Encapsulated packaging for thin-film resonators and thin-film resonator-based filters having a piezoelectric resonator between two acoustic reflectors
First Claim
1. A microelectronic device, comprising:
- a substrate, and the substrate comprises silicon;
a piezoelectric resonator disposed on the substrate, the piezoelectric resonator comprises a first electrode layer of metal deposited on the silicon, a layer of piezoelectric material deposited over the first electrode layer, and a second electrode layer of metal deposited over the piezoelectric material layer;
an acoustic reflector located over and coupled to the piezoelectric resonator;
an encapsulant comprising a molding compound having a low acoustic impedance, the encapsulant deposited over and encapsulating the piezoelectric resonator and acoustic reflector, the encapsulant making contact with the acoustic reflector;
the acoustic reflector transforms the low acoustic impedance of the encapsulant into a high acoustic impedance at the acoustic resonator/acoustic reflector interface; and
wherein the acoustic reflector comprises alternating acoustic reflecting layers of first and second acoustic impedance materials deposited over the second electrode layer of metal;
the first acoustic impedance being higher than the second acoustic impedance.
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Abstract
An acoustic reflector (48) is applied over a thin-film piezoelectric resonator (41, 61) which is supported on a semiconductor or semiconductor-compatible substrate (42, 62) of a microelectronic device (40, 60), enabling an encapsulant (49) to be applied over the reflector-covered resonator without acoustically damping the resonator. In one embodiment, alternating high and low acoustic impedance layers (51, 53 . . . 55) of one-quarter wavelength thicknesses constructively reflect the resonating wavelength to make an encapsulant in the form of an inexpensive plastic molding compound appear as a “clamping” surface to a resonator (41) peripherally supported over an opening (43) on a silicon substrate (42). In another embodiment, an encapsulant- and reflector-covered resonator (61) is mechanically supported above a second reflector (68) which eliminates the need for peripheral support, making substrate (68) also appear as a clamping surface. The invention enables low cost plastic packaging of resonators and associated circuitry on a single monolithic structure. A radio frequency transceiver front-end application is given as an exemplary implementation.
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Citations
6 Claims
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1. A microelectronic device, comprising:
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a substrate, and the substrate comprises silicon;
a piezoelectric resonator disposed on the substrate, the piezoelectric resonator comprises a first electrode layer of metal deposited on the silicon, a layer of piezoelectric material deposited over the first electrode layer, and a second electrode layer of metal deposited over the piezoelectric material layer;
an acoustic reflector located over and coupled to the piezoelectric resonator;
an encapsulant comprising a molding compound having a low acoustic impedance, the encapsulant deposited over and encapsulating the piezoelectric resonator and acoustic reflector, the encapsulant making contact with the acoustic reflector;
the acoustic reflector transforms the low acoustic impedance of the encapsulant into a high acoustic impedance at the acoustic resonator/acoustic reflector interface; and
wherein the acoustic reflector comprises alternating acoustic reflecting layers of first and second acoustic impedance materials deposited over the second electrode layer of metal;
the first acoustic impedance being higher than the second acoustic impedance.- View Dependent Claims (2, 3, 4, 5, 6)
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Specification