JP5047660B2 - Piezoelectric thin film device - Google Patents

Description

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

  2. Description of the Related Art A piezoelectric thin film resonator (FBAR) has a structure in which electrodes are formed on both main surfaces of a piezoelectric thin film supported by a support, and the electrodes are opposed to each other with the piezoelectric thin film interposed therebetween. The piezoelectric thin film resonator is a resonator using an electrical response due to thickness longitudinal vibration excited in a facing region where electrodes face each other with a piezoelectric thin film interposed therebetween.

  However, in the piezoelectric thin film resonator, the elastic wave propagating in the spreading direction of the piezoelectric thin film may be reflected on the outer surface of the opposing region to cause a standing wave, which may cause sub-resonance. In order to solve this sub-resonance problem, a piezoelectric thin film resonator in which the planar shape of the opposing region is an irregular shape is introduced in Patent Document 1.

JP 2000-332568 A

  However, although the piezoelectric thin film resonator of Patent Document 1 can surely suppress the sub-resonance, it has a problem that the effect is insufficient. The present invention has been made to solve this problem, and an object thereof is to effectively suppress the sub-resonance of the piezoelectric thin film resonator and improve the characteristics of the piezoelectric thin film device.

In order to solve the above-described problems, the invention of claim 1 is a piezoelectric thin film device including one or more piezoelectric thin film resonators, which are formed on both main surfaces of the piezoelectric thin film and the piezoelectric thin film, respectively. And a support for supporting the piezoelectric thin film, and the planar shape of the free vibration region in which the piezoelectric thin film is separated from the support is non-circular. Thus, it does not substantially include a parallel portion having a continuous contour that defines the planar shape of the free vibration region. The contour that defines the planar shape of the free vibration region is a waveform. The free vibration region includes the facing region. There is a contour that defines the planar shape of the free vibration region at a position where an elastic wave that leaks from the facing region and propagates in the spreading direction of the piezoelectric thin film can reach, and the contour that defines the planar shape of the free vibration region Elastic waves are reflected.

  According to a second aspect of the present invention, the contour defining the planar shape of the free vibration region does not substantially include a continuous parallel portion parallel to the contour defining the planar shape of the opposing region. It is a thin film device.

  According to a third aspect of the present invention, the contour defining the planar shape of the free vibration region includes a plurality of straight sections, and each of the plurality of straight sections is non-parallel to each other. The piezoelectric thin film device described in 1.

The invention according to claim 4 is the piezoelectric thin film device according to claim 1 or 2, wherein a contour defining a planar shape of the free vibration region includes a curved section.

A fifth aspect of the present invention is the piezoelectric thin film device according to the first aspect, wherein a planar shape of the free vibration region does not have a rotational symmetry axis C _n (n ≧ 2).

A sixth aspect of the present invention is the piezoelectric thin film device according to any one of the first to fifth aspects, wherein the electrodes are formed on both flat main surfaces of the piezoelectric thin film .

  ADVANTAGE OF THE INVENTION According to this invention, the subresonance of a piezoelectric thin film resonator can be suppressed effectively, and the characteristic of a piezoelectric thin film device can be improved.

  According to invention of Claim 2, the characteristic of a piezoelectric thin film device can further be improved.

<1.1 Overall structure>
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 to 3 are schematic views of the piezoelectric thin film resonator 1. 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 taken along the section line III-III in FIG. It has become. 1 to 3, a common XYZ orthogonal coordinate system is defined in which the left-right direction is the X-axis direction, the front-rear direction is the Y-axis direction, and the up-down direction is the Z-axis direction.

