JP2013111674A - Machining method using fixed abrasive wire saw, and wafer - Google Patents

Abstract

Provided is a processing method using a fixed abrasive wire saw capable of appropriately controlling wire tension at a cutting position in cutting of a workpiece using a fixed abrasive wire saw, and a wafer manufactured by the processing method. To do.
A wire row 20 comprising a single fixed abrasive wire 10 wound around main rollers 18A and 18B at a constant pitch is reciprocated in the longitudinal direction, and the reciprocating wire row 20 is covered. In the fixed-abrasive wire saw 1 that presses the workpiece 50 and simultaneously cuts the workpiece 50 at a plurality of locations to process it into a plurality of wafers, the reversal timing in the traveling direction of the reciprocating traveling is set on the wire feeding side. The distance at which the wire portion at the preset reference position moves is equal to or longer than the length of the wire wound around the main rollers 18A and 18B.
[Selection] Figure 1

Description

  The present invention relates to a fixed abrasive wire saw in which a fixed abrasive wire having a plurality of abrasive grains fixed on its surface is reciprocated in the longitudinal direction, and a workpiece is cut with the fixed abrasive wire reciprocated.

  Conventionally, a fixed abrasive wire wound around a pair of rollers having a plurality of grooves and having abrasive grains fixed on its surface is reciprocated in the axial direction, and pressed against the fixed abrasive wire that reciprocally travels the workpiece to cut and feed. However, a technique for cutting a workpiece by a wire saw that cuts the workpiece into a wafer is disclosed (see Patent Document 1). In such a cutting technique, the tension at the cutting position of the fixed abrasive wire is controlled using a wire tension applying mechanism on both ends (see paragraph 0005).

  By the way, the workpiece is pressed against the fixed abrasive wire at a constant speed, and the fixed abrasive wire is bent in the pressing direction as time passes. The workpiece is cut by a reaction force (hereinafter referred to as back force) of the force by which the workpiece presses the fixed abrasive wire. However, in the transitional stage until the cutting of the workpiece is stabilized, the tension at the cutting position of the fixed abrasive wire is weak and easily bent. Therefore, in the transition stage, the force acting in the transverse direction intersecting the cutting direction is larger than the force acting in the cutting direction (that is, the back force). For this reason, in the transition stage, the direction of cutting in the workpiece tends to become unstable. In particular, when the workpiece is formed from a polycrystalline semiconductor material such as a polycrystalline silicon ingot, the polycrystalline silicon crystal grains vary in size and locally vary in hardness. Therefore, in the transition stage, the crystal grains of polycrystalline silicon become an obstacle, and the fixed abrasive wire at the cutting position is likely to be pushed in the lateral direction, and the wire is likely to swell. The waviness of the wire causes unintentional cutting (wafer dropping) during the processing of the wafer. The waviness of the wire can be reduced by controlling the tension of the fixed abrasive wire at the cutting position.

JP 2011-20197 A

  Conventionally, at both ends of the fixed abrasive wire, tension is applied to the wire portion that is not wound around the roller, or the tension applied to the wire at the cutting position is released by releasing the applied tension. I have control. Therefore, if conditions such as the total winding length of the wire around the roller are the same and the reversal cycle in the wire traveling direction is set to a short time, the shorter the reversal cycle, the shorter the wire portion (wire array at the cutting position). ) Has undergone a change in the wire traveling direction before being subjected to tension control, and tension control of the wire portion at the cutting position may not be sufficiently performed.

  Therefore, the present invention has been made paying attention to such an unsolved problem of the conventional technology, and in cutting a workpiece using a fixed abrasive wire saw, the wire tension at the cutting position is reduced. It is an object of the present invention to provide a processing method using a fixed abrasive wire saw that can be appropriately controlled and a wafer manufactured by the processing method.

  [Aspect 1] In order to achieve the above object, the processing method using the fixed abrasive wire saw according to aspect 1 includes a single fixed abrasive wire having a plurality of abrasive grains fixed on the surface thereof and arranged opposite to each other in parallel to the axis. A plurality of rollers wound around the plurality of rollers at a constant pitch, the wire row is reciprocated in the longitudinal direction, and the workpiece is pressed against the wire row that has been reciprocated. A processing method using a fixed abrasive wire saw for cutting a workpiece, wherein a predetermined predetermined tension is applied to the fixed abrasive wire at both ends of the fixed abrasive wire, and the fixed abrasive wire is reciprocated. When the fixed abrasive wire travels, the distance of the portion of the fixed abrasive wire at a preset reference position to move is equal to or longer than the length of the wire wound around the plurality of rollers. To control the inversion timing.

