JP2011066590A - Lamb wave device, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a Lamb wave device capable of achieving a Lamb wave of high frequency by reducing thickness of a piezoelectric substrate. <P>SOLUTION: A Lamb wave resonator 1 being a Lamb wave device has: a crystal substrate 2; a comb-shaped electrode 3 made of aluminum (Al) on one surface of the crystal substrate 2; reflectors 4; electrode pads 5; a metal film 6 made of gold (Au) on the other surface of the crystal substrate 2; support substrates 7 being a silicon substrate joined to the metal film 6; and a cavity 8 which is located opposite to the comb-shaped electrode 3, the reflectors 4 and the electrode pads 5 through the crystal substrate 2 and the metal film 6 which are formed on the support substrates 7. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a Lamb wave type device using Lamb waves propagating inside a piezoelectric substrate and a method for manufacturing the Lamb wave type device.

  Conventionally, Lamb waves that are repeatedly reflected between the front and back surfaces of a piezoelectric substrate and propagate in the piezoelectric substrate are efficiently excited when the thickness H of the piezoelectric substrate is 5 wavelengths or less of the Lamb wave wavelength λ. It has been known. More specifically, the Lamb wave can be excited efficiently when the condition of 0 <(2H / λ) ≦ 10 is satisfied. That is, it is possible to excite a high-frequency Lamb wave by reducing the thickness H of the piezoelectric substrate as much as possible in accordance with the Lamb wave wavelength λ (for example, Patent Document 1).

JP 2003-258596 A

  However, the conventional technique has a problem that the impact resistance of the piezoelectric substrate is reduced as the thickness H of the piezoelectric substrate is reduced in order to increase the frequency of the Lamb wave. For this reason, in the manufacturing process, since it is necessary to meticulously process so as not to give an impact or the like, a decrease in manufacturing efficiency, a decrease in yield due to difficulty in making the piezoelectric substrate uniform, etc. occur. There was a problem.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following application examples or forms.

  Application Example 1 A Lamb wave device according to this application example is for exciting a Lamb wave, and includes a piezoelectric substrate, an excitation electrode formed on one surface of the piezoelectric substrate, and the piezoelectric substrate. A holding film formed on the other surface of the substrate, a support substrate bonded to the holding film, and a cavity provided on the support substrate and opposed to the excitation electrode through the piezoelectric substrate and the holding film And a portion.

  According to this Lamb wave type device, the piezoelectric substrate has the holding film and the support substrate on the surface opposite to the surface on which the excitation electrode is formed, and the support substrate has a cavity portion facing the excitation electrode. The recessed part which is is provided. That is, even if the piezoelectric substrate of the Lamb wave type device is a thin plate, the reduction in impact resistance is suppressed by the holding film and the support substrate provided in a portion other than the cavity portion. ing. Here, since the Lamb wave excited by the excitation electrode propagates repeatedly inside the piezoelectric substrate on the front and back surfaces, in order to efficiently excite the high frequency Lamb wave, the thickness of the piezoelectric substrate is made as thin as possible. And a uniform thickness. Correspondingly, the Lamb wave type device has a configuration in which the impact resistance of the thinned piezoelectric substrate is maintained without being lowered by the support substrate. In addition, the Lamb wave type device has a structure in which the holding film substantially prevents the impact resistance of the piezoelectric substrate from being lowered even in the piezoelectric substrate located in the cavity portion that is not supported by the support substrate. The thickness of the piezoelectric substrate positioned in the part can also be set thinner than in the case where there is no holding film. In other words, the Lamb wave type device has a thin piezoelectric substrate corresponding to the high frequency of the Lamb wave, and it is possible to efficiently and reliably excite the high frequency Lamb wave by the excitation electrode facing the cavity portion. is there.

  Application Example 2 In the Lamb wave device according to the application example, it is preferable that the holding film is a metal film.

