JP5424251B2 - Thin wafer processing method - Google Patents

Description

The present invention relates to a method of cutting a workpiece as a large number of thin wafers in a multi-wire saw.

The multi-wire saw is used when a workpiece such as a silicon ingot or a silicon block is brought into contact with a large number of parallel wires in a running state, and the workpiece is cut into a large number of thin wafers. In the cutting process, a machining fluid such as a coolant or a slurry is supplied to a large number of wires.

The wire is wound in multiple between a plurality of main rollers, and is parallel in a cutting area facing the workpiece. Since the wire interval in the cutting area is regulated by the groove pitch of the main roller with multiple grooves, the thickness of the wafer after cutting is determined by the groove pitch of the main roller and the wire diameter.

In wafer cutting processes such as solar cells, thinning is progressing, and as the thinning progresses, the distance between wires is narrowed. During cutting, if the coolant or machining fluid partially adheres to the wire in the cutting area, the wire partially approaches due to the surface tension of the coolant or processing fluid. Is partially narrower or wider than the specified interval. Such a phenomenon close to the wire tends to appear in the wire cutting area, particularly in an intermediate position between the main rollers.

The above-mentioned wire deviation generally depends on the viscosity of the machining liquid such as a cooling liquid, but generally starts to appear at a wire pitch of 0.5 mm or less, and particularly easily occurs at 0.3 mm or less. When cutting is started in the workpiece while such a wire shift occurs, irregular cut grooves are formed in the workpiece in the initial stage of cutting, and the wire continues cutting following the irregular cut grooves. . Therefore, the thickness of the wafer varies, and the products after the cutting process become uneven.

On the other hand, in Patent Document 1, in a wire saw, a work material (workpiece) is brought into contact with a large number of wires in a running state, and the workpiece is cut into a large number of thin wafers to prevent the wires from shaking at the beginning of cutting. Therefore, temporarily fix the guide plate to the work material (work), cut the guide plate at the beginning of cutting to stabilize the pitch of many wires, and cut the work material (work) after stabilization. Is disclosed. Since this technique is not directly related to a machining liquid such as a cooling liquid, it cannot be a means for solving the problem due to the surface tension of the machining liquid.

JP 2007-301688 A

Accordingly, an object of the present invention is to prevent a wire shift caused by the surface tension of a coolant partially attached to a large number of wires in a multi-wire saw, particularly a multi-wire saw using a wire with fixed abrasive grains. That is.

Under the above-described problems, the thin wafer processing method of the present invention is configured to bring a workpiece into contact with a number of traveling wires while supplying a coolant to a number of wires with fixed abrasive grains parallel at a predetermined pitch. In a multi-wire saw that cuts a large number of thin wafers, at the start of cutting, the wire was driven at a low speed without supplying the coolant, and the wire was bitten into the workpiece, and a cut was formed at the workpiece cutting start position. Later, the supply of the cooling liquid is started and the wire speed is increased, and the workpiece is continuously cut at a steady speed (Claim 1).

Further, in the thin wafer processing method of the present invention, the wire is point-contacted to the cutting start position of the workpiece in a state where the square workpiece is inclined by 1 to 3 degrees with respect to the wire in the cutting area. .

In the thin wafer processing method of the present invention, a guide member is integrally fixed as a part of the workpiece to the cutting start end of the workpiece, the wire and the guide member are brought into point contact at the start of cutting, and a cooling liquid is supplied. Without running, run the wire at a low speed, bite the wire into the guide member, and after forming a cut at the cutting start position of the guide member, start supplying the coolant and increase the wire speed. The workpiece is continuously cut as the speed following the guide member (claim 3).

Furthermore, in the thin wafer processing method of the present invention, the hardness of the guide member may be equal to the hardness of the workpiece, but is preferably made of a material smaller than the hardness of the workpiece.

In the thin wafer processing method of the present invention, the cutting action area of a large number of wires is placed in a processing chamber filled with mist, and at least at the start of cutting, the wire is cooled or lubricated by the mist in the processing chamber. Item 5).

According to the thin wafer processing method of the present invention, the cooling liquid is not supplied at the start of cutting, so that the phenomenon near the wire does not occur, and the wire travels at a low speed in the initial stage. In addition, since the wire does not receive a force in the deflection direction on the workpiece, the workpieces bite into the workpiece while maintaining a predetermined pitch, thereby forming a stable equal pitch cut. Therefore, the wire pitch does not shift at the beginning of processing, and the processing accuracy of the thickness of the thin wafer is improved.

If the wire is in point contact with the cutting start position of the workpiece while the square workpiece is tilted by 1 to 3 degrees, the wire quickly bites into the workpiece at the start of cutting, and cools at the start of cutting. The influence of heat generation on the workpiece and the wire due to the absence of the liquid supply can be further reduced.

