Multiple layer acoustical structures for thin-film resonator based circuits and systems
First Claim
1. A thin film resonator device, comprising:
- a thin film resonator;
a substrate underlying and mechanically supporting the resonator, andan acoustical isolator disposed between and joining the resonator and the substrate and comprising layers of non-lossless material having characteristic impedances and thicknesses selected to present a nominal impedance to the thin film resonator such as would be found if the thin film resonator were coupled to air.
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Abstract
A stacked thin film device structure grown on a substrate, the resonator structure comprising a thin film device comprising at least one piezoelectric crystal layer sandwiched between metallic electrodes, and constructed to have an acoustic response in a given frequency range, and an acoustical stack disposed between and joining the thin film device and the substrate and comprising multiple layers of material, each layer having a characteristic thickness and impedance and being composed of a non-lossless material, the characteristic thicknesses and impedances of the layers being adjusted to determine the input impedance presented to the thin film device, and thereby determining the acoustical coupling between the thin film device and the substrate.
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Citations
14 Claims
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1. A thin film resonator device, comprising:
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a thin film resonator; a substrate underlying and mechanically supporting the resonator, and an acoustical isolator disposed between and joining the resonator and the substrate and comprising layers of non-lossless material having characteristic impedances and thicknesses selected to present a nominal impedance to the thin film resonator such as would be found if the thin film resonator were coupled to air.
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2. A stacked thin film device structure grown on a substrate, comprising;
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a thin film device comprising at least one piezoelectric crystal layer sandwiched between electrodes, and constructed to have an acoustic response and a given frequency range; an acoustical stack disposed between and joining the thin film device and the substrate and comprising multiple layers of material, each layer having a characteristic thickness and impedance and being composed of a non-lossless material, the characteristic thickness and impedances of the layers being adjusted to determine the input impedance presented to the thin film device, and thereby determining the acoustical coupling between the thin film device and the substrate; and wherein the acoustical stack is an acoustical isolator presenting a nominal input impedance to the thin film device mimicking an acoustical short circuit such as would be found if said thin film resonator were coupled to air, the isolator comprising a sufficient number of layers having characteristic thicknesses and impedances adjusted to cause the isolator to present an iterative impedance to the thin film device which meets an isolation condition in the given frequency range, thereby isolating the thin film device from the substrate. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A thin film resonator device, comprising:
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a thin film resonator; a substrate underlying and mechanically supporting the resonator, and an acoustical isolator disposed between and joining the resonator and the substrate and comprising at least six layers of non-lossless material having characteristic impedances and thicknesses adjusted to present a nominal input impedance to the resonator which acoustically isolates the resonator and substrate.
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14. A method for fabricating a thin film resonator device, comprising:
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a) providing a substrate; 1) for receiving an acoustical stack to be formed by sequentially depositing individual layers of non-lossless material on the substrate, each layer having a characteristic impedance and thickness; and 2) for receiving a thin film device to be formed by sequentially depositing a first electrode, a piezoelectric layer, and a second electrode, the properties of the electrodes and piezoelectric layer being chosen to give the thin film device an acoustic response in a given frequency range; b) determining the required characteristic thicknesses and impedances of each stack layer by determining the stack input impedance required to achieve acoustical isolation between the substrate and the thin film device in the given frequency range, the stack input impedance being nominal such as would be found if the thin film resonator device were coupled to air, and calculating the characteristic thicknesses and impedances to achieve that nominal input impedance; c) depositing the layers of the acoustical stack according to the determination of step b); and d) depositing the layers of the thin film device on the acoustical stack.
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Specification