JP4963229B2 - Piezoelectric thin film device - Google Patents

Description

  The present invention relates to a piezoelectric thin film device in which a plurality of piezoelectric thin film resonators are combined.

  FIGS. 14 and 15 are schematic views showing a schematic configuration of a vibration laminate 98 of a conventional piezoelectric thin film filter, FIG. 14 is a perspective view of the piezoelectric thin film filter 9, and FIG. 15 is an XV-XV of FIG. It is sectional drawing of the piezoelectric thin film filter 9 in a cutting line. For convenience of explanation, FIG. 14 defines an XYZ orthogonal coordinate system 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. 14 and 15, the piezoelectric thin film filter 9 has a structure in which a lower surface electrode 94 and an upper surface electrode 96 (961, 962) are formed on the lower surface and the upper surface of the piezoelectric thin film 95, respectively. The piezoelectric thin film filter 9 forms a piezoelectric thin film resonator by causing the lower surface electrode 94 and the upper surface electrode 961 to face each other in the facing region 991, and causes the lower surface electrode 94 and the upper surface electrode 962 to face each other in the facing region 992. Is formed as a ladder type filter combining two piezoelectric thin film resonators.

  In the piezoelectric thin film filter 9, the lower surface electrode 94 is extracted from the facing region 991 in the −Y direction, while the lower surface electrode 94 is extracted from the facing region 992 in the + Y direction. Further, the upper surface electrode 961 is extracted from the facing region 992 in the + Y direction, while the upper surface electrode 962 is extracted from the facing region 992 in the −Y direction. That is, in the piezoelectric thin film filter 9, the lead-out directions of the lower surface electrode 94 and the upper surface electrode 96 are opposite in the two piezoelectric thin film resonators.

  Patent Document 1 is a prior art document related to the present invention. A piezoelectric thin film filter in which the drawing direction of the lower surface electrode and the upper surface electrode is reversed by two piezoelectric thin film resonators is shown in FIGS. 13 and 14. Disclosure.

JP 2004-120219 A

  In the piezoelectric thin film filter, there is a case where it is desired to employ a thin film having in-plane piezoelectric anisotropy such as a single crystal thin film as the piezoelectric thin film. However, in the conventional piezoelectric thin film filter, when a thin film having in-plane piezoelectric anisotropy is adopted as the piezoelectric thin film, the lead-out directions of the lower surface electrode and the upper surface electrode are different between the two piezoelectric thin film resonators. A difference occurs in the resonance characteristics of the two piezoelectric thin film resonators, and a desired characteristic may not be obtained in the piezoelectric thin film filter in which the two piezoelectric thin film resonators are combined. This is a problem common to piezoelectric thin film filters in which three or more piezoelectric thin film resonators are combined, and more generally in general to piezoelectric thin film devices in which a plurality of piezoelectric thin film resonators are combined.

  The present invention has been made to solve this problem, and even when a thin film having in-plane piezoelectric anisotropy such as a single crystal thin film is adopted as a piezoelectric thin film, a piezoelectric thin film device having desired characteristics is manufactured. The purpose is to be able to.

In order to solve the above-described problems, the invention of claim 1 is a piezoelectric thin film device in which a plurality of piezoelectric thin film resonators are combined, and includes a piezoelectric thin film having in-plane piezoelectric anisotropy and the continuous piezoelectric thin film. An upper surface electrode and a lower surface electrode formed on the upper surface and the lower surface, respectively, and the piezoelectric thin film resonator is formed by making the upper surface electrode and the lower surface electrode face each other across the piezoelectric thin film in a plurality of opposing regions. The leading direction of the upper surface electrode from each of the facing regions is aligned with the first direction, and the leading direction of the lower surface electrode from each of the facing regions is aligned with the second direction. Further, the first direction and the second direction are opposite directions.

According to a second aspect of the present invention, the opposing regions are arranged in parallel with the same shape, the width of the upper surface electrode from each of the opposing regions is aligned, and the width of the lower surface electrode from each of the opposing regions is The piezoelectric thin film device according to claim 1 , which is aligned.

The invention according to claim 3 is the piezoelectric thin film device according to claim 1 or 2 , wherein the piezoelectric thin film is made of a single crystal material.