  According to this configuration, the Lamb wave type device forms the metal film as the holding film. That is, if it is a metal film, a holding film with high impact resistance can be formed without increasing the film thickness, and even if the piezoelectric substrate is made thin, it is possible to suppress the decrease in impact resistance. In addition, the Lamb wave type device has the effect of increasing the electromechanical coupling coefficient, which is a value indicating the efficiency in converting electrical vibration into mechanical vibration using the piezoelectric effect of the piezoelectric substrate by forming a metal film. In addition, high-frequency Lamb waves can be excited more efficiently.

  Application Example 3 In the Lamb wave type device according to the application example, the support substrate is any one of silicon, crystal, lithium tantalate, lithium niobate, zinc oxide, aluminum nitride, potassium niobate, and glass. Is preferred.

  According to this configuration, these materials can be bonded to the holding film by eutectic bonding, anodic bonding, diffusion bonding, etc., and the cavity portion can be easily processed by a method such as etching. As well as strength. Thereby, it is possible to select an appropriate support substrate corresponding to the holding film.

  Application Example 4 In the Lamb wave device according to the application example described above, it is preferable that the area of the cavity portion facing the excitation electrode is equal to or larger than the area of the excitation electrode.

  According to this configuration, the excitation electrode region formed on one surface of the piezoelectric substrate is not opposed to the support substrate because the cavity portion is formed on the other surface of the piezoelectric substrate, and is held. Opposite the membrane only. As a result, the Lamb wave type device is not affected by the support substrate because the Lamb wave propagating inside the piezoelectric substrate is excited by the thin plate portion of the piezoelectric substrate located in the cavity, and the Lamb wave propagation speed Variation is less likely to occur. That is, the Lamb wave type device can excite high-frequency Lamb waves more reliably by utilizing the piezoelectric effect of the piezoelectric substrate to the maximum extent.

  Application Example 5 In the Lamb wave type device according to the application example described above, it is preferable that the excitation electrode is a comb-like electrode and has reflectors on both sides of the comb-like electrode.

  According to this configuration, the Lamb wave type device can easily set the wavelength of the Lamb wave by the width of the comb teeth portion and the arrangement pitch of the comb teeth electrode. That is, it is possible to easily excite Lamb waves having a wavelength corresponding to the piezoelectric substrate. Furthermore, this Lamb wave type device has a reflector, and the reflector reflects and resonates the Lamb wave excited by the comb-like electrode. Thereby, the Lamb wave type device can resonate a high frequency Lamb wave.

  Application Example 6 A method for manufacturing a Lamb wave device according to this application example relates to a Lamb wave device for exciting Lamb waves, a film forming step of forming a holding film on one surface of a piezoelectric substrate, A bonding step of bonding a support substrate to the holding film, a thinning step of thinning the piezoelectric substrate, an electrode forming step of forming an excitation electrode on the surface of the piezoelectric substrate, and the piezoelectric substrate and the holding film And a cavity part installation step of providing a cavity part positioned opposite to the excitation electrode on the support substrate.