  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 an upper surface electrode 16 (161, 162) on a support substrate 11. Are stacked in this order. When the piezoelectric thin film resonator 1 is manufactured, the piezoelectric thin film 15 is obtained by removing a piezoelectric substrate 17 (described later) that can withstand its own weight, but the piezoelectric thin film 15 obtained by the removing process is independent. I can't stand my own weight. For this reason, when the piezoelectric thin film resonator 1 is manufactured, the piezoelectric substrate 17 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 17 is removed during the manufacturing process of the piezoelectric thin film resonator 1, the support substrate 11 has the piezoelectric substrate 17 on which the cavity forming film 13 and the lower surface electrode 14 are 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 electrode 16 formed on the upper surface via the adhesive layer 12. It also has a role as a support body that supports. Therefore, the support substrate 11 is required to be able to withstand the force applied when the piezoelectric substrate 17 is removed, and that the strength does not decrease after the piezoelectric thin film resonator 1 is manufactured.

  The material and thickness of the support substrate 11 can be appropriately selected so as to satisfy such requirements. 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>
The adhesive layer 12 adheres and fixes the piezoelectric substrate 17 having the cavity forming film 13 and the lower surface electrode 14 formed on the lower surface to the support substrate 11 when the piezoelectric substrate 17 is removed during the manufacturing of the piezoelectric thin film resonator 1. Have a role to play. In addition, after the piezoelectric thin film resonator 1 is manufactured, the adhesive layer 12 bonds the piezoelectric thin film 15 having the cavity forming film 13 and the lower electrode 14 formed on the lower surface and the upper electrode 16 formed on the upper surface to the support substrate 11. It also has a fixing role. Therefore, the adhesive layer 12 is required to be able to withstand the force applied when the piezoelectric substrate 17 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 17 and to cause a crack or the like when the piezoelectric substrate 17 is removed by the gap. 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 facing region 191, and forms a cavity 135 that separates the piezoelectric thin film 15 from the support substrate 11 in the free vibration region 192. Due to the cavity forming film 13 serving as such a spacer, the piezoelectric thin film 15 does not interfere with the support substrate 11 in the free vibration region 192, and excitation in the opposing region 191 is not hindered.

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 17. More specifically, the piezoelectric thin film 15 removes the piezoelectric substrate 17 having a thickness that can withstand its own weight (for example, 50 μm or more) to a film 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 17 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 grinding in which the piezoelectric substrate 17 is brought into contact with fixed abrasive grains and polishing in which the piezoelectric substrate 17 is brought into contact with loose abrasive grains are sequentially performed, a work-affected layer generated on the piezoelectric substrate 17 by the polishing. Is removed by finish polishing, the speed of cutting the piezoelectric substrate 17 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 to connect the lower electrode 14 and the upper electrode 162 facing each other with the piezoelectric thin film 15 interposed therebetween. Yes. The via hole 155 electrically connects the lower electrode 14 and the upper electrode 162 with a conductive thin film formed on the inner surface thereof.

<1.6 Bottom electrode and top electrode>
The lower electrode 14 and the upper electrode 16 are conductor thin films formed by depositing a conductive material on the flat and polished lower and upper surfaces of the piezoelectric thin film 15, respectively. Here, the “lower surface” and the “upper surface” of the piezoelectric thin film 15 are in a state where there is no unevenness exceeding the surface roughness inevitably remaining after polishing. In order to form the lower electrode 14 on the flat lower surface of the piezoelectric thin film 15 and to form the upper electrode 16 on the flat upper surface of the piezoelectric thin film 15, the lower electrode 14 and the upper electrode 16 are formed by photolithography. In this case, there is an advantage that the dimensional accuracy of the upper surface electrode 14 and the lower surface electrode 16 can be improved. Such an effect of improving the dimensional accuracy can be obtained if the contours of the lower surface electrode 14 and the upper surface electrode 16 are located on flat portions of the lower surface and the upper surface of the piezoelectric thin film 15.

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

  4 and 5 are diagrams showing patterns of the lower surface electrode 14 and the upper surface electrode 16, respectively. 4 and 5 also define an XYZ orthogonal coordinate system common to FIGS.

