Water generation device and wafer generation method

Abstract

To provide a water production device of producing water, capable of efficiently propagating supersonic waves.SOLUTION: A water production device 2 comprises a filter 4 filtering water to produce clean water, a UV irradiator 6 irradiating the clean water produced by the filter 4 with UV rays to destroy organic materials present in the clean water, an ion exchange resin 8 that refines the clean water with the organic materials having been destroyed by the UV irradiator 6, to produce pure water, and degassed water production means 10 of degassing water to produce degassed water.SELECTED DRAWING: Figure 1

Description

【Technical Field】 【0001】 The present invention relates to a water generation device and a method for generating a wafer by generating a wafer from an ingot. 【Background Art】 【0002】 Devices such as ICs, LSIs, and LEDs are formed by laminating a functional layer on the surface of a wafer made of a material such as Si (silicon) or Al2O3 (sapphire) and partitioning it by a planned division line. In addition, power devices, LEDs, etc. are formed by laminating a functional layer on the surface of a wafer made of SiC (silicon carbide) and partitioning it by a planned division line. 【0003】 The wafer on which the device is formed is processed along the planned division line by a cutting device or a laser processing device and divided into individual device chips, and each divided device chip is used in an electrical device such as a mobile phone or a personal computer. 【0004】 The wafer on which the device is formed is generally generated by thinly cutting a columnar ingot with a wire saw. The front and back surfaces of the generated wafer are polished to a mirror finish (see, for example, Patent Document 1). 【0005】 However, when the ingot is cut with a wire saw and the front and back surfaces of the cut wafer are polished, most of the ingot (70 to 80%) is discarded, which is uneconomical. In particular, in the case of a SiC ingot, it has a high hardness and is difficult to cut with a wire saw, requiring a considerable amount of time, resulting in poor productivity. In addition, the unit price of the ingot is high, and there are problems in efficiently generating a wafer. 【0006】 Therefore, the applicant proposed a technique in which a laser beam with a wavelength that is transparent to SiC is focused inside a SiC ingot, the laser beam is irradiated onto the SiC ingot to form a peeling point on the cutting surface, and the wafer is peeled off from the ingot along the cutting surface where the peeling point has been formed (see, for example, Patent Document 2). 【0007】 Furthermore, the applicant has also proposed a technique for applying ultrasound to an ingot via a layer of water to facilitate the separation of wafers to be produced from the ingot (see, for example, Patent Document 3). [Prior art documents] [Patent Documents] 【0008】 [Patent Document 1] Japanese Patent Publication No. 2000-94221 [Patent Document 2] Japanese Patent Publication No. 2016-111143 [Patent Document 3] Japanese Patent Publication No. 2016-146446 [Overview of the Initiative] [Problems that the invention aims to solve] 【0009】 However, while applying ultrasound to an ingot with a delamination point improves delamination, it still takes some time for the wafer to delaminate from the ingot. Therefore, there is a need to shorten the time from the start of ultrasound application to the completion of wafer delamination. 【0010】 Such problems can also occur when a laser beam with a wavelength that penetrates silicon, sapphire, or other ingots is focused inside the ingot, and the laser beam is irradiated onto the ingot to create a peeling point, thereby peeling off a wafer from the silicon, sapphire, or other ingot. 【0011】 The object of the present invention is to provide a water generating device that can efficiently propagate ultrasonic waves into water, and a method for producing wafers that can be efficiently peeled off. [Means for solving the problem] 【0012】 According to the present invention, the following water generating device is provided that solves the above problems. That is, "A water generating device, The system includes a filter that filters water to produce clean water, an ultraviolet irradiator that irradiates the clean water produced by the filter with ultraviolet light to destroy organic matter in the clean water, an ion exchange resin that purifies the clean water from which organic matter has been destroyed by the ultraviolet irradiator into pure water, and a deaerated water generating means that degasses the water to produce deaerated water. The degassed water generating means comprises a chamber, a water inlet for receiving water into the chamber, a depressurization unit for reducing the pressure inside the chamber, an ultrasonic oscillating unit for applying ultrasonic waves to the water inside the chamber, and a degassed water outlet for discharging degassed water from the chamber. A "water generating device" will be provided. 