Wafer Generation Equipment

Abstract

To provide a wafer generation device that can suppress the replacement of a chuck table.SOLUTION: A wafer generation device 30 includes a chuck table that holds an SiC ingot on a suction surface 32 with the wafer to be generated facing up, an ultrasonic oscillation unit 34 that has an end face 341 facing the wafer to be generated and oscillates ultrasonic waves, a water supply unit 33 that supplies water between the wafer to be generated and the end face 341 of the ultrasonic oscillation unit 34, and a peeling unit 35 that sucks and holds the wafer to be generated and peels off the wafer. The chuck table 31 includes a porous plate 40 forming the suction surface 32 and a base 50 for supporting the porous plate 40. The area of the second surface of the SiC ingot is smaller than the area of the suction surface 32. The SiC ingot is sucked and held even when water is flowing on the suction surface 32 exposed around the SiC ingot.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a wafer production apparatus. [Background technology]

[0002] Various electronic device chips such as ICs (Integrated Circuits), LSIs (Large Scale Integration), LEDs (Light Emitting Diodes), and power devices are manufactured by forming fine circuits on wafers that are thinly sliced ​​from single crystal ingots of silicon, sapphire, SiC (silicon carbide), etc. with a wire saw, and then slicing them into individual chips. However, when a single crystal ingot is cut with a wire saw and the front and back sides are polished to produce wafers, 70% to 80% of the ingot's volume is wasted, which is uneconomical.

[0003] In particular, single crystal SiC ingots are highly hard and difficult to cut with a wire saw; cutting takes a considerable amount of time, resulting in poor productivity; and the unit price of the ingot is high, posing a challenge in efficiently producing wafers.

[0004] In response to these issues, a technology has been proposed (see, for example, Patent Document 1) in which a laser beam that is transparent to a single crystal SiC ingot is irradiated to the ingot at a focal point thereof, forming a separation layer on the intended cutting surface, and separating the wafers. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-102513 A Summary of the Invention [Problem to be solved by the invention]

[0006] There are various types of SiC single crystal ingots, with diameters ranging from 3 inches to 6 inches, and the delamination device shown in Patent Document 1 uses a chuck table with suction grooves on the suction surface corresponding to the size of each ingot. For this reason, the delamination device shown in Patent Document 1 required the chuck table to be replaced every time the size of the ingot was changed.

[0007] The present invention has been made in consideration of the above-mentioned circumstances, and an object of the present invention is to provide a wafer production apparatus that can reduce the need for replacement of the chuck table. [Means for solving the problem]

[0008] In order to solve the above problems and achieve the object, the wafer production apparatus of the present invention is an apparatus for producing wafers from an ingot on which a peeling layer has been formed by irradiating a laser beam having a wavelength that is transparent to the ingot with a focal point positioned at a depth corresponding to the thickness of the wafer to be produced, the apparatus comprising: a chuck table for holding the ingot with the wafer to be produced facing up on an adsorption surface; an ultrasonic oscillation unit having an end face facing the wafer to be produced and for emitting ultrasonic waves; a water supply unit for supplying water between the wafer to be produced and the end face of the ultrasonic oscillation unit; a peeling unit for holding the wafer to be produced by suction and peeling the wafer to be produced from the ingot; and a water receiving section surrounding the chuck table for receiving water that is supplied to the ingot from the water supply unit and flows down the adsorption surface of the chuck table around the ingot and is discharged, the chuck table comprising: The porous ceramics is a porous material with a volume ratio of 40% to 70% and a diameter of pores formed by the pores is 10 μm to 25 μm. A porous plate; The porous plate is placed on the upper surface. A base supporting the porous plate and having a communication passage for applying negative pressure to the porous plate, a central recess and a plurality of annular recesses, which are coaxial with each other and have a bottom at which the communication passage connected to a suction source is open, are formed on the upper surface of the base, The area of ​​the bottom surface of the ingot is smaller than the area of ​​the adsorption surface, and the ingot can be sucked and held even in a state in which the water flows on the adsorption surface exposed around the ingot.

[0009] In the wafer production apparatus, the suction surface of the porous plate has a first region corresponding to a first ingot having a first diameter and a second region surrounding the first region, and a communicating passage for selectively applying negative pressure or positive pressure is connected to regions on the surface of the porous plate opposite the suction surface, which correspond to the first region and the second region, respectively, and when the first ingot is suction-held, negative pressure may be applied through the communicating passage connected to the first region, and positive pressure may be applied through the communicating passage connected to the second region.

[0010] In the wafer production apparatus, a vacuum pump serving as a suction source may be connected to the communicating passage of the chuck table, a pressure gauge may be installed in the communicating passage, and when the vacuum pump is operated with nothing placed on the adsorption surface of the porous plate and with an ingot placed thereon, the difference in the measurement value of the pressure gauge for the porous plate may be 5 kPa or more. Effect of the Invention

[0011] The present invention has an effect of reducing the need to replace the chuck table. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a plan view of a SiC ingot to be processed by the wafer producing apparatus according to the first embodiment. [Diagram 2] FIG. 2 is a side view of the SiC ingot shown in FIG. [Diagram 3] FIG. 3 is a perspective view of a wafer produced by the wafer production apparatus according to the first embodiment. [Figure 4] FIG. 4 is a perspective view showing a state in which a peeling layer is formed on the SiC ingot shown in FIG. [Diagram 5] FIG. 5 is a side view showing a state in which a peeling layer is formed on the SiC ingot shown in FIG. [Figure 6] FIG. 6 is a perspective view illustrating a schematic configuration example of a wafer production apparatus according to the first embodiment. As shown in FIG. [Figure 7]FIG. 7 is a cross-sectional view that illustrates a schematic diagram of a production apparatus for the wafer illustrated in FIG. [Figure 8] FIG. 8 is a perspective view of a chuck table of the wafer preparation apparatus shown in FIG. [Figure 9] FIG. 9 is an exploded perspective view of the chuck table shown in FIG. [Figure 10] FIG. 10 is a cross-sectional view that typically shows the wafer producing apparatus according to the first embodiment when processing a second SiC ingot. [Figure 11] FIG. 11 is a cross-sectional view that typically shows the wafer producing apparatus according to the first embodiment when processing a first SiC ingot. [Figure 12] FIG. 12 is a cross-sectional view that typically shows how a wafer is separated from the second SiC ingot shown in FIG. [Figure 13] FIG. 13 is a cross-sectional view that illustrates a chuck table of a wafer producing apparatus according to a modified example of the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The form (embodiment) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiment. Furthermore, the components described below include those that a person skilled in the art can easily imagine and those that are substantially the same. Furthermore, the configurations described below can be appropriately combined. Furthermore, various omissions, substitutions, or modifications of the configurations can be made without departing from the gist of the present invention.

