JP2015123654A - Cutting method of workpiece - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cutting method of a workpiece which can reduce occurrence of cracks and chipping of a cutting end part.SOLUTION: A cutting method of a workpiece 1 includes a processing step of putting a cutting blade travelling to the workpiece 1 in an upper surface of the workpiece 1 at a start of cutting, and letting the cutting blade 2 out from a lower surface 1d of the workpiece 1 at an end of cutting. The processing step includes a step of placing a part except for a cut part 5 of the lower surface 1d of the workpiece 1 on a plurality of pedestals 6 arranged separately from each other, and positioning the cut part 5 between the two adjacent pedestals 6, and cutting a contact member 4 by the cutting blade 2 in a state that the contact member 4 is arranged in a region including the cut part 5 of the lower surface 1d of the workpiece 1.

Description

  The present invention relates to a method for cutting a workpiece such as a semiconductor ingot.

  Conventionally, a polycrystalline silicon substrate has been used as one of semiconductor substrates constituting a solar cell element. In general, a polycrystalline silicon substrate is manufactured by making a block of a silicon ingot produced by a casting method by a cutting method using a band saw and slicing the block using a wire saw.

  In the cutting method using a band saw, first, the end portion of the ingot is removed, and the block is further cut out from the ingot into blocks of a desired size (see, for example, Patent Document 1 below).

  Prior to cutting the ingot by the band saw, the ingot is placed on the pedestal. A groove is formed on the pedestal so that the band saw does not contact the pedestal.

JP 2011-46043 A

  When the ingot is cut into a block having a desired size using a band saw, the cutting position at the end changes depending on the shape of the ingot. For this reason, it is necessary to increase the width of the groove provided in the pedestal. However, when the width of the groove portion is increased, stress concentrates on the cutting portion on the lower surface of the ingot due to the cutting load of the cutting blade immediately before the end of the ingot cutting. For this reason, cracks and chipping may occur around the cut site.

  Accordingly, an object of the present invention is to provide a workpiece cutting method that can reduce the occurrence of cracks and chips at the end of cutting.

In order to solve the above problems, a cutting method for a workpiece according to one aspect of the present invention is such that a cutting blade that travels with respect to a workpiece is placed on the upper surface of the workpiece at the start of cutting, and the cutting ends A workpiece cutting method having a processing step of sometimes taking out the cutting blade from the lower surface of the workpiece,
In the processing step, a part of the workpiece excluding the cutting site on the lower surface is placed on a plurality of pedestals arranged apart from each other, and the cutting site is positioned between two adjacent pedestals. And a step of cutting the contact member by the cutting blade in a state where the contact member is disposed in a region including the cutting site on the lower surface of the workpiece.

  According to the above-described method for cutting a workpiece, it is possible to reduce the occurrence of cracks and chips at the end of cutting in the workpiece.

It is a perspective view which shows the cutting method of the to-be-processed object which concerns on one Embodiment of this invention. It is a top view which shows the arrangement | positioning aspect of the contact member used for the cutting method of the workpiece which concerns on one Embodiment of this invention. It is a figure explaining the cutting location of the workpiece which concerns on one Embodiment of this invention, (a) is a perspective view of the workpiece before a cutting | disconnection, (b) is a disassembled perspective view of the workpiece after a cutting | disconnection. FIG. (A)-(c) is sectional drawing which shows the arrangement | positioning aspect of the contact member in the cutting process of the workpiece which concerns on one Embodiment of this invention, respectively, and is sectional drawing in the XZ plane of FIG. (A)-(c) is sectional drawing which shows the arrangement | positioning aspect of the contact member in the cutting process of the workpiece which concerns on one Embodiment of this invention, respectively, and is sectional drawing in the XZ plane of FIG. (A), (b) is sectional drawing which shows the cutting state of the to-be-processed object which concerns on one Embodiment of this invention, respectively, and is sectional drawing in the XZ plane of FIG. (A), (b) is sectional drawing which shows the cutting state of the to-be-processed object which concerns on an Example, respectively, and is sectional drawing in the XZ plane of FIG. (A), (b) is sectional drawing which shows the cut state of the to-be-processed object which concerns on a comparative example, respectively, and is sectional drawing in the XZ plane of FIG. It is a perspective view which shows the cut location of the to-be-processed object which concerns on an Example and a comparative example.

  Hereinafter, an embodiment of a method for cutting a workpiece according to the present invention will be described in detail with reference to the drawings. In addition, since drawing is shown typically, the size of each component shown, positional relationship, etc. can be changed suitably. In FIG. 1, a right-handed XYZ coordinate system with the + Z direction as viewed in the drawing is attached.

