JP5056645B2 - Work cutting method and wire saw - Google Patents

Description

  The present invention relates to a work cutting method for cutting a large number of wafers from a work (for example, a silicon ingot, a compound semiconductor ingot, etc.), and a wire saw.

  Conventionally, a wire saw is known as means for cutting a wafer from a silicon ingot, a compound semiconductor ingot, or the like. In this wire saw, a plurality of cutting wires are wound around a plurality of rollers to form a wire row, the cutting wires are driven at a high speed in the axial direction, and slurry is appropriately supplied while the wire is being supplied. By cutting and feeding the workpieces to the row, the workpieces are simultaneously cut at each wire position (see Patent Document 1).

  More specifically, the entire workpiece in a state in which the contact plate is bonded to substantially the entire area in the axial direction of the workpiece on a part of the side surface of the workpiece, and the workpiece plate that holds the contact plate is held by the workpiece holding portion of the workpiece feeding mechanism. Is cut and fed and cut by a cutting wire from the opposite side of the backing plate. At this time, a method of pressing the workpiece against the wire row is known by a method of pressing the workpiece against the wire row from above and a method of pressing from below. However, in cutting the semiconductor silicon ingot, the workpiece is wired. The method of pressing the row from above is the mainstream.

Here, FIG. 4 shows an outline of an example of a conventional general wire saw.
As shown in FIG. 4, the wire saw 101 is mainly cut by a wire 102 for cutting the workpiece W, a grooved roller 103 around which the wire 102 is wound, a mechanism 104 for applying tension to the wire 102, and the like. A mechanism 105 for sending the workpiece W to be moved downward, and a mechanism 106 for supplying slurry at the time of cutting.

  The wire 102 is fed out from one wire reel 107 and passes through a traverser 108 and a tension applying mechanism 104 including a powder clutch (constant torque motor 109), a dancer roller (dead weight) (not shown), and the like, and a grooved roller 103. In. The wire 102 is wound around the grooved roller 103 about 300 to 400 times, and then wound around the wire reel 107 ′ through the other tension applying mechanism 104 ′.

  Further, the grooved roller 103 is a roller in which polyurethane resin is press-fitted around a steel cylinder and grooves are cut at a constant pitch on the surface thereof, and a wound wire 102 is predetermined by a driving motor 110. It can be driven in the reciprocating direction at a certain cycle.

  When the workpiece W is cut, the workpiece W is held down by the workpiece feeding mechanism 105 as shown in FIG. 5 and sent out to the wire 102 wound around the grooved roller 103. The workpiece feeding mechanism 105 includes a workpiece holding unit 111 for holding a workpiece, an LM guide 112 for feeding the workpiece downward, and a workpiece feeding main body 113, and the workpiece feeding along the LM guide 112 under computer control. By driving the main body 113, the work W held by the work holding part 111 can be sent out at a feed speed programmed in advance.

  The work W is bonded to the contact plate 114, and the contact plate 114 is held by the work plate 115. Then, the workpiece W is held by the workpiece holding unit 111 through the contact plate 114 and the workpiece plate 115.

  In the example of the work feeding mechanism 105 in FIG. 5, the lateral width of the contact plate 114 is formed to be narrower than the lateral width of the work plate 115, but the side edge portion of the work plate 115 does not protrude outward from the side surface of the contact plate 114. By increasing the lateral width of the contact plate 114 as described above, the problem that the wafer breaks due to the slurry that collides with the lower surface of the side edge of the work plate 115 and bounces against the wafer being cut is solved. An intended wire saw is also known (see Patent Document 2).

  However, when the lateral width of the contact plate 114 is increased as described above, there is a problem that an adhesion region between the workpiece W and the contact plate 114 increases, and it becomes difficult to separate the wafer and the contact plate 114 after cutting the workpiece.

  As shown in FIG. 4, a nozzle 117 is provided in the vicinity of the grooved roller 103 and the wound wire 102 so that slurry can be supplied from the slurry tank 118 to the wire 102 during cutting. . A slurry chiller 116 is connected to the slurry tank 118 so that the temperature of the slurry to be supplied can be adjusted.

