Layer acoustic wave device and method of making the same
View Patent ↗The present invention provides a layer acoustic wave device that is formed without requiring a bonding process to attach a secondary substrate. In particular, the layer acoustic wave device is formed from a substrate, an interdigital transducer created on the substrate, a dielectric layer formed over the interdigital transducer and substrate, and at least one isolation layer formed over the dielectric layer. The at least one isolation layer has sufficient properties to minimize particle displacement on a top surface of the at least one isolation layer. The at least one isolation layer has a greater acoustic impedance than that of the dielectric layer.
1. A layer acoustic wave device comprising:
a piezoelectric substrate having an upper surface;
a metallic interdigital transducer formed on the upper surface of the piezoelectric substrate;
a dielectric layer having a first acoustic impedance and formed over the upper surface of the piezoelectric substrate and the metallic interdigital transducer;
a deposited or grown first isolation layer having a second acoustic impedance and over the dielectric layer, the second acoustic impedance being greater than the first acoustic impedance, wherein the deposited or grown first isolation layer is configured to confine acoustic energy in the dielectric layer;
a deposited or grown second isolation layer having a third acoustic impedance and over the deposited or grown first isolation layer; and
a deposited or grown third isolation layer having a fourth acoustic impedance and over the deposited or grown second isolation layer, wherein the fourth acoustic impedance is greater than the third acoustic impedance.
2. The layer acoustic wave device of claim 1 wherein an acoustic wave velocity of the deposited or grown first isolation layer is greater than an acoustic wave velocity of the dielectric layer.
3. The layer acoustic wave device of claim 1 wherein an acoustic wave velocity of the deposited or grown first isolation layer is less than an acoustic wave velocity of the dielectric layer.
4. The layer acoustic wave device of claim 1 wherein the third acoustic impedance is greater than the first acoustic impedance.
5. The layer acoustic wave device of claim 4 wherein an acoustic wave velocity of the deposited or grown first isolation layer is greater than an acoustic wave velocity of the dielectric layer, and an acoustic wave velocity of the deposited or grown second isolation layer is less than the acoustic wave velocity of the dielectric layer.
6. The layer acoustic wave device of claim 4 wherein an acoustic wave velocity of the deposited or grown first isolation layer is less than an acoustic wave velocity of the dielectric layer, and an acoustic wave velocity of the deposited or grown second isolation layer is greater than the acoustic wave velocity of the dielectric layer.
7. The layer acoustic wave device of claim 1 further comprising a plurality of deposited or grown isolation layers disposed above the deposited or grown third isolation layer over the dielectric layer, wherein the plurality of deposited or grown isolation layers alternate between having an acoustic impedance greater than the first acoustic impedance and having an acoustic impedance less than the first acoustic impedance.
8. The layer acoustic wave device of claim 1 wherein there are no substrates bonded to the upper surface of the piezoelectric substrate.
9. The layer acoustic wave device of claim 1 wherein all layers formed over the dielectric layer are deposited or grown isolation layers.
10. The layer acoustic wave device of claim 1 wherein the second acoustic impedance is at least 1.5 times the first acoustic impedance.
11. The layer acoustic wave device of claim 1 wherein the second acoustic impedance is sufficiently greater than the first acoustic impedance to render particle displacement on an upper surface of the layer acoustic wave device negligible when layer acoustic waves are present in the dielectric layer.
12. The layer acoustic wave device of claim 11 wherein the particle displacement on the upper surface of the layer acoustic wave device is less than ten (10) percent of particle displacement on a surface of the piezoelectric substrate.
13. The layer acoustic wave device of claim 1 wherein the third acoustic impedance is lower than second acoustic impedance and the fourth acoustic impedance.
14. The layer acoustic wave device of claim 1 wherein the third acoustic impedance is equal to the first acoustic impedance.
15. The layer acoustic wave device of claim 1 wherein the third acoustic impedance is less than the first acoustic impedance.
16. The layer acoustic wave device of claim 1 wherein the deposited or grown first isolation layer is in direct contact with the dielectric layer, the deposited or grown second isolation layer is in direct contact with the deposited or grown first isolation layer, and the deposited or grown third isolation layer is in direct contact with the deposited or grown second isolation layer.
17. The layer acoustic wave device of claim 1 wherein the deposited or grown first isolation layer is in direct contact with the dielectric layer.
18. The layer acoustic wave device of claim 1 wherein the deposited or grown second isolation layer is in direct contact with the deposited or grown first isolation layer.
19. The layer acoustic wave device of claim 1 wherein the deposited or grown third isolation layer is in direct contact with the deposited or grown second isolation layer.