  As an example of the semiconductor ingot, an example in which a silicon ingot suitable for manufacturing a semiconductor substrate for a solar cell is used will be described.

<Method for producing semiconductor ingot>
The ingot is produced by a casting method. The casting method includes a step of preparing a silicon melt, a step of placing a silicon melt in a mold, and a step of solidifying the melt.

  First, the process for preparing the silicon melt will be described. A predetermined amount of silicon material and a dopant source are held inside the crucible. Note that boron is used as the dopant source when p-type silicon is produced, and phosphorus is used when n-type silicon is produced. Then, the silicon material and the dopant source are melted by the crucible heating means to produce a silicon melt containing the molten mixture, that is, the dopant source.

  Next, a process of bringing the silicon melt into a mold having a plurality of inner wall surfaces and having an opening in the upper part surrounded by the plurality of inner wall surfaces will be described. The melt is poured from a crucible containing a silicon melt adjusted to a predetermined temperature into a mold that has been heated in advance. The mold is placed in an argon (Ar) atmosphere whose pressure is reduced to 9 kPa or more and 12 kPa or less. The mold may be heated to a temperature that is the same as or slightly lower than the melting point of silicon, for example, a temperature that is several tens to several hundreds of degrees below the melting point.

  Next, the process of solidifying the melt in the mold will be described. In this solidification step, the melt is cooled from below by the cooling means while being heated from above by the mold heating means. Thereby, a positive temperature gradient is provided from the bottom to the top of the mold, and the melt can be sequentially solidified in one direction from the bottom to the top.

Through such a solidification step, the melt is completely solidified and cooled, whereby a silicon ingot can be produced. At this time, the surface of the side part and the bottom part of the ingot taken out from the mold has an uneven shape due to the influence of the mold release material and the mold shape.

<Semiconductor ingot cutting method with band saw>
Next, an ingot cutting method using a band saw will be described. As shown in FIG. 1, a band saw S is used to cut the ingot 1 produced by the casting method. The band saw S includes a cutting blade 2 and a pulley 3. The cutting blade 2 is composed of a blade 2b having a blade portion 2a on the cutting portion side. For example, a cemented carbide tool or abrasive grains (diamond or CBN (cubic boron nitride)) or the like is used for the blade portion 2a. For the blade 2b, for example, an endless belt made of an alloy such as stainless steel or high-tensile steel is used. The blade 2b is stretched between two pulleys 3 and fixed with a blade fixing tool. In this state, the blade 2b is moved downward by rotating the pulley 3 while rotating the blade 2b. In this way, the blade portion 2a of the blade 2b is pressed against the upper surface 1c of the ingot 1 located below the band saw S, and the ingot 1 is cut.

  In addition, it is preferable that the rotational speed of the blade 2b at the time of cutting is 100 m / min to 1000 m / min, and the descending speed of the blade 2b is 1 mm / min to 15 mm / min.

  In this embodiment, as shown in FIG. 6 (a), the traveling cutting blade 2 is put into the upper surface 1c of the ingot 1 at the start of cutting, and as shown in FIG. 6 (b), the lower surface of the ingot 1 at the end of cutting. It has the processing process which takes out the cutting blade 2 from 1d. In this processing step, a part of the lower surface 1d of the ingot 1 except for the cutting site 5 is placed on a plurality of pedestals 6 that are arranged apart from each other. In addition, the lower surface 1d of the ingot 1 is a solidification start surface (bottom part) of the ingot 1, for example. Further, the cutting member 5 is positioned between two adjacent pedestals 6, and the abutting member 4 is disposed by the cutting blade 2 in a state where the abutting member 4 is disposed in a region including the cutting portion 5 on the lower surface 1 d of the ingot 1. Including a cutting step. The cutting blade 2 may be moved relative to the ingot 1. The height at which the abutting member 4 is cut is controlled to be equal to or lower than the height of the base 6.

  As shown in FIGS. 2 and 4A, the ingot 1 is disposed on the pedestal 6 so that the cutting site 5 is located in the gap of the pedestal 6. Between the lower surface 1d of the ingot 1 and the pedestal 6, the ingot 1 is fixed to the pedestal 6 by disposing an adhesive layer 8 made of, for example, an adhesive. As the adhesive, for example, a curable adhesive is used. As the curable adhesive, for example, a two-component adhesive that is used by mixing the mass of the main agent at a ratio of 1 to 2.5 with respect to the mass 1 of the curing agent is used. Here, an epoxy resin or an acrylic resin is used as the main agent. As the curing agent, polyamide resin or polythiol resin is used. Note that the ingot 1 may be fixed to the pedestal 6 by using a clamp, vacuum suction or the like without using the adhesive layer 8.