Using such a wire saw 101, an appropriate tension is applied to the wire 102 using the wire tension applying mechanism 104, and the workpiece is cut and fed by the workpiece feeding mechanism 105 while the wire 102 travels in the reciprocating direction by the driving motor 110. To slice.
However, when the workpiece is cut into a wafer using the conventional general wire saw as described above, and the shape of the cut wafer is examined, a large warp has occurred. Warp is one of the important qualities in the cutting of semiconductor wafers, and further reduction is desired as product quality requirements increase.

JP-A-9-262826 JP-A-11-235653

Therefore, the inventor conducted detailed investigations on the shape of the cut wafer, and found that Warp was significantly deteriorated particularly in the latter half of the cut.
In order to investigate the cause of the Warp deterioration, the state of the workpiece during cutting was observed. The slurry is supplied to the workpiece cutting unit by driving the wire in the axial direction at a high speed to the workpiece side position while applying the slurry from above the wire row. At this time, it was found that most of the slurry that was attached to the wire and carried to the vicinity of the cutting part of the workpiece collided with the side surface of the workpiece at the wire entry portion to the workpiece and scattered to the outside of the workpiece. .

  Here, for example, when the work has a cylindrical shape such as a semiconductor silicon ingot, the slurry is scattered above the work when the work is cut from the center of the work. In particular, in the latter half of the cutting, it was found that the distance between the cutting part and the work holding part was reduced, and the slurry scattered from the work rebounded at the lower end surface of the work holding part and dropped to the work and the wire vigorously.

  In other words, Warp is significantly worse in the second half of cutting because the slurry that collides with the side surface of the workpiece and bounces off at the lower end surface of the workpiece holding part and drops to the workpiece and the wire vigorously. It became clear that the cause was that the wafer-like part and the wire were shaken.

  The present invention has been made in view of the problems as described above, and it is possible to suppress the slurry splashed from the work in the latter half of the cutting from bouncing back at the lower end surface of the work holding part and dropping into the work and the wire vigorously. An object of the present invention is to provide a workpiece cutting method and a wire saw that can improve the warp of a wafer to be cut.

In order to achieve the above object, according to the present invention, a wire wound around a plurality of grooved rollers is reciprocated in the axial direction, a contact plate is bonded to the workpiece to be cut, and the workpiece is held by the workpiece. The workpiece is held by the workpiece holding unit via the plate, and the workpiece held by the workpiece holding unit is relatively pushed down while the slurry is supplied from the nozzle to the wire, and is pushed against the reciprocating wire. A method for cutting a workpiece by cutting and feeding the workpiece and cutting the workpiece into a wafer, wherein the workpiece is cut with a distance between a lower end surface of the workpiece holding portion and an upper end of the workpiece of 40 mm or more. that provides a method of cutting a workpiece to be with.

  In this way, when the workpiece is cut with the distance between the lower end surface of the workpiece holding portion and the upper end of the workpiece being 40 mm or more, the slurry scattered from the workpiece in the latter half of the cutting rebounds at the lower end surface of the workpiece holding portion. Thus, it is possible to prevent the workpiece and the wire from falling down vigorously. As a result, the warp of the wafer to be cut can be improved.

In this case, the width of the backing plate, it is not preferable that less than half of the diameter of the workpiece.
In this way, if the lateral width of the backing plate is ½ or less of the diameter of the workpiece, the bonding area between the workpiece and the backing plate can be reduced, and the wafer and the backing plate can be separated after cutting the workpiece. It can be easily performed without damaging the wafer.

Further, according to the present invention, at least a wire wound around a plurality of grooved rollers and reciprocating in the axial direction, a nozzle for supplying slurry to the wire, and a contact plate bonded to a workpiece to be cut And a work feeding mechanism that pushes the work relative to the wire while holding the work through the work plate holding the corresponding plate, and supplying slurry to the wire from the nozzle, The workpiece held by the workpiece feeding mechanism is a wire saw that presses and feeds the workpiece against the reciprocating wire, and cuts the workpiece into a wafer shape, the workpiece feeding mechanism having a workpiece holding portion, The workpiece holding unit holds the workpiece via the contact plate and the workpiece plate, and a lower end surface of the workpiece holding unit and the workpiece The distance between the upper end of that provides a wire saw, characterized in that those at 40mm or more.

