JP5245064B2 - ULTRASONIC VIBRATION ELEMENT, ITS MANUFACTURING METHOD, AND ULTRASONIC CLEANING DEVICE - Google Patents

Description

  The present invention includes an ultrasonic vibration element that generates ultrasonic vibration, a method of manufacturing the same, and an ultrasonic vibration element. In particular, uniform and precise cleaning of semiconductor wafers, glass masks, glass substrates for liquid crystals, hard disks, and the like can be performed. The present invention relates to a required ultrasonic cleaning apparatus.

  A high-frequency ultrasonic cleaning apparatus is used for precision cleaning of microfabricated products such as semiconductor wafers, glass substrates for liquid crystals, and hard disks. The dirt is particles of less than 1 μm, and the dirt is peeled off by the ultrasonic vibration transmitted through the cleaning liquid filled in the cleaning basket or by the synergistic effect of the cleaning liquid and the ultrasonic vibration.

  FIG. 5 is an explanatory diagram showing a configuration of a general ultrasonic cleaning apparatus. In FIG. 5, 11 is an outer tank, 12 is a quartz tank, 13 is an ultrasonic vibration element, 14 is a high-frequency power source, 15 is pure water, 16 is a cleaning liquid, and 17 is a silicon wafer.

  As shown in FIG. 5, a quartz tank 12 is accommodated in the outer tank 11, pure water 15 is placed in the outer tank 11, and a cleaning liquid 16 such as pure water is contained in the quartz tank 12. Can be put. A silicon wafer 17 as an object to be cleaned is placed in the cleaning liquid 16 in the quartz tank 12. An ultrasonic vibration element 13 is provided at the bottom of the outer tank 11 corresponding to the bottom of the quartz tank 12, and a high frequency power source 14 is connected to the ultrasonic vibration element 13.

  That is, when high frequency power is supplied from the high frequency power supply 14 to the ultrasonic vibration element 13, the ultrasonic vibration element 13 is excited and vibrates ultrasonically. The ultrasonic vibration of the ultrasonic vibration element 13 is transmitted to the cleaning liquid 16 through the bottom of the quartz tank 12. The contamination of the silicon wafer 17 is peeled off by the ultrasonic vibration transmitted into the cleaning liquid 16 or the synergistic effect of the cleaning liquid and the ultrasonic vibration.

  In general, the ultrasonic vibration element 13 has one resonance frequency, and the resonance frequency is supplied from the high frequency power supply 14 so that the vibration efficiency is maximized.

  FIG. 6 is an explanatory diagram for explaining ultrasonic transmission through the bottom surface of a conventional quartz tank. In FIG. 6, 121 is a quartz tank bottom face. As shown in FIG. 6, assuming that the thickness of the quartz tank bottom surface 121 is t, the sound velocity v of the quartz tank bottom surface 121, and the ultrasonic frequency f, the ultrasonic transmission condition of the quartz tank bottom surface 121 is given by the following equation.

t = v / (2 · f) · n
However, n is a natural number.

  FIG. 7 is a characteristic diagram showing the ultrasonic transmission characteristics of the bottom surface of a conventional quartz tank. In FIG. 7, the frequency of ultrasonic vibration is 1 MHz. As shown in FIG. 7, it can be seen that two transmission points appear. Thus, there is a close relationship between the frequency of ultrasonic vibration and the thickness of the plate through which it passes.

8A and 8B are characteristic diagrams showing resonance characteristics of a conventional ultrasonic vibration element. That is, a normal ultrasonic vibration element has a fundamental frequency and a high-order resonance frequency represented by 2n + 1 (n is a natural number) with respect to the fundamental frequency. As an example, FIG. 8A shows the actual resonance point and theoretical resonance point of a nominal 1000 kHz ultrasonic vibration element, and FIG. 8B shows the actual resonance point measurement value and theory of a nominal 2000 kHz ultrasonic vibration element. Resonance point is shown. The horizontal axis represents frequency, the vertical axis represents admittance, and the lower limit position represents the resonance frequency. It can be seen that the resonance frequencies in FIG. 8A are the first order 979 kHz, the second order 2899 kHz, and the third order 4800 kHz. The design value of this ultrasonic vibration element is 975 kHz, and the design resonance frequencies are the first order 975 kHz, the second order 2925 kHz, and the third order 4875 kHz, which are almost the same as the design values including the higher order. The same can be said for the nominal 2000 kHz in FIG.
JP-A-5-291227 Japanese Patent No. 2789178

  Semiconductor cleaning has become increasingly sophisticated and diversified every year, the particle shape of dirt varies in size, the state of adhesion and the particle material, and the precision of the object to be cleaned has increased dramatically. The damage to the cleaning item is remarkable.

