Wire saw device and workpiece cutting method

Abstract

The present invention provides a wire saw apparatus and cutting method that can easily cut wafers from workpieces such as semiconductor ingots in a shorter time than conventional methods. [Solution] A fixing mechanism for fixing the workpiece W, and a cutting mechanism for cutting the workpiece W with a wire 7, A wire saw device comprising a closing mechanism for closing part or all of the cut end of a workpiece created behind the workpiece W as it is cut by the wire 7, wherein the fixing mechanism sandwiches the workpiece W between a first vertical plate 25 and a second vertical plate 25, and the two vertical plates 25 and the bottom plate 27 are in contact and fixed together.

Description

Technical Field

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[0001] The present invention relates to a wire saw apparatus and a workpiece cutting method for cutting a thin wafer from a workpiece such as a semiconductor ingot.

Background Art

[0002] Conventionally, when manufacturing a semiconductor wafer typified by a silicon wafer, although not shown, a cylindrical semiconductor ingot solidified from a silicon melt in a crucible is cut into blocks of an appropriate length, and its peripheral portion is ground to a target diameter. Then, the blocked semiconductor ingot is cut (sliced) into a wafer shape by a wire saw to manufacture a semiconductor wafer.

[0003] In recent years, as next-generation semiconductors, silicon carbide (SiC) and gallium nitride (GaN), which have excellent dielectric breakdown field strength, a large bandgap, high hardness, and high thermal conductivity, have been studied and developed.

[0004] Since GaN has high hardness, it becomes impossible to easily slice a semiconductor ingot with a wire saw apparatus, and the working time becomes longer inevitably. Also, although mass production technology regarding the production of an ingot by crystal growth has not been established yet, on the other hand, there is a desire to efficiently create wafers.

[0005] FIG. 9 is an overall front view of a conventional wire saw apparatus 100. A conventional fixing mechanism 30 includes a holding table 39 that holds a workpiece W of a workpiece via a workpiece table 50 and a dummy member 51, a table base 47 that horizontally moves the holding table 39 in the Y direction (the front-rear direction in FIG. 9), and a lifting frame 35 that raises and lowers the holding table 39.

[0006] The workpiece W is bonded to a dummy member 51 made of carbon, ceramic, or the like, and then bonded to the workpiece table 50 via the dummy member. The workpiece table 50 to which the workpiece W is fixed is fixed to the holding table 39. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2022-52269 [Overview of the project] [Problems that the invention aims to solve]

[0008] The wafer manufacturing method described in Patent Document 1 shortens the lead time by placing an auxiliary member between the workpiece (e.g., semiconductor ingot) and the support member (dummy member). However, it still uses adhesive for fixing, which presents an inefficiency because it requires waiting for the adhesive to dry before cutting and removing the adhesive after cutting to take out the wafer. Furthermore, wafer cracking during cutting, peeling of the adhesive after cutting, and cracking or chipping of the wafer during wafer removal were also issues.

[0009] This invention has been made in view of these considerations, and aims to provide a wire saw device and a workpiece cutting method that can easily cut wafers from workpieces such as semiconductor ingots in a shorter time than conventional methods. [Means for solving the problem]

[0010] In other words, the present invention relates to the following invention. [1] A wire saw device comprising a fixing mechanism for fixing a workpiece, a cutting mechanism for cutting a workpiece with a wire, and a closing mechanism for closing part or all of the cut end of the workpiece created behind the wire cutting the workpiece, wherein the fixing mechanism sandwiches the workpiece between a first vertical plate and a second vertical plate, and the two vertical plates and the bottom plate are in contact and fixed together. [2] The wire saw apparatus according to [1], characterized in that at least one of the first vertical plate, the second vertical plate, and the bottom plate is a magnet, and the others are fixed by magnetic coupling using magnetic materials that can be fixed with magnets. [3] The wire saw device according to [1], characterized in that the first vertical plate, the second vertical plate, and the bottom plate are connected by an L-shaped bracket in which one vertical plate and the bottom plate are integrated, and the other vertical plate is a magnet, and the magnetic coupling by the magnetic force of the magnet is such that the horizontal surface of the L-shaped bracket and the horizontal surface (narrow surface) of the magnet plate stick together strongly, while the vertical surface of the L-shaped bracket and the vertical surface (wide surface) of the magnet stick together weakly. [4] The wire saw device according to [1], characterized in that it is a single wire saw. [5] The wire saw device according to [1], characterized in that it is a multi-wire saw. [6] The wire saw device according to any one of [1] to [5], characterized in that the blocking mechanism has a blocking wire that moves up and down or swings in synchronization with the up and down movement mechanism or swinging mechanism of the cutting wire, thereby blocking a part of the cut end of the workpiece. [7] A cutting method using a wire saw device, wherein the wire saw device is a wire saw device described in any of [1] to [5] above. [8] The workpiece cutting method according to [7], characterized in that the blocking mechanism has a blocking wire that moves up and down or swings in synchronization with a vertical movement mechanism or swinging mechanism of the cutting wire, thereby blocking a part of the cut surface of the workpiece.

