TWI858010B - Workpiece cutting method and workpiece cutting device - Google Patents

Abstract

The present invention is a method for cutting a workpiece, wherein the method is a method for cutting a workpiece using a wire saw, wherein a wire guide has a plurality of grooves formed at a predetermined interval along a rotation direction on an outer surface thereof. The cross-sectional shape of the groove of the unused wire guide at least comprises: an upper portion of the groove, located on the outer surface side of the wire guide and having a first opening angle (θ ₁ ) with the groove wall opposite thereto; a lower portion of the groove, located below the upper portion of the groove and having a second opening angle (θ ₂ ) with the groove wall opposite thereto; and a bottom portion of the groove, located at the lower end of the groove; the first opening angle (θ ₁ ) and the second opening angle (θ ₂ ) are in a relationship of θ ₁ >θ ₂ . An unused wire and an unused wire guide member are used in the following relationship: the maximum value (W _0,max ) of the groove width at the lower portion of the groove of the unused wire guide member is greater than the wire diameter (φ ₀ ) of the unused wire, and the minimum value (W _0,min ) of the groove width at the lower portion of the groove of the unused wire guide member is less than the wire diameter (φ ₀ ) of the unused wire. The unused wire is set in a state where it contacts the groove wall at the lower portion of the groove of the unused wire guide member and does not contact the bottom of the groove, and the workpiece is cut when the wire does not contact the bottom of the groove. Thereby, a workpiece cutting method can be provided which can suppress a decrease in productivity and obtain a good and stable Warp value from the early stage of use of the wire guide.

Description

Workpiece cutting method and workpiece cutting device

The present invention relates to a workpiece cutting method and a workpiece cutting device.

In recent years, the enlargement (larger diameter) of wafers has been expected. With this enlargement, wire saws are used exclusively for cutting ingots (for example, Patent Document 1). Wire saws are cutting devices that cut multiple wafers at the same time by moving a wire (high-tension steel wire) at high speed and pouring abrasive on the wire while pressing against a workpiece (for example, ingots of brittle materials such as silicon, glass, and ceramics. Hereinafter, they are also referred to as ingots) to cut.

Here, FIG9 shows an overview of a general example of a wire saw. As shown in FIG9, the wire saw 100 mainly includes a wire 101 for cutting an ingot (workpiece) 104, a wire array 111 formed by winding the wire 101 around a plurality of wire guides 102, a tension imparting mechanism (not shown) for imparting tension to the wire 101, and an ingot feeding device (not shown) for delivering the cut ingot (workpiece) 104.

The wire 101 is wound from one of the wire reels 103, passes through a tension imparting mechanism, and enters the wire guide 102. After the wire 101 is wound around the wire guide 102 about 300 to 400 times, it passes through another tension imparting mechanism and is wound on the wire reel 103'.

The wire guide 102 is a roller that presses a resin such as polyurethane around a steel cylinder and cuts grooves at a certain interval on its surface. The wound wire 101 can be driven in a reciprocating direction at a predetermined cycle by a driving motor. FIG10 shows the setting state of the wire 101 in the groove of the wire guide 102.

One of the important qualities of semiconductor wafer cutting is to evaluate the parameters related to the shape of the workpiece, namely Warp (or Warp value in some cases). The definition of Warp is shown in Figure 11. Warp is a shape parameter related to the deviation of the wafer from the center line plane, which is the maximum distance between the imaginary center plane of the wafer that is not adsorbed and fixed and the reference plane. Bow in the figure is an evaluation similar to Warp, which is a shape parameter of the distance between the center of the wafer and the reference plane. In addition, the measurement method is specified in JEIDA-43-1999, ASTM, and F1530-94.

As product quality requirements increase, further reduction of the warp value is expected. The cause of warp deterioration is known to be the combined effects of the thermal expansion of the grooved roller and the workpiece, the straightness of the workpiece feed, and the bending of the line during cutting. The means to solve this problem adopts the method described in Patent Document 2.

Patent document 2 discloses a method that measures the displacement of the axially changing ingot when cutting the ingot, and controls the axial displacement of the grooved roller accordingly (such as the temperature and flow rate adjustment of the cooling water flowing to the grooved roller), thereby controlling the relative position of the workpiece relative to the entire length of the axially changing ingot while cutting.

[Prior Art Literature] [Patent Literature]

[Patent document 1] Japanese Patent Publication No. 09-262826

[Patent Document 2] Japanese Patent Publication No. 2008-213110

The cross-sectional shapes of the grooves of the wire guides used in the above-mentioned wire saws are known to be V-shaped, U-shaped, etc., and the opening angles of the grooves are also used in various angles such as 40 degrees to 110 degrees. Generally, when the opening angle of the groove is large, the workability of the wire crossing is excellent, and when it is narrow, there is a tendency for the wire retention effect to be good. In order to stabilize the warp value of the workpiece, it is ideal to have a narrow opening angle of the guide groove.

