Composite substrates including epitaxial monocrystalline piezoelectric layers bonded to substrates, and acoustic wave devices formed with such composite substrates

Abstract

A composite substrate includes a final substrate, and a piezoelectric material directly molecularly bonded to the final substrate at a first interface. The piezoelectric material comprises an epitaxial layer, but does not comprise a seed layer. Additional composite substrates include a final substrate, and a piezoelectric material directly molecularly bonded to the final substrate at a first interface. The piezoelectric material comprises an epitaxial layer. The composite substrate further includes a seed layer on which the piezoelectric material has been epitaxially grown. The seed layer is disposed on a side of the epitaxial layer opposite the final substrate. An acoustic wave device comprises such a composite substrate with at least one electrode on a surface of the piezoelectric layer opposite the substrate.

What is claimed is: 
     
         1 . A composite substrate, comprising:
 a final substrate;   a piezoelectric material directly molecularly bonded to the final substrate at a first interface, the piezoelectric material comprising an epitaxial layer; and   wherein the piezoelectric material does not comprise a seed layer.   
     
     
         2 . The composite substrate of  claim 1 , wherein the epitaxial layer has a thickness within a range from about 0.15 μm to about 20 μm. 
     
     
         3 . The composite substrate of  claim 1 , wherein the epitaxial layer is doped. 
     
     
         4 . The composite substrate of  claim 1 , wherein the piezoelectric material comprises quartz or a compound with the formula LiXO 3 , in which X is selected from among niobium and/or tantalum. 
     
     
         5 . A composite substrate, comprising:
 a final substrate;   a piezoelectric material directly molecularly bonded to the final substrate at a first interface, the piezoelectric material comprising an epitaxial layer; and   a seed layer on which the piezoelectric material has been epitaxially grown, the seed layer disposed on a side of the epitaxial layer opposite the final substrate.   
     
     
         6 . The composite substrate of  claim 5 , wherein the epitaxial layer has substantially the same mesh parameter as the seed layer. 
     
     
         7 . The composite substrate of  claim 5 , wherein the epitaxial layer has a different crystalline quality than the seed layer. 
     
     
         8 . The composite substrate of  claim 5 , wherein a thickness of the seed layer is less than 0.2 μm. 
     
     
         9 . The composite substrate of  claim 5 , wherein the epitaxial layer has a thickness within a range from about 0.15 μm to about 20 μm. 
     
     
         10 . The composite substrate of  claim 5 , wherein the epitaxial layer is doped. 
     
     
         11 . The composite substrate of  claim 5 , wherein the piezoelectric material comprises quartz or a compound with the formula LiXO 3 , in which X is selected from among niobium and/or tantalum. 
     
     
         12 . The composite substrate of  claim 5 , further comprising a receiving substrate directly molecularly bonded to the seed layer on a side thereof opposite the epitaxial layer. 
     
     
         13 . The composite substrate of  claim 5 , wherein the one or more insulators include one or more mirrors and/or cavities to prevent propagation of acoustic waves in the receiving substrate. 
     
     
         14 . An acoustic wave device, comprising:
 a substrate; and   an epitaxially grown monocrystalline piezoelectric layer directly molecularly bonded to the substrate; and   at least one electrode on a surface of the piezoelectric layer opposite the substrate.   
     
     
         15 . The acoustic wave device of  claim 14 , wherein the piezoelectric layer has a first portion located at the interface with the substrate, and a second portion extending from the first portion, and wherein a characteristic of the second portion is different from a characteristic of the first portion. 
     
     
         16 . The acoustic wave device of  claim 15 , wherein the characteristic is crystalline quality or composition. 
     
     
         17 . The acoustic wave device of  claim 16 , wherein the first portion comprises a seed layer, and the second portion comprises piezoelectric material epitaxially grown on the seed layer. 
     
     
         18 . The acoustic wave device of  claim 14 , wherein the substrate comprises a receiving substrate, and wherein the epitaxially grown monocrystalline piezoelectric layer directly molecularly bonded to the substrate comprises a seed layer disposed at the interface between the epitaxially grown monocrystalline piezoelectric layer and the receiving substrate. 
     
     
         19 . The acoustic wave device of  claim 14 , wherein the substrate comprises a final substrate, and wherein the epitaxially grown monocrystalline piezoelectric layer directly molecularly bonded to the substrate does not comprise a seed layer. 
     
     
         20 . The acoustic wave device of  claim 14 , wherein the acoustic wave device is a bulk acoustic wave device further comprising at least one electrode at or proximate the interface between the epitaxially grown monocrystalline piezoelectric layer and the substrate. 
     
     
         21 . The acoustic wave device of  claim 14 , wherein the acoustic wave device is a surface acoustic wave device further comprising at least one additional electrode on the surface of the piezoelectric layer opposite the substrate.