[0011] In this context, "contact and fixation" includes methods such as those that are originally one piece, adhesive fixation, fitting, screwing, and magnetic coupling using magnetic materials where one side is magnetic and the other side is magnetic. [Effects of the Invention]

[0012] According to the present invention, there is provided a wire saw apparatus and a workpiece cutting method capable of shortening the processing time of a wafer from a workpiece such as a semiconductor ingot (particularly, shortening the time for attachment before cutting and removal after cutting) as compared with the conventional method.

[0013] Specifically, it is possible to shorten the time for fixing the workpiece before cutting and the time for taking out the wafer after cutting. Further, there is a demand to cope with various workpiece shapes, and this has been realized.

Brief Description of the Drawings

[0014] [Figure 1] FIG. 1 is an overall front view of a wire saw apparatus according to a first embodiment of the present invention. [Figure 2] FIG. 2 is an explanatory view immediately before the start of cutting according to a second embodiment of the present invention. [Figure 3] FIG. 3 is an explanatory view during cutting according to a second embodiment of the present invention. [Figure 4] FIG. 4 is an explanatory view immediately after the end of cutting according to a second embodiment of the present invention. [Figure 5] FIG. 5 is a side view of a fixing mechanism according to a third embodiment of the present invention. [Figure 6] FIG. 6 is a side view of a fixing mechanism according to a fourth embodiment of the present invention. [Figure 7] FIG. 7 is a side view of a fixing mechanism according to a fifth embodiment of the present invention. [Figure 8] FIG. 8 is an explanatory view of an arc swing mechanism according to a sixth embodiment of the present invention. [Figure 9] FIG. 9 is an overall front view of a conventional wire saw apparatus.

Modes for Carrying Out the Invention

[0015] Hereinafter, a wire saw device and a workpiece cutting method according to an aspect of the present disclosure will be described in detail with reference to the illustrated embodiments. Note that the drawings include schematic ones and may not reflect actual dimensions or ratios. Specifically, in FIGS. 2 to 4, schematic descriptions are provided, and even when members actually abut against each other, there may be cases where a gap is provided between the members in the description.

[0016] FIG. 1 is an overall front view of a wire saw device 1 according to a first embodiment of the present invention. In the present embodiment, first, an example of a single wire saw in which one wire 7 contacts a workpiece W fixed to a fixing mechanism 30 will be described. The wire (cutting wire) 7 will be described based on the case where, for example, a fixed abrasive grain wire in which abrasive grains such as diamond are fixed to the surface of a core wire by electrodeposition is used. On the other hand, a free abrasive grain method can also be adopted, but the description regarding these differences will be omitted.

[0017] As shown in FIG. 1, a supply reel 4, a recovery reel 5, a plurality of guide rollers 6, 11, tension rollers 8, 10, and groove rollers 9a, 9b, 9c are provided on the front portion of a machine frame 3 erected upright, and a fixing mechanism 30 is provided below the groove rollers 9a, 9b.

[0018] The wire 7 is wound around the supply reel 4. The wire 7 is fed out from the supply reel 4, passed over the guide roller 6 and the tension roller 8, then spanned over the groove rollers 9a, 9b, and then wound around the recovery reel 5 via the tension roller 10 and the guide roller 11.

[0019] Motors (not shown) are connected to the supply reel 4 and the recovery reel 5, and by rotationally driving the supply reel 4 and the recovery reel 5 while reversing them in the forward and reverse directions, the wire 7 runs in the reciprocating direction. Further, the tension rollers 8, 10 are configured to swing in the direction of the arrows by a drive mechanism (not shown), and by swinging these tension rollers 8, 10, an appropriate tension is applied to the wire 7.