[0014] [Embodiment 1] The wafer production apparatus according to the first embodiment of the present invention will be described with reference to the drawings. First, a SiC ingot, which is an ingot to be processed by the wafer production apparatus according to the first embodiment, will be described. FIG. 1 is a plan view of the SiC ingot to be processed by the wafer production apparatus according to the first embodiment. FIG. 2 is a side view of the SiC ingot shown in FIG. 1. FIG. 3 is a perspective view of a wafer produced by the wafer production apparatus according to the first embodiment. FIG. 4 is a perspective view showing a state in which a peeling layer is formed on the SiC ingot shown in FIG. 1. FIG. 5 is a side view showing a state in which a peeling layer is formed on the SiC ingot shown in FIG. 4.

[0015] (SiC ingot) 1 and 2 is made of SiC (silicon carbide) and is formed into a cylindrical shape as a whole in the first embodiment. In the first embodiment, the SiC ingot 1 is a hexagonal single crystal SiC ingot.

[0016] 1 and 2, the SiC ingot 1 has a first surface 2 which is a circular end surface, a circular second surface 3 (corresponding to a bottom surface) on the back side of the first surface 2, and a peripheral surface 4 which is continuous with the outer edge of the first surface 2 and the outer edge of the second surface 3. The SiC ingot 1 also has a first orientation flat 5 which indicates a crystal orientation on the peripheral surface 4, and a second orientation flat 6 which is perpendicular to the first orientation flat 5. The length of the first orientation flat 5 is longer than the length of the second orientation flat 6.

[0017] The SiC ingot 1 has a c-axis 9 inclined at an off angle α in an inclination direction 8 toward the second orientation flat 6 with respect to a perpendicular line 7 of the first surface 2, and a c-plane 10 perpendicular to the c-axis 9. The c-plane 10 is inclined at an off angle α with respect to the first surface 2 of the SiC ingot 1. The inclination direction 8 of the c-axis 9 from the perpendicular line 7 is perpendicular to the extension direction of the second orientation flat 6 and is parallel to the first orientation flat 5. The c-planes 10 are set in the SiC ingot 1 at the molecular level of the SiC ingot 1. In the first embodiment, the off angle α is set to 1°, 4°, or 6°, but in the present invention, the off angle α can be freely set within a range of, for example, 1° to 6° to manufacture the SiC ingot 1.

[0018] Moreover, the first surface 2 of the SiC ingot 1 is ground by a grinding device and then polished by a polishing device, so that the first surface 2 is formed into a mirror surface.

[0019] The wafer 11 shown in FIG. 3 is manufactured by peeling off a portion of the SiC ingot 1 and performing grinding, polishing, and the like on the surface 12 peeled off from the SiC ingot 1. After the wafer 11 is peeled off from the SiC ingot 1, a device is formed on the surface. In the first embodiment, the device is a MOSFET (Metal-oxide-semiconductor Field-effect Transistor), a MEMS (Micro Electro Mechanical Systems), or an SBD (Schottky Barrier Diode), but in the present invention, the device is not limited to a MOSFET, a MEMS, or an SBD. Note that the same parts of the wafer 11 as those of the SiC ingot 1 are denoted by the same reference numerals and description thereof will be omitted.

[0020] 1 and 2, a delamination layer 13 is formed, and then the wafer 11 to be produced is delaminated from the delamination layer 13 as a starting point, as shown in Fig. 4 and Fig. 5. The delamination layer 13 is formed inside the SiC ingot 1 by irradiating the SiC ingot 1 with the pulsed laser beam 21 along the second orientation flat 6 while positioning a focal point 22 (shown in Fig. 5) of a pulsed laser beam 21 (shown in Fig. 5) having a wavelength that is transparent to the SiC ingot 1 at a depth 23 (shown in Fig. 5) corresponding to the thickness 14 (shown in Fig. 3) of the wafer 11 to be produced from the first surface 2 of the SiC ingot 1.

[0021] When the SiC ingot 1 is irradiated with a pulsed laser beam 21 having a wavelength that is transparent to the SiC ingot 1, the SiC is separated into Si (silicon) and C (carbon) by the irradiation of the pulsed laser beam 21, and the next irradiated pulsed laser beam 21 is absorbed by the previously formed C, so that the SiC is separated into Si and C in a chain reaction, forming a modified portion 24 inside the SiC ingot 1 along the second orientation flat 6, and a crack is generated extending from the modified portion 24 along the c-plane 10. Thus, when the SiC ingot 1 is irradiated with a pulsed laser beam 21 having a wavelength that is transparent to the SiC ingot 1, a peeling layer 13 including the modified portion 24 and a crack formed from the modified portion 24 along the c-plane 10 is formed.

