Stripping device

Abstract

[Problem] To provide a stripping apparatus that can suppress the enlargement of the apparatus size and efficiently strip a wafer from a crystal ingot with a stripping layer formed thereon. [Solution] The stripping apparatus includes: a crystal ingot holding unit that holds a SiC crystal ingot with the wafer to be manufactured facing upwards; an ultrasonic oscillation unit that is configured to face the SiC crystal ingot held in the crystal ingot holding unit and oscillates with ultrasound; and a liquid supply unit that supplies liquid between the wafer to be manufactured and the ultrasonic oscillation unit. The ultrasonic oscillation unit includes: an ultrasonic oscillator; and a housing member having a bottom surface that is formed to have an area equal to or greater than the area to which ultrasound is to be applied.

Description

[Technical Field]

[0001] This invention relates to a stripping device. [Previous Technology]

[0002] Wafers containing components are generally manufactured by thinning cylindrical semiconductor ingots with a wire saw and then grinding the front and back sides of the wafer after cutting.

[0003] However, if the wafer is manufactured in the above manner, most of the semiconductor ingot (70% to 80% of its volume) will be lost due to removal, which is economically unfeasible.

[0004] In particular, SiC ingots, which have attracted attention as power devices in recent years, are difficult to cut with a wire saw due to their high hardness, resulting in time-consuming cutting and poor productivity.

[0005] Therefore, the inventors have proposed the following techniques: a technique for focusing a laser beam with a wavelength that is penetrable to a single-crystal SiC crystal rod at the interior of the SiC crystal rod and irradiating it with focused light, thereby forming a release layer on a predetermined cutting surface; and a technique for applying ultrasound to a SiC crystal rod with a release layer already formed, thereby separating / manufacturing a wafer using the release layer as a starting point (for example, see Patent Document 1 and Patent Document 2). [Preferred Art Documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2016-111143 [Patent Document 2] Japanese Patent Application Publication No. 2019-102513 [Summary of the Invention]

[0007] [Problem to be Solved by the Invention] In order to impart ultrasonic waves to a SiC crystal rod, an ultrasonic imparting means is needed that has an end face with an area equal to or greater than the area to be irradiated with ultrasonic waves. Therefore, currently, an end face with the desired area is formed by attaching an oscillating plate to an ultrasonic oscillator.

[0008] However, it is known that the adhesive connecting the ultrasonic oscillator and the oscillator plate will peel off over a long period of use, resulting in changes in properties, thus causing problems in the efficient manufacturing of wafers.

[0009] Therefore, the object of the present invention is to provide a stripping device that can suppress characteristic variations and efficiently manufacture wafers from semiconductor ingots.

[0010] [Technical Means for Solving the Problem] According to the present invention, a stripping apparatus is provided for stripping a wafer to be manufactured from a semiconductor ingot with a stripping layer already formed thereon. The stripping layer is formed by positioning a focal point of a laser beam with a wavelength that is penetrable to the semiconductor ingot at a depth equivalent to the thickness of the wafer to be manufactured and irradiating the laser beam. The stripping apparatus includes: an ingot holding unit that holds the semiconductor ingot with the wafer to be manufactured facing upwards; an ultrasonic oscillation unit that is configured to face the semiconductor ingot held in the ingot holding unit and oscillates ultrasonic waves; and a liquid supply unit that supplies liquid between the wafer to be manufactured and the ultrasonic oscillation unit. The ultrasonic oscillation unit includes: an ultrasonic oscillator; and a housing member having a bottom surface that is formed to have an area equal to or greater than the area to which ultrasonic waves are to be imparted. The housing member is integrally formed with the end face of the ultrasonic oscillator.

[0011] Preferably, the housing component comprises any one of stainless steel, titanium, and aluminum.

[0012] [Effect of the Invention] According to the present invention, it can suppress characteristic variations and efficiently manufacture wafers from semiconductor ingots.

Implementation Method

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the contents described in the following embodiments. Furthermore, the constituent elements described below include those readily conceived by those skilled in the art and substantially the same. Moreover, the configurations described below can be appropriately combined. Furthermore, various omissions, substitutions, or modifications to the configuration can be made without departing from the spirit of the present invention.

