Acoustically coupled resonators and method of making the same

Abstract

An apparatus includes a substrate with a cavity and a two-stage resonator filter fabricated over the cavity. The two-stage resonator filter includes a first stage and a second stage. The first stage includes a first resonator and a second resonator, the second resonator acoustically coupled to the first resonator. The second stage includes a third resonator and a fourth resonator, the fourth resonator acoustically coupled to the third resonator. The second resonator and the third resonators are electrically coupled. A decoupling layer couples the first resonator and the second resonator. The decoupling layer extends between the third resonator and the fourth resonator. The first resonator and the fourth resonator are above the substrate. The decoupling layer is above the first resonator and the fourth resonator. The second resonator and the third resonators are above the decoupling layer.

1 - 6 . (canceled) 
     
     
         7 . A method of manufacturing an apparatus, said method comprising: etching a cavity within a substrate, the cavity open to a first major surface of the substrate; filling said cavity with sacrificial material; fabricating a two-stage resonator filter above the cavity; and removing the sacrificial material from the cavity. 
     
     
         8 . The method recited in  claim 7  wherein the two-stage resonator filter comprises a lower piezoelectric layer; a coupling layer above lower piezoelectric layer; an upper piezoelectric layer; and wherein the lower piezoelectric layer and the upper piezoelectric layer enclose the coupling layer. 
     
     
         9 . The method recited in  claim 7  wherein the two-stage resonator filter comprises a coupling layer comprising coupling material; and the sacrificial material different than the coupling material. 
     
     
         10 . The method recited in  claim 7  wherein the coupling layer comprises Silicon dioxide (SiO2). 
     
     
         11 . The method recited in  claim 7  wherein the sacrificial layer comprises Silicon dioxide (SiO2). 
     
     
         12 . The method recited in  claim 7  wherein the two-stage resonator filter comprises: a first stage including a first resonator and a second resonator; the second resonator acoustically coupled to the first resonator; a second stage including a third resonator and a fourth resonator; the fourth resonator acoustically coupled to the third resonator; a decoupling layer between the first resonator and the second resonator, the decoupling layer extending between the third resonator and the fourth resonator; wherein the second resonator and the third resonators are electrically coupled; the first resonator and the fourth resonator are situated above the substrate; the decoupling layer is situated above the first resonator and the fourth resonator; and the second resonator and the third resonator are situated above the decoupling layer. 
     
     
         13 . The method recited in  claim 8  wherein the sacrificial material is removed after fabrication of a lower pair of resonators of the two-stage resonator filter above the cavity but before the rest of the two-stage resonator filter is fabricated. 
     
     
         14 . The method recited in  claim 13  further comprising a step of closing access to the cavity. 
     
     
         15 . The method recited in  claim 14  wherein dielectric material plugs opening of the cavity. 
     
     
         16 - 22 . (canceled)