JP2013222880A - Etching mask - Google Patents

Abstract

An etching mask that prevents etching outside a desired range of a wafer having a texture structure is obtained.
An etching gas is prevented from entering the texture structure from the side surface side of the wafer 1 when a plurality of wafers 1 having texture structures provided on the front and back are stacked and the side surfaces of the wafer 1 are etched. A plurality of protective plates 8 that are in contact with a portion where the texture structure of the side surface of the plurality of stacked wafers 1 is formed, and each of the plurality of protective plates 8 is kept at an equal interval. A protective plate support for holding is provided.
[Selection] Figure 1

Description

  In the manufacturing process of a solar cell, the present invention diffuses minority carriers (for example, phosphorus) into a silicon wafer to form a pn junction therein, and then dry-etches the side surface of the wafer to establish a conductive state between the light receiving surface and the back surface. The present invention relates to an etching mask used for separation.

  In the manufacturing process of a solar cell, after minority carriers (for example, phosphorus) are diffused into a silicon wafer to form a pn junction therein, the side surface of the wafer is dry etched to separate the conductive state between the light receiving surface and the back surface. Hereinafter, this process is referred to as “pn separation”.

  In a conventional dry etching pn separator, a plurality of wafers are stacked and the upper and lower two wafers are replaced with dummy wafers, or the upper and lower sides are sandwiched between plate-like jigs so that only the wafer side surface is exposed. Is held by a fixture and etched.

  This is to improve the work efficiency by etching only the wafer side surface and simultaneously processing a plurality of wafers.

  In the pn separation, it is important to etch only the side surface of the wafer. When etching reaches the wafer surface, the power generation region (pn junction region) occupying the light receiving surface of the solar cell is reduced, and the cell efficiency is lowered. Is concerned.

  In order to realize the above contents, for example, a method as in Patent Document 1 has been proposed.

JP-T-2003-533008 (9th page, 14th line to 10th page, 2nd line, FIG. 2)

  In general, in order to suppress loss due to reflection of light on the light receiving surface of the solar battery cell, there is a method of forming an uneven shape called a texture structure on the wafer surface serving as the light receiving surface.

  However, when a wafer having this texture structure is pn-separated by dry etching, there is an uneven shape on the surface, so that a gap is generated between the stacked wafers. When the etching gas flows into this gap, a region outside the desired range (such as the wafer surface) is etched.

  Increasing the load holding the stacked wafers from above and below may compress the gap and reduce the inflow of the etching gas, but increases the possibility of damage such as chipping of the texture structure or cracking of the cells.

  The present invention has been made in view of the above, and an object of the present invention is to obtain an etching mask that prevents etching outside a desired range of a wafer having a texture structure.

  In order to solve the above-mentioned problems and achieve the object, the present invention provides a texture structure from the side surface side of the wafer when a plurality of wafers having texture structures provided on the front and back surfaces are stacked and each side surface of the wafer is etched. An etching mask for preventing an etching gas from entering the substrate, and a plurality of protective plates that are in contact with a portion where the texture structure of the side surface of the plurality of laminated wafers is formed, and each of the plurality of protective plates And a protective plate support portion that supports the same while keeping the distance between them equal.

  According to the present invention, it is possible to prevent the outside of a desired range of a wafer having a texture structure from being etched.

