Cutting device and method for manufacturing semiconductor wafers using the same

Abstract

A cutting device capable of increasing the processing rate when cutting a workpiece, and a method for manufacturing semiconductor wafers using the same are provided. [Solution] A cutting processing device for cutting a workpiece, comprising: a nozzle for supplying an electrolyte solution toward the workpiece; a first electrode for applying a first potential to the electrolyte solution; a second electrode for applying a second potential to the workpiece that is higher than the first potential; a power supply device for supplying power between the first electrode and the second electrode; and a wire saw that slides in contact with the workpiece to cut the workpiece.

Description

[Technical Field]

[0001] The present disclosure relates to a cutting apparatus for cutting a workpiece into linear shapes, and a method for manufacturing semiconductor wafers using the same. [Background technology]

[0002] For example, when manufacturing wafers from an ingot (lump of raw material) made of a crystalline material such as a semiconductor material, the ingot is generally cut into large blocks using a band saw or similar device, then the outer periphery is ground using a cylindrical grinder or similar device, and then multiple wafers are cut out from the cylindrical block after the outer periphery has been ground using a wire saw.

[0003] When processing wafers from such crystalline materials, and cutting multiple wafers from a cylindrical block (ingot), a multi-wire saw device is generally used, which stretches multiple wires in parallel and moves these wires back and forth repeatedly in unit runs, cutting the ingot into linear shapes with the wires sliding against the ingot, thereby cutting out the wafers (see, for example, Patent Document 1).

[0004] Patent Document 2 also discloses a method for processing a silicon substrate, in which a wire such as a platinum wire is connected to the cathode and a silicon ingot to be processed is connected to the anode, and the silicon ingot is anodized by being brought into approximate contact with the wire in an electrolytic solution.The silicon oxide formed by the anodization is then dissolved with hydrofluoric acid mixed in the electrolytic solution, thereby enabling the silicon ingot to be sliced.

[0005] Furthermore, Patent Document 3 discloses a wire electric discharge machining device that applies a voltage between a wire and a crystalline ingot to generate a local discharge between the wire and the crystalline ingot, thereby locally melting and cutting the crystalline ingot. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-013390 [Patent Document 2] International Publication No. 2008 / 140058 [Patent Document 3] Patent No. 7282277 Summary of the Invention [Problem to be solved by the invention]

[0007] The multi-wire saw device disclosed in Patent Document 1 had the problem of low cutting rate and poor processability when the constituent material of the ingot to be cut was a high-hardness material such as silicon carbide (SiC) crystal or gallium nitride (GaN) crystal. The inventors discovered that, in particular, with the trend toward larger wafer diameters, when the diameter was increased to 6 inches or more, the increase in processing time became apparent. Furthermore, the processing method disclosed in Patent Document 2 does not provide the wire with a mechanical cutting function, but rather chemically dissolves the oxide-generating portion with hydrofluoric acid. This poses the problem of high costs for corrosion prevention measures for the equipment due to the use of a highly corrosive electrolyte, as well as the cost of waste liquid disposal of the electrolyte after use.

[0008] Furthermore, the wire electric discharge machining device disclosed in Patent Document 3 has the problem that the wire is subject to significant wear due to the application of voltage to the wire, and that the surface structure of the crystalline ingot, for example, the crystal structure, is easily changed because the crystalline ingot is locally melted by electric discharge.

[0009] This disclosure has been made in consideration of the above-mentioned circumstances, and aims to provide a cutting processing device that can increase the processing rate when cutting a workpiece, and a method for manufacturing semiconductor wafers using the same. [Means for solving the problem]

[0010] One embodiment of the cutting processing device is a cutting processing device that cuts a workpiece, and is configured to include a nozzle that supplies an electrolyte toward the workpiece, a first electrode that applies a first potential to the electrolyte, a second electrode that applies a second potential to the workpiece that is higher than the first potential, a power supply device that supplies power between the first electrode and the second electrode, and a wire saw that slides in contact with the workpiece to cut the workpiece. [Effects of the Invention]