  Thus, the workpiece feeding mechanism has a workpiece holding portion, and holds the workpiece via the contact plate and the workpiece plate by the workpiece holding portion, and the lower end surface of the workpiece holding portion and the If the distance to the upper end of the workpiece is 40 mm or more, it is possible to suppress the slurry scattered from the workpiece from bouncing back at the lower end surface of the workpiece holding portion and dropping to the workpiece and the wire vigorously. As a result, the warp of the wafer to be cut can be improved.

In this case, the width of the backing plate, it is not preferable the at 1/2 or less of the workpiece diameter.
Thus, if the lateral width of the backing plate is ½ or less of the diameter of the workpiece, the bonding area between the workpiece and the backing plate can be reduced, and the wafer and the backing plate can be separated after cutting the workpiece. It can be easily performed without damaging the wafer.

  In the present invention, in the wire saw, the work is cut by setting the distance between the lower end surface of the work holding portion and the upper end of the work to 40 mm or more, so that the slurry scattered from the work rebounds at the lower end surface of the work holding portion, It is possible to suppress the forceful fall. As a result, the warp of the wafer to be cut can be improved.

Hereinafter, although an embodiment is described about the present invention, the present invention is not limited to this.
When a workpiece is cut into a wafer shape using a conventional general wire saw and the shape of the cut wafer is examined, a large warp has occurred. Warp is one of the important qualities in the cutting of semiconductor wafers, and further reduction is desired as product quality requirements increase.

  Therefore, the present inventor conducted detailed investigations on the shape of the cut wafer in order to solve such a problem, and found that Warp was remarkably deteriorated particularly in the latter half of the workpiece. Further investigation and examination revealed that Warp was significantly worse in the second half of the workpiece cutting because the slurry that collided with the side of the workpiece and bounced off the lower end surface of the workpiece holding part, leading to the workpiece and the wire. It was clarified that the cause was that the workpiece was cut and the wafer-like part and the wire were shaken by the violent drop.

  And when the distance between the lower end surface of the work holding part and the upper end of the work is increased and the work is cut, it is conceived that Warp deterioration in the latter half of the cutting can be suppressed, and the lower end face of the work holding part Experiments were conducted on the best distance between the workpiece and the top of the workpiece, and the present invention was completed.

FIG. 1 is a schematic view showing an example of the wire saw of the present invention.
As shown in FIG. 1, a wire saw 1 of the present invention mainly includes a wire 2 for cutting a workpiece W, a grooved roller 3 around which the wire 2 is wound, and a wire tension application for applying tension to the wire 2. A mechanism 4, a workpiece feeding mechanism 5 that feeds the workpiece W to be cut relatively downward, a slurry supply mechanism 6 that supplies slurry at the time of cutting, and the like.

  The wire 2 is fed out from one wire reel 7, and is passed through a traverser 8 through a wire tension applying mechanism 4 including a powder clutch (constant torque motor 9), a dancer roller (dead weight) (not shown) and the like, and a grooved roller. It is in 3. A wire row is formed by winding the wire 2 around the grooved roller 3 about 300 to 400 times. The wire 2 is wound around a wire reel 7 'through another wire tension applying mechanism 4'.

  FIG. 2 shows an example of a workpiece feeding mechanism that can be used in the wire saw of the present invention. As shown in FIG. 2, the workpiece W is bonded to the contact plate 14, and the contact plate 14 is held by the work plate 15. Then, the work W is held by the work holding unit 11 through the contact plate 14 and the work plate 15.

The lateral width of the work plate 15 is substantially the same as the lateral width of the backing plate 14.
Thus, if the horizontal width of the work plate 15 is substantially the same as the horizontal width of the contact plate 14, the slurry scattered from the work W is retained at the lower end surface of the work plate 15 while maintaining the holding force of the contact plate 14 of the work plate 15. Can be prevented from bouncing down and falling onto the workpiece W and the wire 2.