[0022] When the SiC ingot 1 is irradiated with the laser beam 21 over the entire length in the direction parallel to the second orientation flat 6, the SiC ingot 1 and a laser beam application unit (not shown) that irradiates the laser beam 21 are index-fed relatively along the first orientation flat 5. The index-fed movement distance 25 at this time is equal to or less than the width of the crack. Again, the SiC ingot 1 is irradiated with the pulsed laser beam 21 along the second orientation flat 6 with the focal point 22 positioned at a depth 23 corresponding to the thickness 14 from the first surface 2, and a peeled layer 13 is formed inside. The SiC ingot 1 is repeatedly subjected to an operation of irradiating the laser beam 21 along the second orientation flat 6 and an operation of index-fed the laser beam application unit relatively along the first orientation flat 5.

[0023] As a result, in the SiC ingot 1, a peeled layer 13 having a lower strength than other parts including cracks and modified parts 24 where SiC is separated into Si and C is formed at a depth 23 corresponding to the thickness 14 of the wafer 11 from the first surface 2 for each movement distance of the index feed. In the SiC ingot 1, a peeled layer 13 is formed at a depth 23 corresponding to the thickness 14 from the first surface 2 over the entire length in the direction parallel to the first orientation flat 5 for each movement distance 25 of the index feed.

[0024] Also, there are a plurality of types of SiC ingots 1 having different diameters 26. In the first embodiment, the wafer production apparatus 30 produces a wafer 11 from the SiC ingot 1, which is a first SiC ingot 1-1 (corresponding to the first ingot) having a first diameter 26-1, and a second SiC ingot 1-2 (corresponding to the second ingot) having a second diameter 26-2 larger than the first diameter 26-1.

[0025] (Wafer production equipment) Next, a wafer production apparatus will be described. FIG. 6 is a perspective view showing a schematic configuration example of the wafer production apparatus according to the first embodiment. FIG. 7 is a cross-sectional view showing the wafer production apparatus shown in FIG. 6. FIG. 8 is a perspective view of a chuck table of the wafer production apparatus shown in FIG. 6. FIG. 9 is an exploded perspective view of the chuck table shown in FIG. 8. The wafer production apparatus 30 according to the first embodiment is an apparatus for producing the wafer 11 by peeling the wafer 11 shown in FIG. 4 from the SiC ingots 1-1 and 1-2 on which the peeling layer 13 is formed.

[0026] As shown in Figures 6 and 7, the wafer generating apparatus 30 includes a chuck table 31, a water supply unit 33 (shown only in Figure 6), an ultrasonic oscillation unit 34 (shown only in Figure 6), a peeling unit 35 (shown only in Figure 6), a water receiving section 36, and a control unit 100 (shown only in Figure 6).

[0027] The chuck table 31 holds the SiC ingots 1-1, 1-2 with the wafer 11 to be produced facing up. The upper surface of the chuck table 31 is an adsorption surface 32 parallel to the horizontal direction, and the second surfaces 3 of the SiC ingots 1-1, 1-2 are placed on the adsorption surface 32, and the SiC ingots 1-1, 1-2 are held by the adsorption surface 32 with the first surfaces 2 facing upward. The detailed configuration of the chuck table 31 will be described later.

[0028] The water supply unit 33 supplies water 331 (shown in FIG. 10) between the wafer 11 to be produced and an end face 341 of the ultrasonic oscillation unit 34. The water supply unit 33 is a pipe that supplies water 331 from a water supply source (not shown) from its lower end, and in the first embodiment, supplies the water 331 onto the first surfaces 2 of the SiC ingots 1-1, 1-2 held on the chuck table 31. In the first embodiment, the water supply unit 33 is provided in a housing 342 of the ultrasonic oscillation unit 34, and supplies the water 331 from the outside of the end face 341 of the ultrasonic oscillation unit 34.

[0029] The ultrasonic oscillation unit 34 is housed in a housing 342, has an end face 341 facing the wafer 11 to be produced from the SiC ingots 1-1, 1-2 held on the chuck table 31, and oscillates ultrasonic waves to apply the oscillated ultrasonic waves to the SiC ingots 1-1, 1-2. The end face 341 of the ultrasonic oscillation unit 34 faces the first surfaces 2 of the SiC ingots 1-1, 1-2 held on the chuck table 31 along a direction perpendicular to the suction surface 32 and the first surfaces 2.

[0030] The ultrasonic oscillation unit 34 includes an ultrasonic transducer and a horn having an end surface 341 facing the wafer 11 to be produced. The ultrasonic transducer is, for example, composed of a known piezoelectric element, and when power is applied from a power source (not shown), it vibrates (hereinafter referred to as ultrasonic vibration) in the orthogonal directions described above with an amplitude of several μm to several tens of μm at a frequency of 20 kHz or more and several GHz or less. The horn is formed in a columnar shape and is fixed to the end surface close to the adsorption surface 32 of the ultrasonic transducer.

[0031] In the ultrasonic oscillation unit 34, an end face 341 is immersed in water 331 (shown in FIG. 10) supplied by the water supply unit 33 onto the first faces 2 of the SiC ingots 1-1, 1-2 held on the chuck table 31, and the ultrasonic oscillator ultrasonically vibrates the end face 341, thereby ultrasonically vibrating the first faces 2 of the SiC ingots 1-1, 1-2 via the water 331, thereby applying ultrasonic waves. In the first embodiment, the water supply unit 33 and the ultrasonic oscillation unit 34 are provided so as to be freely raised and lowered by a lifting mechanism (not shown).

[0032] The peeling unit 35 suction-holds the wafer 11 to be produced from the SiC ingots 1-1, 1-2 to which ultrasonic waves have been applied, and peels the wafer 11 from the SiC ingots 1-1, 1-2. The peeling unit 35 includes a transport pad 351 that suction-holds the wafer 11 to be produced on its lower surface, and a moving unit (not shown) that is horizontally movable and raises and lowers the transport pad 351 above the chuck table 31. The moving unit moves the transport pad 351 horizontally between above the chuck table 31 and a position where it is retracted from above the chuck table 31.

