Ultrasonic vibration unit

Abstract

To provide an ultrasonic vibration unit capable of efficiently generating cavitation.SOLUTION: An ultrasonic vibration unit 60 includes a top plate (vibration plate) 62 of a housing 61, to which an ultrasonic vibrator is fixed, and a matching layer 65 laminated on the top plate 62. Ultrasonic waves from the ultrasonic vibrator are radiated from a surface of the matching layer 65 with irregularities 66 via water that is liquid. Namely, in the configuration, water is irradiated with ultrasonic waves from the surface of the matching layer 65 with irregularities 66, so that cavitation can be efficiently generated (i.e. the occurrence frequency of cavitation can be increased).SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an ultrasonic vibration unit that irradiates ultrasonic waves into liquid. [Background technology]

[0002] When ultrasonic waves are irradiated into a liquid, cavitation occurs, in which minute bubbles in the liquid expand and collapse. It is known that in cavitation, powerful shock waves are generated as the bubbles collapse.

[0003] A cleaning method is known that utilizes shock waves generated by this cavitation to clean an object to be cleaned (Patent Document 1).

[0004] As another example of using shock waves generated by cavitation, a method is known for dividing a workpiece having a modified layer formed therein into multiple chips (Patent Document 2). Such a modified layer is formed, for example, by focusing and irradiating a laser beam inside the workpiece. The shock waves generated by cavitation can divide the workpiece into multiple chips starting from the modified layer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2022-033584 [Patent Document 2] JP 2019-220581 A Summary of the Invention [Problem to be solved by the invention]

[0006] The above-mentioned cleaning method and division method utilize cavitation, and it is known that the efficiency of the treatment is improved by increasing the frequency of cavitation. Therefore, in an ultrasonic vibration unit used for irradiating a liquid with ultrasonic waves, it is required to improve the efficiency of generating cavitation.

[0007] The present invention has been made in view of the above problems, and an object of the present invention is to provide an ultrasonic vibration unit capable of efficiently generating cavitation. [Means for solving the problem]

[0008] The ultrasonic vibration unit of the present invention (the present ultrasonic vibration unit) is an ultrasonic vibration unit that irradiates ultrasonic waves into a liquid, and comprises an ultrasonic vibrator that is a source of the ultrasonic waves, a vibration plate having the ultrasonic vibrator fixed to a first surface, and a matching layer that is fixed to a second surface of the vibration plate opposite the first surface and is formed from a material having a smaller acoustic impedance than the vibration plate, and the matching layer has unevenness on the surface opposite to the surface in contact with the vibration plate. Effect of the Invention

[0009] This ultrasonic vibration unit has a vibration plate to which an ultrasonic vibrator is fixed, and a matching layer laminated on the vibration plate. This ultrasonic vibration unit is configured to irradiate ultrasonic waves to the liquid from the uneven surface of the matching layer. This makes it possible to efficiently generate cavitation (i.e., to increase the frequency of cavitation).

[0010] In addition, in this ultrasonic vibration unit, the matching layer is made of a material having a smaller acoustic impedance than the vibration plate. Therefore, the matching layer can reduce the acoustic loss between the vibration plate, which is ultrasonically vibrated by the ultrasonic transducer, and the liquid to which the ultrasonic waves are to be applied. Therefore, it is possible to efficiently irradiate the liquid with ultrasonic waves. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is an explanatory diagram illustrating a configuration of a division device. [Diagram 2] 2(a) and 2(b) are explanatory diagrams showing the structure of the wafer 100. FIG. [Diagram 3] FIG. 3(a) is a perspective view showing the configuration of the ultrasonic vibration unit, and FIG. 3(b) is an explanatory diagram showing projections and recesses. [Figure 4] FIG. 2 is a perspective view showing a configuration of an ultrasonic vibration unit. [Diagram 5] FIG. 2 is an explanatory diagram showing a configuration of an ultrasonic vibration unit. [Figure 6] FIG. 2 is a perspective view showing a configuration of an ultrasonic vibration unit. [Figure 7] FIG. 1 is an explanatory diagram showing the configuration of an experimental device. [Figure 8] 8(a) and 8(b) are explanatory diagrams showing the results of a cavitation efficiency verification experiment. [Figure 9] 9(a) and 9(b) are explanatory diagrams showing the results of a divisibility verification experiment. [Figure 10] 10(a) and 10(b) are explanatory diagrams showing the results of a divisibility verification experiment. [Figure 11] 1A to 1C are diagrams showing configurations of ultrasonic vibration units according to ultrasonic frequency bands. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The dividing apparatus 50 according to this embodiment shown in FIG. 1 divides a disk-shaped wafer 100 shown in FIG. 2(a) to manufacture chips.

