JP2009279746A - Method of manufacturing substrate and solar cell element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a substrate in which thickness accuracy of the substrate is improved. <P>SOLUTION: The method includes a step of preparing a block 1 having a flat surface, a step of advancing a wire 3 in the flat surface 1s of the block 1 and cutting a central part of the block 1 with the wire 3 running at a first speed, and a step of cutting the block 1 cut at the first speed with the wire 3 running at a second speed slower than the first speed in succession. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a substrate and a solar cell element.

  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.

  In order to obtain a substrate with good thickness accuracy, for example, Japanese Patent Laid-Open No. 2004-133830 discloses a workpiece feed rate (feed rate) at the initial cutting as 1. A method of 5 to 4 times is described.

Note that, as a management of the substrate thickness, it has been common to manage the substrate thickness by measuring several points 10 mm or more inside from the edge of the substrate.
JP-A-6-155278

  In recent years, a substrate used for a solar cell has been reduced in thickness, and a wire having a small wire diameter is used in order to reduce kerf loss (cutting allowance). At this time, the block has a problem that the thickness varies at the end portion on the side where the cutting is completed as compared with the central portion, and the block is easily cut. In particular, when the thickness of the end portion of the substrate is different from the average thickness of the entire substrate, there is a problem that cracks, cracks, and the like occur in the element process of the solar cell element and the yield decreases.

  The present invention has been made in view of such problems, and an object thereof is to provide a method for manufacturing a substrate with improved thickness accuracy.

  The method of manufacturing a substrate of the present invention includes a step of preparing a block having a first surface and a second surface on the first back side bonded to a base, and a wire is advanced to the first surface. Starting the cutting of the block, cutting the central portion of the block with a wire running at a first speed, cutting the block at the first speed, and then cutting the block from the central portion. Cutting the block on the second surface side with a wire traveling at a second speed slower than the first speed.

  The solar cell element of this invention has the board | substrate which consists of a silicon | silicone manufactured by the above-mentioned manufacturing method, and the semiconductor junction area | region and electrode which were formed in the said board | substrate.

  According to the present invention, a substrate with reduced thickness variation can be manufactured by the above-described steps. In particular, when the thickness of the end portion (cutting end portion) of the substrate is substantially the same as the average thickness of the entire substrate and the substrate is used as a solar cell element, the yield decreases due to the occurrence of cracks or cracks in the element process of the solar cell element. Is unlikely to occur.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
The substrate manufacturing method of the present embodiment includes a step of preparing a block 1 having a first surface 1 s and a second surface 1 t on the back side of the first surface 1 s bonded to the base 2, After the wire is advanced to the surface 1s and the cutting of the block 1 is started, the center portion of the block 1 is cut by the wire 3 traveling at the first speed, and the block 1 is cut at the first speed. Cutting the block on the second surface 1t side from the central portion with a wire 3 that travels at a second speed slower than the first speed. Here, in this embodiment, the traveling speed (first speed) of the wire that cuts the central portion of the block 1, the supply flow rate of the cutting fluid, and the feed speed are the speed and flow rate when cutting in a steady state. When the length from the first surface 1s to the second surface 1t is a, the average speed and the average flow rate when cutting a range of 1 / 3a or more and less than 2 / 3a from the first surface 1s. Means. The traveling speed (second speed) of the wire that cuts the second surface 1t side of the block cut at the first speed, the supply flow rate of the cutting fluid, and the feed speed are 2 / 3a or more and 17 / 20a. It shall mean the minimum speed and the minimum flow rate in the range below.

  Block 1 is formed 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, the single crystal silicon ingot has a cylindrical shape, and therefore, by cutting four end portions in the height direction, the cross-sectional shape is substantially rectangular (including a square). A silicon block can be obtained. 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 generally a substantially rectangular parallelepiped and has a size that allows a plurality of silicon blocks to be taken out. The silicon block has a rectangular cross section (including a square), for example, 156 × 156. A 300 mm rectangular parallelepiped is formed. In addition, what the corner | angular part was chamfered in the said cross-sectional shape shall be considered as a rectangle.

