JP2008306280A - Piezoelectric thin film device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a piezoelectric thin film resonator from being affected by sub-resonance even if thickness of a piezoelectric thin film varies. <P>SOLUTION: The piezoelectric thin film resonator 1 has such a structure that a lower surface electrode 14 and an upper surface electrode 16 are formed on both principal planes of the piezoelectric thin film 15 supported by a support substrate 11 and are opposed to each other with the piezoelectric thin film 15 interposed therebetween. The upper surface electrode 16 which is made partially thicker by adding a conductor thin film 1602 to a conductor thin film 1601 has a distribution of thickness canceling a distribution of thickness of the piezoelectric thin film 15 in a free vibration region 192. When the upper surface electrode 16 having such a distribution of thickness is employed, the piezoelectric resonator is prevented from resonating at a plurality of resonance frequencies and then hardly affected by sub-resonance. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a piezoelectric thin film device including one or more piezoelectric thin film resonators.

  BACKGROUND ART A piezoelectric bulk acoustic resonator (FBAR) has a structure in which electrode films are formed on both main surfaces of a piezoelectric thin film, and the electrode films are opposed to each other with the piezoelectric thin film interposed therebetween. The piezoelectric thin film resonator is a resonator using an electrical response derived from thickness longitudinal vibration or thickness shear vibration. Therefore, the resonance frequency of the piezoelectric thin film resonator depends on the film thickness of the piezoelectric thin film.

  Patent Document 1 is a prior art document related to the present invention, and refers to a piezoelectric thin film resonator in which the film thickness of the electrode film is not uniform.

JP 2007-006501 A

  However, since the piezoelectric thin film resonator has a structure in which different kinds of materials are laminated, the piezoelectric thin film may be warped due to the difference in thermal expansion coefficient or lattice constant of the material, or the piezoelectric thin film May be deformed. In addition, when processing is performed on the piezoelectric thin film, the piezoelectric thin film may be warped or the piezoelectric thin film may be deformed due to residual stress generated in the piezoelectric thin film by processing. . That is, the piezoelectric thin film resonator has a problem that it is difficult to completely flatten the piezoelectric thin film, and the film thickness of the piezoelectric thin film may vary. Such a variation in the film thickness of the piezoelectric thin film causes the piezoelectric thin film resonator to resonate at a plurality of resonance frequencies, that is, the piezoelectric thin film resonator is affected by unwanted sub-resonance. Cause problems.

  The present invention has been made to solve this problem, and it is an object of the present invention to prevent the piezoelectric thin film resonator from being affected by sub-resonance even when the thickness of the piezoelectric thin film varies.

  In order to solve the above-mentioned problem, the invention of claim 1 is a piezoelectric thin film device including one or more piezoelectric thin film resonators, formed on both main surfaces of the piezoelectric thin film and the piezoelectric thin film, And a support substrate that supports a vibrating body in which the piezoelectric thin film and the electrode film are stacked, and the vibrating body is separated from the support substrate by a cavity. In the free vibration region, the electrode film has a film thickness distribution that cancels the film thickness distribution of the piezoelectric thin film.

  The invention according to claim 2 is the electrode film according to claim 1, wherein the electrode film is formed by further processing a conductor thin film on a part of the conductor thin film having a uniform thickness in the free vibration region. A piezoelectric thin film device.

  The invention according to claim 3 is the piezoelectric thin film device according to claim 1, wherein the electrode film is formed by removing a part of a conductor thin film having a uniform film thickness in the free vibration region. .

  According to a fourth aspect of the present invention, there is provided a piezoelectric thin film device including one or a plurality of piezoelectric thin film resonators, formed on both main surfaces of the piezoelectric thin film and the piezoelectric thin film, and sandwiching the piezoelectric thin film in an opposing region. An electrode film of a conductor facing each other, an additional film of an insulator formed on the electrode film, a support substrate that supports a vibrating body in which the piezoelectric thin film, the electrode film, and the additional film are stacked. And a laminated film of the electrode film and the additional film has a film thickness distribution that offsets the film thickness distribution of the piezoelectric thin film in a free vibration region where the vibrating body is separated from the support substrate by a cavity. is doing.

  A fifth aspect of the present invention is the piezoelectric thin film device according to any one of the first to fourth aspects, wherein the facing region includes the free vibration region.

  The invention according to claim 6 is the piezoelectric according to any one of claims 1 to 4, wherein the planar shape of the facing region is an elongated shape whose length in the longitudinal direction is twice or more the length in the short direction. It is a thin film device.

  According to the present invention, even if the film thickness of the piezoelectric thin film varies, the piezoelectric thin film resonator is not easily affected by sub-resonance.

  According to the invention of claim 4 or claim 5, sub-resonance can be more strongly suppressed.

  In the following, a preferred embodiment of the piezoelectric thin film device of the present invention will be described using a single piezoelectric thin film resonator (FBAR) as an example. However, the embodiment described below does not mean that the piezoelectric thin film device of the present invention is limited to a single piezoelectric thin film resonator. That is, the piezoelectric thin film device in the present invention generally means all piezoelectric thin film devices including one or a plurality of piezoelectric thin film resonators, and an oscillator and a trap including a single piezoelectric thin film resonator. And filters including a plurality of piezoelectric thin film resonators, duplexers, triplexers, traps, and the like.

<1 First Embodiment>
<1.1 Overall structure>
1 to 3 are schematic views of the piezoelectric thin film resonator 1 according to the first embodiment of the present invention. 1 is a perspective view of the piezoelectric thin film resonator 1, FIG. 2 is a plan view of the piezoelectric thin film resonator 1, and FIG. 3 is a cross-sectional view of the piezoelectric thin film resonator 1 along a cutting line indicated by AA in FIG. ing.

  As shown in FIGS. 1 to 3, the piezoelectric thin film resonator 1 includes an adhesive layer 12, a cavity forming film 13, a lower surface electrode 14, a piezoelectric thin film 15, and upper surface electrodes 16 and 17 in this order on a support substrate 11. It has a laminated structure. When the piezoelectric thin film resonator 1 is manufactured, the piezoelectric thin film 15 is obtained by removing a piezoelectric substrate 195 (described later) that can withstand its own weight, but the piezoelectric thin film 15 obtained by the removing process is single. I ca n’t stand my own weight. For this reason, when the piezoelectric thin film resonator 1 is manufactured, the piezoelectric substrate 195 on which the cavity forming film 13 and the lower surface electrode 14 are formed is bonded in advance to the support substrate 11 serving as a support prior to the removal processing.

<1.2 Support substrate>
When the piezoelectric substrate 195 is removed during the manufacturing process of the piezoelectric thin film resonator 1, the support substrate 11 attaches the piezoelectric substrate 195 having the cavity forming film 13 and the lower surface electrode 14 formed on the lower surface via the adhesive layer 12. It has a role as a support to support. In addition, after the piezoelectric thin film resonator 1 is manufactured, the support substrate 11 has the piezoelectric thin film 15 having the cavity forming film 13 and the lower surface electrode 14 formed on the lower surface and the upper surface electrodes 16 and 17 formed on the upper surface. It also has a role as a support body that supports via. Accordingly, the support substrate 11 is required to be able to withstand the force applied when the piezoelectric substrate 195 is removed, and not to decrease in strength even after the piezoelectric thin film resonator 1 is manufactured.

