JP5308733B2 - Non-integrated cathode electrode and plasma CVD apparatus - Google Patents

Description

  The present invention uses a non-integrated cathode electrode for a plasma CVD apparatus for forming a semiconductor thin film such as microcrystalline Si or amorphous Si on the surface of a substrate by plasma CVD, and the non-integrated cathode electrode. The present invention relates to a plasma CVD apparatus.

Thin-film solar cells are considered to become the mainstream of solar cells that generate power using sunlight because they are thin, lightweight, inexpensive to manufacture, and easy to increase in area. In addition to this, demand is expanding for business use and general residential use that are installed on the roofs and windows of buildings.
As a method for manufacturing such a thin film solar cell, there are a roll-to-roll method in which layers are continuously formed on a substrate that moves continuously in each film forming chamber, and a substrate that is simultaneously stopped in each film forming chamber. There is a stepping roll method in which the substrate portion after film formation is sent to the next film formation chamber.

FIG. 5 is a schematic configuration diagram showing a thin film manufacturing apparatus of a stepping roll film forming system in which a plurality of film forming chambers are provided in a common vacuum chamber and a thin film is formed on one surface of a substrate that is conveyed vertically. is there. 6A and 6B are schematic configuration diagrams showing the details of the film forming chamber in FIG. 5, where FIG. 6A shows the substrate transport time, and FIG. 6B shows the film forming time.
The thin film manufacturing apparatus shown in FIG. 5 accommodates an unwinding chamber 53 in which an unwinding roll 52 around which a long flexible substrate 51 is wound is housed, and an unwinding roll 54 that winds up the flexible substrate 51. Between the winding chamber 55 and the unwinding chamber 53 and the winding chamber 55, the flexible substrate 51 is disposed along the conveying direction. The flexible substrate 51 has a metal electrode layer, a photoelectric conversion layer, and a transparent electrode. A film forming chamber 56 as a plurality of independent processing spaces provided for forming a thin film such as a layer is provided.
In such a thin film manufacturing apparatus, the flexible substrate 51 is unwound from the unwinding roll 52 in the unwinding chamber 53 and is wound on the winding roll 54 in the winding chamber 55. The film is formed in the chamber 56.

In each film forming chamber 56, as shown in FIG. 6, in order to form a thin film on the flexible substrate 51 by a plasma CVD method (plasma chemical vapor deposition method), a parallel plate to which a high voltage high frequency is applied. The cathode electrode (high frequency electrode) 57 and the anode electrode (ground electrode) 58 are arranged to face each other with a space therebetween. A high frequency power source 59 and a gas supply pipe 60 are connected to the cathode electrode 57, and the raw material gas introduced into the gas supply pipe 60 is formed from the surface of the cathode electrode 57 having a large number of holes as a shower electrode. It is supplied in the form of a shower. In the anode electrode (ground electrode) 58, a heater 58a for heating the flexible substrate 51 is incorporated.
The film forming chamber 56 includes an upper wall body 61 and a lower wall body 62 that are arranged to face the upper and lower sides of the flexible substrate 51 that is intermittently transported and form a box shape. At the time of film formation, as shown in FIG. 6B, the upper wall 61 is lowered, the flexible substrate 51 into which the anode electrode 58 is carried is pressed, and the opening side end of the lower wall 62 is sealed. Contact the member 63. Thus, an airtightly sealed film formation space 65 communicating with the exhaust pipe 64 is formed from the lower wall body 62 and the flexible substrate 51. In this state, by applying a high frequency voltage to the cathode electrode 57, plasma is generated in the film formation space 65, the raw material gas introduced into the gas supply pipe 60 is decomposed, and a thin film is formed on the surface of the flexible substrate 51. Then, film formation is performed.

  By the way, in the film formation of the plasma CVD method using the cathode electrode of a general parallel plate, as the film formation speed increases, dangling bonds of constituent atoms in the film, pinholes, etc. are generated. The film quality tends to deteriorate. For this reason, in order to obtain a good quality thin film, the film forming speed must be reduced, but there is a problem in maintaining desired mass productivity.

  Therefore, conventionally, by using a cathode electrode integrally provided with a complicated concavo-convex structure composed of grooves, a hollow cathode plasma is generated by the edge effect brought about by the concavo-convex structure, thereby forming a high-density plasma and a reactive gas. There has been provided a technique capable of forming a high-quality amorphous Si film at a high speed by increasing the decomposition efficiency and reducing the electron temperature (for example, Patent Document 1).