[0011] According to the embodiment, it is possible to provide a cutting apparatus capable of increasing the processing rate when cutting a workpiece, and a method for manufacturing a semiconductor wafer using the same. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic configuration diagram showing a cutting device according to a first embodiment. [Figure 2] FIG. 10 is a schematic configuration diagram showing a cutting device according to a second embodiment. [Figure 3] FIG. 10 is a schematic configuration diagram showing a cutting device according to a third embodiment. [Figure 4] FIG. 10 is a schematic configuration diagram showing a cutting device according to a fourth embodiment. [Figure 5] FIG. 10 is a schematic configuration diagram showing a cutting device according to a fifth embodiment. [Figure 6] 1 is a graph showing the results of an example. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, a cutting apparatus according to one embodiment and a method for manufacturing semiconductor wafers using the same will be described with reference to the drawings. Note that the following embodiment is specifically described to provide a better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified. Furthermore, the drawings used in the following description may show essential parts enlarged for the sake of convenience in order to make the features of the present invention easier to understand, and the dimensional proportions of each component may not necessarily be the same as those in reality.

[0014] [First embodiment] FIG. 1 is a schematic configuration diagram showing a cutting apparatus according to a first embodiment of the present disclosure. The cutting processing device 10 is a multi-wire saw device in which a single long wire saw 15 is shifted in parallel and stretched between multiple rollers, and cuts out multiple wafers simultaneously by linearly cutting the ingot M, which is the workpiece, with the wire saw 15 along a direction perpendicular to the longitudinal direction of the ingot M.

[0015] The cutting device 10 of this embodiment includes an electrolyte supply means 11, a first electrode 12, a second electrode 13, a power supply device 14, a wire saw 15, a wire saw driving device 16, and a control unit 17.

[0016] The electrolytic solution supplying means 11 includes an electrolytic solution discharge part (nozzle) 21, a filter 22, a pump 23, and a sink 24. The electrolytic solution supplying means 11 is an electrolytic solution circulating supply device that sucks the electrolytic solution Q used in processing, which is collected in the sink 24, by the pump 23 through the filter 22 and discharges it toward the electrolytic solution discharge part 21.

[0017] The electrolytic solution discharge unit (nozzle) 21 discharges the electrolytic solution Q toward the ingot M, which is the workpiece. The electrolytic solution discharge unit 21 is an open-ended pipe having a discharge port as shown in Fig. 1. The electrolytic solution discharge unit 21 may be provided with a shower head, mist head, or spray nozzle at the discharge port to diffuse the electrolytic solution Q over the entire processed portion of the ingot M.

[0018] In this embodiment, the electrolyte solution discharge part 21 constituting the electrolyte solution supply means 11 is made of a conductor, for example, a metal, and functions as the first electrode 12. In this embodiment, the electrolyte solution discharge part 21 is made of, for example, an aluminum alloy. One end of a cathode wire 14a extending from a power supply device 14 (described later) is connected to the electrolyte solution discharge part (first electrode) 21. This applies a first potential, for example, a cathode potential, to the electrolyte discharged from the electrolyte solution discharge part 21. Therefore, in this embodiment, the electrolyte solution discharge part 21 also serves as the first electrode 12, and is therefore desirably made of a conductive, preferably corrosion-resistant, metallic material, such as stainless steel or copper.

[0019] The filter 22 may be made of a nonwoven fabric filter or the like that collects processing waste and the like contained in the electrolyte Q used in processing and collected in the sink 24.

[0020] The pump 23 may be any type of pump, such as a non-positive displacement pump such as a propeller pump or a centrifugal pump, or a positive displacement pump such as a plunger pump or a screw pump.

[0021] The sink 24 has a base 19 (described later) disposed therein, and collects the electrolyte Q used in machining and discharges it toward the pump 23.

[0022] The second electrode 13 is composed of a pedestal 19 on which the ingot M is placed. The pedestal 19 has a recess that holds the cylindrical ingot M without rolling it. In this embodiment, the pedestal 19 is made of a conductor, such as graphite or a metal.

[0023] One end of an anode wire 14b extending from a power supply 14 (described later) is connected to the base (second electrode) 19. This allows a second potential, for example, an anode potential, to be applied to the ingot M placed on the base 19. During processing, it is preferable to form an adhesive layer made of a conductive adhesive between the ingot M and the base 19.