  As shown in FIGS. 2, 4, and 5, the elongated pentagonal drive unit 141 occupying a part of the lower surface electrode 14 is an elongated pentagonal drive unit 1611 occupying a part of the upper surface electrode 161 in the opposing region 191. And the piezoelectric thin film 15 therebetween. The power feeding portion 144 occupying the remainder of the lower surface electrode 141 excluding the driving portion 1411 is connected to the upper surface electrode 162 by a via hole 155.

  With such a pattern of the lower surface electrode 14 and the upper surface electrode 16, in the piezoelectric thin film resonator 1, when an excitation signal is applied to the upper surface electrode 161 exposed to the outside and the power feeding portion 1622 of the upper surface electrode 162, the lower surface electrode The excitation signal is supplied to the drive unit 141 of 14 and the drive unit 1611 of the upper surface electrode 161, and vibration is excited in the facing region 191. Thereby, the piezoelectric thin film resonator 1 functions as an energy confinement type resonator using thickness longitudinal vibration or thickness shear vibration.

<1.7 Planar shape of free vibration region and opposing region>
In the piezoelectric thin film resonator 1, as shown in FIG. 2, the planar shape of the cavity 133, that is, the free vibration region 192 in which the piezoelectric thin film 15 in which the lower electrode 14 and the upper electrode 16 are formed is separated from the support substrate 11. The planar shape is a pentagon, and the five sides 135 to 139 constituting the pentagonal outline 134 are not parallel to each other.

  This is because the acoustic impedance of the piezoelectric thin film 15 is greatly different between the inner side and the outer side of the free vibration region 192, and the portion that is the contour 134 is in a state close to the fixed end. If the planar shape of the free vibration region 192 is a polygon having a part parallel to the contour (having parallel sides), it propagates in the spreading direction of the piezoelectric thin film leaked from the facing region 191 included in the free vibration region 192. The transverse mode is easily excited between parallel sides of the free vibration region 192, and becomes a secondary resonance (spurious) with respect to the thickness longitudinal vibration mode. However, as shown in FIG. 2, when the planar shape of the free vibration region 192 is a pentagon, the transverse mode is less likely to be excited (the transverse mode Q is reduced), and the secondary resonance with respect to the thickness longitudinal vibration mode is suppressed. Become so.

  From this point of view, the planar shape of the free vibration region 192 does not need to be a pentagon, and may be a triangle, a quadrangle, a hexagon, a heptagon, or the like as long as it does not have parallel sides. That is, it may be a polygon whose outline is composed of four or less or six or more sides.

  Also, it is not essential that the planar contour of the free vibration region 192 is composed only of sides (straight line segments), and if it does not include a continuous parallel portion, as shown in FIG. 235 and the straight line sections 236 to 239 may be configured, or as illustrated in FIG. 7, only the curved line sections 335 to 339 may be configured.

  Here, “does not include a continuous parallel part” means that a part parallel to a specific part of the contour does not continue. Therefore, as shown in FIG. 8, even if there are a plurality of portions (for example, points 436 to 438) parallel to a specific portion (for example, point 439) of the waveform contour 335, it is problematic if they are not continuous. Must not.

  Whether or not to include a continuous parallel portion should be determined based on whether or not the continuous parallel portion is substantially included. That is, even if the contour includes a very short continuous portion (approximately 3% or less of the total length of the contour) that does not substantially affect the characteristics of the piezoelectric thin film resonator 1, Should not be included.

Furthermore, in order to cancel the degeneration of the sub-resonance and lower the strength of the sub-resonance, it is desirable that the symmetry of the planar shape of the free vibration region 192 is low. More specifically, it is desirable not to have a rotational symmetry axis C _n (n ≧ 2) perpendicular to the planar shape. Therefore, from the polygon having an axis of rotational symmetry C _{n (n} ≧ 2) is polygonal having no axis of rotational symmetry C _{n (n} ≧ 2) is desirable. In addition, it is not desirable that the planar shape of the free vibration region 192 is a circle having an infinite symmetry axis _C∞ , and is preferably non-circular.