With such a configuration, the moving distance of the portion of the fixed abrasive wire that is fed to the wire row at the preset reference position is at least the length of the wire wound around the plurality of rollers. Then, the traveling direction of the fixed abrasive wire can be reversed.
As a result, since all of the wires wound around the plurality of rollers once come out of the rollers, the traveling direction is reversed. Tension control can be sufficiently received. Therefore, the back force of each wire portion of the wire row can be stabilized, and variations in cutting speed can be reduced.

[Aspect 2] Furthermore, in the fixed abrasive wire saw according to aspect 2, the traveling control unit is configured to set the wire traveling speed Vw at the time of cutting the workpiece to 100 [m / min with respect to the configuration of aspect 1. ] <Vw <400 [m / min].
With such a configuration, for example, when the workpiece is a semiconductor ingot, in particular, a polycrystalline semiconductor ingot, the wafer is cut as compared with a conventional case where the workpiece is cut at a wire traveling speed of 400 [m / min] or more. It is possible to reduce the number of omissions.

[Aspect 3] On the other hand, in order to achieve the above object, the wafer according to aspect 3 is manufactured by the processing method according to aspect 1 or 2.
The wafer of aspect 3 is a wafer processed by a wire array that has been sufficiently subjected to tension control by the processing method of aspect 1 or 2. Therefore, by using a processing method in which the moving distance of the portion of the fixed abrasive wire at the preset reference position is reversed with the moving distance less than the length of the wire wound around the plurality of rollers. Compared to the manufactured wafer, the wafer has a higher accuracy such as dimensions.

  According to the processing method using the fixed abrasive wire saw according to the present invention, the reversing timing of the traveling direction of the fixed abrasive wire is set to the reversing timing at which the tension of the wire row can be sufficiently controlled. The back force of each contributing wire part can be stabilized, and the effect that variation in cutting speed can be reduced is obtained.

(A) And (b) shows an example of the main structures of a fixed abrasive wire saw typically. (A) is sectional drawing at the time of cut | disconnecting the fixed abrasive wire 10 along a longitudinal direction, (b) is sectional drawing at the time of cut | disconnecting along the direction orthogonal to a longitudinal direction. FIG. 3 is a diagram schematically showing a state of cutting a workpiece 50 by a wire row 20. (A) is the figure which modeled the mechanism of the wire tension increase at the time of a cutting | disconnection, (b) is a figure explaining the force generate | occur | produced in a fixed abrasive wire at the time of a cutting | disconnection. It is a figure which shows an example of the reference point which determines the inversion period of a wire travel direction. (A) is a figure which shows an example of the inversion period of the wire fixing site | part which concerns on this invention, (b) is a figure which shows an example in case an inversion period is a short period. It is a figure which shows the relationship between the wire travel speed based on the cutting test which concerns on an Example, and the number of wafer drop-off number.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1-6 is a figure which shows embodiment of the processing method by the fixed abrasive wire saw which concerns on this invention.
(Constitution)
Hereinafter, the structure of the fixed abrasive wire saw according to the present invention and the processing method using the fixed abrasive wire saw will be described with reference to FIGS. FIGS. 1A and 1B schematically show an example of the main configuration of a fixed abrasive wire saw. FIG. 2A is a cross-sectional view when the fixed abrasive wire 10 is cut along the longitudinal direction, and FIG. 2B is a cross-sectional view when it is cut along a direction orthogonal to the longitudinal direction. FIG. 3 is a diagram schematically showing a state of cutting the workpiece 50 by the wire row 20. FIG. 4A is a diagram schematically showing a mechanism of increasing wire tension at the time of cutting, and FIG. 4B is a diagram for explaining the force generated on the fixed abrasive wire when the workpiece 50 is cut.

A fixed abrasive wire saw 1 shown in FIGS. 1A and 1B manufactures a wafer by thinly cutting (that is, slicing) a workpiece 50 such as a single crystal or polycrystalline silicon ingot or a compound semiconductor ingot. Device.
As shown in FIGS. 1A and 1B, the fixed abrasive wire saw 1 includes a fixed abrasive wire 10, wire bobbins 12A and 12B, main rollers 18A and 18B, tension rollers 16A and 16B, and a guide. Rollers 14A to 14D and motors 24A and 24B are provided.

