Multi-wire saw

The present invention relates to a multi-wire saw used when cutting a silicon ingot to manufacture wafers for semiconductors and solar cells.

Conventionally, a multi-wire saw that can cut a silicon ingot with a small cutting allowance and a uniform thickness or can cut a large number of wafers at a time has been used. Cutting of a silicon ingot using this multi-wire saw is performed by pressing the silicon ingot against a traveling wire and introducing a slurry containing abrasive grains into the cutting interface (see, for example, Patent Document 1). In cutting a silicon ingot using such a wire, the temperature of the slurry rises as the cutting of the ingot by the wire progresses, and the roller of the wire saw expands and contracts. Since the processing conditions of the ingot change, the processing accuracy of the ingot cannot be kept constant. Therefore, an attempt is made to cool the slurry to ensure processing accuracy (see, for example, Patent Document 2).

However, in recent years, it has been required to maintain high wafer quality for cutting silicon ingots and to reduce the cutting allowance and cutting pitch to reduce the wafer processing cost. In order to reduce the cutting allowance, the wire diameter may be reduced, but the breaking strength of the wire is reduced by that amount, so that the tension applied to the wire needs to be reduced. Since cutting of the ingot is performed by a wrapping action which is pressure transfer, if the tension of the wire is reduced, the cutting speed is slowed and the displacement (deflection) of the wire is increased. When the displacement (deflection) of the wire becomes large, the displacement of the wire in the direction orthogonal to the cutting direction also becomes large, and the wafer warps, the thickness unevenness, and the minute unevenness (saw mark) occur, and the quality of the wafer deteriorates. If the feed rate of the silicon ingot is reduced according to the delay in the cutting speed in order to reduce the bending of the wire, the cutting efficiency is lowered. Increasing the wire feed rate to compensate for the delay in cutting speed and increasing the feed rate of the silicon ingot eliminates the margin for poor dispersion of abrasive grains at the cutting interface and causes wire breakage due to a sudden increase in tension. To do. Therefore, it is necessary to reduce the cutting resistance in order to maintain high wafer quality and reduce the cutting allowance and cutting pitch of the silicon ingot. Therefore, a method of cutting a silicon ingot using a fixed abrasive wire and a slurry containing free abrasive grains or a KOH alkaline solution having a concentration of 2% or less has been proposed (see, for example, Patent Document 3).

On the other hand, in the multi-wire saw, when supplying the slurry to the wire, a large amount of slurry is discharged in a curtain shape from above the wire. Only a small amount of the supplied slurry adheres to the wire, and most of the slurry falls off below the wire, so the dropped slurry is stored in the slurry via the drain drawn from the floor of the processing chamber. It is collected in the tank. That is, most of the slurry is not used for cutting the silicon ingot, but is simply circulated from the slurry storage tank to the slurry storage tank via the slurry supply path and the discharge mechanism. Normally, in a multi-wire saw, since the processing chamber is kept in a negative pressure state in order to exhaust hydrogen and the like generated by the reaction, the water contained in the slurry evaporates in the process of supplying and circulating the slurry. In particular, when the slurry used is at a high temperature, the evaporation of water becomes remarkable, the viscosity of the slurry supplied and circulated becomes high, and the excess slurry that is not introduced into the cutting interface at the inlet where the wire is inserted into the silicon ingot. Dry and solidify. Changes in slurry viscosity lead to deterioration in processing quality (variation in wafer thickness, generation of saw marks). In addition, when solidified slurry accumulates at the inlet where the wire is inserted into the silicon ingot, it becomes resistant to the wire, or the solidified slurry fragments are caught at the cutting interface between the wire and the silicon ingot. It can eventually cause the wire to break. If the wire breaks during processing, not only the processing is interrupted, but also the silicon ingot during processing is wasted. In order to return to processing, man-hours such as silicon ingot removal work, cleaning work, and wire tensioning work are required, and productivity is significantly reduced.

<p><patcit num="1"><text>Japanese Patent No. 3187296</text></patcit><patcit num="2"><text>Japanese Unexamined Patent Publication No. 8-47850</text></patcit><patcit num="3"><text>Japanese Unexamined Patent Publication No. 2000-343525</text></patcit></p>

<p> The conventional cutting method using a fixed abrasive wire and a slurry containing free abrasive grains uses the fixed wire as a medium for transporting the free abrasive grains, and reduces the uncertainty of the amount of the free abrasive grains introduced into the cutting interface. As a result, the average amount of free abrasive grains introduced is increased, and fixed abrasive grains are allowed to act at the same time to wrap and cut the silicon ingot. The so-called number of blades in cutting is expected to increase, and the cutting efficiency is increased to reduce the apparent cutting resistance. However, as compared with the case of using a bare wire, it becomes difficult to discharge cutting chips and free abrasive grains, the concentration of cutting chips and free abrasive grains in the liquid at the cutting interface becomes high, and the slurry viscosity at the cutting interface becomes high. There is a problem. Also, fixed abrasive wire is very expensive and its use is significantly uneconomical. In the conventional cutting method using a fixed abrasive wire and an alkaline solution, the cutting chips cause clogging at the cutting interface, and a part of the alkaline solution is used to dissolve the cutting chips. Therefore, the cut surface of the alkaline solution is used. The work on is reduced. Further, the agglomerated cutting chips may give minute cracks to the cut surface, and the alkaline solution selectively works to expand such cracks and roughens the cut surface. The discharge resistance of cutting chips contributes to an increase in cutting resistance, resulting in warpage of the wafer, uneven thickness, and minute irregularities. In order to obtain the sufficient function of the alkaline solution, it is necessary to significantly reduce the wire feed rate and the silicon ingot feed rate, which causes a significant decrease in cutting efficiency. Therefore, a slurry containing abrasive grains and several mass% of a basic substance and having a pH of 12 or more is heated and supplied to the cutting interface to cut the ingot while pressing it against a bare wire, and as a result, the cutting resistance is reduced. It turns out that it can be done. In particular, it was found that the heating temperature of the slurry is preferably 65 ° C to 95 ° C. In order to obtain the effect of reducing such cutting resistance, it is important to control the temperature of the slurry introduced or introduced at the cutting interface to a predetermined temperature.</p><p> In the conventional cutting method disclosed in Patent Document 2, the temperature of the slurry is adjusted in the slurry storage tank, but the temperature of the slurry drops while the slurry is transported from the slurry storage tank to the slurry discharge portion, or the wire becomes a wire. The problem is that the temperature of the slurry drops at the chemical reaction point between the slurry and the ingot because the wire absorbs heat when the slurry is applied, or the slurry applied to the wire absorbs heat to the ingot when it comes into contact with the ingot. was there. Due to such a decrease in the temperature of the slurry, a phenomenon occurs in which the chemical reaction rate differs depending on the location of the chemical reaction interface between the ingot and the slurry, and as a result, the cutting resistance varies, and saw marks and uneven wafer thickness occur.</p><p> In addition, the conventional cutting method has the following problems. (1) Since a large amount of slurry is supplied and circulated, a slurry supply mechanism with a large flow rate and a large amount of power is required, which makes the device expensive. (2) Due to changes in composition during circulation (decrease in moisture and abrasive grains, phase separation of liquid components), the amount of abrasive grains in the slurry introduced into the ingot cutting interface is likely to decrease and the slurry viscosity is likely to change, resulting in processing. Quality variation occurs. (3) Since the slurry is scattered in the processing room and the processing room is heavily soiled, the cleaning man-hours after the operation are large. (4) Even in the temperature control of the slurry, the temperature of the slurry that circulates in large quantities without contributing to cutting must be controlled, and the responsiveness of the temperature control of the slurry introduced at the cutting interface is inferior. In addition, even if a large amount of slurry collected one after another in the tank is agitated, the uniform dispersibility of the abrasive grains is poor, and the abrasive grains are applied to the wire in a non-uniform manner, resulting in deterioration of processing quality (wafer thickness variation, saw mark (scratch)). ), Etc.).</p><p> The present invention has been made in view of the above problems, and an object of the present invention is to provide a multi-wire saw capable of reducing the cutting resistance at the time of cutting a silicon ingot and reducing the variation thereof. Further, the present invention is a multi-wire saw capable of maintaining high processing quality and preventing wire breakage by suppressing changes in the viscosity of the slurry and drying and solidification of the slurry at the inlet portion where the wire is inserted into the silicon ingot. The purpose is to provide. Further, the present invention has a high efficiency of using the slurry, an inexpensive device configuration, easy control of the temperature of the slurry, prolongation of the life of the rotating roller, and good workability such as cleaning and wire tensioning work. An object of the present invention is to provide a multi-wire saw.</p>