  FIG. 1 is a perspective view showing a wire saw apparatus used in the substrate manufacturing method according to the present embodiment. In the configuration 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 a slice base 2 made of a material such as a carbon material, glass, resin or the like by an adhesive or the like. The adhesive is made of an adhesive such as a thermosetting two-component epoxy type, an acrylic type, a reacrate type, or a wax, and the temperature is raised so that the substrate 1a can be easily separated from the slice base 2 after slicing. Thus, an adhesive whose adhesive strength is reduced is used.

  Then, one or a plurality of blocks 1 bonded to the slice base 2 are arranged in the apparatus by a work holder. In FIG. 1, two are arranged.

  In the present embodiment, a loose abrasive type wire saw device that cuts the block 1 by the lapping action of the wire 3 by supplying a cutting fluid containing abrasive grains is used.

  The wire 3 of the wire saw device 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 100 μm to 180 μm, more preferably 140 μm or less.

  The cutting fluid is configured by mixing lapping oil composed of abrasive grains such as silicon carbide, alumina, and diamond, mineral oil, a surfactant and a dispersant, and stretched to a plurality of nozzles from a supply nozzle 4 having a plurality of openings. Cutting fluid is supplied to the formed wire 3. 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.

  The main roller 5 is made of, for example, a resin such as ester-based, ether-based, urea-based urethane rubber, or neurite, and has a diameter of about 150 to 500 mm and a length of about 200 to 1000 mm. The surface of the main roller 5 is provided with a number of grooves for arranging the wires 3 supplied from the wire supply reel 7 at predetermined intervals. The thickness of the substrate is determined by the relationship between the interval between the grooves and the diameter of the wire 3.

  The dip tank 6 is provided below the wire 3 for the purpose of collecting block waste and cutting fluid generated during cutting.

Below, the slicing method of this embodiment using a wire saw apparatus is demonstrated.
(A) First, the wires 3 and the blocks 1 provided in a plurality of rows are prepared.
(A) Next, the wire 3 that travels against the first surface 1s of the block 1 is advanced, and the cutting of the block 1 is started.
(C) Thereafter, the central portion of the block 1 is cut by the wire 3 traveling at the first speed.
(D) Then, the block 1 cut at the first speed is continuously cut by the wire 3 traveling at the second speed slower than the first speed.

The step (a) will be described.
The wires 3 are supplied from the wire supply reel 7 and are wound around the main roller 5 and arranged at predetermined intervals. When the main roller 5 is rotated at a predetermined rotation speed, the wire 3 can travel in the longitudinal direction of the wire 3. When the wire 3 is made to travel in one direction without reciprocating, the load on the motor that drives the main shaft that rotates the wire 3 can be reduced and the life of the apparatus can be extended.

The steps (a) to (d) will be described.
The cutting of the block 1 is performed by lowering the block 1 while supplying the cutting fluid from the supply nozzle 4 provided in the vicinity of the cutting portion toward the traveling wire 3, so that the wire 3 has the first block 1. This is done by relatively pressing the surface 1s. The block 1 is divided into a plurality of substrates 1a having a thickness of 200 μm or less, for example. At this time, the tension of the wire 3, the wire 3
The speed at which the vehicle travels (travel speed) and the speed at which the block is lowered (feed speed) are appropriately controlled.

  In this embodiment, since the cutting fluid supplied to the wire 3 is supplied to the block in one direction by running the wire 3 in one direction using a loose abrasive type wire saw device, the cutting fluid is a substrate. Slicing can be performed in a stable manner, reducing the thickness variation of the substrate 1a after slicing, and reducing the disconnection of the wire 3.

  At the same time as slicing the block 1, the slice base 2 is also cut by about 2 to 5 mm, and the substrate 1 a is put into the next cleaning step while being bonded to the slice base 2.

In the washing process, sludge and the like adhering at the time of slicing are first removed by washing with kerosene. After that, wipe the oil with an alkaline detergent, and then wash away the detergent with water. Then, the surface of the substrate 1a is completely dried by hot air or air and peeled off from the slice base 2 to complete the substrate 1a.

  When the ingot 1 is made of silicon, the substrate 1a obtained by the above method can be used as a solar cell element by forming a semiconductor junction region and an electrode.

