A has a configuration in which a total of eight power supply terminals 132a to 132h are arranged obliquely at the center inside the periphery of the electrode. . The ladder-shaped discharge electrode 132D shown in FIG. 13B has a total of 4 at the central portion inside the peripheral portion of the electrode.
Power supply terminals 132a, 132b, 132c, 13
2d is arranged in a rectangular shape, and further, four terminals 132e to 132h are arranged in a rectangular shape inside, and a total of eight power supply terminals are arranged. The ladder-shaped discharge electrode 132E shown in FIG. 13C has a total of four power supply terminals 132a, 132 at the center inside the periphery of the electrode.
2b, 132c, and 132d are arranged in a rectangular shape, and six terminals 132e to 132j are arranged obliquely between the terminal 132a and the terminal 132c, so that a total of ten power supply terminals are arranged. I have. It is preferable that the number of terminals disposed inside the peripheral portion of the discharge electrode is at least four or more. However, if the number is too large, there is a power division loss, which is not preferable. May be set as appropriate according to the wire diameter and interval.

FIG. 14 shows the relative values of the plasma density distribution when the frequency of the high-frequency power supply is set to a super-high frequency band of 120 MHz using the electrodes shown in FIGS. 12 (A) to 12 (C).
17 to FIG. 15 shows the electrode (four corners (four points)) in FIG. 12A, FIG. 16 shows the electrode (center (four points)) in FIG. 12B, and FIG. 17 shows the electrode in FIG. (Center (8 points)). The results are summarized, and the result of calculating the deviation value (deviation from the average value) of the plasma density is shown in FIG.
4 is shown. Here, the discharge electrode 32 is 40 cm × 40 cm.
The average of the plasma density distribution on the substrate (30 cm × 30 cm) was obtained.

The measurement conditions in FIG. 14 are H ₂ plasma,
The frequency of the high frequency power supply is 120 MHz, and the area is 30 cm.
× 30 cm glass substrate (product name: Corning # 705)
9, manufactured by Corning Incorporated) shows the results of forming an a-Si film. Here, the film forming condition is a SiH ₄ gas flow rate of 50 sc.
c / min, pressure 50 mTorr, high frequency power 150 W. As shown in FIG. 14, FIG.
The discharge electrodes 132A and 132B having the configuration shown in FIG.
It was found that the density distribution was extremely good even when the frequency was set to 120 MHz, as compared with the discharge electrode 32D shown in FIG. In particular, FIG.
The density distribution of the discharge electrode 132B shown in (C) was good in flatness. As a result, at least 4
It has been found that by arranging more than one power supply terminal, a uniform film can be quickly formed even in a high ultrahigh frequency band.

Next, the frequency of the high frequency power supply 36 is set to 100 M
A description will be given of a ladder-type discharge electrode capable of rapidly forming a uniform film in the case of an ultrahigh frequency band having a high plasma density of not less than Hz. In the discharge electrodes of FIGS. 12 and 13, a feed point was provided in the center of the inner side of the periphery of the electrode, and it was shown that good film formation was possible even in the case of an ultra-high frequency band. This problem can be solved by reducing the wire diameter of the discharge electrode, which will be described below.

FIG. 18 is a perspective view of FIG.
In the present embodiment, the electrode has a circular cross section and a wire diameter of 3 mm. The general wire diameter is 6 mm as described in the above-described embodiment, but in the case of 6 mm, when the frequency of the high-frequency power supply 36 is 85 MHz or more,
There is a problem that the plasma density distribution is not uniform.

FIG. 19 shows the relationship between the wire diameter (mm) of the ladder-type electrode and the deviation value of the plasma density. The wire diameter of the electrode is variously changed, and the frequency of the high frequency power supply is set to 120 MHz.
This is a deviation value of the plasma density when z is set. For this reason, as shown in FIG.
By thinning the film, a film having a uniform thickness can be formed quickly.

FIG. 20 shows that the electrode has a circular cross section and a wire diameter of 3 mm, the electrode has a circular cross section and a wire diameter of 6 mm, and the electrode has a rectangular cross section and a wire diameter of 3 mm. When the cross-sectional shape is circular and the wire diameter is 12 mm,
The measured values of the density distribution at different measurement positions when four terminals are arranged at the center of each electrode are shown. FIG.
Are the results of forming an a-Si film on a glass substrate (trade name: Corning # 7059, manufactured by Corning Incorporated) having an area of 30 cm × 30 cm using H ₂ plasma at a frequency of a high frequency power supply of 120 MHz. Here, the film formation conditions are as follows: SiH ₄ gas flow rate 50 scc / min, pressure 50 m
Torr, high frequency power 150 W. In addition, it measured in the direction of a broken line in a figure, and ● shows a feeding point.

