Acoustic resonator comprising collar and acoustic reflector with temperature compensating layer
First Claim
1. An acoustic resonator, comprising:
- an acoustic reflector disposed on a substrate over a cavity formed in the substrate, the acoustic reflector comprising a layer of low acoustic impedance material stacked on a layer of high acoustic impedance material;
a bottom electrode disposed on the layer of low acoustic impedance material of the acoustic reflector;
a piezoelectric layer disposed on the bottom electrode;
a top electrode disposed on the piezoelectric layer; and
a collar formed outside a main membrane region defined by an overlap between the top electrode, the piezoelectric layer and the bottom electrode, the collar having an inner edge substantially aligned with a boundary of or overlapping the main membrane region,wherein the layer of the low acoustic impedance material comprises a temperature compensating material having a positive temperature coefficient for offsetting at least a portion of a negative temperature coefficient of the piezoelectric layer, the bottom electrode and the top electrode.
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Abstract
An acoustic resonator structure includes an acoustic reflector over a cavity formed in a substrate, the acoustic reflector including a layer of low acoustic impedance material stacked on a layer of high acoustic impedance material. The acoustic resonator further includes a bottom electrode on the layer of low acoustic impedance material, a piezoelectric layer on the bottom electrode, a top electrode on the piezoelectric layer, and a collar formed outside a main membrane region defined by an overlap between the top electrode, the piezoelectric layer and the bottom electrode. The collar has an inner edge substantially aligned with a boundary of or overlapping the main membrane region. The layer of the low acoustic impedance material includes a temperature compensating material having a positive temperature coefficient for offsetting at least a portion of a negative temperature coefficient of the piezoelectric layer, the bottom electrode and the top electrode.
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Citations
20 Claims
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1. An acoustic resonator, comprising:
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an acoustic reflector disposed on a substrate over a cavity formed in the substrate, the acoustic reflector comprising a layer of low acoustic impedance material stacked on a layer of high acoustic impedance material; a bottom electrode disposed on the layer of low acoustic impedance material of the acoustic reflector; a piezoelectric layer disposed on the bottom electrode; a top electrode disposed on the piezoelectric layer; and a collar formed outside a main membrane region defined by an overlap between the top electrode, the piezoelectric layer and the bottom electrode, the collar having an inner edge substantially aligned with a boundary of or overlapping the main membrane region, wherein the layer of the low acoustic impedance material comprises a temperature compensating material having a positive temperature coefficient for offsetting at least a portion of a negative temperature coefficient of the piezoelectric layer, the bottom electrode and the top electrode. - View Dependent Claims (2, 3, 4, 6, 7, 8, 9, 10, 11, 12, 13, 14, 19)
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5. An acoustic resonator, comprising:
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an acoustic reflector disposed over a cavity formed in a substrate, the acoustic reflector comprising a layer of low acoustic impedance material stacked on a layer of high acoustic impedance material; a bottom electrode disposed on the layer of low acoustic impedance material of the acoustic reflector; a piezoelectric layer disposed on the bottom electrode; a top electrode disposed on the piezoelectric layer; and a collar formed outside a main membrane region defined by an overlap between the top electrode, the piezoelectric layer and the bottom electrode, the collar having an inner edge substantially aligned with a boundary of or overlapping the main membrane region, wherein the layer of the low acoustic impedance material comprises a temperature compensating material having a positive temperature coefficient for offsetting at least a portion of a negative temperature coefficient of the piezoelectric layer, the bottom electrode and the top electrode, and wherein the collar is formed between the bottom electrode and the piezoelectric layer. - View Dependent Claims (20)
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15. A thin-film bulk acoustic resonator (FBAR), comprising:
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a substrate defining a cavity; a distributed Bragg reflector (DBR) disposed on a top surface of the substrate over the cavity, the DBR comprising at least one layer of low acoustic impedance material having a positive temperature coefficient; an acoustic stack arranged on the DBR over the cavity, the acoustic stack comprising a piezoelectric layer sandwiched between bottom and top electrode layers, and having a main membrane region defined by an overlap between the bottom electrode, the piezoelectric layer, and the top electrode; and a collar arranged outside the main membrane region, the collar defining a collar region having a cutoff frequency that is substantially the same as a cutoff frequency of the main membrane region, wherein the positive temperature coefficient of the at least one layer of low acoustic impedance material offsets at least a portion of a negative temperature coefficient of the piezoelectric layer, the bottom electrode layer and the top electrode layer. - View Dependent Claims (16, 17, 18)
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Specification