[0015] [First Embodiment] A stripping apparatus according to a first embodiment of the present invention will be described with reference to the figures. First, the crystal rod to be processed by the stripping apparatus of the first embodiment, namely a SiC crystal rod, will be described. FIG1 is a top view of the SiC crystal rod to be processed by the stripping apparatus of the first embodiment. FIG2 is a side view of the SiC crystal rod shown in FIG1. ​​FIG3 is a perspective view of a wafer manufactured by the stripping apparatus of the first embodiment. FIG4 is a top view showing the state in which a stripping layer has been formed on the SiC crystal rod shown in FIG1. ​​FIG5 is a cross-sectional view along line VV in FIG4. FIG6 is a perspective view showing the state in which a stripping layer has been formed on the SiC crystal rod shown in FIG1. ​​FIG7 is a side view showing the state in which a stripping layer has been formed on the SiC crystal rod shown in FIG6.

[0016] (SiC Crystal Rod) The SiC crystal rod 1 shown in Figures 1 and 2 in the first embodiment is composed of SiC (silicon carbide) and is formed into a cylindrical shape. In the first embodiment, the SiC crystal rod 1 is a hexagonal single-crystal SiC crystal rod.

[0017] As shown in Figures 1 and 2, the SiC crystal rod 1 has: a first face 2, which is a circular end face; a circular second face 3, which is the back side of the first face 2; and a peripheral face 4, which is connected to the outer edge of the first face 2 and the outer edge of the second face 3. Furthermore, the SiC crystal rod 1 has: a first orientation plane 5, which shows the crystal orientation on the peripheral face 4; and a second orientation plane 6, which is orthogonal to the first orientation plane 5. The length of the first orientation plane 5 is longer than the length of the second orientation plane 6.

[0018] Furthermore, the SiC crystal rod 1 has a c-axis 9 and a c-plane 10 orthogonal to the c-axis 9. The c-axis 9 is tilted at an angle α relative to the perpendicular line 7 of the first surface 2 in an inclination direction 8 toward the second orientation plane 6. The c-plane 10 is tilted at an angle α relative to the first surface 2 of the SiC crystal rod 1. The inclination direction 8 from the perpendicular line 7 of the c-axis 9 is orthogonal to the extension direction of the second orientation plane 6 and parallel to the first orientation plane 5. A plurality of c-planes 10 are set in the SiC crystal rod 1 at the molecular level. In the first embodiment, the tilt angle α is set to 1°, 4° or 6°, but in the present invention, the tilt angle α can be freely set in the range of, for example, 1° to 6° to manufacture the SiC crystal rod 1.

[0019] Furthermore, after the first surface 2 of the SiC crystal rod 1 is ground by a grinding device, the first surface 2 is ground by a polishing device to form a mirror surface. A portion of the first surface 2 of the SiC crystal rod 1 is peeled off, and the peeled portion is manufactured into a wafer 20 as shown in FIG3.

[0020] The wafer 20 shown in Figure 3 is manufactured by peeling off a portion of the SiC ingot 1 and performing grinding and polishing processes on the surface 21 peeled off from the SiC ingot 1. After being peeled off from the SiC ingot 1, the wafer 20 forms a device on its front side. In the first embodiment, the device is a MOSFET (Metal-oxide-semiconductor Field-effect Transistor), MEMS (Micro Electro Mechanical Systems), or SBD (Schottky Barrier Diode), but in this invention, the device is not limited to MOSFET, MEMS, and SBD. Furthermore, the same symbols are used to mark the parts of the wafer 20 that are the same as those of the SiC ingot 1, and the description is omitted.

[0021] The SiC ingot 1 shown in Figures 1 and 2 is separated and peeled off from the release layer 23 shown in Figures 4 and 5, which is a portion of the wafer 20 to be manufactured, starting from the release layer 23. The second side 3 of the SiC ingot 1 is attracted and held by the holding stage 31 of the laser processing apparatus 30 (shown in Figures 6 and 7), and the release layer 23 is formed by the laser processing apparatus 30. The laser processing apparatus 30 positions the focusing point 33 of the pulsed laser beam 32 (shown in Figure 7) with a wavelength that has penetrability to the SiC ingot 1 at a depth 35 (shown in Figures 5 and 7) corresponding to the thickness 22 (shown in Figure 3) of the wafer 20 to be manufactured, starting from the first side 2 of the SiC ingot 1, and irradiates the pulsed laser beam 32 along the second orientation plane 6 to form the release layer 23 inside the SiC ingot 1.

