JP2010194706A - Method of manufacturing substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a substrate improved in thickness accuracy of the substrate. <P>SOLUTION: This method includes processes for: preparing a block 1, a wire 3 for cutting the block 1 in a lower part of the block 1 and a dip tank 6 having machining liquid 11 up to a position not in contact with the wire 3 in a lower part of the wire 3; advancing a lower surface of the block 1 to the traveling wire 3 and starting cutting of the block 1; and cutting the block 1, while dipping the cut region of the block 1 in the machining liquid 11. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a substrate such as a semiconductor substrate.

  Conventionally, when manufacturing a semiconductor substrate including a solar cell element, etc., an ingot is cut into a predetermined size into a block shape, and after the block is bonded to a slice base with an adhesive, a wire saw device or the like is used. The substrate was manufactured by cutting into a plurality of sheets.

  As a slicing method in a wire saw, there is a method (fixed abrasive grain type) of cutting with an abrasive fixed wire in which abrasive particles are fixed to the wire from the beginning. In this method, a coolant liquid (working fluid) is stored in a dip tank, and a wire is run in the coolant liquid to supply coolant liquid to the wire and cut the block (for example, , See Patent Document 1).

JP 2006-181688 A

  However, in the conventional method, micro cracks are generated in the semiconductor substrate, and there is a risk that cracks, cracks, etc. occur in the element process of the solar cell element and the yield is lowered.

  Therefore, an object of the present invention is to provide a method for manufacturing a substrate that reduces the occurrence of microcracks and improves the yield.

  The method for manufacturing a substrate according to the present invention includes a step of preparing a block, a wire for cutting the block, and a processing liquid, a step of starting cutting of the block by the wire, and the cutting of the block. And further cutting the block while immersing at least a part of the region in the processing liquid.

  According to the present invention, problems such as wire breakage and machinability can be reduced by the above-described steps. In particular, when the machining fluid is a coolant, the block cutting region and the wire can be sufficiently cooled. For this reason, generation | occurrence | production of a microcrack is reduced and the yield fall by generation | occurrence | production of the crack in the element process of a solar cell element, a crack, etc. does not arise easily.

It is a perspective view showing typically one embodiment of a wire saw device in a manufacturing method of a substrate concerning the present invention. (A) is sectional drawing which shows typically one Embodiment of the wire saw apparatus in the manufacturing method of the board | substrate which concerns on this invention, (b) is the fragmentary sectional view seen from the X direction of (a).

  Hereinafter, a substrate manufacturing method according to an embodiment of the present invention will be described in detail with reference to the drawings.

  The substrate manufacturing method of the present embodiment includes a step of preparing a block, a wire for cutting the block at the lower portion of the block, and a dip tank having a processing liquid up to a position not in contact with the wire at the lower portion of the wire, The process includes a step of proceeding toward the wire running on the lower surface of the block and starting the cutting of the block, and a step of cutting the block while immersing at least a part of the cut region of the block in the processing liquid.

  The block is machined by cutting the end of the ingot. Such an ingot is made of, for example, single crystal silicon or polycrystalline silicon. For example, when a single crystal silicon ingot is used, since the single crystal silicon ingot has a cylindrical shape, silicon having a substantially rectangular cross section (including a square shape) is obtained by cutting four end portions in the height direction. You can get a block. In addition, what has a corner | angular part in circular shape in the said cross-sectional shape shall also be considered as a rectangle.

  The polycrystalline silicon ingot is, for example, a substantially rectangular parallelepiped, and has a size that allows a plurality of silicon blocks to be taken out. In such a case, the silicon block has a rectangular cross section (including a square shape), and is formed in a rectangular parallelepiped of, for example, 156 mm × 156 mm × 300 mm. In addition, what the corner | angular part was chamfered in the said cross-sectional shape shall be considered as a rectangle.

  As shown in FIG. 1, the traveling wire 3 and the square block 1 fixed to the slice base 2 are pressed against each other, and the block 1 is cut by the wire 3 to manufacture a substrate.

  The block 1 is bonded to the slice base 2 made of a material such as a carbon material, glass or resin by an adhesive or the like. The adhesive consists of an adhesive such as a thermosetting two-component epoxy-based, acrylic-based or acrylate-based resin, or wax. After slicing the substrate, the substrate can be easily peeled off from the slice base 2. An adhesive whose adhesive strength is reduced by raising the temperature is used. One or a plurality of blocks 1 bonded to the slice base 2 are arranged in the apparatus by the work holder 10.

