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US 5,587,620 AGranted
Tunable thin film acoustic resonators and method for making the same
AssigneeHewlett-Packard Company
InventorsRichard C. Ruby, Paul P. Merchant
Life of this patent
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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 Si.sub.3 N.sub.4 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.
Claims25
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, 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.
4 more elements
An acoustical resonator, comprising:
- 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 Si.sub.3 N.sub.4 adjacent to said bottom electrode layer, said bottom electrode being sandwiched between said layer of Si.sub.3 N.sub.4 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.
3 more elements
An acoustical resonator, comprising:
- 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.
2 more elements
An acoustical resonator, comprising:
- 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 Si.sub.3 N.sub.4 adjacent to said bottom electrode layer, said bottom electrode being sandwiched between said layer of Si.sub.3 N.sub.4 and said PZ layer;
- and
- heating means for heating said PZ layer, said heating means comprising a metallic trace in contact with said Si.sub.3 N.sub.4 layer.
3 more elements
An acoustical resonator, comprising:
- 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.
2 more elements
An acoustical resonator, comprising:
- a PZ layer having top and bottom surfaces;
- a bottom electrode layer adjacent to said bottom surface of said PZ layer;
- a layer of Si.sub.3 N.sub.4 adjacent to said bottom electrode layer, said bottom electrode being sandwiched between said layer of Si.sub.3 N.sub.4 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.
3 more elements
Dependencies are inferred from the claim text.