JP2006179720A - Plasma treatment device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma treatment device directly and uniformly forming a recessed groove for a formation formed by a patterning on the surface of a substrate used for a solar cell with high efficiency. <P>SOLUTION: The plasma treatment device is composed of a discharge electrode (1) for placing an article to be treated, a counter discharge electrode (2) oppositely arranged to the discharge electrode (1), and a solid-state dielectric (3) mounted on a surface on the discharge electrode (1) side for placing the article to be treated in the counter discharge electrode (2). The plasma treatment device is further composed of an atmospheric-gas supply pipe (5a) for supplying atmospheric gas to a space (4) between the solid-state dielectric (3) and the discharge electrode (1) for placing the article to be worked with an atmospheric gas. In such a plasma treatment device, a project (8) for a discharge or a recess (7) for the discharge is formed to an opposed surface to the discharge electrode (1) for placing the article to be treated in the solid-state dielectric (3). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a plasma processing apparatus that generates plasma by discharge from a solid dielectric and directly performs surface processing such as deposit or etching of a workpiece, particularly a semiconductor silicon wafer or a solar cell substrate.

  Solar cells convert incident light energy into electrical energy, and are classified into crystalline, amorphous, and compound types depending on the materials used. Currently, the crystalline silicon with high conversion efficiency is in the market. It is a solar cell. This crystalline silicon solar cell is further classified into a single crystal type and a polycrystalline type. In this solar cell, a large number of cells (110) are cascade-connected in one insulating substrate (100) or module so that a high voltage can be taken out. FIG. 10 is a cross-sectional view of the power module manufactured by the above method.

Each cell (110) formed on one insulating substrate (100) is connected in series with an adjacent cell (110) through a transparent electrode (109) and a back electrode (111) by appropriate patterning, and is high. Voltage can be obtained. As shown in FIGS. 8 to 9, the metal mask method, the photolithography method, or the transparent electrode is used for patterning by resin printing → etching → resin peeling → mask alignment for solar cell element layer formation → mask alignment for back electrode formation There is a patterning method using a laser of a deposition layer → a patterning using a laser of a solar cell element layer → a laser of a back electrode deposition layer (Non-Patent Document 1).
Photovoltaic cells and their applications [Revised Edition] Publishing company Power Co., Ltd. Author Kokunori Kuwano Shoichi Nakano Ikuo Kishi Mizuno Onishi April 25, 1994

  At present, solar cells are moving from research level to mass production level, and in recent years, they are attracting worldwide attention from the viewpoint of protecting the global environment. Along with the demand for efficiency, lower costs have become more demanding. In such a solar cell, the above-described patterning methods are all inferior in production efficiency and costly.

    The present invention has been made in view of such problems of the prior art, and is for a buried electrode formed by patterning on the surface of a semiconductor substrate, particularly a substrate used for a semiconductor device (especially a diode) or a solar cell. It is an object of the present invention to provide a plasma processing apparatus capable of uniformly forming a high-efficiency deposit or a concave groove for cell formation.

  In order to achieve the above object, a plasma processing apparatus according to claim 1 includes: a discharge electrode for placing a workpiece (1) and a counter discharge electrode (2) disposed opposite to the discharge electrode (1). ), A solid dielectric (3) provided on the surface of the counter discharge electrode (2) on the workpiece mounting discharge electrode side, and a solid dielectric (3) and a workpiece mounting discharge electrode (1) ) Is a plasma processing apparatus configured with an atmosphere gas supply pipe (5a) for supplying an atmosphere gas to the space (4) between the opposing surfaces (2a) of the solid dielectric (3) with respect to the counter discharge electrode (2) ) Is provided with a discharge convex portion (8) or a discharge concave portion (7).

  In this processing apparatus, since the discharge convex portion (8) or the discharge concave portion (7) is formed on the opposite surface of the solid dielectric (3), the discharge convex portion (8) and the workpiece (10) or plasma due to glow discharge is generated between the ceiling surface (7a) of the discharge recess (7) and the workpiece (10), and the discharge protrusion (8) or discharge discharge A predetermined hole or groove shape is directly formed over the entire surface of the workpiece (10) or in a necessary portion in accordance with the recess (7). The workpiece (10) is, for example, a silicon wafer or glass.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows the principle of the apparatus of the present invention. A discharge electrode (1) for placing a work piece on a disc or a square plate, and the discharge electrode (1) directly above the discharge electrode (1) for placing a work piece. A counter discharge electrode (2) disposed opposite to 1), and a solid dielectric (3) provided on a surface of the counter discharge electrode (2) facing the workpiece mounting discharge electrode (1), The atmosphere gas supply mechanism (5) for supplying the atmosphere gas to the space (4) between the solid dielectric (3) and the discharge electrode (1) for placing the work piece, and the CCD sensor (22) are roughly configured. And is housed in a sealed chamber (11).