During the use of wire guides, when cutting workpieces, the grooves are gradually deformed by wire cutting. The inventor of this case investigated the change of the Warp value of the workpiece after cutting using a wire saw and found that the Warp value of the workpiece increases along with the average value and deviation when cutting at the beginning of the service life of the wire guide (the beginning of the use of the wire guide).

In order to improve the yield rate of the cut workpiece, it is necessary to obtain a good and stable workpiece shape (Warp value) from the initial use of the wire guide (just after use). Although a certain degree of stable workpiece shape (Warp value) can be obtained by reducing the cutting speed in the initial use of the wire guide, it is not stable in the initial stage, and if the cutting speed is reduced, there is a problem of reduced production capacity (production volume).

The present invention is made to solve the above-mentioned problems, and its purpose is to provide a workpiece cutting method and a workpiece cutting device, which can suppress the reduction of production capacity (production volume) and obtain a good and stable workpiece shape (Warp value) from the initial use of the wire guide (just after the start of use), and obtain workpiece quality that does not depend on the service life of the wire guide.

The present invention is made to achieve the above-mentioned purpose and provides a method for cutting a workpiece. The method for cutting a workpiece includes winding a wire into a spiral shape on a plurality of cylindrical wire guides arranged in parallel with each other in the direction of rotation axis to form a line, and while the wire is moved in the axial direction, the workpiece is pressed against the line, and is cut into a wafer shape at a plurality of locations. The wire guide has a plurality of grooves formed at a predetermined interval along the rotation direction on the outer surface, and the cross-sectional shape of the groove of the unused wire guide has at least: an upper portion of the groove, the groove wall located on the outer surface of the wire guide and opposite to it has a first opening angle (θ ₁ ); a lower portion of the groove, the groove wall located below the upper portion of the groove and opposite to it has a second opening angle (θ ₂ ); and a groove bottom located at the lower end of the groove. The first opening angle (θ ₁ ) and the second opening angle (θ ₂ ) are in a relationship of θ ₁ >θ ₂ . An unused wire and an unused wire guide having the following relationship are used: the maximum value (W0 _,max ) of the groove width at the lower portion of the groove of the unused wire guide is greater than the wire diameter ( _φ0 ) of the unused wire, and the minimum value (W0, _min ) of the groove width at the lower portion of the groove of the unused wire guide is less than the wire diameter ( _φ0 ) of the unused wire; the unused wire is set in a state where it contacts the groove wall at the lower portion of the groove of the unused wire guide and does not contact the bottom of the groove, and the cutting of the workpiece is started when the wire does not contact the bottom of the groove.

According to this workpiece cutting method, the reduction in cutting speed (production capacity) can be suppressed, and the Warp value of the workpiece can be stabilized from the early stage of the wire guide's service life (the early stage of the wire guide's use).

At this time, the workpiece can be cut using a wire guide whose cross-sectional shape at the bottom of the groove is arc-shaped, V-shaped or flat.

This can prevent the wire from coming into contact with the bottom of the wire guide groove at a low cost.

At this time, the workpiece cutting method can be as the workpiece cutting is progressing, the wire cutting the groove wall, and further, the workpiece cutting method can be as the workpiece cutting is progressing, the wire contacting the groove bottom and cutting the groove bottom.

This allows the horizontal vibration of the wire to be suppressed more stably.

At this time, the workpiece cutting method is that the unused wire guide can adopt a wire guide that changes the maximum value (W _0,max ) of the groove width at the lower portion of the plurality of grooves and/or the second opening angle (θ ₂ ) toward the direction of travel of the wire.

This can more stably prevent the wire from coming into contact with the bottom of the wire guide groove.

At this time, a workpiece cutting device can be provided, comprising: a plurality of cylindrical wire guides, which are arranged at predetermined intervals so as to be parallel to the directions of the rotation axes of each other and have grooves formed at predetermined intervals on their respective outer surfaces; a line array, which is formed by winding a spiral wire with a predetermined interval due to the grooves of the wire guides; by rotating the wire guides so that the wire moves in an axial direction while pressing the workpiece against the line array, the workpiece is cut into wafer-like shapes at multiple locations at the same time. The cross-sectional shape of the groove of the wire guide component at least comprises: an upper portion of the groove, located on the outer surface side of the wire guide component and having a first opening angle (θ ₁ ) with the opposite groove wall; a lower portion of the groove, located below the upper portion of the groove and having a second opening angle (θ ₂ ); and a bottom portion of the groove, located at the lower end of the groove; the first opening angle (θ ₁ ) and the second opening angle (θ ₂ ) are in a relationship of θ ₁ >θ ₂ . The unused wire and the unused wire guide are in the following relationship: the maximum value (W _0,max ) of the groove width at the lower portion of the groove of the unused wire guide is greater than the wire diameter (φ ₀ ) of the unused wire, and the minimum value (W _0,min ) of the groove width at the lower portion of the groove of the unused wire guide is less than the wire diameter (φ ₀ ) of the unused wire. When the wire is arranged to contact the groove wall at the lower portion of the groove, the wire does not contact the bottom of the groove of the wire guide.

