JP2004087981A - Etching device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an etching device and a method which are capable of forming uniform irregularities on the surface of a board with high tact without arranging and aligning a plate member on the board. <P>SOLUTION: The etching device is equipped with an anode-side electrode 8 and a cathode-side electrode 3 which are confronted with each other, the board 2 is placed on the cathode-side electrode to roughen its surface by etching, and the plate member 7 where a large number of openings 11 are provided is installed on one side of the anode-side electrode 8. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an etching apparatus and an etching method, and more particularly to an etching apparatus and an etching method that can be suitably used for roughening the surface of a silicon substrate or the like used for a solar cell or the like.
[0002]
2. Description of the Related Art
A solar cell converts incident light energy into electric energy. Major solar cells are classified into crystalline, amorphous, and compound solar cells according to the type of materials used. Most of these are crystalline silicon solar cells currently on the market. The crystalline silicon solar cells are further classified into a single crystal type and a polycrystalline type. Single-crystal silicon solar cells have the advantage that the efficiency of the substrate can be easily increased due to the good quality of the substrate, but have the disadvantage that the cost of manufacturing the substrate is high. On the other hand, a polycrystalline silicon solar cell has a disadvantage that it is difficult to increase the efficiency due to poor substrate quality, but has an advantage that it can be manufactured at low cost. Recently, a conversion efficiency of about 18% has been achieved at the research level due to the improvement in the quality of polycrystalline silicon substrates and advances in cell technology.
[0003]
On the other hand, polycrystalline silicon solar cells at the mass production level have been distributed on the market because of their low cost, but in recent years the demand for them has increased further due to environmental issues being addressed. Was required.
[0004]
In such a solar cell, various attempts have been made in the past to improve the conversion efficiency into electric energy. One of the techniques is a technique for reducing the reflection of light incident on a substrate. By reducing the reflection of light on the surface, the efficiency of conversion to electric energy can be increased.
[0005]
When a solar cell element is formed using a silicon substrate, when the surface of the substrate is etched with an aqueous alkali solution such as sodium hydroxide, fine irregularities are formed on the surface of the substrate, and reflection can be reduced to some extent. When a single crystal silicon substrate having a (100) plane orientation is used, a pyramid structure called a texture structure can be uniformly formed on the surface of the substrate by such a method. Since the orientation depends on the orientation, when a solar cell element is formed from a polycrystalline silicon substrate, the pyramid structure cannot be formed uniformly, and therefore, there is a problem that the overall reflectance cannot be reduced effectively.
[0006]
In order to solve such a problem, it has been proposed to form fine protrusions on the surface of a substrate by a reactive ion etching method when a solar cell element is formed of polycrystalline silicon. (See, for example, JP-B-60-27195, JP-A-5-75152 and JP-A-9-102625). In other words, it is intended to form fine irregularities uniformly without being affected by the plane orientation of irregular crystals in polycrystalline silicon, and to reduce the reflectance more effectively even in a solar cell element using polycrystalline silicon. It is.
[0007]
However, the conditions for forming the irregularities as described above are delicate, and vary depending on the structure of the apparatus, so that setting the conditions is often very difficult. When unevenness cannot be formed uniformly, incident light cannot be effectively taken into the solar cell, and the photoelectric conversion efficiency of the solar cell does not improve. Since the value of each solar cell is determined by its power generation efficiency, the cost must be reduced by improving the conversion efficiency of the solar cell.
[0008]
The apparatus used in the reactive ion etching method is generally of a parallel plate electrode type, in which an RF voltage is applied to the side of the electrode on which the substrate is installed, and the other side and the inner side wall are grounded. Connecting. The inside of the chamber is evacuated and an etching gas is introduced to etch the substrate to be etched while keeping the pressure constant. After the etching is completed, the inside of the chamber is returned to the atmospheric pressure.
[0009]
By taking such a procedure, the reactive ion etching apparatus has a long waiting time for evacuation and air leakage. In addition, reactive ion etching equipment is often used for precision small semiconductor devices such as LSIs. However, when used for solar cells, the area of the solar cells themselves is large, so the number of processed cells per operation is small, and There was a problem that cost was high. Therefore, when a reactive ion etching apparatus is used in the manufacturing process of a solar cell, it is important how to increase the number of processed sheets per operation with high tact.