  In the manufacturing method of the substrate 1a in the present embodiment, the traveling speed of the wire 3 cuts the second surface 1t side of the block 1 rather than the speed (first speed) at the time of cutting the central portion of the block 1. The speed at the time (that is, the speed at the time of cutting in the second half after the cutting of the central portion, the second speed) is slower. Here, when the block is cut, generally, after the cutting of the central portion of the block, as shown in FIG. In particular, when the substrates are thinned, they are easily affected by surface tension between the substrates, and an attractive force is generated between the end portions on the cutting start side of the block and is easily contacted. In such a contact portion, the cutting fluid is difficult to be discharged, so that the amount of the cutting fluid existing between the substrates increases, and the machinability is likely to increase. In addition, the wire 3 tends to move closer to the one substrate 1a due to the influence of the twist of the wire 3, etc. Therefore, the cutting amount of the wire 3 with respect to the two substrates 1a sandwiching the wire 3 tends to be larger than the one substrate 1a. From these factors, the thickness of the substrate 1a tends to vary at the end portion on the side where the cutting is completed. However, by slowing the traveling speed of the wire 3 in the present embodiment, the length of the wire passing per unit time is shortened, cutting performance can be reduced, and the influence of twisting and the like can be reduced. In the portion, the thickness of the substrate is less likely to vary, and the thickness of the substrate end on the side where cutting is completed and the average thickness of the entire substrate can be managed to be substantially the same. The first speed of such a wire 3 is, for example, 600 m / min or more and 1000 m / min or less, and the second speed is 400 m / min or more and less than 600 m / min. By setting it as such a speed range, it is easy to slice without a wire breaking.

  The thickness of the substrate 1a can be measured using a contact-type or non-contact-type thickness measuring device. In the present embodiment, the total average thickness of the substrate 1a is measured by measuring the thickness of a total of nine points consisting of eight points B each 30 mm away from the center A point shown in FIG. It was. The thickness at the end of cutting was measured at the point C 30 mm away from the upper edge of the substrate and 5 mm away from the side edge. Further, in the confirmation of burrs (protrusions formed at the end of the substrate), the thickness of point D, which was 2 mm away from the upper end of the substrate (end of block cutting), was measured.

  In addition, by changing the traveling speed of the wire 3 and making the supply flow rate of the cutting fluid smaller at the time of the latter half cutting than at the time of cutting the central part, the thickness of the cutting end part (cutting end part) can be reduced to the substrate. It is possible to manage the thickness to be substantially the same as the overall average thickness, and to suppress variations in the thickness of the entire substrate. Regarding the relationship of the cutting fluid supply flow rate in such a cutting process, for example, the supply flow rate at the latter half of the cutting is 70% or more and 90% or less of the supply flow rate at the cutting of the central portion. By setting it as such a range, it is easy to slice with uniform thickness, without a wire breaking.

  The supply flow rate of the cutting fluid varies depending on the size and number of blocks. For example, when slicing two blocks 1 having a length of 300 mm, 80 L / min or more and 150 L / min when cutting the central portion of the block 1. Used in the following.

  Furthermore, while changing the traveling speed of the wire 3, the feed speed at which the block 1 is moved toward the wire 3 is also slowed at the time of the latter half of the cutting of the central portion, so that the wire 3 is disconnected, etc. Can be reduced, and variations in the thickness of the entire substrate can be suppressed. Regarding the relationship of the feed speed of the block 1 in such a cutting process, for example, the feed speed at the latter half of cutting is 70% or more and 90% or less of the feed speed at the time of cutting the central portion. Although the feed speed of the block differs depending on the size and number of the blocks, for example, when slicing two blocks of 300 mm in length, they are used at 220 μm / min or more and 500 μm / min or less when cutting the central portion. By setting it as such a range, it is easy to slice with uniform thickness, without a wire breaking.

  Also, as shown in FIGS. 4 (a) and 4 (b), the wire traveling speed is decreased stepwise or continuously as it proceeds from the central portion of the block 1 to the second surface side. Moreover, the burden concerning the wire 3 can be reduced and the problem that the wire 3 is disconnected can be reduced.

