JP2722975B2 - Cutting method with multi-wire saw - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-wire saw (hereinafter, abbreviated as "wire saw" for convenience of explanation) for cutting a material such as a semiconductor material, ceramics or the like requiring high-precision cutting into a large number of thin wafers using wires and abrasive grains. C) cutting method.

[0002]

2. Description of the Related Art A wire saw presses an object to be cut (hereinafter, referred to as a "work") against a wire row having a predetermined pitch, and pours a working liquid containing abrasive grains (hereinafter, referred to as a "polishing liquid") into a wire and a workpiece. This is a device that makes relative movement and cuts into a large number of wafers by a grinding action.

FIG. 2 illustrates a cut portion of a general wire saw, (A) is a perspective view of a cut portion showing a state where a work is being cut, and (B) is a wire wound around a groove roller of the wire saw. It is a longitudinal side view which expands and shows a part of groove roller of a state. That is, as shown in (A), one wire 4 is inserted into a large number of ring-shaped grooves 13 engraved at a predetermined pitch p on the outer peripheral surfaces of the three groove rollers 1, 2, and 3 rotatably held. Is wound to form a wire row 5 having a predetermined pitch, and the wire row 5 is reciprocated or moved in one direction. The work lifting table 10 is gradually raised while the abrasive liquid 7 is applied to the work 6 from the abrasive liquid supply nozzle 12. And cut it. In the figure, 8 is a dummy plate, 9 is a base, and 11 is a base fixing bolt.

As a method of supplying the abrasive liquid, in the case of a method in which the wire array 5 is reciprocated and cut, the abrasive fluid 7 is applied to the wire arrays 5 on both sides of the work 6 as shown in FIG. In the case of a method or a method of cutting by moving the wire row 5 in one direction, there is a method of applying the abrasive 7 only to the wire row 5 on the entry side of the work 6 as shown in FIG.

In the grinding and cutting with such a wire saw, the grinding ability (the amount that can be ground in a unit time) determined by the material of the work 6, the surface pressure from the wire acting on the cut portion, the abrasive grains and the traveling speed of the wire row 5 Is basically set to a work lifting speed v that is appropriate to the above. If the work lifting speed v is increased, the surface pressure from the wire increases, so that the grinding ability tends to increase slightly. However, if the v is too large, an excessive load acts on the wire, which not only deteriorates the cutting accuracy but also breaks the wire. The danger increases. Therefore, a method of cutting the work 6 while keeping the load for pressing the work 6 against the wire row 5 constant has been widely adopted.

However, in the case of this method, the load to be set must be determined empirically, so there is waste in trial and error, and it is necessary to set the number of wires and the cross-sectional dimensions of the work. Further, depending on the load detection method, it is necessary to correct the weight of the work 6, and the load setting may be complicated.

[0007]

In a conventional wire saw, the cutting load is set to a small value to improve the cutting accuracy. However, this method reduces the work lifting speed, so that the cutting force is reduced. Efficiency must be reduced.

The inventors of the present invention have repeatedly studied the causes of the deterioration of the cutting accuracy, and found that one of the major causes is the heat generation of the wire due to the grinding. We found that it had an effect.

Hereinafter, the relationship between the heat generation of the wire array and the deterioration of the cutting accuracy will be described with reference to a one-way traveling type wire saw shown in FIG. Since the wire row 5 slides on the work 6 via the abrasive grains, frictional heat or grinding heat is generated, and the temperature of the wire row 5 on the exit side of the work 6 is higher than the temperature of the wire row 5 on the entry side of the work. Become. Since the wire row 5 on the exit side of the work 6 whose temperature has risen is wound around the groove roller 2, the surface temperature of the groove roller 2 is increased.

On the other hand, a general structure of the groove roller is as follows.
As shown in FIG. 4, a wear-resistant resin sleeve 14 having a wire guide groove 13 cut therein is press-fitted into a metal shaft 16 having a flange 16-1 at one end, and screwed to the metal shaft 16. The structure is integrated with the fastening nut 15.

In the case of the groove roller having such a structure, when the length of the work 6 is shorter than the length of the resin sleeve 14, the heat generation of the wire row is limited at most to the range of the length of the work 6. For example, the heat of the wire is transmitted only to the range of the span a in FIG. Therefore, the thermal expansion of the resin sleeve 14 in the axial direction occurs in the area of the span a, and conversely contracts in the axial direction in the area of the remaining span b.

Even when the work 6 is about the same length as the resin sleeve 14, heat is removed from both ends of the resin sleeve 14 by the flange 16-1 and the tightening nut 15, so that the vicinity of both ends of the resin sleeve 14 The temperature remains lower than that in the center, and axial contraction occurs at both ends.

