JP4892278B2 - Work cutting method and wire saw - Google Patents

Description

  The present invention relates to a workpiece cutting method using a wire saw that cuts and feeds a workpiece such as a semiconductor ingot or the like to a wire group constituted by cutting wires.

  Conventionally, a wire saw is known as means for cutting a workpiece into a wafer shape. A wire saw is stretched in a state where a large number of wires are arranged by winding a cutting wire between a plurality of guide rollers, and loose abrasive grains are formed on the wire group while driving the wire group at a high speed in the axial direction. In this state, the workpiece W is cut and fed into the wire group in a direction perpendicular to the axial direction of the cutting wire, thereby moving the workpiece into a wafer shape. It is configured to cut out many at the same time (Patent Document 1).

As an operation using this type of wire saw, for example, when cutting a silicon wafer for a solar cell, a large number of silicon wafers are formed by cutting and feeding an ingot to a wire group while driving the cutting wire in only one direction. Cutting out is done. In other words, by driving the cutting wire in only one direction, it is possible to suppress the deterioration due to wear of the cutting wire, thereby maintaining the sharpness of the cutting wire, thereby efficiently producing a silicon wafer with high cutting surface accuracy. I try to cut it out.
Japanese Patent Laid-Open No. 11-10511

  In the cutting operation of silicon wafers for solar cells as described above, in recent years, it has been required to cut out thinner silicon wafers. As a result, wire saws used in such operations have a narrow pitch of wires. Is underway.

  However, as the pitch of the wire group becomes narrower, the so-called linking phenomenon in which adjacent wires of the wire group are attracted to each other through the slurry is likely to occur. For example, the linking phenomenon remains generated. As a result of the cutting operation of the silicon wafer, it is conceivable that the thickness accuracy of the silicon wafer is impaired.

  The present invention has been made in view of the above circumstances, and an object thereof is to cut out a thin wafer more accurately and efficiently.

In order to solve the above-described problems, the present invention provides a cutting wire drawn from a wire feeding device that is wound around a plurality of guide rollers and wound around a wire winding device so that the gap between the guide rollers is reduced. A method of cutting a workpiece using a wire saw in which a group of wires in which a plurality of wires are arranged is formed, wherein the wire is fed from the wire feeding device, and the wire is wound by the wire winding device. In addition to this step of driving the wire at a constant speed in one direction, and cutting the workpiece by relatively cutting and feeding the workpiece in a direction perpendicular to the wire axis direction with respect to the wire in the one-way drive state, This step is performed before or during this step, and is a vibration for urging the elimination of the linking phenomenon that the wires are attracted to each other in the wire group. In order to grant the wire, having the temporarily reduce the driving speed of the wire while maintaining the wire driving direction in one direction driven state, or a wire linking solve for step Ru temporarily stops the driving of (Claim 1).

  According to this method, since the workpiece is basically cut in the wire driving state in which the wire group is driven in one direction (this step), deterioration due to wear of the cutting wire is suppressed, and the workpiece is maintained while maintaining a high sharpness. Cutting can proceed. In addition, in addition to this step, the linking elimination step is performed before or during this step. Therefore, when a so-called linking phenomenon occurs in the wire group, the elimination can be promoted. Therefore, it is possible to proceed with the cutting operation using an appropriate wire group that does not involve the linking phenomenon while enjoying the above-described effect of maintaining the sharpness of the wire.

In particular, the re trunking eliminates a step, the reduced while maintaining the wire driving direction in one direction driven state the drive speed temporarily, or so to stop the driving, the driving speed of the thus wire units vary As a result, a change in the vibration state of the wire is caused, and the elimination of the linking phenomenon is promoted. In addition, the cutting wire tends to vibrate (resonate) more easily when driven at a lower speed than the high-speed driving state at the time of cutting the workpiece because of the relationship with the natural frequency. Is temporarily driven at a low speed, the vibration of the wire group is appropriately amplified, and as a result, the elimination of the linking phenomenon is promoted.

In each method described above, it is preferable that only perform the linking solve for step a predetermined time period from a position to start the cut of the workpiece, and then to start the present process with respect to the wire (claim 2 ).