【0013】 Preferably, the degassed water generating means is disposed between the filter and the ultraviolet irradiator, between the ultraviolet irradiator and the ion exchange resin, or downstream of the ion exchange resin. 【0015】 The ultrasonic oscillator preferably emits ultrasonic waves in the range of 0.1 MHz to 1.0 MHz, and the degassing unit preferably reduces the pressure inside the chamber to 0.2 atmospheres or less. The degassed water generation means preferably generates degassed water with an oxygen content of 2.0 mg / liter or less. 【0016】 It may be installed in a circulation path that supplies deaerated water to a deaerated water user and receives used deaerated water discharged from the deaerated water user. 【0017】 A precision filter and a temperature controller may be provided downstream of the ion exchange resin. It is preferable to provide a wastewater tank for containing wastewater upstream of the filter. 【0018】 Furthermore, the present invention provides the following wafer manufacturing method that solves the above problems. That is, A method for generating wafers from ingots, Position the focus point of a laser beam having a wavelength that is transparent to the ingot at a depth corresponding to the thickness of the wafer to be formed from the ingot's end face, irradiate the ingot with the laser beam to form a modified layer and form a peeling starting point in a peeling starting point forming step. Include a peeling step of peeling the wafer to be formed from the ingot from the peeling starting point. In the peeling step, there is provided a method for producing a wafer in which degassed water generated by the above-described water production device is supplied to the end face of the ingot to form a layer of degassed water, ultrasonic waves are applied to destroy the peeling starting point. 【0019】 The ingot may be a SiC ingot. The SiC ingot has a first surface, a second surface opposite to the first surface, a c-axis extending from the first surface to the second surface, and a c-plane perpendicular to the c-axis. The c-axis is inclined with respect to the perpendicular of the first surface, and an off-angle is formed between the c-plane and the first surface. The peeling starting point forming step preferably includes a modified layer forming step of relatively moving the focus point of the laser beam and the SiC ingot in a direction perpendicular to the direction in which the off-angle is formed to form a linear modified layer, and an index step of relatively moving the focus point of the laser beam and the SiC ingot in the direction in which the off-angle is formed and indexing by a predetermined amount. 【Advantages of the Invention】 【0020】 The water production device of the present invention includes a filter for filtering water to produce clean water, an ultraviolet irradiator for irradiating the clean water generated by the filter with ultraviolet rays to destroy organic substances in the clean water, an ion exchange resin for purifying the clean water in which organic substances have been destroyed by the ultraviolet irradiator into pure water, and a degassed water generation means for degassing water to generate degassed water. The degassed water generating means comprises a chamber, a water inlet for receiving water into the chamber, a depressurization unit for reducing the pressure inside the chamber, an ultrasonic oscillating unit for applying ultrasonic waves to the water inside the chamber, and a degassed water outlet for discharging degassed water from the chamber. Therefore, it is possible to produce water that can efficiently transmit ultrasonic waves. 【0021】 Also, the method for producing a wafer of the present invention Position the focus point of a laser beam having a wavelength that is transmissive to the ingot at a depth corresponding to the thickness of the wafer to be formed from the ingot end face, irradiate the ingot with the laser beam to form a modified layer and form a peeling starting point in a peeling starting point forming step, and a peeling step of peeling the wafer to be formed from the ingot from the peeling starting point. In the peeling step, deaerated water generated by the above-described water generation device is supplied to the end face of the ingot to generate a layer of deaerated water, ultrasonic waves are applied to break the peeling starting point, so that the wafer can be peeled efficiently. 