JP2003059840A - Apparatus and method for plasma treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for plasma treatment, capable of increasing the size of the treatment area, improving the treatment speed and improving the treatment quality. SOLUTION: The apparatus for plasma treating comprises a reaction vessel 4, a high-frequency electrode 20 provided in the vessel 4, and a dielectric 6 associated with the electrode 20. The electrode 20 has a plurality of small electrodes 21 to 24 separated from each other. High-frequency voltages, applied to at least two of the electrodes 21 to 24, are different in phases from each other. The dielectric 6 is protruded to a plasma-generating atmosphere side with respect to the electrodes 21 to 24. The strength distribution of an electric field which is applied by the electrode 20 can be made uniform by the dielectric 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus and a plasma processing method, and more specifically, to a plasma processing apparatus and a plasma processing suitable for performing film deposition, etching or surface modification on a member to be processed. Regarding the method.

[0002]

2. Description of the Related Art Today, in semiconductor device manufacturing processes, thin film deposition, etching, surface modification and other treatments using plasma energy are indispensable. In these plasma processing steps, it is important to increase the size of semiconductor devices such as liquid crystal displays and solar cells, and to increase the processing area and processing speed in response to the demand for improved processing capacity, and to improve processing quality. Is.

The current state of such plasma processing will be described. Taking the plasma CVD method, which is a typical film deposition method using plasma processing, as an example of the deposited film,
Typically, there are a polycrystalline thin film of silicon, a microcrystalline thin film, an amorphous thin film, and a silicon compound film such as a silicon oxide film, a silicon nitride film, and a metal silicide film. Plasma CV
In order to improve mass productivity in the D method, it is necessary to increase the film forming speed and increase the processing area. In order to increase the film formation rate, it is considered that the high frequency power is increased or the supply amount of the source gas is increased. On the other hand, it is known that, in order to increase the processing area, the influence of the standing wave generated on the electrode increases as the maximum surface dimension of the high-frequency electrode increases. As a result, the in-plane uniformity of plasma is deteriorated, which causes in-plane uniformity of film thickness and film characteristics in the case of film deposition, and in-plane uniformity of etching rate in the case of etching.

In order to solve the problem of non-uniformity of film thickness and film quality, Japanese Unexamined Patent Publication No. 62-130277 has a high frequency voltage applying flat plate electrode divided into a plurality of sections, and each section of the electrode. Disclosed is a plasma CVD apparatus including a power supply device for separately controlling a high-frequency voltage applied to the substrate. Such a conventional device, as shown in FIG.
Reaction chamber 201, distributor 231, power amplifiers 235, 23
6 and 237. The reaction chamber 201 includes split electrodes 240, 241 and 242, and an upper electrode 212.
Are arranged. Split electrodes 240, 241, and 24
The same high-frequency voltage is applied to each of the two from the power source 218. However, if necessary, the applied voltage of the power amplifier is adjusted so that the voltage of the split electrode at the central portion and the voltage of the split electrode at the peripheral end are extremely small. You may change it.

[0005]

However, as will be described later, even in the above-mentioned conventional apparatus, there has been found a problem that the processing effect (for example, film thickness) may be significantly different locally.

An object of the present invention is to provide a plasma processing apparatus and a plasma processing method which can solve the problems of the prior art and can increase the processing area, improve the processing speed, and improve the processing quality. Especially.

[0007]

The inventors of the present invention have disclosed in Japanese Patent Laid-Open No.
A detailed study was conducted on the effect of the technique of dividing the high-frequency electrode into a plurality as disclosed in JP-A-2-130277. The present inventors have found that the size of 40 cm as shown in FIG.
In a plasma processing apparatus having a high-frequency electrode composed of nine small electrodes 21 to 29, which are made of square stainless steel flat plates and are separated from each other by 10 mm, each small electrode has 10
The electric field strength distribution when high frequency power of 0 MHz was applied so as to have the same output and the same phase was obtained by electromagnetic field calculation.
Here, as shown in FIG. 1, the direction orthogonal to the small electrode surface is the x direction, and the two directions parallel to the small electrode surface orthogonal to the x direction are the y direction and the z direction. X obtained as a result of electromagnetic field calculation
The intensity distribution of the electric field Ex in the direction is shown in FIG. Near the center of the entire high-frequency electrode composed of multiple small electrodes (Fig. 3
(A part of), a distribution in which the electric field becomes excessive occurs. It is considered that this is caused by the high-frequency convolution applied to each small electrode. On the contrary, as shown in part B of FIG. 3, the electric field becomes too small in the gap between the adjacent small electrodes. From this, it is predicted that during plasma processing, excessive plasma will be generated near the center (portion A) and excessive plasma will be generated near the gap (portion B). It is clear that processing with such plasma causes problems in processing uniformity and quality. Therefore, in order to weaken the strong electric field in the portion A, electric power smaller than that of the other electrodes (60% of the electric power applied to the other electrodes) was applied to the small electrode 25 in the center. Figure 4
FIG. 8 shows the intensity distribution of the electric field Ex in the x direction when the power applied to the small electrode 25 at the center, which is obtained by the inventors of the present invention, is reduced. It can be seen that an excessive electric field as shown in part A of FIG. 3 is suppressed and a more uniform electric field intensity distribution can be obtained.

