JP2017220546A - Cutting method of workpiece - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably cut a cylindrical workpiece from the start of cutting to the end of cutting while supplying coolant to a processing point.SOLUTION: A fixed abrasive grain wire is plurally wound between a plurality of parallel main rollers 10A, 10B, 10C to form a wire row 11R, and a cylindrical workpiece W is cut off into a wafer shape by pressing the workpiece W against the wire row 11R while coolant C is supplied to the wire row 11R in a traveling state from coolant nozzles 20A, 20B. In that time, corresponding to changes of a workpiece cut length L from the start of cutting to end the of cutting the workpiece W, the positions of the coolant nozzles 20A, 20B to the workpiece W are changed in traveling direction of a wire 11, and the positions of the coolant nozzles 20A, 20B near the end of cutting the workpiece W are moved from a processing point of the workpiece W farther than the positions of the coolant nozzles 20A, 20B near the start of cutting the workpiece W.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a workpiece cutting method, and more particularly to a method of cutting a cylindrical workpiece using a fixed abrasive grain type wire saw.

  A silicon wafer, which is a substrate material for semiconductor devices, is completed by processing the ingot pulled up from the melt by the Czochralski method (CZ method) into a cylindrical shape and then performing each process such as slicing, lapping, and polishing. . In the ingot slicing process, a wire saw is mainly used, and a wire wound in a multiple manner between a plurality of parallel main rollers is run at high speed, and the ingot is brought to a target thickness by pressing the ingot against a running wire row. Sliced.

  As a cutting method using a wire saw, for example, Patent Document 1 describes a cutting method in which, when cutting an ingot while supplying slurry containing abrasive grains from a slurry nozzle, the slurry nozzle is moved along the peripheral surface of the ingot. ing. Patent Document 2 describes a method of moving a slurry supply position by changing the cutting length of a workpiece or by changing the angle formed between the wire and the outer periphery of the workpiece in a method of cutting a cylindrical workpiece using loose abrasive grains. ing. Furthermore, in Patent Document 3, in the method of cutting an ingot using loose abrasive grains, the nozzle position is set close to the ingot according to the change in the contact length between the ingot and the wire from the start of cutting to the end of cutting. A method is described in which the amount of slurry brought in per unit cutting contact length is always kept constant by changing the amount of slurry brought into the cut surface by the wire.

JP 61-121870 A JP-A-9-254142 JP-A-10-296717

  In recent years, in the slicing process using a wire saw, free abrasive grains using conventional slurry (mixed liquid of abrasive grains such as SiC and oil-based or water-soluble dispersant) for the purpose of improving productivity and reducing industrial waste. From the system, the generalization of the fixed abrasive system in which abrasive grains such as diamond grains are fixed on the surface of the wire by Ni electrodeposition, resin or the like is progressing.

  In the case of the fixed abrasive system, glycol-based or water-based coolant is used for the purpose of lubrication and cooling, but the viscosity of this coolant is lower than that of the slurry of the free abrasive system. For example, the viscosity of the free abrasive oily slurry is around 150 mPa · s, and the viscosity of the free abrasive water-soluble slurry is around 80 mPa · s, whereas the viscosity of the coolant is around 10 mPa · s. Therefore, in the fixed abrasive wire saw, if the coolant is supplied from the same position as that of the free abrasive method, the absolute amount of the coolant reaching the processing point while adhering to the wire is extremely small. Such a shortage of coolant supply affects wafer processing quality such as Warp, TTV, and surface roughness.

  In the cutting process using the fixed abrasive method, unlike the case of the loose abrasive method, the amount of abrasive particles taken in is constant (fixed to the wire) regardless of the coolant supply position from the nozzle, so the amount of abrasive particles is taken into account. There is no need to change the position of the nozzle.

  As described above, the coolant has a very low viscosity compared to the slurry and is less likely to adhere to the wire than the slurry. Therefore, in order to send as much coolant as possible to the machining point, the coolant supply position needs to be as close as possible to the machining point (ingot). It is advantageous in terms of lubrication and cooling that abundant coolant exists at the machining point of the workpiece.