  In FIG. 1, the discharge electrode (1) for placing a workpiece is placed on a movable table (12) installed at the bottom of a sealed chamber (11), and is rotated in the vertical and horizontal directions and in the vertical direction (XY-θ). It is driven by the drive device (13) in the -Z direction). The drive device (13) is a known mechanism, such as an XY stage using a stepping motor drive mechanism, a split rotation mechanism using a stepping motor drive installed thereon, and a cylinder thereon. It consists of a lifting mechanism. The workpiece mounting discharge electrode (1) can fix the workpiece (10) placed thereon, for example, by vacuum chucking or electrostatic chucking.

  The drive device (13) is configured to be subjected to vertical, horizontal, rotational and vertical position control or position control and speed control by a driver (14) and a controller (15). The bottom of the sealed chamber (11) and the moving table (12) are connected by a sealing bellows (16) that expands and contracts with the movement of the moving table (12). Further, the discharge electrode (1) for placing the workpiece is grounded via the current sensor (17).

  On the other hand, the counter discharge electrode (2) is suspended from the ceiling portion of the sealed chamber (11), and is attached to an elevating mechanism (18) used at the time of electrode replacement, and the lower surface (2a) of the counter discharge electrode (2) ( Solid dielectric (3) larger than the counter discharge electrode (2) can be attached to and detached from the discharge electrode (1) facing the work piece so as to cover the entire lower surface (2a) of the counter discharge electrode (2). is set up. Further, the counter discharge electrode (2) includes a water cooling pipe (21) for cooling the counter discharge electrode (2), and a work electrode mounting discharge electrode (1) through the solid dielectric (3). A CCD sensor (22) for positioning by looking at the alignment mark of the workpiece (10) and a high voltage power supply device (23) are installed. The CCD sensor (22) has an amplifier (24) for the CCD sensor. And CRT (25) are connected. The elevating mechanism (18) is a cylinder mechanism, for example, and is movable in the vertical direction.

  As the discharge electrodes (1) and (2), for example, a single metal such as copper or aluminum, an alloy such as stainless steel or brass, a silicon conductor material or the like is used, and the structure thereof is a parallel plate as shown in FIG. Not limited to the mold, it is possible to use each structure of a cylindrical opposed flat plate type, a sphere opposed flat plate type, a hyperboloid opposed flat plate type, a coaxial cylindrical type, and a cylindrical opposed cylindrical type. The workpiece-mounting discharge electrode (1) (flat plate electrode) and the solid dielectric (3) are arranged so as to face each other with a predetermined distance (S1) (S2) therebetween. A plasma generation space (4) is formed between the workpiece mounting discharge electrode (1) and the solid dielectric (3).

  The interval (S1) (S2) between the two is as follows. As shown in FIG. 2, the distance (S1) between the upper surface of the workpiece (10) placed on the workpiece placement discharge electrode (1) and the opposite lower surface of the solid dielectric (3) is 0.05. About 0.5 mm, and usually around 0.1 mm. The groove width (W) is 50 μm or more, usually 50 to 100 μm, and the groove height (H) is 2 to 4 mm. The reason why such a numerical value is selected is that atmospheric gas (etching gas or deposit gas) flows in the discharge recess (7), and the upper surface of the workpiece (10) and the lower surface of the solid dielectric (3) are opposed to each other. This is to prevent atmospheric gas from flowing between them. Therefore, when the discharge recess (7) is a groove, the atmospheric gas flows along the groove. However, in the case of a hole, the atmospheric gas flows from the ceiling of the hole, which is not shown. There is a need.

