Temperature compensated bulk acoustic wave resonator with a high coupling coefficient
The dominant frequency of a solidly mounted resonator ( 100/280/300/400 ) is substantially increased by reducing the thickness of each layer of each Bragg acoustic reflector ( 112/160/224/274 ) to have a thickness than is substantially equal to one-quarter of the wavelength of a frequency that is a higher harmonic resonant frequency of the fundamental resonant frequency of the solidly mounted resonator ( 100/280/300/400 ).
1. A solidly mounted resonator (SMR) comprising:
a substrate;
a lower Bragg acoustic reflector that touches the substrate, the lower Bragg acoustic reflector having alternating layers of a low-acoustic material and a high-acoustic material, each layer of material within the lower Bragg acoustic reflector having a thickness substantially equal to one-quarter of a wavelength of a frequency that is a higher harmonic resonant frequency of a fundamental resonant frequency of the SMR;
a lower electrode that touches the lower Bragg acoustic reflector;
a piezoelectric structure that touches the lower electrode, wherein the piezoelectric structure has a thickness substantially equal to one-half of the wavelength of the fundamental resonant frequency of the SMR; and
an upper electrode that touches the piezoelectric structure.
2. The SMR of claim 1 and further comprising an upper Bragg acoustic reflector that touches the upper electrode, the upper Bragg acoustic reflector having alternating layers of a low-acoustic material and a high-acoustic material, each layer of material within the upper Bragg acoustic reflector having a thickness substantially equal to one-quarter of the wavelength of the frequency that is the higher harmonic resonant frequency of the fundamental resonant frequency of the SMR.
3. The SMR of claim 2 and further comprising:
a lower isolation layer that lies between and touches the lower Bragg acoustic reflector and the lower electrode; and
an upper isolation layer that lies between and touches the upper electrode and the upper Bragg acoustic reflector.
4. The SMR of claim 2 and further comprising an isolation layer that lies between and touches the piezoelectric structure and the upper electrode.
5. The SMR of claim 2 , wherein the piezoelectric structure includes a material selected from a list of materials that includes AlN, ZnO, and PZT.
6. The SMR of claim 5 wherein the low-acoustic material is selected from a list of materials that includes MSQ, SiO 2 , and HSQ.
7. The SMR of claim 6 wherein the high-acoustic material is selected from a list of materials that includes SiC, Si-DLC, and DLC.
8. A method of forming a solidly mounted resonator (SMR) comprising:
forming a lower Bragg acoustic reflector to touch a substrate, the lower Bragg acoustic reflector having alternating layers of a low-acoustic material and a high-acoustic material, each layer of material within the lower Bragg acoustic reflector having a thickness substantially equal to one-quarter of a wavelength of a frequency that is a higher harmonic resonant frequency of a fundamental resonant frequency of the SMR;
forming a lower electrode that touches the lower Bragg acoustic reflector;
forming a piezoelectric structure that touches the lower electrode; wherein the piezoelectric structure has a thickness substantially equal to one-half of the wavelength of the fundamental resonant frequency of the SMR; and
forming an upper electrode that touches the piezoelectric structure.
9. The method of claim 8 and further comprising forming an upper Bragg acoustic reflector that touches the upper electrode, the upper Bragg acoustic reflector having alternating layers of a low-acoustic material and a high-acoustic material, each layer of material within the upper Bragg acoustic reflector having a thickness substantially equal to one-quarter of the wavelength of the frequency that is the higher harmonic resonant frequency of the fundamental resonant frequency of the SMR.
10. The method of claim 9 and further comprising:
forming a lower isolation layer that lies between and touches the lower Bragg acoustic reflector and the lower electrode; and
forming an upper isolation layer that lies between and touches the upper electrode and the upper Bragg acoustic reflector.
11. The method of claim 9 and further comprising forming an isolation layer that lies between and touches the piezoelectric structure and the upper electrode.
12. The method of claim 8 , wherein the piezoelectric structure includes a material selected from a list of materials that includes AlN, ZnO, and PZT.
13. The method of claim 12 wherein the low-acoustic material is selected from a list of materials that includes MSQ, SiO 2 , and HSQ.
14. The method of claim 13 wherein the high-acoustic material is selected from a list of materials that includes SiC, Si-DLC, and DLC.
15. A solidly mounted resonator (SMR) comprising:
a substrate;
a lower Bragg acoustic reflector that touches the substrate, the lower Bragg acoustic reflector having alternating layers of a low-acoustic material and a high-acoustic material, each layer of material within the lower Bragg acoustic reflector having a thickness substantially equal to one-quarter of a wavelength of a frequency that is a higher harmonic resonant frequency of a fundamental resonant frequency of the SMR;
a lower isolation layer that touches the lower Bragg acoustic reflector;
a lower electrode that touches the lower isolation layer;
a piezoelectric structure that touches the lower electrode, wherein the piezoelectric structure has a thickness substantially equal to one-half of the wavelength of the fundamental resonant frequency of the SMR;
an upper electrode that touches the piezoelectric structure;
an upper isolation layer that touches the upper electrode; and
an upper Bragg acoustic reflector that touches the upper isolation layer, the upper Bragg acoustic reflector having alternating layers of a low-acoustic material and a high-acoustic material, each layer of material within the upper Bragg acoustic reflector having a thickness substantially equal to one-quarter of the wavelength of the frequency that is a higher harmonic resonant frequency of the fundamental resonant frequency of the SMR.
16. The SMR of claim 15 , wherein the piezoelectric structure includes a material selected from a list of materials that includes AlN, ZnO, and PZT.
17. The SMR of claim 16 wherein:
the low-acoustic material is selected from a list of materials that includes MSQ, SiO 2 , and HSQ; and
the high-acoustic material is selected from a list of materials that includes SiC, Si-DLC, and DLC.
18. The SMR of claim 1 , wherein the higher harmonic resonant frequency is a non-integer multiple of the fundamental resonant frequency.
19. The SMR of claim 8 , wherein the higher harmonic resonant frequency is a non-integer multiple of the fundamental resonant frequency.
20. The SMR of claim 15 , wherein the higher harmonic resonant frequency is a non-integer multiple of the fundamental resonant frequency.