[0022] When the SiC crystal rod 1 is irradiated with a pulsed laser beam 32 of a wavelength that has penetrating power to the SiC crystal rod 1, as shown in FIG5, a modified portion 24 is formed inside the SiC crystal rod 1 along the X-axis direction, and a crack 25 extending from the modified portion 24 along the c-plane 10 is created. The modified portion 24 is formed by the irradiation of the pulsed laser beam 32, which causes SiC to separate into Si (silicon) and C (carbon). The pulsed laser beam 32 that is subsequently irradiated is absorbed by the previously formed C, and SiC is linked to separate into Si and C. Thus, when the SiC crystal rod 1 is irradiated with a pulsed laser beam 32 of a wavelength that has penetrating power to the SiC crystal rod 1, a peeling layer 23 containing the modified portion 24 and the crack 25 is formed from the modified portion 24 along the c-plane 10.

[0023] If the laser processing apparatus 30 irradiates the entire length of the direction parallel to the second orientation plane 6 of the SiC crystal rod 1 when forming the release layer 23, the SiC crystal rod 1 and the laser beam irradiation unit 36 ​​irradiating the laser beam 32 are indexed and fed relative to each other along the first orientation plane 5.

[0024] The laser processing apparatus 30 again positions the focusing point 33 at the desired depth from the first surface 2, and irradiates the SiC crystal rod 1 with a pulsed laser beam 32 along the second orientation plane 6, thereby forming a release layer 23 inside the SiC crystal rod 1. The laser processing apparatus 30 repeats the following actions: irradiating the laser beam 32 along the second orientation plane 6; and indexing the laser beam irradiation unit relative to each other along the first orientation plane 5.

[0025] Accordingly, the SiC ingot 1 forms a release layer 23 with reduced strength compared to other parts at a depth 35 corresponding to the thickness 22 of the wafer 20, starting from the first surface 2, according to the moving distance 26 of each indexing feed. The release layer 23 includes modified parts 24 of SiC separated into Si and C and cracks 25. The SiC ingot 1 forms the release layer 23 at a depth 35 corresponding to the thickness 22 of the wafer 20, starting from the first surface 2, across the entire length in a direction parallel to the first orientation plane 5, according to the moving distance of each indexing feed.

[0026] (Stripping Device) Next, the stripping device will be described. FIG8 is a side view showing an example of the configuration of the stripping device of the first embodiment. FIG9 is a side cross-sectional view of the ultrasonic oscillation unit of the stripping device shown in FIG8. The stripping device 40 of the first embodiment is a stripping device for stripping the wafer 20 to be manufactured from the SiC crystal rod 1 with the stripping layer 23 formed shown in FIG4 and FIG5.

[0027] The stripping device 40 is an apparatus for stripping the wafer 20 to be manufactured from the SiC crystal rod 1 whose focal point 33 of the laser beam 32 with a wavelength that is penetrable to the SiC crystal rod 1 is positioned at a depth 35 corresponding to the thickness 22 of the wafer 20 to be manufactured and irradiated by the laser beam 32 to form a stripping layer 23. As shown in FIG8, the stripping device 40 includes: a crystal rod holding unit 41, a liquid supply unit 50, an ultrasonic oscillation unit 60, and a control unit 100.

[0028] The ingot holding unit 41 holds the SiC ingot 1 with the wafer 20 to be manufactured facing upwards. The ingot holding unit 41 is formed in the shape of a thick disk. The upper surface of the ingot holding unit 41 is a holding surface 42 parallel to the horizontal direction, and the second surface 3 of the SiC ingot 1 is placed on the holding surface 42, with the first surface 2 facing upwards to hold the SiC ingot 1. In the first embodiment, the ingot holding unit 41 attracts and holds (i.e., vacuum-fixes) the second surface 3 of the SiC ingot 1 to the holding surface 42. Furthermore, the ingot holding unit 41 rotates about an axis by a rotation drive source 43 while the SiC ingot 1 is held on the holding surface 42.

[0029] The liquid supply unit 50 supplies liquid 51 (shown in FIG. 8) between the wafer 20 to be manufactured and the ultrasonic oscillation unit 60. The liquid supply unit 50 supplies liquid 51 from a liquid supply source through a conduit at its lower end, and in the first embodiment, supplies liquid 51 to the first surface 2 of the SiC ingot 1 held in the ingot holding unit 41. Furthermore, in the first embodiment, the liquid supply unit 50 is configured to be freely raised and lowered by a lifting mechanism (not shown).