[0033] The water receiving section 36 surrounds the chuck table 31 and receives water 331 that is supplied from the water supply unit 33 to the SiC ingots 1-1 and 1-2, flows over the suction surface 32 of the chuck table 31 around the SiC ingots 1-1 and 1-2, and is discharged. In the first embodiment, the water receiving section 36 is formed in a box shape with a closed bottom and an opening at the top, and the chuck table 31 is placed on the bottom to surround the chuck table 31. As shown in FIG. 7, the water receiving section 36 has an outlet 361 at the bottom for discharging the water 331 to the outside.

[0034] 7, 8 and 9, the chuck table 31 has a porous plate 40 and a base 50. The upper surface of the porous plate 40 forms the suction surface 32, and the porous plate 40 is formed in a disk shape with an outer diameter larger than the second diameter 36-2 of the second SiC ingot 1-2 and a constant thickness. For this reason, the area of ​​the second surface 3 of the SiC ingots 1-1, 1-2 is smaller than the area of ​​the suction surface 32 of the chuck table 31.

[0035] The porous plate 40 is made of porous ceramics, which is a porous material. In the first embodiment, the porous plate 40 is manufactured by, for example, mixing alumina abrasive grains of a predetermined size, frit, and a liquid adhesive, pressing the mixture into a disk shape, and then firing the mixture at 600°C to 1300°C to generate porous ceramics.

[0036] By being produced by the above-mentioned production method, the porosity of the porous ceramics forming the porous plate 40 is 40% or more and 70% or less by volume, and the diameter of the air holes formed by the pores is 10 μm or more and 25 μm or less. In the first embodiment, when a vacuum pump 56 (shown in FIG. 7) serving as a suction source connected to the chuck table 31 is operated with nothing placed on the suction surface 32, the pressure value measured by a pressure gauge 57 disposed in a junction communication passage 54-2 described later is adjusted to a predetermined range smaller than the value of the conventional configuration. In the first embodiment, the predetermined range is, for example, between −65 kPa (gauge pressure) and −20 kPa (gauge pressure).

[0037] In addition, in the first embodiment, the adsorption surface 32 of the porous plate 40 has a first region 321 (a region inside the dotted lines in Figs. 6, 8, 9, etc. of the adsorption surface 32) corresponding to the first SiC ingot 1-1, and a second region 322 (a region outside the dotted lines in Figs. 6, 8, 9, etc. of the adsorption surface 32) surrounding the first region 321. In the first embodiment, the planar shapes of the first region 321 and the second region 322 are circular and coaxial with the planar shape of the adsorption surface 32. In the first embodiment, the diameter of the first region 321 is the same as the first diameter 26-1 of the first SiC ingot 1-1.

[0038] For this reason, when the first SiC ingot 1-1 is held on the adsorption surface 32, the first SiC ingot 1-1 is placed on the first region 321. When the second SiC ingot 1-2 is held on the adsorption surface 32, the second SiC ingot 1-2 is placed on the first region 321 and the second region 322. Note that although the boundary between the first region 321 and the second region 322 is shown by a dotted line in Figures 6, 8, 9, etc., the boundary between the first region 321 and the second region 322 is not shown on the actual adsorption surface 32 of the porous plate 40.

[0039] The base 50 supports the porous plate 40 and includes a communication passage 54 for applying a negative pressure to the porous plate 40. In the first embodiment, the base 50 is made of a metal such as stainless steel, and is formed in a disk shape with a constant thickness and an outer diameter equal to the outer diameter of the porous plate 40.

[0040] The base 50 supports the porous plate 40 by placing the porous plate 40 on its upper surface 51, which is parallel to the horizontal direction. For this purpose, the surface 41 of the porous plate 40 opposite the adsorption surface 32 is placed on the upper surface 51 of the base 50. The base 50 has a central recess 52 that is circular in plan view and multiple annular recesses 53 that are ring-shaped formed on the upper surface 51.

[0041] In the first embodiment, the central recess 52 and the multiple annular recesses 53 are formed at positions coaxial with the upper surface 51 of the base 50. In the first embodiment, the diameter of the central recess 52 is smaller than the diameter of the first region 321. In the first embodiment, three annular recesses 53 are formed on the upper surface 51, but in the present invention, the number of annular recesses 53 formed on the upper surface 51 is not limited to three. In the following, the three annular recesses 53 are referred to as a first annular recess 53-1, a second annular recess 53-2, and a third annular recess 53-3, in that order from the inside.

[0042] The inner and outer diameters of the first annular recess 53-1 are larger than the diameter of the central recess 52 and smaller than the diameter of the first region 321. The inner and outer diameters of the second annular recess 53-2 are larger than the inner and outer diameters of the first annular recess 53-1 and the diameter of the first region 321. The inner and outer diameters of the third annular recess 53-3 are larger than the inner and outer diameters of the second annular recess 53-2 and the diameter of the first region 321.

[0043] One end of the communication passage 54 opens to the bottom of each of the central recess 52, the first annular recess 53-1, the second annular recess 53-2, and the third annular recess 53-3, and the other end communicates with a single communication passage, the junction communication passage 54-2. The junction communication passage 54-2 is connected to a pressure reducing pump 56. The communication passage 54 and the junction communication passage 54-2 are formed by flow paths formed in the base 50 or piping connected to the base 50, or the like.

[0044] The communication passage 54 is sucked by the decompression pump 56, thereby applying a negative pressure to the porous plate 40 placed on the base 50, and by applying a negative pressure to the porous plate 40, the porous plate 40 is sucked and held to the base 50, and the SiC ingots 1-1, 1-2 are sucked and held on the adsorption surface 32. The communication passage 54, one end of which is connected to the central recess 52 and the first annular recess 53-1, is a communication passage connected to the first region 321.