As a result, the wire diameter was 5 mm compared to the wire diameter of 6 mm.
mm, a 10% improvement was observed. It was found that the finer the wire diameter, the better. However, when the wire diameter was less than 0.5 mm, the mechanical strength was weakened and no further improvement in the distribution was observed.

Therefore, the wire diameter of the discharge electrode is set to 85 MHz in consideration of mechanical strength and power consumption.
At 200 MHz of z or more, it is preferable that the width be 0.5 mm to 5 mm. As a result, by setting the wire diameter of the discharge electrode to 0.5 mm to 5 mm, even when the ultra-high frequency band of 85 MHz or more and 200 MHz is used, 3
It has become possible to form a film satisfactorily and quickly even on a large area substrate of about 0 cm × 30 cm to about 60 cm × 60 cm or more.

[0050]

[0051]

As described in detail above, the invention of [Claim 1]
According to the present invention, the feeding point, which is the position connecting the ladder-type electrode and the coaxial cable, is located at the periphery of the ladder-type electrode, and the number thereof is at least four or more, so that a better film thickness than the conventional one can be obtained. A plasma CVD apparatus capable of obtaining a distribution can be provided.

According to the second and third aspects of the present invention, the feeding point, which is a position for connecting the ladder-type electrode and the coaxial cable, is located inside the peripheral portion of the ladder-type electrode. By setting the number to at least four, a good film can be quickly obtained even at an ultra-high frequency.

According to the invention of claim 4 , the frequency of the power supply for supplying the power for generating the glow discharge to the ladder electrode is 85 MHz to 200 MHz, and the wire diameter is 0.5 to 200 MHz.
Since a 5 mm ladder-type electrode is used, a uniform and good film can be obtained quickly even at an ultra-high frequency.

[Brief description of the drawings]

FIG. 1 is an overall view of a plasma CVD apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing electric wiring for supplying high-frequency power to a discharge electrode showing one configuration of the apparatus of FIG. 1;

FIG. 3 is an explanatory view in the case where a power supply terminal is provided on each of the upper side and the lower side in the discharge electrode according to the present invention.

FIG. 4 is an explanatory diagram in a case where two power supply terminals are provided on each of an upper side and a lower side in the discharge electrode according to the present invention.

FIG. 5 is an explanatory diagram in a case where a total of four power supply terminals are provided, two on each of an upper side and a lower side, in the discharge electrode according to the present invention.

FIG. 6 is an explanatory diagram in the case where a total of four power supply terminals are provided, one for each corner, in the discharge electrode according to the present invention.

FIG. 7 is an explanatory view of a case where a total of eight power supply terminals are provided in the discharge electrode according to the present invention, one for each of the corner portion and the upper, lower, left, and right sides.

FIG. 8 is an explanatory view showing a case where the discharge electrode according to the present invention includes four corner portions, and four power supply terminals are provided on the left and right sides, respectively, for a total of eight power supply terminals.

FIG. 9 is an explanatory diagram of a discharge electrode according to the present invention in which four power supply terminals are provided, including four corner portions, four on each of the upper side and the lower side.

FIG. 10 is a characteristic diagram showing a relationship between a feeding point and a film thickness distribution when the device of the present invention is used under the conditions of a frequency of 60 MHz and a power of 500 W.

FIG. 11 is a characteristic diagram showing a relationship between a feeding point and a film thickness distribution when the device of the present invention is used under the conditions of a frequency of 80 MHz and a power of 500 W.

FIG. 12 shows a discharge electrode according to the present invention, in which four power supply terminals are provided at four corners (A), four power supply terminals are provided at the center (B), and eight at the center. It is explanatory drawing in case (C) when the electric power supply terminal is provided.

FIG. 13 shows a discharge electrode according to the present invention.
Explanatory drawing of a case where eight power supply terminals are provided (A), eight power supply terminals are provided at the center (B), and ten power supply terminals are provided at the center (C) It is.

FIG. 14 is a characteristic diagram showing a relationship between a power supply position and a plasma density distribution when the apparatus of the present invention is used under a condition of a frequency of 120 MHz.

FIG. 15 shows a condition under a frequency of 120 MHz.
It is a figure of the plasma density distribution using the electrode of (A).

FIG. 16 shows a condition under a frequency of 120 MHz.
It is a figure of the plasma density distribution using the electrode of (B).

FIG. 17 shows a condition under a frequency of 120 MHz.
It is a plasma density distribution figure using the electrode of (C).