[0030] The ultrasonic oscillation unit 60 is configured to face the SiC crystal rod 1 held in the crystal rod holding unit 41 and oscillate ultrasonically. As shown in FIG9, the ultrasonic oscillation unit 60 includes a housing member 61 and an ultrasonic oscillator 70.

[0031] The housing member 61 includes: a box-shaped housing body 62 with an opening at the top and a flat cover 63. The housing body 62 is made of metal and integrally includes: a circular plate-shaped bottom portion 65 having a bottom surface 64 facing the first surface 2 of the SiC crystal rod 1 held in the crystal rod holding unit 41; and a cylindrical portion 66 erected from the outer edge of the bottom portion 65. Furthermore, in this invention, the housing member 61 may also use, for example, six ultrasonic oscillators 70, and the bottom portion 65 may be configured as an elliptical shape. In this invention, if the bottom part 65 of the housing member 61 is configured as a square or rectangle, the distance from the ultrasonic oscillator 70 to the housing member 61 will vary depending on the position, which may affect the peelability. Therefore, in order to make the distance from the ultrasonic oscillator 70 to the bottom part 65 of the housing member 61 as equal as possible, it is preferable to configure the bottom part 65 as a circular plate or an elliptical shape.

[0032] The bottom surface 64 of the bottom part 65 of the housing body 62 is formed to have an area that is the same as or greater than the area of ​​the first surface 2 of the SiC crystal rod 1 to which the ultrasonic oscillation unit 60 is to impart ultrasonic waves. That is, the housing member 61 has a bottom surface 64, which has an area that is the same as or greater than the area of ​​the first surface 2 of the SiC crystal rod 1 to which the ultrasonic oscillation unit 60 is to impart ultrasonic waves.

[0033] In this invention, the term "having an area equal to or greater than the area of ​​the first surface 2 of the SiC crystal rod 1 to which ultrasound is to be imparted" means that the area of ​​the bottom surface 64 of the housing body 62 is 50% or more and 150% or less of the area of ​​the first surface 2 of the SiC crystal rod 1 to which ultrasound is to be imparted, which is held in the crystal rod holding unit 41.

[0034] If the area of ​​the bottom surface 64 is less than 50% of the area of ​​the first surface 2, although the wafer 20 to be manufactured can be peeled from the SiC ingot 1 by oscillating the ultrasonic oscillation unit 60 in the X-axis direction, the time required to peel the wafer 20 from the SiC ingot 1 will be longer. Furthermore, if the area of ​​the bottom surface 64 is greater than 150% of the area of ​​the first surface 2, the peeling device 40 will be too large and undesirable, and the liquid supply unit 50 will find it difficult to supply liquid between the wafer 20 to be manufactured on the SiC ingot 1 and the bottom surface 64 of the ultrasonic oscillation unit 60. In the first embodiment, the area of ​​the bottom surface 64 is 80% of the area of ​​the first surface 2.

[0035] The cover 63 is formed as a circular plate with an outer diameter equal to that of the bottom surface 64. The outer edge of the cover 63 is fixed to the outer edge of the cylindrical portion 66 and closes the opening of the shell body 62.

[0036] The ultrasonic oscillator 70 is an ultrasonic oscillator. In the first embodiment, the ultrasonic oscillation unit 60 includes a plurality of ultrasonic oscillators 70. The plurality of ultrasonic oscillators 70 are housed within the housing member 61, arranged at intervals between each other, and fixed to the bottom part 65 of the housing body 62.

[0037] The ultrasonic oscillator 70 includes: an annular piezoelectric element 71, a cylindrical first metal block 72, a second metal block 73, and a fixing bolt 75.

[0038] In the first embodiment, the ultrasonic oscillator 70 includes two piezoelectric elements 71. The two piezoelectric elements 71 overlap each other in the axial direction. The piezoelectric elements 71 are made of lead zirconate titanate, which expands and contracts in the thickness direction when an alternating current is applied.

[0039] The first metal block 72 is made of metal and overlaps with a piezoelectric element 71. The second metal block 73 is made of metal and overlaps with another piezoelectric element 71. The second metal block 73 is formed into a truncated cone shape, which increases in size as it moves away from the other piezoelectric element 71. The second metal block 73 has a screw hole 732 for screwing into a bolt 75 at the end face 731 where it overlaps with the other piezoelectric element 71.