<p> According to the present invention, in a multi-wire saw that cuts a work piece while supplying a slurry to a wire traveling between a plurality of rollers, a slurry discharge part for discharging the slurry, and at least the slurry discharge part and the work piece. The multi-wire saw is provided with a processing chamber that covers the above and a humidity control mechanism for maintaining the humidity in the processing chamber in a state close to the saturated vapor pressure.</p><p> Further, according to the present invention, in a multi-wire saw that cuts an workpiece while supplying a slurry containing abrasive grains to a wire traveling between a plurality of rollers, the temperature of the accommodating portion accommodating the slurry and the slurry are maintained constant. A passage hole through which the wire can pass is provided on the constituent surface of the accommodating portion, and the wire passes through the accommodating portion to supply a slurry to the wire. The multi-wire saw is characterized in that the mechanism is provided upstream of the portion where the workpiece is cut.</p><p> Further, according to the present invention, in a multi-wire saw that cuts a work piece while supplying a slurry to a wire traveling between a plurality of rollers, the roller and the work piece provided on the upstream side of a portion for cutting the work piece. The wire is provided with a slurry supply mechanism having a slurry discharge portion provided between the portion for cutting the workpiece, and the slurry discharged from the slurry discharge portion moves along the side surface of the workpiece. It is a multi-wire saw characterized by supplying a slurry.</p>

<p> According to the present invention, since the cutting process can be performed while maintaining the alkaline slurry at a desired high temperature, the variation in the reaction rate depending on the location of the cutting interface between the workpiece and the slurry can be suppressed, and the cutting resistance can be reduced. Variations can be reduced, and saw marks, uneven wafer thickness, etc. can be suppressed. Further, according to the present invention, since the humidity in the processing chamber can be adjusted to the set humidity by the humidity adjusting mechanism, it is possible to prevent the wire from breaking while maintaining high processing quality. Further, according to the present invention, it is possible to improve the utilization efficiency of the slurry with an inexpensive device configuration, facilitate the temperature control of the slurry, prolong the life of the rotating roller, and improve the workability such as cleaning and wire tensioning work. be able to.</p>

<figref num="1">It is an external view of the multi-wire saw which concerns on Embodiment 1 of this invention.</figref><figref num="2">It is a partial external view of the multi-wire saw which concerns on Embodiment 1 of this invention.</figref><figref num="3">It is a figure which shows the structure of the wire heating mechanism of the multi-wire saw which concerns on Embodiment 2 of this invention.</figref><figref num="4">It is an external view of the multi-wire saw which concerns on Embodiment 3 of this invention.</figref><figref num="5">It is a partial external view of the multi-wire saw which concerns on Embodiment 3 of this invention.</figref><figref num="6">It is a figure for demonstrating the cutting process of the workpiece by the multi-wire saw which concerns on Embodiment 3 of this invention.</figref><figref num="7">It is a flowchart of humidity control which concerns on Embodiment 3 of this invention.</figref><figref num="8">It is a graph which shows the slurry viscosity in the slurry storage tank which concerns on Embodiment 3 of this invention.</figref><figref num="9">It is an external view of the multi-wire saw which concerns on Embodiment 4 of this invention.</figref><figref num="10">It is a partial external view of the multi-wire saw which concerns on Embodiment 4 of this invention.</figref><figref num="11">It is a figure for demonstrating the cutting process of the workpiece by the multi-wire saw which concerns on Embodiment 4 of this invention.</figref><figref num="12">It is a partial external view of the multi-wire saw which concerns on Embodiment 5 of this invention.</figref><figref num="13">It is an external view of the multi-wire saw which concerns on Embodiment 6 of this invention.</figref><figref num="14">It is a partial external view of the multi-wire saw which concerns on Embodiment 6 of this invention.</figref><figref num="15">It is a figure for demonstrating the cutting process of the workpiece by the multi-wire saw which concerns on Embodiment 6 of this invention.</figref><figref num="16">It is a partial external view of the multi-wire saw which concerns on Embodiment 7 of this invention.</figref><figref num="17">It is an X arrow view in FIG.</figref><figref num="18">It is a figure explaining the side wall part in the slurry supply mechanism of the multi-wire saw which concerns on Embodiment 8.</figref>

Embodiment 1 (reference example). FIG. 1 is an external view of the multi-wire saw according to the first embodiment of the present invention. FIG. 2 is a partial external view of the multi-wire saw of the first embodiment. The multi-wire saw according to the first embodiment includes a base 1, a frame 2 erected on the upper surface of the base 1, a work piece support mechanism 4 for supporting the work piece 3 so as to be movable in the work direction, and a work piece support mechanism 4. It is provided with a wire supply mechanism 6 that feeds into the workpiece 3 and supplies the wire 5 to the portion to be cut, and a slurry supply mechanism 8 that supplies the slurry 7 to the cutting interface between the workpiece 3 and the wire 5. Base 1 is composed of a flat plate that supports a multi-wire saw. The frame 2 is made of a box and is provided with a side plate 9 facing the operator.

The workpiece support mechanism 4 is movably supported with respect to the stage 11 for fixing the workpiece 3 via the dummy plate 10 and the frame 2, and while applying a predetermined load to the stage 11 in the machining direction. It is equipped with a stage movable mechanism 12 that pushes down the stage 11 and a constant temperature bath 13 that surrounds the stage 11. The constant temperature bath 13 includes a processing chamber 16 surrounded by four side walls 14 projecting in front of the four sides of the frame 2 and the frame 2 and a front wall 15 facing the frame 2 and connecting to the front side of the side wall 14. There is. As shown in FIG. 2, the constant temperature bath 13 is further processed based on the indoor thermometer 17 that measures the temperature inside the processing chamber 16, the hot plate 18 that heats the inside of the processing chamber 16, and the temperature measured by the indoor thermometer 17. It is equipped with a chamber temperature regulator 19 that adjusts the power supplied to the hot plate 18 so that the chamber temperature becomes the optimum temperature of the slurry 7.

The wire supply mechanism 6 is fitted to two motors (not shown) provided on the base 1, a feeding rotation shaft 20 and a winding rotation shaft 21 connected to the shafts of the motors, respectively, and a feeding rotation shaft 20. The wire feeding bobbin 22 to which the wire 5 is unwound, the wire winding bobbin 23 which is fitted to the take-up rotating shaft 21 and winds the wire 5 returned from the processing chamber 16, and the wire unwound from the wire feeding bobbin 22. A plurality of guide pulleys 25 for guiding the 5 to the main roller 24 supported by the frame 2, and a plurality of guide pulleys 26 for guiding the wire 5 returned from the main roller 24 to the wire winding bobbin 23 in between. It is provided with a tension control roller 43 that controls the tension of the wire 5 guided by the pulleys 25 and 26.

Further, the wire supply mechanism 6 is rotationally supported by the frame 2 so as to be parallel to the main roller 24 having a plurality of grooves formed at equal intervals on the outer peripheral surface and the frame 2 so as to be parallel to the main roller 24. On the other hand, it is provided with a sub-roller 27 which is rotationally supported and has a plurality of grooves formed at equal intervals on the outer peripheral surface. Further, in the wire supply mechanism 6, a bobbin heater 28 as a wire heating mechanism is built in the wire feeding bobbin 22. As this wire heating mechanism, an infrared heater provided in the vicinity of the main roller 24 and capable of irradiating the wire 5 with infrared rays or the like, or a hot water tank in which the wire 5 passes hot water in front of the main roller 24 can also be applied. The wire 5 is not limited to those capable of heating the wire 5.

The slurry supply mechanism 8 stores the slurry 7 supplied after adjustment and the slurry 7 collected and returned in the slurry tray 29 of the processing chamber 16, and controls the temperature of the slurry 7 to the optimum temperature. The storage tank 30 with a heating mechanism, the pump 31 that sends out the slurry 7 from the storage tank 30 with a heating mechanism, and the slurry 7 sent out from the pump 31 pass through it and reach the processing chamber 16 while being kept warm at the optimum temperature of the slurry 7. It is provided with a heat insulating pipe 32 to which liquid is sent, and a slurry discharging unit 33 for discharging the slurry 7 sent via the heat insulating pipe 32 toward the wire 5.