  The material constituting the support substrate 11 and the thickness of the support substrate 11 can be appropriately selected so as to satisfy such a requirement. However, the material of the support substrate 11 is a material having a thermal expansion coefficient close to that of the piezoelectric material constituting the piezoelectric thin film 15, more preferably a material having the same thermal expansion coefficient as the piezoelectric material constituting the piezoelectric thin film 15, for example, a piezoelectric body If the same material as the piezoelectric material constituting the thin film 15 is used, warping and breakage due to the difference in thermal expansion coefficient can be suppressed during the manufacturing of the piezoelectric thin film resonator 1. Thus, characteristic fluctuations and breakage due to the difference in thermal expansion coefficient can be suppressed. When a material having an anisotropic thermal expansion coefficient is used, it is desirable to consider that the thermal expansion coefficient in each direction is the same between the support substrate 11 and the piezoelectric thin film 15. When the same piezoelectric material is used for the body thin film 15, it is desirable that the crystal orientations of the support substrate 11 and the piezoelectric thin film 15 are matched.

<1.3 Adhesive layer>
When the piezoelectric substrate 195 is removed during the manufacturing process of the piezoelectric thin film resonator 1, the adhesive layer 12 adheres and fixes the piezoelectric substrate 195 having the cavity forming film 13 and the lower surface electrode 14 formed on the lower surface to the support substrate 11. Have a role to play. In addition, the adhesive layer 12 includes the piezoelectric thin film 15 having the cavity forming film 13 and the lower surface electrode 14 formed on the lower surface and the upper surface electrodes 16 and 17 formed on the upper surface after the manufacture of the piezoelectric thin film resonator 1. It also has the role of adhering and fixing to. Therefore, the adhesive layer 12 is required to be able to withstand the force applied when the piezoelectric substrate 195 is removed and that the adhesive force does not decrease even after the piezoelectric thin film resonator 1 is manufactured.

  Desirable examples of the adhesive layer 12 satisfying such requirements include an organic adhesive, preferably an epoxy adhesive having a filling effect and exhibiting sufficient adhesive force even if the object to be bonded is not completely flat ( Examples thereof include an adhesive layer 12 formed of an epoxy resin adhesive using thermosetting) and an acrylic adhesive (an acrylic resin adhesive using both photo-curing property and thermosetting property). By adopting such a resin, it is possible to prevent an unexpected gap from being generated between the support substrate 11 and the piezoelectric substrate 195, and to prevent a crack or the like from being generated when the piezoelectric substrate 195 is removed by the void. It can be prevented. However, this does not prevent the support substrate 11 and the piezoelectric thin film 15 from being bonded and fixed by the other adhesive layer 12.

<1.4 Cavity forming film>
The cavity forming film 13 is an insulator film obtained by forming an insulating material. The cavity forming film 13 is formed outside the free vibration region 192, and in the free vibration region 192, a cavity (cavity) that separates the vibrating body 10 in which the lower electrode 14, the piezoelectric thin film 15, and the upper electrode 16 are stacked from the support substrate 11. 135 is formed. The cavity forming film 13 having a role as a spacer can prevent the vibration body 10 from interfering with the support substrate 11 in the free vibration region 192 while supporting the vibration body 10 by the support substrate 11. become. The insulating material constituting the cavity forming film 13 is not particularly limited, but is preferably selected from insulating materials such as silicon dioxide (SiO ₂ ).

<1.5 Piezoelectric thin film>
The piezoelectric thin film 15 is obtained by removing the piezoelectric substrate 195. More specifically, the piezoelectric thin film 15 removes the piezoelectric substrate 195 having a thickness that can withstand its own weight (for example, 50 μm or more) to a thickness that cannot withstand its own weight (for example, 10 μm or less). It is obtained by thinning by processing.

As a piezoelectric material constituting the piezoelectric thin film 15, a piezoelectric material having desired piezoelectric characteristics can be selected, but quartz (SiO ₂ ), lithium niobate (LiNbO ₃ ), lithium tantalate (LiTaO ₃ ), Select single crystal materials that do not contain grain boundaries such as lithium tetraborate (Li ₂ B ₄ O ₇ ), zinc oxide (ZnO), potassium niobate (KNbO ₃ ) and langasite (La ₃ Ga ₃ SiO ₁₄ ) It is desirable. This is because by using a single crystal material as the piezoelectric material constituting the piezoelectric thin film 15, the electromechanical coupling coefficient and the mechanical quality factor of the piezoelectric thin film 15 can be improved.

  In addition, as the crystal orientation in the piezoelectric thin film 15, a crystal orientation having desired piezoelectric characteristics can be selected. Here, the crystal orientation in the piezoelectric thin film 15 is preferably a crystal orientation in which the temperature characteristics of the resonance frequency and antiresonance frequency of the piezoelectric thin film resonator 1 are favorable, and the crystal orientation in which the frequency temperature coefficient is “0”. Is more desirable.

  The removal processing of the piezoelectric substrate 195 is performed by mechanical processing such as cutting, grinding and polishing, and chemical processing such as etching. Here, if a plurality of removal processing methods are combined and the piezoelectric substrate is removed while switching the removal processing method step by step from the removal processing method with a high processing speed to the removal processing method with a small process alteration occurring on the processing target. The quality of the piezoelectric thin film 15 can be improved and the characteristics of the piezoelectric thin film resonator 1 can be improved while maintaining high productivity. For example, after performing polishing in which the piezoelectric substrate 195 is brought into contact with fixed abrasive grains and polishing in which the piezoelectric substrate 195 is brought into contact with loose abrasive grains are sequentially performed, a work-affected layer generated on the piezoelectric substrate 195 by the polishing. Is removed by finish polishing, the speed of cutting the piezoelectric substrate 195 can be increased, the productivity of the piezoelectric thin film resonator 1 can be improved, and the quality of the piezoelectric thin film 15 can be improved. The characteristics of the piezoelectric thin film resonator 1 can be improved.

  In such a piezoelectric thin film resonator 1, unlike the case where the piezoelectric thin film 15 is formed by sputtering or the like, the piezoelectric material constituting the piezoelectric thin film 15 and the crystal orientation in the piezoelectric thin film 15 are not restricted by the base. The degree of freedom in selecting the crystal orientation of the piezoelectric material constituting the piezoelectric thin film 15 and the piezoelectric thin film 15 is high. Therefore, the piezoelectric thin film resonator 1 can easily achieve desired characteristics.

  A via hole 155 is formed in the piezoelectric thin film 15 so as to penetrate between the lower surface and the upper surface of the piezoelectric thin film 15 and connect the lower electrode 14 and the upper electrode 17 facing each other with the piezoelectric thin film 15 interposed therebetween. . The via hole 155 electrically connects the lower electrode 14 and the upper electrode 17 by a conductive thin film formed on the inner surface thereof.