[0013] The wafer 100 is an example of a workpiece, and is, for example, a disk-shaped semiconductor wafer. The wafer 100 has, for example, a SiC substrate. A lattice-shaped dividing lines 102 are formed on a surface 101 of the wafer 100, and devices 103 are formed in the areas partitioned by the dividing lines 102. In addition, a modified layer (not shown) is formed inside the wafer 100 along the dividing lines 102 by irradiation with a laser beam or the like.

[0014] As shown in FIG. 2(b), a metal film 106 is formed on the back surface 105 of the wafer 100. The metal film 106 constitutes an electrode when the wafer 100 is divided into a plurality of chips (device chips) including one device 103. The metal film 106 is composed of, for example, a complex of Ti, Ni, and Au. In this case, for example, the thicknesses of Ti and Ni are 1 μm, the thickness of Au is 3 μm, and the thickness of the metal film 106 is 5 μm. The total thickness of the wafer 100 is 570 μm.

[0015] As shown in FIG. 2( b ), a protective tape 107 (not shown in FIG. 2( a )) having the same diameter as the wafer 100 is attached to the front surface 101 of the wafer 100 .

[0016] The dividing apparatus 50 shown in FIG. 1 performs a dividing step on such a wafer 100, dividing the wafer 100 along the internal modified layer to form a plurality of chips. 1, the dividing apparatus 50 includes a water tank 51 for storing water L, a wafer holding member 55 for holding and transporting the wafer 100, an ultrasonic vibration unit 60 for irradiating the liquid with ultrasonic waves, and a control unit 57 serving as a control device. The water L is an example of a liquid through which ultrasonic vibrations are propagated.

[0017] The wafer holding member 55 can place the wafer 100 in the water L of the water tank 51 by adsorbing and holding the front surface 101 side of the wafer 100 to which the protective tape 107 is attached.

[0018] The ultrasonic vibration unit 60 propagates ultrasonic waves through the water L in the water tank 51 to generate cavitation, and is provided on the bottom surface 52 of the water tank 51. As shown in Figures 3(a) and 4, the ultrasonic vibration unit 60 includes a housing 61 having an upper plate (lid plate) 62 and a lower bottom plate 63. As shown in Figure 1, the ultrasonic vibration unit 60 is disposed in the water tank 51 such that the bottom plate 63 of the housing 61 contacts the bottom surface 52 of the water tank 51.

[0019] As shown in FIGS. 5 and 6, the ultrasonic vibration unit 60 includes, inside the housing 61, an ultrasonic vibrator 70 that serves as a source of ultrasonic waves.

[0020] The ultrasonic transducer 70 is a bolt-tightened Langevin type ultrasonic transducer. As shown in Fig. 5, the ultrasonic transducer 70 includes a first horn 71 and a second horn 77, a first piezoelectric element 72 and a second piezoelectric element 73 sandwiched between the first horn 71 and the second horn 77, a first electrode 75 disposed between the first horn 71 and the first piezoelectric element 72, a second electrode 76 disposed between the second horn 77 and the second piezoelectric element 73, and a bolt 74 for fixing them.

[0021] In the ultrasonic transducer 70, by applying an AC voltage to the first electrode 75 and the second electrode 76 from an AC power source 201 located, for example, outside the housing 61, ultrasonic vibrations can be generated from the tip of the first horn 71 toward the outside.

[0022] 5, in this embodiment, the ultrasonic transducer 70 is fixed to the back surface (first surface) of the upper plate 62 of the housing 61, and the tip of the first horn 71 of the ultrasonic transducer 70 is in contact with the upper plate 62 of the housing 61. Therefore, the ultrasonic transducer 70 is configured to propagate ultrasonic vibrations to the upper plate 62.

[0023] 3(a) and 5, a matching layer 65 is fixed to a surface (a second surface opposite to the first surface) of an upper plate 62 of the housing 61. The matching layer 65 is a plate-shaped member, and is laminated on the upper plate 62 of the housing 61. The matching layer 65 is adhered to the surface of the upper plate 62 with an adhesive such as an epoxy resin adhesive or a silicone adhesive. When a silicone adhesive is used, the matching layer 65 can be easily attached to and detached from the upper plate 62.