  However, because the coolant jumps along the curved outer periphery of the ingot at the end of the ingot, if the coolant nozzle is too close to the ingot, the coolant will overflow from the space above the ingot, which causes the wire There is a problem that the flatness of the wafer deteriorates due to shaking.

  Accordingly, an object of the present invention is to provide a workpiece cutting method capable of stably cutting a cylindrical workpiece while supplying a coolant to a machining point from the start of cutting to the end of cutting.

  In order to solve the above-described problems, a workpiece cutting method according to the present invention is configured such that a wire row is formed by winding a plurality of fixed abrasive wires between a plurality of parallel main rollers, and a coolant nozzle is formed on the wire row in a running state. The workpiece is cut into a wafer by pressing the cylindrical workpiece against the wire row while supplying the coolant from the workpiece according to the change in the workpiece cutting length from the cutting start to the cutting end of the workpiece. The position of the coolant nozzle with respect to the workpiece is changed in the traveling direction of the wire, and the position of the coolant nozzle near the end of cutting the workpiece is set to be greater than the position of the coolant nozzle near the start of cutting the workpiece. It is characterized by being kept away from the machining point of the workpiece.

  In the fixed abrasive method, when the position of the coolant nozzle is fixed, the distance from the coolant supply position to the workpiece processing point becomes long at the start and end of cutting, and the coolant hardly reaches the processing point. However, the coolant nozzle position is changed so that the position of the coolant nozzle changes according to the workpiece cutting length, and the coolant nozzle position is brought close to the workpiece processing point at the start and end of cutting, so that sufficient coolant is supplied to the workpiece processing point. The processing quality of the wafer can be improved. Further, the present invention differs from the conventional method in which the position of the coolant nozzle is changed so that the distance to the machining point of the workpiece is always constant, the position of the coolant nozzle in the vicinity of the cutting end is different from the position of the coolant nozzle in the vicinity of the cutting end. Since the workpiece is further away from the processing point of the workpiece, it is possible to improve the processing quality of the wafer by preventing the fluctuation of the wire due to the influence of the splash of the coolant near the end of the workpiece cutting.

  In the present invention, it is preferable that the position of the coolant nozzle near the end of cutting of the workpiece is 20 mm or more away from the processing point of the workpiece than the position of the coolant nozzle near the start of cutting of the workpiece. According to this, it is possible to reliably prevent the wire from swinging due to the influence of the coolant splashing up near the end of cutting the workpiece.

  In the present invention, it is preferable that the position of the coolant nozzle at the time of center cutting of the workpiece is closer to the processing point of the workpiece than the position of the coolant nozzle in the vicinity of the cutting start and the cutting end of the workpiece. According to this, the coolant supply amount can be maximized at the center cutting of the workpiece having the maximum workpiece cutting length, and the machining quality of the workpiece at the center cutting can be ensured.

  In this invention, it is preferable that the distance along the said wire from the said coolant nozzle in the vicinity of the cutting end of the said workpiece | work to the processing point of the said workpiece | work is 100 mm or less. According to this, it is possible to prevent the deflection of the wire due to the influence of the coolant splashing while eliminating the shortage of coolant supply.

  In the workpiece cutting method according to the present invention, the first and second coolant nozzles are respectively disposed on one side and the other side in the traveling direction of the wire as viewed from the workpiece, and the workpiece from the cutting start to the cutting end is arranged. The positions of the first and second coolant nozzles with respect to the workpiece are changed in the traveling direction of the wire in accordance with a change in the workpiece cutting length, and the first and second coolant nozzles in the vicinity of the cutting end of the workpiece. It is preferable that the position is further away from the processing point of the workpiece than the positions of the first and second coolant nozzles in the vicinity of the start of cutting the workpiece. According to this, the present invention can be applied to each of the first and second coolant nozzles arranged on both sides in the traveling direction of the wire, eliminating the shortage of coolant supply and the coolant near the end of cutting the workpiece. It is possible to improve the processing quality of the wafer by preventing the fluctuation of the wire due to the influence of the jumping up of the wafer.

  ADVANTAGE OF THE INVENTION According to this invention, the cutting method of the workpiece | work which can cut | disconnect a cylindrical workpiece | work stably can be provided, supplying a coolant to a process point from the cutting start to the cutting end.