FIG. 1 is a perspective view showing the configuration of the first embodiment of an etching mask according to the present invention. FIG. 2 is a top view of the etching mask according to the first embodiment. FIG. 3 is an enlarged cross-sectional view of a contact portion between the etching mask and the wafer according to the first embodiment. FIG. 4 is a diagram for explaining a procedure in a preparation stage for performing a pn separation process on laminated wafers. FIG. 5 is a cross-sectional view of the dry etching apparatus in a state where stacked wafers are set. FIG. 6 is a perspective view showing the configuration of the second embodiment of the etching mask according to the present invention. FIG. 7 is a schematic diagram of the periphery of the protective plate in the initial mask height state of the etching mask according to the second embodiment. FIG. 8 is a schematic diagram of the periphery of the protective plate when the mask height of the etching mask according to the second embodiment is adjusted. FIG. 9 is a schematic side view of the periphery of the screw feed mechanism in the initial height state of the etching mask according to the second embodiment. FIG. 10 is a schematic side view of the periphery of the screw feed mechanism when adjusting the height of the etching mask according to the second embodiment. FIG. 11 is a schematic diagram showing the configuration of the third embodiment of the etching mask according to the present invention. FIG. 12 is an enlarged cross-sectional view of Embodiment 4 of the etching mask according to the present invention. FIG. 13 is an enlarged cross-sectional view of Embodiment 5 of the etching mask according to the present invention.

  Embodiments of an etching mask according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a perspective view showing the configuration of the first embodiment of an etching mask according to the present invention. FIG. 2 is a top view of the etching mask according to the first embodiment. The etching mask 50 is in contact with the side surfaces of a plurality of laminated wafers 1 to protect it from being etched outside the desired range, and between the protection plates 8 so as to place the protection plate 8 thereon. A plurality of spacers 9 as protective plate holding members inserted into the spacer, a spacer support portion 10 as a protective plate holding member support portion that supports the plurality of spacers 9 while maintaining a predetermined interval, and a protective plate 8 and a spacer support portion. 10 and a base 11 to which 10 is attached. The plurality of spacers 9, the spacer support portions 10, and the base 11 form a protection plate support portion that supports each of the plurality of protection plates 8 while maintaining the same interval therebetween.

  A plurality of spacers 9 and spacer support portions 10 may be provided on one base 11.

The protective plate 8, the spacer 9, the spacer support 10 and the base 11 are materials that are not etched by a fluorine-based gas such as CF ₄ (carbon tetrafluoride) or CHF ₃ (methane trifluoride) used for etching silicon. It is necessary to use stainless steel or aluminum. Further, the protective plates 8 and the spacers 9 need to be at least as many as the stacked wafers 1. However, the number of protection plates 8 may be adjusted according to the number of wafers 1 to be laminated, or dummy wafers may be additionally laminated for the number of wafers 1 that are insufficient with respect to the number of protection plates 8.

  As shown in FIG. 2, two bases 11 are set as one set, and the stacked wafers 1 are attached so as to be sandwiched from both side surfaces. The two bases 11 are connected and fixed to each other with fasteners or bolts. The base 11 may be divided into three or more according to the shape and size of the wafer 1 and attached so as to surround the side surfaces of the laminated wafers 1.

  FIG. 3 is an enlarged cross-sectional view of a contact portion between the etching mask and the wafer according to the first embodiment. The protective plate 8 of the etching mask 50 is stacked and supported by the spacers 9 with a gap at equal intervals in the vertical direction so that the plate surface is parallel to the horizontal plane. Then, in a state where the side surfaces of the wafer 1 and the protective plate 8 face each other, the protective plate 8 of the etching mask 50 is pressed against the side surface of the laminated wafer 1 so as to cover the gap between the wafer 1 and the wafer 1.

  The texture structure 12 is generally formed on both the front and back surfaces of the wafer 1. In this specification, the texture structure 12 has a pyramid shape as an example.

  For example, when the dimension (height) in the thickness direction of the wafer 1 of the texture structure 12 is 20 μm, the dimension in the thickness direction of the wafer 1 in the gap generated when two wafers 1 are stacked is 40 μm. For this reason, the thickness of the protective plate 8 of the etching mask 50 is required to be at least 40 μm. As described above, the thickness of the protection plate 8 is set to be twice or more the height of the texture structure 12.

  As a processing procedure, the upper and lower sides of the laminated wafers 1 are sandwiched between plate members 2 and fixed by a fixing jig 3. Then, with the etching mask 50 attached, it is set in the dry etching apparatus 4 and the etching process is started.