As for the pattern of the uneven structure of the cathode electrode, the surface of the cathode plate is formed by using a three-dimensional structure with unevenness in which long cylindrical recesses arranged in a grid are connected by grooves. There is also a technology that enables high-density microcrystalline Si film deposition at a high speed of about 7 to 10 nm / s by ejecting high density plasma from a long cylindrical recess on the cathode plate surface (for example, Patent Documents). 2).
Furthermore, a technique is also provided in which a plurality of protrusions are provided on the cathode electrode plate and gas supply holes are provided in these protrusions (for example, Patent Document 3).

JP-A-2-294482 Japanese Patent No. 3837539 JP 2004-200345 A

  However, the conventional cathode electrode in which such a concavo-convex structure is integrated is complicated and generally difficult to manufacture, so the cost is higher than that of a normal parallel plate electrode. Is obvious.

Also, normally, in the film formation by plasma CVD method, it is necessary to remove the cathode electrode from the plasma CVD apparatus and clean it by sandblasting or chemical etching from the viewpoint of quality maintenance. It is. However, when the cathode electrode has a complicated concavo-convex structure, a physical method such as sandblasting may damage a portion of the concavo-convex structure and cannot be said to be an appropriate treatment method. Further, even when the chemical etching method is used, when the cathode electrode itself is handled, there is a problem that the uneven structure is easily damaged by the dead weight of the cathode electrode.
Furthermore, since the conventional cathode electrode is integrated and heavy, it takes time to remove it from the plasma CVD apparatus, and the cleaning operation is troublesome, which causes problems in terms of maintenance and cleaning workability. In addition, when the cathode electrode is replaced, the entire electrode must be replaced, which causes a problem of increasing costs.

  The present invention has been made in view of such a situation, and its purpose is easy to manufacture, can be easily increased in area, easy to install and remove, and An object of the present invention is to provide a non-integrated cathode electrode and a plasma CVD apparatus which are excellent in maintainability and can be reduced in cost.

In order to solve the above-described problems of the prior art, the present invention provides a cathode electrode used when a thin film is formed on the surface of a substrate by a plasma CVD method, and a gas from which a raw material gas is introduced from a gas supply pipe Removably attached to the dispersion space forming part, and a shower head type flat plate electrode for allowing the source gas of the gas dispersion space forming part to flow out from the surface, and a plurality of gas flow holes are formed with the outer periphery as an outer frame part. A non-integrated cathode electrode configured by detachably fixing the partition plate with an outer frame to the shower head type flat plate electrode, and in the gas dispersion space forming portion, A gas dispersion space for uniformly dispersing the supplied source gas is provided, and in the gas dispersion space, a protruding piece projecting toward the gas supply pipe and the shower head are provided. A gas diffusion plate having diffusion holes provided at a density lower than that of the gas flow holes of the flat plate electrode is provided, and the gas diffusion space allows the gas dispersion space to be divided into the first space portion and the second space portion. The raw material gas that is defined and introduced is applied to the projection piece while being diffused in the lateral direction and supplied to the first space portion, and the raw material gas is supplied to the second space portion from the diffusion hole. Has been.

Further, in the present invention, specifically, the following configuration is preferable.
That is, two or more partition plates with an outer frame are overlapped and fixed to the shower head type flat plate electrode, and the gas flow holes of the partition plates with an outer frame to be stacked have a diameter and a shape. At least one is formed so as to be different from each other.

  On the other hand, the non-integrated cathode electrode of the present invention is used as a parallel plate cathode electrode for applying a high frequency voltage in a plasma CVD apparatus in order to form a thin film on the surface of a substrate by plasma CVD.

As described above, the non-integrated cathode electrode according to the present invention is a cathode electrode used when a thin film is formed on the surface of a substrate by plasma CVD, and is a gas dispersion in which a source gas is introduced from a gas supply pipe. A shower head type flat plate electrode that is detachably attached to the space forming portion and allows the source gas of the gas dispersion space forming portion to flow out from the surface, and a plurality of gas flow holes are formed in such a shape that the outer periphery is the outer frame portion. A partition plate with an outer frame, and is configured by removably fixing the partition plate with an outer frame to the shower head type flat plate electrode, and in the gas dispersion space forming part, the supplied source gas A gas dispersion space is provided to uniformly disperse the gas, and in the gas dispersion space, a protruding piece projecting toward the gas supply pipe and a gas flow hole of the shower head type flat plate electrode are provided. A gas diffusion plate having diffusion holes provided at a sparse density is disposed, and the gas diffusion space is defined by the gas diffusion plate into a first space portion and a second space portion, and the introduced source gas Is supplied to the first space part while being diffused in the lateral direction by being applied to the projecting piece, and the raw material gas is supplied to the second space part from the diffusion hole. A flat electrode having irregularities can be obtained. Moreover, the non-integrated cathode electrode of the present invention can be manufactured at a low cost and can form a high-quality thin film at a high speed by utilizing the hollow cathode effect. Similar effects can be obtained.

