Hybrid structure for a surface acoustic wave device

Abstract

A hybrid structure for a surface acoustic wave device comprises a useful layer of piezoelectric material having a free first surface and a second surface disposed on a support substrate that has a lower coefficient of thermal expansion than that of the useful layer. The hybrid structure further comprises a trapping layer disposed between the useful layer and the support substrate, and at least one functional interface of predetermined roughness between the useful layer and the trapping layer.

What is claimed is: 
     
         1 . An acoustic wave device, comprising:
 a carrier substrate having a first coefficient of thermal expansion;   a useful layer of piezoelectric material over the carrier substrate and having an exposed surface, the useful layer of piezoelectric material having a second coefficient of thermal expansion higher than the first coefficient of thermal expansion of the carrier substrate;   a charge trapping layer interposed between the useful layer and the carrier substrate and configured to trap moving electric loads in the carrier substrate during operation of an acoustic wave device; and   an electrode comb disposed on the upper first face of the useful layer.   
     
     
         2 . The acoustic wave device of  claim 1 , wherein the piezoelectric material comprises at least one material selected from the group consisting of: lithium tantalate (LiTaO 3 ), lithium niobate (LiNbO 3 ), quartz, zinc oxide (ZnO), and aluminum nitride (AlN). 
     
     
         3 . The acoustic wave device of  claim 2 , wherein the piezoelectric material comprises lithium tantalate (LiTaO 3 ). 
     
     
         4 . The acoustic wave device of  claim 1 , wherein the useful layer of piezoelectric material has a thickness between 3 μm and 300 μm. 
     
     
         5 . The acoustic wave device of  claim 1 , wherein the charge trapping layer has a thickness between 30 nanometers and 30 μm. 
     
     
         6 . The acoustic wave device of  claim 1 , wherein the charge trapping layer comprises at least one material selected from the group consisting of: amorphous silicon, polycrystalline silicon, amorphous germanium, and polycrystalline germanium. 
     
     
         7 . The acoustic wave device of  claim 6 , wherein the charge trapping layer comprises polycrystalline silicon. 
     
     
         8 . The acoustic wave device of  claim 1 , further comprising an insulator layer between the charge trapping layer and the useful layer of piezoelectric material. 
     
     
         9 . A substrate for an acoustic wave device, comprising:
 a useful layer of piezoelectric material;   a carrier substrate having a coefficient of thermal expansion lower than a coefficient of thermal expansion of the useful layer;   a charge trapping material disposed on the carrier substrate between the useful layer of piezoelectric material and the carrier substrate; and   an electrically insulating layer disposed between the useful layer and the charge trapping layer.   
     
     
         10 . The hybrid structure of  claim 9 , wherein the electrically insulating layer comprises at least one material selected from among silicon oxide, silicon nitride, and silicon oxynitride. 
     
     
         11 . The hybrid structure of  claim 10 , wherein the electrically insulating layer comprises silicon oxide. 
     
     
         12 . The hybrid structure of  claim 9 , wherein the piezoelectric material comprises at least one material selected from among lithium tantalate (LiTaO 3 ), lithium niobate (LiNbO 3 ), quartz, zinc oxide (ZnO), and aluminum nitride (AlN). 
     
     
         13 . The hybrid structure of  claim 12 , wherein the piezoelectric material comprises lithium tantalate (LiTaO 3 ). 
     
     
         14 . The hybrid structure of  claim 9 , wherein the piezoelectric material comprises a layer of the piezoelectric material having a thickness between 3 μm and 300 μm. 
     
     
         15 . The hybrid structure of  claim 9 , wherein the charge trapping layer comprises at least one material selected from among amorphous silicon, polycrystalline silicon, amorphous germanium, and polycrystalline germanium. 
     
     
         16 . The hybrid structure of  claim 15 , wherein the charge trapping layer comprises polycrystalline silicon. 
     
     
         17 . The hybrid structure of  claim 15 , wherein the charge trapping layer has a thickness between 30 nanometers and 30 μm. 
     
     
         18 . The hybrid structure of  claim 9 , wherein the carrier substrate comprises silicon or germanium. 
     
     
         19 . A method of manufacturing a hybrid structure for a surface acoustic wave device, comprising:
 forming a charge trapping layer on a carrier substrate;   bonding a useful layer of piezoelectric material over the charge trapping layer on the carrier substrate, the useful layer of piezoelectric material having a coefficient of thermal expansion higher than a coefficient of thermal expansion of the carrier substrate; and   forming electrode comb elements on or in the useful layer of piezoelectric material, the electrode comb elements configured to propagate an acoustic wave through the useful layer of piezoelectric material between the electrode comb elements; and   wherein the charge trapping layer substantially traps electrical carriers in the carrier substrate during operation of the surface acoustic wave device.   
     
     
         20 . The method of  claim 19 , wherein forming the charge trapping layer on the carrier substrate comprises implanting ions in the carrier substrate. 
     
     
         21 . The method of  claim 20 , wherein the ions comprise ions of one or more elements selected from among argon, silicon, and nitrogen. 
     
     
         22 . The method of  claim 19 , wherein bonding the useful layer of piezoelectric material over the charge trapping layer comprises direct bonding the useful layer of piezoelectric material over the charge trapping layer by molecular adhesion. 
     
     
         23 . The method of  claim 19 , wherein the carrier substrate comprises a silicon substrate, and wherein forming the charge trapping layer on the carrier substrate comprises forming a layer of polycrystalline silicon on the silicon substrate.