  In the piezoelectric thin film resonator 1, as shown in FIG. 3, the upper surface of the piezoelectric thin film 15 is substantially flat, but the lower surface of the piezoelectric thin film 15 is curved downward in the free vibration region 192. For this reason, the film thickness of the piezoelectric thin film 15 increases continuously from the peripheral edge of the free vibration region 192 toward the center. Such a film thickness variation is caused by the production of the piezoelectric thin film resonator 1 between the free vibration region 192 where the cavity forming film 12 is not formed and the fixed region 193 where the cavity forming film 12 is formed. This is because the stress applied to the piezoelectric thin film 15 is different during the process.

<1.6 Bottom electrode and top electrode>
The lower surface electrode 14 and the upper surface electrodes 16 and 17 are conductor thin films formed by depositing a conductive material on the lower surface and the upper surface of the piezoelectric thin film 15, respectively.

  The conductive material constituting the lower surface electrode 14 and the upper surface electrodes 16 and 17 is not particularly limited, but aluminum (Al), silver (Ag), copper (Cu), platinum (Pt), gold (Au), chromium (Cr) It is desirable to select from metals such as nickel (Ni), molybdenum (Mo), tungsten (W), ruthenium (Ru), iridium (Ir) and tantalum (Ta). Of course, an alloy may be used as the conductive material constituting the lower surface electrode 14 and the upper surface electrodes 16 and 17. Further, the lower electrode 14 and the upper electrodes 16 and 17 may be formed by stacking a plurality of kinds of conductive materials.

  The elongated rectangular drive unit 141 occupying a part of the lower surface electrode 14 and the elongated rectangular drive unit 161 occupying a part of the upper surface electrode 16 are opposed to each other with the piezoelectric thin film 15 interposed therebetween in the facing region 191. The power feeding portion 142 occupying the remainder of the lower surface electrode 14 excluding the driving portion 141 is connected to the upper surface electrode 17 by a via hole 155.

  The reason why the planar shapes of the drive unit 141 and the drive unit 161 are elongated is to suppress sub-resonance more strongly. Here, the “elongated shape” means that the length in the longitudinal direction of the drive unit 141 and the drive unit 161 (the length of the long side of the rectangle, the major axis of the ellipse, etc.) is the length in the short direction (the rectangular short shape). (A length of a side or an elliptical short axis) is a planar shape that is 2 times or more, preferably 4 times or more, and more preferably 10 times or more. However, this does not prevent the driving unit 141 and the driving unit 161 from having a planar shape that is not an elongated shape.

  By the lower surface electrode 14 and the upper surface electrodes 16 and 17, the piezoelectric thin film resonator 1 excites the power supply portion 162 and the upper surface electrode 17 that are exposed to the outside and occupy the remainder excluding the driving portion 161 of the upper surface electrode 16. When a signal is applied, an excitation signal is applied to the drive unit 141 of the lower surface electrode 14 and the drive unit 161 of the upper surface electrode 16, and vibration is excited in the free vibration region 192. Thereby, the piezoelectric thin film resonator 1 functions as an energy confinement type resonator using thickness longitudinal vibration or thickness shear vibration.

  In the piezoelectric thin film resonator 1, the facing region 191 includes the free vibration region 192. As described above, when the peripheral portion of the facing region 191 is fixed to the support substrate 11 via the adhesive layer 12 and the cavity forming film 13, the sub-resonance of the piezoelectric thin film resonator 1 can be more strongly suppressed. . However, this does not prevent the free vibration region 192 from including the opposing region 191.

  As shown in FIG. 3, the upper surface electrode 16 is formed by additionally processing the conductor thin film 1602 on a part of the conductor thin film 1601 having a uniform thickness in the free vibration region 192. The conductor thin film 1602 is added to the periphery of the free vibration region 192 where the film thickness of the piezoelectric thin film 15 is reduced. The conductive material constituting the conductor thin film 1601 and the conductive material constituting the conductor thin film 1602 may be the same or different. However, when the top electrode 16 is formed by photolithography using wet etching, it is necessary to perform selective etching. Therefore, the conductive thin film 1601 and the conductive thin film 1602 are formed of different conductive materials. Is desirable.

  As described above, the upper surface electrode 16 obtained by additionally processing the conductive thin film 1602 on the conductive thin film 1601 and partially thickening the film thickness cancels the film thickness distribution of the piezoelectric thin film 15 in the free vibration region 192. Having a distribution of If the upper surface electrode 16 having such a film thickness distribution is employed, the piezoelectric thin film resonator 1 can be prevented from resonating at a plurality of resonance frequencies, and the piezoelectric thin film resonator 1 has sub-resonance (spurious). Less affected.

  When the film thickness of the piezoelectric thin film 15 changes continuously, the film thickness of the upper surface electrode 16 is also changed continuously, that is, as the film thickness of the piezoelectric thin film 15 increases continuously, the upper surface electrode Although it is most desirable that the film thickness of 16 is continuously reduced, as shown in FIG. 3, a practical effect of suppressing sub-resonance can be obtained only by changing the film thickness of the upper surface electrode 16 stepwise. be able to. Of course, it is not essential to change the film thickness in two steps, and it may be changed in three or more steps. Thus, the upper surface electrode 16 whose film thickness changes stepwise can be formed more easily than that whose film thickness changes continuously.

  Further, instead of forming the upper surface electrode 15 having a film thickness distribution that cancels the film thickness distribution of the piezoelectric thin film 15 in the free vibration region 192, or in the free vibration region 192, the film thickness of the piezoelectric thin film 15. In addition to forming the upper surface electrode 15 having a film thickness distribution that cancels the distribution of the piezoelectric material, the lower surface electrode 14 having a film thickness distribution that cancels the film thickness distribution of the piezoelectric thin film 15 in the free vibration region 192 is formed. May be.

<1.7 Basic concept on film thickness distribution>
The longitudinal effect vibrator 1a shown in the cross-sectional view of FIG. 4 in which the film-like lower surface electrode 14a and the upper surface electrode 16a are formed on the lower and upper surfaces of the film-like piezoelectric body 15a polarized in the thickness direction, respectively, is the circuit of FIG. The equivalent circuit 1b shown in the figure can be modeled, and the impedance of the longitudinal effect vibrator 1a can be expressed as the impedance of the electrical port 153b. This modeling is based on the well-known Mason technique.

  The equivalent circuit 1b models a three-port equivalent circuit 15b that models a piezoelectric body 15a in which electrodes with negligible film thickness are formed on both main surfaces, a two-port equivalent circuit 14b that models a lower surface electrode 14a, and an upper surface electrode 16a. It can be regarded as coupling with the 2-port equivalent circuit 16b.

  The three-port equivalent circuit 15b includes two mechanical ports 151b and 152b and one electric port 153b. The two-port equivalent circuit 14b includes two mechanical ports 141b and 142b, and two two-port equivalent circuits 16b. Machine ports 161b and 162b. The mechanical port 151b of the 3-port equivalent circuit 15b is connected to the mechanical port 142b of the 2-port equivalent circuit 14b, and the mechanical port 152b of the 3-port equivalent circuit 15b is connected to the mechanical port 161b of the 2-port equivalent circuit 16b. Further, the mechanical port 141b of the 2-port equivalent circuit 14b is short-circuited reflecting that the medium below the lower surface electrode 14a is air whose acoustic impedance can be regarded as substantially zero. The mechanical port 162b of the two-port equivalent circuit 16b is also short-circuited reflecting that the medium above the upper surface electrode 16a is air whose acoustic impedance can be regarded as substantially zero.