The fixed abrasive wire 10 is a wire having abrasive grains fixed on its surface, and is composed of one wire having a length L (for example, several [km] to several tens [km]).
In the present embodiment, as shown in FIGS. 2A and 2B, the fixed abrasive wire 10 includes a wire strand 100 made of a material such as a high-tensile wire, diamond, CBN, SiC, GC, alumina, and the like. It is comprised from the abrasive grain 102 by a material, and the adhering material 104 (binder) which adheres the wire strand 100 and the abrasive grain 102. FIG. In addition, as for the fixing method of the abrasive grains, electrodeposition, resin fixing such as fixing (thermosetting, etc.) with an organic material or an inorganic material is used, but the present invention is not limited to these. The material of the strand may be a piano wire or a high tensile non-metallic fiber wire (including a fiber).

  Returning to FIG. 1, the main rollers 18 </ b> A and 18 </ b> B are juxtaposed in parallel with each other with a predetermined interval in the horizontal direction, and are supported rotatably. Further, each of the main rollers 18A and 18B is formed with a plurality of grooves (non-circular) along the roller rotation direction (circumferential direction) formed on the roller surface side by side in the axial direction at a constant pitch (for example, 325 [μm]). (Shown).

  The fixed abrasive wire 10 is wound along the grooves at positions opposed to the main rollers 18A and 18B in the plurality of grooves formed on the roller surface, and one end side in the axial direction of the main rollers 18A and 18B. It is wound while shifting the groove sequentially from the other end side. Thereby, the longitudinal direction of the wire part hung around the groove | channel in each opposing position is orthogonal to the axial direction (longitudinal direction) of main roller 18A, 18B. In addition, a plurality of wire portions orthogonal to the axial direction constitute a wire row 20 arranged at a constant pitch in the axial direction of the main rollers 18A and 18B.

  One end side of the fixed abrasive wire 10 extending from the winding start side is wound around the wire bobbin 12A via guide rollers 14A and 14C and a tension roller 16A. On the other hand, the other end extending from the winding end side of the fixed abrasive wire 10 is wound around the wire bobbin 12B via the guide rollers 14B and 14D and the tension roller 16B.

  The wire bobbin 12A is rotatably provided by a rotational driving force applied from the motor 24A. With this configuration, the wire bobbin 12A rotates in response to the application of either the forward rotation or the reverse rotation of the motor 24A, and the fixed abrasive wire 10 wound around the wire bobbin 12A becomes the main rollers 18A, 18b. It is drawn out to. Further, the wire bobbin 12A rotates in accordance with the application of the other rotational driving force of the forward rotation or the reverse rotation of the motor 24A, and the fixed abrasive wire 10 is wound around the wire bobbin 12A.

  The wire bobbin 12B is rotatably provided by a rotational driving force applied from the motor 24B. With this configuration, the wire bobbin 12B rotates according to the application of the rotational driving force of either forward rotation or reverse rotation of the motor 24B, and the fixed abrasive wire 10 wound around the wire bobbin 12B becomes the main rollers 18A, 18b. It is drawn out to. Furthermore, the wire bobbin 12B rotates in response to the application of either the forward rotation or the reverse rotation of the motor 24B, and the fixed abrasive wire 10 is wound around the wire bobbin 12B.

The main roller 18A is a driving roller, and rotates by a rotational driving force applied from a driving motor (not shown). On the other hand, the main roller 18B is a driven roller (may be a driving roller), and rotates in the same rotational direction as the main roller 18A by a rotational driving force applied via the main roller 18A and the fixed abrasive wire 10. .
The tension roller 16A applies tension to the fixed abrasive wire 10 by the pressing force applied from the actuator 26A. Further, the tension roller 16B applies tension to the fixed abrasive wire 10 by the pressing force applied from the actuator 26B.

As shown in FIGS. 1 (a) and (b), the fixed abrasive wire saw 1 is further provided with two coolant nozzles 22, a ball screw 30, a motor 33, which are disposed above the wire row 20. A work feed table 34 and a slice base 36 are provided.
The coolant nozzle 22 is a nozzle for injecting coolant supplied at a predetermined water pressure by an electric pump (not shown) to a contact portion between the wire row 20 and the workpiece 50 when the workpiece 50 is cut. is there.
Here, the coolant is, for example, cooling for cooling the heat generated in the contact portion, imparting lubricity for reducing cutting resistance, cleaning of the wafer after processing, rust prevention for metal parts, water It is a water-based liquid configured to have properties such as a reaction suppressing property between the workpiece and the workpiece.