According to this workpiece cutting device, the reduction in cutting speed (production capacity) can be suppressed, and the Warp value of the workpiece can be stabilized from the early stage of the service life of the wire guide (the early stage of use of the wire guide).

At this time, the cutting device of the workpiece is that the cross-sectional shape of the bottom of the groove of the wire guide can be arc-shaped, V-shaped or flat.

This can prevent the wire from coming into contact with the bottom of the wire guide groove at a low cost.

At this time, the workpiece cutting device is a wire guide in which the maximum value (W _0,max ) of the groove width at the bottom of the plurality of grooves and/or the second opening angle (θ ₂ ) changes toward the moving direction of the wire.

This can more stably prevent the wire from coming into contact with the bottom of the wire guide groove.

As described above, according to the workpiece cutting method of the present invention, the reduction of the cutting speed (productivity) can be suppressed, and the Warp value of the workpiece can be made good and stable from the early stage of the service life of the wire guide (the early stage of the use of the wire guide). In addition, according to the workpiece cutting device of the present invention, the reduction of the cutting speed (productivity) can be suppressed, and the Warp value of the workpiece can be made good and stable from the early stage of the service life of the wire guide (the early stage of the use of the wire guide).

100: Wire saw

101: Line

102: Wire guide

103,103’: reel

104: Crystal Tablet

105: Upper part of the groove

106: Lower part of the groove

107: Side wall

108: Groove bottom

111: Line

R: Radius of curvature

θ ₁ : 1st opening angle

θ ₂ : 2nd opening angle

φ ₀ : Wire diameter (wire diameter of unused wire)

φ: Wire diameter (wire diameter of the used wire)

Figure 1 is an explanatory diagram of the cross-sectional structure of the groove of the wire guide.

FIG2 shows an example of the setting state of the wire of the workpiece cutting device of the present invention in the wire guide groove.

FIG3 shows another example of the arrangement of the wire of the present invention in the wire guide groove.

FIG. 4 shows another example of the arrangement of the wire of the present invention in the wire guide groove.

Figure 5 shows the setting status of the wire in the wire guide groove of Comparative Example 1.

Figure 6 shows the setting status of the wire in the wire guide groove of Comparative Example 2.

Figure 7 shows the change in the wafer's Warp value.

Figure 8 shows an enlarged view of the wire guide in Figure 7 at the beginning of its service life.

Figure 9 shows an overview of a general example of a wire saw.

Figure 10 shows a known example of the setting state of the wire in the wire guide groove.

Figure 11 is a diagram showing the definition of Warp.

[Form used to implement the invention]

The present invention is described in detail below, but the present invention is not limited thereto.

As described above, a workpiece cutting method and a workpiece cutting device are required that can suppress a decrease in production capacity (production volume), obtain a good and stable workpiece shape (Warp value) from the initial use of the wire guide (just after use), and obtain workpiece quality that is not dependent on the service life of the wire guide.

The inventors of this case have repeatedly studied the above-mentioned problems and found that the following workpiece cutting method can suppress the reduction of the cutting speed (production capacity) and make the warp value of the workpiece good and stable from the early stage of the service life of the wire guide (the early stage of the use of the wire guide), thereby completing the present invention. The above-mentioned workpiece cutting method is a method for cutting a plurality of cylindrical wire guides arranged in parallel with each other in the direction of the rotation axis. A wire is wound into a spiral to form a line, and the wire is made to travel in an axial direction while a workpiece is pressed against the line, and is cut into wafers at a plurality of locations at the same time. The wire guide has a plurality of grooves formed at a predetermined interval along a rotation direction on an outer surface, and the cross-sectional shape of the groove of the unused wire guide has at least a first opening angle (θ ₁ ), a groove lower portion having a second opening angle (θ ₂ ) located below and opposite to the groove upper portion, and a groove bottom located at a lower end of the groove, the first opening angle (θ ₁ ) and the second opening angle (θ ₂ ) are in a relationship of θ ₁ >θ ₂ , a maximum value (W _0,max ) of the groove width of the groove lower portion of the unused wire guide is greater than the wire diameter (φ ₀ ) of the unused wire, and a minimum value (W _0,min ) of the groove width of the groove lower portion of the unused wire guide is less than the wire diameter (φ ₀ ) of the unused wire. ), the unused wire and the unused wire guide being in a relationship with each other, the unused wire being arranged in a state where it contacts the groove wall at the lower portion of the groove of the unused wire guide and does not contact the bottom of the groove, and the cutting of the workpiece is started when the wire does not contact the bottom of the groove.