  FIG. 4 is a diagram for explaining a procedure in a preparation stage for performing a pn separation process on laminated wafers. A plurality of wafers 1 are laminated, and the upper and lower sides of the laminated wafers 1 are sandwiched between plate members 2 such as dummy wafers and fixed by a fixing jig 3. Then, an etching mask 50 is attached so as to sandwich the laminated wafer 1 from both sides. At this time, the wafer 1 is in a state where only the portion where the texture structure 12 on the side surface is not formed is exposed.

  The wafer 1 has, for example, an octagonal shape with four corners chamfered as shown in FIGS. 1 and 2, a size of 156 mm × 156 mm, and a thickness of 200 μm. When the number of stacked layers during dry etching is 200 to 300, the total thickness of the stacked wafers 1 is 40 to 50 mm.

  FIG. 5 is a cross-sectional view of the dry etching apparatus in a state where stacked wafers are set. The laminated wafer 1 is set on a turntable 6 in a chamber 5 of a dry etching apparatus 4. An etching gas 7 is flowed from one direction parallel to the planar direction of the laminated wafers 1 while the chamber 5 is maintained in a vacuum. The turntable 6 rotates at a constant speed, and the side surfaces of the stacked wafers 1 are uniformly etched.

  The etching region 13 where the protection plate 8 on the side surface of the wafer 1 is not in contact is exposed to the etching gas 7, but the protection plate 8 covers the gap formed by the texture structure 12 on the surface of the wafer 1. Since it is difficult to flow in, etching of the surface of the wafer 1 can be suppressed.

  If the width dimension in the surface direction of the protection plate 8 is wide, the generated gas after etching the wafer 1 tends to stay between the protection plates 8, and there is a concern that the inflow of the etching gas 7 may be hindered. For example, when the width of the protective plate 8 is 10 to 20 mm and the flow of the etching gas 7 is not sufficient, it is necessary to adjust the width dimension.

  In addition, the numerical value shown by said description is an example to the last, and this invention is not limited to these numerical values.

  In the present embodiment, since the wafer surface is not etched during pn separation, the ratio of the power generation region in the light receiving surface of the solar battery cell can be increased, and the conversion efficiency can be improved. Therefore, a module having a desired output can be reduced in size by configuring the solar battery module with solar cells having high conversion efficiency.

Embodiment 2. FIG.
FIG. 6 is a perspective view showing the configuration of the second embodiment of the etching mask according to the present invention. The etching mask 50 is in contact with the side surface of the laminated wafer 1 to protect the outside of the desired range from etching, and the spacer 9 is inserted between the protective plates 8 to maintain a constant interval. In addition to a protective plate support portion having a spacer support portion 10 that supports and rotates a plurality of spacers 9, and a base 11 that attaches the protective plate 8 and the spacer support portion 10 in a movable state, A detachable screw feed mechanism 14 for adjusting the gap is provided.

  Note that the material and dimensions of each member and the use of a plurality of bases 11 as one set are the same as in the first embodiment.

  Further, a plurality of spacer support portions 10 may be provided on one base 11.

  FIG. 7 is a schematic diagram of the periphery of the protective plate in the initial mask height state of the etching mask according to the second embodiment. FIG. 8 is a schematic diagram of the periphery of the protective plate when the mask height of the etching mask according to the second embodiment is adjusted. FIG. 9 is a schematic side view of the periphery of the screw feed mechanism in the initial height state of the etching mask according to the second embodiment. FIG. 10 is a schematic side view of the periphery of the screw feed mechanism when adjusting the height of the etching mask according to the second embodiment.

  The operation of the protective plate 8 when adjusting the mask height will be described with reference to FIGS. As shown in FIG. 7, columnar spacers 9 are rotatably supported by spacer support portions 10 at regular intervals, and a protective plate 8 is placed on each spacer 9. The spacer shape may be a plate shape. The lower end of the spacer support portion 10 is rotatably supported by the base 11. The protective plate 8 is attached to the base 11 so as to be movable in the vertical direction.

