PIEZOELECTRIC THIN FILM DEVICE

Abstract

There is provided a piezoelectric thin film device with its frequency impedance characteristic unsusceptible to spuriousness.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an oblique view showing a schematic configuration of a film bulk acoustic resonator according to a first embodiment of the present invention;

FIG. 2 is a sectional view showing a cross section of the film bulk acoustic resonator along a cutting-plane line II-II of FIG. 1;

FIG. 3A is a view showing patterns of an upper electrode;

FIG. 3B is a view showing patterns of a lower electrode;

FIG. 4 is a view showing an example of shapes of drive sections;

FIG. 5 is a view showing another example of the shapes of the drive sections;

FIG. 6 is a view showing still another example of the shapes of the drive sections;

FIG. 7 is a view showing still another example of the shapes of the drive sections;

FIG. 8 is a view showing still another example of the shapes of the drive sections;

FIG. 9 is an oblique view showing a schematic configuration of a film bulk acoustic resonator according to a second embodiment of the present invention;

FIG. 10A is a view showing patterns of an upper electrode;

FIG. 10B is a view showing patterns of a lower electrode;

FIG. 11 is a view of the upper electrode and the lower electrode formed in positions displaced from positions they should be, as seen from above;

FIG. 12 is a view of another upper electrode and another lower electrode formed in positions displaced from positions they should be, as seen from above;

FIG. 13A is a view showing patterns of the upper electrode and the lower electrode in which widths in the ±Y directions of only portions of pull-out sections, which are close to drive sections, are made the same as those of the drive sections;

FIG. 13B is a view showing patterns of the lower electrode in which widths in the ±Y directions of only portions of pull-out sections, which are close to drive sections, are made the same as those of the drive sections;

FIG. 14 is an oblique view showing a schematic configuration of a film bulk acoustic resonator according to a third embodiment of the present invention;

FIG. 15 is a sectional view showing a cross section of the film bulk acoustic resonator along a cross plane line XV-XV of FIG. 14;

FIG. 16A is a view showing patterns of an upper electrode FIG. 16B is a view showing patterns of a lower electrode;

FIG. 17A is a view showing a patter of the upper electrode in which another weighted portion is further formed on the inner side of a weighted portion;

FIG. 17B is a view showing a patter of the lower electrode;

FIG. 18 is a sectional view showing the film bulk acoustic resonator in which a step-shaped weighted portion is arranged;

FIG. 19 is a sectional view showing the film bulk acoustic resonator in which a slope-shaped weighted portion is arranged;

FIG. 20 is an oblique view of a film bulk acoustic resonator according to a fourth embodiment of the present invention;

FIG. 21 is a plan view of a film bulk acoustic resonator according to the fourth embodiment of the present invention;

FIG. 22 is a sectional view showing a cross section of the film bulk acoustic resonator along a cross plane line XXII-XXII of FIG. 20;

FIG. 23 is a plan view showing the film bulk acoustic resonator in which a weighted portion is arranged across a region along the inner sides of a pair of opposite sides of a rectangular opposing region and a rectangular region of a feeding section adjacent to the opposing region;

FIG. 24 is a plan view showing the film bulk acoustic resonator in which the weighted portion is arranged across a region having an oval opening along the inner side of the rectangular opposing region and the rectangular region of the feeding section adjacent to the opposing region;

FIG. 25 is a plan view showing the film bulk acoustic resonator in which the weighted portion is arranged across a region along the inner side of the outer periphery of the rectangular opposing region and a rectangular region making up the whole of the feeding section adjacent to the opposing region;

FIG. 26 is a plan view showing the film bulk acoustic resonator in which another weighted portion is further formed on the inner side of the weighted portion;

FIG. 27 is a plan view showing the film bulk acoustic resonator in which a step-shaped weighted portion is arranged;

FIG. 28 is a sectional view showing the film bulk acoustic resonator in which a step-shaped weighted portion is arranged;

FIG. 29 is a sectional view showing the film bulk acoustic resonator in which a slope-shaped weighted portion is arranged;

FIG. 30 is an oblique view of a piezoelectric thin film filter according to a fifth embodiment of the present invention;

FIG. 31 is a plan view of the piezoelectric thin film filter according to the fifth embodiment of the present invention;

FIG. 32 is a sectional view showing a cross section of the film bulk acoustic resonator along a cross plane line XXXII-XXXII of FIG. 30;

FIG. 33 is a circuit view showing electric connection of two film bulk acoustic resonators included in the piezoelectric thin film filter;

FIG. 34 is a sectional view showing the state of separation of an assembly obtained by integrating a large number of film bulk acoustic resonators, into separate film bulk acoustic resonators;

FIGS. 35A to 35D is a view for explaining a method for manufacturing the film bulk acoustic resonator;

FIGS. 36E to 36G is a view for explaining the method for manufacturing the film bulk acoustic resonator;