FIG. 1 is a perspective view schematically showing a configuration of a wire saw according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the wire saw 1 of FIG. 1 viewed from the lateral direction. FIG. 3 is a schematic diagram for explaining changes in the positions of the coolant nozzles 20A and 20B. FIG. 4 is a graph showing changes in the positions of the coolant nozzles 20A and 20B. The horizontal axis is the workpiece feed position, and the vertical axis is the distance D along the wire 11 from the coolant nozzles 20A and 20B to the machining point of the workpiece W. Is shown. FIGS. 5A to 5C are schematic diagrams and graphs for explaining wafer processing conditions according to Comparative Examples 1 and 2 and Examples. FIG. 6A is a graph showing TTVs of Comparative Examples 1 and 2 and Examples, and FIG. 6B is a table showing average values and standard deviations of TTVs. Fig.7 (a) is a graph which shows Warp of the comparative examples 1 and 2 and an Example, FIG.7 (b) is a table | surface which shows the average value and standard deviation of Warp.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a perspective view schematically showing a configuration of a wire saw according to an embodiment of the present invention.

  As shown in FIG. 1, the wire saw 1 is formed by winding three parallel main rollers 10A, 10B, and 10C and a single wire 11 between the main rollers 10A, 10B, and 10C. The wire row 11R, coolant nozzles 20A, 20B, 21A, and 21B that supply coolant to the wire row 11R in the traveling state, and a lifting device 18 that lifts and lowers the workpiece W are provided.

  The main rollers 10A, 10B, and 10C are grooved rollers, and a large number of annular grooves are formed at a constant pitch on the outer peripheral surface. The first and second main rollers 10A, 10B are provided at the same height, and the third main roller 10C is provided below them.

  The wire 11 is spirally wound between the three main rollers 10A, 10B, and 10C, and is wound around the groove of each main roller. Accordingly, a wire row 11R having a constant pitch is formed between the first and second main rollers 10A and 10B, and the workpiece W is cut by pressing the workpiece W against the wire row 11R. The workpiece W is, for example, a columnar single crystal silicon block, which is a silicon single crystal ingot grown by the CZ method, which is ground to a constant length and then processed to a certain length.

  The wire saw 1 in this embodiment is a fixed abrasive method, and the wire 11 is a fixed abrasive wire in which abrasive grains such as diamond grains are fixed on the surface of the core wire. The wire 11 wound around one reel 12A is repeatedly wound around the main rollers 10A, 10B, and 10C via the guide roller 13, and then wound around the second reel 12B via the guide roller 13. Taken. The reel 12A is a wire supply reel on which a new wire is wound, and the reel 12B is a wire collection reel that winds up a used wire. These reels 12A and 12B are driven by a torque motor (not shown).

  The tension adjusting mechanism 14A is provided on the wire travel path between the reel 12A and the first main roller 10A, and is a means for adjusting the tension of the wire 11 on the reel 12A side. The tension adjusting mechanism 14B is a reel 12B. And a means for adjusting the tension of the wire 11 on the reel 12B side, which is provided on the wire travel path between the first main roller 10C and the third main roller 10C. Each of the tension adjusting mechanisms 14A and 14B includes a dancer roller 15 around which a wire 11 is wound, a dancer arm 16 that rotatably supports the dancer roller 15, and an actuator 17 that supports the dancer arm 16. An appropriate tension is applied to the wire 11 using the driving force of the actuator 17.

  The fixed abrasive method employs a back-and-force method in which the wire 11 is gradually fed while the traveling direction of the wire 11 is periodically reversed. By rotating the main rollers 10A, 10B, 10C alternately forward and reverse, the wire 11 reciprocates in the direction from one reel 12A toward the other reel 12A or in the opposite direction. At this time, the new wire can be continuously supplied gradually by increasing the feed amount of the wire 11 from the reel 12A more than the feed amount from the reel 12B. The wire 11 reciprocates by being wound at a constant linear velocity in the direction from the first reel 12A toward the second reel 12B or in the opposite direction, and the workpiece W is cut by the cross-seed movement of the wire 11 as described above. Is done.