According to a fourth aspect of the present invention, there is provided the piezoelectric thin film device according to any one of the first to third aspects, wherein vibration is used as the vibration mode.

  According to the present invention, since the characteristics of the piezoelectric thin film resonator can be made uniform, it becomes easy to manufacture a piezoelectric thin film device having desired characteristics.

Moreover, according to the present invention , stray capacitance can be reduced.

According to the invention of claim 2 , the characteristics of the piezoelectric thin film resonator can be further aligned.

  Hereinafter, a preferred embodiment of the piezoelectric thin film device of the present invention will be described by taking as an example a piezoelectric thin film filter in which two piezoelectric thin film resonators (FBAR: Film Bulk Acoustic Resonator) that use vibration as a vibration mode are used. . However, the embodiments described below do not mean that the piezoelectric thin film device of the present invention is limited to only a piezoelectric thin film filter in which two piezoelectric thin film resonators are combined. That is, the piezoelectric thin film device in the present invention generally means a general piezoelectric thin film device in which a plurality of piezoelectric thin film resonators are combined, and includes a ladder type filter, a lattice type filter, a multimode type filter, and the like. Includes filters, duplexers, triplexers and traps. Here, the piezoelectric thin film resonator is a resonator using an electrical response by a bulk acoustic wave that is piezoelectrically excited by a thin film that cannot withstand its own weight without support.

  1 and 2 are schematic views showing a schematic configuration of the piezoelectric thin film filter 1 according to the embodiment, FIG. 1 is a perspective view of the piezoelectric thin film filter 1, and FIG. 2 is a section line II-II in FIG. It is sectional drawing of the piezoelectric thin film filter 1 in FIG. For convenience of explanation, FIG. 1 defines an XYZ orthogonal coordinate system 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 and 2, the piezoelectric thin film filter 1 includes an adhesive layer 12, a cavity forming film 13, a lower surface electrode 14 (141, 142), a piezoelectric thin film 15, and an upper surface electrode 16 ( 161, 162, 163) are stacked in this order. The piezoelectric thin film filter 1 is a monolithic ladder type filter configured by forming a lower surface electrode 14 and an upper surface electrode 16 on a lower surface and an upper surface of a continuous piezoelectric thin film 15, respectively.

  When the piezoelectric thin film filter 1 is manufactured, the piezoelectric thin film 15 is obtained by removing the piezoelectric substrate that can withstand its own weight, but the piezoelectric thin film 15 obtained by the removing process can withstand its own weight alone. Absent. For this reason, in manufacturing the piezoelectric thin film filter 1, the piezoelectric substrate on which the cavity forming film 13 and the lower surface electrode 14 are formed is bonded to the support substrate 11 in advance prior to the removal processing.

<1.1 Support substrate 11>
The support substrate 11 supports the piezoelectric substrate on which the cavity forming film 13 and the lower surface electrode 14 are formed on the lower surface via the adhesive layer 12 when the piezoelectric substrate is removed during the manufacturing process of the piezoelectric thin film filter 1. have. In addition, after the piezoelectric thin film filter 1 is manufactured, the support substrate 11 has 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 via the adhesive layer 12. It also has a supporting role. Accordingly, the support substrate 11 is required to be able to withstand the force applied when the piezoelectric substrate is removed, and not to decrease in strength even after the piezoelectric thin film filter 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 or breakage due to the difference in thermal expansion coefficient can be suppressed during the manufacturing of the piezoelectric thin film filter 1. 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.

<1.2 Adhesive layer 12>
The adhesive layer 12 serves to bond and fix the piezoelectric substrate on which the cavity forming film 13 and the lower surface electrode 14 are formed on the lower surface when the piezoelectric substrate is removed during the manufacturing process of the piezoelectric thin film filter 1. Have. In addition, after the piezoelectric thin film filter 1 is manufactured, the adhesive layer 12 is bonded and fixed to the support substrate 11 with 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. It also has a role to play. Therefore, the adhesive layer 12 is required to be able to withstand the force applied when the piezoelectric substrate is removed and that the adhesive force does not decrease even after the piezoelectric thin film filter 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 formed between the support substrate 11 and the piezoelectric substrate, and to prevent a crack or the like from being generated due to the void during the removal processing of the piezoelectric substrate. It is. 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.