【Brief Description of the Drawings】 【0022】 [Figure 1] Circuit diagram of the water generation device configured according to the present invention. [Figure 2] (a) Perspective view of the ingot, (b) Plan view of the ingot shown in (a), (c) Front view of the ingot shown in (a). [Figure 3] (a) Perspective view showing the peeling starting point forming step, (b) Front view showing the peeling starting point forming step, (c) Cross-sectional view of the ingot in which the peeling starting point is formed. [Figure 4] Schematic diagram showing an example of the peeling step. [Figure 5] Schematic diagram showing another example of the peeling step. 【Mode for Carrying Out the Invention】 【0023】 Hereinafter, preferred embodiments of the water generation device and the wafer generation method of the present invention will be described with reference to the drawings. 【0024】 (Water generation device 2) First, explaining from the water generation device, the water generation device shown by reference numeral 2 in its entirety in FIG. 1 includes a filter 4 that filters water to generate clean water, an ultraviolet irradiator 6 that irradiates the clean water generated by the filter 4 with ultraviolet rays to destroy organic substances in the clean water, an ion exchange resin 8 that purifies the clean water in which organic substances have been destroyed by the ultraviolet irradiator 6 into pure water, and a deaerated water generation means 10 that deaerates water to generate deaerated water. 【0025】 (Filter 4) The filter 4 of this embodiment has a first filter 4a and a second filter 4b, and the first and second filters 4a and 4b are installed in a clean water receiving pan 12 that receives the filtered clean water. 【0026】 Upstream of the filter 4, a wastewater tank 14 for containing wastewater and a wastewater pump 16 for discharging wastewater from the wastewater tank 14 are located. A solenoid valve 20 and a pressure gauge 22 are provided in the pipeline 18 connecting the wastewater pump 16 and the filter 4. 【0027】 When the electromagnetic switching valve 20 is not energized, wastewater discharged from the wastewater pump 16 flows into the first filter 4a through the branch pipe 24a. On the other hand, when the electromagnetic switching valve 20 is energized, wastewater flows into the second filter 4b through the branch pipe 24b. The water that flows into the first and second filters 4a and 4b is filtered to become clean water and flows out into the clean water receiving pan 12. 【0028】 If filtration continues using the first or second filters 4a and 4b, impurities will accumulate on the filter in use, causing clogging and an increase in the pressure reading of the pressure gauge 22. When the pressure reading of the pressure gauge 22 exceeds a predetermined value, the control means (not shown) of the water generator 2 determines that the filter in use has lost its filtration function and activates the electromagnetic switching valve 20 to switch the filter through which wastewater flows. This allows the filter that has lost its filtration function to be replaced without stopping the operation of the water generator 2. 【0029】 The control means for the water generator 2 consists of a computer that includes a central processing unit (CPU) that performs calculations according to a control program, a read-only memory (ROM) that stores the control program and the like, and a read-write random access memory (RAM) that stores the calculation results and the like, and controls the operation of the water generator 2. 【0030】 (UV irradiator 6) The ultraviolet irradiator 6 is located downstream of the filter 4. In the illustrated embodiment, a clean water tank 28 for storing the clean water filtered by the filter 4 and a clean water pump 30 for discharging the clean water from the clean water tank 28 are provided between the clean water pan receiver 12 and the ultraviolet irradiator 6. The clean water filtered by the filter 4 flows into the clean water tank 28 through the pipeline 26. The clean water sent from the clean water tank 28 to the ultraviolet irradiator 6 via the pipeline 31 by the clean water pump 30 is then irradiated with ultraviolet light in the ultraviolet irradiator 6. This sterilizes the clean water and destroys organic matter in the clean water. 