[0024] As another embodiment of the second electrode 13 different from this embodiment, as shown by the branched dotted anode wiring 14b in Fig. 1, an electrode pad made of copper or aluminum may be attached to the outer peripheral surface of the ingot M as the second electrode 13. Even in this embodiment, a second potential, for example, an anode potential, can be applied to the ingot M. In this embodiment, since the base 19 does not need to function as the second electrode 13, an insulating material, a dielectric material, or the like can also be used as the material for the base 19.

[0025] A vertical movement device 28 is provided below the pedestal 19 to move the pedestal 19 up and down in the vertical direction. The vertical movement device 28 moves the ingot M fixed to the pedestal 19 up and down in the vertical direction. During processing, the vertical movement device 28 moves the ingot M from bottom to top toward the wire saw 15 at a predetermined moving speed, and the ingot M comes into contact with the wire saw 15 moving horizontally, cutting the ingot M in a direction perpendicular to the longitudinal direction of the ingot M.

[0026] A DC power supply such as a DC stabilized power supply can be used as the power supply 14. The cathode output terminal of the power supply 14 is electrically connected to the electrolyte discharge portion (first electrode) 21 via a cathode wiring 14a. The anode output terminal is electrically connected to the base (second electrode) 19 via an anode wiring 14b.

[0027] The wire saw 15 may be constructed, for example, by carrying diamond chips or the like as abrasive grains on the surface of a wire made of high carbon steel or the like by electroplating or the like (fixed abrasive grain method). The cutting processing device 10 of this embodiment is a multi-wire saw device, in which one wire saw 15 is offset in parallel and stretched between multiple rollers. The wire diameter of the wire saw 15 may be, for example, about 50 to 200 μm.

[0028] The wire saw driving device 16 drives the wire saw 15 and includes a pair of driving rollers 26a, 26b, a guide roller 26c, a start bobbin 29a, an end bobbin 29b, and a motor 27 that rotates the driving rollers 26a, 26b.

[0029] A groove for guiding the wire saw 15 is formed on the circumferential surface of each of the drive rollers 26a and 26b, and a plurality of wire saws 15 are stretched parallel to one another between the drive roller 26a and the drive roller 26b.

[0030] Motor 27 is connected to drive roller 26a or drive roller 26b, and by rotating drive rollers 26a and 26b at a predetermined rotational speed, saw wire 15 is unwound from start bobbin 29a and stretched between drive rollers 26a and 26b, moves in one direction, and is wound up on end bobbin 29b. Typically, saw wire 15 moves gradually in one direction while repeating a reciprocating motion with an amplitude larger than the width of the cut surface of ingot M.

[0031] The control unit 17 is composed of, for example, a control board equipped with a CPU, a memory, etc., and an interface. The control unit 17 controls, for example, the voltage value applied to the cathode output terminal and the anode output terminal of the power supply device 14 , and also controls the operation of the vertical movement device 28 and the pump 23 of the electrolyte supply means 11 .

[0032] The electrolyte Q used in such a cutting device 10 can be a liquid that is conductive and does not change in quality when a voltage is applied, such as an aqueous solution of an alkali metal salt, a lubricating oil that has been made conductive by mixing carbon powder or metal particles, or an emulsion of these aqueous solutions and lubricating oil. In this embodiment, an aqueous sodium chloride solution (salt water) is used as the electrolyte Q. The concentration of the sodium chloride solution may be, for example, about 1 wt% to 5 wt%.

[0033] In this embodiment, the wire saw 15 described above uses a wire with abrasive grains carried on its surface, but the wire saw 15 can also be configured with only a steel wire without abrasive grains carried thereon. In this case, abrasive grains, such as diamond chips, are mixed into the electrolyte Q. This allows the electrolyte containing abrasive grains to act on the wire, and the wire and loose abrasive grains function as the wire saw 15 (loose abrasive grain method).