  The wire 3 is supplied from the supply reel 7 and taken up on the take-up reel 8. The wire 3 is wound around a plurality of main rollers 5 between the supply reel 7 and the take-up reel 8 and is stretched between the main rollers 5. The wire 3 is made of, for example, a piano wire whose main component is iron or an iron alloy, and has a wire diameter of 80 μm to 180 μm, more preferably 120 μm or less. In the present embodiment, the wire 3 is an abrasive fixed wire in which abrasive grains made of diamond or silicon carbide are fixed around the wire by plating with nickel, copper, or chromium. In this case, the average grain size of the abrasive grains is preferably 5 μm or more and 30 μm or less.

  The dip tank 6 includes a processing liquid in which the cut area of the block 1 is immersed. The dip tank 6 is provided for the purpose of recovering chips and machining fluid of the block 1 generated during cutting. Although the surface tension is easily received between the substrate portions, the influence of the surface tension between the substrates is alleviated by immersing the cut region of the block 1 in the processing liquid, and problems such as disconnection and machinability can be reduced. .

  When such a working fluid is a coolant, the coolant is made of a water-soluble solvent such as glycol, and is supplied to the plurality of wires 3 from the openings of the supply nozzle 4 having a plurality of openings. The The supply flow rate of the coolant liquid supplied to the supply nozzle 4 is appropriately set according to the size and number of blocks. Further, the coolant liquid may be circulated and used, and the abrasive grains and chips contained in the coolant liquid are removed at that time.

  The main roller 5 includes a first main roller 5a and a second main roller 5b arranged below the block 1. The main roller 5 is made of, for example, urethane rubber such as ester, ether or urea, or resin such as neurite, and has a diameter of 150 to 500 mm and a length of about 200 to 1000 mm. . A large number of grooves for arranging the wires 3 supplied from the supply reel 7 at predetermined intervals are provided on the surface of the main roller 5. The thickness of the substrate is determined by the relationship between the interval between the grooves and the diameter of the wire 3.

  As another embodiment, a cutting fluid containing abrasive grains may be used as the processing fluid. Such a cutting fluid can be supplied, for example, by using a loose abrasive type wire saw device that cuts the block 1 by the lapping action of the wire 3. In this case, the wire 3 to be used is wound around the main roller 5, and for example, a piano wire mainly composed of iron or an iron alloy may be used, and the wire diameter is 80 μm to 180 μm, more preferably 120 μm or less. The cutting fluid is configured by mixing wrapping oil composed of abrasive grains such as silicon carbide, alumina, diamond, mineral oil, surfactant and dispersant. The cutting fluid is supplied to a plurality of wires 3 stretched from a supply nozzle 4 having a plurality of openings. As the average particle size of the abrasive grains, for example, those having a narrow particle size distribution of 5 μm to 20 μm are used. The supply flow rate of the cutting fluid supplied to the supply nozzle 4 is appropriately set depending on the size and number of blocks. Further, the cutting fluid may be circulated and used, and new abrasive grains may be additionally supplied at that time.

  Below, the slicing method using the wire saw apparatus in a fixed abrasive grain type is demonstrated. The wire 3 is supplied from the supply reel 7 and guided to the main roller 5 by the guide roller 9, and the wire 3 is wound around the main roller 5 and arranged at a predetermined interval. The wire 3 can be run in the longitudinal direction of the wire 3 by rotating the main roller 5 at a predetermined rotation speed. Further, the wire 3 is reciprocated by changing the rotation direction of the main roller 5. At this time, the length for supplying the wire 3 from the supply reel 7 is longer than the length for supplying the wire 3 from the wire take-up reel 8, and the new line is supplied to the main roller 5.

  The block 1 is cut by lowering the block 1 and relatively pressing the block 1 against the wire 3 while supplying the machining fluid toward the wire 3 running at high speed. The block 1 is divided into a plurality of substrates having a thickness of 200 μm or less, for example. At this time, the tension of the wire 3, the speed at which the wire 3 travels (travel speed), and the speed at which the block is lowered (feed speed) are appropriately controlled. For example, the maximum traveling speed of the wire 13 is set to 500 m / min or more and 1000 m / min or less, and the maximum feed speed is set to 350 μm / min or more and 1100 μm / min or less.

  In the slicing method using the loose abrasive type wire saw apparatus, a cutting fluid is used as a working fluid instead of a coolant. Alternatively, the wire 3 may travel in one direction without reciprocating.