In the case of a one-way traveling type wire saw shown in FIG. 3B, the heat input from the wire row 5 is large at the groove roller 2, and the wire is cooled while passing through the groove roller 1. Therefore, heat input to the groove roller 3 is small. However, if the area of the span a of the groove roller 2 expands in the axial direction, the position of the wire guide groove 13 of the groove roller 2 moves in the axial direction, and the position of the wire stretched between the groove rollers 2 and 3 is changed. As a result, the flatness of the wafer is impaired. In this case, the amount of movement of the wire guide groove 13 is large near both ends of the area of the span a, and the cutting accuracy of the wafer cut by the wire located in this area is significantly deteriorated.

In the reciprocating traveling type wire saw shown in FIG. 3 (A), the accuracy degradation due to the heat generation of the wire is the same. In this case, the heat input from the wire to the groove rollers 2 and 3 on both sides of the work 6 is performed alternately.
The temperature rise of the resin sleeve 14 is smaller than that of the groove roller 2 of the one-way traveling type wire saw shown in FIG. However, the groove rollers 2 and 3 alternately repeat the heat input from the wire when positioned on the exit side of the work 6 and the cooling of the wire when positioned on the entrance side of the work 6, resulting in an unstable wire trajectory. However, the cutting accuracy is still deteriorated.

On the other hand, a substrate material in the field of electronics represented by a silicon wafer is required to have a cutting technology with higher precision and higher efficiency.
However, the conventional wire saw cannot sufficiently meet such a demand unless the problem of a decrease in cutting accuracy caused by heat generation of the wire row is solved.

The present invention has been made in view of such circumstances, and has solved the problem of a decrease in cutting accuracy caused by heat generation of a wire row.
An object of the present invention is to propose a cutting method using a wire saw capable of high-precision and high-efficiency cutting.

[0017]

The inventors of the present invention cannot completely prevent heat generation of the wire row inevitably occurring in the wire saw, but the grooves on both sides of the work from the start to the end of the cut of the work. Based on the judgment that cutting accuracy can be secured by keeping the surface temperature of the roller constant, we examined the results and found that in the case of a one-way traveling type wire saw, a groove roller on which the wire row exiting the work is wound for the first time. It has been found that cutting accuracy can be improved by keeping the surface temperature of the resin sleeve constant from the start to the end of cutting, and the inventors have invented a cutting method using a wire saw capable of high-precision and high-efficiency cutting.

That is, the present invention is directed to a one-way traveling type multi-wire saw, in which the abrasive liquid supplied on the wire row on the work exit side is sprayed by the rotation of the groove roller around which the wire row is wound first . It is a method of cutting while controlling the temperature to be constant, and as a means for controlling the temperature of the droplets to be constant, the temperature of the abrasive liquid supplied onto the wire row on the work exit side, or The gist is a cutting method using a multi-wire saw, which is characterized by controlling a temperature and a flow rate, and further controlling a speed at which a work is pressed onto the wire row.

[0019]

In the present invention, the cutting is performed while controlling the temperature of the droplets generated by the rotation of the groove roller of the abrasive fluid supplied onto the wire row on the work exit side to be constant, for the following reason. . That is, the abrasive fluid supplied on the wire row on the work exit side travels on the wire row, and the wire row adheres to the surface of the groove roller around which the wire is wound first, and at the same time, droplets are generated by the rotation of the groove roller. Occur. Since the temperature Ts of the droplets substantially coincides with the surface temperature of the groove roller that generates the droplets, by keeping the temperature Ts of the droplets constant from the start to the end of cutting, the fluctuation of the temperature of the groove rollers on the work exit side is reduced. This is because it becomes possible to prevent the wire roller from moving in the axial direction due to expansion and contraction of the groove roller during cutting due to heat generation of the wire row.

According to the present invention, the temperature of the abrasive fluid supplied onto the wire row on the work exit side is set high at the rising stage in the wire running state before the start of cutting, and the temperature of the abrasive fluid is set immediately before the start of cutting. And the change in the temperature Ts of the droplets can be minimized by offsetting the heat generation of the wire row due to the grinding. Of course, the flow rate may be increased together with the temperature drop of the polishing liquid. If the increase in the temperature Ts of the droplet due to the heat generation of the wire array cannot be suppressed even by using the temperature of the abrasive fluid or the flow rate increase together, the work lifting speed v is reduced by the minimum necessary to reduce the temperature of the droplet. Ts can be kept constant.

The temperature of the abrasive liquid splash generated by the rotation of the groove roller around which the wire row exits the work first can be measured, for example, by installing a resistance thermometer close to the groove roller.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic diagram showing an example of a device configuration of a wire saw cutting unit for implementing the method of the present invention and a control system thereof.
7-1 is a workpiece entry side curtain-shaped abrasive liquid, 7-2 is a workpiece exit side curtain-shaped abrasive liquid, 12-1 is a workpiece entrance side abrasive liquid supply slit nozzle, 12-2 is a workpiece exit side abrasive liquid supply slit nozzle, 17 is a resistance thermometer, 18 is abrasive liquid splash, 20 is abrasive liquid supply system, 21 is splash temperature control device, 22 is abrasive liquid temperature control device, 23 is abrasive liquid flow rate control device, and 24 is work lifting speed control device. is there.