  Further, in accordance with the change in the traveling speed of the wire 3, the cutting fluid supply flow rate and / or the feed speed of the block 1 is gradually or gradually increased from the time of cutting the central portion of the block 1 toward the second surface 1t. By continuously reducing the thickness, variations in the thickness of the entire substrate can be suppressed. Here, stepwise means that the speed or flow rate is maintained at a certain value for a certain period of time and then changed, and continuous means that the speed or flow rate is maintained at a certain value for a certain period of time without change. I mean.

  Further, the burr can be reduced by increasing the supply flow rate of the cutting fluid when cutting the second surface 1t, which is the end of cutting of the block 1, as compared to when cutting the second half.

  Furthermore, the burr formation can be further reduced by making the traveling speed of the wire 3 smaller than the second speed at the time of cutting the second surface 1t which is the end of cutting of the block 1. Since the cutting end portion of the block 1 is bonded to the slice base 2, the machinability is different at the interface, so burr is generally easily formed. However, the cutting fluid is increased to increase the machinability. However, it is considered that the formation of burrs can be reduced by reducing the traveling speed of the wire 3 and carefully slicing. The traveling speed when cutting the second surface 1t is, for example, 66% or more and 85% or less of the second speed, so that the formation of burrs can be easily reduced.

  Further, as the timing for increasing the supply flow rate of the cutting fluid, it is preferable to cut the block 1 in the range of 17 / 20a to 19 / 20a, and the supply flow rate when cutting the second surface 1t of the block 1 is For example, it may be equivalent to that at the time of cutting the central portion. Moreover, as a timing which makes the traveling speed of the wire 3 small, the time of cutting | disconnection of the range of 17 / 20a or more and 19 / 20a or less of the block 1 is good.

  Further, as shown in FIG. 5A, the traveling speed of the wire 3 and the supply flow rate of the cutting fluid are in a steady state in the cutting process. In FIG. 5A, the timing at which the traveling speed of the wire 3 becomes slower is earlier than or the same as the timing at which the cutting fluid supply flow rate becomes smaller. That is, the depth (cutting position) X at which the block 1 is cut before the speed is reduced from the first speed of the wire 3 is the depth (cutting) at which the block 1 is cut before the cutting fluid supply flow rate decreases. Position) shallower than Y or the same. The first speed is 600 m / min or more and 1000 m / min or less, the second speed is 400 m / min or more and less than 600 m / min, and the supply flow rate during the latter half cutting is 70% or more and 90% of the supply flow rate when cutting the central portion. By making it below, the block 1 can be sliced without degrading the machinability and without placing a burden on the wire 3.

  Furthermore, as shown in FIG. 5B, the traveling speed of the wire 3 and the feed speed of the block 1 are in a steady state in the cutting process. In FIG. 5 (b), the timing at which the traveling speed of the wire 3 is delayed is earlier or the same as the timing at which the feed speed of the block 1 is decreased. That is, the depth (cutting position) X at which the block 1 is cut before the speed is reduced from the first speed of the wire 3 is the depth (cutting) at which the block 1 is cut before the feed speed of the block 1 is reduced. Position) shallower than Z or the same. The first speed is 600 m / min or more and 1000 m / min or less, the second speed is 400 m / min or more and less than 600 m / min, and the feed speed at the second half cutting is 70% or more and 90% of the feed speed at the center cutting. By making it below, the block 1 can be sliced without degrading the machinability and without placing a burden on the wire 3. Note that there is no consistency between the travel speed value and the feed speed value on the vertical axis of FIG. 5B, and the travel speed is actually much higher than the feed speed.

  Further, the depth (cutting position) Y at which the block 1 is cut before the supply flow rate of the cutting fluid becomes smaller than the depth (cutting position) Z at which the block 1 is cut before the feed speed of the block 1 is reduced. Make it shallower or the same. By controlling the slicing condition within the above range, the block 1 can be sliced without degrading the machinability and without placing a burden on the wire 3.

  Thus, since the substrate 1a formed by the above-described manufacturing method can manage the thickness of the end portion of the substrate, in the element process of the solar cell element, the generation of cracks and cracks is prevented, and the solar cell is produced with a high yield. An element can be manufactured.

(Second embodiment)
Next, the difference between the second embodiment and the first embodiment will be mainly described. In 2nd Embodiment, the fixed abrasive type wire saw apparatus cut | disconnected with the abrasive grain fixed wire which fixed the abrasive grain to the wire from the beginning is used.