  According to this method of manufacturing a Lamb wave device, first, a holding film by a film forming step and a support substrate by a bonding step are formed on the piezoelectric substrate, and the process proceeds to a thinning step. In the thinning step, the piezoelectric substrate is processed in a state where it is reinforced by the holding film and the support substrate. Therefore, even if the piezoelectric substrate is processed into a predetermined thin plate, the thickness becomes uneven during the processing. It is also possible to prevent the occurrence of defects such as cracks and chips. The formation of the excitation electrode in the next electrode formation step and the installation of the cavity portion in the cavity portion installation step can also perform stable processing by preventing the occurrence of defects in the piezoelectric substrate. By such a manufacturing method, the piezoelectric substrate of the Lamb wave device has a holding film and a support substrate on the surface opposite to the surface on which the excitation electrode is formed, and the support substrate faces the excitation electrode. The cavity is provided with a recess. That is, even if the thickness of the piezoelectric substrate is thin, a decrease in impact resistance is suppressed by the holding film and the support substrate. Here, since the Lamb wave excited by the excitation electrode propagates repeatedly inside the piezoelectric substrate on the front and back surfaces, in order to efficiently excite the high frequency Lamb wave, the thickness of the piezoelectric substrate is made as thin as possible. And a uniform thickness. Correspondingly, the Lamb wave type device has a configuration in which the piezoelectric substrate is reinforced by the holding film in the portion where the excitation electrode is located. That is, since the holding film suppresses the decrease in impact resistance of the piezoelectric substrate, the thickness of the piezoelectric substrate can be reduced as compared with the case where there is no holding film. A Lamb wave type device by such a manufacturing method has a thin piezoelectric substrate corresponding to the high frequency of Lamb waves, and excites high frequency Lamb waves efficiently and reliably by an excitation electrode located in the cavity portion. It is possible.

  Application Example 7 In the method for manufacturing a Lamb wave device according to the application example, the holding film formed in the film forming step is a metal film, and the cavity part formed in the cavity part installation step is It is preferable that the area facing the excitation electrode has an area equal to or larger than the area of the excitation electrode.

  According to this method, if the holding film formed in the film forming step is a metal film, a holding film having high impact resistance can be formed without increasing the film thickness. It is possible to suppress a decrease in impact properties. In addition, by forming this metal film, the Lamb wave type device also has the effect of increasing the electromechanical coupling coefficient, which is a value indicating the efficiency in converting electrical vibration into mechanical vibration using the piezoelectric effect of the piezoelectric substrate. And high-frequency Lamb waves can be excited more efficiently. Further, due to the cavity portion formed in the cavity portion installation step, the region of the excitation electrode does not face the support substrate on the holding film side of the piezoelectric substrate but faces only the holding film. As a result, the Lamb wave type device is excited by the portion of the piezoelectric substrate where the Lamb wave is not restrained by the support substrate, so that the Lamb wave propagation speed does not easily vary. That is, the Lamb wave type device can excite high-frequency Lamb waves more reliably by utilizing the piezoelectric effect of the piezoelectric substrate to the maximum extent.

The top view which shows the structure of the Lamb wave type | mold resonator which concerns on this embodiment. Sectional drawing which shows the structure of a Lamb wave type | mold resonator. The flowchart which shows the manufacturing method of a Lamb wave type | mold resonator. (A) Cross-sectional view showing film forming step, (b) Cross-sectional view showing joining step, (c) Cross-sectional view showing thinning step. (D) Sectional drawing which shows an electrode formation step, (e) Sectional drawing which shows a cavity part installation step. The top view which shows the structure of the modification of a Lamb wave type | mold resonator.

Hereinafter, an embodiment of a Lamb wave type device and a manufacturing method thereof will be described with reference to the drawings. In this case, the Lamb wave type device is characterized in that the thickness of a piezoelectric material such as quartz can be made thinner than before, and in this embodiment, a Lamb wave type resonator is shown as a specific example. In the drawings, the scale and the like of each part are appropriately changed for easy understanding.
(Embodiment)

  FIG. 1 is a plan view showing a configuration of a Lamb wave type resonator according to this embodiment, and FIG. 2 is a cross-sectional view showing a configuration of the Lamb wave type resonator. FIG. 2 shows a cross section taken along line AA ′ shown in FIG. First, as shown in FIG. 1, a Lamb wave type resonator (Lamb wave type device) 1 includes a quartz crystal substrate 2 which is a piezoelectric substrate having a rectangular shape, and almost one surface (one surface) of the quartz crystal substrate 2. A comb-like electrode (excitation electrode) 3 formed at the center, reflectors 4 formed on both sides of the comb-like electrode 3, and extending from the comb-like electrode 3 to the comb-like electrode 3 And an electrode pad 5 for applying a driving voltage.