FIG. 18 is a perspective view of the electrode (wire diameter: 3 mm) of FIG.

FIG. 19 is a characteristic diagram showing a relationship between a wire diameter and a plasma density distribution when the apparatus of the present invention is used under a condition of a frequency of 120 MHz.

FIG. 20 shows a condition under a condition of a frequency of 120 MHz.
FIG. 9B is an actual measurement diagram of a plasma density distribution due to a change in wire diameter using the electrode of FIG.

FIG. 21 is an overall view of a conventional plasma CVD apparatus using a ladder inductance electrode.

FIG. 22 is an explanatory diagram of electric wiring for supplying high-frequency power to a discharge electrode, which is one component of the device of FIG. 22.

FIG. 23 shows a conventional plasma CVD using parallel plate electrodes.
1 is an overall view of an apparatus.

FIG. 24 is a characteristic diagram showing a relationship between a plasma power supply frequency and a film thickness distribution in a conventional apparatus.

FIG. 25 is a diagram for explaining non-uniformity of impedance in the conventional device of FIG. 21;

26 is a diagram for explaining a difference in electric characteristics between a peripheral portion and a central portion of an electrode in the conventional device of FIG. 23;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 31 Reaction container 32 Discharge electrode 32A-32G Discharge electrode 33 Substrate 34 Substrate heat dissipation heater 35 Impedance matching device 36 High frequency power supply 37 Reaction gas introduction pipe 38 Exhaust pipe 39 Vacuum pump 40 Earth shield 41-48 Power supply terminal 49-52 Power introduction terminal 53-60 Coaxial cable for vacuum 61-68 Coaxial cable 132A-132E Electrode for discharge

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshikazu Nawata 1-1, Akunoura-cho, Nagasaki-shi, Nagasaki Mitsubishi Heavy Industries, Ltd. Nagasaki Shipyard (72) Inventor Kazuhiko Ogawa 1-1-1, Akunoura-cho, Nagasaki-shi, Nagasaki Mitsubishi Heavy Industries, Ltd., Nagasaki Shipyard (72) Inventor Hiroshi Majima 5-717-1, Fukahori-cho, Nagasaki, Nagasaki Prefecture Mitsubishi Heavy Industries, Ltd., Nagasaki Research Institute (72) Inventor Hirohisa Yoshida 5-717, Fukahori-cho, Nagasaki, Nagasaki Prefecture No. 1 Mitsubishi Heavy Industries, Ltd. Nagasaki Research Laboratory (56) References JP-A-8-253864 (JP, A) JP-A-62-130277 (JP, A) JP-A-7-263356 (JP, A) JP Hei 6-77144 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/205 C23C 16/50 H01L 21/31 H05H 1/46

Claims (4)

(57) [Claims] 1. A reaction vessel, means for introducing and discharging a reaction gas into and from the reaction vessel, and a ladder-type electrode for discharge, that is, a ladder antenna-type electrode or a ladder-like planar coil electrode housed from inside the reaction vessel. And a power source for supplying power for generating glow discharge to the ladder-type electrode, and a plasma C for forming an amorphous thin film, a microcrystalline thin film, or a thin film polycrystal on the surface of a substrate provided in the reaction vessel.
In the VD device, a position where the ladder-type electrode and the coaxial cable are connected.
Power supply point is located around the ladder-type electrode, and
The number is at least four.
Zuma CVD equipment. 2. A reaction vessel, and a reaction gas is supplied to the reaction vessel.
Means for introducing and discharging, housed from within the reaction vessel
Ladder type electrode for discharge, that is, ladder antenna type electrode
Alternatively, a ladder-shaped flat coil electrode and this ladder-shaped electrode
And a power supply for supplying power for generating glow discharge to the poles.
Amorphous thin film or substrate on the surface of the substrate installed in the reaction vessel
Is a plasma C forming a microcrystalline thin film or a thin film polycrystal.
In the VD device, a position where the ladder-type electrode and the coaxial cable are connected.
Feed point is located inside the periphery of the ladder electrode.
And the number is at least four.
Plasma CVD apparatus. 3. The method of claim 1 or 2, a plasma CVD apparatus, wherein a frequency of the power supply for supplying power for glow discharge generation in the ladder-type electrode was set to 30MHz to 200 MHz. 4. The ladder-shaped electrode according to claim 3 , wherein a frequency of a power supply for supplying power for generating glow discharge to the ladder-shaped electrode is 85 MHz to 200 MHz, and a wire diameter is 0.5 to 5 mm. A plasma CVD apparatus characterized by the above-mentioned.