Furthermore, the inventors of this case have repeatedly studied the above-mentioned problems and found that the reduction of the cutting speed (production capacity) can be suppressed by the following workpiece cutting device, and the Warp value of the workpiece can be made good and stable from the early stage of the service life of the wire guide (the early stage of the use of the wire guide), and the present invention has been completed. The above-mentioned workpiece cutting device includes a plurality of rotating shafts arranged at predetermined intervals in parallel with each other, and a predetermined number of rotating shafts are arranged on the outer surface of the wire guide. A plurality of cylindrical wire guides having grooves formed at intervals, and a line array formed by a wire wound into a spiral shape at a predetermined interval in the grooves of the wire guides; by rotating the wire guides, the wires are moved in an axial direction while pressing a workpiece against the line array, and the workpiece is cut into a wafer shape at a plurality of locations, and the cross-sectional shape of the grooves of the wire guides has at least a first opening angle (θ ₁ ), a groove lower portion having a second opening angle (θ ₂ ) located below and opposite to the groove upper portion, and a groove bottom located at the lower end of the groove, the first opening angle (θ ₁ ) and the second opening angle (θ ₂ ) are in a relationship of θ ₁ >θ ₂ , the wire and the wire guide, the maximum value (W _0,max ) of the groove width of the groove lower portion of the wire guide is greater than the wire diameter (φ ₀ ) of the wire, and the minimum value (W _0,min ) of the groove width of the groove lower portion of the wire guide is less than the wire diameter (φ ₀ ) of the wire. ), when the wire is arranged to contact the groove wall at the lower part of the groove, the wire does not contact the bottom of the groove of the wire guide.

The following is an explanation with reference to the diagram.

As a result of the inventor's efforts to investigate, it is speculated that the Warp value of the workpiece increases together with the average value and the deviation at the beginning of the service life of the wire guide when the wire saw is running (cutting the workpiece) The reason is that the wire vibrates due to the side play of the wire. Therefore, the structure of the workpiece cutting device that can prevent the vibration of the wire caused by the side play of the wire was reviewed. As a result, it was found that by setting the wire in the groove of the wire guide so that the wire and the groove of the wire guide are in a certain relationship, and then starting the operation of the wire saw, the reduction in cutting speed (production capacity) can be suppressed, and the Warp value is stable from the beginning of the service life of the wire guide (the beginning of the use of the wire guide) to the end, and the present invention is completed.

First, the workpiece cutting device of the present invention, namely the wire saw, is described. The wire saw includes a plurality of cylindrical wire guides arranged at predetermined intervals so as to be parallel to each other in the direction of the rotation axis and having grooves formed at predetermined intervals on the outer surface, and a line array formed by a wire wound into a spiral shape at predetermined intervals in the grooves of the wire guides. During operation (workpiece cutting), the wire guides are rotated so that the wire moves in the axial direction while pressing the workpiece against the line array, and the workpiece is cut into wafers at multiple locations at the same time.

First, the cross-sectional structure of the groove of the wire guide will be explained using Figure 1 while defining the terms used in this specification. The wire guide shown in Figure 1 is a typical example of an unused state of the wire guide used in the workpiece cutting method and workpiece cutting device of the present invention.

As shown in FIG1 , the cross-sectional shape of the groove of the wire guide has at least an upper groove portion located on the outer surface side of the wire guide and having a first opening angle (θ ₁ ) with the groove wall opposite thereto, a lower groove portion located below the upper groove portion and having a second opening angle (θ ₂ ) with the groove wall opposite thereto, and a groove bottom portion located at the lower end of the groove. That is, in the cross-sectional view (cross-sectional view), it is a two-stage or more structure having two or more opening angles. For example, in the case of a two-stage structure, the upper groove portion is a first-stage groove, and the lower groove portion is a second-stage groove, and the shape changes in the depth direction of the groove.

Here, the first opening angle (θ ₁ ) of the upper groove portion and the second opening angle (θ ₂ ) of the lower groove portion are in the relationship of θ ₁ >θ _2. By using a wire guide having such a relationship, it is possible to achieve both improved workability of wire passing and wire holding effect.

Furthermore, in the workpiece cutting device of the present invention, as shown in FIG. 1 and FIG. 2, the maximum value (W _0,max ) of the groove width of the groove of the wire guide 102, that is, the groove width of the lower part of the groove, between the wire 101 and the wire guide 102 is greater than the wire diameter (φ ₀ ) of the wire 101, and the minimum value (W _0,min ) of the groove width of the lower part of the wire guide groove is less than the wire diameter (φ ₀ ) of the wire. ), when the wire 101 is arranged to contact the groove wall 107 of the groove lower part 106 located below the groove upper part 105, as shown in FIG. 2, the wire 101 contacts the side wall 107 of the groove lower part 106 located below the groove upper part 105, and the wire 101 does not contact the groove bottom 108 of the wire guide 102. That is, when the unused wire 101 is arranged in the groove of the unused wire guide 102, the wire 101 is in a state of being embedded in the groove lower part 106 and not contacting the groove bottom 108 of the wire guide 102, and floats.