【0031】 (Ion exchange resin 8) The ion exchange resin 8 of this embodiment comprises a first ion exchange resin 8a and a second ion exchange resin 8b. The first and second ion exchange resins 8a and 8b are connected to the ultraviolet irradiator 6 via a conduit 32, and a solenoid valve 34 is provided in the conduit 32. When the solenoid valve 34 is not energized, clean water discharged from the clean water pump 30 and passing through the ultraviolet irradiator 6 is sent to the first ion exchange resin 8a, and when the solenoid valve 34 is energized, clean water that has passed through the ultraviolet irradiator 6 is sent to the second ion exchange resin 8b. 【0032】 The clean water sent to the first or second ion exchange resins 8a and 8b is purified into pure water through ion exchange. Furthermore, the electromagnetic switching valve 34 allows for the replacement of the first or second ion exchange resins 8a and 8b, which have had their water flow stopped, while the water generator 2 continues to operate. 【0033】 The purified water obtained by ion exchange of clean water may contain fine particles such as resin debris from the ion exchange resin 8. For this reason, it is preferable that the water generator 2 is equipped with a precision filter 36 downstream of the ion exchange resin 8 to remove the above-mentioned fine particles. 【0034】 The pipeline 38 connecting the ion exchange resin 8 and the precision filter 36 is equipped with a detection means 40 for detecting the pressure and resistivity of the pure water in the pipeline 38. When the pressure detected by the detection means 40 exceeds a predetermined value, the control means of the water generator 2 determines that fine substances such as resin debris detached from the ion exchange resin 8 have accumulated on the precision filter 36, causing the precision filter 36 to lose its filtration function, and notifies the operator accordingly. Furthermore, when the resistivity of the pure water detected by the detection means 40 falls below a predetermined value, the control means of the water generator 2 determines that the function of the ion exchange resin in use has deteriorated, and activates the electromagnetic switching valve 34 to switch the ion exchange resin through which the clean water passes. 【0035】 (Degassed water generation means 10) In the illustrated embodiment, as shown in Figure 1, the degassed water generation means 10 is located downstream of the ion exchange resin 8 (more specifically, downstream of the precision filter 36). The degassed water generation means 10 may also be located between the filter 4 and the ultraviolet irradiator 6, or between the ultraviolet irradiator 6 and the ion exchange resin 8. However, in order to prevent gas from remelting into the degassed water before use, it is desirable that the degassed water generation means 10 be located downstream of the precision filter 36 and immediately before the degassed water usage device, as in this embodiment. 【0036】 The pipeline 42 connecting the precision filter 36 and the deaerated water generation means 10 is equipped with a pure water pump 44 for sending the pure water filtered by the precision filter 36 to the deaerated water generation means 10, and a temperature controller 46 for adjusting the temperature of the pure water sent to the deaerated water generation means 10. 【0037】 The degassed water generation means 10 includes a chamber 48, a water inlet 50 for receiving water into the chamber 48, a depressurization unit 52 for reducing the pressure inside the chamber 48, an ultrasonic oscillating unit 54 for applying ultrasonic waves to the water inside the chamber 48, and a degassed water outlet 56 for discharging degassed water from the chamber 48. A suction hole 58 is formed in the upper part of the chamber 48, and this suction hole 58 is connected to the depressurization unit 52, which may be composed of a vacuum pump. 【0038】 The water generating device 2 described above is installed in a circulation path that supplies deaerated water to the deaerated water usage device 60 (a peeling device in the illustrated embodiment) and also receives used deaerated water discharged from the deaerated water usage device 60. 【0039】 The deaerated water generated by the deaerated water generation means 10 is supplied from the deaerated water generation means 10 to the deaerated water usage device 60 via the pipeline 64 by the deaerated water pump 62. The deaerated water used in the deaerated water usage device 60 is then sent from the deaerated water usage device 60 to the wastewater tank 14 via the pipeline 68 by the discharge pump 66. 【0040】 (Degassing water usage device 60: peeling device) The degassing water usage device 60 comprises a water tank 70, a rod 72 positioned to move up and down above the water tank 70, and an ultrasonic oscillator 74 attached to the lower end of the rod 72. A holding table 76 for holding ingots is provided inside the water tank 70, and an outlet 78 for discharging used degassed water is formed at the lower end of the water tank 70. 