  The ball screw 30 includes a screw shaft 31, a nut 32, a first rolling groove formed on the outer diameter surface of the screw shaft 31, and a screw shaft 31 formed on the inner diameter surface of the nut 32 (not shown). A second rolling groove facing one rolling groove, a rolling element rolling path formed between the first rolling groove and the second rolling groove, and a plurality of rolling elements loaded in the rolling element rolling path And rolling elements (balls). The lower end of the screw shaft 31 is fixed to the upper surface of the work feed table 34. Further, a motor 33 is connected to the screw shaft 31 so that the screw shaft 31 can rotate. The nut 32 has an outer diameter surface fixed to a bracket (not shown). When the screw shaft 31 is rotated by the rotational driving force applied from the motor 33, the screw shaft 31 reciprocates (vertically moves) in the vertical direction through the rolling of the rolling elements, and the work feed table 34 is not shown. It reciprocates (moves up and down) along the guide device.

In the present embodiment, the workpiece 50 is fixed to the slice base 36 by an adhesive member. The workpiece 50 is detachably attached to the lower part of the work feed table 34 via the slice base 36.
The fixed abrasive wire saw 1 further includes a control unit 70 that controls operations of various motors, actuators, electric pumps, and the like, as shown in FIG.

  The controller 70 controls the motors 24A and 24B and the drive motor of the drive roller 18A according to the set wire travel speed Vw. In this embodiment, detection information from a detector (not shown) that detects the current traveling speed of the fixed abrasive wire 10 and the state (rotational speed, etc.) of each motor, using the set wire traveling speed Vw as a target speed. Based on the above, each motor is feedback-controlled. Thereby, the wire travel speed at the time of cutting the workpiece 50 is controlled to maintain the set target speed Vw.

  Further, the control unit 70 controls the actuators 26A and 26B in accordance with a preset wire tension F. In this embodiment, detection information from a detector (not shown) that detects the current tension of the fixed abrasive wire 10 and the state of the actuator (pressing amount, rotating amount, etc.) using the set wire tension F as a target tension. Based on the above, each actuator is feedback-controlled. Thereby, the wire tension at the cutting position (wire row 20) at the time of cutting the workpiece 50 is controlled so as to become the set target tension F. The actuators 26A and 26B may be linear motion actuators such as solenoids or rotary actuators such as torque motors.

Here, the tension of the wire row 20 at the time of cutting the workpiece 50 changes according to the following equation (1) according to pressing the workpiece 50 against the wire row 20 at a constant speed.
Ftn = Ft1 + μFN1 + μFN2 +... ΜFN (n−1) + μFNn (1)
In the above equation (1), Ftn is the tension of the nth turn of the wire row 20. Ft1 is an initial tension before the workpiece 50 is pressed. μFN1, μFN2,..., μFN (n−1), μFNn respectively connect the wire row 20 to the constant speed of the work piece 50 of 1, 2,. The tension increases by pressing.

  Since the tension of the wire row 20 continues to descend at a constant speed while the workpiece 50 is pressed against the wire row 20, it continues to increase according to the above equation (1). Therefore, as shown in FIG. 4A, the tension Ft2 after one roll after pressing the workpiece 50 becomes a tension obtained by adding the increased μFN1 to the initial tension Ft1 (Ft2 = Ft1 + μFN1).

  Further, as shown in FIG. 4B, a back force 80 is generated as a reaction force of this force in response to the pressing of the workpiece 50. The back force 80 is in a weak state from when the workpiece 50 is pressed until the cutting is stabilized. Further, each wire constituting the wire row 20 is a force in a horizontal direction (a direction perpendicular to the longitudinal direction of the wire) that intersects the back force 80 when the workpiece 50 is cut according to the physical properties of the workpiece 50 or the like. 81 (hereinafter referred to as horizontal force 81). Accordingly, the force 82 in the direction of travel of the wire when the workpiece 50 is cut (hereinafter referred to as the travel force 82) is a combined force of the back force 80 and the horizontal force 81.