Thus, when the wire 101 is set in the groove of the wire guide 102, the lateral play of the wire in the lower part of the groove of the wire guide 102 is reduced, and as a result, the lateral vibration of the wire 101 is suppressed, and even if the cutting speed is not reduced, the warp value of the workpiece cutting device can be stabilized and low from the beginning of use (from the initial stage of use).

Furthermore, when the wire 101 is placed in the groove of the wire guide 102 as described above and the wire saw is started to operate, as the workpiece is cut (the wire saw is operated), the wire 101 removes the side wall 107 of the groove of the wire guide 102 and approaches the groove bottom 108. Then, after a certain time has passed since the workpiece is cut (the wire saw is operated), the wire 101 contacts the groove bottom 108 of the wire guide 102 and removes the groove bottom 108. At this time, since the side wall 107 and the bottom 108 of the groove are removed and the groove shape matching the line shape is formed, the horizontal vibration of the line 101 can be more stably maintained to be suppressed, thus preventing the deterioration of the Warp value.

However, it is needless to say that the effect of the present invention can be exerted by designing a structure in which the wire 101 does not touch the bottom of the groove of the wire guide 102 before the end of the service life of the wire guide. According to the investigation of the inventor of this case, although it also depends on the material used, the wire 101 has a tendency to become thinner by about 10% with use. This situation can be taken into account to set the relationship between the groove shape and the wire diameter (φ ₀ ).

Here, the cross-sectional shape of the groove bottom 108 of the wire guide 102 is not particularly limited, and can be an arc shape, a V shape, or a flat shape. FIG. 2-4 shows an example of setting the wire 101 in such a wire guide 102. In addition, the matters described in FIG. 2 are appropriately omitted in the following description of FIG. 3-6. In addition, FIG. 3-6 only shows one groove.

The groove of the above shape can be manufactured relatively easily (at low cost) and with high precision, and can prevent the wire 101 from contacting the bottom of the groove of the wire guide 102 at low cost. In particular, as shown in FIG3, if the cross-sectional shape of the groove bottom 108 is an arc shape, and its radius of curvature R does not reach the radius of the wire, or as shown in FIG2, if the cross-sectional shape of the groove bottom 108 is a V-shape (that is, it can also be said that R=0), it can more reliably prevent the wire 101 from contacting the groove bottom 108 of the wire guide 102 at the beginning of the service life of the wire guide from the time of installation, so it is better. Furthermore, as shown in FIG. 4 , as long as the minimum value of the trench width of the lower portion 106 of the trench does not reach the wire diameter, the wire can be prevented from contacting the trench bottom 108 , and the trench bottom 108 can also be flat.

Furthermore, the wire guide may be a wire guide in which the maximum value (W _0,max ) of the groove width at the bottom of the plurality of grooves and/or the second opening angle (θ ₂ ) changes in the direction of travel of the wire. As described above, the wire tends to become thinner by about 10% due to use. Therefore, the portion of the workpiece with a long cutting process is thinner than the unused portion or the portion with a short cutting process. In this way, since the wire width of the wire in use varies depending on the portion of the wire, if the wire guide is a wire guide in which the shape of the plurality of grooves changes in the direction of travel of the wire as described above, a non-contact state between the wire and the bottom of the groove of the wire guide can be stably achieved at the beginning of the service life of the wire guide.

The first opening angle (θ ₁ ) of the upper portion of the groove of the wire guide 102 is preferably 60 to 110°. If it is set in this range, the cutting device has better workability in the wire handover operation. In addition, the second opening angle (θ ₂ ) of the lower portion of the groove is preferably 20 to 60°. If it is set in this range, the cutting device can hold the wire more stably and manufacture wafers with a low warp value.

When setting the wire in the groove of the wire guide 102, at the beginning of use, it is advisable to set the shape of the wire and the groove so that the upper part of the wire is located above the upper end of the lower part of the groove (groove opening). When this is done, the wire guide 102 can extend its service life.

In addition, the maximum value of the groove width (W _0,max ) of the groove lower part, that is, the groove width of the groove mouth (the boundary between the groove upper part and the groove lower part) of the groove lower part and the wire diameter (φ ₀ ) are preferably set to W _0,max /φ ₀ =1.01~1.30. With such a relationship, the wire can be more reliably placed in the groove lower part, and the lateral vibration of the wire can be more reliably prevented.

Furthermore, the curvature radius R of the groove bottom and the wire diameter (φ ₀ ) are preferably set so that R/φ ₀ is less than 0.5. With such a relationship, the non-contact state between the wire and the groove bottom 108 of the wire guide 102 can be more stably and reliably achieved at the initial stage of cutting.