[0020] In Figure 1, the wire saw device 1 is pivotally supported in a triangular arrangement at its center, with groove rollers 9a and 9b forming the base and groove roller 9c forming the apex. In the case of a single wire saw, groove rollers 9a and 9b rotate while being driven by the wire 7, so a drive source is usually not required. The cutting mechanism 2 consists of the wire 7, supply reel 4, retrieval reel 5, motor (not shown), tension rollers 8 and 10, and groove rollers 9a, 9b, and 9c.

[0021] To cut the workpiece W, the workpiece W is fixed by the fixing mechanism 30, and the position of the table base 47 or the bottom plate 27 on the table base is adjusted so that the cutting surface of the workpiece W is directly below the wire 7. Next, the wire 7 is moved back and forth by the cutting mechanism 2, and the workpiece W is raised so that the wire 7 and the workpiece W come into contact and are cut. The motor 7 fixed to the motor fixing frame 41 drives the lifting frame 35 up and down via the drive pulley 42, belt 44, driven pulley 43, ball screw 36, and nut member 37, causing the table base 47 connected to the lifting frame 35 to move up and down, thereby controlling the vertical movement of the workpiece W.

[0022] Figures 2 to 4 illustrate the workpiece cutting method in the second embodiment of the present invention. Figure 2 is an explanatory diagram of the moment immediately before the start of cutting in the second embodiment of the present invention. First, the fixing mechanism will be described. The workpiece W located in the center is sandwiched between the first vertical plate 25 and the second vertical plate 26, and a bottom plate 27 is placed below it. The first vertical plate 25 and the second vertical plate 26 are magnetic materials (for example, iron plates) that can be fixed with magnets, and the bottom plate 27 is a magnetic plate. Since the two vertical plates 25 and 26 are fixed to the bottom plate 27, the workpiece W can also be fixed. Alternatively, the two vertical plates 25 and 26 may become magnets due to the magnetic force of the bottom plate 27 and have a force in the direction that sandwiches the workpiece W. In other words, the fixing mechanism consists of the first vertical plate 25, the second vertical plate 26, and the bottom plate 27, and the fixing mechanism fixes the workpiece W. The magnets may be magnets whose magnetic force can be turned on and off by a switch.

[0023] Figure 3 is an explanatory diagram showing the cutting process in the second embodiment of the present invention. Figure 4 is an explanatory diagram showing the cutting process immediately after completion in the second embodiment of the present invention.

[0024] Wire 7 cuts through the workpiece W, while occlusion wires 50a, 50b, 50c, 50d, and 50e fill in part of the gap at the cut end of the workpiece W. Figure 2 shows the point where occlusion wire 50a begins to enter the gap in the workpiece W, some time after wire 7 has started cutting.

[0025] Figure 4 shows the wire 7 cutting through the workpiece W, at which point all the blocking wires 50a, 50b, 50c, 50d, and 50e have entered the gap and filled a portion of it. The blocking mechanism consists of a means for moving the blocking wires up and down (not shown) and the blocking wires 50a, 50b, 50c, 50d, and 50e. This blocking mechanism prevents the workpiece W from cracking due to the pressing force applied by the workpiece W by filling the gap. Furthermore, if a free abrasive grain method is adopted, the blocking wires 50a, 50b, 50c, 50d, and 50e can also be expected to reduce the unevenness of the cut surface.

[0026] Because there is a space between the workpiece W and the base plate 27, it is easy to determine when the workpiece W has finished cutting by measuring the force applied to the wire 7. Furthermore, it is economical because the base plate 27 can be reused. However, to prioritize cutting accuracy, the workpiece W and the base plate 27 may be in contact. Alternatively, a buffer member may be interposed between the workpiece W and the base plate 27. For example, protrusions may be provided on the vertical plates to prevent the buffer member from shifting. Alternatively, the buffer member may be made of an elastic material such as rubber to prevent shifting. However, contact between the workpiece W and the base plate 27 does not necessarily improve cutting accuracy. Note that the closure wire vertical movement means (not shown) may move vertically on the workpiece W side, while the wire 7 and closure wires 50a, 50b, 50c, 50d, and 50e sides may not move vertically.

[0027] Figure 5 is a side view of a fixing mechanism according to a third embodiment of the present invention. The fixing mechanism in this embodiment consists of an L-shaped bracket in which a first vertical plate 25 and a bottom plate 27 (see Figures 2 to 4) are integrated, and a magnet plate 29 that replaces the second vertical plate 26 (see Figures 2 to 4). The horizontal surface (narrow surface) of the magnet plate 29 rests directly on the bottom surface of the L-shaped bracket 28, resulting in a strong, stable bond. The vertical surface of the L-shaped bracket 28 and the vertical surface (wide surface) of the magnet plate 29 act to attract with a weak force because the workpiece W is sandwiched between them.