[0040] Bolt 75 passes through the inner side of the first metal block 72, a piezoelectric element 71 and another piezoelectric element 71, and engages with the screw hole 732 of the second metal block 73. If bolt 75 engages with screw hole 732, the first metal block 72, a piezoelectric element 71, another piezoelectric element 71 and the second metal block 73 are fixed together.

[0041] Furthermore, in the first embodiment, the first metal block 72, a piezoelectric element 71, another piezoelectric element 71, and the second metal block 73, which are fixed by bolts 75, are arranged in a position coaxial with each other. Also, in the first embodiment, the ultrasonic oscillator 70 has electrodes 74 for applying alternating current to the piezoelectric elements 71, located between the piezoelectric elements 71 and between the other piezoelectric element 71 and the second metal block 73. The electrodes 74 are electrically connected to an AC power source (not shown) that supplies the alternating current. When alternating current is applied to the electrodes and the piezoelectric elements 71 extend or retract, the ultrasonic oscillation unit 60 as a whole, particularly the bottom surface 64, oscillates at a frequency of 20 kHz or higher and 200 kHz or lower with an amplitude of several μm to tens of μm (so-called ultrasonic oscillation).

[0042] Furthermore, in the first embodiment, the metals constituting the housing member 61 and the metal blocks 72 and 73 in the ultrasonic oscillation unit 60 are made of the same material. When the ultrasonic oscillation unit 60 performs ultrasonic oscillation by extending and retracting the piezoelectric element 71, materials with low specific gravity are more prone to vibration. Therefore, the housing member 61 and the metal blocks 72 and 73 are made of the same material.

[0043] In the first embodiment, the metal constituting the shell member 61 and the metal blocks 72 and 73 is stainless steel, titanium alloy, or aluminum alloy. That is, the shell member 61 and the metal blocks 72 and 73 include any one of stainless steel, titanium, and aluminum. Furthermore, when the metal constituting the shell member 61 and the metal blocks 72 and 73 is aluminum alloy, in order to suppress damage caused by cavitation, it is preferable to use extra-super duralumin (which is specified as A7075 according to Japanese industrial standards).

[0044] Furthermore, in this invention, the metals constituting the housing member 61, metal blocks 72, and 73 exhibit less characteristic variation due to load as their weight increases, making it easier to track and control the resonant frequency caused by the AC power supply. Therefore, stainless steel with a specific gravity greater than aluminum alloys such as super-duralumin is preferred. In addition, the ultrasonic oscillation unit 60 in this invention weighs 1.4 kg when using an aluminum alloy, while stainless steel with the same shape weighs 1.8 kg.

[0045] Furthermore, in the first embodiment, the bottom surface 65 of the housing member 61 is integrally formed with the end face 733 (shown as dashed lines in FIG. 9) of the second metal block 73 of each ultrasonic oscillator 70 on the side away from the piezoelectric element 71. That is, in the first embodiment, the bottom surface 65 of the housing member 61 of the ultrasonic oscillation unit 60 and the second metal block 73 are integrally formed. The bottom surface 65 of the integral housing member 61 and the second metal block 73 are manufactured by machining the metal block.

[0046] Furthermore, in the first embodiment, the ultrasonic oscillation unit 60 is moved along the holding surface 42 of the crystal rod holding unit 41 by means of the moving unit 67, and rises and falls in a direction that is intersecting (or orthogonal in the first embodiment) with respect to the holding surface 42.

[0047] The control unit 100 controls the aforementioned components of the stripping device 40 and causes the stripping device 40 to perform processing operations on the SiC ingot 1. Furthermore, the control unit 100 is a computer having the following devices: an arithmetic processing unit having a microprocessor such as a CPU (central processing unit); a memory device having a memory such as ROM (read-only memory) or RAM (random access memory); and an input / output interface device. The arithmetic processing unit of the control unit 100 performs arithmetic processing according to a computer program stored in the memory device, and outputs control signals for controlling the stripping device 40 to the aforementioned components of the stripping device 40 through the input / output interface device.

[0048] The control unit 100 is connected to a display unit (not shown) and an input unit (not shown). The display unit (not shown) is configured as a liquid crystal display device or the like that that displays the status or images of the processing operation. The input unit (not shown) is used by the operator to log in processing content information. The input unit is configured as at least one of an external input device such as a touch panel or a keyboard provided on the display unit.