The wire guide 102 can be used to press a wire guide with a resin such as polyurethane (ester or ether) around a steel cylinder. In addition, the workpiece cutting device can be used regardless of whether it is a free abrasive type or a fixed abrasive type.

The example of the groove shape of the wire guide groove shown above shows a shape with a vertex at the connection between the upper part of the groove and the lower part of the groove, which can also be connected smoothly.

Next, the workpiece cutting method of the present invention is described. By cutting the workpiece using the above-mentioned workpiece cutting device, the reduction of production capacity (production volume) can be suppressed, and a good and stable workpiece shape (Warp value) can be obtained from the initial use of the wire guide (just after the start of use), and the quality of the workpiece can be obtained that is not dependent on the service life of the wire guide.

First, before starting to cut the workpiece, the cutting device is set up. The wire is wound into a spiral shape on multiple cylindrical wire guides that are set in parallel with each other's rotation axes to form a line.

As described above, the cross-sectional shape of the groove of the unused wire guide 102 has at least a groove upper portion 105 located on the outer surface side of the wire guide and opposite to the groove wall 107 having a first opening angle (θ ₁ ), a groove lower portion 106 located below the groove upper portion 105 and opposite to the groove wall 107 having a second opening angle (θ ₂ ), and a groove bottom 108 located at the lower end of the groove, and the first opening angle (θ ₁ ) and the second opening angle (θ ₂ ) are in a relationship of θ ₁ >θ ₂ . Furthermore, the maximum value (W _0,max ) of the groove width of the groove lower portion 106 of the unused wire guide is greater than the wire diameter (φ ₀ ) of the unused wire 101 , and the minimum value (W _0,min ) of the groove width of the groove lower portion 106 of the unused wire guide 102 does not reach the wire diameter (φ ₀ ) of the unused wire 101 (W _0,min <φ ₀ ≦W _0,max ). By using the unused wire 101 and the unused wire guide 102 in such a relationship, the unused wire 101 is set in a state of contacting the groove wall 107 of the groove lower portion 106 of the unused wire guide 102 and not contacting the groove bottom 108. When the wire does not contact the groove bottom 108, the cutting of the workpiece is started, thereby suppressing the reduction of production capacity (production volume), and obtaining a good and stable workpiece shape (Warp value) from the initial use of the wire guide 102 (just after the use begins), and obtaining the quality of the workpiece that does not depend on the service life of the wire guide 102.

As described above, when the wire is placed in the wire guide groove and the wire saw is started to operate, immediately after the operation starts, the wire is supported (held) by the side wall of the lower part of the groove. As the workpiece is cut (the wire saw is operated), the wire removes the side surface of the wire guide groove and approaches the groove bottom, and the cutting progresses while forming the most suitable groove shape according to the wire diameter. Furthermore, when a certain time has passed since the workpiece is cut (the wire saw is operated), the wire contacts the groove bottom of the wire guide and removes the groove bottom. In this way, even when the wire contacts the bottom of the wire guide groove, it can move forward while removing the groove, so the lateral vibration of the wire is still suppressed, thus not causing the deterioration of the Warp value.

Furthermore, as described in the device, when a wire guide is used to cut a workpiece by changing the shape of multiple grooves in the direction of the wire as described above, a non-contact state between the wire and the bottom of the groove of the wire guide can be stably achieved at the beginning of the service life of the wire guide. Furthermore, since there is no need to reduce the cutting speed, the decrease in production capacity can be suppressed.

[Implementation example]

The present invention is described in detail below using embodiments as examples, but this does not limit the present invention.

(Implementation example)

The unused (new) wire guide used a wire guide having groove shape parameters of 90 degrees for the first opening angle (θ ₁ ) of the upper groove, 40 degrees for the second opening angle (θ ₂ ) of the lower groove, 130 μm for the depth of the lower groove, 140 μm for the groove width (W _0,max ) of the groove opening at the lower groove, and 0.030 mm for the radius of curvature R of the groove bottom. When an unused (new) wire having a wire diameter (φ ₀ ) of 0.13 mm was set in such a wire guide, the wire was set in a state where it was in contact with the groove wall of the lower groove of the wire guide and did not contact the groove bottom (see FIG. 3 ).

Next, a single-crystal silicon ingot with a diameter of 200 mm was used as the workpiece to be cut, and a wire saw device was used to perform the cutting process. The shape of the cut silicon wafer was measured, and the warp value was calculated.

(Comparison Example 1)

The unused (new) wire guide used a wire guide having a cross-sectional shape of a V-groove with a groove opening angle of 90 degrees and a groove width of 0.6 mm (600 μm) on the outer surface of the wire guide. Except for this point, the cutting process and the shape measurement of the silicon wafer obtained by cutting were carried out under the same conditions as Example 1. When the wire is set in the wire guide used in Comparative Example 1, the state shown in Figure 5 is formed. At the time of setting the wire in the groove, the wire has a so-called clearance in the groove in the horizontal direction.