[0010]
As one of the methods for improving the tact time, there is a method disclosed in Japanese Patent Application No. 2001-298671. In this method, etching is performed while attaching an etching residue to the surface of a silicon substrate to form irregularities and roughen the surface. Then, the etching residue is removed. Next, the substrate to be etched is covered with a plate member having an opening formed therein and etched. According to this method, the formation speed of the unevenness is increased, and at the same time, the uniformity of the unevenness in the batch is improved, and the number of processed sheets per one processing can be increased.
[0011]
According to this method, a substrate to be etched is placed on a tray, covered with a plate member, transported onto an electrode in a chamber, evacuated and etched, and then the chamber is returned to the atmosphere and the tray is unloaded. This is the process of removing the plate member and collecting the substrate.
[0012]
However, in this method, since the plate member which becomes a resistance at the time of evacuation is returned to the atmosphere each time and then the evacuation is performed, the evacuation speed in the chamber is compared with the evacuation speed when the plate member is not placed. Is reduced. Even if a preliminary chamber or the like is provided adjacent to the chamber and continuous batch processing is performed, the above-described process does not change, and a plurality of plate members will repeat air and vacuum, and the evacuation speed when the plate members are not mounted and In comparison, the evacuation speed in the chamber is reduced.
[0013]
It is also conceivable to transport the substrate and the tray from between the supports by supporting the four points at the ends of the plate member with a support or the like. However, the plate member is separated from the substrate only by 5 to 30 mm. Therefore, it is substantially impossible to transport the substrate and the tray during this time. In addition, in the case of an etching apparatus having a large etching area, in a method of supporting the four points at the ends of the plate member, the plate member bends due to its own weight, and uneven etching occurs due to a difference in distance between the substrate and the plate member. There is also a problem.
[0014]
The present invention has been made in view of such problems of the related art, and an object of the present invention is to provide an etching apparatus and an etching method for forming uniform irregularities on a surface of a substrate with high tact.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, an etching apparatus according to claim 1, wherein a substrate is placed on a cathode electrode provided opposite to an anode electrode to roughen the surface of the substrate. A plate member having a large number of openings formed on the anode side is provided.
[0016]
In the above etching apparatus, it is preferable that the cathode side electrode and the anode side electrode have a parallel plate structure.
[0017]
In the etching apparatus, it is preferable that a protruding wall is provided on the cathode side of the plate member or on a surface on which the substrate is mounted.
[0018]
Further, in the above etching apparatus, it is desirable to provide a protruding wall on the side of the cathode on the periphery of the plate member.
[0019]
In the above etching apparatus, it is desirable that at least one of the opposed electrodes is movable.
[0020]
In the above etching apparatus, the plate member is desirably movable.
[0021]
Further, in the above etching apparatus, it is desirable to perform chamfering on an end face of the opening of the plate member.
[0022]
In the above etching apparatus, it is preferable that the etching apparatus is a reactive ion etching apparatus.
[0023]
In the etching method according to claim 10, in the etching method in which a substrate is placed on a cathode electrode provided to face an anode electrode and the surface of the substrate is roughened, an opening is provided on the anode side. A large number of plate members are attached and etched.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1 and 2 are views showing an embodiment of an etching apparatus according to the present invention, wherein 1 is a mass flow controller, 2 is a silicon substrate, 3 is an RF electrode (cathode side electrode), 4 is a pressure regulator, and 5 is A vacuum pump 6 is an RF power supply.
[0025]
An etching gas and an etching residue generation gas are introduced into the chamber 14 from the mass flow controller 1 and a plasma is generated by introducing RF power from the RF electrode 3 to excite and activate ions and radicals to activate the RF electrode 3. Etching is performed by acting on the surface of a substrate 2 made of, for example, silicon or the like provided on the top.
[0026]
In the apparatus shown in FIG. 2, the RF electrode 3 is installed in the apparatus and the surface of one silicon substrate 2 is etched, but in the apparatus shown in FIG. The surfaces of the silicon substrates 2 are simultaneously etched.
[0027]
Among the generated active species, a method in which the effect of the ions acting on the etching is increased is generally called a reactive ion etching method. Although there is a similar method such as plasma etching, the principle of plasma generation is basically the same, and the distribution of types of active species acting on the substrate 1 is changed to a different distribution depending on a chamber structure, an electrode structure, or a generation frequency. I just let it. Therefore, the present invention is effective not only in the reactive ion etching apparatus but also in all dry etching apparatuses such as a plasma etching method.