[0049] The first embodiment of the stripping device 40 places the second surface 3 of the SiC crystal rod 1 on the holding surface 42 of the crystal rod holding unit 41, on which the stripping layer 23 has been formed. The control unit 100 receives processing content information through the input unit and stores it in the memory device. If the control unit 100 receives a processing start instruction from the operator, the processing operation is started.

[0050] During the processing, because the liquid supply unit 50 and the ultrasonic oscillation unit 60 are integrated, the stripping device 40 descends and approaches the first surface 2 of the SiC crystal rod 1 held in the crystal rod holding unit 41. The stripping device 40 supplies liquid 51 from the liquid supply unit 50 to the first surface 2 of the SiC crystal rod 1 held in the crystal rod holding unit 41, and immerses the bottom surface 64 of the housing member 61 in the liquid 51 on the first surface 2 of the SiC crystal rod 1.

[0051] The stripping device 40 rotates the ingot holding unit 41 around its axis and moves the ultrasonic oscillation unit 60 back and forth along the holding surface 42 using a rotary drive source 43, while applying an alternating current for a predetermined time to the piezoelectric elements 71 of each ultrasonic oscillator 70 of the ultrasonic oscillation unit 60 to cause ultrasonic oscillation on the bottom surface 64. The stripping device 40 transmits the ultrasonic oscillation of the bottom surface 64 to the first surface 2 of the SiC ingot 1 through the liquid 51, thus imparting ultrasonic waves to the first surface 2 of the ingot holding unit 41. In this way, the ultrasonic waves from the ultrasonic oscillation unit 60 stimulate the stripping layer 23, and the SiC ingot 1 is divided from the stripping layer 23, and the wafer 20 to be manufactured is separated from the SiC ingot 1. When an alternating current for a predetermined time is applied to the piezoelectric elements 71 of each ultrasonic oscillator 70 of the ultrasonic oscillation unit 60, the stripping device 40 ends the processing operation. Furthermore, in this invention, if it is detected that the wafer 20 has been peeled off from the SiC crystal rod 1, the peeling device 40 can also terminate the processing operation.

[0052] The wafer 20 to be manufactured, which has been separated from the SiC crystal rod 1, is adsorbed by an adsorption mechanism (not shown) and peeled off from the SiC crystal rod 1, and the surface 21 that has been peeled off from the SiC crystal rod 1 is subjected to grinding, polishing and other processes.

[0053] As explained above, the peeling device 40 of the first embodiment includes an ultrasonic oscillation unit 60, which is formed by integrating the second metal block 73 of the ultrasonic oscillator 70 with the bottom part 65 of the housing member 61 that functions as an oscillation plate. Therefore, the adhesive or other materials fixing the ultrasonic oscillator 70 to the bottom part 65 will not peel off, and the variation of the characteristics (frequency, amplitude) of the ultrasonic oscillator 70 can be suppressed. As a result, the peeling device 40 of the first embodiment can suppress the variation of the characteristics of the ultrasonic oscillator 70 and efficiently manufacture the wafer 20 from the SiC ingot 1.

[0054] Furthermore, since the stripping device 40 of the first embodiment has almost no characteristic changes of the ultrasonic oscillator 70 due to the passage of time, it can also suppress load changes during ultrasonic oscillation, and can be driven stably with a phase difference of 0%, thereby improving power efficiency (for example, from 50% in the past to almost 100%).

[0055] [Second Embodiment] A peeling device according to a second embodiment of the present invention will be described with reference to the drawings. FIG10 is a side view showing an example of the configuration of the peeling device of the second embodiment. In addition, in FIG10, the same symbols are used for the parts that are the same as those in the first embodiment, and the description is omitted.

[0056] The peeling device 40-2 of the second embodiment shown in FIG10 is the same as that of the first embodiment except that the area of ​​the bottom surface 64 is 120% of the area of ​​the first surface 2.

[0057] The stripping device 40-2 of the second embodiment is equipped with an ultrasonic oscillation unit 60, which is formed by integrating the second metal block 73 of the ultrasonic oscillator 70 with the bottom part 65 of the housing member 61 that functions as an oscillation plate. Therefore, similar to the first embodiment, it can suppress the characteristic variation of the ultrasonic oscillator 70 and efficiently manufacture the wafer 20 from the SiC crystal rod 1.

[0058] Next, the inventors of the present invention confirmed the occurrence of peeling of the second metal block 73 and the bottom part 65 of the housing member 61 when separating the wafer 20 from the same SiC crystal rod 1 in comparative examples, present invention 1, and present invention 2, thereby confirming the effectiveness of the peeling devices 40 and 40-2 of the first and second embodiments described above. The results are shown in Table 1.