Here, the higher the tension of the wire row 20, the stronger the back force 80 becomes, and the ratio of the back force 80 to the traveling force 82 increases. Thereby, the fluctuation width (swell) of the wire at the time of cutting can be reduced, and coalescence with adjacent wires is less likely to occur. However, if the tension of the wire row 20 is too high, the wire breaks.
On the other hand, the lower the tension of the wire row 20, the weaker the back force 80 becomes, and the ratio of the horizontal force 81 to the advancing force 82 increases. Therefore, the fluctuation width (swell) of the wire at the time of cutting increases. As a result, coalescence with adjacent wires is likely to occur, and the number of wafer dropouts increases.

  In the present embodiment, in consideration of this fluctuation width, a wire tension of 27 [N] or more is set as the initial tension Ft1. Then, the tension applied to the wire row 20 via the tension rollers 16A and 16B is controlled by the control of the actuators 26A and 26B by the control unit 70, and the set value is 27 [N] or more when the workpiece 50 is cut. The tension of was maintained. The upper limit of the wire tension is determined by the strength of the wire and the device configuration.

Further, in the present embodiment, the control unit 70 controls the reversal timing of the traveling direction in the reciprocating traveling of the fixed abrasive wire 10 as follows.
Specifically, the controller 70 determines that the moving distance of the wire portion (hereinafter referred to as a wire fixing portion) at a preset reference position on the wire feeding side is the main roller 18A, 18B. The distance is controlled so as to be equal to or longer than the length of the wire wound around the wire. Here, an arbitrary position of the fixed abrasive wire 10 can be set as the reference position. Further, tension control by the tension rollers 16A and 16B is performed at the wire portions extending from the end portions of the wire rows 20 to the respective wire bobbins. Therefore, all the wires wound around the main rollers 18 </ b> A and 18 </ b> B need to come out from the end of the wire row 20 in the direction of each wire bobbin.

Accordingly, in order to ensure that the wire row 20 can be subjected to tension control, the distance of moving the reversal timing in the wire traveling direction in one direction of the wire fixing portion is the distance of the fixed abrasive wire 10 to the main rollers 18A and 18B. It is preferable to set the time when the total winding length is reached.
The control unit 70 reciprocates the fixed abrasive wire 10 while controlling the motor 33 to rotationally drive the screw shaft 31 of the ball screw 30 to move the work feed table 34 at a constant speed (for example, 0.8). [mm / min]). As a result, the workpiece 50 mounted on the work feed table 34 is pressed at a constant speed via the slice base 36 to the wire row 20 that reciprocates at a wire traveling speed 320 [m / min]. As shown in FIG. 3, the workpiece 50 pressed against the wire row 20 is cut at a plurality of locations at the same time by the wire row 20 arranged in parallel at a constant wire pitch (for example, 325 [μm]). In this way, a plurality of workpieces 50 are simultaneously cut at a constant pitch and processed into a plurality of wafers.

On the other hand, in this embodiment, the workpiece 50 is a polycrystalline semiconductor ingot formed from a polycrystalline semiconductor material or a polycrystalline semiconductor block formed from this ingot (hereinafter referred to as a polycrystalline semiconductor ingot without distinguishing both). The wire travel speed is controlled as follows.
Specifically, the controller 70 controls the wire traveling speed to a speed within a range of 100 [m / min] <Vw <400 [m / min] when the polycrystalline semiconductor ingot is cut.

  Here, when a polycrystalline semiconductor ingot such as a polycrystalline silicon ingot is cut, it is known that the hardness of the polycrystalline semiconductor ingot varies locally because the size of crystal grains changes locally. . In addition, it is also known that a polycrystalline semiconductor ingot generates wire blurring during cutting in the vicinity of inclusions such as silicon nitride mixed in the ingot during ingot growth.

As a result of experiments, the inventors have found that when a polycrystalline silicon ingot is cut at the same wire traveling speed as when a conventional single crystal silicon ingot is cut, the number of wafer drops increases as the wire traveling speed increases. I found that I tend to do. On the other hand, it has been found that the number of dropped wafers tends to decrease by reducing the wire traveling speed to lower than 400 [m / min]. However, when the wire traveling speed was 100 [m / min] or less, the cutting performance deteriorated, and the necessary cutting ability could not be obtained.
For this reason, in this embodiment, when cutting the polycrystalline semiconductor ingot, the wire traveling speed Vw is controlled to a speed within a range of 100 [m / min] <Vw <400 [m / min]. I made it.