  The 3-port equivalent circuit 15b includes reactance elements 154b, 155b, and 156b connected in a T shape. One end of the reactance element 154b, one end of the reactance element 155b, and one end of the reactance element 156b are connected. The other end of the reactance 154b is connected to the ground end of the machine port 151b and the ground end of the machine port 152b via the secondary side of the ideal transformer 157b. The other end of the reactance element 155b is connected to the signal end of the mechanical port 151b. The other end of the reactance element 156b is connected to the signal end of the mechanical port 152b. The 3-port equivalent circuit 15b includes a capacitive element 158b and a negative capacitive element 159b connected in an inverted L shape. One end of the capacitive element 158b is connected to the signal end of the electrical port 153b, and the other end of the capacitive element 158b is connected to the ground end of the electrical port 153b and one end on the primary side of the ideal transformer 157b. One end of the negative capacitive element 159b is connected to the signal end of the electrical port 153b, and the other end of the negative capacitive element 159b is connected to the other end of the ideal transformer 157b.

Impedance Z _a1 and reactance element 155b of the reactance element 154b, the impedance Z _b1 of 156b, the area of the piezoelectric body 15a S _1, the thickness L ₁ of the piezoelectric 15a, acoustic velocity [nu ₁ in in a piezoelectric body 15a, the piezoelectric 15a Using the density ρ ₁ and the angular frequency ω (= 2πf), they are expressed by Expression 1 and Expression 2, respectively.

The 2-port equivalent circuit 14b includes reactance elements 144b, 145b, and 146b connected in a T shape. One end of the reactance element 144b, one end of the reactance element 145b, and one end of the reactance element 146b are connected. The other end of the reactance element 144b is connected to the ground end of the mechanical port 141b and the ground end of the mechanical port 142b. The other end of the reactance element 145b is connected to the signal end of the mechanical port 141b. The other end of the reactance element 146b is connected to the signal end of the mechanical port 142b. The impedance Z _a2 of the reactance element 144b and the impedance Z _b2 of the reactance elements 145b and 146b are the area S _{2 of} the lower surface electrode 14a, the film thickness L _{2 of} the lower surface electrode 14a, the sound velocity ν _{2 in} the lower surface electrode 14a, and the lower surface electrode 14a. Using the density ρ ₂ and the angular frequency ω, they are expressed by Expression 3 and Expression 4, respectively.

Similarly, the 2-port equivalent circuit 16b includes reactance elements 164b, 165b, and 166b connected in a T shape. One end of the reactance element 164b, one end of the reactance element 165b, and one end of the reactance element 166b are connected. The other end of the reactance 164b is connected to the ground end of the machine port 161b and the ground end of the machine port 162b. The other end of the reactance element 165b is connected to the signal end of the mechanical port 161b. The other end of the reactance element 166b is connected to the signal end of the mechanical port 162b. The impedance Z _a3 of the reactance element 164b and the impedance Z _b3 of the reactance elements 165b and 166b are the area S _{3 of} the upper surface electrode 16a, the film thickness L _{3 of} the upper surface electrode 16a, the speed of sound ν _{3 in} the upper surface electrode 16a, and the upper surface electrode 16a. Using the density ρ ₃ and the angular frequency ω, they are expressed by Expression 5 and Expression 6, respectively.

Therefore, if the transformation ratio of the ideal transformer 157b is n, the admittance viewed from the primary side of the ideal transformer 157b is expressed by Equation 7, and the admittance Y viewed from the electrical port 153b is obtained by using the capacitance C _d of the capacitive element 158b. It is represented by Formula 8.

Here, the impedance viewed from the electrical port 153b is "0" at the resonant frequency f _r, the resonance frequency f _r can be obtained by solving the resulting equation the denominator of Equation 8 as 0 for the frequency f, The resonance frequency _fr is expressed by Equation 9 as a function of the film thicknesses L ₁ , L ₂ , and L ₃ .

As can be seen from Equation 9, if the film thickness of the piezoelectric body 15 increases or decreases while the film thickness of the lower electrode 14 and the film thickness of the upper electrode 16 are constant in the free vibration region 192, the resonance frequency also varies in the free vibration region 192. However, if the film thickness of the lower electrode 14 and the film thickness of the upper electrode 16 are decreased in accordance with the increase or decrease of the film thickness of the piezoelectric body 15 in the free vibration region 192, the fluctuation of the resonance frequency in the free vibration region 192 can be reduced. And sub-resonance can be suppressed. For example, the free vibration region 192 is divided into n regions R _i (n = 1, 2,..., N) so that the deviation of the resonance frequency f _ri of the region R _i specified by Equation 9 becomes small. to, if an increase of decrease the thickness of the lower electrode 14 and upper electrode 16 in each of the regions R _i, a secondary resonance can be suppressed.

The capacitance C _d of the capacitive element 158b is expressed by Equation 10 using the dielectric constant ε _{33 of} the piezoelectric body 15a, the area S _{1 of} the piezoelectric body 15a, and the plate thickness L ₁ of the piezoelectric body 15a, and the transformation of the ideal transformer 157b. The ratio n is expressed by Equation 11 using the piezoelectric constant e _{33 of} the piezoelectric body 15a, the area S _{1 of} the piezoelectric body 15a, and the plate thickness L ₁ of the piezoelectric body 15a.

<1.8 Manufacturing method>
Subsequently, lithium niobate single crystal as the piezoelectric material constituting the support substrate 11 and the piezoelectric thin film 15, epoxy adhesive as the material constituting the adhesive layer 12, silicon dioxide as the insulating material constituting the cavity forming film 13, lower surface A method for manufacturing the piezoelectric thin film resonator 1 will be described by taking as an example the case where molybdenum is used as the conductive material constituting the electrode 14 and gold is used as the conductive material constituting the upper surface electrode 16. However, the manufacturing method described below is merely an example, and does not prevent the material from being changed according to desired characteristics. Further, it is not essential to obtain the piezoelectric thin film 15 by removing the piezoelectric substrate 195. As is conventionally done, the lower electrode, the piezoelectric thin film, and the upper electrode are added on the support substrate by sputtering or the like. The piezoelectric thin film resonator 1 may be manufactured by sequentially forming films by processing.

  In the manufacturing method described below, the piezoelectric thin film resonator 1 is formed by integrating a large number (typically several hundred to several thousand) of piezoelectric thin film resonators 1 in order to reduce the manufacturing cost. After the mother substrate is manufactured, the mother substrate is cut with a dicing saw and separated into individual piezoelectric thin film resonators 1.

  In the following, for the sake of convenience, the description will be given focusing on one piezoelectric thin film resonator 1 included in the mother substrate, but other piezoelectric thin film resonators 1 included in the mother substrate are also simultaneously focused on the piezoelectric thin film resonator 1 focused on. Manufactured in parallel.