(Comparison Example 2)

The unused (new) wire guide used a wire guide having groove shape parameters such as the first opening angle (θ ₁ ) of the upper groove being 90 degrees, the second opening angle (θ ₂ ) of the lower groove being 40 degrees, the depth of the lower groove being 130 μm, the groove width (W _0,max ) of the groove opening of the lower groove being 190 μm, and the curvature radius R of the groove bottom being 0.065 mm. When a new wire having a wire diameter (φ ₀ ) of 0.13 mm was set in such a wire guide, the wire was in contact with the groove bottom of the wire guide (see FIG. 6 ). At the time when the wire was set in the groove, the wire had a so-called play in the lateral direction in the groove. In addition, under the same conditions as in Example 1, cutting processing and shape measurement of the cut silicon wafers were performed.

In addition, representative values of cutting processing conditions (including the above conditions) are shown in Table 1 for reference.

FIG7 shows the change of the wafer's Warp value. The horizontal axis is a selection of processing batches over a certain period of time from the beginning of the service life of the wire guide. The vertical axis shows the Warp value. The graph is based on the average value of the Warp value of every ten batches. In addition, to compare the embodiment with Comparative Examples 1 and 2, the average value of thirty batches from the beginning of the cutting process of Comparative Example 1 is used as the benchmark 1, and the relative values are compared. As shown in FIG7, it can be seen that in Comparative Example 1, the number of cutting process batches until the Warp value is low and stable is the largest.

FIG8 is a diagram that expands the range of the three diagrams (30 batches) of the wire guide parts in the early stage of their service life in FIG7. As shown in FIG8, in the embodiment, a low and stable Warp value was obtained from the initial stage. In comparison example 2, as shown in FIG7, the result was stable at an earlier stage than comparison example 1, but as shown in FIG8, the Warp value was high and had deviations in the initial stage. Based on the data of the initial 30 batches shown in FIG8, a comparison of the wire guide parts in the early stage of their service life (30 batches) was conducted. As a result, in the embodiment, a workpiece with a stable Warp value and deviation compared to comparison examples 1 and 2 and high quality was obtained.

The conditions and evaluation results of the above-mentioned embodiments, comparative examples 1 and 2 are summarized in Table 2.

[Table 2]

As shown in FIG7 , in the embodiment, since the wire is properly embedded in the lower part of the wire guide groove from the beginning of use, and there is no wire play, the Warp value is considered to be stable from the beginning. On the other hand, in the embodiment and comparative examples 1 and 2, the Warp values between batches and within batches are low and stable. This is because the side surfaces (side walls) and the bottom surface of the wire guide groove are gradually polished toward the bottom of the groove due to the movement of the wire, and the shapes of the side surfaces (side walls) and the bottom surface of the groove gradually conform to the shape of the wire. In Comparative Example 2, although the wire is placed in the lower part of the groove of the wire guide, it is placed in contact with the bottom of the groove, so the wire play cannot be eliminated. Compared with the embodiment, the Warp value is chaotic in the first few dozen batches.

As mentioned above, since the wire wears and becomes thinner due to use, the ratio of the groove width (W _0,max ) between the grooves and the wire diameter (φ) varies depending on the usage status. When the wire is set in the wire guide groove, in order to more stably maintain the non-contact state between the groove bottom and the wire in the initial period of the wire life, it is advisable to add the change of the wire diameter (φ) to set the relationship with the groove width (W _0,max ) between the grooves of the unused wire guide grooves. Therefore, for Example and Comparative Example 2, the ratio of the groove width (W _0,max ) of the groove opening of the unused wire guide to the wire diameter (φ) (groove opening/wire diameter = W _0,max /φ), and the ratio of the curvature radius (R) of the groove bottom of the unused wire guide to the wire diameter (φ) (groove bottom R/wire diameter = R/φ) were investigated. The results are shown in Table 3.

As shown in Table 3, it can be seen that when the wire diameter (φ ₀ ) is used as a reference, the groove width (W _0,max ) of the groove mouth of the wire guide is preferably set in the range of 1.01~1.30, and the curvature radius R of the groove bottom of the groove is preferably set in the range of less than 0.5.

For example, as described above, when the wire guide changes the shape of a plurality of grooves so that the groove width (W _0,max ) of the groove openings of the grooves gradually narrows toward the running direction of the wire, it is effective to set it within the above range.

As mentioned above, it can be seen that according to the embodiment of the present invention, the warp can be formed to a stable and good level from the beginning of using the wire guide, and the workpiece shape quality can be obtained that is not dependent on the service life of the wire guide, and the workpiece shape quality can be maintained without reducing the cutting speed (production capacity).

In addition, the present invention is not limited to the above-mentioned embodiments. The above-mentioned embodiments are illustrative, and any structure having substantially the same technical concept as that described in the scope of the patent application of the present invention and exerting the same effect is included in the technical scope of the present invention.