In order to examine the correlation between the uniform electric field distribution as shown in FIG. 4 and the actual film thickness distribution, a film forming experiment was conducted. The film thickness distribution obtained as a result is shown in FIG. The film thickness of the portion corresponding to the small electrode surface showed a uniform distribution similar to the calculation result of FIG. 4, but the film thickness tends to increase in the portion B corresponding to the gap between the adjacent small electrodes. Was given. Although it was predicted from the result of FIG. 4 that the electric field was small, the film thickness would be small.
The opposite result was obtained.

Therefore, a Langmuir probe is inserted from the port of the reaction vessel between the high frequency electrode and the member to be treated,
When the plasma electron density distribution was measured on the small electrode surface and in the portion B corresponding to the gap between the adjacent small electrodes, the electron density was measured in the portion B corresponding to the gap between the adjacent small electrodes as shown in FIG. It turned out to be getting bigger.

Therefore, as a result of calculation under the same conditions as in FIG. 4, not only the electric field Ex in the x direction but also the electric field Ey in the y direction and the electric field Ez in the z direction parallel to each small electrode are included in the electric field E = ( Ex ² + Ey ² + Ez ² ) ^1/2 is shown in FIG. It was found that the electric field E was rather strong at the B portion corresponding to the gap between the adjacent small electrodes. When the magnitude of the high-frequency voltage applied to the adjacent small electrodes is different, a strong electric field is generated in the gap due to the potential difference between the adjacent small electrodes, and as a result, excessive plasma is generated and the gap is generated in the gap. It is considered that the film thickness at the corresponding portion increased.

In order to solve the above problems, according to the present invention,
There is provided an apparatus for treating a predetermined member with plasma generated by applying a high frequency voltage in a reaction container. This plasma processing apparatus includes an electrode for applying a high frequency voltage, which is provided in a reaction container and is composed of a plurality of small electrodes separated from each other, and a plasma inserted between the plurality of small electrodes to generate a plasma. A dielectric having a higher dielectric constant than the atmosphere in which it is stored. In this device, the high frequency voltages applied to at least two of the plurality of small electrodes have different magnitudes. The dielectric can be arranged so that the intensity distribution of the electric field applied by the plurality of small electrodes is made uniform.

Further, in order to solve the above-mentioned problems, the present invention provides a method for treating a predetermined member with plasma generated by applying a high frequency voltage in a reaction vessel. This plasma processing method includes (a) a dielectric in which electrodes composed of a plurality of small electrodes separated from each other are provided in a reaction container for applying a high frequency voltage, and which has a higher dielectric constant than an atmosphere in which plasma is generated. Using a device in which the body is inserted between multiple small electrodes;
(B) forming an atmosphere for generating plasma in the reaction container, and (c) applying a high-frequency voltage to each of the plurality of small electrodes to form a predetermined member through the plasma generated from the atmosphere. Processing. In this method, the high frequency voltages applied to at least two of the plurality of small electrodes have different magnitudes. The dielectric can be arranged so that the intensity distribution of the electric field applied by the plurality of small electrodes is made uniform.

In a preferred aspect of the present invention, the dielectric material projects from the plurality of small electrodes toward the plasma generating atmosphere. More specifically, the dielectric can be made to project from the plurality of small electrodes toward the plasma generation atmosphere side with a length of 10 mm or less. In the present invention, the length of the dielectric protruding from the plurality of small electrodes toward the plasma generating atmosphere is
It may be partially different. In the present invention, the dielectric can have, for example, a shape that partially projects into the plasma generation atmosphere.

In the present invention, the dielectric can be divided into a plurality of parts. When dividing the dielectric into multiple
Adjacent to each of the plurality of small electrodes, each of the plurality of portions can be provided separately from each other. A conductor, typically a metal plate, can be disposed between adjacent portions of the dielectric.

In a preferred embodiment, the dielectric constant of the dielectric is 3 or more and 50 or less. Typically, the dielectric material is
At least one selected from the group consisting of alumina porcelain, quartz, glass, beryllia porcelain, and silicon carbide porcelain.
It is a seed.

In a preferred embodiment, the maximum size of the plurality of small electrodes is 1/4 or less of the high frequency wavelength. In the present invention, the frequency of the high frequency voltage is typically 20 to 500M.
In the Hz range.

The present invention is applied to plasma CVD, plasma etching, surface modification by plasma, and the like. In particular, the apparatus according to the present invention is suitable as a plasma CVD apparatus, and the method according to the present invention is suitable as a plasma CVD method, but is not limited thereto.