As shown in FIG. 2, the storage tank 30 with a heating mechanism measures the temperatures of the slurry storage tank 34, the slurry heating heater 35 that surrounds and heats the slurry storage tank 34, and the slurry 7 in the slurry storage tank 34. It is equipped with a thermometer 36 and a temperature controller 37 that adjusts the heating conditions of the slurry heating heater 35 based on the measured temperature of the slurry 7. Although a heating wire is used as the slurry heating heater 35, it is not limited to these as long as it can heat the slurry 7 such as a throw-in heater, a ribbon heater, and a hot water heater.

As shown in FIG. 2, the heat insulating pipe 32 includes a pipe 38 through which the slurry 7 can pass, a slurry heat insulating heater 39 wound around the side wall surface thereof, and a thermometer 40 that projects into the pipe 38 to measure the temperature of the slurry 7. And a temperature controller 41 that controls the heat retention condition of the slurry heat retention heater 39 based on the temperature of the slurry 7 in the pipe 38. A ribbon heater is used as the heat retaining heater 39, but it is not limited to these as long as the slurry 7 in the pipe 38 can be kept warm by flowing hot water through the pipe to the outside of the double pipe. ..

Next, a wafer will be produced by cutting the workpiece 3 using the multi-wire saw of the first embodiment. A polycrystalline silicon ingot (hereinafter referred to as an ingot) is used as the workpiece 3 at this time. Its outer shape is a prism with a size of 150 mm and a length of 25 mm. This ingot is fixed on a stainless steel base plate 44 via a glass dummy 10 with an adhesive made of epoxy resin or the like, and the base plate 44 is mechanically fixed to the stage 11.

Next, the wire is spirally wound between the main roller 24 and the sub roller 27. The wire 5 used here is formed of a hard steel wire (piano wire) and has a thickness of about 0.06 to 0.25 mm. In addition, the wire may be composed of an alloy such as a nickel-chromium alloy or an iron-nickel alloy, a refractory metal such as tungsten or molybdenum, or a bundle of polyamide fibers. First, the wire 5 is unwound from the wire feeding bobbin 22, the traveling guide is guided by the guide pulley 25 to change the traveling direction, and the wire 5 is unwound to the frontmost groove of the main roller 24. Then, while touching the inside of this groove, the sub-roller 27 is extended to the foremost groove of the sub-roller 27, and the sub-roller 27 is rotated counterclockwise by half a turn along the groove. From there, the main roller 24 is extended to the second groove from the front, and the main roller 24 is rotated counterclockwise by half a turn along the groove. By repeating these operations, a plurality of wires 5 spirally stretched at a desired pitch can be provided between the main roller 24 and the sub roller 27. Further, the wire 5 drawn from the sub roller 27 to the innermost groove of the main roller 24 is wound by the wire winding bobbin 23 while being guided by the guide pulley 26. The winding wire pitch of the main roller 24 and the sub roller 27 is equal to the cutting pitch of the ingot, and the number of windings is arbitrarily determined according to the number of wafers cut out from the ingot.

Next, the slurry 7 used when cutting the ingot will be described. The slurry 7 contains an alkali or mixed acid, the components of which consist of abrasive grains, basic substances and liquid components. The abrasive grains may be those generally used as an abrasive, and examples thereof include silicon carbide, cerium oxide, diamond, boron nitride, aluminum oxide, zirconium oxide, and silicon dioxide. In addition, these can be used alone or in combination of two or more. Compounds that can be used for such abrasive grains are commercially available. Specifically, as silicon carbide, trade names GC (Green Silicon Carbide) and C (Black Silicon Carbide) (manufactured by Fujimi Incorporated Co., Ltd.) ), Examples of aluminum oxide include trade names FO (Fujimi Optical Emery), A (Regular Fused Alimina), WA (White Fused Aluminum) and PWA (Platelet Calcined Aluminum) (manufactured by Fujimi Incorporated Co., Ltd.). The average particle size of the abrasive grains is not particularly limited, but is preferably 1 μm to 60 μm, and more preferably 5 μm to 20 μm. The content of the abrasive grains is not particularly limited, but is preferably 20% by mass to 50% by mass with respect to the total mass of the slurry 7.

The basic substance may be any substance that acts as a base in slurry 7, and for example, alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide, magnesium hydroxide, and calcium hydroxide. , Alkaline earth hydroxides such as barium hydroxide can be mentioned. In addition, these can be used alone or in combination of two or more. Among these, alkali metal hydroxides are preferable from the viewpoint of reactivity with silicon ingots. The content of the basic substance is 3.5% by mass or more and 20% by mass or less with respect to the total mass of the liquid components in the slurry 7.

Further, as the liquid component of the slurry 7, water, a known coolant, or a mixture thereof can be used. The water used here is preferably one having a low impurity content, but is not limited thereto. Specific examples include pure water, ultrapure water, city water, and industrial water. The water content is not particularly limited, but is preferably 10% by mass to 75% by mass with respect to the total mass of the slurry 7. Further, the coolant may be one generally used as a cutting auxiliary mixture containing a moisturizer, a lubricant, a rust preventive, a viscosity modifier, for example, polyethylene glycol, benzotriazole, oleic acid and the like. Such coolants are commercially available, and specific examples thereof include trade names Rica Martinol (manufactured by Rika Trading Co., Ltd.) and Luna Coolant (manufactured by Daichi Chemical Industry Co., Ltd.). The content of the coolant is not particularly limited, but is preferably 0% by mass to 50% by mass with respect to the total mass of the slurry 7.

Slurry 7 having such a structure can be prepared by mixing each component in a desired ratio. The method of mixing each component is arbitrary, and can be performed by, for example, stirring with a blade-type stirrer. Further, the mixing order of each component is also arbitrary. Further, for the purpose of purification or the like, the prepared slurry 7 may be further treated, for example, a filtration treatment, an ion exchange treatment or the like.

This slurry 7 has strong basicity. Therefore, the silicon ingot cutting interface is weakened by the reaction shown in the equation (1) and is wrapped by abrasive grains. Si + 4H₂O Si (OH)₄+ 2H₂ (1) The temperature of the slurry 7 that promotes the chemical reaction between the slurry 7 and the ingot is preferably in the range of 65 ° C to 95 ° C. If the temperature of the slurry 7 is too low, the reaction is not activated and the cutting resistance is not sufficiently reduced. If the temperature is too high, the water required for the reaction is insufficient due to the evaporation of the slurry liquid component (mainly water). However, the cutting resistance increases, which is not preferable.

The slurry 7 thus prepared is stored in the slurry storage tank 34 and heated to raise the temperature of the slurry 7 to 65 ° C to 95 ° C. The temperature-adjusted slurry 7 is discharged from the slurry protruding portion 33 while the temperature of the slurry 7 is kept at 65 ° C to 95 ° C in the heat insulating pipe 32. The slurry 7 adheres to the wire 5 located below the slurry discharge portion 33 and is introduced into the cutting interface between the ingot and the wire 5. The ingot is processed by contacting, pressurizing, and sliding the ingot pushed downward by the workpiece support mechanism 4 and the wire 5 with a slurry. Further, the temperature of the air in the processing chamber 16 is controlled to be 65 ° C to 95 ° C. Further, the temperature of the wire 5 is also heated to 65 ° C to 95 ° C. At this time, in the case of the optimum temperature of the slurry 7, for example, 80 ° C, the temperature of each of the air in the slurry 7, the wire 5, and the processing chamber 16 is controlled to be 80 ° C.

In addition, the rest of the slurry 7 discharged from the slurry discharge unit 33 and dropped down from the ingot and the wire 5 is collected by the slurry tray 29, separated from impurities (silicon chips, etc.), regenerated, and then the slurry. It is returned to the slurry storage tank 34 via the recovery drain pipe 46.

As a specific example of the composition of slurry 7, 4 parts by mass of sodium hydroxide is dissolved in 46 parts by mass of water to make a basic aqueous solution, and this aqueous solution and 50 parts by mass of coolant (Luna Coolant # 691 manufactured by Daichi Chemical Industry Co., Ltd.) ) And mixed. To this mixed solution, 100 parts by mass of SiC abrasive grains (manufactured by Fujimi Incorporated, GC # 1200, average particle diameter of about 10 μm) were further added and stirred to adjust slurry 7. The pH of the obtained slurry 7 at 25 ° C was 13.9.