Moreover, since the cathode electrode of the present invention has a non-integral structure, it can be easily attached and removed during replacement or cleaning, and is excellent in maintainability. In addition, the area of the electrode can be easily increased according to the user's request. Therefore, the cost can be reduced.
Furthermore, since the partition plate with an outer frame of the non-integrated cathode electrode according to the present invention is light when removed from the shower head type flat plate electrode, it can be quickly and reliably cleaned by a chemical etching process, and the weight As in the case of an integrated cathode electrode, the uneven structure is not damaged by its own weight.

  And in the present invention, two or more partition plates with an outer frame are overlapped and fixed to the showerhead flat plate electrode, and the gas flow holes of the partition plates with an outer frame to be superimposed are: When at least one of the diameter and the shape is different from each other, a complicated three-dimensional space can be easily obtained, so that the cost can be reduced. In addition, according to the present invention, high-density plasma can be formed to increase the decomposition efficiency of the source gas, and an even higher quality thin film can be formed at high speed.

  On the other hand, when the non-integrated cathode electrode of the present invention is used as a parallel plate cathode electrode for applying a high-frequency voltage in a plasma CVD apparatus to form a thin film on the surface of the substrate by plasma CVD. Since a high-quality thin film can be formed at high speed, a plasma CVD apparatus with excellent production efficiency can be provided.

  Hereinafter, a non-integrated cathode electrode and a plasma CVD apparatus according to the present invention will be described in detail based on embodiments thereof with reference to the drawings.

FIG. 1 is a sectional view of a non-integrated cathode electrode according to an embodiment of the present invention, FIG. 2 is a plan view of a partition plate with an outer frame constituting the non-integrated cathode electrode in the present embodiment, and FIG. FIG. 4 is a plan view of a non-integrated cathode electrode in the present embodiment, and FIG. 4 is a plan view of a showerhead type flat plate electrode constituting the non-integrated cathode electrode.
A non-integrated cathode electrode 1 according to an embodiment of the present invention shown in FIG. 1 is a parallel plate that applies a high-frequency voltage in a plasma CVD apparatus to form a thin film on the surface of a flexible substrate by plasma CVD. It is used as a cathode electrode.

  Such a plasma CVD apparatus is configured to perform film formation by a stepping roll method, for example. That is, the plasma CVD apparatus to which the non-integrated cathode electrode according to the embodiment of the present invention is applied is not illustrated, but for example, in order from one end side to the other end side, the unwinding chamber, the plurality of film forming chambers, and A winding substrate is formed, and the flexible substrate unwound from the unwinding roll of the unwinding chamber enters each film forming chamber, and is temporarily stopped in the film forming chamber to form a film on each surface. After being performed, it is configured to be wound on a winding roll in a winding chamber. Therefore, in each film forming chamber, the non-integrated cathode electrode (high-frequency electrode) 1 of the present embodiment and an anode electrode (ground electrode) (not shown) are arranged to face each other with a gap therebetween. In the state where the anode electrode holds the flexible substrate and the film formation space is formed, a high frequency voltage is applied to the non-integrated cathode electrode 1 to generate plasma, and the supplied source gases (for example, silane and hydrogen) A thin film is formed on the surface of the flexible substrate by decomposing Si compound gas such as, and film formation is performed.

  The cathode electrode 1 of the present embodiment is non-integral as shown in FIG. 1 and is detachably attached to the gas dispersion space forming part 2 through which the source gas G is guided. The source gas in the gas dispersion space forming part 2 A shower head type flat plate electrode 3 for allowing G to flow out from the surface, and a partition plate 5 with an outer frame in which a plurality of gas flow holes 4 are formed in such a shape that the outer periphery forms an outer frame portion 5a. Then, the cathode electrode 1 is assembled by fixing the detachable partition plate 5 to the shower head type flat plate electrode 3 using screws (bolts, screws, etc.) 6 as fastening means. ,It is configured. That is, in the cathode electrode 1 of the present embodiment, the gas dispersion space forming portion 2, the shower head type flat plate electrode 3, and the partition plate 5 with an outer frame are formed separately.