  The substrate manufacturing method of the present embodiment includes a step of preparing a block 1 having a first surface 1 s and a second surface 1 t on the back side of the first surface 1 s bonded to the base 2, Advance the wire with the abrasive grains fixed to the surface 1 s, start cutting the block 1, cut the central portion of the block 1 with the wire 3 traveling at the first speed, and block at the first speed And cutting the second surface 1t of the block with a wire 3 that travels at a second speed that is slower than the first speed.

  The wire 3 of the wire saw device is wound around a main roller 5 and is made of, for example, a piano wire mainly composed of iron or an iron alloy, and has a wire diameter of 80 μm to 180 μm, more preferably 120 μm or less. In the wire 3, abrasive grains made of diamond or silicon carbide are fixed around the wire by plating with nickel, copper or chromium. The average grain size of the abrasive grains is preferably 5 μm or more and 30 μm or less.

  The supply nozzle 4 has a plurality of openings for discharging the coolant liquid. The coolant liquid is made of, for example, a water-soluble solvent such as glycol, and is supplied to the plurality of wires 3 through the openings of the supply nozzle 4 having a plurality of openings. 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. Moreover, you may use it, circulating a coolant liquid, and it uses it, removing the chips etc. which are contained in a coolant liquid in that case.

Below, the slicing method of this embodiment using a wire saw apparatus is demonstrated.
(A) First, the wires 3 and the blocks 1 provided in a plurality of rows are prepared.
(A) Next, the wire 3 that travels against the first surface 1s of the block 1 is advanced, and the cutting of the block 1 is started.
(C) Thereafter, the central portion of the block 1 is cut by the wire 3 traveling at the first speed.
(D) Then, the second surface 1t of the block 1 is continuously cut by the wire 3 traveling at a second speed slower than the first speed.

  In the present embodiment, the wire 3 is caused to travel bidirectionally using a fixed abrasive type wire saw device, so that the abrasive particles fixed to the wire 3 can be effectively used to improve the productivity. Become.

In the manufacturing method of the substrate 1a in the present embodiment, the traveling speed of the wire 3 is higher when the second surface 1t of the block 1 is cut than the speed (first speed) at the time of cutting the central portion of the block 1. The second speed is slower. As described above, when the block is cut, generally after the cutting of the central portion of the block, as shown in FIG. 6, the substrate is easily subjected to the surface tension force, and the surface of the substrate is made of abrasive grains. There is a high possibility of being hurt. However, by reducing the traveling speed of the wire 3 in the present embodiment, it is possible to reduce cracks generated at the end of the substrate on the side where cutting is completed. This is presumably because blurring or the like generated in the wire 3 is reduced by reducing the traveling speed of the wire 3. The wire 3 of the present embodiment travels in one direction at a steady speed, then decelerates and stops temporarily, accelerates in the reverse direction to reach a steady speed, then decelerates and stops, and travels in the opposite direction again. Do (round trip). For this reason, the traveling speed here means a steady speed. The first speed of such a wire 3 is, for example, 600 m / min or more and 1000 m / min or less, and the second speed is 300 m / min or more and less than 500 m / min. By setting it as such a speed range, generation | occurrence | production of a crack can be reduced and a slice can be performed, without a wire breaking. Moreover, as a timing which makes the traveling speed of the wire 3 small, the time of cutting | disconnection of the range of 17 / 20a or more and 39 / 40a or less of the block 1 is good.

  In addition to changing the traveling speed of the wire 3, the feed speed of the block 1 is also slower when the second surface 1t is cut than when the center portion is cut. And the occurrence of cracks can be reduced. The feed speed may be adjusted so that the feed speed is decreased when the traveling speed of the wire 3 is decreased and the feed speed is increased when the traveling speed is increased. Therefore, the feed speed when speed adjustment is performed means a steady speed. Regarding the relationship of the feed speed of the block 1 in such a cutting step, for example, the feed speed at the time of cutting the second surface is 50% or more and 90% or less of the feed speed at the time of cutting the central portion. Although the feed speed of the block varies depending on the size and number of blocks, for example, when slicing a block having a length of 300 mm, it is used at 350 μm / min or more and 1100 μm / min or less when the central portion is cut. By setting it as such a range, the disconnection of a wire can be reduced and generation | occurrence | production of a crack can be reduced and it can slice.