  The comb-like electrode 3 includes a first electrode 31 having a plurality of comb-like electrode fingers 31a and a second electrode 32 having a plurality of comb-like electrode fingers 32a. Has been. The electrode fingers 31a are each formed with a pitch P of 3 μm, and the electrode fingers 32a are similarly formed with a pitch P of 3 μm. In addition, the electrode fingers 31a and the electrode fingers 32a are arranged so that each one is alternately inserted. The lamb wave resonator 1 is connected to the first electrode 31 and extends to one corner along one side of the quartz substrate 2. The lamb wave resonator 1 is connected to the second electrode 32 and is connected to the quartz substrate 2. 5a and an electrode pad 5b extending to the corner of the diagonal position. Further, the lamb wave resonator 1 includes a reflector 4a formed on one side in the direction in which the electrode fingers 31a and the electrode fingers 32a are alternately arranged with respect to the comb-like electrode 3, and the other side. And the reflector 4b formed in the above. The reflector 4a and the reflector 4b each have a plurality of fingers similar to the electrode fingers 31a and 32ab in a parallel arrangement with the electrode fingers 31a and 32a. The comb-like electrode 3, the reflector 4, and the electrode pad 5 are formed by vapor-depositing aluminum (Al).

  Next, as shown in FIG. 2, the other surface of the quartz substrate 2 on which the comb-like electrodes 3 and the like are formed on one surface is disposed between the metal film 6 as a holding film and the quartz substrate 2. And a support substrate 7 that supports the Lamb wave resonator 1 with the metal film 6 interposed therebetween. The metal film 6 is a chemically stable gold (Au) film, and has a thickness J of 0.1 μm formed by sputtering, and has an impact resistance due to the thinning of the quartz substrate 2. It plays a role in suppressing the decline. In the Lamb wave resonator 1, the quartz substrate 2 is a so-called AT-cut quartz, and the thickness H is reduced to 15 μm. The support substrate 7 is a silicon (Si) substrate that is eutectic bonded to the gold (Au) of the metal film 6 and has a wider area than the regions of the comb-like electrode 3 and the reflector 4. Part 8 is formed. The cavity portion 8 is formed by etching silicon (Si) of the support substrate 7, and is positioned to face the comb-like electrode 3 and the reflector 4 with the crystal substrate 2 and the metal film 6 interposed therebetween. . That is, only the metal film 6 is formed on the other surface side of the quartz crystal substrate 2 at the position where the comb-like electrode 3 and the reflector 4 are formed.

  When the driving voltage is applied to the electrode pad 5, the lamb wave resonator 1 having such a configuration is configured such that one surface and the other surface of the quartz substrate 2 are formed by the comb-like electrode 3 in the AT-cut quartz substrate 2. Lamb waves that repeatedly propagate and propagate are excited. Since the excited Lamb wave has a higher phase velocity than a surface acoustic wave or the like, it has a feature that its frequency can be increased. The Lamb wave has a wavelength λ corresponding to the pitch P of the electrode fingers 31a and 32a, propagates in the direction of the reflectors 4a and 4b, and is reflected by the reflector 4. Here, as is known, the thickness H of the quartz substrate 2 is a value of 5 wavelengths or less of the wavelength λ of the Lamb wave from the relationship of (2H / λ ≦ 10, that is, H / λ ≦ 5). It has been found that it excites efficiently. When (H / λ) in the Lamb wave resonator 1 is calculated, 15/3 = 5, which satisfies this condition. Therefore, the Lamb wave resonator 1 is capable of generating a high frequency signal stably because the Lamb wave is efficiently excited by the comb-like electrode 3 and resonates by reflection by the reflector 4.