  In addition, as shown in FIG. 2, the abutting member 4 is disposed between the cutting portion 5 on the lower surface 1 d of the ingot 1 and the periphery thereof, that is, between the adjacent pedestals 6. Details of the base 6 and the abutting member 4 will be described later.

Next, the cutting part of the ingot 1 is demonstrated using FIG. 3 (a), (b). In addition, the dashed-dotted line shown by Fig.3 (a) is the first cutting location, and this cutting location goes down in the figure as cutting progresses. The side surface portion 1b of the ingot 1 contains a large amount of impurities and the like and is relatively poor in quality. Then, the ingot 1 excluding such end material is cut to form, for example, a plurality of 10 cm square or 15 cm square blocks 1a. For example, when nine blocks 1a are taken out from one ingot 1, first, the ingot 1 is cut in the order of A1, A2, A3, and A4 as shown in FIG. Next, the ingot 1 is cut in the order of B1, B2, B3, and B4. Thereby, as shown in FIG.3 (b), the several block 1a with which the shape where the side part 1b was isolate | separated was cut out.

  Next, the pedestal 6 will be described in detail. The plurality of bases 6 are fixed to the plate 7 with a certain gap, for example. The cutting part 5 of the ingot 1 is located in the gap between the pedestals 6, and the ingot 1 is arranged on the upper surface of the pedestal 6. However, the aspect of the base 6 is not limited to the said structure. For example, a plurality of pedestals 6 separated by the groove portions may be arranged by providing the groove portions in a lattice shape in a member made of a square pole. For the base 6 and the plate 7, for example, stainless steel, glass, aluminum alloy, or the like is used.

  The width W of the gap between the plurality of bases 6 shown in FIG. 2 is determined by the size of the block 1 a cut out from the ingot 1. For example, when cutting out a 15 cm square block 1a, it is preferably 20 mm or more and 60 mm or less. The width W of the gap between the plurality of bases 6 is preferably 20 mm or greater and 70 mm or less, for example. By setting it as the said range, it is reduced that the cutting position of the ingot 1 shifts | deviates. Moreover, even when the ingot 1 moves a little, it can reduce that the cutting blade 2 contacts the base 6 and is damaged. In addition, a sufficient contact area between the ingot 1 and the pedestal 6 can be secured, and the ingot 1 can be prevented from shifting due to stress generated during cutting, and stable and reliable cutting is realized. The

  Further, the height D of the plurality of bases 6 including the adhesive layer 8 illustrated in FIG. 4A is preferably 5 mm or more and 50 mm or less. The height D of the pedestal 6 is the distance between the upper surface of the pedestal 6 and the upper surface of the plate 7, and is the height D from the base surface of the gap between the plurality of pedestals 6 to the upper surface of the pedestal 6. By setting it as the said range, it can reduce that the cutting blade 2 cut | disconnects all the contact members 4, and the cutting blade 2 contacts the plate 7, and is damaged. In addition, a sufficient contact area between the ingot 1 and the pedestal 6 can be ensured, and the shift of the ingot 1 due to stress generated during cutting can be reduced, thereby realizing stable cutting.

  Next, the contact member 4 will be described in detail. The abutting member 4 is disposed in a peripheral portion including the cutting portion 5 of the ingot 1 located in the gap between the plurality of pedestals 6 when FIG. 1 is viewed from above. The contact member 4 preferably has a hardness equal to or lower than that of the workpiece. For example, since the Mohs hardness of the semiconductor silicon ingot 1 is 7, a material having a Mohs hardness lower than that of the ingot 1 is preferable so that the contact member 4 does not damage the blade 2b. The abutting member 4 may be composed of only an adhesive layer 8 made of an adhesive, for example. By using only the adhesive as the contact member 4, the removal of the contact member 4 after the end of the cutting may be performed by removing the adhesive, thereby improving workability. The abutting member 4 may be made of, for example, a resin such as rubber having a Mohs hardness of 4 or less, a silicon having a Mohs hardness of 7, or a glass having a Mohs hardness of 6. Further, as shown in FIG. 4B, these abutting members 4 may be fixed to the ingot 1 via the adhesive layer 8. By using the member described above as the abutting member 4, the ingot 1 can be cut without reducing the number of times the cutting blade 2 is used. At this time, the adhesive used may be the same material as the adhesive used for fixing the ingot 1 to the base 1 or may be a different material.