  In manufacturing the piezoelectric thin film resonator 1, first, a molybdenum film is formed on the entire lower surface of the piezoelectric substrate 195 by sputtering, and patterning is performed using a general photolithography process to obtain the lower electrode 14 ( FIG. 6).

  Subsequently, a silicon dioxide film is formed on the entire lower surface of the piezoelectric substrate 195 by sputtering, and patterning is performed using a general photolithography process to form the cavity forming film 13 (FIG. 7).

  Subsequently, an epoxy adhesive serving as the adhesive layer 12 is applied to the upper surface of the support substrate 11, and the upper surface of the support substrate 11 is bonded to the lower surface of the piezoelectric substrate 195 on which the lower electrode 14 and the cavity forming film 13 are formed. The Then, pressure is applied to the support substrate 11 and the piezoelectric substrate 195 to perform press-bonding. Thereafter, the epoxy adhesive is cured to bond the support substrate 11 and the piezoelectric substrate 195 (FIG. 8).

  After the bonding between the support substrate 11 and the piezoelectric substrate 195 is completed, the lower surface of the support substrate 11 is bonded and fixed to the polishing jig while maintaining the state where the piezoelectric substrate 195 is bonded to the support substrate 11. The upper surface of 195 is ground with a fixed abrasive grinder to thin the piezoelectric substrate 195. Further, the upper surface of the piezoelectric substrate 195 is polished with diamond abrasive grains, so that the piezoelectric substrate 195 is further thinned. Finally, in order to remove the work-affected layer generated on the piezoelectric substrate 195 by polishing with diamond abrasive grains, the piezoelectric substrate 195 is subjected to final polishing using loose abrasive grains and a non-woven cloth polishing pad. A piezoelectric thin film 15 having a thickness of 5 is obtained (FIG. 9). FIG. 9 shows a state in which the thickness of the piezoelectric thin film 15 varies when the piezoelectric thin film 15 is obtained by removing the piezoelectric substrate 195. However, the film thickness of the piezoelectric thin film 15 may vary in other processes.

  Next, the upper surface (polished surface) of the piezoelectric thin film 15 is washed with an organic solvent, and a chromium film and a gold film are sequentially formed on the upper surface of the piezoelectric thin film 15, and the obtained laminated film is formed by general photolithography. By patterning using a process, an etching mask 196 is obtained in which only the portion of the piezoelectric thin film 15 where the via hole 155 is to be formed is exposed (FIG. 10).

  After the etching mask 196 is formed, the piezoelectric thin film 15 is etched with heated buffered hydrofluoric acid to form a via hole 155 that penetrates between the upper surface and the lower surface of the piezoelectric thin film 15 to expose the lower electrode 14. At the same time, the etching mask 196 is removed by etching (FIG. 11).

  Then, a gold film is formed on the entire upper surface of the piezoelectric thin film 15 by sputtering, and patterning is performed using a general photolithography process to obtain the conductive thin film 1601 and the upper electrode 17 below the upper electrode 16 ( FIG. 12). At this time, since the conductive thin film is also formed on the inner side surface of the via hole 155, conduction between the lower surface electrode 14 and the upper surface electrode 17 is ensured.

  Further, a gold film is formed by sputtering on the upper surface of the piezoelectric thin film 15 on which the conductive thin film 1601 is formed, and an upper conductive thin film 1602 on the upper surface electrode 16 is obtained. Thus, the piezoelectric thin film resonator 1 is manufactured (FIG. 3).

<1.9 Sub-resonance suppression effect>
FIG. 13 shows the frequency of the piezoelectric thin film resonator 1 in which the driving units 141 and 161 have a planar shape of 200 μm long × 25 μm wide, the conductive thin film 1602 has a width of 3 μm, and the conductive thin film 1602 has a thickness of 0.087 μm. FIG. 14 is a diagram illustrating an example of the impedance-characteristic, and FIG. 14 is a diagram illustrating an example of the frequency-impedance characteristic of the piezoelectric thin film resonator equivalent to the piezoelectric thin film resonance 1 except that the conductive thin film 1602 is not added. is there. From FIG. 13 and FIG. 14, by adding a conductive thin film 1602 and giving the upper surface electrode 16 a film thickness distribution that cancels the film thickness distribution of the piezoelectric thin film 15, a sub-resonance having a frequency higher than the resonance frequency is obtained. It turns out that it can suppress.

<2 Second Embodiment>
FIG. 15 is a schematic diagram of the piezoelectric thin film resonator 2 according to the second embodiment of the present invention. FIG. 15 is a cross-sectional view of the piezoelectric thin film resonator 2.

  As shown in FIG. 15, the piezoelectric thin film resonator 2 has a structure in which an adhesive layer 22, a cavity forming film 23, a lower surface electrode 24, a piezoelectric thin film 25, and an upper surface electrode 26 are laminated in this order on a support substrate 21. Have. The piezoelectric thin film resonator 2 has the same structure as the piezoelectric thin film resonator 1 except for the upper surface electrode 26, and includes a support substrate 21, an adhesive layer 22, a cavity forming film 23, a lower surface electrode 24, a piezoelectric thin film 25, and The upper surface electrode 26 corresponds to the support substrate 11, the adhesive layer 12, the cavity forming film 13, the lower surface electrode 14, the piezoelectric thin film 15, and the upper surface electrode 16 of the piezoelectric thin film resonator 1, respectively.

  The difference between the piezoelectric thin film resonator 1 and the piezoelectric thin film resonator 2 is that the piezoelectric thin film resonator 1 is obtained by further processing the conductive thin film 1602 on a part of the conductive thin film 1601 having a uniform film thickness, thereby forming a piezoelectric body. In contrast to the film thickness distribution of the upper surface electrode 16 that cancels out the film thickness distribution of the thin film 15, the piezoelectric thin film resonator 2 removes a part of the conductor thin film having a uniform film thickness. By forming the groove 265, the film thickness distribution of the upper surface electrode 26 that cancels the film thickness distribution of the piezoelectric thin film 25 in the free vibration region 292 is obtained. Specifically, in the piezoelectric thin film resonator 2, a conductive thin film having a uniform thickness is formed, and the central portion of the free vibration region 292 where the thickness of the piezoelectric thin film 25 is increased is processed by laser processing or ion beam (IB). ) The upper surface electrode 26 is formed by removal processing or the like.

  Even when the upper surface electrode 26 having such a film thickness distribution is employed, the piezoelectric thin film resonator 2 can be prevented from resonating at a plurality of resonance frequencies. It becomes difficult to receive.

<3 Third Embodiment>
FIG. 16 is a schematic diagram of the piezoelectric thin film resonator 3 according to the third embodiment of the present invention. FIG. 16 is a cross-sectional view of the piezoelectric thin film resonator 3.

  As shown in FIG. 16, the piezoelectric thin film resonator 3 has a structure in which an adhesive layer 32, a cavity forming film 33, a lower surface electrode 34, a piezoelectric thin film 35, and an upper surface electrode 36 are laminated in this order on a support substrate 31. Have. The piezoelectric thin film resonator 3 has the same structure as the piezoelectric thin film resonator 1 except for the piezoelectric thin film 35 and the upper surface electrode 36, and includes a support substrate 31, an adhesive layer 32, a cavity forming film 33, a lower surface electrode 34, The piezoelectric thin film 35 and the upper surface electrode 36 correspond to the support substrate 11, the adhesive layer 12, the cavity forming film 13, the lower surface electrode 14, the piezoelectric thin film 15, and the upper surface electrode 16 of the piezoelectric thin film resonator 1, respectively. Yes.