  On the other hand, the upper surface of the workpiece (10) placed on the workpiece placement discharge electrode (1) and the discharge convex portion (8) of the solid dielectric (3) are opposed to each other as shown in FIG. The distance (S2) from the lower surface (8a) is about 1 to 2 mm, usually around 1 mm. The width of the discharge projection (8) is not particularly limited. The height of the discharge convex portion (8) is not particularly limited, but a value of 2 to 4 mm is selected so that plasma discharge is preferentially generated from the opposite lower surface (8a) of the discharge convex portion (8). It is. Note that the atmospheric gas also flows between the discharge convex portions (8), but the ceiling surface (7a) between the discharge convex portions (8) is the workpiece (10) from the lower surface facing the discharge convex portions. Therefore, a preferential plasma discharge is generated from the discharge projection (8). As described above, in either case of FIGS. 2 and 3, the atmospheric gas is allowed to flow through the plasma discharge generation region.

  The solid dielectric (3) is made of a material having a high dielectric constant (generally, an oxide) such as quartz glass, for example, and when attached to the counter discharge electrode (2), its lower surface ( A discharge concave portion (7) or a discharge convex portion (8) as shown in FIG. 2 or FIG. 3 is formed on the workpiece mounting discharge electrode (1). The interval between the discharge concave portions (7) or the discharge convex portions (8) is formed in accordance with a site necessary for the workpiece (10). In the case of a solar cell, it is formed in accordance with a patterning groove or a buried electrode groove constituting a cell. The cross-sectional shape of the discharge concave portion (7) or the discharge convex portion (8) is rectangular, but of course, it is not limited to this, and the optimal cross-sectional shape is adopted for the patterning shape formed on the workpiece (10). Is done. Further, the discharge concave portion (7) or the discharge convex portion (8) may be an elongated straight line or a curved line, a straight or curved groove shape, a straight or curved protrusion shape, or a simple hole shape or a cylindrical shape. Good. In short, the optimum cross-sectional shape is adopted as the patterning shape formed on the workpiece (10).

  It should be noted that the solid dielectric (3) is not limited to the one installed on the counter discharge electrode (2) as shown in the figure, and is installed on both the opposing surfaces of the two discharge electrodes (1) and (2). Also good. However, the discharge recess (7) or the discharge protrusion (8) is limited to the solid dielectric (3) attached to the counter discharge electrode (2). The solid dielectric (3) is placed so as to be in close contact with the discharge electrode (2) by vacuum adsorption, and the exposed portion of the opposite discharge electrode (1) is covered so as to cover the opposite surface of the discharge electrode (2). Prevents plasma transfer to

  The atmospheric gas supply mechanism (5) is attached to the elevating mechanism (18) and elevates together with the counter discharge electrode (2). The atmosphere gas supply / exhaust mechanism (5) consists of an atmosphere gas supply pipe (5a) opened in the plasma generation space (4) between the solid dielectric (3) and the discharge electrode (1) for placing the workpiece. It consists of an atmosphere gas exhaust pipe (5b) and a partition wall (5c) surrounding the plasma generation space (4) between the two (5a) and (5b). Is provided with a seal member (6), which is in close contact with the lower surface of the solid dielectric (3) and the upper surface of the discharge electrode (1) for placing the workpiece.

  Therefore, both upper and lower surfaces surrounded by both (5a) and (5b) and the front and rear partition walls (5c) and (5c) are opened. The workpiece (10) enters the lower surface opening (5d), and the solid dielectric (3) enters the upper surface opening (5e), and the atmosphere gas supply / exhaust piping (5a ) (5b) are in close contact with the solid dielectric (3) and the workpiece placement discharge electrode (1) to form a plasma generation space (4). (5a1) is the air supply port of the atmospheric gas supply pipe (5a), (5a2) is the air supply buffer of the atmospheric gas supply pipe (5a), (5b1) is the exhaust port of the atmospheric gas exhaust pipe (5b), ( 5b2) is an exhaust buffer of the atmospheric gas exhaust pipe (5b), which reduces changes in supply air and exhaust pressure (in other words, pressure hunting).

  The solar cell substrate which is the workpiece (10) of this example is a single crystal or polycrystalline circular or rectangular silicon substrate. This substrate may be either p-type or n-type.

  The closed chamber (11) accommodates the apparatus of the present invention, and is provided with an inert gas supply pipe (28a), an inert gas exhaust pipe (28b), and an open / close door (29) for taking in and out the workpiece (10). It has been.

  Then, the workpiece (10) is placed on the workpiece placement discharge electrode (1) from the opening / closing door (29) by a transfer means (not shown) such as a robot hand, and then After the inside of the sealed chamber (11) is evacuated, the valve (31) of the inert gas supply pipe (28a) is opened, filled with inert gas, and the inside of the sealed chamber (11) is at a predetermined pressure (usually normal pressure). Inert atmosphere. Usually, He is used as an inert atmosphere.