[0045] In the first embodiment, the decompression pump 56 is a water seal vacuum pump. In the first embodiment, a pressure gauge 57 is provided in the junction communication passage 54-2 to measure the air pressure in the junction communication passage 54-2. The pressure gauge 57 outputs the measurement result to the control unit 100.

[0046] In addition, one end of a positive pressure communication passage 55, which is a communication passage, is opened at the bottom of each of the central recess 52, the first annular recess 53-1, the second annular recess 53-2, and the third annular recess 53-3. The other end of the positive pressure communication passage 55 is connected to one merging positive pressure communication passage 55-2. The merging positive pressure communication passage 55-2 is connected to a positive pressure source 58. The positive pressure communication passage 55 and the merging positive pressure communication passage 55-2 are formed by a flow path formed in the base 50 or a pipe connected to the base 50. The positive pressure communication passage 55 applies positive pressure to the porous plate 40 placed on the base 50 by supplying gas pressurized by the positive pressure source 58, and by applying positive pressure to the porous plate 40, gas is sprayed from the vent hole opened on the adsorption surface 32 of the porous plate 40. The positive pressure communication passage 55, one end of which is connected to the second annular recess 53-2 and the third annular recess 53-3, is a communication passage which is connected to the second region 322.

[0047] Further, the communication passages 54 having one end opening at the bottom of each of the first annular recess 53-1, the second annular recess 53-2, and the third annular recess 53-3 are each provided with an on-off valve 59. Note that, hereinafter, the on-off valve 59 provided in the communication passage 54 having one end opening at the bottom of the first annular recess 53-1 will be referred to as a first on-off valve 59-1, the on-off valve 59 provided in the communication passage 54 having one end opening at the bottom of the second annular recess 53-2 will be referred to as a second on-off valve 59-2, and the on-off valve 59 provided in the communication passage 54 having one end opening at the bottom of the third annular recess 53-3 will be referred to as a third on-off valve 59-3.

[0048] In addition, the positive pressure communication passages 55, one end of which opens at the bottom of each of the first annular recess 53-1, the second annular recess 53-2, and the third annular recess 53-3, are each provided with an on-off valve 60. In the following, the positive pressure on-off valve 60 provided in the positive pressure communication passage 55, one end of which opens at the bottom of the first annular recess 53-1, is referred to as the first positive pressure on-off valve 60-1, the on-off valve 60 provided in the positive pressure communication passage 55, one end of which opens at the bottom of the second annular recess 53-2, is referred to as the second positive pressure on-off valve 60-2, and the on-off valve 60 provided in the positive pressure communication passage 55, one end of which opens at the bottom of the third annular recess 53-3, is referred to as the third positive pressure on-off valve 60-3.

[0049] Further, a junction on-off valve 61 which is an on-off valve is provided in the junction communication passage 54-2, and a junction positive pressure on-off valve 62 which is an on-off valve is provided in the junction positive pressure communication passage 55-2.

[0050] In this way, the communication passages 54, 55, 54-2, and 55-2 of the chuck table 31 are provided with the on-off valves 59-1, 59-2, 50-3, 60-1, 60-2, 60-3, 61, and 62, and one end opens to the bottoms of the central recess 52, the first annular recess 53-1, the second annular recess 53-2, and the third annular recess 53-3 on the upper surface 51 of the base 50, and are connected to the decompression pump 56 and the positive pressure source 58, so that negative pressure or positive pressure is selectively applied to the regions corresponding to the first region 321 and the second region 322 of the surface 41 of the porous plate 40. For this purpose, the communication passages 54, 55, 54-2, and 55-2 that selectively apply negative pressure or positive pressure are connected to the regions corresponding to the first region 321 and the second region 322 of the surface 41 of the porous plate 40. The regions corresponding to the first region 321 and the second region 322 refer to regions of the surface 41 of the porous plate 40 that overlap the first region 321 and the second region 322 in the thickness direction of the porous plate 40 .

[0051] The control unit 100 controls the above-mentioned components of the wafer generation apparatus 30 to cause the wafer generation apparatus 30 to perform processing operations on the SiC ingots 1-1 and 1-2, i.e., the wafer generation operation of the wafer generation apparatus 30. The control unit 100 is a computer having an arithmetic processing device having a microprocessor such as a CPU (central processing unit), a storage device having a memory such as a ROM (read only memory) or a RAM (random access memory), and an input / output interface device. The arithmetic processing device of the control unit 100 performs arithmetic processing according to a computer program stored in the storage device, and outputs control signals for controlling the wafer generation apparatus 30 to the above-mentioned components of the wafer generation apparatus 30 via the input / output interface device.

[0052] The control unit 100 is connected to a display unit (not shown) configured with a liquid crystal display device or the like for displaying the status and images of the machining operation, and an input unit (not shown) used by an operator to register machining content information, etc. The input unit is configured with at least one of a touch panel provided on the display unit and an external input device such as a keyboard.

[0053] Next, the processing operation of the wafer production apparatus 30 according to the first embodiment will be described with reference to the drawings. Fig. 10 is a cross-sectional view that typically shows the wafer production apparatus according to the first embodiment processing the second SiC ingot. Fig. 11 is a cross-sectional view that typically shows the wafer production apparatus according to the first embodiment processing the first SiC ingot. Fig. 12 is a cross-sectional view that typically shows the wafer being peeled off from the second SiC ingot shown in Fig. 10.

[0054] In the wafer generating apparatus 30 according to the first embodiment, the second surfaces 3 of the SiC ingots 1-1, 1-2 on which the peeling layer 13 has been formed are placed on the chucking surface 32 of the chuck table 31, the control unit 100 receives processing content information via the input unit and stores it in the storage device, and when the control unit 100 receives a processing start instruction from an operator, the processing operation is started. The processing content information includes information indicating whether the processing target is the first SiC ingot 1-1 or the second SiC ingot 1-2.