  Also, as shown in FIGS. 4 (a) and 4 (b), the wire traveling speed is decreased stepwise or continuously as it proceeds from the central portion of the block 1 to the second surface 1t side. Moreover, the burden concerning the wire 3 can be reduced and the problem that the wire 3 is disconnected can be reduced.

  Furthermore, the feed speed of the block 1 should be reduced stepwise or continuously as it advances from the time of cutting the central portion of the block 1 to the second surface 1t side in accordance with the change in the traveling speed of the wire 3. Therefore, variation in the thickness of the entire substrate can be suppressed. Here, “stepwise” refers to the case where the speed or flow rate is maintained at a certain value for a certain period of time and then changed, and “continuous” refers to the case where the speed is varied at a certain value for a certain period of time without changing it over time. Say.

  When manufacturing a solar cell element using the board | substrate 1a formed with the said manufacturing method, generation | occurrence | production of the crack etc. in a manufacturing process can be prevented and a solar cell element can be produced with a high 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.

Example 1
Examples will be described below.
First, an epoxy-based adhesive was applied to a slice base made of a glass plate, a rectangular parallelepiped polycrystalline silicon block of 156 mm × 156 mm × 300 mm was placed on the slice base, and the adhesive was cured. As shown in FIG. 1, a silicon block bonded to two slice bases is installed in a wire saw device, and a cutting fluid comprising silicon carbide abrasive grains (# 1200), mineral oil, a surfactant, and a dispersant is added. While supplying the wire (wire diameter 130 μm) running in one direction, the block adhered to the slice base was sliced to produce a silicon substrate having an average thickness of 200 μm. Slicing conditions at the time of cutting the central part are 700 m / min for the first traveling speed of the wire, 120 L / min for the supply flow rate of the cutting fluid, and slicing conditions for the second half of the feed speed of the silicon block are 270 μm / min. The second traveling speed of the wire is set to eight conditions (No. 1 to No. 8) of 300 m / min, 350 m / min, 400 m / min, 450 m / min, 500 m / min, 550 m / min, 600 m / min, and 650 m / min. ), The cutting fluid supply flow rate was 120 L / min, and the feed rate of the silicon block was 220 μm / min. In addition, each value was continuously made small from the value of a center part so that it might become the conditions at the time of the cutting | disconnection on the 2nd surface side when it cuts 120 mm from the cutting start edge part.

  The slicing conditions of the comparative example were constant at a wire traveling speed of 700 m / min, a cutting fluid supply flow rate of 120 L / min, and a silicon block feed speed of 270 μm / min.

  The average thickness of the silicon substrate obtained under each condition and the thickness of the end portion (second surface side) of the silicon substrate on the side where cutting was completed in the ingot were measured, and the difference was evaluated as an absolute value. The difference in thickness is an average value when 500 sheets are measured. Moreover, the wire breakage rate under each condition was also confirmed. The disconnection rate was evaluated as a percentage of the number of disconnections when slicing 1000 times. The results are shown in Table 1.

  As shown in Table 1, it was confirmed that by making the second traveling speed of the wire slower than the first speed, the difference between the average thickness of the substrate and the thickness of the end of the cut end was reduced. In particular, by setting the thickness to 600 mm / min or less, the difference in thickness can be suppressed more effectively, and by slicing the wire without disconnection by reducing the feed speed to 400 mm / min or more. I was able to.

(Example 2)
Next, slicing of the silicon block was performed under the following conditions as part of the slicing conditions of Example 1. Regarding the slicing conditions at the time of cutting in the latter half, the second speed is 500 m / min, the cutting fluid supply flow rate is 75 L / min, 84 L / min, 90 L / min, 95 L / min, 108 L / min, 115 L / min. Conditions (No. 9 to No. 14) and the feed rate were 220 μm / min.

  The average thickness of the silicon substrate obtained in each condition and the thickness of the side edge at the end of cutting were measured, and the difference was evaluated as an absolute value. Moreover, the wire breakage rate under each condition was also confirmed. The results are shown in Table 2.