  In this way, the state in which the spacer support portion 10 is perpendicular to the horizontal plane is the initial state of the height of the etching mask 50.

  As shown in FIG. 8, at the time of adjusting the height of the etching mask 50, it is tilted with the rotation support portion of the spacer support portion 10 as the rotation center. At this time, since the vertical interval between the spacers 9 is always constant, the height of the entire etching mask 50 is lowered while the protective plate 8 placed on the spacer 9 is also maintained at a constant interval.

  The operation of the screw feed mechanism at the time of mask height adjustment will be described based on FIGS. As shown in FIG. 9, the upper end of the spacer support portion 10 is attached to a slide block 16 that can slide on the base 11 in one direction. The slide block 16 is fitted in a groove provided in the base 11 and is attached so as not to move upward (cannot be separated from the base 11). In addition, the attachment part of the upper end of the spacer support part 10 and the slide block 16 is movable to an up-down direction. The detachable screw feed mechanism 14 is positioned and attached on the base 11 with a positioning pin or the like, and adjusted to a position where the spindle 17 contacts the contact surface of the slide block 16.

  As in FIG. 7, the state in which the spacer support portion 10 is perpendicular to the horizontal plane is the initial state of the height of the etching mask 50. As shown in FIG. 10, when adjusting the height of the etching mask 50, the screw feed mechanism 14 is rotated and the spindle 17 is pushed in. As a result, the slide block 16 moves in the horizontal direction, the spacer support portion 10 is tilted, and the overall height of the etching mask 50 is lowered. As the spacer support portion 10 is tilted, the upper end of the spacer support portion 10 and the slide block 16 The mounting part moves downward.

  The etching mask 50 is fixed after the height is adjusted by tightening the fixing screw 18 attached to the slide block 16. By tightening the fixing screw 18, the tip of the fixing screw 18 is strongly pressed against the base 11, and the sliding movement of the slide block 16 is restricted. After adjusting the height of the base 11, the stacked wafers 1 are sandwiched and fixed, the screw feed mechanism 14 is removed, and the dry etching apparatus 4 is set.

  If the thickness of the wafer 1 to be used or the etching amount (damage etching amount) at the time of removing the damaged layer generated when slicing the wafer 1 is changed due to a change in the specification of the solar battery cell or the like, The thickness changes. Further, as the number of stacked layers increases, the influence of the change in the overall thickness of the stacked wafers 1 increases. However, by adjusting the overall height of the etching mask 50 while maintaining the distance between the protective plates 8 of the etching mask 50 at equal intervals, it is possible to cope with a change in the thickness of the wafer 1.

  A micrometer can be applied as the screw feeding mechanism 14. In this case, the height of the etching mask 50 is adjusted so that the interval between the protective plates 8 becomes a desired value by waving a scale on the fixed shaft portion of the micrometer so as to correspond to the interval between the protective plates 8. It becomes easy to adjust.

Embodiment 3 FIG.
FIG. 11 is a schematic diagram showing the configuration of the third embodiment of the etching mask according to the present invention. As shown in FIG. 11, a plurality of protection plates 8 are connected by an elastic member 19 such as a leaf spring. Other configurations are the same as those in the second embodiment.

  By connecting the protection plate 8 with the elastic member 19, when the height of the etching mask 50 is adjusted, the protection plates 8 are attracted to each other, so that the backlash in the vertical direction of the protection plate 8 can be suppressed.

Embodiment 4 FIG.
FIG. 12 is an enlarged cross-sectional view of Embodiment 4 of the etching mask according to the present invention. The configuration of the etching mask 50 is the same as that of the first embodiment. As shown in FIG. 12, one protective plate 8 for the etching mask 50 is provided for two wafers 1.