  In addition, it has been found that the lamb wave resonator 1 has an effect of increasing the electromechanical coupling coefficient by forming the metal film 6. The electromechanical coupling coefficient is a value indicating the efficiency in converting electrical vibration into mechanical vibration using the piezoelectric effect of a piezoelectric substrate such as a quartz substrate, and is a coefficient proportional to the excitation efficiency of Lamb waves or the like. is there. Due to the increase effect of the electromechanical coupling coefficient, the Lamb wave resonator 1 can excite high-frequency Lamb waves more efficiently. The Lamb wave resonator 1 can also control the frequency by using the capacitance between the metal film 6 and the electrode pad 5. That is, the capacitance can be changed by changing the area of the electrode pad 5. For example, if the capacitance is increased, the frequency can be made more stable.

  Next, a method for manufacturing the Lamb wave resonator 1 will be described. FIG. 3 is a flowchart showing a method for manufacturing a Lamb wave resonator. First, in step S <b> 1, an Au film that is a metal film (holding film) 6 is formed on the quartz substrate 2. This step S1 corresponds to a film forming step, and FIG. 4A is a cross-sectional view showing the film forming step. As shown in FIG. 4A, the Au film is formed on the one surface (the other surface) of the quartz substrate 2 by sputtering to have a thickness J of 0.1 μm. The Au film is a chemically stable material, hardly affected by heat or chemical treatment in post-processing, and hardly causes deterioration such as corrosion in the long term. In addition, the Au film is the metal film 6 and has the effect of complementing the strength of the quartz crystal substrate 2 and suppressing the reduction in impact resistance. After forming the Au film, the process proceeds to step S2.

  In step S2, the crystal substrate 2 and the support substrate 7 are bonded. This step S2 corresponds to the joining step, and FIG. 4B is a cross-sectional view showing the joining step. As shown in FIG. 4B, the support substrate 7 is bonded to the Au film so that the metal film 6 of the Au film is sandwiched between the support substrate 7 and the crystal substrate 2. The support substrate 7 is a silicon plate and is bonded to the Au film by eutectic bonding. The eutectic point, which is the temperature at which silicon (Si) and gold (Au) are eutectic bonded, is 363 ° C., and the support substrate 7 and the Au film of the metal film 6 are bonded by heat treatment at a temperature higher than this temperature. Eutectic bonded silicon (Si) and gold (Au) have high mechanical strength and are difficult to peel off. Therefore, the support substrate 7 can substantially suppress a decrease in impact resistance of the crystal substrate 2 by supporting the crystal substrate 2 via the Au film. After joining the support substrate 7, the process proceeds to step S3.

  In step S3, the quartz substrate 2 is thinned. Step S3 corresponds to the thinning step, and FIG. 4C is a cross-sectional view showing the thinning step. As shown in FIG. 4 (c), in the quartz substrate 2, the surface opposite to the surface on which the metal film 6 and the support substrate 7 are provided (one surface) is polished, and a thin plate having a thickness H of 15 μm To. The polishing process is performed by wet polishing in which the crystal substrate 2 is ground with a grindstone while supplying a polishing liquid. In the polishing process, since the quartz substrate 2 is supported by the metal film 6 and the support substrate 7, the quartz substrate 2 is hardly cracked or chipped due to processing stress, and the quartz substrate 2 is more reliably thinned. be able to. Further, when the quartz substrate 2 is made thin, deformation such as substrate bending does not occur, so that the quartz substrate 2 can be processed to a uniform thickness H. The thin plate processing of the quartz substrate 2 can be performed by dry polishing, dry etching, wet etching, or a combination of these in addition to wet polishing. After processing the thin plate of the quartz substrate 2, the process proceeds to step S4.