  No. No. 5, results and No. From the results of 9 to 14, it was confirmed that the difference between the average thickness of the substrate and the thickness of the end of the cut end is reduced by making the supply flow rate of the cutting fluid smaller than the condition at the time of cutting the central portion. In particular, when the supply flow rate of the cutting fluid at the time of the latter half cutting is 108 L / min or less, that is, the supply flow rate at the latter half cutting is 90% or less of the supply flow rate at the time of cutting the central portion, the thickness can be more effectively increased. The difference can be suppressed, and more than 84 L / min, that is, the supply flow rate at the time of cutting in the latter half is set to 70% or more of the supply flow rate at the cutting of the central portion, so that the wire can be sliced without disconnection. did it.

(Example 3)
Next, the slicing of the silicon block was performed under the conditions described below as part of the slicing conditions of Example 1. Regarding the slicing conditions at the time of cutting in the latter half, the second traveling speed of the wire is 600 m / min, the cutting fluid supply flow rate is 90 L / min, the cutting fluid supply flow rate at the end of cutting is 110 L / min, and the wire traveling Speed is 400m / min, 450m /
5 conditions (Nos. 15 to 19) of min, 510 m / min, 550 m / min, and 600 m / min. In addition, it was made to become the conditions at the time of cutting | disconnection of a termination | terminus part, when cutting 145 mm from the cutting start edge part.

  The presence or absence of burrs on the silicon substrate obtained under each condition was confirmed. X was given for burrs of 20 μm or more, △ for burrs of 20 μm or more and 10 μm or less, and ◯ for burrs of 10 μm or less. The results are shown in Table 3.

  No. From the results of 15 to 19, it was confirmed that the burr was reduced by increasing the supply flow rate of the cutting fluid and lowering the traveling speed of the wire in the cutting of the terminal portion than in the latter cutting conditions. In particular, the wire traveling speed at the time of cutting the terminal portion is 510 m / min or less, that is, the wire traveling speed at the time of cutting the terminal portion is set to 85% or less of the wire traveling speed at the latter half of cutting. In particular, the generation of burrs was reduced and the thickness of the burrs could be suppressed.

Example 4
First, an epoxy-based adhesive was applied to a slice base made of carbon, a rectangular parallelepiped polycrystalline silicon block of 156 mm × 156 mm × 300 mm was placed on the slice base, and the adhesive was cured. As shown in FIG. 1, a silicon block bonded to two slice bases is installed in a wire saw apparatus, and diamond abrasive grains (average particle diameter 10 μm) traveling in both directions with a coolant liquid made of glycol are provided. While supplying to the fixed wire (wire diameter 120 μm), the block bonded to the slice base was sliced to produce a silicon substrate having an average thickness of 200 μm. Slicing conditions at the time of cutting the central portion are the first traveling speed of the wire is 800 m / min, the feed speed of the silicon block is 500 μm / min, and the slicing conditions at the time of cutting the second surface are the second traveling speed of the wire Speeds of 250m / min, 300m / min, 350m / min, 400m / min, 450m / min, 500m / min, 550m / min, 600m / min (No. 20 to No. 27), silicon block feed The speed was 400 μm / min. In addition, it was made to become the conditions at the time of the cutting | disconnection of a 2nd surface when it cut | disconnects 150 mm from the cutting start edge part.

  In the slicing conditions of the comparative example, the traveling speed of the wire was constant at 800 m / min and the feed speed of the silicon block was constant at 500 μm / min.

  The crack generation rate of the silicon substrate obtained under each condition and the defect rate of saw marks in which traces of wires remain on the substrate were also confirmed. The results are shown in Table 4.

  As shown in Table 4, it was confirmed that the crack generation rate was reduced by making the second traveling speed of the wire slower than the first speed. In particular, the crack generation rate can be more effectively reduced by setting it to 500 mm / min or less, and it has been possible to slice by reducing the defect of the saw mark by setting it to 300 mm / min or more. .