[0028]
The etching apparatus of the present invention will be described in detail with reference to FIGS. In FIG. 3, reference numeral 2 denotes a silicon substrate, 3 denotes an RF electrode, 6 denotes an RF power source, 7 denotes a plate member, 8 denotes a chamber wall, 9 denotes a mounting member, 10 denotes a tray, 11 denotes an opening, and 12 denotes an insulator.
[0029]
A plate member 7 in which a large number of openings 11 are formed is mounted via a mounting member 9 to a chamber wall 8 which is connected to the ground and serves as an anode electrode in the chamber 14. On the side of the cathode electrode 7, a tray 10 is placed on the RF electrode 3, and a silicon substrate 2 to be etched is placed thereon. By introducing RF power from the RF electrode 3, a plasma is generated to excite and activate ions and radicals, and the plasma is applied to the surface of the silicon substrate 2 provided on the RF electrode 3 to perform etching. At this time, if the mounting position of the plate member 7 is on the side of the anode electrode 8 which can be separated from the side of the cathode electrode 3 on which the substrate 2 is mounted, as shown in FIG. Alternatively, as shown in FIG. 4, it may be mounted on the side wall in the chamber 14. In addition, as shown in FIG. 5, by fixing the plate member 7 not only at the peripheral portion but also at the central portion by the mounting member 9, it is possible to prevent the plate member 7 from bending due to its own weight.
[0030]
It is desirable that the chamber wall 8 and the plate member 7 are insulated. As a result, the plate member 7 has no effect as an electrode, and the state of plasma generation does not depend on the mounting method and position of the plate member 7 on the chamber wall 8. As a method of insulating the chamber wall 8 and the plate member 7, the plate member 7 or the mounting member 9 may be made of an insulating material, or an insulating material may be interposed between the plate member 7 and the chamber wall 8.
[0031]
When the etching apparatus is of a batch type, it is desirable that the cathode 3 and the anode 8 have a parallel plate structure. This is to avoid the occurrence of etching unevenness due to the difference in the distance between the substrate 2 and the counter electrode 8.
[0032]
Further, as shown in FIG. 6, by providing the projecting wall 13 on the cathode 3 side of the plate member 7, a residue serving as an etching mask can be effectively confined between the substrate 2 and the plate member 7, and unevenness can be obtained. Formation can be promoted. This effect is particularly effective when the protruding wall 13 is provided on the periphery of the plate member 7.
[0033]
Further, as shown in FIG. 7, the protruding wall 13 can be provided on the anode electrode 8 side of the surface on which the substrate 2 is mounted. The projecting wall 13 may be provided at a position where it comes into contact with the tray 10 or the plate member 7 during the etching process, or may be provided at a position where it does not come into contact. In the case where it is provided at a contact position, at least one of the tray 10, the protruding wall 13, the plate member 7, or the mounting member 9, which intervenes the cathode electrode 3 and the chamber wall 8 so as not to conduct, must be formed of an insulating material. .
[0034]
It is desirable that at least one of the opposing electrodes 3 and 8 is movable in a direction away from each other. By doing so, even if the plate member 7 is arranged at a distance of 5 to 30 mm from the substrate 2 as in the past, the distance between the electrodes 3 and 8 is increased when the substrate 2 and the tray 10 are transported. The space between the plate 2 and the plate member 7 can be secured, and the substrate 2 and the tray 10 can be transported.
[0035]
FIG. 8 is a diagram showing an example in which the anode 8 is fixed and the cathode 3 is moved.
[0036]
Further, as shown in FIG. 9, if the plate member 7 is vertically movable in the chamber 13, the substrate 2 and the tray 10 can be transported from the side of the chamber 13, and particularly, continuous batch processing is performed. This is advantageous in the case of an etching apparatus.
[0037]
It is desirable to chamfer the corners of the opposite end faces of the opening 11 of the plate member 7. Thereby, abnormal discharge in the opening 11 can be avoided.
[0038]
The plate member 7 may be made of either a metal material or a glass material. A metal member made of aluminum or the like is preferable in terms of easy processing of the plate member 7, but a stainless steel material or the like is not suitable because it is corroded when exposed to a gas used for silicon etching.
[0039]
It is desirable that the etching is performed while maintaining the distance between the plate member 7 and the silicon substrate 2 at 5 to 30 mm. By doing so, the silicon compound generated at the time of etching can be trapped between the silicon substrate 2 and the plate member 7, and a residue containing silicon as a main component is easily generated on the silicon substrate 2; And the formation of unevenness can be promoted at the same time. When the distance between the plate member 7 and the silicon substrate 2 is 5 mm or less, when the opening 11 of the plate member 7 forms irregularities, it is transferred as a pattern on the surface of the silicon substrate 2 and becomes uneven. On the other hand, if it is 30 mm or more, the formation of the residue is delayed, and the effect of promoting the formation of unevenness is reduced.