  However, it is only output control that the user can control for ultrasonic cleaning at present. In ultrasonic cleaning, there is a frequency as an important factor in addition to the output, and there is a difference in the size of the particle size that can be cleaned at the same output even at high and low frequencies, and the occurrence of damage to fine products.

  Along with the diversification of cleaning in recent years, a cleaning apparatus such as single wafer cleaning of a semiconductor wafer does not necessarily have a quartz tank, and a single frequency according to the thickness of a conventional quartz tank is not necessarily required. .

  That is, in order to improve the convenience of ultrasonic cleaning, it is preferable to provide a frequency control function in addition to the conventional output control.

  As for the oscillation frequency control of the ultrasonic cleaning apparatus, for example, as in Patent Document 2, for the purpose of improving the ultrasonic transmittance of the bottom surface of the quartz tank, there is a technique of frequency modulation about several percent with respect to the fundamental frequency. It is not frequency control aimed at direct control of cleaning power.

  The present invention has been made in view of the above circumstances, and provides an ultrasonic vibration element having a plurality of different thicknesses for generating ultrasonic vibrations of a plurality of different frequencies and a method for manufacturing the same, and the ultrasonic vibration element. By controlling important elements of ultrasonic cleaning power such as ultrasonic vibration output and frequency, direct frequency control of cleaning power is performed to maximize the cleaning effect and diversify the cleaning target. It is an object of the present invention to provide an ultrasonic cleaning apparatus that can be used.

  In order to achieve the above object, an ultrasonic vibration element of the present invention includes a piezoelectric element, an anode and a cathode formed on the piezoelectric element, a groove formed on the piezoelectric element, and another anode formed on the bottom surface of the groove. It is characterized by comprising.

  The ultrasonic cleaning apparatus of the present invention is characterized in that the ultrasonic vibration element has a three-dimensional wiring structure on the vibration element so as to reduce the number of wires for power feeding.

  The method of manufacturing an ultrasonic vibration element according to the present invention includes the steps of forming a first anode and a cathode on the upper surface and the lower surface of the piezoelectric element, forming a groove from the first anode in the piezoelectric element, and the groove Forming a second anode on the bottom surface, inserting an insulator into a part of the groove, and forming an electrode connecting the first anode on the insulator. Features.

  The ultrasonic cleaning apparatus of the present invention includes ultrasonic vibration elements having a plurality of different thicknesses that generate a plurality of ultrasonic vibrations having different frequencies, and provides important elements of ultrasonic cleaning power such as output and frequency of ultrasonic vibrations. By controlling, direct frequency control of the cleaning power can be performed, and the cleaning effect can be controlled to the maximum to cope with the diversification of objects to be cleaned.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1A is a schematic perspective view showing an ultrasonic cleaning apparatus according to an embodiment of the present invention, and FIGS. 1B to 1F are ultrasonic transducers according to the embodiment of the present invention (FIG. 1). It is a schematic perspective view which shows the different example of A part of (a).

  In FIG. 1A, 21 is an outer tub, 22 is an ultrasonic vibration element, and 24 is pure water. As shown in FIG. 1A, a cleaning tank containing a cleaning liquid for cleaning an object to be cleaned is provided in the bottomed rectangular cylindrical outer tank 21. The bottom of the outer tub 21 is provided with a plurality of ultrasonic vibration elements 22 having a plurality of different thicknesses that generate ultrasonic vibrations having a plurality of different frequencies of 500 kHz or more. A high frequency power source is connected to the ultrasonic vibration element 22.