  In addition, in the piezoelectric thin film resonator 1, the planar shape of the facing region 191 and the planar shape of the free vibration region 192 are dissimilar, and each of the five sides 135 to 139 constituting the contour 134 is opposed to each other. None of the five sides 195 to 199 constituting the outline 194 of the planar shape (pentagon) of the region 191 is non-parallel. In this way, if the contour 194 does not include a continuous parallel portion parallel to the contour 134, the sub-resonance can be more strongly suppressed. Here, the fact that the continuous parallel portion is not included should be determined based on whether or not the continuous parallel portion is substantially included, as described above, and the piezoelectric thin film resonator 1 Even if the contour contains a very short continuous portion (approximately 3% or less of the total length of the contour) that does not substantially affect the characteristics of the contour, it should be regarded as "not including the continuous parallel portion" is there.

  The planar shape of the facing region 191 is the same as the planar shape of the free vibration region 192. That is, it is desirable that the planar shape of the facing region 191 is also a non-circular shape having a contour that does not substantially include a continuous parallel portion. However, this does not prevent the opposing region 191 from having a planar shape of a circle, a square, a rectangle, or the like.

  In the above description, the free vibration region 192 includes the opposing region 191, but the present invention is also applicable when a part of the opposing region 191 is outside the free vibration region 192.

<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 tungsten is used as the conductive material constituting the electrode 14 and 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 17, and the lower electrode 14, the piezoelectric thin film 15, and the upper electrode 16 are sputtered on the substrate as conventionally performed. The piezoelectric thin film resonator 1 may be manufactured by sequentially forming a film by the additional 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 and the frequency adjustment described above is performed, 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 tungsten film is formed on the entire lower surface of the piezoelectric substrate 17 by sputtering, and patterning is performed using a general photolithography process, so that the pattern shown in FIG. A bottom electrode 14 having the same is obtained (FIG. 9).

  Subsequently, a silicon dioxide film is formed on the entire lower surface of the piezoelectric substrate 17 by sputtering, and patterning is performed using a general photolithography process to form a cavity forming film 13 (FIG. 10).

  Subsequently, an epoxy adhesive serving as an 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 17 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 17 to perform press-bonding. Thereafter, the epoxy adhesive is cured to bond the support substrate 11 and the piezoelectric substrate 17 (FIG. 11).

  After the bonding between the support substrate 11 and the piezoelectric substrate 17 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 17 is bonded to the support substrate 11. The upper surface of 17 is ground with a fixed abrasive grinder to thin the piezoelectric substrate 17. Further, the upper surface of the piezoelectric substrate 17 is polished with diamond abrasive grains to further reduce the thickness of the piezoelectric substrate 17. Finally, in order to remove the work-affected layer generated on the piezoelectric substrate 17 by the polishing process using diamond abrasive grains, the piezoelectric substrate 17 is subjected to final polishing using the free abrasive grains and the non-woven cloth polishing pad. A piezoelectric thin film 15 having a film thickness of is obtained (FIG. 12).

  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 the process, an etching mask 18 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. 13).

  After the formation of the etching mask 18, the piezoelectric thin film 15 is etched with heated buffered hydrofluoric acid to form a via hole 155 that penetrates between the upper and lower surfaces of the piezoelectric thin film 15 to expose the lower electrode 14. At the same time, the etching mask 18 was removed by etching (FIG. 14).

  Then, a tungsten film is formed on the entire upper surface of the piezoelectric substrate 17 by sputtering, and patterning is performed using a general photolithography process to obtain the upper surface electrode 16 having the pattern shown in FIG. 5 (FIG. 15). Thereby, the piezoelectric thin film resonator 1 is manufactured.