  The difference between the piezoelectric thin film resonator 1 and the piezoelectric thin film resonator 3 is that in the piezoelectric thin film resonator 1, the lower surface of the piezoelectric thin film 15 is curved downward in the free vibration region 192, and the thickness of the piezoelectric thin film 15 is The conductor thin film 1602 is added to the periphery of the thinned free vibration region 192 to obtain the film thickness distribution of the top electrode 16 that cancels the film thickness distribution of the piezoelectric thin film 15, whereas the piezoelectric thin film resonance In the child 3, the lower surface of the piezoelectric thin film 35 is curved upward in the free vibration region 392, and is superposed on the conductive thin film 3601 having a uniform film thickness, so that the piezoelectric thin film 35 becomes thin. A conductor thin film 3602 is added to the center of the region 392, and the film thickness distribution of the upper surface electrode 36 that cancels the film thickness distribution of the piezoelectric thin film 35 in the free vibration region 392 is obtained.

  Even if the upper surface electrode 36 having such a film thickness distribution is employed, the piezoelectric thin film resonator 3 can be prevented from resonating at a plurality of resonance frequencies, and the piezoelectric thin film resonator 3 can be influenced by sub-resonance. It becomes difficult to receive.

<4 Fourth Embodiment>
FIG. 17 is a schematic diagram of a piezoelectric thin film resonator 4 according to a fourth embodiment of the present invention. FIG. 17 is a cross-sectional view of the piezoelectric thin film resonator 4.

  As shown in FIG. 17, the piezoelectric thin film resonator 4 has a structure in which an adhesive layer 42, a cavity forming film 43, a lower surface electrode 44, a piezoelectric thin film 45, and an upper surface electrode 46 are laminated in this order on a support substrate 41. Have. The piezoelectric thin film resonator 4 has the same structure as the piezoelectric thin film resonator 3 except for the upper surface electrode 46, and includes a support substrate 41, an adhesive layer 42, a cavity forming film 43, a lower surface electrode 44, a piezoelectric thin film 45, and The upper surface electrode 46 corresponds to the support substrate 31, the adhesive layer 32, the cavity forming film 33, the lower surface electrode 34, the piezoelectric thin film 35, and the upper surface electrode 36 of the piezoelectric thin film resonator 3, respectively.

  The difference between the piezoelectric thin film resonator 3 and the piezoelectric thin film resonator 4 is that the piezoelectric thin film resonator 3 is obtained by additionally processing the conductive thin film 3602 on a part of the conductive thin film 3601 having a uniform thickness. While the film thickness distribution of the upper surface electrode 36 that cancels the film thickness distribution of the thin film 35 is obtained, the piezoelectric thin film resonator 4 removes a part of the conductor thin film having a uniform film thickness. Thus, in the free vibration region 492, the film thickness distribution of the upper surface electrode 46 that cancels the film thickness distribution of the piezoelectric thin film 45 is obtained. Specifically, in the piezoelectric thin film resonator 4, a conductive thin film having a uniform thickness is formed, and the peripheral portion of the free vibration region 492 in which the thickness of the piezoelectric thin film 45 is increased is removed to process the upper surface. An electrode 46 is formed.

  Even if the upper surface electrode 46 having such a film thickness distribution is employed, the piezoelectric thin film resonator 4 can be prevented from resonating at a plurality of resonance frequencies, and the piezoelectric thin film resonator 4 can be influenced by sub-resonance. It becomes difficult to receive.

  For example, in FIG. 18, the planar shape of the drive units 441 and 461 is a rectangle of 200 μm length × 25 μm width, the width of the groove 465 obtained by the removal process is 4.5 μm, and the removal process using the ion beam (IB). FIG. 19 is a diagram showing an example of frequency-impedance characteristics of the piezoelectric thin film resonator 4 in which the width of the groove formed by the step is 4.5 μm and the depth is 0.15 μm. FIG. FIG. 5 is a diagram showing an example of frequency-impedance characteristics of a piezoelectric thin film resonator equivalent to the piezoelectric thin film resonance 1. From FIG. 18 and FIG. 19, by removing a part of the conductor thin film having a uniform film thickness and providing the upper surface electrode 46 with a film thickness distribution that cancels the film thickness distribution of the piezoelectric thin film 45, It can be seen that a sub-resonance having a frequency lower than the resonance frequency can be suppressed.

<5 Fifth Embodiment>
FIG. 20 is a schematic diagram of a piezoelectric thin film resonator 5 according to a fifth embodiment of the present invention. FIG. 20 is a cross-sectional view of the piezoelectric thin film resonator 5.

  As shown in FIG. 20, the piezoelectric thin film resonator 5 has a structure in which an adhesive layer 52, a cavity forming film 53, a lower surface electrode 54, a piezoelectric thin film 55, and an upper surface electrode 56 are laminated in this order on a support substrate 51. Have. The piezoelectric thin film resonator 5 has the same structure as the piezoelectric thin film resonator 1 except for the piezoelectric thin film 55 and the upper surface electrode 56, and includes a support substrate 51, an adhesive layer 52, a cavity forming film 53, a lower surface electrode 54, The piezoelectric thin film 55 and the upper surface electrode 56 correspond to the support substrate 11, the adhesive layer 12, the cavity forming film 13, the lower surface electrode 14, the piezoelectric thin film 15, and the upper surface electrode 16 of the piezoelectric thin film resonator 1, respectively. Yes.

  The difference between the piezoelectric thin film resonator 1 and the piezoelectric thin film resonator 5 is that in the piezoelectric thin film resonator 1, the upper surface of the piezoelectric thin film 15 is substantially flat and the lower surface of the piezoelectric thin film 15 is curved downward in the free vibration region 192. In addition, the conductive thin film 1602 is added to the peripheral portion of the free vibration region 192 where the thickness of the piezoelectric thin film 15 is reduced, and the distribution of the thickness of the upper surface electrode 16 that cancels the distribution of the thickness of the piezoelectric thin film 15 is obtained. On the other hand, in the piezoelectric thin film resonator 5, the lower surface of the piezoelectric thin film 55 is substantially flat and the upper surface of the piezoelectric thin film 55 is curved downward, and the conductive thin film 5601 has a uniform film thickness. The conductor thin film 5602 is added to the center of the free vibration region 592 where the film thickness of the piezoelectric thin film 55 becomes thin, and the upper surface electrode 56 cancels out the film thickness distribution of the piezoelectric thin film 55 in the free vibration region 592. The film thickness distribution is obtained

  Even when the upper surface electrode 56 having such a film thickness distribution is employed, the piezoelectric thin film resonator 5 can be prevented from resonating at a plurality of resonance frequencies. It becomes difficult to receive.

<6 Sixth Embodiment>
FIG. 21 is a schematic diagram of a piezoelectric thin film resonator 6 according to a sixth embodiment of the present invention. FIG. 21 is a cross-sectional view of the piezoelectric thin film resonator 6.