  In the substrate manufacturing method according to the present embodiment, as shown in FIG. 2, the processing liquid 11 in which at least a part of the cut area of the block 1 (the area after the wire 3 passes) is filled in the dip tank 6 is used. The block 1 is cut while being immersed. At this time, the liquid level of the machining liquid 11 in the dip tank 6 is in a position where it does not come into contact with the traveling wire 3. In particular, the distance between the liquid surface of the machining liquid 11 and the wire 3 is 3 cm or more, more preferably 5 cm or more, so that the machining liquid can be cut without being scattered even when the wire 3 runs at a high speed. it can. Since the distance between the processed portions (hereinafter referred to as substrate portions) 1a of the cut block is narrow, the processing liquid 11 soaks up due to the capillary phenomenon, and the influence of the surface tension between the substrate portions 1a is alleviated, and the wire breakage, cutting ability, etc. Problems can be reduced. When the machining liquid 11 is a coolant liquid, the soaked machining liquid 11 is caught in the wire 3 that travels at high speed in the closed space of the cutting area, and sufficiently cools the cutting area of the block 1 and the wire 3. Can do. Moreover, since the wire 3 is not run in the liquid of the machining liquid 11, the wire 3 is not affected by the turbulent flow of the machining liquid and the wire 3 is not shaken. For this reason, generation | occurrence | production of a microcrack can be reduced.

  In addition, after the block 1 is immersed in the machining liquid 11 in the dip tank 6, the supply amount of the machining liquid 11 supplied from the supply nozzle may be adjusted as appropriate. In particular, when the machining fluid 11 is a cutting fluid, the machinability changes, so that the machining fluid 11 is appropriately adjusted to be constant.

  Further, after cutting a height of 1/3 or more, more preferably half or more of the block 1 having a substrate size of 15 cm or more obtained after cutting, at least a part of the cut region of the block 1 is processed liquid 11. The height of the processing liquid 11 in the dip tank 6 is adjusted so as to be immersed in the dip tank. After the height of 1/3 or more, more preferably half or more, of the block 1 is cut, the substrate is particularly susceptible to surface tension. When the substrate is thinned, it is more susceptible to the influence of surface tension between the substrate portions 1a, and the end portions on the cutting start side of the block are easily brought into contact with each other. In the fixed abrasive type wire saw device, a load is applied to the wire 3 being cut at such a contact portion, and the wire 3 is easily broken. Further, in the loose abrasive type wire saw device, the cutting fluid is hardly discharged at such a contact portion, so that the amount of the cutting fluid existing between the substrate portions 1a increases, and the machinability is likely to increase. . However, by immersing the cut area on the cutting start side of the block 1 in the processing liquid 11, the influence of the surface tension between the substrates is alleviated, and problems such as disconnection and machinability can be reduced. In addition, since the cutting can be performed stably as compared with the case of immersing in the processing liquid 11 from the start of cutting, the surface roughness and undulation of the substrate can be reduced.

  Further, the depth at which the block 1 is immersed in the machining liquid 11 can be adjusted by changing the height of the liquid level of the machining liquid 11 in the step of immersing the block in the machining liquid, and the liquid level is in contact with the wire 3. Can be adjusted to not. The height of the liquid level may be adjusted by adjusting the supply amount and discharge amount of the machining liquid 11. In addition to supplying the machining liquid 11 to the supply nozzle 4, a supply port to the dip tank 6 may be provided separately and supplied from this supply port.

  In addition, the dip tank 6 is previously filled with the processing liquid until the height at which the end of the block 1 at the beginning of cutting is immersed in the processing liquid after the height of 1/3 or more, more preferably more than half of the block 1 is cut. You may keep it. Thereby, the influence of surface tension can be relieved, without providing the mechanism which adjusts a process liquid separately.

  Moreover, you may make it irradiate the process liquid 11 in the dip tank 6 with an ultrasonic wave. Thereby, the influence of the surface tension between the board | substrate parts 1a is relieve | moderated, and problems, such as a disconnection and machinability, can further be reduced.

  Then, simultaneously with slicing the block 1, the slice base 2 is also cut by about 2 to 5 mm, and the wire 3 is pulled out from the block. At this time, the substrate can be taken out while being adhered to the slice base 2. At this time, the wire 3 is pulled out from the block 1 while immersing at least a part of the block 1, in particular, the end of the block 1 on the cutting start side in the processing liquid 11 in the dip tank 6. By immersing the block 1 in the processing liquid 11, the influence of the surface tension between the substrates is alleviated, and it is possible to reduce the narrowing between the end portions on the cutting start side of the block 1. For this reason, when the wire 3 is pulled out, it is possible to reduce damage to the substrate due to the abrasive grains attached to the wire 3.