  The coolant liquid is supplied from the coolant nozzles 20A, 20B, 21A, and 21B to the wire 11 being cut. The coolant nozzles 20A, 20B, 21A, and 21B have a large number of nozzle holes corresponding to the wire rows, and the coolant liquid flows down in a curtain shape and is discharged so as to be applied to the running wire rows. The coolant nozzles 20 </ b> A, 20 </ b> B, 21 </ b> A, and 21 </ b> B are disposed above the wire row 11 </ b> R, and supply the temperature adjusted coolant liquid supplied from the tank via the chiller to the wire 11.

  The workpiece W is disposed above the wire saw 1 and is attached to the lifting device 18. When the lifting device 18 gradually lowers the workpiece W and presses the workpiece W against the wire row 11R, the workpiece W is gradually cut from the lower end toward the upper end. At that time, running resistance and heat generation of the wire 11 can be reduced by cutting while supplying coolant from the coolant nozzles 20A, 20B, 21A, 21B to the processing point of the workpiece W via the wire 11. Thereby, the processing quality of the workpiece | work W can be improved.

  FIG. 2 is a cross-sectional view of the wire saw 1 of FIG. 1 viewed from the lateral direction.

  As shown in FIG. 2, four coolant nozzles 20A, 20B, 21A, and 21B are provided above the wire row 11R and on both sides of the workpiece W. The coolant nozzle needs to be arranged on the near side in the traveling direction of the wire 11 with respect to the workpiece W. However, since the wire 11 travels in both directions, the two coolant nozzles 20A and 20B and 21A and 21B are formed on the workpiece W. It is arranged on each side. That is, when the wire 11 is traveling in the direction from the main roller 10A toward the main roller 10B, the coolant C is supplied from the coolant nozzles 20A and 21A provided on the left side (one side) of the workpiece W and travels in the opposite direction. In this case, the coolant C is supplied from the coolant nozzles 20B and 21B provided on the right side (the other side), and the coolant C is supplied to the machining point of the workpiece W together with the wire 11 in the traveling state.

  Of the four coolant nozzles 20A, 20B, 21A, 21B, the coolant nozzles 21A, 21B on the relatively outer side (in the direction away from the workpiece W) are provided directly above the main rollers 10A, 10B, respectively. The coolant nozzles 21A and 21B on the inner side (in the direction approaching the workpiece W) are provided closer to the workpiece W than the coolant nozzles 20A and 20B, respectively. The coolant nozzles 21A and 21B are fixed nozzles whose positions are fixed, whereas the coolant nozzles 20A and 20B are movable nozzles whose positions can be moved in the horizontal direction. Although the movement mechanism of coolant nozzle 20A, 20B is not specifically limited, For example, it can be set as the structure which combined the drive motor and the encoder for movement position confirmation. The coolant nozzles 20 </ b> A, 20 </ b> B, 21 </ b> A, 21 </ b> B operate according to instructions from the control unit 22. The main rollers 10A, 10B, 10C and the lifting device 18 also operate according to instructions from the control unit 22.

  The coolant nozzles 20A and 20B are movable in the traveling direction (the overhead line direction) of the wire 11, and can make the coolant supply position approach (black arrow) or separate (white arrow) from the workpiece W. The flow rate of the coolant C from the coolant nozzles 20A and 20B is constant, but the workpiece W is changed by changing the position of the coolant nozzles 20A and 20B according to the change of the workpiece cutting length L from the start of cutting of the workpiece W to the end of cutting. The coolant supply amount to the machining point can be adjusted. The workpiece cutting length L can be detected from the positional relationship between the wire 11 and the workpiece W. For example, the workpiece cutting length L can be easily determined from the distance Y (feed position) from the upper end of the workpiece W to the wire 11 and the diameter of the workpiece W. .