【0041】 (Water generation method) To describe the method of generating water using the water generation device 2 as described above, first, wastewater is sent from the wastewater tank 14 to the filter 4 by the wastewater pump 16, where the wastewater is filtered to produce clean water. The generated clean water is temporarily stored in the clean water tank 28. Next, the clean water in the clean water tank 28 is sent to the ultraviolet irradiator 6 by the clean water pump 30, where ultraviolet light is irradiated onto the clean water to sterilize it and destroy organic matter in the clean water. 【0042】 Next, clean water is introduced into the ion exchange resin 8 to purify it into pure water. Then, fine substances in the pure water, such as resin debris from the ion exchange resin 8, are removed by the precision filter 36, and the pure water is then supplied from the precision filter 36 to the degassed water generation means 10 by the pure water pump 44. At this time, the temperature controller 46 adjusts the temperature of the pure water to an appropriate temperature (for example, 20°C). 【0043】 When pure water W is supplied into the chamber 48 of the degassed water generation means 10, the pressure inside the chamber 48 is reduced by the depressurization unit 52 (for example, to 0.2 atmospheres or less), and ultrasonic waves (for example, about 0.1 MHz to 1.0 MHz) are applied to the pure water W inside the chamber 48 by the ultrasonic oscillation unit 54. As a result, gas dissolved in the pure water W appears as bubbles, and the gas is removed from the pure water W, generating degassed water. The degassed water generated in this way has very few impurities or fine bubbles that absorb ultrasonic energy, so ultrasonic waves can be propagated efficiently. 【0044】 Furthermore, it is preferable to have a low air pressure inside the chamber 48 when generating degassed water, because degassing is promoted as the pressure decreases. The relationship between the air pressure inside the chamber 48 and the lower limit of the oxygen content of the degassed water is shown below. 【0045】 Air pressure inside the chamber (atm) Lower limit of oxygen content in degassed water (mg / liter) 1.0 8.1 0.7 6.55 0.65 5.8 0.6 5.48 0.5 4.97 0.4 4.08 0.3 3.1 0.2 1.96 0.1 1.14 0.03 0.36 【0046】 Next, preferred embodiments of the wafer production method of the present invention will be described. 【0047】 (82 ingots) Figure 2 shows a cylindrical ingot 82 processed by the wafer manufacturing method of the present invention. The ingot 82 shown is formed from single-crystal SiC (silicon carbide). 【0048】 The ingot 82 has a circular first surface 84, a circular second surface 86 located opposite the first surface 84, a circumferential surface 88 located between the first surface 84 and the second surface 86, a c-axis extending from the first surface 84 to the second surface 86, and a c-plane perpendicular to the c-axis (see Figure 2(c)). At least the first surface 84 is flattened by grinding or polishing to the extent that it does not obstruct the incidence of the laser beam. 【0049】 In ingot 82, the c-axis is inclined with respect to the perpendicular 90 of the first face 84, and an off-angle α (for example, α = 1, 3, or 6 degrees) is formed between the c-face and the first face 84. The direction in which the off-angle α is formed is indicated by arrow A in Figure 2. 【0050】 On the circumferential surface 88 of the ingot 82, a rectangular first orientation flat 92 and a second orientation flat 94 are formed, both indicating the crystal orientation. The first orientation flat 92 is parallel to the direction A in which the off-angle α is formed, and the second orientation flat 94 is perpendicular to the direction A in which the off-angle α is formed. As shown in Figure 2(b), when viewed from above, the length L2 of the second orientation flat 94 is shorter than the length L1 of the first orientation flat 92 (L2 <L1)。 【0051】 The ingot processed by the wafer manufacturing method of the present invention is not limited to the ingot 82 described above. It may also be a SiC ingot in which the c-axis is not tilted with respect to the perpendicular to the first surface and the off-angle α between the c-plane and the first surface is 0 degrees (i.e., the perpendicular to the first surface and the c-axis coincide), or an ingot formed from a material other than SiC, such as Si (silicon), Al2O3 (sapphire), or GaN (gallium nitride). 