Next, using the obtained slurry 7, a polycrystalline silicon ingot (150 mm square, 25 mm long) was cut under the cutting conditions shown below to prepare a wafer. The cutting conditions were a wire diameter of 0.1 mm, a cutting allowance of 0.13 mm, a cutting pitch of 0.39 mm, a cutting speed of 0.35 mm / min, a wire running speed of 600 m / min, and a slurry temperature of 80 ° C. As a comparative example, the ingot was cut in the same manner with the slurry temperature set to 25 ° C. At that time, the amount of deflection of the wire 5 was measured as an index showing the magnitude of the cutting resistance. The results are shown in Table 1. If a cutting resistance is generated at the cutting interface between the traveling wire 5 and the ingot during the cutting process, the wire 5 bends in the ingot feeding direction. Since this deflection is proportional to the magnitude of the cutting resistance, the magnitude of the cutting resistance can be known by measuring the amount of wire deflection during the cutting process. In other words, a large deflection means that the wire 5 at the cutting interface is delayed in the cutting direction (two directions), and the desired cutting speed cannot be obtained. Next, the obtained wafer was washed with water and dried, and then the thickness unevenness of the wafer was evaluated. Further, the presence or absence of saw marks on the wafer surface was visually evaluated. These results are shown in Table 1.

<tables num="1"><img file="JP4907682B2_D0001.tif" /></tables>

As is clear from Table 1, by controlling the slurry 7 to a temperature of 80 ° C, the thickness unevenness is small, the high wafer quality with no saw marks is maintained, and the amount of wire deflection, that is, the cutting resistance is significantly reduced. I was able to reduce it.

As described above, according to the first embodiment, since the cutting process can be performed while maintaining the temperature of the slurry and the workpiece at desired values, high wafer quality with small thickness unevenness and extremely few saw marks is maintained. At the same time, the amount of wire deflection, that is, the cutting resistance can be significantly reduced.

Embodiment 2 (reference example). FIG. 4 is an external view of the wire heating mechanism of the multi-wire saw according to the second embodiment of the present invention. Since the wire heating mechanism of the multi-wire saw of the second embodiment is different from that of the first embodiment and the other parts are the same, the description of the same part will be omitted. This wire heating mechanism includes two pulleys 25a and 25b of a plurality of guide pulleys 25 for guiding the wire 5 between the wire feeding bobbin 22 and the main roller 24, and the wires 5 having a desired length are separated as much as possible. It is equipped with a power supply 42 that supplies voltage between the two pulleys 25a and 25b. The pulleys 25a and 25b are conductive and can be conducted between the pulleys 25a and 25b and the wire 5. The wire feeding bobbin 22 and the wire winding bobbin 23 have an insulating property because the wire 5 is electrically floated. This wire heating mechanism can generate Joule heat to heat the wire 5 by passing an electric current through the wire 5 between the pulleys 25a and 25b.

The wire 5 used in the second embodiment is a piano wire having a resistance R = 28.3 (Ω / m) and a diameter D = 0.1 (mm), a wire feed speed of v = 10 (m / s), and between pulleys. The distance is L = 0.4 (m), and the voltage required to raise the temperature of wire 5 by T = 60 (K) is calculated below. The time t (sec) required for the minute portion Δx of the wire 5 to pass between the pulleys can be obtained from Eq. (2). t = L / v = 0.04 [sec] (2) Furthermore, the mass W (g) of the wire 5 existing between the pulleys has a wire specific gravity of A = 7.8 (g / cm).²), Which can be obtained from Eq. (3). W = (πD²/ 4) L A = 0.025 [g] (3) Therefore, the amount of heat Q (J) required for raising the temperature can be obtained from Eq. (4) with the specific heat of the wire as C = 0.5 (J / gK). Q = ΔT C W = 0.74 [J] (4) The amount of current I (A) flowing through the wire 5 at this time can be obtained from the required amount of heat Q from Eq. (5). I = (Q / Rt)^1/2= 1.3 [A] (5) Therefore, the inter-pulley voltage V (V) that must be applied between the pulleys is as shown in Eq. (6). V = IR = 14 [V] (6)

As described above, according to the second embodiment, the wire can be easily heated by using a commercially available general-purpose voltage source, a battery, or the like. Further, the heating temperature of the wire can be easily controlled by changing the power supply voltage.

Embodiment 3. FIG. 4 is an external view of the multi-wire saw according to the third embodiment of the present invention, and FIG. 5 is a partial external view of the multi-wire saw according to the third embodiment. Further, FIG. 6 is a diagram for explaining a process of cutting the workpiece by the multi-wire saw of the third embodiment. The multi-wire saw according to the third embodiment includes a base 1, a frame 2 erected on the upper surface of the base 1, a work piece support mechanism 4 for supporting the work piece 3 so as to be movable in the work direction, and a work piece support mechanism 4. It is provided with a wire supply mechanism 6 that feeds into the workpiece 3 and supplies the wire 5 to the portion to be cut, and a slurry supply mechanism 8A that supplies the slurry 7 to the cutting interface between the workpiece 3 and the wire 5. Base 1 is composed of a flat plate that supports a multi-wire saw. The frame 2 is composed of a box and is provided with a side plate 9 facing the operator.

The workpiece support mechanism 4 is movably supported with respect to the stage 11 for fixing the workpiece 3 via the dummy plate 10 and the frame 2, and while applying a predetermined load to the stage 11 in the machining direction. It is equipped with a stage movable mechanism 12 that pushes down the stage 11 and a processing chamber 16 that surrounds the stage 11. The processing chamber 16 is surrounded by four side walls 14 projecting in front of the four sides of the frame 2 and the frame 2, and a front wall 15 facing the frame 2 and connecting to the front side of the side wall 14. As shown in FIG. 5, on the ceiling surface of the processing chamber 16, a discharge port 45 for discharging the atmosphere (including gas generated during cutting, for example, hydrogen) in the processing chamber 16 is provided, and the processing chamber 16 is provided. A slurry collection drain pipe 46 is connected to the slurry tray 29 of the above. Further, on the ceiling surface of the processing chamber 16, a humidity control mechanism 47 for adjusting the humidity in the processing chamber 16 to the set humidity is attached. This humidity control mechanism 47 is based on the comparison result between the humidifying device 49 for generating water vapor 48, the hygrometer 50 for measuring the humidity, and the measured humidity in the processing chamber 16 and the humidifying device 49. It is equipped with a control device 51 that starts and stops. Therefore, the humidity in the processing chamber 16 can be adjusted by the humidity control mechanism 47. The humidifier 49 used here is not particularly limited as long as it can generate water vapor 48, and examples thereof include an ultrasonic humidifier and a heater humidifier.

The wire supply mechanism 6 is fitted to two motors (not shown) provided on the base 1, a feeding rotation shaft 20 and a winding rotation shaft 21 connected to the shafts of the motors, respectively, and a feeding rotation shaft 20. The wire feeding bobbin 22 to which the wire 5 is unwound, the wire winding bobbin 23 which is fitted to the take-up rotating shaft 21 and winds the wire 5 returned from the processing chamber 16, and the wire unwound from the wire feeding bobbin 22. A plurality of guide pulleys 25 for guiding the 5 to the main roller 24 supported by the frame 2, and a plurality of guide pulleys 26 for guiding the wire 5 returned from the main roller 24 to the wire winding bobbin 23 in between. It is provided with a tension control roller 43 that controls the tension of the wire 5 guided by the pulleys 25 and 26. Further, the wire supply mechanism 6 is rotationally supported by the frame 2 so as to be parallel to the main roller 24 having a plurality of grooves formed at equal intervals on the outer peripheral surface and the frame 2 so as to be parallel to the main roller 24. On the other hand, it is provided with a sub-roller 27 which is rotationally supported and has a plurality of grooves formed at equal intervals on the outer peripheral surface.

The slurry supply mechanism 8A includes a slurry storage tank 34 for storing the slurry 7 supplied to the wire 5 and the slurry tray 29 of the processing chamber 16 and returned via the slurry collection drain pipe 46, and a slurry storage tank 34. The pump 31 that sends the slurry 7 from the tank 34, the pipe 32A that the slurry 7 sent from the pump 31 is sent to the processing chamber 16 through the pump 31, and the slurry 7 that is sent via the pipe 32A. Is provided with a slurry discharge unit 33 that discharges the pipe toward the wire 5. The slurry discharge portion 33 is arranged in the processing chamber 16 above the sub-roller 27 arranged on the upstream side of the portion for cutting the workpiece 3 and the portion for cutting the workpiece 3. There is. The slurry storage tank 34 may be arranged inside the processing chamber 16, but it may be arranged outside the processing chamber 16 because the amount of slurry storage is limited and the structure inside the processing chamber 16 becomes complicated. desirable.