FIG. 37 is a view showing a frequency impedance characteristic of a film bulk acoustic resonator of Example 1;

FIG. 38 is a view showing a frequency impedance characteristic of a film bulk acoustic resonator of Example 2;

FIG. 39 is a view showing a frequency impedance characteristic of a film bulk acoustic resonator of Comparative Example;

FIG. 40 is a view showing a distribution of amplitude of vibrations in a drive section of the film bulk acoustic resonator of Example 1;

FIG. 41 is a view showing a distribution of amplitudes of vibrations in a drive section of the film bulk acoustic resonator of Comparative Example;

FIG. 42 is a sectional view for explaining a method for manufacturing a film bulk acoustic resonator of Example 3;

FIG. 43 is a sectional view for explaining a method for manufacturing the film bulk acoustic resonator of Example 3;

FIG. 44 is a view showing a frequency impedance characteristic of the film bulk acoustic resonator of Example 3;

FIG. 45 is a view showing a frequency impedance characteristic of a film bulk acoustic resonator of Example 4;

FIG. 46 is a view showing dependency of spurious strength upon a side ratio La/Lb;

FIG. 47 is a view showing dependency of low-frequency resonant waveform strength upon the side ratio La/Lb;

FIG. 48 is a view for explaining a definition of the spurious strength;

FIG. 49 is a view for explaining a definition of the low-frequency resonant waveform strength;

FIG. 50 is a view showing the state of separation of an assembly obtained by integrating a large number of film bulk acoustic resonators, into separate film bulk acoustic resonators;

FIGS. 51A to 51D is a view for explaining a method for manufacturing a film bulk acoustic resonator according to Example 6;

FIGS. 52E to 52H is a view for explaining the method for manufacturing the film bulk acoustic resonator according to Example 6;

FIGS. 53A and 53B is a view for explaining a formation process for an upper electrode of a piezoelectric thin film filter according to Example 7;

FIG. 54 is a view showing a frequency-impedance characteristic of the film bulk acoustic resonator according to Example 6;

FIG. 55 is a view showing a frequency-impedance characteristic of a film bulk acoustic resonator according to Example 8;

FIG. 56 is a view showing frequency-attenuation characteristics of piezoelectric thin film filters according to Examples 7 and 9;

FIG. 57 is a sectional view showing the film bulk acoustic resonator in which one opposite side of a rectangular cavity is located on the inner side of an excitation region;

FIG. 58 is a sectional view showing the film bulk acoustic resonator in which both opposite sides of the rectangular cavity are located on the inner side of the excitation region; and

FIG. 59 is a view showing a schematic configuration of a main section of a conventional film bulk acoustic resonator.

Claims

1. A piezoelectric thin film device including a single or a plurality of film bulk acoustic resonators, the device comprising: a piezoelectric thin film; andelectrodes formed on respective main surfaces of said piezoelectric thin film and having drive sections opposed to each other with said piezoelectric thin film interposed therebetween, whereinsaid respective drive section has a slender two-dimensional shape with magnitude in a longitudinal direction being not less than twice as large as magnitude in a widthwise direction.

2. The piezoelectric thin film device according to claim 1, wherein said respective drive section has a slender two-dimensional shape with magnitude in the longitudinal direction being not less than four times as large as magnitude in the widthwise direction.

3. The piezoelectric thin film device according to claim 1, wherein said respective drive section has a slender two-dimensional shape with magnitude in the longitudinal direction being not less than ten times as large as magnitude in the widthwise direction.

4. The piezoelectric thin film device according to claim 1, wherein said respective drive section has a rectangular shape with a long-side length as magnitude in the longitudinal direction being not less than twice as large as a short-side length as magnitude in the widthwise direction.

5. The piezoelectric thin film device according to claim 4, wherein said respective electrode has a pull-out section for pulling out said drive section in a direction perpendicular to a predetermined direction while maintaining a width of said drive section in said predetermined direction.

6. The piezoelectric thin film device according to claim 1, wherein said respective drive section has an oval shape with a long-axis length as magnitude in the longitudinal direction being not less than twice as large as a short-axis length as magnitude in the widthwise direction.

7. The piezoelectric thin film device according to claim 1, wherein at least one of said drive sections has a weighted portion with a larger mass per unit area than that of a central portion, only along inner sides of a pair of opposite sides extending in the longitudinal direction.

8. The piezoelectric thin film device according to claim 7, wherein said respective drive section has a rectangular shape with the long-side length as magnitude in the longitudinal direction being not less than twice as large as the short-side length as magnitude in the widthwise direction, andat least one of said drive sections has said weighted portion only along the inner side of said long side.

9. The piezoelectric thin film device according to claim 1, wherein a material for said piezoelectric thin film is any one of lithium niobate and lithium tantalite.

10. The piezoelectric thin film device according to claim 1, further comprising: a support for supporting said piezoelectric thin film; andan adhesive layer for bonding said piezoelectric thin film to said support.