<1.3 Cavity Formation Film 13>
The cavity forming film 13 is an insulator film obtained by forming an insulating material. In the piezoelectric thin film filter 1, the cavity forming film 13 is formed on the lower surface of the fixed region 193 of the vibration laminate 18 in which the lower electrode 14, the piezoelectric thin film 15 and the upper electrode 16 are stacked, and the support substrate 11, the adhesive layer 12, and the cavity forming A support 17 on which the film 13 is laminated supports the vibration laminate 18 at the outer edges of the elongated rectangular free vibration regions 191 and 192. The cavity forming film 13 that functions as a spacer forms cavities 135 and 136 below the free vibration regions 191 and 192, and the free vibration regions 191 and 192 of the vibration laminate 18 interfere with the support substrate 11. Thus, the vibration excitation in the free vibration regions 191 and 192 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 ).

<1.4 Piezoelectric thin film 15>
The piezoelectric thin film 15 is obtained by removing the piezoelectric substrate. More specifically, the piezoelectric thin film 15 removes a piezoelectric substrate having a thickness (for example, 50 μm or more) that can withstand its own weight to a thickness (for example, 10 μm or less) that cannot withstand its own weight. It can be obtained by thinning.

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 desirably a crystal orientation in which the temperature characteristics of the resonance frequency and antiresonance frequency of the piezoelectric thin film resonator constituting the piezoelectric thin film filter 1 are favorable, and the frequency temperature coefficient is “ More preferably, the crystal orientation is “0”.

  The removal processing of the piezoelectric substrate 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 filter 1 can be improved while maintaining high productivity. For example, after performing grinding in which a piezoelectric substrate is brought into contact with fixed abrasive grains and polishing in which a piezoelectric substrate is brought into contact with loose abrasive grains in order, a work-affected layer generated on the piezoelectric substrate by the polishing is finished and polished. If it removes by this, the speed at which the piezoelectric substrate is cut can be increased, the productivity of the piezoelectric thin film filter 1 can be improved, and the quality of the piezoelectric thin film 15 can be improved. The characteristics can be improved. Note that a more specific method of removing the piezoelectric substrate will be described in an example described later.

  In such a piezoelectric thin film filter 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 and the piezoelectric thin film 15 constituting the piezoelectric thin film 15 is high. Therefore, the piezoelectric thin film filter 1 can easily achieve desired characteristics.

  The piezoelectric thin film 15 has a via hole 155 that penetrates between the lower surface and the upper surface of the piezoelectric thin film 15 and connects the lower electrode 141 and the upper electrode 162 facing each other with the piezoelectric thin film 15 interposed therebetween in the fixed region 193. In the fixed region 193, the lower surface electrode 142 and the upper surface electrode 163 that are opposed to each other with the piezoelectric thin film 15 interposed therebetween are formed.

<1.5 Lower electrode 14 and upper electrode 16>
The lower surface electrode 14 and the upper surface electrode 16 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 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.

  As shown in the plan view of FIG. 3 showing a pattern of the lower surface electrode 14 and the upper surface electrode 16 viewed from above in addition to FIGS. 1 and 2, the lower surface electrode 141 and the upper surface electrode 161 are included in the free vibration region 191. A thin thin film resonator (series resonator) 1001 shown in the circuit diagram of FIG. 4 is formed by facing the piezoelectric thin film 15 in an elongated rectangular shape facing region 196 (region specified by solid line hatching). Yes. In the piezoelectric thin film resonator 1001, the lower surface electrode 141 is drawn from the facing region 196 in the −Y direction, and the upper surface electrode 161 is drawn from the facing region 196 in the + Y direction, and then the stretching direction is in the + X direction and the −Y direction. The pad 1011 is bent sequentially and part thereof is connected to the outside.

  Further, the lower surface electrode 142 and the upper surface electrode 162 are opposed to each other with the piezoelectric thin film 15 interposed therebetween in an elongated rectangular opposing region (region specified by solid line hatching) 197 in the free vibration region 192, as shown in FIG. A piezoelectric thin film resonator (parallel resonator) 1002 shown in the circuit diagram of FIG.