According to the invention, for example, a plasma CV
10% on a substrate with a maximum dimension of 1 m or more by D method
A thin film can be formed with a thickness distribution within the range. The thin film formed on such a substrate can form a semiconductor device such as a photoelectric conversion device. Here, the "thickness distribution" is obtained by dividing the thin film formed on the substrate into a predetermined number, for example, 81 pieces, and using the maximum value and the minimum value of the film thickness measured for the fragments, the expression {(maximum value- The minimum value) / (maximum value + minimum value)} × 100% can be used.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION When the magnitudes of high-frequency voltages applied to adjacent small electrodes are different from each other, a potential difference occurs between the adjacent small electrodes. For this reason, a stronger electric field (electric field in the y or z direction parallel to the small electrode surface) is generated in the gap between the small electrodes, that is, in the portion such as the area C shown in FIG.
Occurs. Due to the strong electric field, the plasma processing rate in the portion corresponding to the gap portion is increased, and nonuniform processing may occur.

Therefore, in order to weaken the electric field generated in the gap, a dielectric is inserted between the small electrodes. The inserted dielectric has a higher dielectric constant than the processing gas (atmosphere in which plasma is generated) having a relative dielectric constant equal to about 1. Such a dielectric easily takes in lines of electric force, and a strong electric field is applied to the dielectric. Therefore, the electric field in the process gas generated by the plasma becomes relatively weak, and
It is possible to weaken an excessive electric field applied near the inserted dielectric, that is, between adjacent small electrodes. As a result, the in-plane uniformity of plasma is improved.

In the present invention, the dielectric is arranged so as to make the intensity distribution of the electric field applied from the high frequency electrode uniform. In the present invention, the dielectric does not merely play a role of separating a plurality of small electrodes, but has a role of making the intensity distribution of the electric field generated by applying a high frequency voltage to each small electrode uniform. There is.

Further, in the present invention, the dielectric can be projected from the small electrode to the side of the member to be processed (the side of the space where plasma is generated). By occupying the region where a strong electric field is applied by the protruding dielectric, it is possible to prevent excessive plasma generation in the region.

Therefore, according to the present invention, the increase in plasma electron density in the region between the small electrodes can be suppressed more effectively, and the in-plane uniformity of plasma generation can be further improved. In particular, the main region where ionization and dissociation reactions occur in high-frequency plasma is near the boundary between the bulk part and the sheath part of the plasma, so the protruding length of the dielectric (the length of the dielectric protruding from the small electrode to the plasma generation space side) The amount of plasma ionization and the amount of dissociation reaction can be adjusted by adjusting the value of (a) to the sheath length, and the plasma electron density can be made uniform, and thus the plasma processing rate can be made uniform. Since the sheath length in the process plasma is typically 10 mm or less, it is preferable to adjust the protrusion length of the dielectric within a range of 10 mm or less, for example, 1 to 10 mm.

In the present invention, all or part of the dielectric can be projected from the small electrode. The in-plane uniformity of the plasma treatment can be further improved by adjusting the protrusion length of the dielectric depending on the place where the electric field becomes strong or weak.

In the present invention, the dielectric may be divided into a plurality of parts. By arranging the dielectric portion at an appropriate position, the electric field can be locally adjusted, and the effect of the plasma treatment can be further enhanced. Further, the division of the dielectric is preferable because it increases the degree of freedom of the device structure.

When the dielectric is divided into a plurality of parts, each part may be arranged for each small electrode. Each portion can be located adjacent to each small electrode. For example, each portion can be arranged to surround each small electrode. The parts are preferably separated from each other. In addition, a conductor, typically a metal, may be placed between adjacent portions of the dielectric. The parts can be arranged independently of each other. In such a structure, the position of the dielectric can be set for each small electrode according to process conditions, and as a result, an unnecessarily strong electric field can be suppressed for each small electrode. Such a structure can also contribute to a uniform plasma treatment effect.

In a preferred embodiment, the dielectric has a dielectric constant higher than that of the atmosphere in which plasma is generated, plasma resistance, and heat resistance. The dielectric constant of the dielectric is 3
-50 is preferable. Typically, dielectric materials include alumina porcelain, quartz, glass, beryllia porcelain, and silicon carbide based porcelain.

Further, in the present invention, it is preferable that the maximum size of each small electrode is ¼ or less of the wavelength of the applied high frequency wave. With such a size, it is possible to prevent a standing wave from being generated on each small electrode surface, and it is possible to perform more uniform plasma treatment on a member to be treated having a large area. The maximum dimension of the member to be treated means the longest distance between any two points on the surface of the member to be treated. For example,
In the case of a rectangular plate-shaped member, the length of the diagonal line becomes the maximum dimension, and in the case of a disk-shaped member, the diameter corresponds to the maximum dimension.

By setting the frequency of the high frequency voltage applied to each small electrode in the range of 20 to 500 MHz, the electron density in the plasma can be increased and the plasma potential can be suppressed to a low level, so that the processing speed can be increased. And the processing quality can be improved at the same time.

The plasma processing apparatus and plasma processing method according to the present invention are typically applied to plasma processing such as film deposition, etching, and surface modification in the manufacturing process of semiconductor devices. According to the present invention, the area to be processed can be increased, the processing speed can be improved, and the processing quality can be improved. According to the present invention, a high-performance semiconductor device can be manufactured at low cost.

