Piezoelectric resonator, piezoelectric filter, duplexer, communication apparatus, and method for manufacturing piezoelectric resonator
First Claim
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1. A piezoelectric resonator comprising:
- a substrate; and
a vibration portion provided on the substrate, the vibration portion including a thin film portion in which top and bottom surfaces of the thin film portion includes at least one layer of piezoelectric thin film sandwiched between at least a pair of upper and lower electrodes facing each other in a thickness direction of the thin film portion;
whereinfirst and second insulation films arranged between the substrate and the vibration portion; and
a temperature coefficient of resonant frequency of one of the first insulation film, the second insulation film, and the piezoelectric thin film and temperature coefficients of resonant frequencies of the others of the first insulation film, the second insulation film, and the piezoelectric thin film have opposite signs;
the arithmetic average surface roughness of the lower electrode is about 2.5 nm or less; and
one of the first and second insulation films primarily comprises Al2O3, and the Al2O3 includes an oxygen defect.
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Abstract
A piezoelectric thin film resonator having a stabilized temperature characteristic of resonant frequency, a method for manufacturing the same, and a communication apparatus using the piezoelectric thin film resonator are provided. The piezoelectric thin film resonator is provided with a substrate having an opening, first and second insulation films which are provided on one surface of the substrate while covering the opening and which primarily include SiO2 and Al2O3, respectively, Al2O3 having oxygen defect and being in an amorphous state, and a piezoelectric thin film which is provided on the second insulation film and is sandwiched between electrodes and which primarily includes ZnO.
96 Citations
36 Claims
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1. A piezoelectric resonator comprising:
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a substrate; and
a vibration portion provided on the substrate, the vibration portion including a thin film portion in which top and bottom surfaces of the thin film portion includes at least one layer of piezoelectric thin film sandwiched between at least a pair of upper and lower electrodes facing each other in a thickness direction of the thin film portion;
wherein first and second insulation films arranged between the substrate and the vibration portion; and
a temperature coefficient of resonant frequency of one of the first insulation film, the second insulation film, and the piezoelectric thin film and temperature coefficients of resonant frequencies of the others of the first insulation film, the second insulation film, and the piezoelectric thin film have opposite signs;
the arithmetic average surface roughness of the lower electrode is about 2.5 nm or less; and
one of the first and second insulation films primarily comprises Al2O3, and the Al2O3 includes an oxygen defect. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A piezoelectric resonator, comprising:
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a substrate;
an insulation film provided on the substrate; and
a vibration portion provided on the insulation film, the vibration portion including a thin film portion including at least one layer of piezoelectric thin film which is sandwiched between at least a pair of upper and lower electrodes which face each other in the thickness direction of the thin film;
wherein an arithmetic average surface roughness of the lower electrode is about 2.5 nm or less; and
an anti-oxidation film is arranged on the lower electrode. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36)
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Specification