(Operation)
Next, based on FIGS. 5-6, operation | movement of the fixed abrasive wire saw 1 using the processing method of this embodiment is demonstrated.
FIG. 5 is a diagram illustrating an example of a reference point for determining a reversal period in the wire traveling direction. Fig.6 (a) is a figure which shows an example of the inversion period of the wire fixing part which concerns on this invention, (b) is a figure which shows an example in case an inversion period is a short period.
Hereinafter, the operation will be described assuming that the workpiece 50 is a polycrystalline silicon ingot, the wire travel speed Vw is 320 [m / min], and the wire tension is 30 [N].

  The controller 70 controls the drive motor of the drive roller 18A, the motor 24A, and the motor 24B to synchronously drive the wire bobbins 12A and 12B and the drive roller 18A, thereby moving the fixed abrasive wire 10 to a preset wire travel speed. Reciprocate at 320 [m / min]. Here, most of the fixed abrasive wire 10 is wound around the wire bobbin 12A with the wire bobbin 12A as the wire supply side and the wire bobbin 12B as the winding side.

  The control unit 70 controls the motor 24A to rotate the wire bobbin 12A such that the fixed abrasive wire 10 is fed out 1500 [m] and wound up 1490 [m]. On the other hand, the motor 24B is controlled to cause the wire bobbin 12B to rotate such that the fixed abrasive wire 10 is wound up 1500 [m] and fed out 1490 [m] in synchronization with the rotation of the wire bobbin 12A. Further, the drive motor 18 is controlled to rotate the drive roller 18A in the same rotation direction in synchronization with the rotation operations of the wire bobbins 12A and 12B. As a result, the fixed abrasive wire 10 is reciprocated at a speed of 320 [m / min] and a new wire portion is supplied. That is, for each round trip, a new wire portion is added by 10 [m] to the wire row 20 contributing to cutting, and the wire portion used for cutting is wound by 10 [m] on the wire bobbin 12B. Go.

Further, the control unit 70 controls the tension rollers 16A and 16B by controlling the actuators 26A and 26B so that the initial tension of the fixed abrasive wire 10 becomes 30 [N].
On the other hand, the control unit 70 controls the inversion cycle in the wire traveling direction by controlling the drive motor of the drive roller 18A, the motor 24A, and the motor 24B.
Specifically, as shown in FIG. 5, the control unit 70 causes the wire part (wire fixing part) at the “reference point-on” position, which is the end part in the wire feed-out direction of the wire row 20, to be wound by wire. The reversal timing is the time when the vehicle travels more than the distance to the “reference point-out” position on the taking direction side.

  By doing so, as shown in FIG. 6A, the wire winding region from “reference point-enter” to “reference point-exit”, which is the shaded portion in the figure, that is, the workpiece 50 The traveling direction is reversed every time when the wire fixing part can travel the entire winding region (full length) or more with respect to the region including the whole. Here, in FIGS. 6A and 6B, the horizontal axis is time [min], and the vertical axis is the wire fixing portion when the position of “reference point-on” is 0.0 [km]. Traveling position [km]. Here, the wire bobbins 12A and 12B are rotated such that a new wire portion is added little by little, for example, the fixed abrasive wire 10 is fed out 1500 [m] and wound up 1490 [m]. For this reason, the traveling position of the wire fixing portion gradually protrudes (in this example, by 10 [m]) from the winding region to the “reference point-out” side.

  By setting such a reversal cycle, each wire fixing portion (updated for each newly added portion) travels from “reference point-in” to “reference point-out”. In “reference point-out”), the traveling direction of the wire fixing part is reversed. The inversion timing at this time is either the top of the waveform (lower collision) or the top of the waveform (upper collision) in FIG. By setting such a reversal timing, the wire row 20 can sufficiently receive tension control by the tension rollers 16A and 16B at both ends of the fixed abrasive wire 10.

  On the other hand, as shown in FIG. 6 (b), when the reversal timing of the wire travel direction is set to the time when the wire fixing part travels a distance of about 1/3 of the entire winding area, the travel distance is short. Therefore, the traveling direction of the wire fixing portion is reversed before the wire row 20 is subjected to the tension control by the tension rollers 16A and 16B. Therefore, at this inversion timing, the wire row 20 cannot receive sufficient tension control.