  Since the coolant used in the fixed abrasive method has a low viscosity, if the distance D from the position of the coolant nozzles 20A, 20B to the processing point of the workpiece W is far away, the coolant C reaches the processing point of the workpiece W. hard. Although the coolant supply amount to the processing point can be increased to some extent by bringing the coolant nozzles 20A and 20B close to the workpiece W, the cross-sectional shape is circular, so that the start and end of cutting are compared with the central portion of the workpiece W. In this case, the distance D to the machining point is far away, resulting in insufficient coolant supply, so that the amount of coolant that should exist in a large amount between the workpiece and the fixed abrasive wire is very small. If the coolant supply is insufficient, the friction between the fixed abrasive wire and the workpiece W, that is, at the processing point increases, and the straightness of the wire 11 becomes unstable, resulting in increased damage to the wafer surface and frictional heat. As a result of the Warp deterioration due to the expansion of the workpiece W and the main rollers 10A to 10C due to expansion of the workpiece W, the falling of the abrasive grains due to direct damage to the fixed abrasive wire due to the reduction in the lubrication effect, breakage of the wire, etc. Problems arise.

  However, in this embodiment, movable coolant nozzles 20A and 20B are employed, and the coolant is supplied from an appropriate position according to the processing position of the workpiece W. The position of the coolant nozzles 20A, 20B at the end can be brought close to the workpiece W, and therefore, the shortage of coolant supply to the machining point of the workpiece W at the start or end of cutting can be solved.

  FIG. 3 is a schematic diagram for explaining changes in the positions of the coolant nozzles 20A and 20B. FIG. 4 is a graph showing changes in the positions of the coolant nozzles 20A and 20B. The horizontal axis is the workpiece feed position, and the vertical axis is along the wire 11 from the coolant nozzles 20A and 20B to the processing point of the workpiece W. The distance D is shown.

As shown in FIG. 3, the positions of the first and second coolant nozzles 20 </ b> A and 20 </ b> B are set at the machining position of the workpiece W while maintaining a symmetrical positional relationship with respect to the vertical reference axis Z passing through the center of the workpiece W. Will change accordingly. When defining the positional relationship between the coolant nozzles 20A, 20B and the workpiece W with respect to the vertical reference axis Z, the coolant nozzles 20A, 20B approach the workpiece W at the beginning of cutting the workpiece W, but as the machining proceeds. Gradually move away from the workpiece W, and move farthest from the workpiece W when the workpiece W is cut at the center. As the processing further progresses, the position of the coolant nozzles 20A, 20B gradually approaches the workpiece W, but does not approach as much as at the start of cutting, and the position of the coolant nozzles 20A, 20B at the end of cutting is higher than that at the beginning of cutting. Move away from W. That is, when the distance X _A at the start of cutting the workpiece W, the distance X _B at the center cutting of the workpiece W, and the distance X _C at the end of cutting, the relationship X _A <X _C <X _B is established. The positions of the coolant nozzles 20A and 20B are controlled.

  In this way, the coolant nozzles 20A and 20B at the start and end of cutting are closer to the workpiece W than at the center cutting of the workpiece W, thereby supplying coolant to the machining point of the workpiece W at the start and end of cutting. The shortage can be resolved.

On the other hand, as shown in FIGS. 3 and 4, the distance D along the wire 11 from the position of the coolant nozzles 20A, 20B to the outer peripheral surface (processing point) of the workpiece W is somewhat longer at the beginning of cutting, and processing is performed. It gradually becomes shorter as it advances, and becomes the shortest when the workpiece W is cut at the center (the workpiece cutting length L is maximum). As the processing further proceeds, the distance D gradually increases, and the distance D at the end of cutting becomes longer than at the start of cutting. That is, the position of the coolant nozzles 20A and 20B at the end of cutting is not as close to the machining point of the workpiece W as at the start of cutting. When the distance D _A at the start of cutting, the distance D _B at the center cutting, and the distance D _C at the end of cutting, the relationship of D _B <D _A <D _C is established. The graph of FIG. 4 shows such a change in distance D linearly.

  When the position of the coolant nozzles 20A, 20B is set very close to the workpiece W at the end of cutting the workpiece W, a large amount of coolant jumps up on the outer peripheral surface on the upper side of the workpiece W and vibrates the wire 11, thereby causing TTV, The processing quality of a wafer such as Warp deteriorates. However, it is possible to suppress the splashing of the coolant by moving the positions of the coolant nozzles 20A and 20B at the end of cutting away from the processing point of the workpiece W than at the start of cutting. Therefore, it is possible to prevent the wire 11 from swinging due to the influence of the coolant splashing, and to improve the wafer processing quality.