  According to this method, it is possible to eliminate the linking phenomenon at the cutting stage of the wire group with respect to the workpiece. The “predetermined period” may be either the workpiece cutting feed amount or time.

Further, in each of the above methods, the main step includes a step of detecting a cutting feed position of the workpiece with respect to the wire group, and the main step is performed when the detected feed position reaches a specific feed position. May be interrupted to execute the linking elimination process (claim 3 ).

  According to this method, it is possible to execute the linking elimination process at a specific feed position of the workpiece.

In each method described above, the in this step, the linking eliminate a step a plurality of times, may be performed intermittently (claim 4).

  According to this method, it is possible to eliminate the linking phenomenon more reliably.

On the other hand, a wire saw according to the present invention includes a plurality of guide rollers, a wire feeding device that feeds a cutting wire to the guide rollers, and a wire winding device that winds the wires from the guide roller, and the wire feeding device. A wire group in which a plurality of wires are arranged between the guide rollers is formed by winding the wire fed out from the device around the guide roller and winding the wire around the guide roller. In a wire saw in which a wire group is driven in an axial direction and the workpiece is cut and fed to the wire group in this wire driving state, the wire group is cut in a direction orthogonal to the axial direction. A cutting and feeding means for relatively cutting and feeding the workpiece, and a workpiece feeding position by the cutting and feeding means, which are set in advance. Storage means for storing the specific feed position, feed position detection means for detecting the feed position by the cutting feed means, and drive control for controlling the operation of the feeding device and wire take-up device to drive the wire group and means, wherein the drive control means, wherein in response to the detection of the feed position of the workpiece by the feed position detecting means, wherein in the feed position other than the specific feed position, while prior Symbol unwinding the wire from the wire feeding device The wire is wound by the wire winding device so that the wire is driven in one direction at a constant speed, and the wire driving direction in the one-way driving state is maintained at the specific feed position. temporarily reduces the driving speed of the wire while the, or the driving of the wire feeding said wire in order to stop device and And it controls the operation of the ear retractor (claim 5).

  According to this configuration, it is possible to automate the workpiece cutting method according to the first aspect of the wire saw.

  According to the cutting method using the wire saw of the present invention, the workpiece is cut by driving the wire group in one direction (one-way driving state) in this step, and in addition to this step, the so-called linking phenomenon is eliminated. Since the linking elimination process for temporarily switching the wire driving state to a state different from the one-way driving state in order to impart vibration for urging to the wire is performed, the effect of maintaining the sharpness of the wire group It is possible to proceed with the cutting work using a more appropriate wire group without linking phenomenon. Therefore, a thin wafer such as a silicon wafer for solar cells can be cut out more accurately and efficiently.

  A preferred embodiment (first embodiment) of the present invention will be described with reference to the drawings.

  FIG. 1 is an overall configuration diagram of a wire saw according to the present invention. The wire saw shown in this figure includes a pair of wire feeding / winding devices 10A and 10B, guide pulleys 12A and 12B, guide pulleys 14A and 14B, guide pulleys 16A and 16B, wire tension adjusting devices 18A and 18B, guide pulleys 22A and 22B. , And four guide rollers 24A, 24B, 26A, 26B.

  The guide rollers 24A and 24B are arranged at the same height position, and the guide rollers 26A and 26B are arranged at positions below the guide rollers 24A and 24B, respectively, so that the guide roller 26A is rotationally driven by the drive motor 25. It has become.