  In step S <b> 4, the comb-like electrode 3, the reflector 4 and the electrode pad 5 are formed on the crystal substrate 2. This step S4 corresponds to an electrode forming step, and FIG. 5D is a cross-sectional view showing the electrode forming step. As shown in FIG. 5D, the comb-like electrode 3, the reflector 4 and the electrode pad 5 are formed on the surface of the quartz crystal substrate 2 polished in step S3 by photolithography. Specifically, first, aluminum (Al) is vapor-deposited on the entire surface of the polished quartz crystal substrate 2. Next, a resist is applied and exposed so as to cover the entire surface of the deposited aluminum (Al). For example, the resist is applied by applying a negative resist agent to the entire surface of aluminum (Al) by spin coating and baking in an oven furnace. In the exposure, a glass mask is set so as to cover the negative resist agent, and the negative resist is exposed to ultraviolet rays. The glass mask has a transmissive portion disposed in the portions of the comb-like electrode 3, the reflector 4, and the electrode pad 5, and a light shielding portion other than the transmissive portion. UV rays are blocked. In the negative resist agent, the portion facing the transmissive portion exposed to ultraviolet rays is cured. Next, when the resist is developed with a developing solution, the portion cured by exposure to ultraviolet rays is not dissolved by development, but the portion not exposed to ultraviolet rays is dissolved by development. Therefore, after development, the resist remains only in the portion where the comb-like electrode 3, the reflector 4 and the electrode pad 5 are formed.

  Then, aluminum (Al) in a portion where the resist is not formed is removed by etching. In the portion where the resist is formed, aluminum (Al) remains in a convex shape without being removed by etching. By such etching, the comb-like electrode 3, the reflector 4 and the electrode pad 5 covered with the resist can be formed. After this etching, the remaining resist covering the comb-like electrode 3, the reflector 4, and the electrode pad 5 is removed. Thus, the comb-like electrode 3, the reflector 4, and the electrode pad 5 are formed. After forming the comb-like electrode 3, the reflector 4, and the electrode pad 5, the process proceeds to step S5.

  In step S <b> 5, the cavity portion 8 is installed on the support substrate 7. This step S5 corresponds to a cavity part installation step, and FIG. 5E is a cross-sectional view showing the cavity part installation step. As shown in FIG. 5 (e), the cavity portion 8 is disposed at a position facing the comb-like electrode 3 and the reflector 4 through the quartz crystal substrate 2 and the metal film 6. In plan view, as shown in FIG. 1, the area of the cavity portion 8 has a larger area than the area where the comb-like electrode 3 and the reflector 4 are formed. The cavity portion 8 is formed by etching silicon (Si) of the support substrate 7 with potassium hydroxide (KOH). In the etching process, first, a portion other than the cavity portion 8 is covered with a resist including the comb-like electrode 3, the reflector 4 and the electrode pad 5. That is, the portion not covered with the resist exists on the surface of the support substrate 7 opposite to the surface bonded to the Au film. Then, when the silicon (Si) is removed by etching until the Au film is reached, a concave portion is formed on the support substrate 7. Finally, if the resist is removed, the concave portion is set as the cavity portion 8 on the support substrate 7. Thus, the Lamb wave type resonator 1 is completed and the flow ends.

  Hereinafter, effects of the Lamb wave resonator 1 and the manufacturing method thereof in the embodiment will be described together.

  (1) Since the Lamb wave type resonator 1 has a configuration in which the crystal substrate 2 is reinforced by the metal film 6 and the support substrate 7, in the thinning step when the crystal substrate 2 is processed into a predetermined thin plate, It is possible to prevent the occurrence of defects such as cracks and chips. Thereby, the Lamb wave type resonator 1 can have the quartz substrate 2 of the uniform thickness H, and can excite a high frequency Lamb wave.

  (2) Since the lamb wave resonator 1 has the cavity portion 8, the comb-like electrode 3 and the reflector 4 are not opposed to the support substrate 7 through the quartz substrate 2. It faces only the metal film 6. That is, the area of the cavity portion 8 has an area equal to or larger than the areas of the comb-like electrode 3 and the reflector 4. Thereby, the Lamb wave type resonator 1 is excited in the thin plate portion of the quartz substrate 2 located in the cavity portion 8 where the Lamb wave propagating inside the quartz substrate 2 is not restrained by the support substrate 7. Variations in the propagation speed of Lamb waves are less likely to occur, and stable high-frequency Lamb waves can be excited more reliably.