【0052】 (Peel-starting point formation process) In the illustrated embodiment, first, a laser beam with a wavelength that is transparent to the ingot 82 is focused at a depth corresponding to the thickness of the wafer to be produced from the end face of the ingot 82, and a delamination initiation step is performed in which the laser beam is irradiated onto the ingot 82 to form a modified layer and delamination initiation point. 【0053】 The peeling point formation process can be carried out, for example, using the laser processing apparatus 96 shown in Figure 3. The laser processing apparatus 96 comprises a chuck table 98 for suction holding the ingot 82, an oscillator (not shown) that emits a pulsed laser beam LB with a wavelength that is transparent to the ingot 82, and a concentrator 100 that focuses the pulsed laser beam LB emitted by the oscillator and irradiates the ingot 82 held by suction on the chuck table 98 with the pulsed laser beam LB. 【0054】 The chuck table 98 is configured to rotate freely around an axis extending in the vertical direction, and is also configured to move freely in the X-axis direction, indicated by arrow X in Figure 3(a), and in the Y-axis direction, which is perpendicular to the X-axis direction (indicated by arrow Y in Figure 3(a)). The XY plane defined by the X-axis and Y-axis directions is essentially horizontal. 【0055】 Continuing the explanation with reference to Figure 3, in the peeling point formation process, first, the ingot 82 is held by suction on the upper surface of the chuck table 98 with the first surface 84 facing upwards. Next, the ingot 82 is imaged from above by the imaging means (not shown) of the laser processing apparatus 96, and based on the image of the ingot 82 captured by the imaging means, the orientation of the ingot 82 is adjusted to a predetermined orientation, and the positional relationship between the ingot 82 and the light concentrator 100 is adjusted. 【0056】 When adjusting the orientation of the ingot 82 to a predetermined orientation, the second orientation flat 94 is aligned in the X-axis direction, as shown in Figure 3(a). This aligns the direction perpendicular to the direction A in which the off-angle α is formed with the X-axis direction, and also aligns the direction A in which the off-angle α is formed with the Y-axis direction. 【0057】 Next, the focal point FP (see Figure 3(b)) of the laser beam LB is positioned on the first surface 84 of the ingot 82 at a depth corresponding to the thickness of the wafer to be produced. Then, while relatively moving the focal point FP and the ingot 82 in the X-axis direction (the direction perpendicular to the direction A in which the off-angle α is formed), the laser beam LB with a wavelength that is transparent to the ingot 82 is irradiated onto the ingot 82 from the focuser 100. As a result, as shown in Figure 3(c), a linear modified layer 102 in which SiC is separated into Si (silicon) and C (carbon) can be formed along the X-axis direction. In addition, cracks 104 extending along the c-plane are also formed from the modified layer 102 (modified layer formation step). 【0058】 Next, the focusing point FP and the ingot 82 are relatively indexed in the Y-axis direction (direction A where the off-angle is formed) (indexing step). The indexing amount Li is set to a length that does not exceed the width of the crack 104, so that adjacent cracks 104 in the Y-axis direction overlap when viewed vertically. Then, by alternately repeating the modified layer formation step and the indexing step, a delamination starting point 106 having multiple modified layers 102 and cracks 104 is formed at a depth (planned cutting surface) corresponding to the thickness of the wafer to be produced. 【0059】 Such a peeling point formation process can be carried out, for example, under the following processing conditions. Wavelength of pulsed laser beam: 1064nm Repeat frequency: 80kHz Average output: 3.2W Pulse width: 4ns Diameter of the focal point: 10 μm Numerical Aperture (NA): 0.45 Index amount: 400 μm Wafer thickness to be produced: 700 μm 【0060】 (Peeling process) After performing the peeling point formation process, a peeling process is carried out to peel the wafer to be produced from the ingot 82 from the peeling point 106. The peeling process can be performed using the peeling apparatus 60 described above. 【0061】 Referring to Figure 4, in the peeling process, first, the wafer to be produced is positioned upwards (i.e., with the first surface 84, which is the end face closer to the peeling initiation point 106, facing upwards), and the ingot 82 is held by the holding table 76. In this case, an adhesive (for example, an epoxy resin adhesive) may be interposed between the second surface 86 of the ingot 82 and the upper surface of the holding table 76 to fix the ingot 82 to the holding table 76, or an suction force may be generated on the upper surface of the holding table 76 to hold the ingot 82 by suction. 