  Subsequently, the CCD sensor (22) is operated, and the workpiece to the solid dielectric (3) with reference to the alignment mark of the workpiece (10) on the discharge electrode (1) for placing the workpiece The moving table (12) is moved by the driving device (13) so that the workpiece (10) on the mounting discharge electrode (1) is at a predetermined position. When the position of the workpiece (10) is fixed, the moving table (12) is stopped, and in this state, the carrier gas and the processing gas (etching gas in the case of etching, etching gas from the atmosphere gas supply pipe (5a) Is supplied to the plasma generation space (4) and simultaneously discharged from the atmospheric gas exhaust pipe (5b) to discharge the entire plasma generation space (4) (more precisely, the discharge recess ( In the case of 7), it is covered with the mixed gas flowing in the discharge concave portion (7), and in the case of the discharge convex portion (8), between the discharge convex portion (8) and the workpiece (10).

  In this state, the high-voltage power supply device (23) is operated and a high-voltage pulse as shown in FIG. 4 ([a] is a one-way high-voltage pulse application and [b] is a two-way high-voltage pulse application. In the latter case, the negative charge accumulated in the counter discharge electrode (2) during discharge can be neutralized with a pulse of reverse polarity to generate stable glow discharge plasma). Applied to the electrodes (1) and (2), a stable glow discharge plasma is generated between the solid dielectric (3) and the work piece (10), and the discharge portion of the work piece (10) is generated by the mixed gas. Etch or deposit directly. The state of generation of the glow discharge plasma is as described above. When the discharge concave portion (7) is formed in the solid dielectric (3) as shown in FIG. 2, the discharge ceiling surface of the discharge concave portion (7) ( Glow discharge plasma is generated between 7a) and the portion of the workpiece (10) facing the discharge ceiling surface (7a). (Since the mixed gas does not flow in the narrow gap (S1) between the opposing lower surface of the solid dielectric (3) and the workpiece (10), no etching or depositing is performed.)

  Further, as shown in FIG. 3, when the discharge convex portion (8) is formed on the solid dielectric (3) as shown in FIG. 3, the lower end surface (8a) of the discharge convex portion (8) and the workpiece Glow discharge plasma is generated between the portion facing the lower end surface (8a) of (10).

  When a predetermined amount of surface treatment (etching or deposit) is completed, the supply of the mixed gas and the energization between the discharge electrodes (1) and (2) are stopped, and the inside of the sealed chamber (11) is purged with a purge gas such as nitrogen, The open / close door (29) is opened, and the workpiece (10) having been subjected to the surface processing is taken out by a conveying means such as a robot arm.

  The gas used in the treatment in the present invention is not particularly limited as long as it is a gas that generates glow discharge plasma by applying an electric field, and various gases can be used depending on the purpose of the treatment.

  The present invention is an epoch-making method for changing the conventional patterning method, greatly contributes to low-cost and mass production of solar cell substrates, and greatly contributes to improvement of the global environment.

Schematic structure explanatory diagram of the present invention Sectional view of the first embodiment of the solid dielectric used in the present invention Sectional view of the second embodiment of the solid dielectric used in the present invention Schematic structure around the discharge electrode for placing a workpiece of the present invention Schematic perspective view of the atmospheric gas supply / discharge mechanism of the present invention Principle diagram of solar cell Rear perspective view Conventional patterning flow diagram Flow chart of other conventional patterning Cross section of a general power module

Explanation of symbols

(1) Discharge electrode for placing workpiece
(2) Counter discharge electrode
(3) Solid dielectric
(4) Plasma generation space
(5a) Atmospheric gas supply pipe
(7) Discharge convex part
(8) Recess for discharge

Claims (1)

A discharge electrode for mounting a workpiece, a counter discharge electrode disposed opposite the discharge electrode, a solid dielectric provided on a surface of the counter discharge electrode on the discharge electrode for mounting the workpiece, and a solid A plasma processing apparatus comprising an atmosphere gas supply pipe for supplying an atmosphere gas to a space between a dielectric and a discharge electrode for placing a workpiece;
A plasma processing apparatus, wherein a discharge convex portion or a discharge concave portion is formed on a surface of a solid dielectric facing a counter discharge electrode.

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