[0028] Figure 6 is a side view of a fixing mechanism according to a fourth embodiment of the present invention. Here, an example is shown of cutting two workpieces W simultaneously. In other words, it is a multi-wire saw (a multi-wire saw is a device that cuts multiple wafers simultaneously by moving a wire array stretched at a predetermined pitch at high speed and pressing the workpieces against the wire array). In this third embodiment, each of the two workpieces W is sandwiched between two vertical plates 25 and 26.

[0029] Figure 7 is a side view of a fixing mechanism according to a fifth embodiment of the present invention. Here again, an example is shown of cutting two workpieces simultaneously, and it is a multi-wire saw. In this fifth embodiment, of the vertical plates 25 and 26 that sandwich the workpiece W in the fourth embodiment, two adjacent vertical plates 25 and 26 are made into a single vertical plate 26a. This reduces the cost of parts and simplifies installation work by making two plates into one. On the other hand, care must be taken because the cutting location, that is, the path of the wire 7, is affected by the thickness accuracy of the vertical plate 26a.

[0030] In the second, fourth, and fifth embodiments described above, two vertical plates sandwich and fix the wake W (semiconductor ingot). However, the two planes (bottom surfaces) of the cylindrical shape of the semiconductor ingot are not necessarily perfectly parallel. Furthermore, the planes themselves are not necessarily perfectly smooth. In other words, we want to be able to handle all kinds of surfaces, such as those that are mirror-finished, rough, or contain irregularities. Therefore, it is advisable to interpose an intermediate member (not shown) between the vertical plates and the workpiece W. The intermediate member may be an elastic member that can absorb the shape of irregularities. In addition, an adhesive member may be used for the intermediate member to prevent the workpiece W and the vertical plates from shifting position during cutting. Note that the workpiece W is not limited to a cylindrical shape and may be of various shapes.

[0031] Figure 8 is an explanatory diagram of an arc-shaped oscillating mechanism according to the sixth embodiment of the present invention. When the workpiece W moves linearly relative to the wire 7, a pivot point is provided at or near this point on the straight line within the cutting surface of the workpiece W, and the running position of the wire 7 on the workpiece W is switched (switched in the direction of oscillation) between the top side and the left and right base sides of the remaining cut portion as the cutting progresses. More specifically, it is preferable to switch the direction of oscillation so that the running direction of the workpiece W and the wire 7 is always directed from the top side to the base side of the remaining cut portion where the cut edge of the workpiece W is substantially arc-shaped. Note that the control method of the arc-shaped oscillating mechanism according to this embodiment is not limited to the method described in the specification.

[0032] The oscillating mechanism (not shown) includes an oscillating support plate (not shown) to which the ends of groove rollers 9a, 9b, and 9c are pivotally attached, and an oscillating motor (not shown) that drives the oscillating support plate. When the oscillating motor rotates, rotational force is transmitted to the oscillating support plate, causing it to rotate to the right or left by a predetermined angle. The oscillating support plate oscillates by alternately rotating clockwise and counterclockwise. The oscillating angle at this time is set, for example, to 2 to 10°.

[0033] The control unit (not shown) primarily controls the amount of abrasive grains supplied to the wire 7, the reciprocating speed of the wire 7, and the oscillation angle of the wire 7 by the oscillation means (not shown). Furthermore, it also switches the oscillation direction so that the direction of travel of the wire 7 is always directed from the top side to the bottom side of the cut edge of the workpiece W, where the cut edge is arc-shaped.

[0034] As the wire 7 travels in the direction of cutting the workpiece W, always from the top to the bottom of the remaining cut portion, excess abrasive grains tend to adhere to the gap between the wire 7 and the uncut surface of the remaining cut portion each time a cut is made. Figure 8 shows that abrasive grains and chips 14 have entered the gap between the surface to be cut and the wire 7. In other words, the chips can be expected to contribute to the cutting of the workpiece W in the same way as the abrasive grains.

