JP2004111550A - Dummy substrate and vacuum-treating device fixing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make the plasma of a cleaning gas uniform even under a high plasma density. <P>SOLUTION: A conductive raising member 12 having an upper surface 13 positioned to a prescribed height from the surface 10a of a dummy substrate 10 which is fixed to an electrode instead of a substrate to be subjected to film formation at the time of self-cleaning a vacuum-treating device is attached to the surface 10a excluding the peripheral edge section of the surface 10a. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a vacuum processing apparatus, and more particularly to a vacuum processing apparatus for a large area substrate such as a plasma CVD apparatus for forming a film for forming a solar cell element.
[0002]
[Prior art]
In the manufacturing process of a solar cell, there is a step of forming an amorphous silicon film on the surface of a substrate, and this amorphous silicon film is usually formed using a plasma CVD apparatus.
[0003]
As shown in FIG. 5, this type of plasma CVD apparatus has a pair of electrodes 3 and 4 provided in a vacuum vessel 1 so as to face each other and connected to a high-frequency power supply 2.
Then, for example, silane gas (SiH ₄ ) is supplied as a raw material gas into the vacuum vessel 1, and a high frequency (for example, 13.56 MHz to 100 MHz) voltage is applied between the electrodes 3 and 4 so that the electrodes 3 and 4 are applied. A plasma of mainly a silane gas (SiH ₄ ), which is a source gas, is formed in between, and a radical (primarily a SiH ₄ radical) of the source gas generated at this time is used to form a surface of a rectangular plate-shaped substrate 5 made of, for example, glass Then, a Si film is formed.
[0004]
The one electrode 3 also functions as a source gas supply unit, has a hollow portion into which a source gas supplied from the outside flows, and is formed on a surface facing the other electrode 4. It has a large number of holes 3a, and a raw material gas is supplied between the electrodes 3 and 4 through these holes 3a.
More specifically, as shown in FIG. 6, one of the electrodes 3 is located at both ends thereof and has a pair of pipe-shaped pairs having a plurality of power supply positions 3d to which the high frequency power from the high frequency power supply 2 is supplied. And a ladder-type gas pipe electrode comprising a plurality of parallel pipe members 3c each of which has a plurality of holes 3a and electrically connects the pair of power supply rods 3b, 3b. And serves both of a gas supply function and a plasma generation electrode function (however, in the present invention, the electrode 3 may also serve as a gas supply function and a plasma generation electrode function, or may have separate functions. What you have may be installed individually).
[0005]
The other electrode 4 on the ground side has a substrate 5 placed on its surface. In order to maintain good adhesion between the substrate 5 and the electrode 4, the other electrode 4 is in contact with the periphery of the substrate 5. It has a conductive pressing plate 6 for pressing the lever against the electrode 4.
Heaters 7 are provided on the back side of the electrodes 4 so as to face each other, and the electrodes 4 are heated by the heaters 7. This is because by maintaining the substrate 5 at a predetermined temperature via the electrode 4, the formation of a film on the surface of the substrate 5 can be made easy and high quality. Note that the electrode 4 also functions as a heater cover for plasma.
[0006]
At the time of film formation using the plasma CVD apparatus as described above, components other than the substrate 5 in the vacuum vessel 1 (for example, portions of the electrode 3 and the electrode 4 that are not covered by the substrate 5 and the holding plate 6). Also, a Si film is formed, and the thickness of the Si film increases with each predetermined film forming process, and finally, the Si film is peeled off due to a difference in thermal expansion coefficient with the constituent members in the vacuum vessel 1.
This may cause problems such as damage to the film being formed on the surface of the substrate 5 and increase in defects. Therefore, such a plasma CVD apparatus periodically performs cleaning. It is necessary to remove the Si film attached to components other than the substrate 5 by performing a process.
[0007]
A self-cleaning method has been proposed as a method in which the cleaning process at this time is performed rationally in a short time without releasing the vacuum state of the vacuum vessel 1 and replacing the cleaning target part with a spare part.
In the self-cleaning method, instead of a raw material gas, an F-based gas such as NF ₃ is supplied as a cleaning gas into the vacuum vessel 1 and then the plasma (F plasma) is formed between the electrodes 3 and 4. The F radicals generated thereby act on the Si film to generate and exhaust SiF ₄ gas. For example, see Patent Document 1.
This self-cleaning is usually performed in a state where the substrate 5 is not fixed to the electrode 4 because the substrate 5 is etched by F radicals if the substrate 5 is a glass substrate containing SiO ₂ as a main component.