  The workpiece feeding mechanism 5 includes a workpiece holding portion 11 for holding down the workpiece W while being pushed down, an LM guide 12 and a workpiece feeding main body portion 13, and drives the workpiece holding portion 11 along the LM guide 12 by computer control. By doing so, it is possible to feed the workpiece W held at a feeding speed programmed in advance.

  And the workpiece | work W hold | maintained by the workpiece | work holding | maintenance part 11 of the workpiece | work feed mechanism 5 in this way is sent to the wire 2 located below by the workpiece | work feed mechanism 5 when cut | disconnecting. Further, the workpiece feeding mechanism 5 pushes the workpiece W down to the wire 2 until the wire 2 reaches the contact plate 14, thereby pushing and feeding the workpiece W against the wire 2. Then, after the cutting of the workpiece W is completed, the cut workpiece W is pulled out from the wire row by reversing the feeding direction of the workpiece W.

  Here, in the example of the workpiece feeding mechanism 5 as shown in FIG. 2, the workpiece W is pushed down and cut and fed. However, in the present invention, if workpiece feeding is performed by relatively pushing it down. good. That is, instead of sending the workpiece W downward, the workpiece W may be sent out by pushing the wire row upward.

The grooved roller 3 is a roller in which polyurethane resin is press-fitted around a steel cylinder and grooves are cut on the surface at a constant pitch. The wound wire 2 is reciprocated by a driving motor 10 in a reciprocating direction. It can be driven. When the workpiece is cut, an appropriate tension can be applied to the wire 2 by the wire tension applying mechanism 4.
Further, a nozzle 17 is arranged above the wire 2 wound around the grooved roller 3 and reciprocally traveling in the axial direction at the time of cutting, and when cutting the workpiece W, slurry can be supplied to the wire 2. It can be done.

  Here, the slurry supply means 6, that is, the means for supplying the slurry to the grooved roller 3 (wire 2) will be described. In this slurry supply means 6, a slurry tank 18 is connected to a nozzle 17 via a slurry chiller 16. The supply temperature of the supplied slurry is controlled by the slurry chiller 16, and the grooved roller 3 (wire 2) is supplied from the nozzle 17. Can be supplied. However, such a configuration is not limited to this, and the supply temperature of the slurry may be adjusted by configuring another heat exchanger, for example.

  Here, the type of slurry to be used is not particularly limited, and the same type of conventional slurry can be used. For example, GC (silicon carbide) abrasive grains can be dispersed in a liquid.

And in the wire saw 1 of this invention, as shown in FIG. 2, it has adjusted so that the distance H of the lower end surface of the workpiece holding part 11 and the upper end of the workpiece | work W may be 40 mm or more.
Here, the adjustment of the distance H between the lower end surface of the work holding unit 11 and the upper end of the work W can be performed by adjusting the thickness of the work plate 15, for example.

  Thus, in the wire saw 1, if the distance H between the lower end surface of the work holding part 11 and the upper end of the work W is 40 mm or more, the slurry scattered from the work W particularly in the latter half of the cutting is below the work holding part 11. It is possible to suppress the bouncing off to the workpiece W and the wire 2 vigorously at the end face. As a result, the warp of the wafer to be cut can be improved.

At this time, the lateral width of the contact plate 14 is preferably less than or equal to ½ of the diameter of the workpiece W.
As a conventional method for suppressing the influence of the slurry scattered on the side surface of the workpiece W, a method in which the lateral width of the contact plate 14 is ½ or more of the workpiece diameter is known. As in the conventional method, if the lateral width of the contact plate 14 is ½ or more of the workpiece diameter, the slurry bounced off from the workpiece plate 15 or the workpiece holding unit 11 is prevented from falling onto the workpiece W. However, the adhesion area between the workpiece W and the contact plate 14 becomes large, and it becomes difficult to separate the wafer and the contact plate 14 after cutting the workpiece, which may damage the wafer.

  However, according to the present invention, the lateral width of the contact plate 14 is ½ or less of the diameter of the workpiece W, preferably the smallest lateral width that can safely hold the workpiece W when the workpiece W is cut. The work W and the backing plate 14 are made smaller in the bonding area so that the wafer and the backing plate 14 can be easily separated from each other without damaging the wafer. By making the distance between the end face and the upper end of the workpiece 40 mm or more, it is possible to prevent the slurry bounced off from the workpiece plate 15 or the workpiece holding unit 11 from dropping onto the workpiece W with a strong force.