  In the piezoelectric thin film resonator 1002, the lower surface electrode 142 is extracted from the opposing region 197 in the −Y direction, and the upper surface electrode 162 is extracted from the opposing region 197 in the + Y direction, and then the extending direction is in the + X direction and the −Y direction. The pad 1013 is bent sequentially and part thereof is connected to the outside.

  That is, the piezoelectric thin film filter 1 is the piezoelectric thin film resonators 1001 and 1002, and the lead-out directions of the lower surface electrodes 141 and 142 from the opposing regions 196 and 197 are aligned in the + Y direction, and the upper surface electrodes 161 and 162 from the opposing regions 196 and 197 are aligned. Electrode pattern in which the lead-out direction is aligned in the -Y direction. When such an electrode pattern is employed, even when the piezoelectric thin film 15 having in-plane piezoelectric anisotropy such as a single crystal thin film is employed, the characteristics of the piezoelectric thin film resonators 1001 and 1002 (for example, resonance frequency and antiresonance). (Difference with frequency) can be made uniform, so that it is easy to manufacture a piezoelectric thin film filter having desired characteristics.

  The lower surface electrode 141 and the upper surface electrode 162 are opposed to each other across the piezoelectric thin film 15 in a facing region (region specified by dotted hatching) 198 in the fixed region 193 and are short-circuited by a via hole 155. In addition, the lower surface electrode 142 and the upper surface electrode 163 are opposed to each other with the piezoelectric thin film 15 interposed therebetween in an opposing region (region specified by dotted hatching) 199 in the fixed region 193 and short-circuited by the via hole 156. Yes. A part of the upper surface electrode 163 serves as pads 1012 and 1014 connected to the outside.

  With such an electrode pattern, the piezoelectric thin film filter 1 functions as a bidirectional filter having the pads 1011 and 1012 as input terminal pairs and the pads 1013 and 1014 as output terminal pairs, and the series resonator 1001 and the parallel resonator 1012. It exhibits filtering characteristics according to the resonance characteristics of the thickness longitudinal vibration mode and thickness shear vibration mode.

  From the viewpoint of making the characteristics of the piezoelectric thin film resonators 1001 and 1002 uniform, it is most desirable that the patterns of the lower surface electrodes 141 and 142 are exactly the same and the patterns of the upper surface electrodes 161 and 162 are the same. However, if the piezoelectric thin film resonators 1001 and 1002 are energy confinement type resonators, the influence of the electrode pattern on the characteristics of the piezoelectric thin film resonators 1001 and 1002 decreases as the distance from the opposing regions 196 and 197 increases. It is practically sufficient if the patterns of the lower surface electrodes 141 and 142 are made the same and the patterns of the upper surface electrodes 161 and 162 are made the same only in the opposing regions 196 and 197 and the vicinity thereof. Therefore, in the piezoelectric thin film filter 1, the patterns of the upper surface electrodes 161 and 162 are not exactly the same, but the opposing regions 196 and 197 are arranged in parallel as the same elongated rectangular shape, and the lower surface electrodes 141 and 141 from the opposing regions 196 and 197 are arranged. By aligning the lead-out width 142 (length in the direction perpendicular to the lead-out direction) and aligning the lead-out widths of the upper surface electrodes 161 and 162 from the opposing regions 196 and 197, the piezoelectric thin film resonators 1001 and 1002 have a difference in characteristics. It is prevented from occurring.

  Further, it is desirable that the lead-out direction of the lower surface electrodes 141 and 142 and the lead-out direction of the upper surface electrodes 161 and 162 are opposite to each other as shown in FIG. If the direction is opposite, the stray capacitance can be reduced, so that the anti-resonance frequency of the piezoelectric thin film resonators 1001 and 1002 is lowered, the pass band width of the piezoelectric thin film filter 1 is narrowed, and the signal of the stop band frequency This is because it is possible to prevent the amount of out-of-band suppression of the piezoelectric thin film filter 1 from being reduced. However, this does not prevent the angle formed between the lead-out direction of the lower surface electrodes 141 and 142 and the lead-out direction of the upper surface electrodes 161 and 162 from being other than 180 °, for example, 90 °.