[0008]
[Patent Document 1]
JP-A-2002-57110 (FIG. 13 and the like)
[0009]
[Problems to be solved by the invention]
By the way, in a self-cleaning process using a plasma of a cleaning gas, in the case of a vacuum processing apparatus in which a substrate 5 having a large area exceeding 1 m on a side is used as a film formation target, a large area between the electrodes 3 and 4 is also used. It is difficult to generate plasma uniformly. Particularly, when the supply power for plasma generation is 2 kW / m ² or more and the plasma density is high, the F plasma of the F-based gas concentrates on the once generated portion. For this reason, the F plasma was localized, and cleaning distribution (cleaning unevenness) was likely to occur.
On the other hand, in order to suppress the localization of plasma generation as described above, the plasma density may be reduced. However, in this case, for example, when NF ₃ gas is used as a cleaning gas, it acts on the Si film. The amount of generated F radicals is reduced, and the etching rate of the Si film attached to the constituent member is reduced, resulting in a problem that the cleaning time is prolonged.
[0010]
Then, as shown in the application specification of Japanese Patent Application No. 2002-29909, the present applicant simply attaches the substrate 5 to the other electrode 4 for fixing the substrate 5 with the holding plate 6 at the time of film formation, at the time of self-cleaning. In addition to a state in which the substrate 5 is not fixed, a technique for fixing a dummy substrate made of a conductive metal such as aluminum in the same shape as the substrate 5 instead of the substrate 5 has been proposed.
This is because the distance from the holding plate 6 pressing the peripheral portion of the dummy substrate to the one electrode 3 and the distance from the surface of the dummy substrate to the one electrode 3 are substantially equal to each other, and The aim is to make the plasma of the cleaning gas uniform by making the distance between the electrodes 3 and 4 uniform.
Further, in the specification of Japanese Patent Application No. 2002-29909, the distance from the holding plate 6 to the one electrode 3 is reduced by forming the dummy substrate such that the portion other than the peripheral edge on the surface of the dummy substrate is convex. A technique has been proposed in which the distance from the surface of the dummy substrate to the one electrode 3 is the same so that the plasma of the cleaning gas is made uniform even when the supply power for plasma generation is high.
[0011]
However, particularly when the F-based gas is used as a cleaning gas and the supply power for generating the F plasma is increased (2 kw / m ² or more) and the plasma density is increased, one of the plasma generating electrodes is used. Regarding the electrode 3, F plasma tends to be strong in a region between a plurality of power supply positions 3 d that exist in each of the pair of power supply rods 3 b, 3 b, and in a central region located between the pair of power supply rods 3 b, 3 b. The plasma tends to weaken (application specification of Japanese Patent Application No. 2001-260126 according to the present application), and it has not been possible to sufficiently achieve uniform plasma.
[0012]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and a dummy substrate used for self-cleaning of a vacuum processing apparatus capable of equalizing the plasma of a cleaning gas even under a high plasma density, and a vacuum processing in which the dummy substrate is fixed. It is intended to provide a device.
[0013]
[Means for Solving the Problems]
In order to solve the above problems and achieve such an object, a dummy substrate according to the present invention includes one electrode provided in a vacuum vessel to which a predetermined source gas is supplied, and one electrode provided in the vacuum container. The other electrode provided in the vacuum vessel so as to face each other, the other electrode provided with a conductive pressing plate for pressing the peripheral portion of the substrate placed on the surface and fixing the substrate, A predetermined process such as forming a film based on the source gas on the surface of the substrate is performed by applying a high-frequency voltage between the one and the other electrodes to form a plasma of the source gas between the two electrodes. In a vacuum processing apparatus, self-cleaning for removing a film adhered to a constituent member in the vacuum container by film formation on the surface of the substrate by reacting with a plasma formed by introducing a cleaning gas into the vacuum container. When performing, a conductive dummy substrate fixed to the other electrode in place of the substrate, in a portion except for the vicinity of the peripheral edge of the surface, the upper surface located at a predetermined height from this surface And a conductive raising member attached thereto.
According to the present invention having such a configuration, since the separate raising member is attached to the surface of the dummy substrate, by appropriately setting the height of the upper surface of the raising member, The distance between the upper surface of the raising member and one of the electrodes can be greatly reduced as compared with the conventional case, and even when the supply power for plasma generation to one of the electrodes is high, the distance to the other electrode on the ground side can be reduced. The directivity is enhanced, and the distribution of the plasma of the cleaning gas formed between the electrodes can be improved and uniformized.
[0014]
At this time, the raising member may have a plurality of slits cut from the outer peripheral edge on the upper surface toward the center. With such a configuration, the upper surface of the raising member may have an in-plane surface. It is possible to suppress the occurrence of thermal buckling deformation due to the temperature distribution.
