Optimal acoustic impedance materials for polished substrate coating to suppress passband ripple in BAW resonators and filters
First Claim
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1. A method of reducing phase and amplitude ripples in a BAW resonator frequency response comprising:
- providing a substrate;
fabricating a Bragg mirror having alternate layers of a high acoustic impedance material and a low acoustic impedance material on a first side of the substrate;
fabricating a BAW resonator on the Bragg mirror;
coating a second side of the substrate opposite the first side with a lossy material having an acoustic impedance in the range of 0.01×
to 1.0×
the acoustic impedance of the layers of high acoustic impedance material;
the substrate of the BAW resonator having a thickness of 400 μ
m or less;
the second side of the substrate being a polished surface with a peak-to-peak roughness of approximately 1000 A.
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Abstract
Methods of reducing phase and amplitude ripples in a BAW resonator frequency response by providing a substrate, fabricating a Bragg mirror having alternate layers of a high acoustic material and a low acoustic material on a first surface of the substrate, fabricating a BAW on the Bragg mirror, and coating a second side of the substrate opposite the first side with a lossy material having an acoustic impedance in the range of 0.01× to 1.0× the acoustic impedance of the layers of high impedance material, the second surface of the substrate being a polished surface. Various embodiments are disclosed.
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Citations
9 Claims
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1. A method of reducing phase and amplitude ripples in a BAW resonator frequency response comprising:
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providing a substrate; fabricating a Bragg mirror having alternate layers of a high acoustic impedance material and a low acoustic impedance material on a first side of the substrate; fabricating a BAW resonator on the Bragg mirror; coating a second side of the substrate opposite the first side with a lossy material having an acoustic impedance in the range of 0.01×
to 1.0×
the acoustic impedance of the layers of high acoustic impedance material;the substrate of the BAW resonator having a thickness of 400 μ
m or less;the second side of the substrate being a polished surface with a peak-to-peak roughness of approximately 1000 A. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of reducing phase and amplitude ripples in a BAW resonator frequency response comprising:
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providing a substrate; fabricating a Bragg mirror having alternate layers of tungsten and a low acoustic impedance material on a first side of the substrate; fabricating a BAW on the Bragg mirror; coating a second side of the substrate opposite the first side with a lossy epoxy material having an acoustic impedance in the range of 0.01×
to 1.0×
the acoustic impedance of the layers of tungsten;the substrate of the BAW resonator having a thickness of 400 μ
m or less;the second side of the substrate being polished to a peak-to-peak roughness of less than approximately 1000 A. - View Dependent Claims (8, 9)
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Specification