[0055] In the processing operation, the wafer generation apparatus 30 opens and closes the on-off valves 59-1, 59-2, 59-3, 60-1, 60-2, 60-3, 61, and 62 depending on whether the processing target is the first SiC ingot 1-1 or the second SiC ingot 1-2, and sucks and holds the SiC ingots 1-1 and 1-2 to be processed on the suction surface 32. When the processing target is the second SiC ingot 1-2, as shown in Fig. 10, the wafer generation apparatus 30 opens the on-off valves 59-1, 59-2, 59-3, and 61 and closes the on-off valves 60-1, 60-2, 60-3, and 62.

[0056] 11, when the processing object is the first SiC ingot 1-1, the wafer generating apparatus 30 opens the on-off valves 59-1, 60-2, 60-3, 61, and 62 and closes the on-off valves 59-2, 59-3, and 60-1. In this manner, when the wafer generating apparatus 30 suction-holds the first SiC ingot 1-1 on the suction surface 32 of the chuck table 31, it applies negative pressure through the communication passage 54 having one end opening to the central recess 52 and the first annular recess 53-1 connected to the first region 321, and applies positive pressure through the positive pressure communication passage 55 having one end opening to the second annular recess 53-2 and the third annular recess 53-3 connected to the second region 322.

[0057] 10 and 11, when the SiC ingots 1-1 and 1-2 are sucked and held on the chucking surface 32 of the chuck table 31, the pressure value measured by the pressure gauge 57 falls within a second predetermined range in which both the lower limit and the upper limit are lower than the above-mentioned predetermined range. In the first embodiment, the second predetermined range is, for example, between -90 kPa (gauge pressure) and -70 kPa (gauge pressure).

[0058] In the processing operation, the wafer generating apparatus 30 lowers the water supply unit 33 and the ultrasonic oscillation unit 34 to approach the first surfaces 2 of the SiC ingots 1-1, 1-2 held on the chuck table 31, and supplies water 331 from the water supply unit 33 to the first surfaces 2 of the SiC ingots 1-1, 1-2 held on the chuck table 31, so that the end face 341 of the ultrasonic oscillation unit 34 is immersed in the water 331 on the first surfaces 2 of the held SiC ingots 1-1, 1-2. The pressure value measured by the pressure gauge 57 at this time falls within the second predetermined range. In this way, since the chuck table 31 has a porous plate 40 made of porous ceramics having a porosity of 40% or more and 70% or less by volume and the diameter of the air holes formed by the pores is 10 μm or more and 25 μm or less, when the pressure reducing pump 56 is operated with nothing placed on the suction surface 32 and with SiC ingots 1-1, 1-2 placed on it, the difference in the measurement value of the pressure gauge 57 is the difference between the predetermined range and the second predetermined range, i.e., 5 kPa or more.

[0059] In addition, during the processing operation, water 331 supplied to first surfaces 2 of SiC ingots 1-1, 1-2 by water supply unit 33 flows over first surfaces 2 and downward along peripheral surfaces 4 of SiC ingots 1-1, 1-2. Water 331 flows over suction surfaces 32 exposed around the SiC ingots 1-1, 1-2, along the outer peripheral surface of chuck table 31, is received by water receiver 36, and is then discharged from discharge port 361. In this way, the chuck table 31 is configured such that the porous plate 40 is made of porous ceramics having a porosity of 40% or more and 70% or less by volume and the diameter of the air holes formed by the pores is 10 μm or more and 25 μm or less, so that the area of ​​the second surface 3 of the SiC ingots 1-1, 1-2 is smaller than the area of ​​the suction surface 32 and water 331 flows over the suction surface 32 exposed around the SiC ingots 1-1, 1-2.

[0060] If the porosity of the porous ceramics forming the porous plate 40 is less than 40% by volume and the diameter of the pores formed by the pores is less than 10 μm, even if leakage of negative pressure can be suppressed, the SiC ingots 1-1, 1-2 whose second surfaces 3 have an area smaller than that of the adsorption surface 32 cannot be sucked and held by the adsorption surface 32 with sufficient suction force. If the porosity of the porous ceramics forming the porous plate 40 exceeds 70% by volume and the diameter of the pores formed by the pores exceeds 25 μm, leakage of negative pressure is too great and the SiC ingots 1-1, 1-2 whose second surfaces 3 have an area smaller than that of the adsorption surface 32 cannot be sucked and held by the adsorption surface 32 with sufficient suction force.

[0061] Wafer production apparatus 30 applies power to the ultrasonic vibrator of ultrasonic oscillation unit 34 for a predetermined time, and ultrasonic oscillation unit 34 applies ultrasonic waves to first surface 2 of SiC ingots 1-1, 1-2. Then, ultrasonic waves from ultrasonic oscillation unit 81 are irradiated to first surface 2, stimulating delamination layer 13, and fracturing SiC ingots 1-1, 1-2 over the entire surface of wafer 11 to be produced, starting from delamination layer 13.

[0062] After applying power to the ultrasonic vibrator of the ultrasonic oscillation unit 34 for a predetermined time, the wafer generation apparatus 30 stops the supply of water 331 from the water supply unit 33, opens the on-off valves 59-1, 59-2, 59-3, and 61, closes the on-off valves 60-1, 60-2, 60-3, and 62, and raises the water supply unit 33 and the ultrasonic oscillation unit 34. The wafer generation apparatus 30 moves the separation unit 35 to above the chuck table 31 and lowers it above the chuck table 31 to bring the lower surface of the transfer pad 351 of the separation unit 35 into contact with the first surfaces 2 of the SiC ingots 1-1 and 1-2 held on the chuck table 31.