[0024] FIG. 3(b) shows an enlarged view of a portion of the surface of the matching layer 65 shown in FIG. 3(a). As shown in FIG. 3(b), the matching layer 65 has irregularities 66 on its surface (the surface opposite to the surface in contact with the upper plate 62). The irregularities 66 are formed by making a plurality of lattice-shaped grooves 661 on the surface of the matching layer 65, for example, by dicing. The width and depth of these grooves are, for example, 100 μm. Furthermore, the protruding portions 662 of the irregularities 66 are formed in a substantially cubic shape with a width of 100 μm and a height of 100 μm. In the ultrasonic vibration unit 60, the surface of the matching layer 65 is the surface that comes into contact with the water L in the water tank 51, as shown in FIG. 1.

[0025] In this manner, in the ultrasonic vibration unit 60, the ultrasonic transducer 70 is fixed to the back surface of the top plate 62 of the housing 61, and the tip of the first horn 71 of the ultrasonic transducer 70 is in contact with the top plate 62 of the housing 61. Therefore, the top plate 62 of the housing 61 is a vibration plate to which the ultrasonic transducer 70 is fixed to the back surface, which is the first surface, and ultrasonic vibrations from the ultrasonic transducer 70 are transmitted. In addition, a matching layer 65 is laminated on the top plate 62, and the surface of the matching layer 65 is in contact with the water L in the water tank 51.

[0026] Therefore, in the ultrasonic vibration unit 60, ultrasonic vibrations from the ultrasonic transducer 70 are transmitted to the upper plate 62 of the housing 61 and the matching layer 65, and ultrasonic waves are irradiated (transmitted) toward the water L from the surface of the matching layer 65 on which the unevenness 66 is formed.

[0027] The matching layer 65 is made of a material having an acoustic impedance smaller than that of the upper plate 62 of the housing 61 serving as a diaphragm and larger than that of water L. In this embodiment, the upper plate 62 of the housing 61 is made of SUS (acoustic impedance: 46×10 6 kg / m 2 The matching layer 65 is mainly made of alumina (acoustic impedance: 33×10 6 kg / m 2 s) or glass epoxy (acoustic impedance: 7.1×10 6 kg / m 2The thickness of the layer is about 0.6 mm. The acoustic impedance of water L is 1.5×10 6 kg / m 2 ·s.

[0028] The control unit 57 includes a CPU that performs arithmetic processing according to a control program, and a storage medium such as a memory, etc. The control unit 57 controls the above-mentioned members of the dividing apparatus 50 to perform the dividing step for the wafer 100.

[0029] In a division process using a division apparatus 50 having such a configuration, the wafer 100 is divided along the intended division lines 102 by irradiating the wafer 100 with ultrasonic waves via water L while the wafer 100 and the surface of the matching layer 65 are facing each other.

[0030] 1, the control unit 57 holds the protective tape 107 side of the wafer 100 with the wafer holding member 55 so that the back surface 105 on which the metal film 106 is formed faces downward. Then, the control unit 55 controls the wafer holding member 55 to submerge the wafer 100 in the water L of the water tank 51 and place the wafer 100 facing the front surface of the matching layer 65 of the ultrasonic vibration unit 60 placed on the bottom surface 52 of the water tank 51. At this time, the control unit 57 brings the front surface of the matching layer 65 on which the irregularities 66 are formed and the back surface 105 of the wafer 100 close to each other, for example, by a distance of 1 to 3 mm.

[0031] Next, the control unit 57 applies an AC voltage from the AC power supply 201 to the first electrode 75 and the second electrode 76 (see FIG. 5) of the ultrasonic transducer 70 of the ultrasonic vibration unit 60. This causes ultrasonic vibration to propagate from the tip of the first horn 71 of the ultrasonic transducer 70 to the upper plate 62 of the housing 61. The oscillation frequency of the ultrasonic waves is, for example, 38 kHz.

