Surface acoustic wave device with multi-layer piezoelectric substrate

Abstract

A surface acoustic wave device is disclosed. the surface acoustic wave device can include a single crystal support layer, an intermediate single crystal layer positioned over the single crystal support layer, a lithium based piezoelectric layer positioned over the intermediate single crystal layer, and an interdigital transducer electrode positioned over the lithium based piezoelectric layer, the surface acoustic wave device configured to generate a surface acoustic wave. The single crystal layer can be a quartz layer, such as a z-propagation quartz layer. A thermal conductivity of the single crystal support layer is greater than a thermal conductivity of the intermediate single crystal layer, and the thermal conductivity of the single crystal support layer is greater than a thermal conductivity of the lithium based piezoelectric layer.

What is claimed is: 
     
         1 . A surface acoustic wave device comprising:
 a single crystal support layer;   an intermediate single crystal layer over the single crystal support layer;   a lithium based piezoelectric layer over the intermediate single crystal layer; and   an interdigital transducer electrode over the lithium based piezoelectric layer, the surface acoustic wave device configured to generate a surface acoustic wave.   
     
     
         2 . The surface acoustic wave device of  claim 1  wherein the single crystal support layer is a silicon layer or an aluminum nitride layer. 
     
     
         3 . The surface acoustic wave device of  claim 1  wherein the single crystal support layer has a thickness that is greater than a combined thickness of the intermediate single crystal layer and the lithium based piezoelectric layer. 
     
     
         4 . The surface acoustic wave device of  claim 1  wherein the intermediate single crystal layer is a quartz layer, and the quartz layer has a first Euler angle φ in a range from 40° to 5°, a second Euler angle θ in a range from 85° to 95°, and a third Euler angle ψ in a range from 85° to 95°. 
     
     
         5 . The surface acoustic wave device of  claim 1  wherein the intermediate single crystal layer is a quartz layer, and the quartz layer has a first Euler angle φ in a range from −5° to 5°, a second Euler angle θ in a range from 120° to 170°, and a third Euler angle ψ in a range from −5° to 5° or 85° to 95°. 
     
     
         6 . The surface acoustic wave device of  claim 1  wherein the intermediate single crystal layer has a thickness in a range from 5 λ to 20 λ. 
     
     
         7 . The surface acoustic wave device of  claim 1  wherein the lithium based piezoelectric layer is a lithium tantalate layer or a lithium niobate layer, the lithium tantalate layer has a first Euler angle φ in a range from −5° to 5°, a second Euler angle θ in a range from 100° to 150°, and a third Euler angle ψ in a range from −5° to 5°, and the lithium niobate layer has a first Euler angle φ in a range from −5° to 5°, a second Euler angle θ in a range from 100° to 150°, and a third Euler angle ψ in a range from −5° to 5°. 
     
     
         8 . The surface acoustic wave device of  claim 1  wherein the lithium based piezoelectric layer has a thickness in a range from 0.1 λ to 2 λ. 
     
     
         9 . The surface acoustic wave device of  claim 1  wherein a thermal conductivity of the single crystal support layer is greater than a thermal conductivity of the intermediate single crystal layer, and the thermal conductivity of the single crystal support layer is greater than a thermal conductivity of the lithium based piezoelectric layer. 
     
     
         10 . A surface acoustic wave device comprising:
 a support layer;   a quartz layer over the support layer, the quartz layer having a lower thermal conductivity than the support layer;   a lithium based piezoelectric layer over the quartz layer, the lithium based piezoelectric layer having a lower thermal conductivity than the support layer; and   an interdigital transducer electrode over the lithium based piezoelectric layer, the surface acoustic wave device configured to generate a surface acoustic wave.   
     
     
         11 . The surface acoustic wave device of  claim 10  wherein the support layer is a silicon layer or an aluminum nitride layer. 
     
     
         12 . The surface acoustic wave device of  claim 10  wherein the support layer has a thickness greater than a combined thickness of the quartz layer and the lithium based piezoelectric layer. 
     
     
         13 . The surface acoustic wave device of  claim 10  wherein the quartz layer is a z-propagation quartz layer having a second Euler angle θ in a range from 120° to 140°. 
     
     
         14 . The surface acoustic wave device of  claim 10  wherein the quartz layer has a thickness in a range from 5 λ to 20 λ, λ is a wavelength of the surface acoustic wave, and the lithium based piezoelectric layer has a thickness in a range from 0.1 λ to 2 λ. 
     
     
         15 . The surface acoustic wave device of  claim 10  further comprising a silicon dioxide layer between the quartz layer and the lithium based piezoelectric layer. 
     
     
         16 . The surface acoustic wave device of  claim 10  further comprising a first silicon dioxide layer between the support layer and the quartz layer, and a second silicon dioxide layer between the quartz layer and the lithium based piezoelectric layer. 
     
     
         17 . An acoustic wave filter for filtering a radio frequency signal, the acoustic wave filter comprising the surface acoustic wave device of  claim 10 . 
     
     
         18 . A surface acoustic wave device comprising:
 a support layer;   a z-propagation quartz layer over the support layer, the support layer having a thermal conductivity higher than a thermal conductivity of the z-propagation quartz layer;   a lithium based piezoelectric layer over the z-propagation quartz layer, the thermal conductivity of the support layer being higher than a thermal conductivity of the lithium based piezoelectric layer; and   an interdigital transducer electrode over the lithium based piezoelectric layer, the surface acoustic wave device configured to generate a surface acoustic wave.   
     
     
         19 . The surface acoustic wave device of  claim 18  wherein the support layer is a spinel support layer or a silicon support layer. 
     
     
         20 . The surface acoustic wave device of  claim 18  wherein the thermal conductivity of the support layer is at least double the thermal conductivity of the z-propagation quartz layer.