<1.6 Other>
In the above description, the case where the present invention is applied to an L-type ladder filter has been described. However, the present invention can also be applied to T-type, π-type ladder filters, lattice filters, and multimode filters. The number of resonators constituting the filter is not particularly limited.

  Examples according to preferred embodiments of the present invention will be described below.

  In this embodiment, a single crystal of lithium niobate is used as the piezoelectric material constituting the support substrate 11 and the piezoelectric thin film 15, an epoxy adhesive is used as the material constituting the adhesive layer 12, and silicon dioxide is used as the insulating material constituting the cavity forming film 13. The piezoelectric thin film filter 1 was manufactured using tungsten as the conductive material constituting the lower surface electrode 14 and the upper surface electrode 16.

  As shown in the cross-sectional view of FIG. 5, the piezoelectric thin film filter 1 according to the example is manufactured by manufacturing a mother substrate 1 m in which a large number of piezoelectric thin film filters 1 are integrated in order to reduce the manufacturing cost. It is manufactured by cutting into individual piezoelectric thin film filters 1 by cutting with a dicing saw. FIG. 5 shows an example in which three piezoelectric thin film filters 1 are included in the mother substrate 1m, but the number of piezoelectric thin film filters 1 included in the mother substrate 1m is four or more. Well, typically speaking, the mother substrate 1m includes several hundred to several thousand piezoelectric thin film filters 1.

  In the following, for the sake of convenience, the description will be focused on one piezoelectric thin film filter 1 included in the mother substrate 1m, but other piezoelectric thin film filters 1 included in the mother substrate 1m are also parallel to the focused piezoelectric thin film filter 1. Manufactured.

  Then, the manufacturing method of the piezoelectric thin film filter 1 which concerns on an Example is demonstrated, referring sectional drawing of FIGS.

  In manufacturing the piezoelectric thin film filter 1, first, a circular wafer (45 ° cut Y plate) of lithium niobate single crystal having a thickness of 0.5 mm and a diameter of 3 inches was prepared as the support substrate 11 and the piezoelectric substrate 916.

  Subsequently, a tungsten film having a thickness of 1000 angstroms is formed on the lower surface of the piezoelectric substrate 916 by sputtering, and the obtained tungsten film is patterned by using a general photolithography technique, so that the pattern shown in FIG. 3 is obtained. A piezoelectric substrate 916 having a lower electrode 14 having the same was obtained (FIG. 6).

  Then, a silicon dioxide film having a thickness of 0.5 μm is formed on the lower surface of the piezoelectric substrate 916 by sputtering, and the obtained silicon dioxide film is patterned by using a general photolithography technique, so that the fixed region 193 is formed. The silicon dioxide film formed in the free vibration regions 191 and 192 was removed while leaving the formed silicon dioxide film (FIG. 7). As a result, the cavity forming film 13 is formed on the piezoelectric substrate 916.

  Here, an epoxy adhesive serving as the adhesive layer 12 is applied to the upper surface of the support substrate 11 (FIG. 8), and the upper surface of the support substrate 11 and the lower surface of the piezoelectric substrate 916 on which the lower electrode 14 and the cavity forming film 13 are formed. And pasted together. Then, pressure was applied to the support substrate 11 and the piezoelectric substrate 916 to perform press-bonding, and the film thickness of the adhesive layer 12 was set to 0.5 μm. Thereafter, the bonded support substrate 11 and piezoelectric substrate 916 were allowed to stand in an environment of 200 ° C. for 1 hour to cure the epoxy adhesive, thereby bonding the support substrate 11 and the piezoelectric substrate 916 (FIG. 9). As a result, cavities 135 and 136 having a depth of 0.5 μm were formed below the free vibration regions 191 and 192 of the piezoelectric substrate 916.