  The width T of the contact member 4 in the vertical direction with respect to the longitudinal direction of the cutting blade 2 is preferably 5 mm or more and not more than the width W of the gap of the pedestal 6. By setting the width T of the abutting member 4 to 5 mm or more, the cut portion 5 on the lower surface 1d of the ingot 1 is reinforced, and the occurrence of cracks and chips at the end of cutting of the ingot 1 is reduced.

  The thickness of the abutting member 4 is preferably 40% or more of the height D of the pedestal 6 and not more than the height D of the pedestal 6. By setting it as the said range, the stress which tends to concentrate on the cutting | disconnection site | part 5 of the ingot 1 can fully be reduced, and generation | occurrence | production of the crack in the cutting | disconnection site | part 5 and a chip | tip can be reduced.

  As described above, according to the present embodiment, when the block 1a is cut out from the ingot 1, the base 6 can be reused without cutting, and the occurrence of cracks and chips at the end of cutting can be reduced. Due to the cutting load of the cutting blade 2, the ingot 1 being cut is stressed in the direction of falling inward, and particularly stress is concentrated on the cutting site 5 on the lower surface 1d of the ingot 1. However, in this embodiment, by providing the abutting member 4, stress that tends to concentrate on the cutting site 5 is reduced. Thereby, generation | occurrence | production of the crack in the surrounding part of the cutting | disconnection site | part 5 and a chip | tip can be reduced.

<Modification>
In addition, this invention is not limited to the above-mentioned embodiment, A various change, improvement, etc. are possible in the range which does not deviate from the summary of this invention.

  For example, the pedestal 6 may be provided in all regions except the peripheral portion of the cutting portion 5. Alternatively, it may be provided only in the region that becomes the block 1a of the ingot 1 and may not be provided on the lower surface 1d of the side surface portion 1b of the ingot 1 that becomes the end material. When the pedestal 6 is provided on the lower surface 1d of the side surface portion 1b of the ingot 1, the width W of the gap between the pedestals 6 tends to be small, and the cutting blade 2 may come into contact with the pedestal 6 and be damaged. By not providing the base 6 on the lower surface 1d of the side surface portion 1b of the ingot 1, the above problem can be reduced. In that case, you may provide the contact member 4 in the surrounding part of the cutting | disconnection site | part 5 adjacent to the side part 1b of the ingot 1, and generation | occurrence | production of the crack in the surrounding part of the cutting | disconnection part 5 can be reduced more.

  The abutting member 4 may be provided on the entire surface of the ingot 1. Further, the contact member 4 used at that time may be fixed by using a clamp, vacuum suction or the like, and an adhesive is provided on the contact surface with the ingot 1 side and the base 6 to form the adhesive layer 8. It may be fixed.

  Further, for example, as shown in FIG. 4C, the contact member 4 may be fixed to the lower surface 1 d of the ingot 1 and the upper surface of the plate 7 using an adhesive 8. The effect similar to the content mentioned above is acquired also by this aspect.

  Further, as shown in FIG. 5A, the thickness of the abutting member 4 is set to be less than the height D of the pedestal, and the abutting member 4 is fixed to the lower surface 1d of the ingot 1 with an adhesive layer 8 using an adhesive. Further, a gap may be provided between the abutting member 4 and the plate 7. The effect similar to the content mentioned above is acquired also by this aspect.

  Further, as shown in FIG. 5B, the contact member 4 may be formed only of the adhesive layer 8 using an adhesive, and a gap may be provided between the contact member 4 and the plate 7. The effect similar to the content mentioned above is acquired also by this aspect.

  Further, as shown in FIG. 5 (c), the contact member 4 is formed only by the adhesive layer 8 using an adhesive, and between the pedestals 6 disposed apart from each other, from the lower surface 1 d of the ingot 1 to the plate 7. The gap may be filled with an adhesive layer. The effect similar to the content mentioned above is acquired also by this aspect.

  Moreover, in this embodiment, although the solidification start surface of the ingot 1 was provided on the base 6 as the lower surface 1d, the side part 1b of the ingot 1 may be provided on the base 6 to cut the ingot 1.

  Further, the abutting member 4 may be fixed by a fixing jig so as to be disposed at the cutting site 5 on the lower surface 1d of the ingot 1.

