Composite structure and associated production method
A composite structure for an acoustic wave device comprising a heterostructure includes: a useful layer of piezoelectric material, having a first face and a second face, the first face being arranged at a first bonding interface on a support substrate having a coefficient of thermal expansion less than that of the useful layer, wherein the composite structure further comprises a functional layer, an entire surface of which is arranged at a second bonding interface on the second face of the useful layer and having a coefficient of thermal expansion less than that of the useful layer. Methods are used for producing such a composite structure.
1 . A composite structure for an acoustic wave device comprising a heterostructure, including:
a useful layer of piezoelectric material, having a first face and a second face, the first face being arranged at a first bonding interface between the useful layer and a support substrate, the support substrate having a lower coefficient of thermal expansion than that of the useful layer; and
a functional layer, the functional layer being substantially planar and having a substantially planar main face, the entirety of the substantially planar main face being arranged on the second face of the useful layer at a second bonding interface between the functional layer and the useful layer, the functional layer having a lower coefficient of thermal expansion than that of the useful layer,
wherein the functional layer exhibits a substantially uniform thickness along a longitudinal axis of the composite structure, and
wherein an adhesion energy of the first bonding interface between the useful layer and the support substrate of the heterostructure is greater than or equal to 1500 mJ/m 2 .
2 . The composite structure of claim 1 , wherein the functional layer has a thickness greater than or equal to 10 microns.
3 . The composite structure of claim 1 , wherein the useful layer comprises a material selected from the group consisting of lithium tantalate (LiTaO 3 ), lithium niobate (LiNbO 3 ), aluminum nitride (AIN), and zinc oxide (ZnO).
4 . The composite structure of claim 1 , wherein the functional layer comprises a material selected from the group consisting of silicon, III-V semiconductors, silicon carbide, glass, and sapphire.
5 . The composite structure of claim 1 , wherein the support substrate comprises a material selected from the group consisting of silicon, III-V semiconductors, silicon carbide, glass, and sapphire.
6 . The composite structure of claim 1 , wherein the functional layer and the support substrate consist essentially of the same material.
7 . The composite structure of claim 1 , wherein the functional layer comprises at least one first local opening enabling access to at least one first part of the second face of the useful layer, and wherein the first part of the second face of the useful layer comprises metal elements forming an acoustic wave device.
8 . The composite structure of claim 1 , wherein:
the functional layer comprises at least one first local opening enabling access to at least one first part of the second face of the useful layer;
the support substrate comprises at least one second local opening, at least partially facing the first local opening and enabling access to at least one second part of the first face of the useful layer; and
the first and second parts, respectively, of the second and first faces of the useful layer comprise metal elements forming an acoustic wave device.
9 . The composite structure of claim 7 , wherein the functional layer and/or the support substrate comprise(s) metal contacts and/or electronic devices electrically connected to metal elements arranged on the useful layer.
10 . A composite structure for an acoustic wave device comprising a heterostructure, including:
a useful layer of piezoelectric material, having a first face and a second face, the first face being arranged at a first bonding interface between the useful layer and a support substrate, the support substrate having a lower coefficient of thermal expansion than that of the useful layer; and
a functional layer, the functional layer being substantially planar and having a substantially planar main face, the entirety of the substantially planar main face being arranged on the second face of the useful layer at a second bonding interface between the functional layer and the useful layer, the functional layer having a lower coefficient of thermal expansion than that of the useful layer,
wherein the functional layer exhibits a substantially uniform thickness along a longitudinal axis of the composite structure, and
wherein the adhesion energy of the second bonding interface between the functional layer and the heterostructure is less than 1000 mJ/m 2 .
11 . The composite structure of claim 10 , wherein the functional layer has a thickness greater than or equal to 10 microns.
12 . The composite structure of claim 10 , wherein the useful layer comprises a material selected from the group consisting of lithium tantalate (LiTaO 3 ), lithium niobate (LiNbO 3 ), aluminum nitride (AIN), and zinc oxide (ZnO).
13 . The composite structure of claim 10 , wherein the functional layer comprises a material selected from the group consisting of silicon, III-V semiconductors, silicon carbide, glass, and sapphire.
14 . The composite structure of claim 10 , wherein the support substrate comprises a material selected from the group consisting of silicon, III-V semiconductors, silicon carbide, glass, and sapphire.
15 . The composite structure of claim 10 , wherein the functional layer and the support substrate consist essentially of the same material.
16 . The composite structure of claim 10 , wherein the functional layer comprises at least one first local opening enabling access to at least one first part of the second face of the useful layer, and wherein the first part of the second face of the useful layer comprises metal elements forming an acoustic wave device.
17 . The composite structure of claim 10 , wherein:
the functional layer comprises at least one first local opening enabling access to at least one first part of the second face of the useful layer;
the support substrate comprises at least one second local opening, at least partially facing the first local opening and enabling access to at least one second part of the first face of the useful layer; and
the first and second parts, respectively, of the second and first faces of the useful layer comprise metal elements forming an acoustic wave device.
18 . The composite structure of claim 16 , wherein the functional layer and/or the support substrate comprise(s) metal contacts and/or electronic devices electrically connected to metal elements arranged on the useful layer.