If the guide member is integrally fixed to the cut end of the workpiece as a part of the workpiece, and the wire is in point contact with the guide member, the wire quickly bites into the guide member at the start of cutting. The influence of heat generation on the workpiece and the wire due to the fact that the coolant is not supplied at the start of cutting can be almost eliminated (claim 3).

If the material of the guide member is smaller than the hardness of the workpiece, the wire bites into the guide member more quickly, the cutting efficiency is improved, and the wear of the wire can be reduced.

If the cutting action area of many wires is placed in a processing chamber filled with mist, the wire touches the mist in the processing chamber and cools at least at the start of cutting, and the cutting surface is also lubricated by the mist. Smooth machinability can be ensured (Claim 5).

In 1st Embodiment of the thin wafer processing method of this invention, it is a side view of the principal part of the multi-wire saw at the time of the process of a workpiece | work. In 2nd Embodiment of the thin wafer processing method of this invention, it is a side view of the principal part of the multi-wire saw at the time of the process of a workpiece | work. In the 3rd Embodiment of the thin wafer processing method of this invention, it is a side view of the principal part of the multi-wire saw before the start of the cutting of a workpiece | work. In the 3rd Embodiment of the thin wafer processing method of this invention, it is a side view of the principal part of the multi-wire saw at the time of continuing cutting of a workpiece | work. In 4th Embodiment of the thin wafer processing method of this invention, it is a side view of the principal part of the multi-wire saw at the time of the cutting start of a workpiece | work. FIG. 5 is a partial cross-sectional view of the relationship between the main roller groove and the wire. It is a front view of a processing locus of a work, A is a processing locus by the present invention, and B is a processing locus by a conventional technique. It is a side view of the guide member used as a part of workpiece | work.

FIG. 1 shows a first embodiment of the thin wafer processing method of the present invention. In FIG. 1, a multi-wire saw 1, for example, travels a wire 3 with multiple fixed abrasive grains wound around the outer periphery of three parallel grooved main rollers 2, and a cylinder in a cutting area of the wire 3. Then, the workpiece 4 is cut at the position of each wire 3 by pressing the workpiece 4 such as a silicon prism or other shape silicon ingot or silicon block. The workpiece 4 is held by the base plate 6 and moves in the machining feed direction during machining.

As shown in FIG. 6, the main roller 2 has a large number of V-shaped annular grooves 2 a on the outer peripheral surface, and the pitch P of the numerous grooves 2 a is a predetermined interval between the wires 3, that is, the workpiece 4. It is set so as to correspond to the thickness t of the wafer 5 after the cutting process.

The wire 3 is placed in parallel in the corresponding groove 2a of the two main rollers 2 in the cutting area facing the workpiece 4, that is, the upper area, and is orthogonal to the center line of the axis of the main roller 2. In a non-cutting region that does not face the workpiece 4, that is, in a lower left region or a lower right region, the winding is performed in a state of being displaced by one pitch from the groove 2a of one main roller 2 to the groove 2a of the other main roller 2. It is hung.

In the thin wafer processing method of the first embodiment, at the start of cutting, the surface of the cutting start position of the workpiece 4 is brought into line contact with the wire 3 and the wire 3 is lowered without supplying the coolant 7 from the nozzle 8. After traveling at a speed and causing the wire 3 to bite into the workpiece 4 and forming a cut at the cutting start position of the workpiece 4, the process shifts to steady machining, and one or more nozzles 8 provided above the wire 3. Then, the supply of the coolant 7 such as the coolant is started, the wire speed is increased, and the cutting of the workpiece 4 is continued at a steady speed. At the time of steady processing, the multi-wire saw 1 cuts the workpiece 4 thinly at a constant thickness t by bringing the workpiece 4 into contact with the cutting area of the wire 3 while supplying the coolant 7, as shown in FIG. Then, it is processed as a large number of thin wafers 5.

Since the cooling liquid 7 is not supplied at the start of cutting, there is no phenomenon near the wires due to the surface tension of the cooling liquid 7 between the wires 3, and each wire 3 bites into the work 4 at equal intervals. , To form a stable machining trajectory. For this reason, the thickness t of the wafer 5 after cutting becomes a predetermined dimension from the start of cutting of the workpiece 4 as shown in FIG. In this way, the processing accuracy of the thickness t of each wafer 5 is improved. This enables thinner processing.

On the other hand, when the coolant 7 is supplied at the start of cutting and the adjacent wires 3 are partially displaced by the surface tension between the adjacent wires 3, a large number of the wires 3 are caused to move toward the workpiece 4 while being displaced. In this case, the thickness t of the wafer 5 after cutting does not have a constant dimension as shown in FIG. Become.