【0062】 Next, degassed water W' is supplied into the tank 70 until the water level is higher than the top surface of the ingot 82. Then, the rod 72 is lowered, and the ultrasonic oscillator 74 is positioned slightly above the first surface 84 of the ingot 82. The distance between the first surface 84 and the ultrasonic oscillator 74 can be about 2-3 mm. Then, ultrasonic waves are emitted from the ultrasonic oscillator 74, and the delamination point 106 is destroyed by the ultrasonic waves through the layer of degassed water W' between the first surface 84 and the ultrasonic oscillator 74. This makes it possible to separate the wafer to be produced from the ingot 82 from the delamination point 106. 【0063】 In the example described above, a method was explained in which degassed water W' is stored in the water tank 70. However, as shown in Figure 5, a layer of degassed water W' may also be created by supplying degassed water W' from the supply nozzle 108 between the first surface 84 of the ingot 82 and the ultrasonic oscillator 74. 【0064】 In this process, the wafer to be produced is positioned upwards, and the ingot 82 is held on the holding table 76. Then, the ultrasonic oscillator 74 is positioned slightly above the first surface 84, and degassed water W' is supplied from the supply nozzle 108 between the first surface 84 and the ultrasonic oscillator 74 to create a layer of degassed water W'. Ultrasound is then emitted from the ultrasonic oscillator 74, and the delamination point 106 is destroyed by the ultrasound through the layer of degassed water W' between the first surface 84 and the ultrasonic oscillator 74. This allows the wafer to be produced from the ingot 82 to be separated from the delamination point 106. 【0065】 In the example shown in Figure 4, there is time required to store the degassed water W' in the water tank 70 and time required to discharge the used degassed water W' from the water tank 70 after wafer peeling. In contrast, in the example shown in Figure 5, a layer of degassed water W' can be immediately generated by supplying the degassed water W' from the supply nozzle 108 between the first surface 84 and the ultrasonic oscillator 74, and the used degassed water W' can be discharged simultaneously with the application of ultrasound to the ingot 82. Therefore, the peeling process time can be shortened in the example in Figure 5 compared to the example in Figure 4. 【0066】 As described above, in the illustrated embodiment, degassed water W' is supplied to the end face of the ingot 82 to create a layer of degassed water W', and ultrasound is applied to the ingot 82 through the layer of degassed water W' to destroy the delamination initiation point 106. Therefore, the energy of the ultrasound is not converted into cavitation, and the energy of the ultrasound can be effectively applied to the ingot 82. Thus, the wafer can be efficiently delaminated from the ingot 82. 【0067】 <Experiment> The inventors generated multiple layers of degassed water by changing the air pressure inside a chamber, applied ultrasound to an ingot through the generated layers of degassed water, and measured the time it took for the delamination point to be destroyed and the wafer to delaminate from the ingot. They also measured the sound pressure (amplitude) of the ingot when ultrasound was applied to it. The frequency of the ultrasound used to generate the degassed water was 0.1 MHz, and the frequency of the ultrasound applied to the ingot to destroy the delamination point was 25 kHz. The temperature of the degassed water was 20°C. 【0068】 <Experimental Results> Oxygen content of degassed water (mg / liter), peeling time (seconds), sound pressure (V) 8.1 1352 1.54 6.55 1223 1.56 5.8 1123 1.66 5.48 1082 1.68 4.97 1002 1.88 4.08 815 1.88 3.1 753 1.88 1.96 356 2.20 1.14 243 2.32 0.36 236 3.12 【0069】 As can be understood by referring to the experimental results above, the lower the oxygen content of the degassed water, the shorter the time it takes for the wafer to detach from the ingot, and the higher the sound pressure of the ingot. Furthermore, the detachment time was 753 seconds when the oxygen content of the degassed water was 3.1 mg / liter, and 356 seconds when the oxygen content of the degassed water was 1.96 mg / liter. When the oxygen content of the degassed water changed from 3.1 mg / liter to 1.96 mg / liter, the detachment time was reduced to less than half. Therefore, from the viewpoint of efficiently producing wafers from ingots, it is preferable to produce degassed water with an oxygen content of 2.0 mg / liter or less. [Explanation of Symbols] 【0070】 2: Water generator 4: Filter 4a: First filter 4b: Second filter 6: Ultraviolet irradiator 8: Ion exchange resin 8a: First ion exchange resin 8b: Second ion exchange resin 10: Degassed water generation means 14: Wastewater tank 36: Precision Filters 46: Temperature controller 48: Chamber 50:Water inlet 52: Depressurization section 54: Ultrasonic oscillator 56: Degassing water outlet 60: Degassing water usage equipment (peeling equipment) 82: Ingot 84: First side 86: The second side 90: Perpendicular line 102: Modified layer 106: Detachment starting point LB: Laser beam FP: Focus point W: Pure water W': Degassed water