Next, a wafer will be produced by cutting the workpiece 3 using the multi-wire saw of the third embodiment. A polycrystalline silicon ingot (hereinafter referred to as an ingot) is used as the workpiece 3 at this time. This ingot is fixed on a stainless steel base plate 44 via a glass dummy 10 with an adhesive made of epoxy resin or the like, and the base plate 44 is mechanically fixed to the stage 11.

Next, the wire 5 is spirally wound between the main roller 24 and the sub roller 27. The wire 5 used here is formed of a hard steel wire (piano wire) and has a thickness of about 0.06 to 0.25 mm. In addition, the wire may be composed of an alloy such as a nickel-chromium alloy or an iron-nickel alloy, a refractory metal such as tungsten or molybdenum, or a bundle of polyamide fibers. First, the wire 5 is unwound from the wire feeding bobbin 22, the traveling guide is guided by the guide pulley 25 to change the traveling direction, and the wire 5 is unwound to the frontmost groove of the main roller 24. Then, while touching the inside of this groove, the sub-roller 27 is extended to the foremost groove of the sub-roller 27, and the sub-roller 27 is rotated counterclockwise by half a turn along the groove. From there, the main roller 24 is extended to the second groove from the front, and the main roller 24 is rotated counterclockwise by half a turn along the groove. By repeating these operations, a plurality of wires 5 spirally stretched at a desired pitch can be provided between the main roller 24 and the sub roller 27. Further, the wire 5 drawn from the sub roller 27 to the innermost groove of the main roller 24 is wound by the wire winding bobbin 23 while being guided by the guide pulley 26. The winding wire pitch of the main roller 24 and the sub roller 27 is equal to the cutting pitch of the ingot, and the number of windings is arbitrarily determined according to the number of wafers cut out from the ingot.

In such a multi-wire saw, when the wire supply mechanism 6 is driven, the wire 5 travels in a constant direction at a predetermined speed while maintaining a constant tension by the tension control roller 43. At this time, the main roller 24 and the sub roller 27 rotate synchronously at a rotation speed corresponding to the traveling speed of the wire 5. In the processing chamber 16, the wires 5 are guided along the grooves of the main rollers 24 and the sub rollers 27, so that the rows of the wires 5 are arranged at a constant tension below the stage 11 while running in parallel. It will be. Here, the workpiece support mechanism 4 pushes down the ingot as the workpiece 3 toward the wire 5, so that the ingot comes into contact with the traveling wire 5 and is pressed against the wire 5. At this time, as shown in FIG. 6, when the slurry 7 is discharged from the slurry discharge portion 33 and supplied to the traveling wire 5, the slurry 7 is carried to the cutting interface of the ingot by the traveling wire 5. Then, the bond of the silicon atom is broken by the wrapping action and the chemical action of the slurry 7, and the ingot is cut.

In such a cutting process, as shown in FIG. 5, steam 48 is released into the processing chamber 16 from the humidity control mechanism 47, so that the humidity (relative humidity) in the processing chamber 16 becomes saturated vapor pressure. It is kept close. The humidity control in the processing chamber 16 by the humidity control mechanism 47 will be described with reference to FIG. 7. First, when it is confirmed that the multi-wire saw is operating, in step 101, the set humidity input to the control device 51 is read, and the process proceeds to step 102. In step 102, the humidity in the processing chamber 16 measured by the hygrometer 50 is read, and the process proceeds to step 103. In step 103, the control device 51 determines whether or not the measured humidity in the processing chamber 16 is within the set range. If the measured humidity in the processing chamber 16 is lower than the set range, the determination is denied and the process proceeds to step 104, and humidification by the humidifying device 49 is started. On the other hand, if the measured humidity in the processing chamber 16 is higher than the set range in step 103, the determination is affirmed and the process proceeds to step 105, and the humidification by the humidifying device 49 is stopped.

Here, it is desirable to adjust the humidity in the processing chamber 16 to 95 to 99%. If the humidity is too low, the amount of water contained in the slurry 7 evaporates and the viscosity of the slurry 7 increases, which may cause saw marks. If the humidity is too high, the water vapor 48 released into the processing chamber 16 becomes water droplets and is collected by the slurry tray 29, and the slurry 7 in the slurry storage tank 34 is diluted to reduce the viscosity. When the viscosity of the slurry 7 decreases, the amount of the slurry 7 falling off from the wire 5 increases, and the cutting efficiency may decrease.

In the multi-wire saw according to the third embodiment, 46 parts by mass of water, 4 parts by mass of sodium hydroxide, 50 parts by mass of propylene glycol, and 100 parts by mass of abrasive grains (titanium carbide having an average particle size of 10 μm). A silicon ingot cutting experiment was conducted under the conditions of a humidity of 98% and a temperature of 80 ° C in the processing chamber 16 using a slurry containing and. The slurry in the slurry storage tank 34 is collected at predetermined time (0, 2, 4 and 7 hours), and the shear rate is 57.6 [s] using a rotational viscometer (Brookfield's programmable rheometer DV-III).^-1], The viscosity at 25 ° C was measured. The results are shown in Fig. 8. As is clear from FIG. 8, when the ingot is cut in the processing chamber 16 in which the humidity is maintained close to the saturated vapor pressure, the evaporation of the water contained in the slurry 7 is suppressed. The viscosity is kept almost constant. On the other hand, in the conventional multi-wire saw without humidification (humidity in the processing chamber is about 70%), the viscosity of slurry 7 increased significantly within 2 hours from the start of cutting.

Further, in the multi-wire saw according to the third embodiment, using a slurry having a sodium hydroxide concentration of 4% by mass at 80 ° C and a piano wire with a diameter of 0.1 mm, cutting at a humidity of 98% in the processing chamber. When the silicon ingot (150 mm square, 25 mm long) was cut under the conditions of a speed of 0.35 mm / min and a wire traveling speed of 600 m / min, it was confirmed that the silicon ingot could be cut without breaking the wire. On the other hand, when the silicon ingot was cut using a conventional multi-wire saw, the wire was broken about 1 hour after the start of the cutting process (cutting length of about 21 mm).

As described above, according to the third embodiment, since the humidity in the processing chamber 16 is maintained in a state close to the saturated vapor pressure, the change in viscosity of the slurry 7 is extremely small, and the wire 5 serves as the workpiece 3. The slurry 7 does not dry and solidify at the inlet portion inserted into the silicon wire. Therefore, it is possible to prevent the wire from breaking while maintaining high processing quality. Further, unlike the conventional multi-wire saw, a mechanism for adjusting the viscosity while supplying water to the slurry storage tank 34 becomes unnecessary, and the viscosity control of the slurry becomes easy.

In the multi-wire saw according to the third embodiment, the slurry discharge portion 33 is located above between the sub-roller 27 arranged on the upstream side of the portion for cutting the workpiece 3 and the portion for cutting the workpiece 3. Was placed, but it is not limited to this. For example, the slurry 7 discharged from the slurry discharge unit 33 moves along the side surface of the workpiece 3 and is close to the upstream side wall surface of the portion where the workpiece 3 is cut so as to be supplied to the wire 5. May be placed. Further, in the multi-wire saw according to the third embodiment, the humidity control mechanism 47 is arranged in the processing chamber 16, but it is sufficient if the humidity control mechanism 47 can release water vapor 48 into the processing chamber 16, and the present invention is limited to this. Not done. For example, the humidity control mechanism 47 may be arranged outside the processing chamber 16 and water vapor 48 may be discharged from the humidity control mechanism 47 into the processing chamber 16 via piping or the like. Further, a forced convection fan or the like may be provided in the processing chamber 16 according to the third embodiment so that the humidity in the processing chamber 16 becomes uniform. Further, in order to adjust the temperature of the slurry 7, a slurry heating heater that surrounds and heats the slurry storage tank 34 may be provided. The heater for heating the slurry is not limited as long as it can heat the slurry 7, but examples thereof include a heating wire, a throw-in heater, a ribbon heater, and a hot water heater.