Next, the workpiece cutting method according to the present invention will be described. Here, a cutting method using the wire saw 1 and the workpiece feeding mechanism 5 as shown in FIGS. 1 and 2 will be described.
First, as shown in FIG. 2, the contact plate 14 is bonded to the work W, and the plate 14 is held by the work plate 15. Then, the workpiece W is held by the workpiece holding unit 11 via the contact plate 14 and the workpiece plate 15.

At this time, the distance H between the lower end surface of the work holding part 11 and the upper end of the work W is adjusted to be 40 mm or more.
Such adjustment of the distance H between the lower end surface of the work holding unit 11 and the upper end of the work W can be performed by adjusting the thickness of the work plate 15, for example. Alternatively, the thickness of the contact plate 14 may be adjusted.

  Then, with the tension applied to the wire 2 and reciprocating in the axial direction, the slurry holding mechanism 6 moves the workpiece holding unit 11 along the LM guide 12 of the workpiece feeding mechanism 5 while the slurry is supplied to the wire 2 by the slurry supply mechanism 6. Driven, the workpiece W is lowered, and the workpiece W is cut and fed into the wire row to cut the workpiece W.

  In this way, if the workpiece W is cut such that the distance between the lower end surface of the workpiece holding portion 11 and the upper end of the workpiece W is 40 mm or more, the slurry scattered from the workpiece W in the latter half of the cutting is It is possible to suppress the bouncing down to the work W and the wire 2 with the lower end surface. As a result, the warp of the wafer to be cut can be improved.

  Here, the wire saw work feeding mechanism as shown in FIG. 2 is used to cut and feed the work so as to feed the work downward. However, the work cutting method according to the present invention is not limited to this, and the work The feeding may be performed by relatively pushing down. That is, the work W may be sent out by pushing the wire row upward rather than sending the work W downward.

  Here, the magnitude | size of the tension | tensile_strength provided to the wire 2, the traveling speed of the wire 2, etc. can be set suitably. For example, the traveling speed of the wire can be set to 400 to 800 m / min. Moreover, the cutting feed speed at the time of carrying out cutting feed with respect to a wire row | line can be 0.2-0.4 mm / min, for example. These conditions are not limited to this.

  Here, although not particularly limited, the wire reversal cycle when the wire 2 is reciprocated during cutting of the workpiece can be set to 60 s, for example. Further, as the slurry supplied to the wire 2 at the time of cutting, for example, a mixture of GC # 1000 and coolant can be used, and the weight ratio can be set to a ratio of, for example, 50:50. Moreover, the temperature of slurry can be 15 degreeC-30 degreeC, for example.

By cutting the workpiece W in this way, when the wire row reaches the contact plate 14 on the upper surface of the workpiece W, that is, when the cutting of the workpiece W is completed, the feeding direction of the workpiece W is reversed. Then, the cut workpiece W is pulled out from the wire row.
At this time, it is preferable that the lateral width of the contact plate 14 is not more than ½ of the diameter of the workpiece W.
In this way, if the lateral width of the contact plate 14 is set to ½ or less of the diameter of the workpiece W, the bonding area between the workpiece W and the contact plate 14 can be reduced, and the wafer and the contact plate after the workpiece W is cut. 14 can be easily peeled off without damaging the wafer.

  As described above, in the present invention, in the wire saw, the work is cut with the distance between the lower end surface of the work holding part and the upper end of the work being 40 mm or more, so that the slurry scattered from the work rebounds at the lower end face of the work holding part. Thus, it is possible to prevent the workpiece and the wire from falling down vigorously. As a result, the warp of the wafer to be cut can be improved.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples of the present invention, but the present invention is not limited to these.