The present invention will be further described below with reference to examples. The embodiment discloses a plasma CVD apparatus having a flat plate-shaped high-frequency electrode, which is divided into a plurality of rectangular and ladder-shaped small electrodes and arranged in parallel, but the present invention is limited to such an embodiment. Not something that is done. For example,
The shape of the small electrode is not limited to a square shape, but a rod shape,
It may be a disc type, a spherical type or the like, and the arrangement of the plurality of small electrodes is not limited to the parallel plate type, but may be a lattice type, a concentric circle type, or the like. Further, the plasma treatment is not limited to the film deposition such as the CVD, and the treatment quality can be similarly improved by applying the present invention to etching.

[0032]

EXAMPLES Example 1 FIG. 1 shows a schematic cross-sectional view of a plasma CVD apparatus used in this example. A flat plate-shaped high-frequency electrode 20 which is divided into a plurality of small electrodes 21 to 29 inside a stainless steel reaction container 4 to which a gas introduction unit 51 and a vacuum exhaust unit 52 are connected.
And the to-be-processed member disposition portion 31 made of stainless steel on which the to-be-processed member 3 is placed are arranged so as to be parallel to each other. The high frequency electrode 20 and the processed member disposition portion 31 form a pair of electrodes. Reaction container 4 and processing target member disposition part 31
Is electrically grounded. On the other hand, the high frequency electrode 20 including the small electrodes 21 to 29 is electrically insulated from the reaction container 4.

FIG. 2 shows a small electrode 2 constituting the high frequency electrode 20.
It is a perspective view of 1-29. Each small electrode is a 40 cm square stainless steel plate. The nine small electrodes are arranged in a square shape to form a flat plate-shaped high frequency electrode 20. Adjacent small electrodes are separated by 10 mm. As shown in FIG. 1, a dielectric 6 made of alumina porcelain having a relative dielectric constant of 9.7 is arranged in the gap. Small electrodes 21-2
9 are electrically isolated from each other.

FIG. 9 shows a perspective structure of the high frequency electrode and the dielectric in this embodiment. Surface of dielectric 6 and small electrodes 21-2
The relative distance of the surface of 9 is represented by xmm. In this example, the relative distance between the surface of the dielectric 6 and the surfaces of the small electrodes 21 to 29 was set to 0 mm. In this embodiment, the dielectric 6 almost completely fills the gap between the high frequency electrodes 20. Dielectric 6
Is in contact with the high-frequency electrode 20 and also with the wall of the reaction vessel 4 which is at ground potential. However, it is not essential to the invention that the dielectric contacts the high frequency electrode and the device wall. The effect of the present invention can be obtained even when the dielectric is not in contact with the high-frequency electrode or when it is not in contact with the device wall.

The high-frequency voltage oscillated from the high-frequency power source 1 is distributed by the distributor 8 to the nine high-frequency transmission lines, and the power regulators 91 to 99 and the power monitors 101 to 109 provided for the respective high-frequency transmission lines. And matcher 1
It is applied to each of the small electrodes 21 to 29 via 11 to 119. The value of the power monitors 101 to 109 provided for each of the small electrodes 21 to 29 is read as the power individually adjusted by the power regulators 91 to 99 configured by an electric circuit including an inductance, a capacitance, and a resistance,
By performing matching by the matching devices 111 to 119, the high frequency power applied to each of the small electrodes 21 to 29 is adjusted.
In this embodiment, the power applied to the small electrode 25 at the center is 60% of the power applied to the other small electrodes, that is, 0.12 Wc.
m ^-2 .

In this example, an amorphous silicon thin film was formed by using monosilane and hydrogen as source gases. The main film forming conditions are as follows. Workpiece member: Glass substrate (1 m square) Total gas flow rate: SiH ₄ 1300 sccm H ₂ 1800 sccm Substrate temperature: 200 ° C. High frequency power: 0.12 Wcm ^-2 (small electrode 25) 0.2 Wcm ^-2 (other than small electrode 25) Frequency : 100 MHz Film forming pressure: 50 Pa Distance between small electrode and member to be processed: 40 mm After the film forming process for 1 hour, the glass substrate on which the amorphous silicon thin film was deposited was taken out from the reaction container 4. As shown in FIG. 10, 81 samples of 6 cm square were cut out from the glass substrate to obtain film thickness measurement samples. In FIG.
The forty-nine shaded samples are the samples on the surface of the small electrode, and the white 32 samples are the samples just above the gaps of the small electrodes. As a result of measuring the film thickness at the center of all 81 samples using a step meter, the film thickness distribution was 10%, and the average film thickness was 900 nm. The film thickness distribution was 6% only with 49 samples on the small electrode surface. In addition, the film thickness distribution is calculated by a formula {(maximum film thickness-minimum film thickness) / for a predetermined number of samples.
(Maximum film thickness + minimum film thickness)} × 100%.

Comparative Example 1 With the structure in which the dielectric 6 was removed in FIG. 1, the other conditions were exactly the same as in Example 1, and the film thickness distribution of the formed sample was evaluated in the same manner as in Example 1. As a result, the film thickness distribution for all 81 samples was 15%. The film thickness distribution was 6% only with 49 samples on the small electrode surface.

