JP2014003147A - Dry etching apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dry etching apparatus with excellent mass-productivity, the apparatus capable of forming a texture structure on a silicon substrate.SOLUTION: A dry etching apparatus EM for forming a texture structure on a surface of a silicon substrate W comprises: a freely rotatable drum electrode 2 arranged in a vacuum processing chamber 1a; at least one substrate holder 3 which is detachably attached to a circumferential surface of the drum electrode, and holds a plurality of silicon substrates along a generatrix direction of the drum electrode; a high-frequency power supply E for supplying high-frequency power to the drum electrode; and gas introduction means 4 for introducing an etching gas into a space between the drum electrode and a wall surface defining the vacuum processing chamber.

Description

  The present invention relates to a dry etching apparatus for forming a texture structure on a silicon substrate surface, and more specifically, a texture that exhibits a high light scattering containment effect on the surface of a silicon substrate in a manufacturing process of a crystalline solar cell. The present invention relates to a structure used for forming a structure with high productivity.

  In a crystalline solar cell using a monocrystalline or polycrystalline silicon substrate, the silicon substrate surface is roughened by forming an uneven shape by dry etching (providing a texture structure), and is incident on the silicon substrate surface. 2. Description of the Related Art Conventionally, efforts have been made to improve photoelectric conversion efficiency by reducing light reflection. Conventionally, a dry etching apparatus used for imparting a texture structure to the surface of a silicon substrate is known from Patent Document 1, for example.

  This is a stage for holding a silicon substrate in a vacuum processing chamber, a metal shower plate having a plurality of through holes disposed opposite to the silicon substrate held by the stage, and high-frequency power to the stage. A high-frequency power supply. Then, an etching gas is uniformly supplied to the silicon substrate through each through hole of the shower plate in a vacuum processing chamber under reduced pressure, and high-frequency power is supplied to the stage at a predetermined frequency (for example, 13, 56 MHz) to perform vacuum processing. A plasma is formed in the chamber, and active species and ion species generated in the plasma are incident on the surface of the silicon substrate for etching. At this time, the hydrocarbon (hydrocarbon) polymer film containing silicon oxide deposited on the substrate surface and oxygen in the etching gas act as a mask, so that the silicon substrate surface is etched into a rough shape and roughened. The texture structure is formed.

  However, in the above etching apparatus, for example, when the high frequency power to be input is set in a range in which abnormal discharge is unlikely to occur, a texture structure with a height of about 0.8 to 1.5 μm is formed on the silicon substrate surface. It cannot be said that the etching rate (for example, 5 to 10 nm / sec) is fast, and mass-productivity is remarkably low when a silicon substrate is etched one by one and a texture structure is imparted to the surface.

JP 2011-35262 A

  In view of the above points, an object of the present invention is to provide a dry etching apparatus having high mass productivity when a texture structure is formed on a silicon substrate.

  In order to solve the above-described problems, a dry etching apparatus of the present invention for forming a texture structure on a silicon substrate surface includes a rotatable drum electrode disposed in a vacuum processing chamber and a drum electrode peripheral surface that is detachable. There is at least one substrate holder for holding a plurality of silicon substrates along the generatrix direction of the drum electrode, a high frequency power source for supplying high frequency power to the drum electrode, a wall surface defining the vacuum processing chamber, and the drum electrode Gas introduction means for introducing an etching gas into a space between the two.

  According to the present invention, when an etching gas is introduced into the space between the wall surface of the vacuum processing chamber and the drum electrode, and high frequency power of a predetermined frequency is applied to the drum electrode, capacitively coupled high-density plasma is generated in the space. The active species and ion species formed in this plasma are incident on the silicon substrate surface, and the etching of the silicon substrate proceeds. At this time, a plurality of silicon substrates are arranged around the drum electrode, and the silicon substrate surface can be etched while rotating the drum electrode. Therefore, the number of processed substrates per unit time can be compared with the conventional example. Can be increased, and high mass productivity can be achieved. In this case, the frequency of the high-frequency power source is 13.56 MHz, the input power is set to 8 kW, and the etching rate when forming a texture structure with a height of about 0.8 to 1.5 μm on the silicon substrate surface is about It was confirmed to be 8 to 12 nm / sec. As the etching gas, for example, a gas containing fluorine-containing gas, halogen gas, and oxygen gas is used.