Claims

[Claim 1] A water generating device, A water generating apparatus comprising: a filter that filters water to produce clean water; an ultraviolet irradiator that irradiates the clean water produced by the filter with ultraviolet light to destroy organic matter in the clean water; an ion exchange resin that purifies the clean water from which organic matter has been destroyed by the ultraviolet irradiator into pure water; and a degassed water generating means that degasses water to produce degassed water, wherein the degassed water generating means comprises: a chamber; a water inlet that receives water into the chamber; a depressurization unit that reduces the pressure inside the chamber; an ultrasonic oscillating unit that imparts ultrasonic waves to the water inside the chamber; and a degassed water outlet that discharges degassed water from the chamber. [Claim 2] The water generating apparatus according to claim 1, wherein the degassed water generating means is disposed between the filter and the ultraviolet irradiator, between the ultraviolet irradiator and the ion exchange resin, or downstream of the ion exchange resin. [Claim 3] The water generating apparatus according to claim 1, wherein the ultrasonic oscillating unit oscillates ultrasonic waves in the frequency range of 0.1 MHz to 1.0 MHz, and the depressurizing unit reduces the pressure inside the chamber to 0.2 atmospheres or less. [Claim 4] The water generating apparatus according to claim 1, wherein the deaerated water generating means generates deaerated water with an oxygen content of 2.0 mg / liter or less. [Claim 5] The water generating device according to claim 1, which is arranged in a circulation path that supplies deaerated water to a deaerated water usage device and receives used deaerated water discharged from the deaerated water usage device. [Claim 6] The water generating apparatus according to claim 1, further comprising a precision filter and a temperature controller downstream of the ion exchange resin. [Claim 7] The water generating apparatus according to claim 1, further comprising a wastewater tank for containing wastewater on the upstream side of the filter. [Claim 8] A wafer production method for producing wafers from ingots, A delamination initiation step involves positioning the focal point of a laser beam with a wavelength that is transparent to the ingot at a depth corresponding to the thickness of the wafer to be produced from the edge face of the ingot, and irradiating the ingot with the laser beam to form a modified layer and delamination initiation point, The process includes a peeling step of peeling off the wafer to be produced from the ingot from the peeling starting point, A method for producing a wafer, wherein in the peeling step, degassed water generated by a water generating device according to any one of claims 1 to 7 is supplied to the end face of an ingot to create a layer of degassed water, and ultrasonic waves are applied to destroy the peeling initiation point. [Claim 9] The method for producing a wafer according to claim 8, wherein the ingot is a SiC ingot. [Claim 10] The SiC ingot has a first face, a second face opposite the first face, a c-axis extending from the first face to the second face, and a c-face perpendicular to the c-axis, wherein the c-axis is inclined with respect to the perpendicular to the first face and an off-angle is formed between the c-face and the first face. The delamination starting point formation step includes a modified layer formation step in which the focusing point of the laser beam and the SiC ingot are moved relative to each other in a direction perpendicular to the direction in which the off-angle is formed to form a linear modified layer, A method for producing a wafer according to claim 9, comprising an index step of moving the focal point of the laser beam and the SiC ingot relative to each other in the direction in which the off-angle is formed, thereby feeding the index by a predetermined amount.

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