As described above, since the cooling liquid 7 is not supplied at the start of cutting, the phenomenon near the wire does not occur, and since the wire 3 travels at a low speed in the initial stage, the heat generation to the wire 3 and the workpiece 4 is kept small. It is done. The wire 3 bites into the workpiece 4 while maintaining a predetermined pitch P without receiving a force in the deflection direction, and forms a stable notch with a constant pitch P. Therefore, there is no deviation in the pitch P of the wire 3 in the initial stage of processing, and the processing accuracy of the thickness t of the wafer 5 is improved.

FIG. 2 shows a second embodiment of the thin wafer processing method of the present invention. In FIG. 2, the rectangular workpiece 4 is a rectangular column, for example, a quadrangular prism, and is held by the base plate 6 in a state where the rectangular workpiece 4 is inclined by 1 to 3 degrees with respect to the cutting region of the wire 3. For this reason, the position of the workpiece 4 closest to the wire 3 (lower right corner in FIG. 2) is the cutting start position.

Also in the second embodiment, the thin wafer processing method of the present invention makes the point of contact of the cutting start position of the workpiece 4 (the lower right corner in FIG. 2) with the wire 3 at the start of cutting. As in the embodiment, the wire 3 is run at a low speed without supplying the coolant 7 from the nozzle 8, the wire 3 is bitten into the workpiece 4, and a cut is formed at the cutting start position of the workpiece 4. The supply of coolant 7 such as coolant is started from one or two or more nozzles 8 provided above the wire 3 and the wire speed is increased to cut the workpiece 4 as a steady speed. continue.

Even in the second embodiment, the same effects as those of the first embodiment can be obtained. In particular, the square workpiece is set to be inclined by 1 to 3 degrees, and the wire 3 is set at the cutting start position of the workpiece 4. Because of the point contact, the wire 3 quickly bites into the cutting start position of the workpiece 4 at the start of cutting, and the influence of heat generation on the workpiece 4 and the wire 3 due to the cooling liquid 7 not being supplied at the start of cutting. Can be smaller.

Next, FIGS. 3 and 4 show a third embodiment of the thin wafer processing method of the present invention. In the third embodiment, the workpiece 4 has a cutting start end facing the wire 3, that is, a guide member 4 a long in the direction perpendicular to the wire 3 below the workpiece 4 as a part of the workpiece 4. The guide member 4a is a portion that first comes into contact with the wire 3 in place of the workpiece 4 at the start of cutting, and may be the same quality silicon as the hardness of the workpiece 4, but preferably has a hardness smaller than the hardness of the workpiece 4. It is made of a material such as resin, carbon, and adhesive.

For example, the guide member 4a made of a material such as silicon or resin is fixed to the work 4 in advance with an appropriate adhesive, and is removed from each wafer 5 by separation processing after the end of cutting. The adhesive as the guide member 4a is formed on the workpiece 4 with a coating film having a predetermined thickness, and is peeled off from each wafer 5 by a separation process after the end of cutting.

The cross-sectional shape of the guide member 4a, that is, the cross-sectional shape in a plane orthogonal to the axis of the main roller 2, is trapezoidal as shown in FIGS. 3 and 4, or is easy to cut as illustrated in FIG. From the viewpoint of heat dissipation efficiency, a right triangle, a regular triangle, a concave or convex shape, two rectangular members, a kamaboko shape or a two-crest shape, or a combination of these shapes. However, if the biting state of the large number of wires 3 with respect to the guide member 4a is taken into consideration, it is preferable that the lower end has a shape that makes point contact with the large number of wires 3, a triangular shape, a double mountain shape, or the shape shown in FIGS. Thus, it is set as the cross-sectional shape which has an acute angle at a lower end. In addition, although the coating film of an adhesive agent becomes a flat film | membrane normally by application | coating, it can also be made into the shape close | similar to the semi-cylindrical shape or the triangle which makes a point contact by raising a coating film to medium height.

As shown in FIG. 3, in the thin wafer processing method of the present invention, at the start of cutting, the acute angle portion of the guide member 4 a is lightly brought into point contact with the wire 3, and the coolant 7 is not supplied from the nozzle 8. Is moved at a low speed to cause the wire 3 to bite into the acute angle portion of the guide member 4a, and thereafter, as shown in FIG. While supplying the coolant 7 such as coolant from the nozzle 8 is started, the wire speed is increased, and the cutting of the workpiece 4 is continued following the guide member 4a as the steady speed. At the time of this steady processing, the multi-wire saw 1 makes the work 4 thinly cut at a constant thickness t by bringing the work 4 into contact with the cutting region of the wire 3 while supplying the cooling liquid 7, thereby forming a large number of thin wafers 5. Process.