  (3) In the lamb wave resonator 1, since the metal film 6 is configured to suppress a decrease in impact resistance of the quartz substrate 2 in the cavity portion 8, the quartz substrate 2 can be made thinner. it can. The Lamb wave type resonator 1 also has an effect of increasing the electromechanical coupling coefficient by forming the metal film 6, and can excite a high frequency Lamb wave more efficiently.

  (4) Use of a metal film 6 of Au film that is chemically stable and hardly affected by heat or chemical treatment in post-processing as the holding film, and gold (Au) and mechanical strength as the support substrate 7 By using silicon (Si) having a high eutectic bond, the quartz crystal substrate 2 is stably supported over a long period of time including the manufacturing process, and can maintain high reliability.

  (5) The Lamb wave resonator 1 includes the metal film 6 not only in the cavity portion 8 but also between the support substrate 7 and the crystal substrate 2, so that static electricity between the metal film 6 and the electrode pad 5 can be obtained. Capacitance can be used, and control such as changing the capacitance by changing the area of the electrode pad 5 to stabilize the frequency can be performed.

  (6) The quartz substrate 2 has a thickness H of about 100 μm, which is the limit of thinning, in order to ensure both impact resistance and uniform thickness H in the quartz alone. On the other hand, by providing the metal film 6 and the support substrate 7, the crystal substrate 2 having a thickness of 15 μm in the present embodiment is obtained, and further knowledge that a thickness of 3 μm is possible is obtained.

  The Lamb wave type device and the Lamb wave type device manufacturing method are not limited to the above embodiment, and the same effects as in the embodiment can be obtained even in the following modifications. It is done.

  (Modification 1) Although the support substrate 7 uses silicon (Si), it is not limited to silicon (Si), but glass, crystal, lithium tantalate, lithium niobate, zinc oxide, aluminum nitride, and niobium Potassium acid may be used. The holding film is not limited to the Au film, and may be titanium (Ti), chromium (Cr), nickel (Ni), or the like. As the holding film, these metal films 6 are more preferable, but metals other than metals may be used. Further, although quartz is used for the piezoelectric substrate, lithium tantalate, lithium niobate, zinc oxide, aluminum nitride, and potassium niobate may be used. As a result, a holding film and a supporting substrate 7 suitable for the piezoelectric substrate can be selected widely, and the bonding method between the holding film and the supporting substrate 7 also uses anodic bonding by ion transfer or atomic diffusion in addition to eutectic bonding. A method suitable for the holding film and the support substrate 7 can be utilized, such as diffusion bonding.

  (Modification 2) In the film formation step of step S1, the Au film is formed on the entire surface of the quartz substrate 2, but the Au film may be formed only in the region where the cavity portion 8 is formed. However, in order to determine the positions of the formation region of the Au film and the installation region of the cavity 8, advanced alignment is necessary. Further, the film formation step of step S1 may be performed after the cavity part installation step of step S5. However, since the Au film is formed on the bottom of the concave portion of the cavity portion 8, there is a problem that it is difficult to form a uniform film thickness as compared with the present embodiment.

  (Modification 3) In the Lamb wave resonator 1, the thickness H of the quartz substrate 2 is 15 μm, the pitch P of the electrode fingers 31a and 32a of the comb-like electrode 3 is 3 μm, and the thickness J of the Au film is 0.1 μm. However, this is an example, and the setting may be changed as appropriate according to the Lamb wave to be excited.