[0032] As a result, the upper plate 62 and the matching layer 65 are ultrasonically vibrated, and ultrasonic waves W are irradiated from the surface of the matching layer 65 having the unevenness 66 toward the back surface 105 of the wafer 100 on which the metal film 106 is formed, as shown in FIG. 1. As a result, cavitation (the generation and disappearance of minute bubbles) occurs in the water L between the matching layer 65 and the wafer 100 due to the action of the ultrasonic waves W. The impact of this cavitation causes plastic deformation in the metal film 106 of the wafer 100, and the metal film 106 is work-hardened and made embrittled. Furthermore, this impact causes the wafer 100 to be divided along the modified layer formed below the planned division lines 102, and a plurality of device chips including the device 103 are formed.

[0033] This completes the dividing step. Note that, although the dividing step divides the wafer 100 into a plurality of device chips, the wafer 100 is held together by the protective tape 107, preventing the wafer 100 from falling apart.

[0034] As described above, the ultrasonic vibration unit 60 of the dividing device 50 of this embodiment has the upper plate (vibration plate) 62 of the housing 61 to which the ultrasonic vibrator 70 is fixed, and the matching layer 65 laminated on the upper plate 62. Then, ultrasonic waves W from the ultrasonic vibrator 70 are irradiated to the wafer 100 from the surface of the matching layer 65 having the unevenness 66, via the liquid water L. That is, in this configuration, since the ultrasonic waves W are irradiated to the water L and the wafer 100 from the surface of the matching layer 65 having the unevenness 66, it is possible to efficiently generate cavitation (i.e., to increase the frequency of cavitation generation).

[0035] Therefore, in this embodiment, it is possible to efficiently embrittle the metal film 106 in the wafer 100 and divide the wafer 100 along the modified layer. This makes it possible to improve the productivity in manufacturing device chips by dividing the wafer 100 by ultrasonic waves.

[0036] Moreover, in this embodiment, the matching layer 65 is formed of a material having an acoustic impedance smaller than that of the upper plate 62 of the housing 61 and larger than that of the water L. Therefore, the matching layer 65 can reduce the acoustic loss between the upper plate 62 of the housing 61, which is ultrasonically vibrated by the ultrasonic vibrator 70, and the water, which is the liquid to which the ultrasonic waves are to be applied. Therefore, it becomes possible to efficiently irradiate the water L with ultrasonic waves.

[0037] Here, experimental results regarding the effects of the ultrasonic vibration unit 60 according to this embodiment will be shown.

[0038] (1) Cavitation efficiency verification experiment In this experiment, the cavitation efficiency (ease of cavitation occurrence) was compared using an ultrasonic vibration unit 60 with a matching layer 65 having projections and recesses 66 and an ultrasonic vibration unit 160 of a comparative example (see FIG. 7). The ultrasonic vibration unit 160 of the comparative example has a configuration in which the matching layer 65 does not have projections and recesses 66 in the configuration of the ultrasonic vibration unit 60.

[0039] In this experiment, an experimental apparatus 90 as shown in Fig. 7 was used. The experimental apparatus 90 includes a water tank (made of transparent resin) 91 for storing the luminol aqueous solution LS, a support member 92 for supporting the ultrasonic vibration unit 60 (160), and a camera 93.

[0040] 7, the support member 92 supports the ultrasonic vibration unit 60 (160) with the matching layer 65 facing downward, and the ultrasonic vibration unit 60 (160) can be submerged in the luminol aqueous solution LS in the water tank 91. The distance between the lower surface of the ultrasonic vibration unit 60 (160) (the surface of the matching layer 65) and the bottom surface of the water tank 91 is, for example, 5 mm. In addition, the height of the liquid level of the luminol aqueous solution LS during the experiment is, for example, 30 mm.

[0041] The camera 93 is disposed below the water tank 91, and captures light emission by chemiluminescence in the luminol aqueous solution LS below the ultrasonic vibration unit 60 (160) through the bottom surface of the water tank 91. This light emission is due to a chemical reaction between hydrogen peroxide and luminol generated by cavitation, and becomes more intense when the efficiency of cavitation is high.

[0042] The luminol aqueous solution LS is obtained by dissolving luminol and sodium carbonate in water (for example, 1000 mL). The sodium carbonate is added for the purpose of dissolving the luminol in the water. The luminol concentration of the luminol aqueous solution LS is, for example, 0.02% (0.2 g / 1000 mL), and the sodium carbonate concentration is, for example, 0.05% (0.5 g / 1000 mL). The exposure time of the camera 93 is, for example, 120 seconds.