  In the present invention, a vacuum preparatory chamber is connected to the vacuum processing chamber on the axis of the rotation axis of the drum electrode, and a plurality of substrate holders on which silicon substrates are set are stocked in the vacuum preparatory chamber. It is preferable that a stock means is provided, and a vacuum auxiliary chamber in which an extruding means for pushing the substrate holder stocked in the stock means toward the drum electrode is connected to the vacuum preliminary chamber. According to this, a silicon substrate that has been previously degassed in the vacuum preliminary chamber can be transferred to the vacuum processing chamber, and an etching process can be performed on each silicon substrate, which is advantageous. Further, the vacuum preparatory chamber is an upstream vacuum preparatory chamber, and a downstream vacuum preparatory chamber is connected to the wall surface of the vacuum processing chamber facing the upstream vacuum preparatory chamber via a communication passage. Delivery means for delivering the substrate holder from the vacuum processing chamber to the vacuum preliminary chamber on the downstream side is provided, and when the substrate holder stocked in the stock means is pushed out toward the drum electrode by the extrusion means, it is attached to the drum electrode. If the other substrate holder is configured to be transferred to the vacuum preparatory chamber on the downstream side, a configuration for recovering the processed silicon substrate can be realized, which is advantageous.

The schematic diagram which shows the structure of the dry etching apparatus of embodiment of this invention. Sectional drawing which follows the II-II line | wire of FIG.

  Hereinafter, with reference to the drawings, an embodiment of a dry etching apparatus of the present invention for forming a texture structure on the surface of a single crystal or polycrystalline silicon substrate (hereinafter simply referred to as a substrate W) used in a crystalline solar cell will be described. To do. In addition, since the structure of a crystalline solar cell is well-known, detailed description is abbreviate | omitted here. In the following description, the axial direction of the rotation axis of the drum electrode is defined as the left-right direction and the direction orthogonal to the left-right direction is defined as the up-down direction with reference to FIG.

  With reference to FIG.1 and FIG.2, EM is the dry etching apparatus of this embodiment. The dry etching apparatus EM includes a cylindrical first chamber 1 that defines a central vacuum processing chamber 1a in which an etching process is performed. The first chamber 1 can be held by being evacuated to a predetermined pressure via a vacuum exhaust means P1 provided with a rotary pump, a turbo molecular pump, or the like. A drum electrode 2 is supported in the left and right side surfaces of the first chamber 1 via a rotation shaft 22 in the first chamber 1 and can be rotated at a constant rotational speed by a drive motor (not shown). Yes. The drum electrode 2 is made of a conductive material such as aluminum and has a regular octahedron outline.

  On the peripheral surface of the drum electrode 2, a pair of engaging claws 22a and 22b extending in the axial direction for receiving a substrate holder 3 to be described later is provided, and the bus bar of the drum electrode 2 is formed by the engaging claws 22a and 22b. A substrate holder 3 on which a plurality of substrates W are mounted at predetermined intervals along the direction is held. Here, the substrate holder 3 is composed of a plate-like member made of a conductive material having a plate thickness that is shorter than the width of the peripheral surface of the drum electrode 2 and shorter than the length of the drum electrode 2 and can maintain rigidity. On one surface thereof, a pair of left and right engaging claws 31a and 31b for receiving the substrate W are erected at a predetermined interval. Then, when the substrate W is slid along one surface of the substrate holder 3, the periphery of one surface (surface to be etched) of the substrate W engages with the engaging claws 31 a and 31 b and moves to the substrate holder 3. It is to be retained. The drum electrode 2 is connected to an output E1 from a high frequency power source E via a matching box MB. As the high frequency power source E, for example, a predetermined power (for example, 5 to 12 kW) is input to the drum electrode 2 at a frequency of 13.56 MHz, and a known one including the matching box MB can be used. Description is omitted.

Connected to the wall surface of the first chamber 1 is a gas introduction pipe 4 for introducing an etching gas into a space between the wall surface of the first chamber 1 defining the vacuum processing chamber 1 a and the drum electrode 2. In this case, the distal end portion of the gas introduction pipe 4 is branched into a plurality and connected to a plurality of locations on the wall surface of the first chamber 1. The gas introduction pipe 4 is also provided with a flow rate control means 41 having a function of closing the mass flow controller. The flow rate control means 41 communicates with a gas source outside the figure, and the flow rate-controlled etching gas is introduced into the space in the vacuum processing chamber 1a. I can do it. In this embodiment, a mixed gas containing a fluorine-containing gas such as NF ₃ , SF ₆ , or CxHyFz, a halogen-containing gas such as Cl ₂ or HBr, and an oxygen gas is used as the etching gas.

  Then, after evacuating to a predetermined pressure in the vacuum processing chamber 1a, an etching gas is introduced into the space in the vacuum processing chamber 1a, and this is performed while rotating the drum electrode 2 at a predetermined rotation speed (for example, 5 to 20 rpm). When high frequency power having a predetermined frequency is applied to the drum electrode 2 by a high frequency power source E, capacitively coupled high density plasma is formed in the space, and active species and ion species generated in the plasma are incident on the surface of the substrate W. The substrate W is etched. At this time, the hydrocarbon (hydrocarbon) polymer film containing silicon oxide deposited on the surface of the substrate W or oxygen in the etching gas serves as a mask, so that the surface of the substrate W is etched into an uneven shape. It is roughened to form a texture structure.