  The control unit 70 reciprocates the fixed abrasive wire 10 and controls the motor 33 to lower the work feed table 34 at a constant speed. As a result, the polycrystalline silicon ingot mounted on the work feed table 34 is pressed at a constant speed via the slice base 36 to the wire row 20 that reciprocates at a wire traveling speed 320 [m / min]. The polycrystalline silicon ingot pressed against the wire row 20 is cut at a plurality of locations simultaneously at a constant wire pitch, and the polycrystalline silicon ingot is processed into a plurality of wafers.

  As described above, according to the processing method using the fixed abrasive wire saw 1 according to the present embodiment, the moving distance of the wire portion at the preset reference position on the wire feeding side is the main roller 18A, It controls so that it may become more than the total winding length of the fixed abrasive wire 10 wound by 18B. That is, the reversal timing in the wire traveling direction is controlled so that the wire row 20 travels in a range where the tension control by the tension rollers 16A and 16B at both ends of the fixed abrasive wire 10 can be sufficiently received. As a result, the tension of the wire row 20 is controlled so as to maintain the set tension F for each inversion cycle, so that the back force 80 at the time of cutting the fixed abrasive wire 10 is stabilized and variation in cutting speed is reduced. be able to.

Further, the wire traveling speed Vw when cutting the polycrystalline semiconductor ingot as the workpiece 50 is controlled to a speed within the range of 100 [m / min] <Vw <400 [m / min]. Thereby, compared with the case where it cut | disconnects at the speed of 400 [m / min] or more of the past, the number of drop-off of a wafer can be reduced.
Further, the tension at the cutting position (wire row 20) of the fixed abrasive wire saw 1 when cutting the workpiece 50 is controlled to 27 [N] or more. Thereby, compared with the case where it controls to less than 27 [N], it becomes possible to make the ratio of the back force 80 in the advancing force 82 sufficiently large with respect to the horizontal force 81. Thereby, the runout width of the wire at the time of cutting can be reduced.
Here, the tension rollers 16A and 16B, the actuators 26A and 26B, and the control unit 70 constitute a tension control unit. The control unit 70 constitutes a travel control unit. In addition, “reference point-in” corresponds to the first reference position, and “reference point-out” corresponds to the second reference position.

(Modification)
In the above-described embodiment, the configuration in which the workpiece 50 is pressed down from the top of the wire row 20 in the vertical direction has been described as an example, but the configuration is not limited thereto. The direction of the wire row 20 may be changed to another direction, and the workpiece 50 may be moved and pressed from another direction according to the direction.
In the above-described embodiment, the work feed table 34 has been described by taking as an example a configuration in which the ball screw 30 is driven up and down by a motor, but the present invention is not limited to this configuration.

For example, another configuration such as a configuration in which the workpiece feed table 34 is linearly moved using a linear actuator to press the workpiece 50 against the wire row 20 may be employed.
Moreover, in the said embodiment, although two main rollers which comprise the wire row | line 20 were used, it is good not only as this structure but as a structure which uses three or more main rollers.

In the above-described embodiment, the configuration in which the motor 18A is driven as a driving roller out of the two main rollers 18A and 18B is described as an example, but the configuration is not limited thereto.
For example, all the main rollers may be rotatably provided, and other configurations such as a configuration in which only the motor that rotationally drives the wire bobbins 12A and 12B is rotated or a configuration in which all the main rollers are rotationally driven by the motor may be employed.

The above embodiments are preferable specific examples of the present invention, and various technically preferable limitations are given. However, the scope of the present invention is described in particular in the above description to limit the present invention. As long as there is no, it is not restricted to these forms. In the drawings used in the above description, for convenience of illustration, the vertical and horizontal scales of members or parts are schematic views different from actual ones.
Further, the present invention is not limited to the above-described embodiment, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.