[0059] [Table 1] Table 1 The generation of peeling Product 1 of the present invention none Product 2 of this invention none Comparative example have

[0060] The comparative example in Table 1 is formed by separating the second metal block 73 of the ultrasonic oscillator 70 of the peeling device 40 of the first embodiment from the bottom part 65 of the housing member 61 and fixing them with adhesive.

[0061] The first embodiment of the present invention 1 in Table 1 is the peeling device 40 of the first embodiment, and the second embodiment of the present invention 2 in Table 1 is the peeling device 40-2 of the second embodiment.

[0062] Table 1 reveals the peeling of the second metal block 73 and the bottom surface 65 of the housing member 61 during the fabrication of a wafer 20 from a 4-inch SiC crystal rod 1 in the comparative example, product 1 of the present invention, and product 2 of the present invention. In the results shown in Table 1, the frequency, current value, and application time of the alternating current applied to the piezoelectric element 71 in the comparative example, product 1 of the present invention, and product 2 of the present invention are set to be the same.

[0063] According to Table 1, in the comparative example, peeling occurred after the ultrasonic oscillator 70 was driven for 1000 hours. In contrast to this comparative example, in the present invention 1 and the present invention 2, no peeling occurred even after the ultrasonic oscillator 70 was driven for 1000 hours.

[0064] Therefore, according to Table 1, by having an ultrasonic oscillation unit 60, which is formed by integrating the second metal block 73 of the ultrasonic oscillator 70 with the bottom part 65 of the housing member 61 that functions as an oscillating plate, the peeling of the ultrasonic oscillator 70 and the bottom part 65 can be suppressed.

[0065] Furthermore, the present invention is not limited to the above-described embodiments. That is, various modifications and implementations can be made without departing from the spirit of the present invention. For example, in the present invention, the stripping devices 40, 40-2 may also have a stripping means (a means of attracting, holding and transporting the wafer 20) that has been separated from the SiC crystal rod 1 by imparting ultrasonic oscillation. [Simplified Explanation of the Diagram]

[0013] FIG1 is a top view of the SiC crystal rod to be processed by the stripping apparatus of the first embodiment. FIG2 is a side view of the SiC crystal rod shown in FIG1. ​​FIG3 is a perspective view of the wafer manufactured by the stripping apparatus of the first embodiment. FIG4 is a top view showing the state in which a stripping layer has been formed on the SiC crystal rod shown in FIG1. ​​FIG5 is a cross-sectional view along line VV in FIG4. FIG6 is a perspective view showing the state in which a stripping layer has been formed on the SiC crystal rod shown in FIG1. ​​FIG7 is a side view showing the state in which a stripping layer has been formed on the SiC crystal rod shown in FIG6. FIG8 is a side view showing an example of the configuration of the stripping apparatus of the first embodiment. FIG9 is a side cross-sectional view of the ultrasonic oscillation unit of the stripping apparatus shown in FIG8. FIG10 is a side view showing an example of the configuration of the stripping apparatus of the second embodiment.

Claims

1. A stripping apparatus for stripping a wafer to be manufactured from a semiconductor ingot with a stripping layer already formed thereon, the stripping layer being formed by focusing a laser beam of wavelength penetrable to the semiconductor ingot at a depth equivalent to the thickness of the wafer to be manufactured and irradiating the laser beam, the stripping apparatus characterized by comprising: an ingot holding unit that holds the semiconductor ingot with the wafer to be manufactured facing upwards; an ultrasonic oscillation unit disposed facing the semiconductor ingot held in the ingot holding unit and oscillating ultrasonic waves; and a liquid supply unit that supplies liquid between the wafer to be manufactured and the ultrasonic oscillation unit, the ultrasonic oscillation unit comprising: an ultrasonic oscillator having a piezoelectric element, a first metal block, a second metal block; and a housing member having a bottom surface having an area equal to or greater than the area to which ultrasonic waves are to be imparted, the housing member having a bottom portion having the bottom surface, the bottom portion being integrally formed with an end face of the second metal block in the ultrasonic oscillator. The first metal block, the second metal block, and the piezoelectric element are screwed together by bolts.

2. The stripping device as claimed in claim 1, wherein, The housing components are made of stainless steel, titanium, or aluminum.

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