The gas dispersion space forming portion 2 is formed in a substantially U-shaped cross section having an opening on one side, and a gas dispersion space 7 for uniformly dispersing the supplied source gas G is provided inside the recess. ing. Further, a gas supply pipe 8 that guides the source gas G to the gas dispersion space 7 is provided on the other side of the gas dispersion space forming section 2, and the tip of the gas supply pipe 8 communicates with the gas dispersion space 7, The base end of the gas supply pipe 8 is connected to a gas supply source (not shown).
In addition, a gas diffusion plate 10 having a projecting piece 10a and a diffusion hole 10b is disposed in the gas dispersion space 7, and the gas diffusion space 7 is formed between the first space portion 7a and the second space by the gas diffusion plate 10. It is defined in the space portion 7b. The gas diffusion plate 10 supplies the source gas G to the first space portion 7a of the gas dispersion space 7 while diffusing the source gas G introduced from the gas supply pipe 8 against the protrusions 10a in the lateral direction. This is an electrode component for uniformly diffusing the source gas G into the second space portion 7b from the diffusion holes 10b provided at a density lower than that of the gas flow holes 4 of the shower head type flat plate electrode 3.

  Further, as shown in FIG. 3, the shower head type flat plate electrode 3 uses a rectangular flat plate in plan view having a large number of small holes 9 so that the source gas G in the gas dispersion space 7 flows out in a shower shape. These small holes 9 are disposed so as to penetrate through, for example, a pattern (an arbitrary pattern is possible) in which adjacent small hole rows are located between them. Moreover, the shower head type flat electrode 3 of this embodiment is removably attached to the periphery of the opening part of the gas dispersion space formation part 2 using the screw etc. which are not illustrated. The shower head type flat plate electrode 3 is connected to a high frequency power source (not shown) as in the conventional example shown in FIG.

Furthermore, the partition plate 5 with the outer frame is formed by punching a metal plate or an alloy plate by a general machining method. That is, as shown in FIGS. 2 and 4, the partition plate 5 with the outer frame is formed using a rectangular plate having substantially the same dimensions in a plan view superimposed on the showerhead flat plate electrode 3. Inside the frame portion 5 a, a rectangular gas flow hole 4 in a plan view is formed at a position corresponding to the small hole 9 of the showerhead flat plate electrode 3. For this reason, the gas flow holes 4 are arranged to penetrate in the same pattern as the small holes 9.
When the partition plate 5 with the outer frame is detachably fixed to the shower head type flat plate electrode 3 by tightening the outer frame portion 5a with the screw 6 in a state of being superimposed on the shower head type flat plate electrode 3, The surface of the partition plate 5 with the outer frame protrudes from the surface of the shower head type flat plate electrode 3 through the inner peripheral edge of the gas flow hole 4 by the plate thickness. An uneven structure is formed by the surfaces of the gas flow holes 4 and the showerhead flat plate electrode 3. Therefore, also in the cathode electrode 1 of this embodiment, the edge effect brought about by this uneven structure can be obtained, thereby forming high-density plasma and increasing the decomposition efficiency of the source gas G.

In order to confirm the effect of the non-integrated cathode electrode 1 according to the embodiment of the present invention, a microcrystalline Si plasma is used by using the non-integrated cathode electrode 1 of the present embodiment and a general parallel plate electrode. The film formation speed in CVD was compared.
In addition, using a mixed gas of SiH4 and H2 (mixing ratio of about 1:33) as the raw material gas G, microcrystalline Si is formed by plasma CVD at a pressure of 10 Torr, a discharge frequency of 80 MHz, and a power of 125 W. Filmed.

According to this, the film formation rate by the non-integrated cathode electrode 1 of this embodiment was 2.5 nm / sec, whereas the film formation rate by a general parallel plate electrode was 2.3 nm / sec. there were. Further, the defect density of microcrystalline Si by the non-integrated cathode electrode 1 of this embodiment was 9 × 10 ¹⁵ cm ⁻³ , whereas the defect density of microcrystalline Si by a general parallel plate electrode is It was 5 × 10 ¹⁶ cm ⁻³ .
From the above results, in the plasma CVD apparatus using the non-integrated cathode electrode 1 according to the embodiment of the present invention, the hollow cathode effect is used and the quality is higher than that using a general parallel plate electrode. It was confirmed that the thin film can be formed at high speed.