  That is, high frequency power of a plurality of different frequencies is supplied from the high frequency power source to the ultrasonic vibration element 22, and ultrasonic vibrations of a plurality of different frequencies are generated from the ultrasonic vibration element 22. The ultrasonic vibration generated by the ultrasonic vibration element 22 is transmitted to the cleaning liquid in the cleaning tank in the outer tank 21. In the cleaning tank in the outer tank 21, dirt of an object to be cleaned such as a silicon wafer is peeled off by the ultrasonic vibration transmitted in the cleaning liquid or the synergistic effect of the cleaning liquid and the ultrasonic vibration.

  In FIG. 1 (b), as the ultrasonic vibration element 22, elongated protrusions 31 and 32 having different thicknesses are formed by slit processing, and the small areas of the ultrasonic vibration element 22 have different thicknesses. The convex portion 31 generates ultrasonic vibration of the frequency f1 at the thickness L1, and the convex portion 32 generates ultrasonic vibration of the frequency f2 (f2> f1) at the thickness L2 (L2 <L1). That is, the ultrasonic vibration element 22 has a plurality of resonance frequencies of frequencies f1 and f2.

  In FIG. 1C, as the ultrasonic vibration element 22, prismatic convex portions 41 and 42 having different thicknesses are formed by processing, and the small areas of the ultrasonic vibration element 22 have different thicknesses. The convex portion 41 generates ultrasonic vibration of the frequency f1 at the thickness L1, and the convex portion 42 generates ultrasonic vibration of the frequency f2 (f2> f1) at the thickness L2 (L2 <L1).

  In FIG. 1D, as the ultrasonic vibration element 22, a plurality of small prisms 51 and 52 having different heights are gathered together and integrally formed, and the small areas of the ultrasonic vibration element 22 have different thicknesses. The rectangular column 51 generates ultrasonic vibration of the frequency f1 at the thickness L1, and the rectangular column 52 generates ultrasonic vibration of the frequency f2 (f2> f1) at the thickness L2 (L2 <L1).

  In FIG. 1E, the ultrasonic vibration element 22 is formed by integrating a plurality of small cylinders 61 and 62 having different heights so that the small areas of the ultrasonic vibration element 22 have different thicknesses. The cylinder 61 generates ultrasonic vibration of the frequency f1 at the thickness L1, and the cylinder 62 generates ultrasonic vibration of the frequency f2 (f2> f1) at the thickness L2 (L2 <L1).

  In FIG. 1 (f), a plurality of small circular holes 71 are formed as the ultrasonic vibration element 22, and different thicknesses are given to the small areas of the ultrasonic vibration element 22. An ultrasonic vibration having a frequency f1 is generated in a portion having a thickness L1 formed by the portion 71 having no circular hole, and a frequency f2 (f2) is formed in a portion having a thickness L2 (L2 <L1) formed in the bottom portion of the circular hole 72. The ultrasonic vibration of> f1) is generated.

  That is, in order to cause the ultrasonic vibration element 22 to oscillate various frequencies, the ultrasonic vibration element 22 needs to have a plurality of resonance frequencies corresponding thereto. The basic resonance frequency of the ultrasonic vibration element 22 is determined according to the thickness of the ultrasonic vibration element 22. Therefore, a plurality of different resonance frequencies can be obtained by providing different thicknesses for each small region of the ultrasonic vibration element 22. Since the resonance frequency and the thickness of the ultrasonic vibration element 22 are inversely proportional to each other, if the thickness of the ultrasonic vibration element 22 is halved, the frequency is doubled.

  The thickness of the ultrasonic vibration element 22 is not limited to two types, and may be three or more types according to a desired frequency. In this case, ultrasonic vibrations having three or more types of frequencies are generated. be able to.

  Embodiments of the present invention can provide a relatively inexpensive, high-performance, and highly efficient ultrasonic cleaning apparatus. Regarding the oscillation frequency control of the ultrasonic cleaning apparatus, it is a frequency control for the purpose of direct control of the cleaning power, and the cleaning effect can be controlled to the maximum by changing it by 25% or more of the fundamental frequency.