101: Line

102: Wire guide

105: Upper part of the groove

106: Lower part of the groove

107: Side wall

108: Groove bottom

φ ₀ : Line diameter

Claims (10)

A method for cutting a workpiece, wherein a wire is wound into a spiral shape on a plurality of cylindrical wire guides arranged in parallel with each other in the direction of rotation axis to form a line, and the wire is made to travel in the axial direction while the workpiece is pressed against the line, and the workpiece is cut into a wafer shape at a plurality of locations at the same time; the wire guide has a plurality of grooves formed at a predetermined interval along the rotation direction on the outer surface; the cross-sectional shape of the groove of the unused wire guide has at least: an opening angle of a first opening angle (θ ₁ ) on the upper portion of the groove, and an opening angle of a groove wall located on the side of the outer surface of the wire guide and facing the groove wall at the lower portion of the groove, which is adjacent to and opposite to the upper portion of the groove, is a second opening angle (θ ₂ ); and a bottom of the groove, located at the lower end of the groove; the first opening angle (θ ₁ ) and the second opening angle (θ ₂ ) are in a relationship of θ ₁ >θ ₂ ; the unused wire and the unused wire guide are in the following relationship: the maximum value (W _0,max ) of the groove width at the lower portion of the groove of the unused wire guide is greater than the wire diameter (φ ₀ ) of the unused wire, and the minimum value (W _0,min ) of the groove width at the lower portion of the groove of the unused wire guide is less than the wire diameter (φ ₀ ); setting the unused wire to contact the groove wall at the bottom of the groove of the unused wire guide and not contact the bottom of the groove; starting the cutting of the workpiece when the wire does not contact the bottom of the groove. For example, a method for cutting a workpiece as described in item 1 of the patent application, wherein a wire guide having a cross-sectional shape of a groove bottom that is arc-shaped, V-shaped, or flat is used. A method for cutting a workpiece as in item 1 of the patent application, wherein the wire cuts the groove wall as the cutting of the workpiece proceeds. A method for cutting a workpiece as described in item 2 of the patent application, wherein the wire cuts the groove wall as the cutting of the workpiece proceeds. A method for cutting a workpiece as claimed in any one of items 1 to 4 of the patent application scope, wherein, as the cutting of the workpiece proceeds, the wire contacts the bottom of the groove and cuts the bottom of the groove. A method for cutting a workpiece as claimed in any one of items 1 to 4 of the patent application, wherein the unused wire guide is a wire guide that gradually reduces the maximum value (W _0,max ) of the groove width at the lower part of the plurality of grooves and/or the second opening angle (θ ₂ ) toward the direction of travel of the wire. A method for cutting a workpiece as claimed in claim 5, wherein the unused wire guide is a wire guide which gradually reduces the maximum value (W _0,max ) of the groove width at the lower part of the plurality of grooves and/or the second opening angle (θ ₂ ) toward the direction of travel of the wire. A workpiece cutting device comprises: a plurality of cylindrical wire guides, which are arranged at predetermined intervals so that the rotation axis directions are parallel to each other and each of which has grooves formed at predetermined intervals on its outer surface; and a line array, which is formed by winding a wire in a spiral shape at predetermined intervals in the grooves of the wire guides; by rotating the wire guides, the wire is moved in an axial direction while the workpiece is pressed against the line array, and the workpiece is cut into wafer shapes at a plurality of locations at the same time, wherein the cross-sectional shape of the groove of the unused wire guides at least has: an opening angle of a first opening angle (θ ₁ ); the opening angle of the groove wall adjacent to and opposite to the upper portion of the groove is a second opening angle (θ ₂ ); and the groove bottom is located at the lower end of the groove; the first opening angle (θ ₁ ) and the second opening angle (θ ₂ ) are in a relationship of θ ₁ >θ ₂ , the unused wire and the unused wire guide are such that the maximum value (W _0,max ) of the groove width of the unused wire guide at the lower portion of the groove is greater than the wire diameter (φ ₀ ) of the unused wire, and the minimum value (W _0,min ) of the groove width of the unused wire guide at the lower portion of the groove is less than the wire diameter (φ ₀ ) of the unused wire. ), when the unused wire is arranged to contact the groove wall at the lower part of the groove, the unused wire does not contact the bottom of the groove of the unused wire guide. For example, in the workpiece cutting device of item 8 of the patent application scope, the cross-sectional shape of the bottom of the groove of the unused wire guide is arc-shaped, V-shaped or flat. A workpiece cutting device as claimed in any one of item 8 or 9 of the patent application scope, wherein the unused wire guide is a wire guide in which the maximum value of the groove width (W _0,max ) at the lower part of the plurality of grooves and/or the second opening angle (θ ₂ ) gradually decreases toward the direction of travel of the wire.

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