[0035] The arc oscillation mechanism stabilizes the amount of polishing per reciprocating motion of the wire 7 at a large value, thereby shortening the cutting time and resulting in wafers with excellent flatness. The closure wires 50a, 50b, 50c, 50d, and 50e may be moved up and down in synchronization with the vertical movement mechanism of the wire 7. Alternatively, the closure wires 50a, 50b, 50c, 50d, and 50e may be oscillated in synchronization with the oscillation mechanism of the wire 7. This allows the closure wires 50a, 50b, 50c, 50d, and 50e to be smoothly inserted into the cut end of the workpiece W behind the wire 7.

[0036] Although this embodiment has been described using a down-cut method in which the workpiece W is cut from top to bottom, it is also possible to use an up-cut method in which the workpiece W is cut from bottom to top.

[0037] The wire saw apparatus according to the first embodiment is a fixed abrasive type, but is not limited thereto. For example, the sixth embodiment uses free abrasives. In the free abrasive type, it is preferable to provide a nozzle (not shown) for supplying a slurry containing abrasives to the contact portion between the workpiece W and the wire 7. Even in the fixed abrasive type, it is preferable to provide a nozzle (not shown) for supplying cutting fluid to the contact portion between the workpiece W and the wire 7.

[0038] From the above, the present invention can be performed without using adhesive for fixing, there is no need to wait for the adhesive to dry before cutting, and the laborious work of peeling off the adhesive and removing the wafer after cutting is eliminated. In other words, the present invention can provide a wire saw device and workpiece cutting method that can shorten the processing time for wafers from workpieces such as semiconductor ingots compared to conventional methods (in particular, the time for mounting before cutting and removing after cutting can be shortened).

[0039] The workpiece W used in this invention is not limited to materials such as silicon, SiC, or GaN, but this invention is particularly effective for processing GaN. [Explanation of Symbols]

[0040] Double job 1. Wire saw device 2 Cutting mechanism 3 machine frame 4. Supply Reels 5. Retrieval reel 6 Guide rollers 7 wires 8 Tension Roller 9a, 9b, 9c groove rollers 10 Tension Rollers 11 Guide rollers 12a, 12b, 12c, 12d 14 Abrasive grains and chips 20a, 20b, 20c Roller frame 21 Ball screw 25 First vertical board 26, 26a Second vertical board 27 Bottom plate 28 L-shaped brackets 29 Magnetic plate 30 Fixing mechanism 32 Sliders 34 Nut component 35 Lifting Frame 36 Ball Screw 37 Nut component 39 Holding Table 40 motors 41 Motor mounting frame 42 Drive pulley 43 Driven pulley 44 belts 47 Table stand 50a, 50b, 50c, 50d, 50e occlusion wire

Claims

1. A fixing mechanism for securing the workpiece, A cutting mechanism that cuts the workpiece with a wire, It includes a closing mechanism that closes part or all of the cut end of the workpiece created behind the workpiece as it is cut by the wire, The fixing mechanism of the wire saw device is characterized in that it sandwiches the workpiece between a first vertical plate and a second vertical plate, and the two vertical plates and the bottom plate are in contact and fixed together.

2. The wire saw device according to claim 1, characterized in that at least one of the first vertical plate, the second vertical plate, and the bottom plate is a magnet, and the others are fixed by magnetic coupling using magnetic materials that can be fixed with magnets.

3. The wire saw device according to claim 1, wherein the first vertical plate, the second vertical plate, and the bottom plate are connected by an L-shaped bracket in which one vertical plate and the bottom plate are integrated, and the other vertical plate is a magnet, and the magnetic coupling of the magnets is such that the horizontal surface of the L-shaped bracket and the horizontal surface of the magnet plate are strongly attracted to each other, and the vertical surface of the L-shaped bracket and the vertical surface of the magnet are weakly attracted to each other.

4. The wire saw device according to claim 1, characterized in that the wire saw device is a single wire saw.

5. The wire saw device according to claim 1, characterized in that the wire saw device is a multi-wire saw.

6. The wire saw device according to any one of claims 1 to 5, characterized in that the blocking mechanism has a blocking wire that moves up and down or swings in synchronization with the vertical movement mechanism or swinging mechanism of the cutting wire, thereby blocking a part of the cut end of the workpiece.

7. A cutting method using a wire saw device, wherein the wire saw device is the wire saw device described in any one of claims 1 to 5.

8. The workpiece cutting method according to claim 7, characterized in that the blocking mechanism causes the blocking wire to move up and down or swing in synchronization with the vertical movement mechanism or swinging mechanism of the cutting wire, thereby blocking a portion of the cut end of the workpiece.

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