[0063] The wafer generating apparatus 30 suction-holds the first surfaces 2 of the SiC ingots 1-1, 1-2 held on the chuck table 31 on the lower surface of the transport pad 351 of the peeling unit 35, and lifts the peeling unit 35 as shown in Fig. 12. The wafer generating apparatus 30 peels the wafer 11 to be generated on the first surface 2 side from the SiC ingots 1-1, 1-2, and carries out the SiC ingots 1-1, 1-2 from the suction surface 32 of the chuck table 31. After the SiC ingots 1-1 and 1-2 are removed from the suction surface 32 of the chuck table 31, the wafer generating apparatus 30 closes the on-off valves 59-1, 59-2, 59-3 and 61 and opens the on-off valves 60-1, 60-2, 60-3 and 62 to supply pressurized gas from the positive pressure source 58 to the porous plate 40, i.e., to apply positive pressure, and sprays the gas from the pores opened on the suction surface 32.

[0064] In addition, in the wafer generating apparatus 30, the control unit 100 prestores a predetermined range and a second predetermined range, and after the SiC ingots 1-1 and 1-2 are suction-held on the suction surface 32 of the chuck table 31, the control unit 100 judges whether the SiC ingots 1-1 and 1-2 defined in the processing content information are suction-held on the suction surface 32 of the chuck table 31 based on the measurement result of the pressure gauge 57. Specifically, when the processing target defined in the processing content information is the first SiC ingot 1-1, if the measurement result of the pressure gauge 57 is within the second predetermined range after the SiC ingots 1-1 and 1-2 are suction-held on the suction surface 32 of the chuck table 31, the control unit 100 judges that the first SiC ingot 1-1 is suction-held on the suction surface 32, and if the measurement result of the pressure gauge 57 is outside the second predetermined range, the control unit 100 judges that the first SiC ingot 1-1 is not suction-held on the suction surface 32. Similarly, when the processing object defined by the processing content information is the second SiC ingot 1-2, the control unit 100 makes a determination after suction-holding the SiC ingots 1-1 and 1-2 on the suction surface 32 of the chuck table 31.

[0065] As described above, in the wafer production apparatus 30 according to the first embodiment, the porosity of the porous ceramics forming the porous plate 40 is 40% or more and 70% or less by volume, and the diameter of the air holes formed by the pores is 10 μm or more and 25 μm or less. Therefore, the wafer production apparatus 30 according to the first embodiment can suction and hold the SiC ingots 1-1, 1-2 having the second surface 3 smaller than the area of ​​the suction surface 32 on the suction surface 32 of the chuck table 31 even in a situation where water 331 flows on the suction surface 32.

[0066] Therefore, the wafer production apparatus 30 according to the first embodiment is provided with the chuck table 31 that can suction and hold the SiC ingots 1-1, 1-2 regardless of the area of ​​the second surface 3 of the SiC ingots 1-1, 1-2 even in a situation where water 331 flows on the suction surface 32, and has the effect of eliminating the need to replace the chuck table 31 depending on the size of the SiC ingots 1-1, 1-2. As a result, the wafer production apparatus 30 according to the first embodiment has the effect of suppressing replacement of the chuck table 31 even if the diameters 26-1, 26-2, which are the sizes of the SiC ingots 1-1, 1-2 to be processed, are changed.

[0067] In addition, in the wafer production apparatus 30 according to the first embodiment, the difference in pressure value measured when the vacuum pump 56 applies negative pressure to the chucking surface 32 is 5 kPa or more between the state where there is nothing on the chuck table 31 and the state where the SiC ingots 1-1, 1-2 are placed on the chuck table 31, which is different from the state where there is nothing on the chuck table 31 and the state where the SiC ingots 1-1, 1-2 are placed on the chucking surface 32. As a result, in the wafer production apparatus 30, the control unit 100 can confirm whether the SiC ingots 1-1, 1-2 are placed on the chucking surface 32 based on the measurement result of the pressure gauge 57.

[0068] Furthermore, the wafer production apparatus 30 according to the first embodiment can apply positive pressure from the suction surface 32 exposed around the first SiC ingot 1-1, thereby preventing debris generated during peeling from being sucked into the exposed suction surface 32. As a result, the wafer production apparatus 30 can suppress contamination of the suction surface 32.

[0069] [Modifications] A wafer production apparatus according to a modified example of the first embodiment of the present invention will be described with reference to the drawings. Fig. 13 is a cross-sectional view that shows a schematic diagram of a chuck table of the wafer production apparatus according to a modified example of the first embodiment. In Fig. 13, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

[0070] The chuck table 31-1 of the wafer generating apparatus 30 according to the modified example shown in Fig. 13 is the same as that of the first embodiment except that the porous plate 40 and the base 50 are fixed by the bolts 70 as shown in Fig. 13. Note that Fig. 13 omits the recesses 52, 53-1, 53-2, and 53-3, the communication passages 54, 54-2, 55, and 55-2, and the opening / closing valves of the base 50, but in the present invention, the chuck table 31 includes the recesses 52, 53-1, 53-2, and 53-3 and the communication passage 54, similar to the first embodiment.

[0071] The wafer production apparatus 30 according to the modified example includes a chuck table 31-1 that can suction and hold the SiC ingots 1-1, 1-2 regardless of the area of ​​the second surface 3 of the SiC ingots 1-1, 1-2 even in a situation where water 331 flows on the suction surface 32. As a result, similar to the first embodiment, the wafer production apparatus 30 according to the modified example has an effect of being able to suppress replacement of the chuck table 31-1 even if the diameters 26-1, 26-2, which are the sizes of the SiC ingots 1-1, 1-2 to be processed, are changed.