  (Modification 4) The electrode pad 5 is not limited to the structure which extends from the comb-like electrode 3 and extends to the corner of the quartz substrate 2 as shown in FIG. FIG. 6 is a plan view showing a configuration of a modified example of the Lamb wave type resonator. As shown in FIG. 6, the electrode pad 50 (50a, 50b) may be provided in the immediate vicinity of the comb-like electrode 3. As a result, the capacitance between the metal film 6 and the electrode pad 50 is changed to a value different from the capacitance between the metal film 6 and the electrode pad 5, and the frequency of the Lamb wave resonator 1 is changed. Etc. can be controlled.

  (Modification 5) The comb-like electrode 3, the reflector 4 and the electrode pad 5 are deposited aluminum (Al), but chromium (Cr), nickel (Ni), titanium (Ti) other than aluminum (Al) , Gold (Au), etc., or these may be laminated. Moreover, the method of forming in a comb-tooth shape etc. is not limited to an etching, A resist is apply | coated to parts other than the area | region which forms the comb-tooth-shaped electrode 3, the reflector 4, and the electrode pad 5, and the resist is not apply | coated. A method of forming aluminum (Al) or the like on the portion by vapor deposition or the like may be used.

  (Modification 6) Although the Lamb wave type resonator 1 has a configuration including the reflectors 4, a so-called end-surface reflection type configuration without the reflectors 4 may be used.

  (Modification 7) A Lamb wave device having a holding film such as an Au film and a support substrate 7 is not limited to the application to the Lamb wave resonator 1, and includes a filter, an oscillator equipped with an oscillation circuit, and the like. In addition, it can be applied to various devices in which the piezoelectric substrate is preferably thin.

  DESCRIPTION OF SYMBOLS 1 ... Lamb wave type resonator as a Lamb wave type device, 2 ... Quartz substrate as a piezoelectric substrate, 3 ... Comb-like electrode as excitation electrode, 4 ... Reflector, 5 ... Electrode pad, 6 ... As holding film Metal film, 7 ... support substrate, 8 ... cavity part, 31 ... first electrode, 31a ... electrode finger, 32 ... second electrode, 32a ... electrode finger, 50 ... electrode pad.

Claims (7)

A lamb wave device for exciting lamb waves,
A piezoelectric substrate;
An excitation electrode formed on one surface of the piezoelectric substrate;
A holding film formed on the other surface of the piezoelectric substrate;
A support substrate bonded to the holding film;
A Lamb wave type device comprising: a cavity portion provided on the support substrate and positioned opposite to the excitation electrode through the piezoelectric substrate and the holding film. The lamb wave device according to claim 1,
The Lamb wave device, wherein the holding film is a metal film. In the Lamb wave type device according to claim 1 or 2,
The Lamb wave type device is characterized in that the support substrate is any one of silicon, crystal, lithium tantalate, lithium niobate, zinc oxide, aluminum nitride, potassium niobate and glass. In the Lamb wave type device according to any one of claims 1 to 3,
The cavity portion has a Lamb wave type device in which a region facing the excitation electrode is equal to or larger than a region of the excitation electrode. In the lamb wave type device according to any one of claims 1 to 4,
The excitation electrode is a comb-like electrode and has a reflector on both sides of the comb-like electrode. A method of manufacturing a Lamb wave type device for exciting Lamb waves,
A film forming step of forming a holding film on one surface of the piezoelectric substrate;
A bonding step of bonding a support substrate to the holding film;
A thinning step for thinly processing the piezoelectric substrate;
Forming an excitation electrode on the surface of the piezoelectric substrate; and
A method for manufacturing a Lamb wave type device, comprising: a cavity portion installation step in which a cavity portion located opposite to the excitation electrode via the piezoelectric substrate and the holding film is provided on the support substrate. In the manufacturing method of the Lamb wave type device according to claim 6,
The holding film formed in the film forming step is a metal film, and the cavity portion formed in the cavity portion installation step has a region facing the excitation electrode having an area equal to or larger than the region of the excitation electrode. A method for manufacturing a Lamb wave device.

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