  In the dry etching apparatus EM, the second chamber 6 and the third chamber 7 are connected to the left and right sides of the first chamber 1 through communication paths 5a and 5b having gate valves GV1 and GV2, respectively. The second chamber 6 and the third chamber 7 define upstream and downstream vacuum preliminary chambers 6a and 7a, respectively. Since the internal structures of the second and third chambers 6 and 7 are basically the same, the second chamber 6 will be described below as an example.

  The second chamber 6 (7) can be evacuated and held at a predetermined pressure via a vacuum exhaust means P2 (P3) equipped with a rotary pump, a turbo molecular pump, etc., and a stock means 8 is provided therein. Yes. The stock means 8 includes a magazine 81 having a plurality of upper and lower shelves 81a that support the substrate holder 3, and a drive means 82 that drives the magazine 81 so as to be movable up and down, and a support plate 82a of the drive means 82 includes: It is connected to a slider 84 of a single-axis robot 83 arranged so as to extend in the vertical direction on the wall surface of the second chamber 6. Although not specifically illustrated and described, an openable / closable door is provided on the front surface of the second chamber 6 (7), and the substrate holder 3 can be set in the magazine 81 or the third chamber 7 can be opened in the air atmosphere. Thus, the substrate holder 3 after the etching process can be collected.

  A fourth chamber 9 is connected to the left side surface of the second chamber 6 facing the first chamber 1 through a gate valve GV3, thereby defining a vacuum auxiliary chamber 9a. The vacuum auxiliary chamber 9a can be held by being evacuated to a predetermined pressure via a vacuum exhaust means P4 equipped with a rotary pump, a turbo molecular pump or the like, and an extrusion means 90 is provided on the bottom surface thereof. The pushing means 90 includes a single-axis robot 91 arranged so as to extend in the left-right direction, and a pressing rod 93 that is cantilevered by a slider 92 of the single-axis robot 91. In this case, the length that allows the right end of the pressing rod 93 to enter the vacuum processing chamber 1a through the upstream vacuum preparatory chamber 6a is set, and the substrate holder 3 stocked by the stock means 8 is attached to the drum electrode 3. It extrudes to the peripheral surface located in the upper surface of the. In addition, a plurality of drive rollers R serving as delivery means are provided in the communication path 5b between the first chamber 1 and the third chamber 7 on the downstream side. Then, when the substrate holder 3 stocked in the stock means is pushed toward the drum electrode 2 by the pushing means 90, the other substrate holder 3 that holds the processed substrate W mounted on the drum electrode 2 is downstream. When the right end of the substrate holder 3 is frictionally engaged with the drive roller R located at the leftmost end, the substrate holder 3 is moved from the left to the right by each drive roller R. And is stored in one of the shelves 81a in the vacuum preparatory chamber 7a on the downstream side. Below, the etching process to the board | substrate W using the said etching apparatus EM is demonstrated.

  First, a plurality of substrates W are set on one substrate holder 3 at a position outside the figure as described above, and a plurality of substrate holders 3 on which these substrates W are set are placed in the vacuum preliminary chamber 6a on the upstream side in the atmospheric state. The magazine 81 is set so as to be supported by the shelf 81a. Then, the vacuum preliminary chamber 6a is evacuated to a predetermined pressure. Each of the gate valves GV1 to GV3 is in a closed state, and the vacuum processing chamber 1a, the downstream vacuum preliminary chamber 7a, and the vacuum auxiliary chamber 9a are evacuated to a predetermined pressure. When each chamber reaches a predetermined pressure, the gate valves GV1 and GV3 are opened, and when the pressing rod 93 of the pushing means 90 is moved from left to right, the substrate holder 3 located at the uppermost stage is moved to the drum electrode 2. Extruded toward the top surface of At this time, when the substrate holder 3 slides on the upper surface of the drum electrode 2 between the pair of engaging claws 22a and 22b and reaches a predetermined position, the movement of the pushing means 90 is stopped. Thereby, the board | substrate holder 3 is hold | maintained by engagement claw part 22a, 22b. After the pressing rod 93 of the pushing means 90 is once returned to the vacuum auxiliary chamber 9a, the magazine 81 is moved upward, the drum electrode 2 is rotated by a predetermined angle (30 degrees), and the substrate holder 3 is moved by the above operation. Set to. By repeating this operation, the substrate holders 3 holding the plurality of unprocessed substrates W are respectively mounted on the peripheral surface of the drum electrode 2.