  As shown in FIG. 21, the piezoelectric thin film resonator 6 has a structure in which an adhesive layer 62, a cavity forming film 63, a lower surface electrode 64, a piezoelectric thin film 65, and an upper surface electrode 66 are laminated in this order on a support substrate 61. Have. The piezoelectric thin film resonator 6 has the same structure as the piezoelectric thin film resonator 1 except for the piezoelectric thin film 65 and the upper surface electrode 66, and includes a support substrate 61, an adhesive layer 62, a cavity forming film 63, a lower surface electrode 64, The piezoelectric thin film 65 and the upper surface electrode 66 correspond to the support substrate 11, the adhesive layer 12, the cavity forming film 13, the lower surface electrode 14, the piezoelectric thin film 15, and the upper surface electrode 16 of the piezoelectric thin film resonator 1, respectively. Yes.

  The difference between the piezoelectric thin film resonator 1 and the piezoelectric thin film resonator 6 is that in the piezoelectric thin film resonator 1, the upper surface of the piezoelectric thin film 15 is substantially flat and the lower surface of the piezoelectric thin film 15 is curved downward in the free vibration region 192. In addition, a conductor thin film 1602 is added to the peripheral portion of the opposing region 191 where the film thickness of the piezoelectric thin film 15 is reduced, and a film thickness distribution of the upper surface electrode 16 is obtained to cancel the film thickness distribution of the piezoelectric thin film 15. On the other hand, in the piezoelectric thin film resonator 6, the lower surface of the piezoelectric thin film 65 is substantially flat and the upper surface of the piezoelectric thin film 65 is repeatedly undulated, and is superimposed on the conductor thin film 6601 having a uniform film thickness. Then, the conductive thin film 6602 is added to the concave portion where the thickness of the piezoelectric thin film 65 becomes thin, and the distribution of the thickness of the upper surface electrode 66 that cancels the distribution of the thickness of the piezoelectric thin film 65 in the free vibration region 692 is obtained. There is in point.

  Even if the upper surface electrode 66 having such a film thickness distribution is employed, the piezoelectric thin film resonator 6 can be prevented from resonating at a plurality of resonance frequencies, and the piezoelectric thin film resonator 6 can be influenced by sub-resonance. It becomes difficult to receive.

<7 Seventh Embodiment>
FIG. 22 is a schematic diagram of a piezoelectric thin film resonator 7 according to a seventh embodiment of the present invention. FIG. 22 is a cross-sectional view of the piezoelectric thin film resonator 7.

  As shown in FIG. 22, the piezoelectric thin film resonator 7 has a structure in which an adhesive layer 72, a cavity forming film 73, a lower surface electrode 74, a piezoelectric thin film 75, and an upper surface electrode 76 are laminated in this order on a support substrate 71. Have. The piezoelectric thin film resonator 7 has the same structure as the piezoelectric thin film resonator 1 except for the piezoelectric thin film 75 and the upper surface electrode 76, and includes a support substrate 71, an adhesive layer 72, a cavity forming film 73, a lower surface electrode 74, The piezoelectric thin film 75 and the upper surface electrode 76 correspond to the support substrate 11, the adhesive layer 12, the cavity forming film 13, the lower surface electrode 14, the piezoelectric thin film 15, and the upper surface electrode 16 of the piezoelectric thin film resonator 1, respectively. Yes.

  The difference between the piezoelectric thin film resonator 1 and the piezoelectric thin film resonator 7 is that in the piezoelectric thin film resonator 1, the upper surface of the piezoelectric thin film 15 is substantially flat and the lower surface of the piezoelectric thin film 15 is curved downward in the free vibration region 192. In addition, a conductor thin film 1602 is added to the peripheral portion of the opposing region 191 where the film thickness of the piezoelectric thin film 15 is reduced, and a film thickness distribution of the upper surface electrode 16 is obtained to cancel the film thickness distribution of the piezoelectric thin film 15. On the other hand, in the piezoelectric thin film resonator 7, the lower surface and the upper surface of the piezoelectric thin film 65 are substantially flat and the lower surface and the upper surface are non-parallel, and are stacked on the conductive thin film 7601 having a uniform film thickness. Thus, the conductive thin film gradually decreases in thickness from one end of the free vibration region 792 where the film thickness of the piezoelectric thin film 75 decreases toward the other end of the free vibration region 792 where the film thickness of the piezoelectric thin film 75 increases. 7602 is added to the free vibration region 792. It lies in that obtaining a film thickness distribution of the upper electrode 76 to offset the distribution of film thickness of the piezoelectric thin film 75 Te.

  Even when the upper surface electrode 76 having such a film thickness distribution is employed, the piezoelectric thin film resonator 7 can be prevented from resonating at a plurality of resonance frequencies, and the piezoelectric thin film resonator 7 can be influenced by sub-resonance. It becomes difficult to receive.

<8 Eighth Embodiment>
FIG. 23 is a schematic diagram of a piezoelectric thin film resonator 8 according to an eighth embodiment of the present invention. FIG. 23 is a cross-sectional view of the piezoelectric thin film resonator 8.

  As shown in FIG. 23, the piezoelectric thin film resonator 8 includes an adhesive layer 82, a cavity forming film 83, a lower surface electrode 84, a piezoelectric thin film 85, an upper surface electrode 86, and an additional film 87 in this order on a support substrate 81. It has a laminated structure. The piezoelectric thin film resonator 8 has the same structure as the piezoelectric thin film resonator 1 except for the upper surface electrode 86 and the additional film 87, and includes a support substrate 81, an adhesive layer 82, a cavity forming film 83, a lower surface electrode 84, a piezoelectric film. The body thin film 85 and the upper surface electrode 86 correspond to the support substrate 11, the adhesive layer 12, the cavity forming film 13, the lower surface electrode 14, the piezoelectric thin film 15 and the upper surface electrode 16 of the piezoelectric thin film resonator 1, respectively. .

The difference between the piezoelectric thin film resonator 1 and the piezoelectric thin film resonator 8 is that the piezoelectric thin film resonator 1 is obtained by further processing the conductive thin film 1602 on a part of the conductive thin film 1601 having a uniform film thickness, thereby forming a piezoelectric body. While the film thickness distribution of the upper surface electrode 16 canceling out the film thickness distribution of the thin film 15 is obtained, in the piezoelectric thin film resonator 8, a part of the upper surface electrode 86 made of a conductor thin film having a uniform film thickness is obtained. Further, the additional film 87 made of an insulator thin film is additionally processed, so that the film thickness of the laminated film 88 of the upper surface electrode 86 and the additional film 87 that cancels the film thickness distribution of the piezoelectric thin film 85 in the free vibration region 892 is reduced. The point is that the distribution is obtained. The insulating material constituting the additional film 87 is not particularly limited, but is preferably selected from insulating materials such as silicon dioxide (SiO ₂ ).

  Even if the laminated film 88 having such a film thickness distribution is employed, the piezoelectric thin film resonator 8 can be prevented from resonating at a plurality of resonance frequencies, and the piezoelectric thin film resonator 8 can be influenced by sub-resonance. It becomes difficult to receive.