[0034] The ingot M, which is the workpiece to be cut by the cutting apparatus 10, may be any material having a predetermined conductivity (10,000 Ωcm or less, preferably 10 Ωcm or less) sufficient to allow current to flow for anodization, and in which the oxide formed by anodization is more embrittled than the original material before anodization. Specific examples of such materials include SiC, GaN, Si, AlN, diamond, BN, ZnO, and Ga2O3. Typical examples include semiconductor materials composed of a single crystal or polycrystal of any one of SiC, GaN, Si, and Ga2O3. By cutting an ingot M made of such a material using the cutting apparatus 10 of this embodiment, semiconductor wafers such as SiC wafers, GaN wafers, and silicon wafers can be formed.

[0035] The operation of the cutting apparatus 10 of this embodiment configured as described above and the method for manufacturing semiconductor wafers will now be described. In the following description, it is assumed that the cutting apparatus 10 of this embodiment is used to cut out SiC from an SiC single crystal ingot as the ingot M, for example. First, the ingot M, which is the workpiece, is fixed in the recess of the base 19, which also serves as the second electrode 13. The ingot M may be fixed using, for example, a conductive adhesive.

[0036] Next, the control unit 17 operates the pump 23 of the electrolyte solution supply means 11 to start circulating the supply of the electrolyte solution Q. The electrolyte solution Q is discharged by the pump 23 from the electrolyte solution discharge unit 21 toward the ingot M, and flows so as to cover the outer surface of the ingot M. The electrolyte solution Q is then collected by a sink 24 disposed below the ingot M, filtered by a filter 22, and then discharged again from the electrolyte solution discharge unit 21.

[0037] Next, the control unit 17 operates the power supply device 14 to apply a first potential to the electrolyte solution discharge unit (first electrode) 21, which also serves as the first electrode 12, via the cathode wiring 14a. As a result, the electrolyte solution Q discharged from the electrolyte solution discharge unit 21 flows on the outer peripheral surface of the ingot M while the first potential is being applied.

[0038] Furthermore, the power supply device 14 is operated to apply a second potential to the pedestal (second electrode) 19, which also serves as the second electrode 13, via the anode wiring 14b. As a result, the second potential is applied to the ingot M placed on the pedestal 19.

[0039] The first potential applied to the electrolyte Q is typically ground potential (0 V), but may be any potential lower than the second potential. The second potential applied to the ingot M may be any potential higher than the first potential.

[0040] The potential difference between the first potential and the second potential applied by the power supply device 14 may be in the range of about 0.1 V to 100 V, and the current value may be in the range of 0.01 A to 50 A. The power supply device 14 may be operated in a constant voltage mode, for example.

[0041] In this way, by applying the first potential and the second potential to the electrolytic solution Q and the ingot M, respectively, by the power supply device 14, the surface of the ingot M through which the electrolytic solution Q flows is anodized (anodization step).

[0042] That is, when the electrolyte Q at the first potential comes into contact with the ingot M at the second potential, O contained in the electrolyte Q 2- OH -These react with the SiC that makes up the ingot M and are oxidized, forming an oxide film such as SiO2 on the surface of the ingot M. Depending on the oxidation conditions, the SiO2 film formed here may become porous with many pores.

[0043] Next, the control unit 17 operates the wire saw driving device 16 to move the wire saw 15 stretched between a pair of drive rollers 26a, 26b. While not particularly limited, the movement speed of the wire saw 15 may be, for example, approximately 300 m / min to 2500 m / min. To further improve the processing speed, a movement speed greater than 2500 m / min may be adopted. Then, the vertical movement device 28 raises the base 19 on which the ingot M is fixed at a predetermined speed (processing rate). When the wire saw 15 comes into contact with the raised ingot M and begins to slide, the ingot M is ground into a linear shape by the abrasive grains carried by the wire saw 15 (grinding process).

[0044] In this grinding process, a high processing rate can be set because an oxide film such as SiO2 is formed on the surface of the ingot (workpiece) M by anodizing. That is, the Vickers hardness of SiC is about 23.5 GPa, while that of SiO2 is about 9.7 GPa, so the hardness of the SiO2 film formed by anodizing is significantly lower than that of SiC. In addition, the oxide film formed during anodizing is porous, which is thought to make it embrittled and increase the grinding processing rate.