Furthermore, at this time, the raising member may be divided and attached to a plurality of parts. With such a configuration, the in-plane temperature distribution on the upper surface of the raising member and the temperature difference between the raising member and the dummy substrate are reduced. It is possible to reduce the size, and further, it is possible to avoid a portion that interferes during the transfer of the dummy substrate.
[0015]
Further, the vacuum processing apparatus according to the present invention is provided with one electrode provided in a vacuum vessel to which a predetermined source gas is supplied, and provided in the vacuum vessel so as to face the one electrode, And a second electrode provided with a conductive pressing plate for pressing the peripheral portion of the substrate mounted thereon and fixing the substrate, and applying a high-frequency voltage between the one and the other electrodes to apply both the electrodes. In a vacuum processing apparatus for performing a predetermined process such as forming a film based on the source gas on the surface of the substrate by forming a plasma of the source gas between the electrodes, the film is formed on the surface of the substrate by the film formation. When performing self-cleaning, in which a film adhered to a constituent member in a vacuum vessel is removed by reacting with plasma formed by introducing a cleaning gas into the vacuum vessel, the film is applied to the other electrode instead of the substrate. Dummy substrate of the present invention is characterized in that it is fixed.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
The vacuum processing apparatus (plasma CVD apparatus) according to the present embodiment has the same configuration as the above-described vacuum processing apparatus shown in FIGS. 5 and 6 (the same parts are described using the same reference numerals). During the self-cleaning, a conductive material such as aluminum as shown in FIGS. 1 to 4 is used instead of the rectangular plate-shaped substrate 5 made of glass containing SiO ₂ as a main component. A dummy substrate 10 made of metal is placed on the surface of the other electrode 4, and the periphery of the dummy substrate 10 is pressed toward the electrode 4 by a conductive pressing plate 6, thereby fixing the dummy substrate 10 to the electrode 4. It is like that.
[0017]
Also in such a vacuum processing apparatus, for example, an F-based gas such as NF ₃ is supplied into the vacuum vessel 1 through a plurality of holes 3 a in one electrode 3 as a cleaning gas used at the time of self-cleaning.
Then, a high frequency supplied from the high frequency power supply 2 is supplied to a plurality of power supply positions 3 d provided on the pair of power supply rods 3 b, 3 b on one electrode 3, and a high frequency voltage is applied between the electrodes 3, 4. As a result, F radicals are generated by forming F plasma of an F-based gas.
By causing the F radical to act on the Si film to be removed, generating a SiF ₄ gas, and then exhausting the gas, the Si film attached to the constituent members in the vacuum vessel 1 is removed.
[0018]
As shown in FIG. 1, the dummy substrate 10 according to the first embodiment of the present invention has a rectangular plate shape (rectangular plate shape) with one side exceeding 1 m, and has substantially the same shape as the substrate 5 on which a film is to be formed. It is formed, and the material is not limited as long as it is basically conductive and has excellent corrosion resistance to F radicals. In this embodiment, aluminum is selected. This is because the aluminum substrate is similar in physical properties such as mass and calorie to a glass substrate (substrate 5 on which a film is to be formed), and can be used with the same feeling as a glass substrate, and has good corrosion resistance to F radicals. This is because it has the feature of being. The physical properties of glass and aluminum are specific gravity = 2.5 / 2.7 and specific heat = 0.2 (kcal / kg · K) /0.21 (kcal / kg · K).
[0019]
Further, the dummy substrate 10 is formed with a plurality of slits 11 cut from each of four sides forming the outer peripheral edge toward the center in order to suppress thermal buckling deformation caused by the in-plane temperature distribution. Accordingly, the peripheral portion of the dummy substrate 10 is divided into a plurality.
Among the four sides of the dummy substrate 10, a plurality of slits 11 cut from the same side toward the center are substantially orthogonal to the side, and are disposed substantially parallel to each other at substantially equal intervals. It is formed such that the closer to the center of the side, the longer its length.
[0020]
The length of each slit 11 is about 10% or more of the substrate length (the length of the dummy substrate 10 in the length direction (cutting direction) of the slit 11) (about 100 mm or more when the substrate length exceeds 1 m). It is preferable that the interval between the substantially parallel slits 11 adjacent to each other is set in the range of 100 to 150 mm. Further, the width of each slit 11 is 1 mm or less for suppressing abnormal plasma discharge ( More preferably, it is set to 0.5 mm or less.