In all the examples and comparative examples shown below, the film thickness distributions for all 81 samples are shown.

Examples 2 to 7 The film thickness when the arrangement of the dielectric 6 is changed and the relative distance between the surface of the dielectric 6 and the surfaces of the small electrodes 21 to 29 is changed under the same conditions as in Example 1. The distribution is shown in FIG. Regarding the position of the dielectric surface, the small electrode surface is set to 0 of the origin, and the direction (x direction) approaching the processed member 3 is expressed as a positive direction. x = -0.
Samples were prepared at 6 points of 5, 0.5, 1, 2, 3, 4 mm. The result is shown in FIG. FIG. 11 also shows the results of Example 1 in which the position of the dielectric surface is 0 mm and Comparative Example 1 in which the dielectric is not inserted.
Is plotted at the position of the dielectric surface-1 mm for convenience.

From FIG. 11, it was found that the film thickness distribution was reduced by inserting the dielectric material, as compared with Comparative Example 1 in which the dielectric material was not inserted. From FIG. 11, it is desirable that the dielectric material protrudes toward the member to be processed with respect to the electrode surface, and in particular, in this embodiment, the projection length is 3
When the thickness was less than or equal to mm, the film thickness distribution was as good as 10% or less, and when the protrusion length was 2 mm, the film thickness distribution was 7% at the minimum. Further, the film thickness distribution was 6% only with 49 samples on the small electrode surface when the protrusion length was 2 mm. Therefore, it can be understood that the nonuniformity of the film thickness immediately above the gap is almost eliminated by setting the appropriate protrusion length.

In this embodiment, the protrusion length of the dielectric is 3
When it exceeds mm, the film thickness in the gap becomes smaller than that in the small electrode surface. It was found that the film thickness in the gap tends to decrease as the dielectric protrusion length increases. It is considered that the effect of suppressing the electric field (electric field in the y and z directions) applied between the adjacent small electrodes is increased by increasing the protrusion length of the dielectric.

As a result of measuring the electron density on the small electrode surface by the Langmuir probe under the process conditions of Examples 1 to 7, the sheath thickness was about 3 in all Examples.
It was mm. In high-frequency plasma, the main region where ionization and dissociation reactions occur is near the boundary between the plasma bulk and the sheath.Therefore, adjusting the protrusion length of the dielectric up to the sheath length allows plasma ionization and It is thought that the amount of dissociation reaction can be adjusted.

Examples 8 to 12 Under the same conditions as in Example 1 except that the film forming pressure was 20 Pa, the arrangement of the dielectric 6 was changed and the surface of the dielectric 6 and the surfaces of the small electrodes 21 to 29 were changed. The relative distance (distance x shown in FIG. 9) was changed. Regarding the position of the dielectric surface, the small electrode surface is set to 0 as the origin, the direction (x direction) approaching the member to be processed is expressed as a positive direction, and samples are prepared at 5 points of x = 0, 5, 8, 10, 12 mm. did.

Comparative Example 2 As Comparative Example 2, the structure in which the dielectric 6 was removed and the other conditions were exactly the same as in Examples 8 to 12, and the film thickness distribution of the sample formed was evaluated.

FIG. 12 shows the film thickness distribution of Examples 8 to 12 and Comparative Example 2 in which no dielectric material was inserted. Comparative Example 2 is plotted at the position of the dielectric surface-1 mm for convenience.

From FIGS. 12A and 12B, in Examples 8 to 12, when the protrusion length was 8 mm, the film thickness distribution was 7%, which was the minimum, and when the protrusion length was 10 mm or less, the film thickness distribution was 10% or less. It showed a numerical value. As a result of measuring the electron density on the small electrode surface by the Langmuir probe under the process conditions of Examples 8 to 12, the sheath thickness was about 10 mm in all Examples.

From the above results, since the sheath thickness changes depending on the process conditions, the optimum protrusion length of the dielectric changes, but by adjusting the protrusion length up to about the sheath thickness, a good film thickness can be obtained. It turns out that the distribution can be obtained.

Example 13 Instead of the 40 cm square stainless steel flat plate small electrodes 21 to 29 used in Example 1, a stainless steel square rod-shaped member was welded as shown in FIG. 13 and processed into a ladder type. Small electrode 1
21 to 129 were used. The size of the ladder type small electrode is 40c
The square rod-shaped member had a thickness of 15 mm, and the gap between adjacent rod-shaped members was 15 mm. Under the same conditions as in Example 1, the protrusion length of the dielectric 6 was adjusted so that the film thickness distribution was minimized, and as a result of film formation, the film thickness distribution was 8%.

The rod-shaped member is not limited to the square type, but may be a round type or a thin plate type. In addition, when a reaction gas flows between both main surfaces of the electrode like a ladder type electrode,
Excessive plasma is generated in the gaps on both main surfaces of the electrode, and as a result, film deposition species, etching species, etc. generated from the non-uniform plasma move back and forth to both main surfaces, resulting in non-uniform plasma processing. Become. Therefore, in the case where plasma is generated on both main surfaces of the electrode, it is more effective that the dielectric material protrudes toward the plasma side of the electrodes on both main surfaces.