  The reason is that only one side of the surface of the wafer 1 is used as the light receiving surface 20, and the remaining one surface on the back side of the light receiving surface 20 has an effect on the characteristics of the solar cell even if the pn junction is etched. There is no distinction between the front and back sides of the wafer 1 in the point considered not to reach and the step of performing the pn separation, and either one may be used as the light receiving surface 20. For this reason, it is considered that the wafers 1 are alternately stacked, and only the portion where the surfaces used as the light receiving surface 20 face each other is protected by the etching mask 50. Therefore, the side surface of the wafer 1 and the back surface of the wafer 1 become the etching region 13.

  After the pn separation, the wafers 1 are inverted and aligned for each sheet before a CVD (Chemical Vapor Deposition) process for forming an AR (Anti-Reflection) film.

  In the present embodiment, the number of protection plates 8 may be half, and the number of parts can be reduced. Moreover, the tolerance of the dimension of the spacer 9 increases, and parts processing becomes easy.

Embodiment 5 FIG.
FIG. 13 is an enlarged cross-sectional view of Embodiment 5 of the etching mask according to the present invention. As shown in FIG. 13, an elastic sheet 21 is sandwiched between wafers 1 to be laminated. Other configurations of the etching mask 50 are the same as those in the first embodiment. That is, the thickness of the protective plate 8 is twice the height of the texture structure + the thickness of the elastic sheet 21 or more. Further, the interval between the protective plates 8 is the thickness of the wafer 1 + the thickness of the elastic sheet 21.

  The elastic sheet 21 uses, for example, a plasma-resistant silicone rubber or a polymer material such as fluorine rubber, and has a thickness of about 1 mm, for example. The side surface of the wafer 1 becomes an etching region 13.

  Thereby, when the wafers 1 are stacked, it is possible to suppress damage such as the tip of the texture structure 12 being lost due to contact between the wafers 1. Further, in combination with the etching mask 50, the effect of suppressing the inflow of the etching gas to the surface of the wafer 1 by the elastic sheet 21 is improved. Further, the tolerance increases in the thickness dimension of the protective plate 8 by the thickness of the elastic sheet 21, and the part processing becomes easy.

  As described above, the etching mask according to the present invention is useful in that it can prevent etching outside a desired range of a wafer having a texture structure.

DESCRIPTION OF SYMBOLS 1 Wafer 2 Plate member 3 Fixing jig 4 Dry etching apparatus 5 Chamber 6 Rotary table 7 Etching gas 8 Protection plate 9 Spacer 10 Spacer support part 11 Base 12 Texture structure 13 Etching area 14 Screw feed mechanism 16 Slide block 17 Spindle 18 Fixing Screw 19 Elastic member 20 Light receiving surface 21 Elastic sheet 50 Etching mask

Claims (6)

An etching mask that prevents an etching gas from entering the texture structure from the side surface of the wafer when a plurality of wafers having texture structures on the front and back surfaces are stacked and the side surfaces of the wafer are etched. Because
A plurality of protective plates to be brought into contact with a portion where the texture structure is formed on the side surface of the plurality of laminated wafers;
An etching mask, comprising: a protection plate support portion that supports each of the plurality of protection plates while maintaining an equal interval therebetween.   The protection plate support section includes a plurality of protection plate holding members on which the plurality of protection plates are placed, and a protection plate holding member that supports each of the plurality of protection plate holding members while maintaining an equal interval therebetween. The etching mask according to claim 1, further comprising a support portion and a base to which the protection plate and the protection plate holding member support portion are attached.   3. The etching mask according to claim 2, wherein the protection plate support portion supports the plurality of protection plates so that a distance between the protection plates can be changed. The protective plate holding member support is attached to the base so that the inclination with respect to the base can be changed,
The etching mask according to claim 3, further comprising a screw feed mechanism that adjusts an interval between the protective plates by changing an inclination of the protective plate holding member supporting portion with respect to the base.   The etching mask according to claim 3 or 4, wherein the plurality of protective plates are connected by an elastic member.   6. The etching device according to claim 1, wherein the plurality of protective plates are in contact with a side surface of a portion where the texture structure is formed on either one of the front and back surfaces of the wafer. mask.

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