[0045] Therefore, by constantly applying the first potential and the second potential to the electrolyte Q and the ingot M, respectively, during grinding processing using the wire saw 15, an SiO2 film with a lower hardness than SiC is always formed on the grinding portion (the exposed surface of the ingot M), making it possible to perform grinding at a higher processing rate than when grinding SiC.

[0046] Then, by using the vertical movement device 28 to move the multiple wire saws 15 and raise the pedestal 19 to which the ingot M is fixed across the diameter of the ingot M, multiple SiC wafers can be formed (cutting process). That is, the cutting process is a process in which the surface of the ingot M is anodized in the anodization process, while linear grinding is performed across the entire diameter of the ingot M in the grinding process. The SiC wafers obtained in this way are expected to be less susceptible to damage during the cutting process due to the assistance of anodization, which is expected to improve the warpage and thickness variations of the wafers obtained during the cutting process, as well as improve the straightness of the wafers when cut.

[0047] As described above, according to the cutting apparatus 10 of this embodiment and the method for manufacturing semiconductor wafers using the same, the power supply 14 applies the first potential and the second potential to the electrolyte Q and the ingot M, respectively, during cutting by the wire saw 15. As a result, the cut surface of the ingot M is always covered with an oxide film, which is an oxide of the constituent material of the ingot, by anodization.

[0048] Therefore, if the oxide has a lower hardness than the constituent material of the ingot, the cutting surface will not become rough even if the rising speed of the ingot M, i.e., the processing rate, is increased. Therefore, it is possible to realize a cutting processing apparatus 10 that can increase the processing rate during cutting and maintain high surface processing accuracy, and a semiconductor wafer manufacturing method using the same.

[0049] In addition, even when GaN is used as the ingot M, a Ga2O3 film with a lower hardness than GaN is formed by anodization. Therefore, even if the processing rate is increased, the cut surface is less likely to become rough, and a relatively flat GaN wafer can be formed.

[0050] [Second embodiment] FIG. 2 is a schematic configuration diagram showing a cutting device according to a second embodiment of the present disclosure. The same components as those in the first embodiment are given the same numbers, and redundant explanations will be omitted. In the cutting device 30 of this embodiment, a mesh electrode 32 made of a conductor is used as the first electrode 12 instead of the electrolyte solution discharge part (nozzle) 21. The mesh electrode 32 may be made of, for example, a steel mesh material. The mesh electrode 32 is disposed between the electrolyte solution discharge part (nozzle) 21 and the ingot (workpiece) M, and a first potential is applied to the electrolyte solution Q discharged from the electrolyte solution discharge part 21 as it passes through the mesh electrode 32.

[0051] According to the configuration of this embodiment, by using the mesh electrode 32 as the first electrode, the contact area of ​​the first electrode with the electrolytic solution Q is increased, and the efficiency of applying the first potential to the electrolytic solution Q can be improved. This allows the surface of the ingot M to be anodized more efficiently. In the second embodiment, a mesh electrode is exemplified as the first electrode, but a plate-shaped electrode (conductive plate) may also be used.

[0052] [Third embodiment] FIG. 3 is a schematic configuration diagram showing a cutting apparatus according to a third embodiment of the present disclosure. The same components as those in the first embodiment are given the same numbers, and redundant explanations will be omitted. In the cutting device 40 of this embodiment, a funnel-shaped electrode 42 made of a conductor is used as the first electrode 12 instead of the electrolyte solution discharge part (nozzle) 21. The funnel-shaped electrode 42 may be made of, for example, copper or aluminum. The funnel-shaped electrode 42 is integrally formed with a sink part 42a that receives the electrolyte solution Q discharged from the electrolyte solution discharge part 21 and a plurality of nozzle parts 42b that extend downward from the sink part 42a.

[0053] The funnel-shaped electrode 42 is disposed between the electrolyte solution discharge portion (nozzle) 21 and the ingot (workpiece) M, and the electrolyte solution Q discharged from the electrolyte solution discharge portion 21 is received by the funnel-shaped electrode 42, thereby applying a first electric potential to the electrolyte solution Q. Then, the electrolyte solution Q to which the first electric potential has been applied flows evenly downward from the multiple nozzle portions 42b toward the ingot M. This allows the electrolyte solution Q to flow evenly over the surface of the ingot M, making it possible to more efficiently anodize the surface of the ingot M.