When the substrate holder 3 is set on the entire peripheral surface of the drum electrode 2, the gate valves GV1 and GV3 are closed, and the vacuum processing chamber 1a is evacuated to a predetermined pressure as described above. An etching gas (for example, the flow rate of NF ₃ : Cl ₂ : oxygen gas is 700: 1400: 300 sccm) is introduced into the space, and this drum electrode 2 is rotated while rotating the drum electrode 2 at a predetermined rotation speed (for example, 5 to 20 rpm). 2 is supplied with high frequency power (for example, 13.56 MHz, 8 kW) at a predetermined frequency from a high frequency power source E, and capacitively coupled high-density plasma is formed in the space, and active species and ion species generated in the plasma. Is incident on the surface of the substrate W, and the substrate W is etched. Thereby, a texture structure having a height of about 0.8 to 1.5 μm is formed on the surface of the substrate W. Simultaneously with this etching process, the upstream vacuum preliminary chamber 6a is opened to the atmosphere, and the substrate holder 3 on which the unprocessed substrate W is set is set on each shelf 81a of the magazine 81 in the same procedure as described above.

  When the etching process is finished, each of the gate valves GV1 to GV3 is opened and the pressing rod 93 of the pushing means 90 is moved from the left to the right, so that the substrate holder 3 located at the uppermost stage faces the upper surface of the drum electrode 2. Extruded. At this time, the substrate holder 3 pushes the substrate holder 3 holding the processed substrate W toward the downstream vacuum preparatory chamber 7a, and the drive roller R in which the right end of the substrate holder 3 is positioned at the leftmost end. Is frictionally engaged, the substrate holder 3 is sent by the drive roller R and stored in the shelf 81a of the magazine 81 in the vacuum preparatory chamber 7a on the downstream side. By repeating the above operation, the setting of the substrate holder 3 on which the unprocessed substrate W is set on the drum electrode 2 and the recovery of the substrate holder 3 on which the processed substrate W is set are simultaneously performed.

  According to the above, since a plurality of substrates W are arranged around the drum electrode 2 and the surface of the substrate W can be etched while rotating the drum electrode 2, the unit time can be compared with the conventional example. The number of processing per hit can be increased, and high mass productivity can be achieved. In addition, since the upstream vacuum preparatory chamber 6a is provided, it is advantageous that the substrate W that has been previously degassed can be transferred to the vacuum processing chamber 1a and subjected to the etching process on each substrate W. . Moreover, since the setting of the substrate holder 3 on which the substrate W before processing on the drum electrode 2 is set and the recovery of the substrate holder 3 on which the processed substrate W is set are performed simultaneously, mass productivity is improved. Further improvement can be achieved.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to said thing. In the above embodiment, an example in which a vacuum preparatory chamber and a vacuum auxiliary chamber are connected to the vacuum processing chamber has been described as an example. However, the present invention is not limited to this, and batch processing is performed only in the vacuum processing chamber. May be. In the above embodiment, the regular octahedron is used. However, the outline of the drum electrode 2 is not limited to this, and may be a dodecahedron or a 24-hedron.

  EM: dry etching apparatus, 1a ... vacuum processing chamber, 2 ... drum electrode, 3 ... substrate holder, 6a, 7a ... vacuum preparatory chamber, 4 ... gas introduction pipe, 5a, 5b ... communication path, 8 ... stock means, 90 ... Extruding means, E ... high frequency power source, R ... driving roller (feeding means), W ... substrate (silicon substrate).

Claims (3)

A dry etching apparatus for forming a texture structure on a silicon substrate surface,
A rotatable drum electrode disposed in the vacuum processing chamber; and at least one substrate holder that is detachably attached to a peripheral surface of the drum electrode and holds a plurality of silicon substrates along a generatrix direction of the drum electrode; A dry etching apparatus comprising: a high frequency power source for supplying high frequency power to a drum electrode; and gas introducing means for introducing an etching gas into a space between a wall surface defining a vacuum processing chamber and the drum electrode.   In the vacuum processing chamber, a vacuum preparatory chamber is provided continuously on the axis of the rotation axis of the drum electrode, and stocking means for stocking a plurality of substrate holders on which silicon substrates are set is provided in the vacuum preparatory chamber. 2. The dry etching apparatus according to claim 1, wherein a vacuum auxiliary chamber in which an extruding unit for extruding the substrate holder stocked in the stock unit toward the drum electrode is provided in the vacuum preliminary chamber.   The vacuum preparatory chamber is an upstream vacuum preparatory chamber, and a downstream vacuum preparatory chamber is connected to the wall surface of the vacuum processing chamber facing the upstream vacuum preparatory chamber via a communication path, and the substrate holder is connected to the communication path. When the substrate holder stocked in the stock means is pushed out toward the drum electrode by the extruding means, the other means attached to the drum electrode are provided. 3. The dry etching apparatus according to claim 2, wherein the substrate holder is configured to be transferred to a vacuum preparatory chamber on the downstream side.

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