  Further, since the coolant nozzles 20A and 20B are closest to the machining point when the workpiece W is at the center cutting position where the workpiece cutting length L is maximized, the coolant supply amount can be maximized when the workpiece cutting length L is maximized. it can. Therefore, the work quality of the work when the work W is cut at the center can be ensured.

  As described above, in the work cutting method according to the present embodiment, when the cylindrical work W is cut using the fixed-abrasive wire saw 1, the work is supplied to the wire row 11R according to the change in the work cutting length L. As the coolant supply position is changed, the coolant supply position near the end of cutting of the workpiece W is further away from the workpiece W than the coolant supply position at the same workpiece cutting length near the start of cutting. The workpiece W can be stably cut while supplying a sufficient amount of coolant to the machining point of the workpiece W from the end of cutting to the end of cutting, and the wire 11 swings due to the splash of coolant near the end of cutting of the workpiece W. Can improve the processing quality of the wafer.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. Needless to say, it is included in the range.

  For example, in the above-described embodiment, the silicon single crystal ingot is given as a representative example of the workpiece. However, the present invention is not limited to this, and various cylindrical workpieces can be targeted. Further, the wire saw 1 may be constituted by, for example, a wire row that is wound in a multiple manner between two main rollers, and the configuration is not particularly limited.

  A silicon single crystal ingot having a diameter of 300 mm was used as a work, and the work was cut using a fixed abrasive type wire saw, and then TTV and Warp of the wafer were evaluated. The core wire diameter of the fixed abrasive wire used in the wire saw is 0.12 mm, the wire tension is 20 to 50 N, the wire traveling speed is 400 to 900 m / min (reciprocating traveling), the coolant type is glycol, and the coolant supply amount is 100 L. / Min, the temperature of the coolant was 18-26 ° C.

  FIGS. 5A to 5C are schematic diagrams and graphs for explaining wafer processing conditions according to Comparative Examples 1 and 2 and Examples.

  As shown in FIG. 5A, in the first comparative example, the positions of the coolant nozzles 20A and 20B are fixed, thereby changing the distance from the coolant nozzles 20A and 20B to the outer peripheral surface of the ingot within a range of 230 mm to 80 mm. This is the case. Moreover, as shown in FIG.5 (b), the comparative example 2 is a case where a coolant nozzle is moved so that the distance from coolant nozzle 20A, 20B to the outer peripheral surface of an ingot may become fixed at 100 mm.

Further, as shown in FIG. 5C, in the embodiment, the positions of the coolant nozzles 20A and 20B are moved, but the distance from the coolant nozzles 20A and 20B to the outer peripheral surface of the ingot is completely constant as in the comparative example 2. Rather, in order to prevent the coolant from jumping up near the end of cutting, it was moved away from the outer peripheral surface of the ingot than at the beginning of cutting. More specifically, the distance D _A = 80 mm at the start of cutting A, the distance D _B = 30 mm at the middle board B, and the distance D _C = 100 mm at the cutting end C. That is, the positions of the coolant nozzles 20A and 20B at the cutting end C were set 20 mm farther from the machining point of the workpiece W than the positions of the coolant nozzles 20A and 20B at the cutting start A.

  Then, TTV and Warp of the wafer samples of Comparative Examples 1 and 2 and Examples were measured. TTV (Total Thickness Variation) is a parameter indicating a difference between the maximum value and the minimum value of the thickness in the wafer surface. Warp is a parameter that represents the shape of the wafer in a natural state where the wafer is not vacuum-sucked. The measurement surface uses the thickness center plane, and the reference plane uses the thickness center plane best-fit surface. It is defined as the difference between the maximum value and the minimum value obtained by subtracting the reference surface from the surface. For the measurement of TTV and Warp, a flatness measuring device SBW manufactured by Kobelco Research Institute was used.

  FIG. 6A is a graph showing TTVs according to Comparative Examples 1 and 2 and Examples, and FIG. 6B is a table showing average values and standard deviations of TTVs.