  Each of the wire feeding / winding devices 10A and 10B includes bobbins 9A and 9B around which a wire W for cutting is wound, and bobbin driving motors 11A and 11B that rotationally drive the bobbins. The wire W fed from the bobbin 9A of one wire feeding / winding device 10A is hung in the order of the guide pulleys 12A, 14A, 16A, the pulley 20A of the wire tension adjusting device 18A, and the guide pulley 22A, and further the guide roller 24A. 24B, 26B, 26A, guide pulley 22B, wire tension adjustment after being wound (wound) around the guide rollers a number of times while being fitted into guide grooves (not shown) on the outer peripheral surfaces of guide rollers 22B, 26B, 26A The pulley 20B of the device 18B and the guide pulleys 16B, 14B, and 12B are hung in this order, and are wound around the bobbin 9B of the other wire feeding / winding device 10B, and are appropriately applied to the wire W by both wire tension adjusting devices 18A and 18B. Tension is applied. Then, the rotation driving direction of the guide roller 26A by the drive motor 25 and the rotation driving direction of the bobbins 9A and 9B by the bobbin driving motors 11A and 11B are switched between forward and reverse, so that the wire W is fed out from the bobbin 9A and bobbins. The state can be switched between a state wound around 9B and a state where the wire W is fed from the bobbin 9B and wound around the bobbin 9A.

  That is, in this wire saw, a wire group in which a large number of wires W are stretched in parallel with each other is formed between the guide rollers 24A and 24B, and these wire groups can be driven back and forth in the axial direction. Yes. In this embodiment, the drive motor 25 and the bobbin drive motors 11A and 11B are composed of servo motors.

  Above the wire W stretched between the guide rollers 24A and 24B, a workpiece feeding device 30 (corresponding to the cutting feeding means according to the present invention) for moving a cylindrical workpiece (ingot) 28 is provided. . The workpiece feeding device 30 includes a workpiece holding unit 32 and a workpiece feeding motor 34. The workpiece holding unit 32 holds the workpiece 28 in a direction in which a target crystal orientation can be obtained based on the crystal axis. The workpiece feeding motor 34 is combined with a ball screw (not shown), 32 and the workpiece 28 are moved up and down integrally (that is, cut and fed). In this embodiment, the work feed motor 34 is composed of a servo motor like the drive motor 25 and the like, and also serves as a feed position detecting means according to the present invention for detecting the cutting feed position of the work 28.

  Above the wire W stretched between the guide rollers 24A and 24B, slurry supply devices 36A and 36B are provided at positions on the left and right sides of the work 28. These slurry supply devices 36 </ b> A and 36 </ b> B simultaneously supply a processing liquid (slurry) in which abrasive grains are mixed to each wire W that is driven at high speed, and attach this to the surface of the wire W.

  Therefore, in this wire saw, a large number of wires W stretched between the guide rollers 24A and 24B are simultaneously driven in the longitudinal direction at a high speed, and the machining fluid is supplied to the wires W from the slurry supply devices 36A and 36B. By cutting and feeding the workpiece 28 downward with respect to these wires W, a large number of wafers (thin pieces) are simultaneously cut out from the workpiece 28 at the same time.

  The wire saw has a controller 40 as shown in FIG. The controller includes a main control unit 41 composed of a CPU (corresponding to drive control means according to the present invention), a storage unit 42 composed of various memories (corresponding to storage means according to the present invention), and a motor control unit composed of a servo amplifier. 43 is included.

  The main control unit 41 comprehensively controls the driving of the wire saw, and drives the wire W in accordance with a machining program stored in the storage unit 42, that is, at a driving speed and a driving direction programmed in advance, and is programmed in advance. A control signal is output to the motor control unit 43 so as to cut and feed the workpiece 28 at the cut feed speed.

  Hereinafter, the cutting operation control of the workpiece 28 by the main control unit 41 will be described together with its operation according to the flowchart of FIG.

  The workpiece 28 is held by the workpiece holding portion 32, and the workpiece 28 (work holding portion 32) is set at an initial position, for example, a position separated from the wire W (wire group) as shown in FIG. Then, this flowchart starts.

  First, the main control unit 41 drives the drive motor 25 and the bobbin drive motors 11A and 11B at a low speed and switches the drive direction at regular time intervals, thereby driving the wire W forward and backward (step S1). That is, a state in which the wire W is wound out by the other side of the wire feeding / winding device 10B (referred to as a forward drive state of the wire W) while being fed from the wire feeding / winding device 10A on one side, On the contrary, a state in which the wire W is taken out by the wire feeding / winding device 10A on the one side (referred to as a backward driving state of the wire W) while feeding the wire W from the wire feeding / winding device 10B on the other side alternately. Switch. At this time, the driving speed of the wire W is set to a sufficiently low speed as compared with a forward driving state of the wire W described later.