[0043] Fig. 8(a) shows the light emission state by chemiluminescence when the ultrasonic vibration unit 160 of the comparative example is used, as imaged by the camera 93. Fig. 8(b) shows the light emission state by chemiluminescence when the ultrasonic vibration unit 60 of this embodiment is used, as imaged by the camera 93. As shown in these figures, when the ultrasonic vibration unit 60 of this embodiment is used, higher light emission is obtained, and higher cavitation efficiency is realized. Therefore, it can be seen that it is preferable that the matching layer 65 of the ultrasonic vibration unit 60 has unevenness 66.

[0044] (2) Dividability verification experiment In this experiment, the above-mentioned division process was carried out using an ultrasonic vibration unit 60 provided with a matching layer 65 having projections and recesses 66 in a dividing device 50, and an ultrasonic vibration unit 160 of the comparative example described above, and the results of dividing a wafer 100 into multiple chips were compared.

[0045] Fig. 9(a) shows the state of the wafer 100 when ultrasonic waves are irradiated onto the wafer 100 for one minute using an ultrasonic vibration unit 160 of a comparative example having a matching layer 65 without unevenness 66. Fig. 9(b) shows the state of the wafer 100 when ultrasonic waves are irradiated onto the wafer 100 for one minute using an ultrasonic vibration unit 60 of this embodiment having a matching layer 65 with unevenness 66. Note that in these figures, the planned dividing lines 102 and devices 103 of the wafer 100 are not depicted.

[0046] As shown in Fig. 9(a), when the ultrasonic vibration unit 160 of the comparative example is used, the wafer 100 is not substantially divided by ultrasonic irradiation for one minute. On the other hand, as shown in Fig. 9(b), when the ultrasonic vibration unit 60 of the present embodiment is used, even with ultrasonic irradiation for one minute, a crack C is formed in the wafer 100, and it is understood that the wafer 100 begins to be divided.

[0047] 10(a) shows the state of the wafer 100 when ultrasonic waves are irradiated onto the wafer 100 for five minutes using the ultrasonic vibration unit 160 of the comparative example, and FIG 10(b) shows the state of the wafer 100 when ultrasonic waves are irradiated onto the wafer 100 for five minutes using the ultrasonic vibration unit 60 of the present embodiment.

[0048] As shown in Fig. 10(a), in the ultrasonic vibration unit 160 of the comparative example, even when the ultrasonic wave irradiation time was set to 5 minutes, only thin cracks C were observed in the wafer 100. On the other hand, as shown in Fig. 10(b), in the case of using the ultrasonic vibration unit 60 of the present embodiment, when the sound wave irradiation time was set to 5 minutes, many thick cracks C were generated in the wafer 100, and it can be seen that the division of the wafer 100 has progressed significantly.

[0049] In this way, when the ultrasonic vibration unit 60 of this embodiment is used, the division of the wafer 100 proceeds more efficiently, and it can be said that a high cavitation efficiency is realized. Therefore, from this experiment, it is also found that it is preferable that the matching layer 65 of the ultrasonic vibration unit 60 has the unevenness 66.

[0050] In this embodiment, the unevenness 66 formed on the surface of the matching layer 65 is formed by making grooves 661 on the surface of the matching layer 65, as shown in Fig. 1(b). In this regard, the unevenness of the matching layer 65 may be formed by providing a plurality of holes on the surface of the matching layer 65.

[0051] Moreover, the width (or hole diameter) of the grooves 661 in the unevenness 66 is preferably equal to or smaller than the resonant bubble diameter corresponding to the frequency of the ultrasonic waves output from the ultrasonic transducer .

[0052] The relationship between the frequency f0 of the ultrasonic wave and the radius a of the resonant bubble is expressed, for example, by the following formula (1).

[0053]

number

[0054] For example, when the medium is water at 20° C., the medium inside the microbubble is air at 20° C., and the ultrasonic frequency f0 is 38 kHz, the radius a of the microbubble calculated by the above formula (1) is 85 μm. Therefore, it is preferable that the width (or hole diameter) of the grooves 661 in the unevenness 66 is 170 μm or less.

[0055] In addition, it is preferable to select the most suitable material for the upper plate 62 (vibration plate) of the housing 61 in the ultrasonic vibration unit 60 and the matching layer 65 laminated on the upper plate 62 depending on the frequency band, the environment in which it is used, and / or the structure of the ultrasonic transducer 70, etc. An optimal material for the matching layer 65 is, for example, a material that has an acoustic impedance close to the value Z expressed by the following equation (2).