  As shown in FIGS. 6A and 6B, the number of wafer samples in Comparative Example 1 was 133, the TTV average value (μm) was 14.78, and the standard deviation was 2.31. The number of wafer samples in Comparative Example 2 was 136, the TTV average value (μm) was 13.25, and the standard deviation was 2.03.

  On the other hand, the number of wafer samples in the example was 141, the TTV average value (μm) was 12.09, and the standard deviation was 1.33.

  As described above, the average TTV value of Comparative Example 2 is lower than that of Comparative Example 1 and the flatness of the wafer is good, but the TTV average value of Example is further lower than that of Comparative Example 2 and is higher than that of Comparative Examples 1 and 2. It was also found that the flatness of the wafer is even better.

  FIG. 7A is a graph showing Warp according to Comparative Examples 1 and 2 and Examples, and FIG. 7B is a table showing the average value and standard deviation of Warp.

  As shown in FIGS. 7A and 7B, the number of wafer samples in Comparative Example 1 was 133, and the Warp average value (μm) was 14.37, and the standard deviation was 1.92. The number of wafer samples in Comparative Example 2 was 136, and the Warp average value (μm) was 13.21 and the standard deviation was 1.84.

  On the other hand, the number of wafer samples in the example was 141, and the Warp average value (μm) was 11.94, and the standard deviation was 1.38.

  Thus, the Warp average value of Comparative Example 2 is lower than that of Comparative Example 1 and the flatness of the wafer is good, but the Warp average value of Example is further lower than that of Comparative Example 2 and is higher than that of Comparative Examples 1 and 2. It was also found that the flatness of the wafer is even better.

DESCRIPTION OF SYMBOLS 1 Wire saw 10A, 10B, 10C Main roller 11 Wire 11R Wire row 12A, 12B Reel 13 Guide roller 14A, 14B Tension adjustment mechanism 15 Dancer roller 16 Dancer arm 17 Actuator 18 Lifting device 20A, 20B Coolant nozzle (movable)
21A, 21B Coolant nozzle (fixed type)
22 Control part C Coolant D Distance from coolant nozzle to workpiece machining point L Work cutting length W Work Y Distance from workpiece upper end to wire Z Vertical reference axis

Claims (5)

A plurality of fixed abrasive wires are wound around a plurality of parallel main rollers to form a wire row, and a cylindrical workpiece is pushed into the wire row while supplying coolant from the coolant nozzle to the wire row in the running state. It is a method of cutting the workpiece into a wafer by hitting,
The position of the coolant nozzle with respect to the workpiece is changed in the traveling direction of the wire in accordance with a change in the workpiece cutting length from the start of cutting to the end of cutting of the workpiece, and the position of the coolant nozzle in the vicinity of the end of cutting of the workpiece. The workpiece cutting method, wherein the workpiece is moved away from the machining point of the workpiece than the position of the coolant nozzle in the vicinity of the cutting start of the workpiece.   The workpiece cutting method according to claim 1, wherein the position of the coolant nozzle near the end of cutting the workpiece is 20 mm or more away from the processing point of the workpiece than the position of the coolant nozzle near the start of cutting the workpiece. .   The position of the coolant nozzle at the time of cutting the center of the workpiece is closer to the processing point of the workpiece than the position of the coolant nozzle near the start of cutting and the end of cutting of the workpiece. How to cut the workpiece.   The work cutting method according to any one of claims 1 to 3, wherein a distance along the wire from the coolant nozzle to a machining point of the work in the vicinity of a cutting end of the work is 100 mm or less. The first and second coolant nozzles are arranged on one side and the other side in the traveling direction of the wire as viewed from the workpiece, respectively.
The position of the first and second coolant nozzles with respect to the workpiece is changed in the traveling direction of the wire in accordance with a change in the workpiece cutting length from the start of cutting to the end of cutting of the workpiece, and in the vicinity of the end of cutting of the workpiece. 5. The positions of the first and second coolant nozzles at the same distance from the machining point of the workpiece are made farther from the positions of the first and second coolant nozzles near the start of cutting the workpiece, respectively. The work cutting method according to any one of the above.