It is the schematic which shows one Embodiment of the wire saw apparatus in the manufacturing method of the board | substrate of this invention. It is an enlarged view which shows one Embodiment of the cutting start edge part in the manufacturing method of the board | substrate of this invention. It is the figure which showed an example of the place which measures the thickness of a board | substrate. (A), (b) is a figure which shows one Embodiment of the time-dependent change of the wire travel speed in the manufacturing method of a board | substrate. (A) is a figure which shows the time-dependent change of the wire travel speed in the board | substrate manufacturing method, and the supply flow rate of a cutting fluid, (b) is one implementation of the time-dependent change of the wire travel speed and the block feed speed in the board | substrate manufacturing method. It is a figure which shows a form. It is an enlarged view which shows one Embodiment of the cutting start edge part in the manufacturing method of the board | substrate of this invention.

Explanation of symbols

1: Block 1a: Substrate 1s: First surface 1t on the side where cutting of the block is started: Second surface 3 on the side where cutting of the block is finished 3: Wire

Claims (17)

Providing a block having a first surface and a second surface on the first back side adhered to a base;
Advancing a wire to the first surface and starting cutting the block;
Cutting the central portion of the block with a wire traveling at a first speed;
Cutting the block on the second surface side from the central portion after cutting the block at the first speed with a wire traveling at a second speed slower than the first speed; and A method for manufacturing a substrate.   When the length from the first surface of the block to the second surface is a, the wire passes through a range of 2 / 3a or more and less than 17 / 20a from the first surface of the block. The substrate manufacturing method according to claim 1, wherein the traveling speed of the wire is shifted from the first speed to the second speed.   When the length from the first surface of the block to the second surface is a, the wire passes through the range of 17 / 20a or more and 19 / 20a or less from the first surface of the block. The substrate manufacturing method according to claim 1, wherein the traveling speed of the wire is shifted from the first speed to the second speed.   The second speed is such that the speed passing through the range from 17 / 20a to 19 / 20a from the first surface of the block is from 2 / 3a to 17 / 20a from the first surface of the block. The method for manufacturing a substrate according to claim 2, wherein the substrate is slower than a speed while passing through a range below.   5. The method of manufacturing a substrate according to claim 4, wherein the second speed is decreased stepwise or continuously as the wire advances from the central portion of the block to the second surface side. The substrate manufacturing method according to claim 1, wherein the block is a square block.   The feed speed for moving the block toward the wire is slower when cutting the second surface than the central portion than when cutting the central portion of the block. 7. The method for producing a substrate according to any one of 6 above.   8. The method of manufacturing a substrate according to claim 7, wherein the feed rate of the block is decreased stepwise or continuously as the wire advances from the central portion of the block to the second surface side.   The method for manufacturing a substrate according to claim 1, wherein the first speed is 600 m / min or more and 1000 m / min or less.   The method for manufacturing a substrate according to claim 1, wherein the second speed is 400 m / min or more and less than 600 m / min.   The feed speed of the block when cutting the second surface side of the block is 70% or more and 90% or less of the feed speed when cutting the central portion. A method for manufacturing the substrate according to claim 1.   The cutting of the block is performed by supplying cutting fluid containing abrasive grains, and the supply flow rate of the cutting fluid is closer to the second surface than the central portion than when cutting the central portion of the block. The method for manufacturing a substrate according to claim 2, wherein the time of cutting is smaller.   13. The substrate according to claim 12, wherein a supply flow rate of the cutting fluid is decreased stepwise or continuously as the wire advances from the central portion of the block to the second surface side. Manufacturing method   14. The substrate according to claim 12, wherein a supply flow rate of the cutting fluid is set larger when cutting the second surface of the block than when cutting the second surface of the block. Manufacturing method.   When the length from the first surface of the block to the second surface is a, the cutting fluid supply flow rate is within the range of 17 / 20a to 19 / 20a from the first surface of the block. The method for manufacturing a substrate according to any one of claims 12 to 14, wherein the size of the substrate is made larger than that when cutting 2 / 3a to 17 / 20a from the first surface of the block.   The cutting fluid supply flow rate when cutting the second surface side of the block is 70% or more and 90% or less of the cutting fluid supply flow rate when cutting the central portion. The manufacturing method of the board | substrate in any one of 12-15. A substrate made of silicon manufactured by the manufacturing method according to claim 1,
A solar cell element comprising a semiconductor junction region and an electrode formed on the substrate.

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