  In particular, in the fixed abrasive type, when the wire 3 is pulled out, the wire 3 is pulled while running. In the fixed abrasive type, since the abrasive grains are directly bonded and fixed to the wire 3, the substrate is more easily damaged than the free abrasive type, but by moving the wire 3, the contact resistance between the wire 3 and the substrate is small. Therefore, it is possible to reduce damage to the substrate by the abrasive grains. At this time, when the traveling speed when the wire 3 is pulled out is slower than the traveling speed during cutting, the damage to the substrate can be further reduced. The traveling speed of the wire 3 is set to 10 m / min or more and 100 m / min or less. Further, the feed speed when the wire 3 is pulled out is set to 1 mm / min or more and 10 mm / min or less.

  Then, the substrate taken out is put into the next cleaning step while being bonded to the slice base 2.

  In the cleaning process, an alkaline liquid or a neutral liquid is used as a cleaning liquid, and water-soluble coolant, oil, and dirt adhering to the substrate are cleaned, and then the detergent is washed away with water. Then, the substrate surface is completely dried by hot air or air and peeled off from the slice base 2 to complete the substrate 1a.

  Thus, since the generation | occurrence | production of the microcrack in a board | substrate can reduce the board | substrate formed with the said manufacturing method, generation | occurrence | production of a crack, a crack, etc. can be suppressed in the element process of a solar cell element, and is high. A solar cell element can be manufactured with a yield.

  In addition, this invention is not limited to the said embodiment, Many corrections and changes can be added within the scope of the present invention.

  For example, the slicing process may be performed as it is without cutting the ingot 1.

  Examples according to the present invention will be described below. First, an epoxy adhesive was applied to a slice base made of a glass plate. Next, a rectangular parallelepiped polycrystalline silicon block of 156 mm × 156 mm × 300 mm was placed on the slice base, and the adhesive was cured. Then, a silicon block bonded to two slice bases was placed in a wire saw device, and diamond abrasive grains were fixed by Ni plating (wire diameter = 120 μm, abrasive grain diameter = 14 μm, average diameter D = 148 μm) The block bonded to the slice base was sliced while traveling in both directions, and a 156 square silicon substrate having an average thickness of 200 μm was produced.

  At this time, after filling the dip tank with the processing liquid and cutting 1/3 of the block and half the height, conditions 1 and 2 where the cut end of the block 1 is immersed in the processing liquid for the first time, and at the start of cutting In the condition 3 (comparative example) where the block is immersed in the machining fluid and the condition 4 (comparative example) where the block is cut without filling the dip tank with the machining fluid, the wire breakage rate and the slice defect when slicing Rate and fracture strength in a 4-point bending test of the substrate. In the 4-point bending test of the substrate, the distance between the external fulcrums is 130 mm, the distance between the internal fulcrums is 80 mm, and the maximum bending stress when the obtained silicon substrate is broken by applying a load is obtained. The bending strength was calculated according to JIS R 1601 (2008).

  Defect items related to the defect rate of slices include the presence or absence of slice marks, the presence or absence of irregularities, and the presence or absence of undulations. The defect rate was calculated from the number of substrates. The results are shown in Table 1.

  As shown in Table 1, from the results of conditions 1 to 4, in conditions 1 and 2, all of the wire breakage rate, slice failure rate, and substrate break strength are compared to conditions 3 and 4 which are comparative examples. Greatly improved.

1: Block 1a: Substrate 3: Wire 6: Dip tank 11: Processing fluid (coolant fluid or cutting fluid)

Claims (7)

Preparing a block, a wire for cutting the block, and a working fluid;
Starting the cutting of the block with the wire;
Further cutting the block while immersing at least a part of the cut region of the block in the working fluid;
The manufacturing method of the board | substrate which has this.   The substrate manufacturing method according to claim 1, wherein at least a part of the cut region of the block is immersed in the processing liquid after half of the block is cut in the cutting direction of the block.   The method for manufacturing a substrate according to claim 1, wherein in the step of immersing the block in the processing liquid, the height of the liquid level of the processing liquid is changed. Preparing a block, a wire for cutting the block, and a working fluid;
Starting the cutting of the block with the wire;
After cutting the block, the step of pulling out the wire from the block while immersing at least a part of the block in the processing liquid;
The manufacturing method of the board | substrate which has this.   The method of manufacturing a substrate according to claim 4, wherein in the step of pulling out the wire, the wire is pulled out while running.   6. The method of manufacturing a substrate according to claim 5, wherein in the step of pulling out the wire, a traveling speed of the wire when the wire is pulled out is slower than a traveling speed of the wire being cut.   The substrate manufacturing method according to any one of claims 4 to 6, wherein at least a part of the cut region of the block is immersed in the processing liquid during the cutting of the block.

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