Acoustic resonator structure comprising a bridge

Abstract

An acoustic resonator comprises a first electrode a second electrode and a piezoelectric layer disposed between the first and second electrodes. The acoustic resonator further comprises a reflective element disposed beneath the first electrode, the second electrode and the piezoelectric layer. An overlap of the reflective element, the first electrode, the second electrode and the piezoelectric layer comprises an active area of the acoustic resonator. The acoustic resonator also comprises a bridge adjacent to a termination of the active area of the acoustic resonator.

1 . An acoustic wave resonator, comprising:
 (a) a substrate having a top surface;   (b) an acoustic mirror formed on the top surface of the substrate or in the substrate, having a first edge and an opposite, second edge;   (c) a first dielectric layer formed on the substrate such that the dielectric layer is substantially in contact with the first and second edges of the acoustic mirror;   (d) a first electrode formed over the substrate and overlying the acoustic mirror, having a first end portion and an opposite, second end portion, wherein at least one of the first and second end portions extends beyond one of the first and second edges of the acoustic mirror and is situated on the first dielectric layer;   (e) a second dielectric layer formed on the acoustic mirror and the first dielectric layer such that the second dielectric layer is substantially in contact with the first and second end portions of the first electrode;   (f) a piezoelectric layer formed on the first electrode and the second dielectric layer such that the piezoelectric layer overlapping the end portion of the first electrode is isolated from the first electrode; and   (g) a second electrode deposited on the piezoelectric layer having a portion situated above the acoustic mirror.   
     
     
         2 . An acoustic wave resonator comprising:
 (a) a substrate having a top surface;   (b) an acoustic mirror formed on the top surface of the substrate or in the substrate, having a first edge and an opposite, second edge;   (c) a dielectric layer formed on the substrate such that the dielectric layer is substantially in contact with the first and second edges of the acoustic mirror;   (d) a first electrode formed over the substrate and overlying the acoustic mirror, having a first end portion and an opposite, second end portion, wherein the first end portion extends beyond one of the first and second edges of the acoustic mirror and situates on the dielectric layer and the second end portion locates between the first and second edges of the acoustic mirror;   (e) a piezoelectric layer formed on the first electrode and extending beyond the second end portion of the first electrode and onto the dielectric layer so as to define an air gap therebetween; and   (f) a second electrode deposited on the piezoelectric layer having a portion situated above the acoustic mirror and extending crossover the second end portion of the first electrode.   
     
     
         3 . The acoustic wave resonator of  claim 12 , wherein the air gap is filled with a dielectric material having a dielectric constant. 
     
     
         4 . An acoustic wave resonator, comprising:
 (a) an acoustic mirror formed in or on a top surface of the substrate, having a first edge and an opposite, second edge; and   (b) a plurality of multilayered piezoelectric structures stacked over the acoustic mirror, wherein each two adjacent multilayered piezoelectric structures are separated by a decoupling layer, wherein each multilayered piezoelectric structure comprises a first electrode having a end portion, a second electrode and a piezoelectric layer formed therebetween, and wherein at least one of the first electrode and the second electrode and the piezoelectric layer define an air gap in a region that overlaps the end portion of the first electrode.   
     
     
         5 . The acoustic wave resonator of claim  19 , wherein the decoupling layer comprises a single layer or a multilayer. 
     
     
         6 . The acoustic wave resonator of  claim 5 , wherein the air gap is filled with a dielectric material. 
     
     
         7 . A method of fabricating an acoustic wave resonator, comprising the steps of:
 (a) forming an acoustic mirror having a first edge and an opposite, second edge, on a top surface of a substrate or in the substrate;   (b) forming a dielectric layer on the substrate such that the dielectric layer is substantially in contact with the first and second edges of the acoustic mirror;   (c) forming a first electrode having a end portion, over the acoustic mirror, the end portion extending beyond the acoustic mirror and onto the dielectric layer;   (d) forming a piezoelectric layer on the first electrode and the dielectric layer; and   (e) forming a second electrode on the piezoelectric layer such that the second electrode extends beyond the end portion of the first electrode to define a region in which the second electrode overlapping the end portion of the first electrode is isolated from the piezoelectric layer.   
     
     
         8 . The method of  claim 7 , wherein the step of forming the acoustic mirror comprises the step of forming an air cavity functioning as the acoustic mirror on the top surface of the substrate or in the substrate. 
     
     
         9 . The method of  claim 8 , wherein the step of forming the air cavity comprises the step of forming a sacrificial layer having a shape of the acoustic mirror on the top surface of the substrate. 
     
     
         10 . The method of  claim 9 , further comprising the step of removing the sacrificial layer from the substrate to form the acoustic mirror thereon. 
     
     
         11 . The method of  claim 7 , wherein the step of forming the second electrode comprises the steps of:
 (i) forming a sacrificial layer on the piezoelectric layer such that the sacrificial layer covers at least the region overlapping the end portion of the first electrode;   (ii) depositing the second electrode on the piezoelectric layer and over the sacrificial layer; and   (iii) removing the sacrificial layer to form an air gap between the second electrode and the piezoelectric layer in the region overlapping the end portion of the first electrode.   
     
     
         12 . The method of  claim 7 , wherein the step of forming the second electrode comprises the steps of:
 (i) forming a second dielectric layer on the piezoelectric layer such that the dielectric layer covers at least the region overlapping the end portion of the first electrode; and   (ii) depositing the second electrode on the piezoelectric layer and over the second dielectric layer.   
     
     
         13 . A method of fabricating an acoustic wave resonator, comprising the steps of:
 (a) forming an acoustic mirror having a first edge and an opposite, second edge, on a top surface of a substrate or in the substrate;   (b) forming a dielectric layer on the substrate such that the dielectric layer is substantially in contact with the first and second edges of the acoustic mirror;   (c) forming a first electrode having a first end portion and an opposite, second end portion, over the acoustic mirror, wherein the first end portion extends beyond the first edge of the acoustic mirror and onto the dielectric layer and wherein the second end portion extends beyond the second edge of the acoustic mirror or locates between the first and second edges of the acoustic mirror;   (d) forming a piezoelectric layer on the first electrode and extending beyond at least one of the first and second end portions of the first electrode and crossing over the first electrode layer so as to define a region in which the piezoelectric layer crosses over the first electrode layer is isolated from the first electrode layer; and   (e) forming a second electrode deposited on the piezoelectric layer having a portion situated above the acoustic mirror and extending over at least one of the first and second end portions of the first electrode and the defined region.   
     
     
         14 . The method of  claim 13 , wherein the step of forming the piezoelectric layer comprises the steps of: (i) depositing an dielectric film on the end portion of the first electrode and an area of the dielectric layer surrounding the end portion of the first electrode to form a planarized surface thereon; and (ii) growing the piezoelectric layer on the planarized surface. 
     
     
         15 . The method of  claim 13 , wherein an air gap is defined between the piezoelectric layer and the first electrode layer in the region.