  After the bonding between the support substrate 11 and the piezoelectric substrate 916 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 916 is bonded to the support substrate 11. The upper surface of 916 was ground with a fixed abrasive grinder to reduce the thickness of the piezoelectric substrate 916 to 50 μm. Further, the upper surface of the piezoelectric substrate 916 was polished with diamond abrasive grains, and the thickness of the piezoelectric substrate 916 was reduced to 2 μm. Finally, in order to remove the work-affected layer generated on the piezoelectric substrate 916 by polishing with diamond abrasive grains, the piezoelectric substrate 916 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 1 μm was obtained (FIG. 10).

  Next, the upper surface of the piezoelectric thin film 15 is washed with an organic solvent, a chromium film and a gold film are sequentially formed on the upper surface of the piezoelectric thin film 15 by sputtering, and the obtained laminated film is subjected to a general photolithography technique. The etching mask 918 exposing only the region where the via holes 155 and 156 are to be formed was formed by patterning using the etching mask (FIG. 11). After that, the piezoelectric thin film 15 was etched with a 1: 1 buffered hydrofluoric acid aqueous solution at a temperature of 60 ° C. to form via holes 155 and 156 to expose the lower surface electrode 14 (FIG. 12).

  Then, a tungsten film having a film thickness of 1000 angstroms is formed on the upper surface of the piezoelectric thin film 15 by sputtering, and the obtained tungsten film is patterned using a general photolithography technique, thereby having the pattern shown in FIG. A top electrode 16 was obtained (FIG. 13). At this time, since the tungsten film is also formed on the inner side surfaces of the via holes 155 and 156, conduction between the lower surface electrode 14 and the upper surface electrode 16 is ensured.

1 is a perspective view showing a schematic configuration of a piezoelectric thin film filter according to a preferred embodiment of the present invention. It is sectional drawing which shows schematic structure of the piezoelectric thin film filter which concerns on desirable embodiment of this invention. It is a top view which shows the pattern which looked at the lower surface electrode and the upper surface electrode from upper direction. It is a circuit diagram of a piezoelectric thin film filter. It is sectional drawing which shows a mode that a mother board | substrate is cut | disconnected and isolate | separated into each piezoelectric thin film filter. It is sectional drawing which shows the state which formed the lower surface electrode in the piezoelectric material board | substrate. It is sectional drawing which shows the state which formed the cavity formation film in the piezoelectric material board | substrate. It is sectional drawing which shows the state which apply | coated the adhesive layer to the support substrate. It is sectional drawing which shows the state which adhere | attached the support substrate and the piezoelectric material board | substrate. It is sectional drawing which shows the state which made the piezoelectric material thin film the piezoelectric material thin film. It is sectional drawing which shows the state which formed the etching mask in the piezoelectric material thin film. It is sectional drawing which shows the state which formed the via hole in the piezoelectric material thin film. It is sectional drawing which shows the state which formed the upper surface electrode in the piezoelectric material thin film. It is a perspective view which shows schematic structure of the principal part of the conventional piezoelectric thin film filter. It is sectional drawing which shows schematic structure of the principal part of the conventional piezoelectric thin film filter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piezoelectric thin film filter 14,141,142 Lower surface electrode 15 Piezoelectric thin film 16,161,162,163 Upper surface electrode 196,197 Opposite area | region

Claims (4)

A piezoelectric thin film device combining a plurality of piezoelectric thin film resonators,
A piezoelectric thin film having in-plane piezoelectric anisotropy;
An upper surface electrode and a lower surface electrode respectively formed on the upper surface and the lower surface of the continuous piezoelectric thin film;
With
Forming the piezoelectric thin film resonator by causing the upper surface electrode and the lower surface electrode to face each other across the piezoelectric thin film in a plurality of opposing regions;
Aligning the leading direction of the upper surface electrode from each of the opposing regions to the first direction, aligning the leading direction of the lower surface electrode from each of the opposing regions to the second direction ,
The piezoelectric thin film device, wherein the first direction and the second direction are opposite directions . 2. The opposing regions are arranged in parallel in the same shape, the leading electrode widths from the opposing regions are aligned, and the leading electrode widths from the opposing regions are aligned. Piezoelectric thin film device. The piezoelectric thin film device according to claim 1, wherein the piezoelectric thin film is made of a single crystal material. The piezoelectric thin film device according to any one of claims 1 to 3, wherein vibration is used as a vibration mode.

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