The work entry-side abrasive liquid supply slit nozzle 12-1 and the work exit-side abrasive liquid supply slit nozzle 12-2 arranged on both sides of the work 6 have elongated slit holes for supplying a curtain-like abrasive liquid. In addition, it has a length that covers the entire width of the wire row 5. The work entry-side abrasive liquid supply slit nozzle 12-1 may be arranged directly above the work 6. The abrasive liquid is supplied from the abrasive liquid supply system 20 to the abrasive liquid supply slit nozzles 12-1 and 12-2 on the work entrance side and the work exit side.

A resistance thermometer 17 for measuring the temperature of the abrasive liquid droplets 18 is arranged close to the groove roller 2 around which the wire row 5 that has exited the work 6 first winds.

Workpiece entry side abrasive liquid supply slit nozzle 12-
The polishing liquid 7-1 supplied from 1 is used for cutting the work 6. The abrasive fluid 7-2 supplied from the workpiece outlet-side abrasive fluid supply slit nozzle 12-2 travels on the wire row 5,
A part thereof adheres to the surface of the groove roller 2 and at the same time becomes a droplet 18 due to the rotation of the groove roller. The temperature Ts of the droplet 18 is measured by the resistance thermometer 17, and a temperature variation is detected by the droplet temperature control device 21.
Is controlled to be kept constant from the rising stage before the start of cutting to the end of cutting.

That is, according to the present invention, the grinding fluid temperature control device 22
The temperature of the abrasive fluid 7-2 supplied from the workpiece outlet-side abrasive fluid supply slit nozzle 12-2 is set high, and the cutting is started by lowering the temperature of the abrasive fluid 7-2 immediately before the start of cutting. Although the wire row 5 generates heat by the start of cutting, the temperature of the abrasive fluid 7-2 is lowered in advance, so that it is offset by the heat generated by grinding, and the fluctuation of the splash temperature Ts can be minimized. At this time, the flow rate of the polishing liquid 7-2 may be increased by the polishing liquid flow rate control device 23 as needed, and used together with the temperature control. In this manner, cutting is performed while maintaining the spray temperature Ts constant. As a result, the heat generation of the wire row 5 becomes constant, so that thermal fluctuation of the groove roller 2 is prevented.

When the cross-sectional shape of the work 6 is circular, for example, as shown in FIG. 1, the length L of the wire in the cross section of the work changes, thereby changing the heat value of the wire row 5. In the process of changing the calorific value, the temperature of the abrasive fluid, the flow rate, and the work-up speed are controlled in a stepwise manner to keep the splash temperature Ts constant.

That is, in the first step, the temperature of the polishing liquid 7-2 is reduced by the polishing liquid temperature control device 22 or the flow rate of the polishing liquid 7-2 is increased by the polishing liquid flow control device 23. If the control of the temperature or the flow rate cannot suppress the rise of the splash temperature Ts due to heat generation, the work lifting speed control unit 24 reduces the work lifting speed v by a necessary minimum as a second step. Work lifting speed v
Is set to the minimum necessary in order not to lower the cutting efficiency.

Next, in the process of decreasing the calorific value, the splash temperature Ts is kept constant in the reverse steps. That is,
In the first step, the workpiece lifting speed v is increased to improve the cutting efficiency, and in the second step, the temperature of the abrasive fluid 7-2 is increased or the flow rate is decreased.

EXAMPLE 1 A one-way traveling type wire saw shown in FIG. 1 was used to grind a quartz ingot (rectangular cross section) having a cross-sectional dimension of 125 mm × 125 mm and a length of 200 mm with GC # 600 abrasive grains and lapping oil. Was supplied onto the wire rows from the entry side and the exit side of the work, and cut under the conditions of 96 wire rows, a wire pitch of 2.0 mm, and a wire diameter of 0.20 mm, and the accuracy of the wafer was measured.

In this embodiment, the wire traveling speed is 400 m / m
In, work lifting speed 0.4mm / min, work inlet side supply abrasive liquid temperature is constant at 25 ° C, work outlet side supply abrasive liquid temperature is 31 ° C during rising, and the temperature is reduced from just before cutting start to 25 ° C constant. And As a result, the temperature of the abrasive droplets is
The temperature was almost constant at 28 ° C. during the rising and cutting. The flat defect near the cutting start portion of the wafer was greatly reduced, and the warpage of all the wafers was 10 μm or less.