<1.9 Suppression Effect of Sub-Resonance by Planar Shape of Free Vibration Region>
FIGS. 16 and 17 are diagrams showing the frequency impedance characteristic and the phase impedance characteristic of the piezoelectric thin film resonator when the planar shape of the free vibration region 192 is the pentagon and the rectangle, respectively. FIGS. 18 and 19 are diagrams showing the movement of the voltage reflection coefficient of the piezoelectric thin film resonator on the Smith chart when the planar shape of the free vibration region 192 is the pentagon and the rectangle, respectively. is there.

  As shown in FIGS. 18 and 19, when the planar shape of the free vibration region 192 is rectangular, the sub-resonance is superimposed between the resonance frequency and the anti-resonance frequency or on the higher frequency side than the anti-resonance frequency ( These sub-resonances can be suppressed by making the planar shape of the free vibration region 192 a pentagon, as indicated by the arrows in FIGS. Such a sub-resonance suppressing effect can be obtained not only when the planar shape of the free vibration region 192 is a pentagon but also when the shape is as described above.

1 is a perspective view of a piezoelectric thin film resonator according to a preferred embodiment of the present invention. It is a top view of a piezoelectric thin film resonator. FIG. 3 is a cross-sectional view of the piezoelectric thin film resonator taken along a cutting line indicated by III-III in FIG. 2. It is a figure which shows the pattern of a lower surface electrode. It is a figure which shows the pattern of an upper surface electrode. It is a figure which shows the example of the planar shape of a cavity. It is a figure which shows the example of the planar shape of a cavity. It is a figure which shows the example of the planar shape of a cavity. 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 the frequency impedance characteristic of a piezoelectric thin film resonator. It is a figure which shows the frequency impedance characteristic of a piezoelectric thin film resonator. It is a figure which shows the motion on the Smith chart of the voltage reflection coefficient of a piezoelectric thin film resonator. It is a figure which shows the motion on the Smith chart of the voltage reflection coefficient of a piezoelectric thin film resonator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piezoelectric thin film resonator 11 Support substrate 12 Adhesive layer 13 Cavity formation film 14 Lower surface electrode 15 Piezoelectric thin film 16 Upper surface electrode 133 Cavity 191 Opposite area 192 Free vibration area

Claims (6)

A piezoelectric thin film device including one or more piezoelectric thin film resonators,
A piezoelectric thin film;
Electrodes formed respectively on both main surfaces of the piezoelectric thin film and facing each other with the piezoelectric thin film interposed therebetween in an opposing region;
A support for supporting the piezoelectric thin film;
With
The planar shape of the free vibration region piezoelectric thin film is spaced apart from the support is a non-circular, free of parallel portions contour defining the planar shape of the free vibration region is continuous in substantially the free The contour that defines the planar shape of the vibration region is a waveform,
The free vibration region includes the opposing region;
There is a contour that defines the planar shape of the free vibration region at a position where an elastic wave that leaks from the facing region and propagates in the spreading direction of the piezoelectric thin film can reach, and the contour that defines the planar shape of the free vibration region Piezoelectric thin film devices that reflect elastic waves.   2. The piezoelectric thin film device according to claim 1, wherein a contour defining a planar shape of the free vibration region does not substantially include a continuous parallel portion parallel to a contour defining a planar shape of the opposing region.   3. The piezoelectric thin film device according to claim 1, wherein a contour defining a planar shape of the free vibration region includes a plurality of linear sections, and each of the plurality of linear sections is non-parallel to each other.   The piezoelectric thin film device according to claim 1, wherein a contour defining a planar shape of the free vibration region includes a curved section. 2. The piezoelectric thin film device according to claim 1, wherein a planar shape of the free vibration region does not have a rotational symmetry axis C _n (n ≧ 2).   The piezoelectric thin film device according to any one of claims 1 to 5, wherein the electrodes are formed on both flat main surfaces of the piezoelectric thin film.

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