  FIG. 3 is a characteristic diagram showing the cleaning effect of the ultrasonic cleaning apparatus according to the embodiment of the present invention. That is, in ultrasonic cleaning, ultrasonic waves are oscillated in water, and the dirt adhering to the object to be cleaned is peeled off by the energy of cavitation shock waves generated at that time, and at the same time, causes cleaning damage. The occurrence of cavitation tends to become weaker as the frequency becomes higher and weaker as the ultrasonic output becomes lower. As shown in FIG. 3, the frequency and output are maintained at the optimum values for the object to be cleaned. And good cleaning.

  FIG. 2A is a schematic perspective view showing an ultrasonic cleaning apparatus according to the embodiment of the present invention, and FIGS. 2B and 2C show wiring of the ultrasonic vibrator according to the embodiment of the present invention. FIG. 2 (a) to 2 (c), the same parts as those in FIGS. 1 (a) and 1 (b) are denoted by the same reference numerals, and the description thereof is omitted. 2A is the same as FIG. 1A, and FIG. 2B corresponds to FIG. 1B.

  As shown in FIG. 2B, the upper surface of the ultrasonic vibration element 22 is a cathode (common electrode) M, and the apex of the convex portion 31 is a first anode P1 (which generates ultrasonic vibration of frequency f1). In addition to wiring in common, the vertexes of the protrusions 32 are collectively wired as the second anode P2 (which generates ultrasonic vibration of frequency f2).

  In this case, the cathode M on the upper surface of the ultrasonic vibration element 22, the first anode P1 in which the vertices of the convex portions 31 are wired in common, and the second anode P2 in which the vertices of the convex portions 32 are collectively wired in common. Conductive plating may be applied.

  As shown in FIG. 2C, the first anode P1 and the second anode P2, which are commonly wired together, are wired in parallel and connected to the high frequency power supply 25 to form a power supply line for one frequency system.

  That is, when the high-frequency power of frequency f1 and the high-frequency power of frequency f2 are alternately output from the high-frequency power supply 25 and supplied to the first anode P1 and the second anode P2, the ultrasonic vibration element 22 has a high frequency power of the frequency f1. Ultrasonic vibration of frequency f1 is generated in a portion corresponding to the convex portion 31, and ultrasonic vibration of frequency f2 is generated in a portion corresponding to the convex portion 32 of the ultrasonic vibration element 22 with high frequency power of frequency f2.

  Incidentally, in order to drive an ultrasonic vibration element having a plurality of resonance frequencies, it is usual to perform separate wiring for each resonance frequency. In this case, there are merits such as simultaneous irradiation of ultrasonic vibrations of different frequencies. However, in that case, the wiring becomes enormous, resulting in a demerit such as a rise in product price, difficulty in routing the wiring, and incorrect wiring. In order to improve this, for example, a vibrating element as shown in FIG. 1 can be provided with a three-dimensional wiring structure to reduce wiring routing. An example of this manufacturing method will be described next.

  A normal vibration element having one resonance frequency has an electrode structure as shown in FIG. That is, an anode P made of a conductive film is provided on the upper surface of a plate-like piezoelectric element 81 such as ceramic, leaving a part of the upper surface, and a cathode M made of a conductive film is formed on the lower surface of the piezoelectric element 81. A part is provided continuously. A gap 82 is provided between the anode P and the cathode M. Next, as shown in FIG. 9B, a plurality of grooves 83 are provided in the longitudinal direction on the upper surface of the piezoelectric element 81 by machining, and grooves 84 are provided in the gap 82 by machining. In this case, an element having the frequency f1 is formed in the portion of the anode P, and an element having the frequency f2 is formed in the portion of the groove 83 between the anodes P. Next, as shown in FIG. 9C, an insulator 85 such as resin or ceramic is inserted between the cathodes M of the grooves 83. Next, as shown in FIG. 9D, an electrode 86 made of a conductive film is manufactured at the bottom of the groove 83 and the groove 84. Next, as shown in FIG. 9E, an insulator 87 such as resin or ceramic is inserted into a part between the anodes P of the groove 83. Next, as shown in FIG. 9 (f), an electrode 88 is continuously formed on the surface of the insulator 85 corresponding to the cathode M, and the surface of the insulator 87 corresponding to the anode P. The electrode 89 is formed continuously with the anode P. The anode P and the electrode 89 form the anode P1, the electrode 86 forms the anode P2, and the cathode M and the electrode 88 form the cathode M. As a result, the three wires of the cathode M, the first anode P1, and the second anode P2 are sufficient.