[0021]
Further, the dummy substrate 10 has a raising member 12 having an upper surface 13 located at a predetermined height from the surface 10a with respect to a central portion of the surface 10a excluding the vicinity of the peripheral portion pressed by the holding plate 6. Installed.
The raising member 12 has a rectangular (rectangular) upper surface 13 positioned at a height of about 5 to 25 mm from the dummy substrate 10a, and a peripheral wall intersecting an outer peripheral edge (four sides) of the upper surface 13. It is composed of a portion 14 and a flange portion 15 extending outward from the peripheral wall portion 14 and having a plurality of screw holes 16 formed therein, and is hollow.
As the material of the raising member 12, an aluminum plate is selected for the same reason as the dummy substrate 10 described above, and the thickness thereof can be about 0.1 to 1 mm, but in the present embodiment, , About 0.5 mm.
[0022]
The raising member 12 is fixed to the surface 10a of the dummy substrate 10 by screws via screw holes 16 formed in the flange portion 15.
Here, a part of the screw hole 16 formed in the flange portion 15 of the raising member 12 (for example, the screw hole 16 formed at the end of the flange portion 15) is a round hole 16a used for positioning. , Whereas the remainder is a slot 16b. This makes it possible to absorb deformation due to a temperature difference between the raising member 12 and the dummy substrate 10 by the elongated hole 16b, while keeping the positioning function of the raising member 12 with respect to the dummy substrate 10 by the round hole 16a. That's why.
[0023]
In the vacuum processing apparatus in which the dummy substrate 10 to which the above-described raising member 12 is attached is fixed by pressing the peripheral portion of the electrode 4 on the ground side with the pressing plate 6 instead of the substrate 5 on which the film is to be formed, As shown in FIG. 2, the distance L1 from the electrode 3, which is a plasma generating electrode, to the surface 10a of the dummy substrate 10 is in the range of 25 to 45 mm (the same applies to the distance from the electrode 3 to the holding plate 6). Distance L2 from electrode 3 to upper surface 13 of raising member 12 attached to dummy substrate 10 is in the range of 5 to 30 mm.
[0024]
During self-cleaning in such a vacuum processing apparatus, the distance between the upper surface 13 of the raising member 12 of the dummy substrate 10 fixed to the electrode 4 and the electrode 3 serving as the plasma generating electrode is set to be significantly small. (5 to 30 mm), the directivity to the electrode 4 on the ground side becomes strong, and the supply electrode for generating plasma to the electrode 3 is high, and even when the plasma density is high, the cleaning gas is provided between the electrodes 3 and 4. As a result, a uniform F plasma is formed by the NF ₃ gas.
Therefore, even if the substrate 5 has a large area (the electrode 4 has a large area), it is possible to uniformly clean each component without causing localization of plasma.
[0025]
Further, the electrode 4 on the ground side also serves as a heater cover, and this heater cover is required to have corrosion resistance to F radicals. By fixing the dummy substrate 10 to the electrode 4, corrosion due to F radicals is suppressed. As a result, the surface integrity of the heater cover can be maintained for a long period of time.
[0026]
Next, a description will be given of a dummy substrate 10 according to a second embodiment of the present invention.
In the dummy substrate 10 according to the second embodiment, as shown in FIG. 3, a plurality of slits 17 cut from the four sides forming the outer peripheral edge toward the center on the upper surface 13 of the raising member 12. It has been formed. Among the four sides of the upper surface 13, a plurality of slits 17 cut from the same side toward the center (excluding the slits 17 cut from the corners of the upper surface 13) are formed on this side. They are substantially orthogonal to each other, are substantially parallel to each other, and are arranged at substantially equal intervals.
In the dummy substrate 10 according to the second embodiment, in addition to the same effects as those of the above-described embodiment, the thermal buckling deformation caused by the in-plane temperature distribution generated on the upper surface 13 of the raising member 12 is suppressed. The distance between the plasma electrode 3 and the upper surface 13 of the raising member 12 can be kept constant and stable.
[0027]
Note that the length of each slit 17 is preferably about 10% or more of the substrate length (about 100 mm or more when the substrate length exceeds 1 m), and between the substantially parallel slits 11 adjacent to each other. The interval is preferably set in the range of 100 to 150 mm, and the width of each slit 11 is preferably set to 1 mm or less (more preferably, 0.5 mm or less) to suppress abnormal plasma discharge. .
[0028]
Next, a description will be given of a dummy substrate 10 according to a third embodiment of the present invention.