[0054] In this third embodiment, the electrolyte solution discharge portion (nozzle) 21 and the funnel-shaped electrode 42 are illustrated as separate bodies, but a configuration in which the funnel-shaped electrode 42 is attached to the electrolyte solution discharge portion (nozzle) 21 and integrated with it may also be used.

[0055] [Fourth embodiment] FIG. 4 is a schematic configuration diagram showing a cutting apparatus according to a fourth embodiment of the present disclosure. The same components as those in the first embodiment are given the same numbers, and redundant explanations will be omitted. In the cutting device 50 of this embodiment, a liquid tank 52 made of a conductor that accommodates an ingot (workpiece) M is used as the first electrode 12, instead of the electrolyte solution discharge unit (nozzle) 21. The potential of this liquid tank 52 is set to be substantially the same as the potential of the cathode wire 14a. Furthermore, the anode wire 14b connected to the base (second electrode) 19 may be covered with an insulating coating at least within the liquid tank 52. The anode wire 14b is insulated from the liquid tank 52, and may be led to the base 19 from the upper opening of the liquid tank 52 by an insulating-coated wiring, for example.

[0056] Such a liquid tank 52 may be, for example, a hollow rectangular parallelepiped container made of a carbon material and having an open top. A pedestal (second electrode) 19, which also serves as the second electrode 13, is accommodated inside the liquid tank 52, and an ingot M is placed on the pedestal 19. The bottom of the pedestal 19 and the bottom of the liquid tank 52 are electrically insulated by an insulating material (not shown). An electrolyte solution Q discharged from an electrolyte solution discharge portion 21 is stored inside the liquid tank 52, and the ingot M is submerged in the electrolyte solution Q. In FIG. 4, a sink 24 is provided below the liquid tank 52, similar to that in FIG. 1, to prevent leakage of the electrolyte when the liquid tank 52 is cut, but this is omitted from FIG. 4.

[0057] In this cutting apparatus 50, a first potential is applied to the electrolyte Q via the liquid tank 52 made of a conductor, and a second potential is applied to the ingot M via the base 19. As a result, an oxide film is formed on the surface of the ingot M by anodic oxidation. During cutting, the wire saw 15 cuts the liquid tank 52 as well as the ingot M. In other words, the liquid tank 52, which forms the first electrode, is a disposable container. For this reason, it is preferable to use a material that is conductive, has low hardness, and does not easily wear down the wire saw 15, such as carbon in this embodiment, as the material constituting the liquid tank 52. However, the liquid tank 52 may also be made of a material with low conductivity, such as glass.

[0058] According to the cutting processing apparatus 50 of this embodiment, by submerging the entire ingot M in the electrolyte Q to which the first potential is applied, the entire surface of the ingot M is covered with the electrolyte Q, and therefore, the anodization of the surface of the ingot M can be carried out evenly and efficiently.

[0059] [Fifth embodiment] FIG. 5 is a schematic configuration diagram showing a cutting apparatus according to a fifth embodiment of the present disclosure. The same components as those in the first embodiment are given the same numbers, and redundant explanations will be omitted. The cutting device 60 of this embodiment includes an ingot moving device 68 that moves the base 19, which also serves as the second electrode 13 and supports the ingot (workpiece) M downward, up and down in the vertical direction.

[0060] According to this embodiment, when cutting the ingot M having an oxide film formed on its surface by anodization, the ingot M is cut from below (down cut), so that the wafers being cut can be supported from below during cutting. This allows the wafers to be collected in an aligned state after cutting is complete, and the ingot M can be sliced ​​more efficiently.

[0061] Although the embodiments of the present disclosure have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are included in the scope of the inventions described in the claims and their equivalents. [Example]

[0062] An ingot made of a SiC single crystal was actually cut using a device simulating the cutting device of the second embodiment shown in Figure 2. The electrolyte used was a sodium chloride aqueous solution (concentration 5 wt%) with loose abrasive grains (diamond abrasive grains: concentration 5 wt%, average particle size 5 μm) dispersed in it. An iron (steel) conducting plate was used as the first electrode (cathode). The conducting plate was tilted and placed directly below the open end of the electrolyte outlet, so that the electrolyte that slid down from the edge of the conducting plate would be guided to the ingot to be processed.

