Tunable thin film acoustic resonators and method for making the same
First Claim
1. A high-Q, acoustical resonator, comprising:
- a bottom electrode layer having an ordered structure, a thickness and an acoustical attenuation;
a thin-film PZ layer comprising AlN deposited on said lower electrode layer with an ordered structure imparted thereon by said ordered structure of said lower electrode layer, said PZ layer having a top surface and a thickness; and
a top electrode layer adjacent to said top surface of said PZ layer, the top electrode layer having a thickness and an acoustical attenuation,wherein;
the top electrode layer, the PZ layer, and the bottom electrode layer collectively consitute an acoustic path having a Q, the top electrode layer and the bottom electrode layer each having a thickness relative to the thickness of the PZ layer such that the top electrode layer and the bottom electrode layer collectively constitute such a proportion of the acoustic path that the top electrode layer and the bottom electrode layer having a high acoustical attenuation causes the acoustic path to have a low Q, andboth of said top electrode layer and said bottom electrode layer consist essentially of at least one metal chosen from the group consisting of Mo and W to minimize the acoustical attenuation of said top electrode layer and said bottom electrode layer, and thereby to maximize the Q of the acoustical resonator.
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Abstract
An acoustical resonator comprising top and bottom electrodes that sandwich a PZ layer. The resonance frequency of the acoustical resonator may be adjusted after fabrication by utilizing heating elements included in the acoustical resonator and/or by adjusting the thickness of a tuning layer. In the preferred embodiment of the present invention, the electrodes comprise Mo layers. One embodiment of the present invention is constructed on a Si3 N4 membrane. A second embodiment of the present invention is constructed such that it is suspended over a substrate on metallic columns. In the preferred embodiment of the present invention, the electrodes are deposited by a method that minimizes the stress in the electrodes.
388 Citations
25 Claims
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1. A high-Q, acoustical resonator, comprising:
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a bottom electrode layer having an ordered structure, a thickness and an acoustical attenuation; a thin-film PZ layer comprising AlN deposited on said lower electrode layer with an ordered structure imparted thereon by said ordered structure of said lower electrode layer, said PZ layer having a top surface and a thickness; and a top electrode layer adjacent to said top surface of said PZ layer, the top electrode layer having a thickness and an acoustical attenuation, wherein; the top electrode layer, the PZ layer, and the bottom electrode layer collectively consitute an acoustic path having a Q, the top electrode layer and the bottom electrode layer each having a thickness relative to the thickness of the PZ layer such that the top electrode layer and the bottom electrode layer collectively constitute such a proportion of the acoustic path that the top electrode layer and the bottom electrode layer having a high acoustical attenuation causes the acoustic path to have a low Q, and both of said top electrode layer and said bottom electrode layer consist essentially of at least one metal chosen from the group consisting of Mo and W to minimize the acoustical attenuation of said top electrode layer and said bottom electrode layer, and thereby to maximize the Q of the acoustical resonator. - View Dependent Claims (2, 3, 4)
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5. An acoustical resonator, comprising:
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a thin-film PZ layer having top and bottom surfaces; a bottom electrode layer adjacent to said bottom surface of said PZ layer; a top electrode layer adjacent to said top surface of said PZ layer, said top electrode layer, said PZ layer, and said bottom electrode layer collectively constituting a structure having a resonant frequency, said resonant frequency depending on a temperature of said PZ layer; a layer of Si3 N4 adjacent to said bottom electrode layer, said bottom electrode being sandwiched between said layer of Si3 N4 and said PZ layer; and heating means for increasing said temperature of said PZ layer to a predetermined temperature whereat said resonant frequency is equal to a predetermined frequency, said heating means additionally indicating said temperature of said PZ layer. - View Dependent Claims (6, 7)
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8. An acoustical resonator, comprising:
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a thin-film PZ layer comprising AlN and having top and bottom surfaces; a bottom electrode layer adjacent to said bottom surface of said PZ layer; a top electrode layer adjacent to said top surface of said PZ layer, said top electrode layer, said PZ layer, and said bottom electrode layer collectively constituting a structure having a resonant frequency, said resonant frequency depending on a temperature of said PZ layer; and heating means for increasing said temperature of said PZ layer to a predetermined temperature whereat said resonant frequency is equal to a predetermined frequency, said heating means additionally indicating said temperature of said PZ layer. - View Dependent Claims (9)
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10. An acoustical resonator, comprising:
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a PZ layer having top and bottom surfaces; a bottom electrode layer adjacent to said bottom surface of said PZ layer; a top electrode layer adjacent to said top surface of said PZ layer; a layer of Si3 N4 adjacent to said bottom electrode layer, said bottom electrode being sandwiched between said layer of Si3 N4 and said PZ layer; and heating means for heating said PZ layer, said heating means comprising a metallic trace in contact with said Si3 N4 layer. - View Dependent Claims (11, 12, 13, 14, 15)
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16. An acoustical resonator, comprising:
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a thin-film PZ layer having top and bottom surfaces; a bottom electrode layer adjacent to said bottom surface of said PZ layer; a top electrode layer adjacent to said top surface of said PZ layer; and an evaporable tuning layer acoustically coupled to said PZ layer, part of said tuning layer being evaporated after fabrication of said acoustical resonator to provide a predetermined resonance frequency for said acoustical resonator, said tuning layer comprising a metallic layer and means for causing a current to pass through said metallic layer thereby causing a portion of said metallic layer to vaporize. - View Dependent Claims (17)
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18. An acoustical resonator, comprising:
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a PZ layer having top and bottom surfaces; a bottom electrode layer adjacent to said bottom surface of said PZ layer; a layer of Si3 N4 adjacent to said bottom electrode layer, said bottom electrode being sandwiched between said layer of Si3 N4 and said PZ layer; a top electrode layer adjacent to said top surface of said PZ layer; and a tuning layer in acoustical contact with said PZ layer, the thickness of said tuning layer being adjusted after fabrication of said acoustical resonator to provide a predetermined resonance frequency for said acoustical resonator. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25)
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Specification