Embodiment 4. FIG. 9 is an external view of the multi-wire saw according to the fourth embodiment of the present invention, and FIG. 10 is a partial external view of the multi-wire saw according to the fourth embodiment. Further, FIG. 11 is a diagram for explaining a process of cutting the workpiece by the multi-wire saw of the fourth embodiment. The multi-wire saw according to the fourth embodiment includes a base 1, a frame 2 erected on the upper surface of the base 1, a work piece support mechanism 4 for supporting the work piece 3 so as to be movable in the work direction, and a work piece support mechanism 4. It is provided with a wire supply mechanism 6 that feeds into the workpiece 3 and supplies the wire 5 to the portion to be cut, and a slurry supply mechanism 8B that supplies the slurry 7 to the cutting interface between the workpiece 3 and the wire 5. Base 1 is composed of a flat plate that supports a multi-wire saw. The frame 2 is composed of a box and is provided with a side plate 9 facing the operator.

The workpiece support mechanism 4 is movably supported with respect to the stage 11 for fixing the workpiece 3 via the dummy plate 10 and the frame 2, and while applying a predetermined load to the stage 11 in the machining direction. It is equipped with a stage movable mechanism 12 that pushes down the stage 11 and a processing chamber 16 that surrounds the stage 11. The processing chamber 16 is surrounded by four side walls 14 projecting in front of the four sides of the frame 2 and the frame 2, and a front wall 15 facing the frame 2 and connecting to the front side of the side wall 14.

The wire supply mechanism 6 is fitted to two motors (not shown) provided on the base 1, a feeding rotation shaft 20 and a winding rotation shaft 21 connected to the shafts of the motors, respectively, and a feeding rotation shaft 20. The wire feeding bobbin 22 to which the wire 5 is unwound, the wire winding bobbin 23 which is fitted to the take-up rotating shaft 21 and winds the wire 5 returned from the processing chamber 16, and the wire unwound from the wire feeding bobbin 22. A plurality of guide pulleys 25 for guiding the 5 to the main roller 24 supported by the frame 2, and a plurality of guide pulleys 26 for guiding the wire 5 returned from the main roller 24 to the wire winding bobbin 23 in between. It is provided with a tension control roller 43 that controls the tension of the wire 5 guided by the pulleys 25 and 26. Further, the wire supply mechanism 6 is rotationally supported by the frame 2 so as to be parallel to the main roller 24 having a plurality of grooves formed at equal intervals on the outer peripheral surface and the frame 2 so as to be parallel to the main roller 24. On the other hand, it is provided with a sub-roller 27 which is rotationally supported and has a plurality of grooves formed at equal intervals on the outer peripheral surface.

Next, the supply of the slurry 7 to the wire 5 by the slurry supply mechanism 8B will be specifically described with reference to FIG. The slurry supply mechanism 8B includes a slurry storage tank 34 for storing the slurry 7 supplied to the wire 5 and the slurry tray 29 of the processing chamber 16 and returned via the slurry collection drain pipe 46, and a slurry storage tank 34. The pump 31 that sends the slurry 7 from the tank 34, the pipe 32A that the slurry 7 sent from the pump 31 is sent to the processing chamber 16 through the pump 31, and the slurry 7 that is sent via the pipe 32A. Is provided with a slurry discharge unit 33 that discharges the pipe toward the wire 5. As shown in FIG. 10, the slurry discharge portion 33 is above between the sub-roller 27 provided on the upstream side of the portion for cutting the workpiece 3 and the portion for cutting the workpiece 3. The discharged slurry 7 is installed so as to move along the side surface of the workpiece 3 (close to the upstream side wall surface of the portion where the workpiece 3 is cut). When the slurry 7 is supplied to the wire 5 by the slurry discharge unit 33, the slurry 7 is discharged from the slurry discharge unit 33 in a curtain shape, for example. At this time, since the slurry discharge portion 33 is above the cutting portion of the workpiece 3, the discharged slurry 7 flows down along the side surface of the workpiece 3. When the slurry 7 moves to the intersection of the wire 5 and the workpiece 3 without evaporating water and comes into contact with the wire 5, the slurry 7 is carried by the wire 5 to the cutting interface of the workpiece 3. In such a cutting process, the viscosity of the slurry 7 is always constant because the slurry 7 is constantly flowing at the side surface of the workpiece 3, particularly at the intersection of the traveling wire 5 and the workpiece 3.

Next, a wafer will be produced by cutting the workpiece 3 using the multi-wire saw of the fourth embodiment. A polycrystalline silicon ingot (hereinafter referred to as an ingot) is used as the workpiece 3 at this time. This ingot is fixed on a stainless steel base plate 44 via a glass dummy 10 with an adhesive made of epoxy resin or the like, and the base plate 44 is mechanically fixed to the stage 11.

Next, the wire 5 is spirally wound between the main roller 24 and the sub roller 27. The wire 5 used here is formed of a hard steel wire (piano wire) and has a thickness of about 0.06 to 0.25 mm. In addition, the wire may be composed of an alloy such as a nickel-chromium alloy or an iron-nickel alloy, a refractory metal such as tungsten or molybdenum, or a bundle of polyamide fibers. First, the wire 5 is unwound from the wire feeding bobbin 22, the traveling guide is guided by the guide pulley 25 to change the traveling direction, and the wire 5 is unwound to the frontmost groove of the main roller 24. Then, while touching the inside of this groove, the sub-roller 27 is extended to the foremost groove of the sub-roller 27, and the sub-roller 27 is rotated counterclockwise by half a turn along the groove. From there, the main roller 24 is extended to the second groove from the front, and the main roller 24 is rotated counterclockwise by half a turn along the groove. By repeating these operations, a plurality of wires 5 spirally stretched at a desired pitch can be provided between the main roller 24 and the sub roller 27. Further, the wire 5 drawn from the sub roller 27 to the innermost groove of the main roller 24 is wound by the wire winding bobbin 23 while being guided by the guide pulley 26. The winding wire pitch of the main roller 24 and the sub roller 27 is equal to the cutting pitch of the ingot, and the number of windings is arbitrarily determined according to the number of wafers cut out from the ingot.

In such a multi-wire saw, when the wire supply mechanism 6 is driven, the wire 5 travels in a constant direction at a predetermined speed while maintaining a constant tension by the tension control roller 43. At this time, the main roller 24 and the sub roller 27 rotate synchronously at a rotation speed corresponding to the traveling speed of the wire 5. In the processing chamber 16, the wires 5 are guided along the grooves of the main rollers 24 and the sub rollers 27, so that the rows of the wires 5 are arranged at a constant tension below the stage 11 while running in parallel. It will be. Here, the workpiece support mechanism 4 pushes down the ingot as the workpiece 3 toward the wire 5, so that the ingot comes into contact with the traveling wire 5 and is pressed against the wire 5. At this time, as shown in FIG. 11, when the slurry 7 is discharged from the slurry discharge portion 33, moves along the side surface of the ingot, and is supplied to the traveling wire 5, the traveling wire 5 reaches the cutting interface of the ingot. Will be carried. Then, the bond of the silicon atom is broken by the wrapping action and the chemical action of the slurry 7, and the ingot is cut. In addition, the rest of the slurry 7 discharged from the slurry discharge unit 33 and dropped down from the ingot and the wire 5 is collected by the slurry tray 29, separated from impurities (silicon chips, etc.), regenerated, and then the slurry. It is returned to the slurry storage tank 34 via the recovery drain pipe 46.

In the multi-wire saw according to the fourth embodiment, a slurry having a sodium hydroxide concentration of 4% by mass at 80 ° C and a piano wire with a diameter of 0.1 mm are used to cut a cutting speed of 0.35 mm / min and a wire traveling speed. A silicon ingot (150 mm square, 25 mm long) was cut under the condition of 600 m / min (the wire was not broken). After cutting, as a result of observing the inlet portion where the wire was inserted into the silicon ingot, no solidified slurry was observed. When a silicon ingot is cut using a conventional multi-wire saw and the wire breaks about 1 hour after the start of cutting (cutting length of about 21 mm), a large amount of solidified slurry adheres to the inlet. It was.

As described above, according to the fourth embodiment, since the slurry 7 is constantly flowing at the intersection of the traveling wire 5 and the ingot as the workpiece 3, the slurry 7 does not dry or solidify. Therefore, it is possible to reduce the resistance applied to the running of the wire 5, and it is possible to prevent the wire from breaking, which significantly reduces the productivity.

Embodiment 5. FIG. 12 is a partial external view of the multi-wire saw according to the fifth embodiment. In the multi-wire saw according to the fifth embodiment, the slurry supply mechanism 8C includes a sheet member 52 attached to the side surface of the workpiece 3. Other configurations are the same as those in the fourth embodiment.