Example 14 As shown in FIG. 14, the dielectric 6 inserted in the high frequency electrode portion was divided into a dielectric 61 around the small electrode 25 in the center and a dielectric 62 other than the dielectric 61. The dielectric 61 was projected 3 mm from the small electrode surface, and the dielectric 62 was projected 2 mm from the small electrode surface. As a result of forming a film under the same conditions as in Example 1,
The film thickness distribution was 6%. By forming a gap structure in the dielectric and selectively increasing the protrusion length of the central portion of the dielectric, it becomes possible to further uniformize the film thickness.

Embodiment 15 As shown in FIG.
Divided into two. The dielectrics 161 to 169 are installed so as to surround the side surfaces of the nine small electrodes 21 to 29, respectively. Further, the side surfaces of the dielectrics 161 to 169 were surrounded by stainless steel flat plates 131 to 139, respectively. The stainless steel flat plates 131 to 139 were set to the same potential as the wall of the reaction container 4. In this embodiment, the dielectrics 161 to 169 are in contact with the high frequency electrodes 21 to 29 and also with the flat plates 131 to 139 made of stainless steel. Dielectrics 161-16
9 are arranged independently of each other. 2 from the small electrode surface
The dielectrics 161 to 169 were projected with a length of mm. When a sample was manufactured under the same conditions as in Example 1, the film thickness distribution of the sample was 7%. With this structure, an electric field applied between adjacent small electrodes can be suppressed for each small electrode. By arranging each dielectric portion independently for each small electrode, it is possible to set the optimum electrode-dielectric arrangement according to process conditions.

Here, it is not essential to set the flat plates 131 to 139 to the same potential as the device wall, and another mode may be used as long as a strong electric field applied between adjacent small electrodes can be suppressed. For example, a certain constant voltage may be applied to the flat plates 131 to 139, or the flat plates 131 to 139 may have a floating potential. Further, the dielectrics 131 to 169 are high-frequency electrodes 21 to 29 and the stainless steel flat plates 131 to 131.
It is not essential that the small electrode 21 is in contact with the 139.
Flat plate 1 made of stainless steel even when not in contact with ~ 29
The effects of the present invention can be obtained even when not in contact with 31 to 139.

Examples 16 to 21 In the same electrode structure as in Example 1, the dielectric 6 was glass having a relative permittivity of 3, quartz having a relative permittivity of 3.8, and a relative permittivity of 6.
5 was changed to beryllia porcelain, silicon carbide porcelain having a relative permittivity of 50, and titanium oxide porcelain having a relative permittivity of 90. A film of a sample when the relative distance between the dielectric 6 surface and the small electrodes 21 to 24 surface is set so that the film thickness distribution becomes the smallest in each material under the same film forming conditions as in Example 1. The thickness distribution is shown in FIG. FIG. 16 also shows the results of the alumina porcelain having a relative permittivity of 9.7 of Example 1 and the relative permittivity of 1 in which the dielectric body of Comparative Example 2 was not inserted.

Since it is possible to prevent a strong electric field from being applied to the dielectric and to prevent a strong electric field from being applied to the gap, FIG.
As shown in (1), a better film thickness distribution could be obtained when each dielectric was inserted, as compared with the case where the relative dielectric constant was 1 in which no dielectric was inserted. Preferably, the dielectric constant of the dielectric material is in the range of 3 to 50, and the film thickness distribution in that range is 10%.
Within was good.

Teflon (R) resin having a relative dielectric constant of about 2 can also be used by applying a surface coating or the like for improving plasma resistance.

In each of the above-described embodiments, the square small electrodes or the ladder-shaped small electrodes arranged is used, but the small electrodes may have various shapes such as a rectangle, a polygon and a circle. Good. Further, when the maximum size of each small electrode is ¼ or less of the wavelength of the applied high frequency voltage, a particularly remarkable effect is obtained.

In each of the embodiments, the power is distributed from one high frequency power source and applied to a plurality of small electrodes, but the power source is connected for each electrode or for each group of several small electrodes. You may.

Example 22 In this example, a thin film solar cell was manufactured by using the plasma CVD apparatus shown in FIG. 1 to form a photoelectric conversion layer made of an amorphous silicon thin film. The protrusion length of the dielectric from the small electrode was set to 2 mm. FIG. 17 shows a schematic cross-sectional view of the thin film solar cell manufactured in this example. A glass substrate 100 cm square and 1.1 mm thick was used as the substrate 141, and ZnO was formed thereon as the transparent electrode 142 by a sputtering method so as to have a film thickness of about 1 μm.
Then, the substrate 141 is placed inside the reaction container 4 of the plasma CVD apparatus shown in FIG. 1 so that the side on which the transparent electrode 142 is formed faces the high frequency electrode composed of a plurality of small electrodes. A p-type amorphous silicon thin film 143 having a film thickness of 30 nm, an i-type amorphous silicon thin film 144 having a film thickness of 300 nm, and an n-type amorphous silicon thin film 145 having a film thickness of 30 nm are sequentially formed on the transparent electrode 142. Thus, the photoelectric conversion layer was formed.
The film forming conditions for the p-type, i-type, and n-type amorphous silicon thin films are shown below. In addition, the frequency of the applied high frequency is 100 MHz in any case.