Since the cooling liquid 7 is not supplied at the start of cutting, the phenomenon of near the wire due to surface tension does not occur between the wires 3, and each wire 3 bites into the guide member 4a at equal intervals and is stable. Form a machining trajectory. For this reason, the thickness t of the wafer 5 after cutting becomes a predetermined dimension from the start of cutting of the workpiece 4 as shown in FIG. In this way, the processing accuracy of the thickness t of each wafer 5 is improved. This enables thinner processing.

On the other hand, when the coolant 7 is supplied at the start of cutting and the adjacent wires 3 are partially offset by the surface tension, the many wires 3 are guided while the wires are shifted. In order to continue cutting of the workpiece 4 while maintaining the wire spacing in the state near the wire after that, the thickness t of the wafer 5 after the cutting is constant as shown in FIG. It will not be a dimension.

As described above, in the present invention, since the coolant 7 is not supplied at the start of cutting, the phenomenon near the wire does not occur, and the wire 3 travels at a low speed in the initial stage. Fever is kept small. Further, each wire 3 bites into the guide member 4a without receiving a force in the swing direction, and cuts the workpiece 4 while maintaining a predetermined pitch P, thereby forming a stable equal pitch P cut. Therefore, there is no deviation in the pitch P of the wire 3 in the initial stage of processing, and the processing accuracy of the thickness t of the wafer 5 is improved.

In particular, when the guide member 4a is in point contact with the wire 3, the wire 3 quickly bites into the guide member 4a at the start of cutting, and the workpiece is not supplied with the coolant 7 at the start of cutting. The influence of heat generation on the wire 4 and the wire 3 can be almost eliminated.

As described above, the hardness of the guide member 4a may be equal to the hardness of the workpiece 4, but is preferably made of a material smaller than the hardness of the workpiece 4. If the material of the guide member 4a is smaller than the hardness of the workpiece 4, the wire 3 can further bite into the guide member 4a more quickly, the cutting efficiency can be improved, and the wear of the wire 3 can be reduced.

Further, FIG. 5 shows a fourth embodiment of the thin wafer processing method of the present invention. In this fourth embodiment, the thin wafer processing method of the present invention is placed in a processing chamber 9 in which the cutting action areas of a large number of wires 3 are filled with a mist 10 of water vapor or other solution, and at least at the start of cutting, The wire 3 is cooled and lubricated by the mist 10 in the processing chamber 9.

If the cutting action areas of many wires 3 are placed in the processing chamber 9 filled with the mist 10, the wire 3 is cooled by the mist 10 at least at the start of cutting, and the cut surface is also lubricated by the mist 10. Smooth cutting performance can be secured, which is advantageous. The processing chamber 9 filled with the mist 10 is configured so as to be seen through by a transparent plate, and can be used continuously in the process of steady processing of the workpiece 4 as necessary.

This fourth embodiment can also be applied to the second and third embodiments. Note that a lubricating liquid, a cutting agent, and other special functional liquids can be mixed in the cooling liquid 7 and the mist 10 as necessary.

The multi-wire saw wire misalignment prevention method of the present invention is not limited to a silicon ingot or silicon block, but can be used when thinly cutting other workpieces 4.

1 Multi-wire saw 2 Main roller 2a Groove 3 Wire 4 Work 4a Guide member 5 Wafer 6 Base plate 7 Coolant 8 Nozzle 9 Processing chamber 10 Mist t Thickness P Pitch

Claims (5)

At the start of cutting in a multi-wire saw that cuts a workpiece into a number of thin wafers by contacting the workpiece with a number of wires traveling while supplying a coolant to a number of wires with fixed abrasive grains parallel at a predetermined pitch , Run the wire at a low speed without supplying the cooling liquid, bite the wire to the cutting start position of the workpiece, form the cut at the cutting start position of the workpiece, start supplying the cooling liquid and wire speed The thin wafer processing method is characterized in that the workpiece is continuously cut at a steady speed. 2. The thin wafer processing method according to claim 1, wherein the wire is brought into point contact with the cutting start position of the workpiece in a state where the rectangular workpiece is tilted by 1 to 3 degrees with respect to the wire in the cutting area. A guide member is fixed to the workpiece cutting start end as a part of the workpiece, and at the start of cutting, the wire and the guide member are brought into point contact, and the wire runs at a low speed without supplying coolant. Then, after the wire is bitten into the guide member and the cut is formed at the cutting start position of the guide member, the supply of the coolant is started and the wire speed is increased. The thin wafer processing method according to claim 1, wherein cutting is continued. 4. The thin wafer processing method according to claim 3, wherein the hardness of the guide member is made of a material smaller than the hardness of the workpiece. The cutting action area of a large number of wires is placed in a processing chamber filled with mist, and at least at the start of cutting, the wire is cooled or lubricated by the mist in the processing chamber. The thin wafer processing method of crab.

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