For comparison, a wire running speed of 400 m / min and a work lifting speed of 0.4 mm / m were obtained by a conventional method.
In, the cutting was performed with the temperature of the polishing liquid on the entrance side and the exit side of the work kept constant at 25 ° C. As a result, the abrasive liquid splash temperature reached 28 ° C. in 15 minutes after the start of cutting, and became constant thereafter. In the vicinity of the cutting start portion of the wafer, a convex warpage was generated. Particularly, a warp of 40 μm at the maximum was observed in the edge wafer, and the warpage of 25 wafers exceeded 20 μm.

Example 2 A one-way traveling type wire saw shown in FIG.
A silicon ingot (circular cross section) having a length of 00 mm and a length of 150 mm was prepared using the same polishing liquid as in Example 1 and the number of wire rows was 12
0, wire pitch 1.15mm, wire diameter 0.18mm
Was cut under the following conditions, and the accuracy of the wafer was measured.

In this embodiment, the wire traveling speed is 400 m /
min, the temperature of the abrasive fluid on the entrance and exit sides of the workpiece is kept constant at 25 ° C., and the lifting speed of the workpiece is changed in the range of 0.1 to 0.9 mm / min so that the temperature Ts of the abrasive fluid is kept constant. Was. As a result, the temperature of the abrasive liquid changed in the range of 27 to 28 ° C., and the warpage of all wafers was 15 μm or less.

For comparison, a wire running speed of 400 m / min and a work lifting speed of 0.4 mm / m were obtained by the conventional method.
In, the cutting was performed with the temperature of the polishing liquid on the entrance side and the exit side of the work kept constant at 25 ° C. As a result, the abrasive liquid splash temperature gradually increased with the increase of the wire length L in the cross section of the work after the start of cutting, reached 33 ° C., and gradually decreased with the decrease of L.
The wafer was warped in a convex shape in the same manner as described above. In particular, the wafer at the end had a maximum warpage of 40 μm, and the warpage of 26 wafers exceeded 20 μm.

[0036]

As described above, according to the method of the present invention, it is possible to suppress the thermal deformation of the groove roller due to the heat generation of the wire in the one-way traveling type wire saw, thereby enabling high-precision cutting. Since cutting can be performed with almost no reduction in the work lifting speed, a high quality wafer can be cut with high efficiency. Further, the method of the invention comprises:
It is effective for a work having any cross-sectional shape, and has a great effect in high-precision cutting of a wafer represented by a substrate material in the field of electronics.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of a device configuration of a wire saw cutting unit for carrying out the method of the present invention and a control system thereof.

FIGS. 2A and 2B illustrate a cut portion of a general wire saw to which the present invention is applied. FIG. 2A is a perspective view of the cut portion showing a state where a workpiece is being cut, and FIG. It is a longitudinal side view which expands and shows a part of groove roller in the state where the wire was wound.

3A and 3B illustrate a method of supplying an abrasive liquid in a wire saw, in which (A) is a method of supplying an abrasive liquid in a method of cutting by reciprocating a wire array, and (B) is a method of operating the wire array in one direction. This is a method of supplying the abrasive liquid in the cutting method.

FIG. 4 is a schematic longitudinal sectional view showing the structure of a general groove roller of a wire saw.

[Explanation of symbols]

 1, 2, 3 Groove roller 4 Wire 5 Wire row 6 Work 7-1 Work entry-side curtain-shaped abrasive 7-2 Work exit-side curtain-shaped abrasive 10 Work lifter 12-1 Work entry-side abrasive liquid supply slit nozzle 12 -2 Work-side exit-side abrasive fluid supply slit nozzle 17 Resistance thermometer 18 Abrasive fluid splash 20 Abrasive fluid supply system 21 Splash temperature control device 22 Abrasive fluid temperature control device 23 Abrasive fluid flow control device 24 Work lifting speed control device

Claims (3)

(57) [Claims] 1. A multi-strand wire string stretched between groove rollers having wire guide grooves of a predetermined pitch is caused to travel in one direction, and is placed on a workpiece or on a wire row on an entrance side and an exit side of a workpiece. In a multi-wire saw that cuts an object to be cut into a large number of wafers by pressing the object to be cut onto the wire row while supplying a processing liquid containing abrasive grains, the processing liquid supplied to the wire row on the side of the object to be cut , A cutting method using a multi-wire saw, wherein cutting is performed while controlling the temperature of droplets generated by the rotation of a groove roller around which the wire row is wound first so as to be constant. 2. The groove roller on which the wire array is wound first.
So that the temperature of the droplets generated by the rotation of
2. The cutting method using a multi-wire saw according to claim 1, wherein the temperature, or the temperature and the flow rate, of the working fluid supplied onto the wire row on the cut object exit side are controlled. 3. A groove roller on which said wire array is wound first.
So that the temperature of the droplets generated by the rotation of
2. The method according to claim 1 , further comprising controlling a speed of pressing an object to be cut onto the wire row.