  Next, the slurry supply devices 36A and 36B are driven to start supplying the slurry, and the workpiece feed motor 34 is driven to start cutting and feeding the workpiece 28 at a constant speed (step S2). Then, the workpiece 28 starts to be cut. If the wire W is cut into the work 28 while being advanced and retracted at a low speed in this way, even if a so-called linking phenomenon occurs in which the adjacent wires W are attracted to each other through the slurry, the phenomenon is quickly eliminated. Thus, the cutting of each wire W with respect to the workpiece 28 is performed appropriately and stably. That is, when the wire W is driven forward / backward as described above, a light impact is applied to the wire W at the time of forward / backward drive switching, and the vibration state of the wire W changes along with the speed change of the wire W accompanying the forward / backward switching. Then, the slurry adhering to the wires falls off due to the impact or the like, and the separation of the wires W that are stuck to each other through the slurry is promoted. Further, the wire W is driven at a low speed as described above, so that the wire W is stably cut into the workpiece 28.

  After the wire W has been cut into the workpiece 28, when the workpiece 28 reaches a predetermined cutting and feeding position (YES in step S3), that is, the workpiece 28 reaches the predetermined cutting and feeding position based on the output signal from the workpiece feeding motor 34. When this is detected, the drive state of the wire W is switched from the advance / retreat drive state to the advance drive state, and the drive speed of the wire W is accelerated to a predetermined speed (step S4). Is set (step S5).

  Then, the cutting operation is advanced by feeding the workpiece 28 at a constant feeding speed by the workpiece feeding device 30 with the driving speed of the wire W kept at the predetermined speed, and when the workpiece 28 reaches a specific cutting feeding position (step If YES in S6), the wire W is driven forward and backward for the set number of times (step S7). In this embodiment, when the work 28 reaches the position where the cutting feed has advanced by, for example, 5 mm from the time when the driving state of the wire W is switched to forward driving (the time of switching in step S4), the wire W is driven forward and backward one to several times. . In other words, when the linking phenomenon has not yet been solved by temporarily driving the wire W to advance and retreat one to several times while advancing the cutting of the workpiece 28 while driving the wire W forward, the solution is solved. Will be promoted.

  Thereafter, the wire W is again switched to the forward drive state, the cutting of the workpiece 28 is advanced while driving the wire W in this forward drive state, and it is determined whether or not the counter value has reached the set value “N” ( Step S9) If NO is determined here, the counter value is incremented by "1" and the process returns to Step S6 (Step S11). That is, while the wire W is driven in the forward drive state to advance the cutting of the work 28, the wire W is temporarily switched to the forward / backward drive state every time the cutting and feeding of the work 28 advances 5 mm, thereby eliminating the linking phenomenon. It is supposed to prompt.

  If YES is determined in step S9, it is further determined whether or not the work 28 has reached a predetermined cutting end position based on the output signal from the work feed motor 34. If YES is determined here, the driving of the wire W is determined. Is stopped, and a series of cutting work of the workpieces 28 is finished.

  As described above, in this wire saw (work cutting method), the cutting work of the work 28 is advanced by cutting and feeding the work 28 while driving the wire W in the forward (one-way) driving state (according to the present invention). In this step), since the wire W is temporarily moved forward and backward before and during the operation, the linking phenomenon of the wire W is promoted as described above (execution of the linking elimination process according to the present invention). ) The wafer thickness can be efficiently cut out, while the wafer thickness accuracy can be improved. That is, most of the work 28 is cut while the wire W (wire group) is driven in one direction (forward drive), so that the work 28 is cut while the wear of the wire W is suppressed and high sharpness is maintained. In addition, by temporarily driving the wire W back and forth, the linking phenomenon can be eliminated with almost no wear deterioration of the wire W. In particular, in this wire saw, since the wire W is driven to advance and retreat within a predetermined range including the cutting start position of the wire W with respect to the workpiece 28, it becomes possible to eliminate the linking phenomenon in advance before starting the cutting, Therefore, each wire W can be cut into the workpiece 28 individually and appropriately from the cutting start stage.