[0056]

number

[0057] FIG. 11 shows the materials of the ultrasonic transducer 70 (transducer), the upper plate 62 (vibration plate) of the housing 61 of the ultrasonic vibration unit 60, the matching layer 65, and the medium according to the frequency band of ultrasonic waves (26 to 160 kHz (low frequency band), 400 to 1000 kHz (high frequency band)). In this figure, the acoustic impedance of each material is shown in parentheses. The unit of acoustic impedance is "10 6 kg / m 2 ·s".

[0058] The material of the ultrasonic transducer 70 is, for example, PZT (lead zirconate titanate). The ultrasonic transducer 70 used in the low frequency band is heavy and the amplitude of the ultrasonic waves it oscillates is large. For this reason, SUS, which has high mechanical strength, is used as the material of the upper plate 62 (vibration plate). In addition, alumina and glass epoxy can be used as the material of the matching layer 65.

[0059] Also, in the high frequency band, the upper plate 62 (diaphragm) can be made of SUS, and the matching layer 65 can be made of alumina and glass epoxy.

[0060] The ultrasonic vibrator 70 used in the high frequency band is light in weight and the amplitude of the ultrasonic waves it oscillates is small. Therefore, a material with low mechanical strength, such as that used for the matching layer 65, can be used as the material for the upper plate 62 (vibration plate). That is, for example, alumina, quartz, or glass epoxy can be used. In this case, the matching layer 65 may not be provided on the upper plate 62 of the ultrasonic vibration unit 60, and the unevenness 66 may be formed on the surface of the upper plate 62. However, from the viewpoint of reducing acoustic loss and suppressing wear of the housing 61, it is preferable that the ultrasonic vibration unit 60 includes the matching layer 65 having the unevenness 66.

[0061] Furthermore, the preferred thickness of the upper plate 62 (vibration plate) is approximately 1 / 2 the wavelength of the ultrasonic waves (wavelength within the upper plate 62). The preferred thickness of the matching layer 65 is approximately 1 / 4 the wavelength of the ultrasonic waves (wavelength within the matching layer 65). However, when the frequency band of the ultrasonic waves is low, a load is generated if the upper plate 62 or matching layer 65 is thick. For this reason, it is preferred that the thickness of each layer is sufficiently thin compared to the wavelength of the ultrasonic waves.

[0062] In addition, in this embodiment, an example is shown in which the ultrasonic vibration unit 60 is applied to a dividing device 50 that performs a dividing step on the wafer 100. In this regard, the ultrasonic vibration unit 60 can also be applied to a cleaning device that cleans an object to be cleaned by cavitation. In this case, for example, the ultrasonic vibration unit 60 and the object to be cleaned are submerged in liquid (such as water) in a water tank, and the object to be cleaned is placed facing the surface of the matching layer 65 of the ultrasonic vibration unit 60. In this state, ultrasonic waves are irradiated from the surface of the matching layer 65 through the liquid to the object to be cleaned, and shock waves generated by cavitation are used to clean the object to be cleaned. [Explanation of symbols]

[0063] 50: dividing device, 51: water tank, 52: bottom surface, 55: wafer holding member, 57: control unit, 60: ultrasonic vibration unit, 61: housing, 62: upper plate, 63: bottom plate, 65: matching layer, 66: unevenness, 70: ultrasonic transducer, 71: first horn, 72: first piezoelectric element, 73: second piezoelectric element, 74: bolt, 75: first electrode, 76: second electrode, 77: second horn, 90: experimental apparatus, 91: water tank, 92: support member, 93: camera, 100: wafer, 101: surface, 102: division line, 103: device, 105: rear surface, 106: metal film, 107: protective tape, 160: ultrasonic vibration unit, 201: AC power source, 661: groove, 662: protrusion, C: crack, L: water, LS: luminol solution, W: ultrasound, a: radius, f0: frequency

Claims

[Claim 1] An ultrasonic vibration unit that irradiates ultrasonic waves to a liquid, An ultrasonic transducer that serves as a source of the ultrasonic waves; a vibration plate having the ultrasonic transducer fixed to a first surface; a matching layer fixed to a second surface of the diaphragm opposite to the first surface, the matching layer being made of a material having an acoustic impedance smaller than that of the diaphragm; The matching layer has an uneven surface on the opposite side to the surface in contact with the diaphragm. An ultrasonic vibration unit characterized by:

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