The sheet member 52 used here may be made of a material that does not react with the slurry 7 or has extremely low reactivity. For example, in the case of the slurry 7 containing a strong alkaline substance such as sodium hydroxide, polyethylene is used. Examples thereof include polypropylene, methylpentene resin, fluororesin, natural rubber, styrene rubber, butyl rubber, ethylene / propylene rubber and the like. Further, the sheet member 52 is preferably smaller than the hardness of the workpiece 3 from the viewpoint of cutting efficiency. Further, since the cut portion of the workpiece 3 may have a high temperature of about 100 ° C due to the resistance applied to the running of the wire 5, the glass transition when the sheet member 52 made of the above material is attached. It is preferable to use a thermoplastic adhesive having a temperature of 100 ° C. or higher.

In such a slurry supply mechanism 8C, since the sheet member 52 is attached to the side surface of the workpiece 3, the slurry 7 discharged from the slurry discharge portion 33 flows down along the surface of the sheet member 52. Therefore, even if the slurry 7 having a chemical reactivity with the workpiece 3 is continuously discharged to the side surface of the workpiece 3, the side surface of the workpiece 3 is not etched.

As described above, according to the fifth embodiment, even if the slurry 7 having chemical reactivity with the workpiece is continuously discharged to the side surface of the workpiece 3, the side surface of the workpiece 3 is not etched and the workpiece 3 is processed. It is possible to suppress the dimensional change of the object 3 as much as possible.

In the multi-wire saw according to the fourth and fifth embodiments, the slurry discharge portion 33 is installed above between the sub roller 27 and the portion where the workpiece 3 is cut, but the discharged slurry 7 is the workpiece. It is not limited upward as long as it can move along the side surface of 3 and come into contact with the wire 5. For example, the slurry discharge portion 33 may be installed sideways or below between the sub roller 27 and the portion where the workpiece 3 is cut, and the slurry 7 may be ejected toward the side surface of the workpiece 3.

Further, inside the slurry storage tank 34 according to the fourth and fifth embodiments, moisture control for keeping the amount of water in the slurry 7 constant so that the composition of the slurry 7 discharged from the slurry discharge unit 33 is constant. A mechanism, a temperature control mechanism for keeping the temperature of the slurry 7 constant, a stirring mechanism for preventing precipitation and aggregation of the slurry, and the like may be provided. In particular, when the slurry 7 is used at a high temperature of about 65 to 95 ° C, the composition changes due to the evaporation of water, so it is desirable to provide a water control mechanism. At that time, if the amount of water evaporation per unit time is obtained in advance, it is sufficient to supply water to the slurry storage tank 34 at a constant ratio, so that the amount of water in the slurry 7 can be more easily adjusted. .. In the fourth and fifth embodiments, the slurry 7 is moved along the side surface of the workpiece 3 to supply the slurry 7, and the slurry 7 is directly applied to the wire 5 to supply the slurry 7. May be used in combination to introduce the slurry 7 at the cutting interface of the workpiece 3. In this case, the slurry 7 that is directly applied and supplied to the wire 5 is mainly used to cut the workpiece 3, and the slurry 7 that moves along the side surface of the workpiece 3 is inserted into the workpiece 3 by the wire 5. It is preferable to use it as an auxiliary means for preventing the solidification of the slurry 7 at the entrance portion where the slurry 7 is formed. Therefore, it is preferable to minimize the flow rate of the slurry 7 moving along the side surface of the workpiece 3.

Embodiment 6. FIG. 13 is an external view of the multi-wire saw according to the sixth embodiment of the present invention, and FIG. 14 is a partial external view of the multi-wire saw according to the sixth embodiment. Further, FIG. 15 is a diagram for explaining a process of cutting the workpiece by the multi-wire saw of the sixth embodiment. The multi-wire saw according to the sixth embodiment includes a base 1, a frame 2 erected on the upper surface of the base 1, a work piece support mechanism 4 for supporting the work piece 3 so as to be movable in the work direction, and a work piece support mechanism 4. It is provided with a wire supply mechanism 6 that feeds into the workpiece 3 and supplies the wire 5 to the portion to be cut, and a slurry supply mechanism 8D that supplies the slurry 7 to the cutting interface between the workpiece 3 and the wire 5. Base 1 is composed of a flat plate that supports a multi-wire saw. The frame 2 is composed of a box and is provided with a side plate 9 facing the operator.

The workpiece support mechanism 4 is movably supported with respect to the stage 11 for fixing the workpiece 3 via the dummy plate 10 and the frame 2, and while applying a predetermined load to the stage 11 in the machining direction. It is equipped with a stage movable mechanism 12 that pushes down the stage 11 and a processing chamber 16 that surrounds the stage 11. The processing chamber 16 is surrounded by four side walls 14 projecting in front of the four sides of the frame 2 and the frame 2, and a front wall 15 facing the frame 2 and connecting to the front side of the side wall 14.

The wire supply mechanism 6 is fitted to two motors (not shown) provided on the base 1, a feeding rotation shaft 20 and a winding rotation shaft 21 connected to the shafts of the motors, respectively, and a feeding rotation shaft 20. The wire feeding bobbin 22 to which the wire 5 is unwound, the wire winding bobbin 23 which is fitted to the take-up rotating shaft 21 and winds the wire 5 returned from the processing chamber 16, and the wire unwound from the wire feeding bobbin 22. A plurality of guide pulleys 25 for guiding the 5 to the main roller 24 supported by the frame 2, and a plurality of guide pulleys 26 for guiding the wire 5 returned from the main roller 24 to the wire winding bobbin 23 in between. It is provided with a tension control roller 43 that controls the tension of the wire 5 guided by the pulleys 25 and 26. Further, the wire supply mechanism 6 is rotationally supported by the frame 2 so as to be parallel to the main roller 24 having a plurality of grooves formed at equal intervals on the outer peripheral surface and the frame 2 so as to be parallel to the main roller 24. On the other hand, it is provided with a sub-roller 27 which is rotationally supported and has a plurality of grooves formed at equal intervals on the outer peripheral surface.

Next, the supply of the slurry 7 to the wire 5 by the slurry supply mechanism 8D will be specifically described with reference to FIGS. 14 and 15. The slurry supply mechanism 8D is used for a liquid tank 53 as an accommodating portion for storing the slurry 7 and a plurality of wire routing for pulling the wire 5 into the liquid tank 53 and pulling it up from the liquid tank 53 to guide it to the workpiece 3. It is equipped with rollers 54a, 54b, 54c and 54d. Further, the liquid tank 53 is arranged between the sub-roller 27 located on the upstream side of the cut portion of the workpiece 3 and the cut portion of the workpiece 3, and has a stirring mechanism 55 for stirring the slurry 7 at the bottom. Have.

Next, a wafer will be produced by cutting the workpiece 3 using the multi-wire saw of the sixth embodiment. A polycrystalline silicon ingot (hereinafter referred to as an ingot) is used as the workpiece 3 at this time. This ingot is fixed on a stainless steel base plate 44 via a glass dummy 10 with an adhesive made of epoxy resin or the like, and the base plate 44 is mechanically fixed to the stage 11. When the wire supply mechanism 6 is driven, the wire 5 travels in a constant direction at a predetermined speed while maintaining a constant tension by the tension control roller 43. At this time, the main roller 24 and the sub roller 27 rotate synchronously at a rotation speed corresponding to the traveling speed of the wire 5. In the processing chamber 16, the wire 5 traveling between the main roller 24 and the sub roller 27 enters the liquid tank 53 via the wire routing roller 54a, and is sequentially guided by the wire routing rollers 54b and 54c to liquid. It is sent from the tank 53 to the outside. Since the slurry 7 is housed in the liquid tank 53, the slurry 7 is supplied to the wire 5 by guiding the wire 5 in the liquid tank 53. Then, the slurry 7 adhering to the wire 5 is carried to the cutting interface of the ingot by the traveling of the wire 5. Then, the bond of the silicon atom is broken by the wrapping action and the chemical action of the slurry 7, and the ingot is cut. Although not shown, a slurry storage / stirring tank for collecting the amount of slurry 7 introduced at the cutting interface of the ingot and a slurry storage / stirring tank for collecting the amount of slurry 7 introduced at the cutting interface of the ingot from the slurry storage / stirring tank 53 A mechanism to supply to is installed.