(Example)
A silicon ingot having a diameter of 300 mm and an axial length of 300 mm was cut into a wafer by the cutting method of the present invention using the wire saw of the present invention as shown in FIG. 1 under the cutting conditions shown in Table 1. Using the workpiece feed mechanism as shown in FIG. 2, the distance H between the lower end surface of the workpiece holding part and the upper end of the workpiece is changed between 40 and 100 mm by changing the thickness of the workpiece plate. The warp of the wafer after cutting was compared. The width of the work plate was 100 mm, and the width of the backing plate was 90 mm. The result is shown in FIG.

It was confirmed that if the distance H is 40 mm or more, a sufficient Warp improvement effect can be obtained.
Thus, the workpiece cutting method and the wire saw of the present invention can suppress the slurry splashed from the workpiece from rebounding at the lower end surface of the workpiece holding portion and falling down to the workpiece and the wire vigorously. It was confirmed that the Warp of the wafer to be cut can be improved.

(Comparative example)
Using a conventional wire saw as shown in FIG. 4, the silicon ingot is cut into a wafer under the same conditions as in the example except that the distance H between the lower end surface of the work holding portion and the upper end of the work is 10 mm, 20 mm, and 30 mm. Then, the Warp of the wafer after cutting was compared.
The result is shown in FIG.

As shown in FIG. 3, the Warp improves as the distance H between the lower end surface of the work holding portion and the upper end of the work increases, and the effect is particularly remarkable when the distance H is between 30 mm and 50 mm. I understand.
In addition, when the distance H is 50 mm or more, the amount of improvement of Warp is small. This is because the slurry scattered from the side surface of the workpiece falls to the workpiece and the wire almost without reaching the lower end surface of the workpiece holding portion. Because it became.

  On the other hand, as shown in FIG. 3, in the comparative example, it can be seen that the Warp is worse than the result of the example.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

It is the schematic which shows an example of the wire saw which concerns on this invention. It is the schematic which showed an example of the workpiece feeding mechanism in the wire saw which concerns on this invention. It is a figure which shows the result of an Example and a comparative example. It is the schematic which shows an example of the conventional wire saw. It is the schematic which showed an example of the workpiece feeding mechanism in the conventional wire saw.

Explanation of symbols

1 ... wire saw, 2 ... wire, 3 ... grooved roller,
4, 4 '... wire tension applying mechanism, 5 ... work feeding mechanism, 6 ... slurry supply mechanism,
7, 7 '... wire reel, 8 ... traverser, 9 ... constant torque motor,
DESCRIPTION OF SYMBOLS 10 ... Drive motor, 11 ... Work holding part, 12 ... LM guide,
13 ... work feed main body, 14 ... pad, 15 ... work plate,
16 ... Slurry chiller, 17 ... Nozzle, 18 ... Slurry tank.

Claims (2)

A wire wound around a plurality of grooved rollers is reciprocated in the axial direction, a backing plate is bonded to the workpiece to be cut, and the workpiece is held by a workpiece holding unit via a workpiece plate holding the corresponding plate. Then, while supplying slurry to the wire from the nozzle, the workpiece held by the workpiece holding unit is relatively pushed down, pressed against the reciprocating wire, and cut and fed to cut the workpiece into a wafer shape. A method of cutting a workpiece,
The workpiece is cut by setting the lateral width of the contact plate to ½ or less of the diameter of the workpiece, and setting the distance between the lower end surface of the workpiece holding portion and the upper end of the workpiece to 80 mm or more. Cutting method. At least a wire that is wound around a plurality of grooved rollers and reciprocates in the axial direction, a nozzle that supplies slurry to the wire, a contact plate that is bonded to the workpiece to be cut, and a workpiece that holds the corresponding plate A workpiece feeding mechanism is provided that feeds the wire to the wire by relatively pushing down the workpiece while holding the workpiece through a plate, and is held by the workpiece feeding mechanism while supplying slurry to the wire from the nozzle. A wire saw that presses and feeds the workpiece against the reciprocating wire, and cuts the workpiece into a wafer shape,
The work feeding mechanism has a work holding part, and the work holding part holds the work via the contact plate and the work plate,
The wire saw according to claim 1, wherein a width of the contact plate is ½ or less of a diameter of the workpiece, and a distance between a lower end surface of the workpiece holding portion and an upper end of the workpiece is 80 mm or more.

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