In the dummy substrate 10 according to the third embodiment, the raising member 12 mounted on the upper surface 13 is divided and mounted on the upper surface 13, that is, the raising member 12 mounted on the upper surface 13 includes a plurality of raising members 12A. , 12B, and 12C. In addition, the spacing between adjacent ones of the plurality of raised members 12A, 12B, 12C may be too large to hinder the uniformity of the F plasma. Is set to 10% or less.
In the dummy substrate 10 according to the third embodiment, in addition to the same effects as those of the above-described embodiment, the in-plane temperature distribution on the upper surface 13 of the raising member 12 and the temperature difference between the raising member 12 and the dummy substrate 10 are obtained. Can be reduced, and the raising member 12 can be attached so as to avoid a portion where interference occurs with other members when the dummy substrate 10 is carried.
[0029]
In the above embodiment, a plasma CVD apparatus is described as a vacuum processing apparatus. However, a vacuum processing apparatus that performs self-cleaning (cleaning using plasma of a cleaning gas) is not limited thereto. For example, the present invention can be applied to a dry etching apparatus.
In addition, as the dummy substrate 10 and the raising member 12, other materials having F radical corrosion resistance, such as an Inconel material and a Ni-plated steel material, capable of securing sufficient strength at a use environment temperature are used. can do.
[0030]
【The invention's effect】
According to the present invention, since a separate raising member is attached to the surface of the dummy substrate, by appropriately setting the height of the upper surface of the raising member, the upper surface of the raising member and one of the upper surface of the raising member are appropriately set. Since the distance from the electrode can be greatly reduced as compared with the conventional case, the directivity to the other electrode, which is on the ground side, becomes stronger even when the supply power for plasma generation to one electrode is high. Thus, the distribution of the plasma of the cleaning gas formed between the two electrodes can be improved and uniformized, and uneven cleaning can be suppressed.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a dummy substrate according to a first embodiment of the present invention.
FIG. 2 is a schematic explanatory view in which main parts of a vacuum processing apparatus to which the dummy base shown in FIG. 1 is mounted are extracted.
FIG. 3 is a perspective view illustrating a dummy substrate according to a second embodiment of the present invention.
FIG. 4 is a plan view illustrating a dummy substrate according to a third embodiment of the present invention.
FIG. 5 is a schematic explanatory view showing a general vacuum processing apparatus.
6 is a perspective view showing a ladder type gas pipe electrode used in the vacuum processing apparatus shown in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Vacuum container 2 High frequency power supply 3 One electrode 3a Hole 3b Power supply rod 3c Pipe member 4 The other electrode 5 Substrate 6 Holding plate 7 Heater 10 Dummy substrate 10a Surface 11 Slits 12A, 12B, 12C Raising member 13 Upper surface 14 Peripheral wall portion 15 Flange Parts 16, 16a, 16b Screw holes

Claims (4)

One electrode provided in a vacuum container to which a predetermined source gas is supplied, and a peripheral portion of a substrate provided in the vacuum container so as to face the one electrode and mounted on the surface. And a second electrode provided with a conductive pressing plate for fixing the substrate by applying a high-frequency voltage between one and the other electrodes to form a plasma of the source gas between the two electrodes. By doing so, in a vacuum processing apparatus that performs a predetermined process such as forming a film based on the source gas on the surface of the substrate,
When performing self-cleaning for removing a film adhered to a component member in the vacuum container by film formation on the surface of the substrate and reacting with a plasma formed by introducing a cleaning gas into the vacuum container, A conductive dummy substrate fixed to the other electrode instead of the substrate,
A dummy substrate, wherein a conductive raising member having an upper surface positioned at a predetermined height from the surface is attached to a portion of the surface other than the vicinity of a peripheral portion. The dummy substrate according to claim 1,
A dummy substrate, wherein the raising member has a plurality of slits cut from an outer peripheral edge on an upper surface thereof toward a center portion. The dummy substrate according to claim 1 or 2,
The dummy substrate, wherein the raising member is divided and attached to a plurality of parts. One electrode provided in a vacuum container to which a predetermined source gas is supplied, and a peripheral portion of a substrate provided in the vacuum container so as to face the one electrode and mounted on the surface. And a second electrode provided with a conductive pressing plate for fixing the substrate by applying a high-frequency voltage between one and the other electrodes to form a plasma of the source gas between the two electrodes. By doing so, in a vacuum processing apparatus that performs a predetermined process such as forming a film based on the source gas on the surface of the substrate,
When performing self-cleaning for removing a film adhered to a component member in the vacuum container by film formation on the surface of the substrate and reacting with a plasma formed by introducing a cleaning gas into the vacuum container, 4. The vacuum processing apparatus according to claim 1, wherein the dummy substrate according to claim 1 is fixed to the other electrode instead of the substrate.

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