In the multi-wire saw according to the sixth embodiment, the viscosity is 150 mPa · s (25 ° C, shear rate 57.6 [s).^-1]) In the liquid tank 53 accommodating the slurry, 64 pieces of 0.1 mm diameter piano wire with a 0.39 mm pitch and a width of 25 mm, 10 m / sec, via wire routing rollers 54a, 54b, 54c, 54d. It was confirmed that sufficient slurry was uniformly applied to the wires to generate a transverse film (slurry film stretched between adjacent wires due to surface tension) when the wires were entered and sent out at the same speed as above, and the cutting process could be performed as usual.

As described above, according to the sixth embodiment, since the wire 5 is configured to pass through the liquid tank 53 arranged on the upstream side of the cut portion of the workpiece 3, it is sent out from the liquid tank 53. An appropriate amount of slurry 7 is attached to the wire 5, waste of slurry is eliminated, utilization efficiency of slurry is improved, and manufacturing cost can be suppressed. In addition, a large flow rate / high power slurry supply mechanism for supplying / circulating a large amount of slurry 7 becomes unnecessary, and the device becomes inexpensive. Further, since the wire 5 to which an appropriate amount of the slurry 7 is attached runs in the processing chamber 16, the scattering of the slurry 7 can be minimized. This means that the processing chamber 16 is less contaminated and that the labor of collecting the slurry 7 adhering to the wall surface and floor surface of the processing chamber 16 can be saved. Furthermore, since the liquid tank 53 in the sixth embodiment requires a smaller capacity than that of the conventional one, the temperature of the slurry 7 can be easily controlled and the amount of the slurry to be circulated can be minimized. The slurry composition in the slurry storage / stirring tank is stable, and the uniform dispersibility of the abrasive grains can be maintained. Therefore, the slurry composition is accurately controlled, and the slurry 7 in a state that is not much different from the initially adjusted state can be continuously supplied to the cutting interface of the workpiece 3, so that the wafer thickness varies and saw marks (scratches) occur. Etc. are suppressed and the processing quality is improved. Further, since the amount of the slurry 7 adhering to the opposite portion of the spirally wound wire 5 is reduced, the excess slurry 7 does not adhere to the sub roller 27 on the side close to the liquid tank 53, and the life due to the wear of the roller groove is reduced. It is possible to suppress the shortening of the period.

Further, the liquid tank 53 may be provided with a temperature control mechanism (not shown) for keeping the temperature constant, a filter (not shown) for removing chips from the workpiece 3, and the like, if necessary. The liquid tank 53 is preferably arranged close to the cut portion of the workpiece 3.

Embodiment 7. FIG. 16 is a partial external view of the multi-wire saw of the seventh embodiment, and FIG. 17 is a view taken along the arrow X in FIG. Since the slurry supply mechanism of the multi-wire saw of the seventh embodiment is different from that of the sixth embodiment and the other parts are the same, the description of the same part will be omitted. In the multi-wire saw according to the seventh embodiment, the slit supply mechanism 8E is provided with a liquid tank 53A that accommodates the slurry 7 and has a stirring mechanism 55, and the side surfaces of the liquid tank 53A that face each other 2 Slit-shaped passage holes 57a and 57b are provided in the side wall portions 56a and 56b, respectively. The positions where the passage holes 57a and 57b are provided are located below the liquid level of the slurry 7 when the slurry 7 is housed in the liquid tank 53A. Then, as shown in FIG. 17, the row of wires 7 spanning the main roller 24 and the sub roller 27 is arranged so as to pass through the slit-shaped passage holes 57a and 57b, and therefore, You will be guided through Slit 7 as you pass through the liquid tank 53A.

In such a slurry supply mechanism 8E, the wire 5 enters the liquid tank 53A through one of the passage holes 57a. At this time, since the slurry 7 is housed in the liquid tank 53A, the wire 5 comes into contact with the slurry 7 and the slurry 7 is supplied to the wire 5. The wire 5 to which the slurry 7 is attached is sent out from the passage hole 57b of the opposite side wall portion 56b to the outside of the liquid tank 53A, and the slurry 7 is carried to the cutting interface of the workpiece 3 by the traveling of the wire 5. There is a slight gap between the passage hole 57a and the wire 5, and the slurry 7 leaks from this gap. It is preferable to provide a recovery tray 58 at the lower part of the liquid tank 53A in order not to pollute the inside of the processing chamber 16 and to prevent the slurry 7 from adhering to the facing portion of the spirally wound wire 5.

As described above, according to the seventh embodiment, since the wire 5 does not travel on the wire routing rollers 54a, 54b, 54c, and 54d, the efficiency of using the slurry can be further improved. In addition, the wire tensioning work is reduced and the workability is improved.

As in the sixth embodiment, the liquid tank 53A includes a stirring mechanism 55, a temperature control mechanism for keeping the temperature constant (not shown), and a filter for removing ingot chips (not shown), if necessary. ) Etc. may be provided. Further, in the slurry supply mechanism 8E, the passage holes 57a and 57b are provided in the opposite side surface portions 56a and 56b, but the present invention is not limited to this, and if the wire 5 can be guided to the slurry 7 in the liquid tank 53A. , It may be provided on any side surface. For example, the cutting position of the workpiece 3 is arranged above the liquid tank 53A, and a roller for changing the direction is provided in the liquid tank 53A. You may let me.

Embodiment 8. Since the multi-wire saw of the eighth embodiment has a different slurry supply mechanism from the seventh embodiment and the other parts are the same, the description of the same part will be omitted. FIG. 18 is a diagram illustrating a side wall portion of the slurry supply mechanism 8F of the multi-wire saw according to the eighth embodiment of the present invention, FIG. 18 (A) shows a closed state, and FIG. 18 (B) shows an open state. It is a figure for demonstrating. In FIG. 18, the side wall portion 56c of the liquid tank 53A and the side wall portion (not shown) facing the side wall portion 56c are provided with an openable member 60 having a notch portion 59. The openable member 60 is composed of an upper side wall member 61a provided with a notch 59 and a lower side wall member 61b fixed to the liquid tank 53A. When the upper side wall member 61a is closed, the notch 59 forms the passage hole 57c as shown in FIG. 18A.

In such a slurry supply mechanism 8F, the workability is improved because it is not necessary to pass the wire 5 through the passing hole 57c every circumference during the preparatory work for spirally winding the wire 5 around the main roller 24 and the sub roller 27. That is, at the time of the winding preparation work of the wire 5, as shown in FIG. 5 (B), it is sufficient to remove the upper side wall member 61a and pass the wire 5 through the notch 59. When the workpiece 3 is cut, the upper side wall member 61a is closed again to form a passage hole 57c, the slurry 7 is supplied to the liquid tank 53A, and then the workpiece 3 is cut as described in the seventh embodiment. do it.

If the processing accuracy of the contact surfaces of the upper side wall member 61a, the lower side wall member 61b, and the liquid tank 53A is ensured, or if a soft member (polytetrafluoroethylene resin, etc.) is used, only mechanical fastening is required. Therefore, the leakage of slurry 7 can be sufficiently sealed.

1 base, 2 frames, 3 workpieces, 4 workpiece support mechanism, 5 wires, 6 wire supply mechanism, 7 slurry, 8,8A, 8B, 8C, 8D, 8E, 8F slurry supply mechanism, 9 side plates, 10 Dummy plate, 11 stage, 12 stage movable mechanism, 13 constant temperature bath, 14 side wall, 15 front wall, 16 processing chamber, 17 indoor thermometer, 18 hot plate, 19 chamber temperature regulator, 20 feeding rotation shaft, 21 winding rotation Shaft, 22 Wire feeding bobbin, 23 Wire winding bobbin, 24 Main roller, 25,25a, 25b, 26 Guide pulley, 27 Subroller, 28 Bobbin heater, 29 Slurry saucer, 30 Storage tank with heating mechanism, 31 Pump, 32 Heat insulation pipe, 33 slurry discharge part, 34 slurry storage tank, 35 slurry heating heater, 36,40 thermometer, 37,41 temperature controller, 38 pipe, 39 slurry heat insulation heater, 42 power supply, 43 tension control roller, 44 Base plate, 45 outlet, 46 slurry recovery drain pipe, 47 humidity control mechanism, 48 steam, 49 Humidifier, 50 hygrometer, 51 controller, 52 sheet member, 53,53A liquid tank, 54a, 54b, 54c, 54d wire routing roller, 55 stirring mechanism, 56a, 56b, 56c side wall, 57a, 57b, 57c Pass hole, 58 collection tray, 59 notch, 60 openable member, 61a upper side wall member, 61b lower side wall member.