Film-forming conditions for p-type amorphous silicon thin film High frequency power: 0.03 W / cm ² (small electrode 25) 0.05 W / cm ² (other than small electrode 25) Source gas: SiH ₄ 150 sccm H ₂ 1500 sccm B ₂ H ₆ (2.0% / H ₂ ) 300 sccm Film forming pressure: 50 Pa Substrate temperature: 200 ° C. Distance between small electrode and target member: 40 mm Projection length of dielectric from small electrode: 2 mm i-type amorphous Film forming conditions for silicon thin film High frequency power: 0.12 W / cm ² (small electrode 25) 0.2 W / cm ² (other than small electrode 25) Source gas: SiH ₄ 600 sccm H ₂ 900 sccm Film forming pressure: 50 Pa Substrate temperature: 200 ℃ distance between the small electrodes and the workpiece member: 40 mm dielectric protrusion length from the small electrodes: 2 mm n-type film forming conditions high frequency power of the amorphous silicon thin film: 0.024W / cm ² ( Electrode 25) 0.04 W / cm ² (small electrodes 25 than) the source _{gas: SiH 4 100sccm H 2 1200sccm PH} 3 (2.0% / H 2) 100sccm Film Pressure: 50 Pa substrate temperature: 200 ° C. under a small electrodes Distance from processing member: 40 mm Projection length from small dielectric electrode: 2 mm Substrate 141 was taken out from reaction vessel, and then back electrode 14
As No. 6, Ag was formed by sputtering to have a thickness of 300 nm. The back surface electrode 146 also has a role of improving the power generation efficiency by reflecting the light once transmitted through the photoelectric conversion layer.

For each glass substrate, 9 × 9 unit cells (4 cm square) were prepared, and the distribution of photoelectric conversion efficiency was measured. FIG. 18 shows the variation when the average value of the photoelectric conversion efficiencies in 81 unit cells is 1.

Comparative Example 3 In the plasma CVD apparatus shown in FIG. 1, film formation was performed under the same conditions as in Example 22 with the structure in which the dielectric 6 was removed. FIG. 19 shows the variation in the photoelectric conversion efficiency in the obtained 81 unit cells.

The variation in photoelectric conversion efficiency of the thin film solar cell produced by using the plasma CVD apparatus of the present invention is small,
It was confirmed that the yield can be improved by the plasma CVD apparatus and the plasma CVD method of the present invention.

In the present embodiment, the plasma CVD apparatus and the plasma CVD method of the present invention were applied to the manufacturing process of a thin film solar cell using an amorphous silicon thin film as a photoelectric conversion layer, but the application of the present invention is not limited to this. Absent. For example, in forming a polycrystalline silicon thin film, or etching an amorphous silicon thin film or a polycrystalline silicon thin film, by using the present invention, an area to be processed corresponding to an increase in the size of a semiconductor device or an improvement in processing capability can be obtained. It is possible to increase the size, improve the processing speed, and improve the processing quality. As described above, according to the present invention, yield, reliability, and mass productivity can be improved in plasma processing steps such as film deposition and etching. The present invention can be applied not only to the manufacturing process of a thin film solar cell, but also to the manufacturing process of thin film transistors and the like.

[0064]

As described above, according to the present invention,
In a device that applies high-frequency voltages of different sizes to a plurality of small electrodes, application of an excessive electric field can be controlled by appropriately disposing a dielectric. According to the present invention, it is possible to easily obtain an optimum processing effect by controlling locally excessively generated plasma.

According to the present invention, in the film forming step and the etching step in the semiconductor device manufacturing process, the area to be processed is increased, the processing speed is improved, and the processing quality is improved in response to the increase in the size of the semiconductor device and the improvement in the processing capacity. As a result, yield, reliability, and mass productivity can be improved.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a plasma CVD apparatus that is one embodiment of the present invention.

FIG. 2 is a perspective view showing a small electrode to which a high frequency voltage is applied in the plasma CVD apparatus.

FIG. 3 is a diagram showing an intensity distribution of an electric field from a high frequency electrode toward a member to be processed in a conventional plasma CVD method.

FIG. 4 is a diagram showing an intensity distribution of an electric field from a high-frequency electrode to a member to be processed when high-frequency voltages having different magnitudes are applied to a plurality of small electrodes in a plasma CVD apparatus.

5 is a diagram showing a film thickness distribution of a deposited sample in the case shown in FIG.

6 is a diagram showing a plasma electron density distribution in the plasma CVD apparatus in the case shown in FIG.

FIG. 7 is a diagram showing an electric field strength distribution on a high frequency electrode surface in the case shown in FIG.

FIG. 8 is a schematic sectional view of a plasma CVD apparatus.

FIG. 9 is a perspective view showing an arrangement of a high frequency electrode and a dielectric according to the present invention.

FIG. 10 is a diagram showing a portion where a sample is cut out from a substrate on which a film is formed.