As described above, in the non-integrated cathode electrode 1 of the embodiment of the present invention, the shower head type flat plate electrode 3 that is detachably attached to the gas dispersion space forming portion 2 and flows out the source gas G from the surface, and the outer periphery is provided. A partition plate 5 with an outer frame in which a plurality of gas flow holes 4 are formed in a shape that forms an outer frame portion 5a, and the partition plate 5 with the outer frame can be removed from the shower head type flat plate electrode 3 with screws 6. Since it is configured by fixing, it is possible to obtain a flat electrode having irregularities with a simple structure. In addition, the non-integrated cathode electrode 1 of the present embodiment can be manufactured inexpensively and easily, and a high-quality thin film can be formed at high speed using the hollow cathode effect.
In addition, since the cathode electrode 1 of the present embodiment has a non-integral structure, attachment work and removal work at the time of replacement and cleaning of the partition plate 5 with the outer frame and the shower head type flat plate electrode 3 are easily performed. And has excellent maintainability. In addition, the cathode electrode 1 having a large area can be obtained easily and at low cost according to the user's request.
Furthermore, since the partition plate 5 with the outer frame of the non-integrated cathode electrode 1 of the present embodiment is light when removed from the showerhead flat plate electrode 3, it can be quickly and reliably cleaned by chemical etching. In addition, the uneven structure is not damaged by its own weight as in the case of a heavy integrated cathode electrode.

  While the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications and changes can be made based on the technical idea of the present invention.

For example, although the stepping roll type plasma CVD apparatus is used in the above-described embodiment, a roll-to-roll type plasma CVD apparatus may be used. Moreover, although the partition plate 5 with an outer frame is overlapped and fixed to the shower head type flat plate electrode 3 of the embodiment described above, two or more partition plates 5 with an outer frame are stacked. It may be fixed.
In this case, it is preferable that the gas flow holes 4 of the partition plate 5 with the outer frame to be overlapped are formed so that at least one of the diameter and the shape is different from each other. According to such a configuration, a complicated three-dimensional space can be easily obtained. Therefore, according to the non-integrated cathode electrode 1 having such a structure, it is possible to form a further high-quality thin film at a high speed and reduce the cost.

It is sectional drawing which shows the non-integral type cathode electrode which concerns on embodiment of this invention. It is a top view which shows the partition plate with an outer frame which comprises the non-integral type cathode electrode in this embodiment. It is a top view which shows the shower head type flat electrode which comprises the non-integrated cathode electrode in this embodiment. It is a top view which shows the non-integrated cathode electrode in this embodiment. It is a schematic block diagram which shows an example of the conventional thin film manufacturing apparatus of the conventional stepping roll system. 5A and 5B show details of a film forming chamber of the general thin film manufacturing apparatus shown in FIG. 5, where FIG. 5A shows the substrate transport time, and FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Non-integrated cathode electrode 2 Gas dispersion space formation part 3 Shower head type flat plate electrode 4 Gas distribution hole 5 Partition plate with an outer frame 6 Screw 7 Gas dispersion space 8 Gas supply pipe 9 Small hole 10 Gas diffusion plate G Raw material gas

Claims (3)

A cathode electrode used when a thin film is formed on the surface of a substrate by a plasma CVD method. The cathode electrode is detachably attached to a gas dispersion space forming portion through which a source gas is guided from a gas supply pipe , and the gas dispersion space is formed. A shower head type flat plate electrode for flowing out the raw material gas from the surface; and a partition plate with an outer frame in which a plurality of gas flow holes are formed in a shape having an outer periphery as an outer frame part, the shower head type flat plate In the non-integrated cathode electrode configured by detachably fixing the partition plate with the outer frame to the electrode,
A gas dispersion space for uniformly dispersing the supplied source gas is provided in the gas dispersion space forming portion, and a protrusion piece protruding toward the gas supply pipe is provided in the gas dispersion space, and the shower head type A gas diffusion plate having diffusion holes provided at a density lower than that of the gas flow holes of the flat plate electrode is provided, and the gas diffusion plate defines the gas dispersion space into a first space portion and a second space portion. The introduced source gas is applied to the projection piece and diffused in the lateral direction while being supplied to the first space portion, and the source gas is supplied to the second space portion from the diffusion hole. nonintegrated cathode electrode, characterized in that is.   Two or more partition plates with an outer frame are overlapped and fixed to the shower head type flat plate electrode, and the gas flow hole of the partition plate with an outer frame to be overlapped is at least one of a diameter and a shape. The non-integrated cathode electrodes according to claim 1, wherein are formed so as to be different from each other.   The non-integral cathode electrode according to claim 1 or 2 is used as a parallel plate cathode electrode for applying a high-frequency voltage in order to form a thin film on the surface of a substrate by a plasma CVD method. A plasma CVD apparatus.

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