  Therefore, even when an extremely thin wafer such as a silicon wafer for solar cells is cut out so that the distance between the wires W is extremely close, the ultra thin wafer can be accurately obtained without any linking phenomenon. It becomes possible to cut out well and efficiently.

  Next, a second embodiment of the wire saw according to the present invention will be described.

  The basic configuration of the wire saw according to the second embodiment is basically the same as that shown in FIGS. 1 and 2, and only the cutting operation control by the main controller 41 is as shown in the flowchart of FIG. This is different from the operation control of the first embodiment.

  Specifically, in the second embodiment, as shown in FIG. 4, in place of the processing of steps S1, S4, S7, and S8 of the first embodiment, steps S1 ′ and S4 ′ described below, respectively. , S7 ′ and S8 ′, the driving speed of the wire W is switched without switching the driving direction of the wire W during the cutting operation of the work 28.

  That is, the main control unit 41 first drives the wire W in the forward drive state in step S1 ′. At this time, the main control unit 41 drives the wire W at a speed (hereinafter, simply referred to as a low speed) sufficiently slower than a set speed (referred to as a reference speed) when cutting the workpiece 28. For example, in this embodiment, the reference speed is set to 800 m / min, and the driving speed of the wire W in step S1 ′ is set to 400 m / min.

  Then, after the start of cutting of the wire W into the workpiece 28, when the workpiece 28 reaches a predetermined cutting feed position (YES in step S3), the driving speed of the wire W is accelerated from a low speed to a reference speed, and this speed is maintained. Then, the workpiece 28 is cut (step S4 ').

  Next, when the workpiece 28 reaches a specific cutting feed position (YES in step S6), the driving speed of the wire W is reduced and the wire W is driven at a low speed for a set time (step S7 '), and then the wire is again turned on. The drive speed of W is accelerated and returned to the reference speed (step S8 ').

  Thereafter, the workpiece 28 is cut while maintaining the driving speed of the wire W at the reference speed. When the workpiece 28 reaches a specific cutting feed position (YES in step S6), the wire W is decelerated for a set time to reduce the speed. Drive at speed. Thus, in this embodiment, the wire W is driven at a low speed for a set time every time the work 28 reaches the position where the cutting feed has advanced by, for example, 5 mm from the switching time of step S4 ′.

  According to the second embodiment as described above, the wire W is driven in a forward (one-way) driving state throughout the entire process, but the wire W is temporarily lowered to a low speed as described above, so that the wire is driven. The elimination of the W linking phenomenon is promoted (linking elimination process). That is, as described above, a change in the vibration state of the wire W occurs due to a change in the driving speed of the wire W, thereby promoting the elimination of the linking phenomenon. In particular, the wire W tends to vibrate (resonate) more easily when driven at a speed lower than the driving speed at the time of cutting the workpiece because of its natural frequency. Therefore, by temporarily reducing the driving speed from the reference speed to the low speed as described above, the vibration of the wire W is moderately amplified, and as a result, the slurry adhered to the wire W is dropped and stuck to each other. Separation of W will be promoted.

  Accordingly, in the second embodiment as well, as in the first embodiment, the linking phenomenon can be effectively eliminated, and as a result, an extremely thin wafer can be cut out accurately and efficiently. There is an advantage that can be. Further, in the second embodiment, the wire W (wire group) is driven only in one direction throughout the entire process, so that it is more advantageous than the first embodiment from the viewpoint of avoiding wear deterioration of the wire W. Become.

  The method for cutting the wire saw and workpiece 28 described above is an example of a preferred embodiment of the wire saw and workpiece cutting method according to the present invention, and the specific configuration of the wire saw and the specific workpiece cutting method are as follows. The present invention can be changed without departing from the gist of the present invention.