FIG. 11 is a diagram showing the relationship between the protrusion length from the small electrode surface and the film thickness distribution of the dielectrics according to Examples 1 to 7 and Comparative Example 1.

FIG. 12 is a diagram showing a relationship between a projection length from a small electrode surface and a film thickness distribution of dielectrics according to Examples 8 to 12 and Comparative Example 2.

FIG. 13 is a perspective view showing a high-frequency electrode composed of a ladder-type small electrode.

FIG. 14 is a perspective view showing another high frequency electrode-dielectric structure according to the present invention.

FIG. 15 is a plan view showing another high-frequency electrode-dielectric structure according to the present invention.

FIG. 16 is a diagram showing a relationship between a relative dielectric constant of a dielectric material inserted in a gap between high frequency electrodes and a film thickness distribution.

FIG. 17 is a schematic cross-sectional view of a thin film solar cell manufactured in Example 22.

FIG. 18 is a diagram showing a variation in photoelectric conversion efficiency in the thin film solar cell manufactured in Example 22.

FIG. 19 is a diagram showing variations in photoelectric conversion efficiency in the thin-film solar cell manufactured in Comparative Example 3.

FIG. 20 is a schematic sectional view of a conventional plasma CVD apparatus.

[Explanation of symbols]

1 high frequency power source, 3 processed material, 4 reaction vessel, 6,
61, 62, 161-169 Dielectrics, 8 distributors, 2
0 high-frequency electrode, 21 to 29 small electrodes, 31 treated member disposing portion, 51 gas introducing means, 52 gas exhausting means, 9
1-99 power regulator, 101-109 power monitor,
111-119 Matching device, 121-129 Ladder type small electrode, 131-139 Flat plate made of stainless steel, 141
Glass substrate, 142 transparent electrode, 143 p-type amorphous silicon thin film, 144 i-type amorphous silicon thin film, 145
n-type amorphous silicon thin film, 146 back electrode.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Haruki Morita             22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka             Inside the company F-term (reference) 4K030 FA03 JA01 JA18 KA14 KA30                       KA46                 5F045 AA08 AB04 AC01 AF07 BB01                       CA13 DP02 EH04 EH08 EH14                       EH19 EH20

Claims (15)

[Claims] 1. An apparatus for treating a predetermined member with plasma generated by applying a high-frequency voltage in a reaction container, comprising: a plurality of small electrodes provided in the reaction container and separated from each other. An electrode for applying the high-frequency voltage, and a dielectric having a higher dielectric constant than the atmosphere in which the plasma is generated, the electrode being inserted between the plurality of small electrodes. The plasma processing apparatus is characterized in that the high-frequency voltages applied to at least two of them have different magnitudes. 2. The plasma processing apparatus according to claim 1, wherein the dielectric is projected from the plurality of small electrodes toward the atmosphere. 3. The plasma processing apparatus according to claim 1, wherein the dielectric material protrudes from the plurality of small electrodes toward the atmosphere with a length of 10 mm or less. 4. The plasma processing apparatus according to claim 2, wherein the lengths of the dielectrics protruding from the plurality of small electrodes toward the atmosphere are partially different. . 5. The plasma processing apparatus according to claim 1, wherein the dielectric is divided into a plurality of parts. 6. The plasma processing apparatus according to claim 5, wherein each of the plurality of portions is provided adjacent to each of the plurality of small electrodes and apart from each other. 7. A conductor is disposed between a plurality of adjacent portions of the dielectric body,
The plasma processing apparatus according to claim 6. 8. The plasma processing apparatus according to claim 1, wherein the dielectric constant of the dielectric is 3 or more and 50 or less. 9. The material of the dielectric is at least one selected from the group consisting of alumina porcelain, quartz, glass, beryllia porcelain, and silicon carbide porcelain. The plasma processing apparatus according to claim 1. 10. The plasma processing apparatus according to claim 1, wherein the maximum size of the plurality of small electrodes is ¼ or less of the wavelength of the high frequency. 11. The high frequency voltage has a frequency of 20 to 50.
It is in the range of 0 MHz.
0. The plasma processing apparatus according to any one of 0. 12. The plasma processing apparatus according to claim 1, wherein the plasma processing apparatus is a plasma CVD apparatus. 13. A method for treating a predetermined member with plasma generated by application of a high frequency voltage in a reaction container, wherein electrodes comprising a plurality of small electrodes separated from each other apply the high frequency voltage. For using a device provided in the reaction vessel and having a dielectric constant higher than that of the atmosphere in which the plasma is generated is inserted between the plurality of small electrodes; To form an atmosphere for generating the plasma, and processing a predetermined member through the plasma generated from the atmosphere by applying a high-frequency voltage to each of the plurality of small electrodes, The high-frequency voltage applied to at least two of the plurality of small electrodes has different magnitudes from each other. Law. 14. The frequency of the high frequency voltage is 20 to 50.
14. The plasma processing method according to claim 13, wherein the plasma processing method is in the range of 0 MHz. 15. The plasma processing method according to claim 14, wherein a thin film is formed by a plasma CVD method on a substrate having a maximum dimension of 1 m or more with a thickness distribution of 10% or less.