[0063] The second electrode (anode) was a steel base, to which the SiC ingot was bonded using a conductive adhesive. By applying a DC voltage of 10 V or 30 V between the current-carrying plate (first electrode) and the base (second electrode) while flowing the above-mentioned electrolyte containing abrasive grains, it was confirmed that an oxide film (SiO2) was formed on the surface of the SiC ingot by anodic oxidation.

[0064] While maintaining this voltage application state, cutting was performed for 30 minutes using a wire saw (wire diameter 120 μm, wire feed rate 3.1 m / min, wire tension 10 N, cutting pressure 15 N). This wire feed rate is extremely slow compared to common commercially available cutting devices, but was set due to the limitations of the experimental equipment used. As a comparative example, no voltage was applied between the current-carrying plate (first electrode) and the base (second electrode), and no oxide film (SiO2) was formed. Cutting was performed for 30 minutes using the wire saw under the above conditions. The wire used for the wire saw had a resin coating on its surface. The results of this verification example are shown in Figure 6.

[0065] According to the results shown in Figure 6, under conditions where no anodization was performed (voltage applied between electrodes: 0 V), the cutting depth was approximately 110-120 μm, but under conditions where an oxide film was formed by anodization (voltage applied between electrodes: 10 V, 30 V), the cutting depth reached 180-190 μm, confirming an improvement in machining efficiency of approximately 1.5 times compared to when no anodization was performed. In this example, measurements were performed at two levels of voltage applied between electrodes: 10 V and 30 V, and improvements in machining efficiency were observed regardless of the magnitude of the applied voltage, confirming the effect of forming an oxide film by anodization.

[0066] As another verification example, we also verified the case where a first potential was applied to the wire of a wire saw instead of the conductive plate used in the cutting device of the above verification example. In this verification example, a diamond wire with diamond grains supported on the wire was used. When a voltage was applied between the electrodes, a discharge phenomenon was observed between the wire saw and the SiC ingot when the wire saw contacted the SiC ingot. Furthermore, when the applied voltage between the electrodes was changed to 0 V, 10 V, and 30 V, the cutting depth per unit time decreased. In other words, applying a voltage did not improve the processing efficiency. It was confirmed that, when performing cutting processing by forming an oxide film stably, it is preferable to apply the first potential to the electrolyte rather than to the wire of the wire saw.

[0067] The key points that can be understood from the above disclosure are as follows: [Configuration 1] A cutting device for cutting a workpiece, a nozzle for supplying an electrolytic solution toward the workpiece; a first electrode that applies a first potential to the electrolyte; a second electrode that applies a second potential higher than the first potential to the workpiece; a power supply device that supplies power between the first electrode and the second electrode; a wire saw that slides in contact with the workpiece to cut the workpiece. [Configuration 2] 2. The cutting device according to claim 1, wherein the nozzle is made of a conductive material and serves as the first electrode. [Configuration 3] The cutting apparatus according to configuration 2, wherein the first electrode is a mesh electrode made of a conductor and disposed between the nozzle and the workpiece, through which the electrolyte flowing down toward the workpiece can pass. [Configuration 4] The cutting apparatus according to configuration 2, wherein the first electrode is a funnel-shaped electrode made of a conductive material, disposed between the nozzle and the workpiece, and capable of receiving the electrolyte flowing down toward the workpiece and controlling the flow direction. [Configuration 5] The cutting device according to configuration 2, wherein the first electrode is a liquid tank made of a conductor that accommodates the workpiece, the electrolyte is stored in the liquid tank, and the first potential is applied via the liquid tank. [Configuration 6] 6. The cutting device according to any one of configurations 1 to 5, wherein the wire saw carries abrasive grains. [Configuration 7] 6. The cutting apparatus according to any one of configurations 1 to 5, wherein the electrolyte contains abrasive grains. [Configuration 8] The cutting processing device according to any one of configurations 1 to 7, further comprising a workpiece moving device that moves the workpiece vertically from the upper side to the lower side toward the wire saw that slides at a fixed position in the vertical direction. [Configuration 9] 9. The cutting device according to any one of configurations 1 to 8, wherein the workpiece is an ingot made of a single crystal or polycrystal of any one of SiC, GaN, Si, and Ga2O3. [Configuration 10] A cutting processing device according to any one of configurations 1 to 9, wherein the surface of the workpiece is anodized by a potential difference between the first potential and the second potential, and the anodized portion is linearly ground with the wire saw. [Configuration 11] A method for manufacturing a semiconductor wafer using the cutting apparatus according to any one of configurations 1 to 10, an anodizing step of anodizing a surface of the ingot of semiconductor material, which is the workpiece, to form an oxide film; a grinding step of linearly grinding the portion where the oxide film is formed with the wire saw; and a cutting step of cutting the workpiece by the anodizing step and the grinding step to obtain semiconductor wafers. [Industrial Applicability]