[0072] In addition, after the processing object is placed on the suction surface 32, the wafer generation apparatus 30 of the present invention may open the on-off valves 59-1, 59-2, 59-3, and 61 and close the on-off valves 60-1, 60-2, 60-3, and 62, and the control unit 100 may control the opening and closing of the on-off valves 59-1, 59-2, 59-3, 60-1, 60-2, 60-3, 61, and 62 based on the measurement results of the pressure gauge 57. Specifically, after the object to be processed is placed on the suction surface 32, the wafer generating apparatus 30 of the present invention opens the on-off valves 59-1, 59-2, 59-3, and 61 and closes the on-off valves 60-1, 60-2, 60-3, and 62, and if the control unit 100 determines that the measurement result of the pressure gauge 57 is within a second predetermined range, it opens the on-off valves 59-1, 59-2, 59-3, and 61 and keeps the on-off valves 60-1, 60-2, 60-3, and 62 closed to continue the processing operation.

[0073] After the object to be processed is placed on the suction surface 32, the wafer generating apparatus 30 of the present invention opens the on-off valves 59-1, 59-2, 59-3, and 61, and closes the on-off valves 60-1, 60-2, 60-3, and 62, and if the measurement result of the pressure gauge 57 is outside the second predetermined range, the control unit 100 closes the third on-off valve 59-3, opens the third positive pressure on-off valve 60-3 and the confluence positive pressure on-off valve 62, and again determines whether the measurement result of the pressure gauge 57 is within the second predetermined range.

[0074] In this way, after the object to be processed is placed on the suction surface 32, the wafer generating apparatus 30 of the present invention opens the on-off valves 59-1, 59-2, 59-3, and 61, and closes the on-off valves 60-1, 60-2, 60-3, and 62, so that the control unit 100 sequentially closes the on-off valves 59-1, 59-2, and 59-3, starting with those provided in the connecting passages 54 whose one ends open into the outer peripheral annular recesses 53-1, 53-2, and 53-3, and opens the confluence positive pressure on-off valve 62, and sequentially opens the positive pressure on-off valves 60-1, 60-2, and 60-3, starting with those provided in the positive pressure connecting passages 55 whose one ends open into the outer peripheral annular recesses 53-1, 53-2, and 53-3.

[0075] In this case, in addition to the effect of the first embodiment, the wafer generating apparatus 30 opens the on-off valves 59-1, 59-2, 59-3, 61 and closes the on-off valves 60-1, 60-2, 60-3, 62 after the processing object is placed on the suction surface 32, and the control unit 100 controls the opening and closing of the on-off valves 59-1, 59-2, 59-3, 60-1, 60-2, 60-3, 61, 62 so that the measurement result of the pressure gauge 57 falls within a second predetermined range, so that the SiC ingots 1-1, 1-2 of any size can be appropriately sucked and held on the suction surface 32 of the porous plate 40 of the chuck table 31. As a result, the wafer generating apparatus 30 has the effect of further suppressing the replacement of the chuck table 31 even if the diameters 26-1, 26-2, which are the sizes of the SiC ingots 1-1, 1-2 to be processed, are changed.

[0076] It should be noted that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. [Explanation of symbols]

[0077] 1. SiC ingot (ingot) 1-1 First SiC ingot (First ingot) 1-2 Second SiC ingot (Second ingot) 3 2nd side (bottom side) 11 Wafer 13 Peeling layer 14 Thickness 21 Laser Beam 22 Focus point 23 Depth 26-1 First diameter 30 Wafer generation equipment 31 Chuck table 32 Adsorption surface 33 Water Supply Unit 34 Ultrasonic oscillation unit 35 Peeling unit 36 Water receiving section 40 Porous Plate 41 surface (opposite the suction surface) 50 Bases 54 Communication path 54-2 Merging connection path (communication path) 55 Positive pressure passage 55-2 Confluence positive pressure passage (passage) 56 Decompression pump (suction source) 57 Pressure Gauge 321 First area 322 Second area 331 Water 341 End face

Claims

1. A wafer producing apparatus for producing a wafer from an ingot having a peeled layer formed thereon by irradiating a laser beam having a wavelength that is transparent to the ingot with a focal point positioned at a depth corresponding to a thickness of the wafer to be produced, the apparatus comprising: a chuck table for holding the ingot with a suction surface thereof with the wafer to be produced facing up; an ultrasonic wave generating unit having an end surface facing a wafer to be produced and configured to generate ultrasonic waves; a water supply unit for supplying water between the wafer to be produced and the end face of the ultrasonic oscillation unit; a separation unit that suction-holds a wafer to be produced and separates the wafer from the ingot; a water receiving portion surrounding the chuck table for receiving water supplied from the water supply unit to the ingot and flowing over the suction surface of the chuck table around the ingot and then being discharged; the chuck table includes a porous plate made of porous ceramics, which is a porous material having a porosity of 40% or more and 70% or less by volume and having air holes formed by pores with a diameter of 10 μm or more and 25 μm or less, and a base on which the porous plate is placed, supports the porous plate, and includes a communication passage for applying a negative pressure to the porous plate; A central recess and a plurality of annular recesses which are coaxial with each other and have a bottom opening connected to a suction source are formed on the upper surface of the base, and the area of ​​the bottom surface of the ingot is smaller than the area of ​​the adsorption surface, so that the ingot is adsorbed and held even when water flows on the adsorption surface exposed around the ingot.

2. The adsorption surface of the porous plate has a first region corresponding to a first ingot having a first diameter and a second region surrounding the first region; The communication passage that selectively applies negative pressure or positive pressure is connected to regions corresponding to the first region and the second region on the surface of the porous plate opposite to the adsorption surface, 2. The wafer production apparatus according to claim 1, wherein when the first ingot is suction-held, negative pressure is applied in the communicating passage connected to the first region, and positive pressure is applied in the communicating passage connected to the second region.

3. 3. The wafer generating apparatus of claim 1 or claim 2, wherein a vacuum pump serving as a suction source is connected to the communicating passage of the chuck table, a pressure gauge is installed in the communicating passage, and when the vacuum pump is operated with nothing placed on the adsorption surface of the porous plate and with an ingot placed thereon, the difference in the measurement value of the pressure gauge for the porous plate is 5 kPa or more.

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