  As another method, since the ultrasonic vibration element uses a resonance principle, the ultrasonic vibration element does not vibrate even when high frequency power having a frequency that does not resonate is applied. In other words, all the frequency system wirings are combined into parallel wiring, and the high frequency power corresponding to each resonance frequency is switched and sequentially output from the high frequency power supply device, so that the maximum desired frequency can be exceeded with minimum wiring. Sound wave vibration can be obtained.

  FIG. 4 is a characteristic diagram showing resonance characteristics of the ultrasonic vibration element according to the embodiment of the present invention. In FIG. 4, an ultrasonic vibration element having two thicknesses of 1000 kHz and 2000 kHz as shown in FIG. 1B is manufactured, and the resonance characteristics of the ultrasonic vibration element and the theoretical values are obtained as resonance characteristics. Resonance point is shown. The horizontal axis represents frequency, the vertical axis represents admittance, and the lower limit position represents the resonance frequency. In the design, resonance frequencies should appear as 975 kHz, 1950 kHz, 2925 kHz, 4875 kHz, etc., and as shown in FIG. It was confirmed that the ultrasonic vibration element can oscillate at 1891 kHz.

  From this, it is possible to realize an ultrasonic cleaning device capable of finely controlling the frequency by manufacturing an ultrasonic vibration element that is changed in units of 100 kHz, for example, without being limited to frequencies that are considerably separated from 1000 kHz and 2000 kHz.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

(A) is a schematic perspective view which shows the ultrasonic cleaning apparatus which concerns on embodiment of this invention, (b)-(f) is an ultrasonic transducer | vibrator (FIG. 1 (a)) of embodiment of this invention. It is a schematic perspective view which shows the example from which A part) differs. BRIEF DESCRIPTION OF THE DRAWINGS (a) is a schematic perspective view which shows the ultrasonic cleaning apparatus concerning embodiment of this invention, (b), (c) is structure explanatory drawing which shows the wiring of the ultrasonic vibration element concerning embodiment of this invention. It is. It is a characteristic view which shows the cleaning effect of the ultrasonic cleaning apparatus which concerns on embodiment of this invention. It is a characteristic view which shows the resonance characteristic of the ultrasonic vibration element which concerns on embodiment of this invention. It is composition explanatory drawing which shows a general ultrasonic cleaning apparatus. It is explanatory drawing explaining the ultrasonic transmission of the conventional quartz tank bottom face. It is a characteristic view which shows the ultrasonic transmission characteristic of the conventional quartz tank bottom face. (A), (b) is a characteristic view which shows the resonance characteristic of the conventional ultrasonic vibration element. (A)-(f) is process drawing which shows the manufacturing method of the ultrasonic vibration element which concerns on embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 21 ... Outer tank, 22 ... Ultrasonic vibration element, 24 ... Pure water, 25 ... High frequency power supply, 31, 32 ... Convex part, 41, 42 ... Convex part 51, 52 ... Conical pillar, 61, 62 ... Cylinder, 71 72 ... Circular holes.

Claims (3)

A piezoelectric element having two opposing surfaces;
A first electrode formed on one surface of the piezoelectric element;
A second electrode having a polarity different from that of the first electrode, formed on the other surface of the piezoelectric element;
A groove formed on one surface of the piezoelectric element;
A third electrode having the same polarity as the first electrode, formed in the groove;
An ultrasonic vibration element comprising: The ultrasonic vibration element according to claim 1;
A cleaning tank to which ultrasonic waves are transmitted from the ultrasonic vibration element;
An ultrasonic cleaning apparatus comprising: Forming a first anode and a cathode on the upper and lower surfaces of the piezoelectric element;
Forming a groove in the piezoelectric element from a first anode;
Forming a second anode on the bottom of the groove;
Inserting an insulator into a portion of the groove;
Forming an electrode for connecting the first anode on the insulator.

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