[0068] The cutting apparatus and semiconductor wafer manufacturing method using the same disclosed herein can efficiently slice an ingot made of a hard crystalline material to form semiconductor wafers, thereby improving the efficiency of semiconductor wafer manufacturing and thus having industrial applicability. [Explanation of symbols]

[0069] 10, 30, 40, 50, 60…Cutting equipment 11...Electrolyte supply means 12...1st electrode 13…Second electrode 14...Power supply device 15...Wire saw 16...Wire saw drive unit 17...Control unit 21...Electrolyte discharge part (nozzle) 22...Filter 23...Pump 24...Sink 28...Up and down movement device 32...Mesh electrode 42...Funnel-shaped electrode 52…Liquid tank 68...Ingot moving device Q…Electrolyte M...Ingot (workpiece)

Claims

1. A cutting device for cutting a workpiece, a nozzle for supplying an electrolytic solution toward the workpiece; a first electrode that applies a first potential to the electrolyte; a second electrode that applies a second potential higher than the first potential to the workpiece; a power supply device that supplies power between the first electrode and the second electrode; a wire saw that slides in contact with the workpiece to cut the workpiece.

2. The cutting device according to claim 1 , wherein the nozzle is made of a conductive material and serves also as the first electrode.

3. 3. The cutting device according to claim 2, wherein the first electrode is a mesh electrode made of a conductor and disposed between the nozzle and the workpiece, and through which the electrolyte flowing down toward the workpiece can pass.

4. 3. The cutting device according to claim 2, wherein the first electrode is a funnel-shaped electrode made of a conductive material, disposed between the nozzle and the workpiece, and capable of receiving the electrolyte flowing down toward the workpiece and controlling the flow direction.

5. 3. The cutting device according to claim 2, wherein the first electrode is a liquid tank made of a conductive material that contains the workpiece, the electrolyte is stored in the liquid tank, and the first potential is applied via the liquid tank.

6. The cutting device according to claim 1 , wherein the wire saw carries abrasive grains.

7. The cutting device according to claim 1 , wherein the electrolytic solution contains abrasive grains.

8. A cutting processing device as described in any one of claims 1 to 5, further comprising a workpiece moving device that moves the workpiece from the upper side to the lower side in the vertical direction toward the wire saw that slides at a fixed position in the vertical direction.

9. The workpiece is SiC, GaN, Si, Ga. ２ O ３ 6. The cutting device according to claim 1, wherein the ingot is made of one of a single crystal and a polycrystal.

10. 6. The cutting device according to claim 1, wherein the surface of the workpiece is anodized by a potential difference between the first potential and the second potential, and the anodized portion is linearly ground with the wire saw.

11. A method for manufacturing a semiconductor wafer using the cutting processing apparatus according to any one of claims 1 to 5, an anodizing step of anodizing a surface of the ingot of semiconductor material, which is the workpiece, to form an oxide film; a grinding step of linearly grinding the portion where the oxide film is formed with the wire saw; and a cutting step of cutting the workpiece by the anodizing step and the grinding step to obtain semiconductor wafers.

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