  An example embodying the above-described embodiment and a comparative example thereof will be described. The reference drawings are mainly based on FIG. 1 and are shown in FIGS. 7A and 7B in the embodiment, and FIGS. 8A and 8B in the comparative example. For the band saw, a cutting blade using stainless steel for the blade 2b and diamond for the blade portion 2a was used.

  The cutting conditions of the silicon ingot as the workpiece were such that the blade rotation speed during cutting was 600 m / min, and the blade descending speed was 5 mm / min.

  Moreover, stainless steel was adopted for the pedestal 6, the distance between the pedestals was 40 mm, and the height of the pedestal was 30 mm.

<Example>
The contact member 4 is made of silicon. The width of the abutting member 4 was 20 mm, and the height of the abutting member 4 was 30 mm. The abutting member 4 and the base 6 were simultaneously bonded to the lower surface of the ingot 1 under the same conditions. That is, an epoxy resin as a main agent and a polyamide resin as a hardener are applied on the abutting member 4 and the pedestal 6, and a curable adhesive containing a main agent: curing agent in a mass ratio of 1.5: 1 is applied. The ingot 1 was disposed on the abutting member 4 and the base 6. The ingot 1 was placed and heated from below the pedestal 6, and pressure was applied from the top of the ingot 1 to bond them.

  As shown in FIGS. 7A and 7B, the abutting member 4 is provided in a region including the cut portion on the lower surface 1 d of the ingot 1. Then, as shown in FIG. 9, the ingot 1 is first cut in the order of cutting points A1, A2, A3, A4, and A5 indicated by alternate long and short dashed lines, and then cut portions B1, B2, B3, B4, and B5 indicated by alternate long and short dashed lines. Cut in order. This cut out 16 blocks. FIGS. 7A and 7B show a state where the cut portion A2 is cut after being cut at the cut portion A1.

<Comparative example>
As shown in FIGS. 8A and 8B, without providing a contact member around the cutting portion of the ingot 1, the cutting points A1, A2, A3, A4, and A5 are similar to the procedure shown in FIG. After cutting in order, the ingot 1 was then cut in the order of cut points B1, B2, B3, B4, and B5, and 16 blocks were cut out.

<Cutting defect rate>
Next, the ingot 1 was cut under the conditions of the example and the comparative example, and the ingot 1 was arranged on the pedestal 6 so that the lower surface 1d became a solidification start surface. Then, the occurrence rate of cracks and chips at the cut portion of the lower surface 1d of the ingot 1 when 100 ingots 1 were cut was obtained. The occurrence rate is the ratio of the number of blocks in which cracks and chips occur in 1600 blocks.

  As a result, the defect rate of cracks and chips of the ingot 1 generated at the cutting portion of the lower surface 1d of the ingot 1 at the end of cutting of the ingot 1 in the example was reduced by about 60% compared to the comparative example.

  This is because the concentration of stress is reduced by providing the contact member 4 around the cutting portion of the lower surface 1d of the ingot 1 at the end of cutting of the ingot 1, so that the occurrence rate of cracks and chips of the ingot 1 is reduced. It is guessed.

DESCRIPTION OF SYMBOLS 1: Ingot 1a: Block 1b: Side part 1c: Upper surface 1d: Lower surface 2: Cutting blade 2a: Blade part 2b: Blade 3: Pulley 4: Contact member 5: Cutting part 6: Base 7: Plate 8: Adhesive layer (adhesion) Agent)
S: Band saw

Claims (5)

A cutting method for a workpiece, which has a machining step of putting a cutting blade traveling on the workpiece on the upper surface of the workpiece at the start of cutting and extracting the cutting blade from the lower surface of the workpiece at the end of cutting. There,
In the processing step, a part of the workpiece excluding the cutting site on the lower surface is placed on a plurality of pedestals arranged apart from each other, and the cutting site is positioned between two adjacent pedestals. And cutting the workpiece with the cutting blade in a state where the patch is disposed in a region including the cutting site on the lower surface of the workpiece.   The workpiece cutting method according to claim 1, wherein the height of the plurality of pedestals is equal to or higher than the height of the abutting member.   The workpiece cutting method according to claim 1, wherein the hardness of the contact member is equal to or less than the hardness of the workpiece.   The method for cutting a workpiece according to any one of claims 1 to 3, wherein an adhesive layer is interposed between the contact member and the lower surface of the workpiece.   The method for cutting a workpiece according to claim 1, wherein the contact member is an adhesive.

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