Hereinafter, based on FIG. 7, the Example using the processing method similar to the processing method by the fixed abrasive wire saw 1 of the said embodiment is described.
FIG. 7 is a diagram illustrating a relationship between the wire traveling speed based on the cutting test according to the example and the wafer dropout rate.
In this example, a polycrystalline silicon ingot (W: 156 [mm] × H: 156 [mm] × L: 210 [mm]) for a solar cell was employed as the workpiece 50. As the fixed abrasive wire 10, a wire (wire diameter φ 130 [mm], average abrasive particle size 12 to 25 μm, wire length 30 [km]) manufactured by Asahi Diamond Industry was used. The wire travel direction is reciprocal travel, the wire travel speed is set in the range of 200 [m / min] to 1400 [m / min] in increments of 100 [m / min], and the wire tension at the cutting position is set. The cutting test was carried out at each set speed with setting to 32 [N]. In addition, as described in the above embodiment, the reversal timing of the wire travel direction is such that the travel distance of the wire fixing portion is the main rollers 18A and 18B in FIG. It was made for it to become more than the total winding length of the fixed abrasive wire 10 to. Moreover, the descending speed of the work feed table 34 at the time of cutting was set to 0.8 [mm / min]. Moreover, the coolant made from Yushiro Chemical Industry was used as a processing liquid. Moreover, it cut | disconnected 3 times each with respect to the same wire travel speed.

As a result of performing a cutting test under such measurement conditions, the test results shown in FIG. 7 were obtained as the relationship between the wire traveling speed and the wafer dropout rate (average value of three tests). In FIG. 7, “◯” indicates the average value at each measurement speed, and the “D” -shaped vertically extending bar line indicates the range of variation in the number of dropped wafers at each measurement speed.
Note that the drop-off number rate is obtained as follows. First, when cutting one or more silicon ingots, the number of slices per cut (one shot) is:
Number of slices = [(length in the direction perpendicular to the wire of the ingot) × (number of ingots per shot)] / [wire pitch]
The wafer drop rate is calculated as follows:
Wafer drop rate = [number of wafers dropped during slicing] / [number of slices]
Is required.

  As shown in FIG. 7, in the speed range of 600 [m / min] to 800 [m / min] generally used for cutting a single crystal silicon ingot, the drop-off number ratio is about 0.5 to 2. It is 0 [%], and it can be seen that there is a variation in the dropout rate at the same travel speed. On the other hand, in the speed band of less than 400 [m / min] according to the present invention, the wafer drop rate is stable at about 1.1 [%] or less, and 600 [m / min] to 800 [m / min]. It can be seen that the wafer drop rate is lower than that in the speed zone. In addition, it can be seen that the dropout rate is stable without fluctuations.

Further, when the wire traveling speed is increased from 800 [m / min], the wafer drop rate is about 1.1 to 3.7 [%] up to the speed band of 1200 [m / min]. In comparison with the speed band of less than 400 [m / min], the variation in the number of dropped wafers is large and the number of dropped sheets is high.
As described above, in the cutting process of the polycrystalline semiconductor ingot by the fixed abrasive wire saw 1, as has been found in the examples, the wire traveling speed Vw is set to 100 [m / min] <Vw <400 [m / min]. For example, the dropout rate of wafers can be reduced as compared with the conventional processing at a wire traveling speed of 400 [m / min] or more.

DESCRIPTION OF SYMBOLS 1 Fixed abrasive wire saw 10 Fixed abrasive wire 12A, 12B Wire bobbin 14A-14D Guide roller 16A, 16B Tension roller 18A, 18B Main roller 20 Wire row 22 Coolant nozzle 24A, 24B, 33 Motor 26A, 26B Actuator 30 Ball screw 34 Workpiece Feed table 36 Slice base 50 Work piece 70 Control unit 80 Back force 81 Horizontal force 82 Progressive force

Claims (3)

A wire array configured by winding a single fixed abrasive wire having a plurality of abrasive grains fixed on a surface around a plurality of rollers arranged opposite to each other in parallel to each other at a constant pitch; A processing method using a fixed abrasive wire saw that reciprocates in the longitudinal direction and presses the workpiece against the reciprocated wire row to cut the workpiece,
At both ends of the fixed abrasive wire, a predetermined tension set in advance to the fixed abrasive wire is applied,
When reciprocating the fixed abrasive wire,
Reversing the traveling direction of the fixed abrasive wire so that the moving distance of the portion at a preset reference position in the fixed abrasive wire is equal to or longer than the length of the wire wound around the plurality of rollers. The processing method by the fixed abrasive wire saw characterized by controlling timing.   The said traveling control part controls the wire traveling speed Vw at the time of cutting | disconnecting the said workpiece to the speed within the range of 100 [m / min] <Vw <400 [m / min]. A processing method using the fixed abrasive wire saw according to 1.   A wafer manufactured by the processing method according to claim 1.

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