[0040]
The pattern shape of the opening 11 of the plate member 7 is not particularly limited. For example, a pattern in which circular openings are arranged in a matrix may be used, or a staggered dot pattern may be used. Also, a pattern such as a slit can be formed. However, if there is a portion having a large area that is not open, unevenness occurs in the lower portion due to a difference in the shape of the unevenness 2 from the lower portion of the opening 11. The ratio of the opening 11 of the plate member 7 to the entire area can be selected according to the etching state of the substrate to be etched.
[0041]
In the above example, a bulk silicon solar cell was described as an example of a substrate to be etched. However, substrates such as a substrate type thin film silicon solar cell, a superstrate type solar cell, an amorphous silicon solar cell, and a thin film solar cell using a compound. Widely applicable to Further, it can be applied to a substrate such as a multilayer (tandem) type thin film solar cell. Furthermore, it is not limited to solar cells.
[0042]
【The invention's effect】
As described above, according to the etching apparatus of the present invention, in the etching apparatus in which the substrate is placed on the cathode electrode provided to face the anode electrode and the surface of the substrate is roughened, Since a plate member having a large number of openings is provided on the anode side, it is not necessary to align the plate members and arrange them on the substrate, and uniform unevenness can be formed on the substrate surface with a high tact. .
[0043]
Further, in the etching method according to the tenth aspect, in the etching method in which a substrate is placed on a cathode electrode provided opposite to an anode electrode and the surface of the substrate is roughened, an opening is formed on the anode side. Since the plate member having a large number of parts is attached and etched, it is not necessary to position the plate member one by one and dispose it on the substrate, and uniform irregularities can be formed on the substrate surface with high tact.
[Brief description of the drawings]
FIG. 1 is a diagram showing a structure of an etching apparatus according to the present invention.
FIG. 2 is a diagram showing another structure of the etching apparatus according to the present invention.
FIG. 3 is a diagram showing a structural example of an etching apparatus according to the present invention.
FIG. 4 is a diagram showing another example of the structure of the etching apparatus according to the present invention.
FIG. 5 is a diagram showing another example of the structure of the etching apparatus according to the present invention.
FIG. 6 is a diagram showing another example of the structure of the etching apparatus according to the present invention.
FIG. 7 is a diagram showing another example of the structure of the etching apparatus according to the present invention.
FIG. 8 is a view showing another example of the structure of the etching apparatus according to the present invention.
FIG. 9 is a diagram showing another example of the structure of the etching apparatus according to the present invention.
FIG. 10 is a diagram showing a structural example of a conventional etching apparatus.
[Explanation of symbols]
Reference Signs List 1: mass flow controller, 2: silicon substrate, 3: RF electrode (cathode), 4: pressure regulator, 5: vacuum pump, 6: RF power supply, 7; plate member, 8: chamber wall (anode), 9; Member, 10; tray, 11; opening, 12; insulator, 13; projecting wall, 14;

Claims (9)

In an etching apparatus for mounting a substrate on a cathode electrode provided opposite to an anode electrode to roughen the surface of the substrate, a plate member having a large number of openings formed on the anode side was provided. An etching apparatus characterized by the above-mentioned. 2. The etching apparatus according to claim 1, wherein the cathode side electrode and the anode side electrode have a parallel plate structure. The etching apparatus according to claim 1, wherein a protruding wall is provided on the cathode side of the plate member or on a surface on which the substrate is mounted. The etching apparatus according to claim 1, wherein a protruding wall is provided on a side of the plate member on the side of the cathode. The etching apparatus according to claim 1, wherein at least one of the opposed electrodes is movable. The etching apparatus according to claim 1, wherein the plate member is movable. The etching apparatus according to any one of claims 1 to 6, wherein a chamfering process is performed on an end surface of the opening of the plate member. The etching apparatus according to any one of claims 1 to 7, wherein the etching apparatus is a reactive ion etching apparatus. In an etching method of placing a substrate on a cathode electrode provided opposite to an anode electrode and roughening the surface of the substrate, a plate member having a large number of openings formed on the anode side is attached. An etching method characterized by performing etching.

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