<9 Ninth Embodiment>
FIG. 24 is a schematic diagram of a piezoelectric thin film resonator 9 according to a ninth embodiment of the present invention. FIG. 24 is a cross-sectional view of the piezoelectric thin film resonator 9.

  As shown in FIG. 24, the piezoelectric thin film resonator 9 has a structure in which an adhesive layer 92, a cavity forming film 93, a lower surface electrode 94, a piezoelectric thin film 95, and an upper surface electrode 96 are laminated on a support substrate 91 in this order. Have. The piezoelectric thin film resonator 9 has the same structure as the piezoelectric thin film resonator 3 except for the piezoelectric thin film 95 and the upper surface electrode 96, and includes a support substrate 91, an adhesive layer 92, a cavity forming film 93, a lower surface electrode 94, The piezoelectric thin film 95 and the upper surface electrode 96 correspond to the support substrate 31, the adhesive layer 32, the cavity forming film 33, the lower surface electrode 34, the piezoelectric thin film 35, and the upper surface electrode 36 of the piezoelectric thin film resonator 3, respectively. Yes.

  The difference between the piezoelectric thin film resonator 3 and the piezoelectric thin film resonator 9 is that in the piezoelectric thin film resonator 3, the upper surface of the piezoelectric thin film 35 is substantially flat and the lower surface of the piezoelectric thin film 35 is curved upward in the free vibration region 392. In addition, a conductor thin film 3602 is added to the central portion of the free vibration region 392 where the film thickness of the piezoelectric thin film 35 is reduced, and is superimposed on the conductor thin film 3601 having a uniform film thickness. In contrast to the film thickness distribution of the upper surface electrode 36 that cancels the film thickness distribution of the thin film 35, in the piezoelectric thin film resonator 9, the lower surface of the piezoelectric thin film 95 is curved upward in the free vibration region 962. In addition, the upper surface of the piezoelectric thin film 95 is repeatedly undulated, and is overlaid on the conductive thin film 9601 having a uniform film thickness, and the central portion of the free vibration region 962 in which the film thickness of the piezoelectric thin film 95 becomes thin is reduced. Conductor thin film 9 02 adds lies in that obtaining a film thickness distribution of the upper electrode 96 to offset the distribution of film thickness of the piezoelectric thin film 95 in the free vibration region 962.

  In the piezoelectric thin film resonator 9 in which both the upper surface and the lower surface of the piezoelectric thin film 95 are non-flat, even if the upper surface electrode 96 having such a film thickness distribution is employed, the piezoelectric thin film resonator 9 has a plurality of resonance frequencies. This makes it possible to prevent the piezoelectric thin film resonator 9 from being affected by sub-resonance.

1 is a perspective view of a piezoelectric thin film resonator according to a first embodiment of the present invention. 1 is a plan view of a piezoelectric thin film resonator according to a first embodiment of the present invention. FIG. 3 is a cross-sectional view of the piezoelectric thin film resonator taken along the line AA in FIG. 2. It is sectional drawing of a longitudinal effect vibrator. It is a circuit diagram which shows the equivalent circuit of a longitudinal effect vibrator. It is sectional drawing of the piezoelectric thin film resonator in the middle of manufacture. It is sectional drawing of the piezoelectric thin film resonator in the middle of manufacture. It is sectional drawing of the piezoelectric thin film resonator in the middle of manufacture. It is sectional drawing of the piezoelectric thin film resonator in the middle of manufacture. It is sectional drawing of the piezoelectric thin film resonator in the middle of manufacture. It is sectional drawing of the piezoelectric thin film resonator in the middle of manufacture. It is sectional drawing of the piezoelectric thin film resonator in the middle of manufacture. It is a figure which shows an example of the frequency-impedance characteristic of a piezoelectric thin film resonator. It is a figure which shows an example of the frequency-impedance characteristic of a piezoelectric thin film resonator. It is sectional drawing of the piezoelectric thin film resonator of 2nd Embodiment of this invention. It is sectional drawing of the piezoelectric thin film resonator of 3rd Embodiment of this invention. It is sectional drawing of the piezoelectric thin film resonator of 4th Embodiment of this invention. It is a figure which shows an example of the frequency-impedance characteristic of a piezoelectric thin film resonator. It is a figure which shows an example of the frequency-impedance characteristic of a piezoelectric thin film resonator. It is sectional drawing of the piezoelectric thin film resonator of 5th Embodiment of this invention. It is sectional drawing of the piezoelectric thin film resonator of 6th Embodiment of this invention. It is sectional drawing of the piezoelectric thin film resonator of 7th Embodiment of this invention. It is sectional drawing of the piezoelectric thin film resonator of 8th Embodiment of this invention. It is sectional drawing of the piezoelectric thin film resonator of 9th Embodiment of this invention.

Explanation of symbols

1, 2, 3, 4, 5, 6, 7, 8, 9 Piezoelectric thin film resonators 11, 21, 31, 41, 51, 61, 71, 81, 91 Support substrate 12, 22, 32, 42, 52, 62, 72, 82, 92 Adhesive layer 13, 23, 33, 43, 53, 63, 73, 83, 93 Cavity forming film 14, 24, 34, 44, 54, 64, 74, 84, 94 Bottom electrode 15, 25, 35, 45, 55, 65, 75, 85, 95 Piezoelectric thin film 16, 26, 36, 46, 56, 66, 76, 86, 96 Upper surface electrode 87 Additional film

Claims (6)

A piezoelectric thin film device including one or more piezoelectric thin film resonators,
A piezoelectric thin film;
An electrode film formed on both main surfaces of the piezoelectric thin film and facing the piezoelectric thin film in an opposing region;
A support substrate that supports a vibrating body in which the piezoelectric thin film and the electrode film are stacked;
With
A piezoelectric thin film device in which the electrode film has a film thickness distribution that cancels the film thickness distribution of the piezoelectric thin film in a free vibration region in which the vibrating body is separated from the support substrate by a cavity.   2. The piezoelectric thin film device according to claim 1, wherein the electrode film is formed by additionally processing a conductive thin film on a part of a conductive thin film having a uniform thickness in the free vibration region.   2. The piezoelectric thin film device according to claim 1, wherein the electrode film is formed by removing a part of a conductor thin film having a uniform thickness in the free vibration region. A piezoelectric thin film device including one or more piezoelectric thin film resonators,
A piezoelectric thin film;
An electrode film of a conductor formed on both main surfaces of the piezoelectric thin film and facing the piezoelectric thin film in an opposing region; and
An additional film of an insulator formed on the electrode film;
A support substrate for supporting a vibrating body in which the piezoelectric thin film, the electrode film, and the additional film are stacked;
With
In a free vibration region where the vibrating body is separated from the support substrate by a cavity, the laminated film of the electrode film and the additional film has a film thickness distribution that cancels the film thickness distribution of the piezoelectric thin film. Piezoelectric thin film device.   The piezoelectric thin film device according to any one of claims 1 to 4, wherein the facing region includes the free vibration region.   5. The piezoelectric thin film device according to claim 1, wherein a planar shape of the facing region is an elongated shape whose length in the longitudinal direction is twice or more the length in the lateral direction.

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