  For example, in the first embodiment, the wire W is driven forward / backward every time cutting feed advances by 5 mm, but the position (cutting feed position) for driving the wire W forward / backward in this way is limited to this. What is necessary is just to set suitably instead of a thing. Further, it is not always necessary to drive the wire W forward / backward for every fixed feed amount as in the embodiment, and the wire W may be driven forward / backward only once at a specific cutting feed position. This is the same for the second embodiment. However, there is an advantage that the ringing phenomenon can be more reliably eliminated by intermittently executing the advance / retreat driving of the wire W a plurality of times throughout the entire process as in the embodiment.

  In addition, as a driving state of the wire W for eliminating the linking (linking-removing step), the driving of the wire W is stopped in addition to the forward / backward driving or the low-speed driving of the wire W as in the above embodiment. May be. Also in this case, a change occurs in the vibration state of the wire W, thereby promoting the elimination of the linking phenomenon.

1 is an overall configuration diagram of a wire saw according to the present invention. It is a block diagram which shows the controller of a wire saw. It is a flowchart which shows an example of the control (1st Embodiment) by a controller. It is a flowchart which shows an example of control (2nd Embodiment) by a controller.

Explanation of symbols

W wire 10A, 10B Wire feeding / winding device 11A, 11B Bobbin drive motor 24A, 24B, 26A, 26B Guide roller 25 Drive motor 28 Work 30 Work feed device 34 Work feed motor 36A, 36B Slurry supply device

Claims (5)

A wire saw in which a wire group in which a plurality of wires are arranged between the guide rollers is formed by winding the cutting wire fed from the wire feeding device around the plurality of guide rollers and winding the wire around the guide rollers. A method of cutting a workpiece using
The wire is fed out from the wire feeding device, and the wire is wound up by the wire winding device to drive the wire in one direction at a constant speed. In addition to this step of cutting the workpiece by relatively cutting and feeding the workpiece in a direction perpendicular to the workpiece, this step is executed before or during this step, and the wires are attracted to each other in the wire group. In order to impart vibration to the wire to eliminate the linking phenomenon , the wire driving speed is temporarily reduced while maintaining the wire driving direction in the one-way driving state, or the wire driving is temporarily performed. work cutting method according to a wire saw, characterized in that it comprises a linking solve for step Ru is stopped. The work cutting method according to claim 1,
The wire running only the linking solve for step a predetermined time period from a position to start the cut of the workpiece relative to the workpiece cutting method according to a wire saw, characterized that you initiate this process thereafter. In the workpiece cutting method according to claim 1 or 2 ,
The process includes a step of detecting a cutting and feeding position of the workpiece with respect to the wire group, and the linking elimination process by interrupting the process when the detected feeding position reaches a specific feeding position. work cutting method according to a wire saw, it characterized that you run a. In the workpiece cutting method according to any one of claims 1 to 3,
Wherein in this step, the linking eliminate a step a plurality of times intermittently wire saw process according workpiece cutting, characterized in execution to Rukoto. A plurality of guide rollers; a wire feeding device that feeds a cutting wire to the guide roller; and a wire winding device that winds the wire from the guide roller, wherein the wire fed from the wire feeding device is A wire group in which a plurality of wires are arranged between the guide rollers is formed by being wound around the guide roller and being wound around the wire winding device, and the wire group is driven in the axial direction by each operation, In a wire saw that cuts the workpiece by cutting and feeding the workpiece to the wire group in this wire driving state,
Cutting feed means for cutting and feeding the workpiece relative to the wire group in a direction perpendicular to the axial direction;
A storage means for storing a specific feed position set in advance as a work feed position by the cutting feed means;
A feed position detecting means for detecting a feed position by the cutting feed means;
Drive control means for controlling the operation of the feeding device and the wire winding device to drive the wire group,
In response to detection of the workpiece feed position by the feed position detection means, the drive control means winds the wire while feeding the wire from the wire feeding device at a feed position other than the specific feed position. The wire is driven in a one-way driving state in which the wire is driven in one direction at a constant speed by winding the device, and the wire driving speed is maintained while maintaining the wire driving direction in the one-way driving state at the specific feeding position. A wire saw characterized by controlling the operations of the wire feeding device and the wire winding device to temporarily lower the wire or to stop the driving of the wire.

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