SAW resonator with improved power durability and heat resistance and RF filter comprising an SAW resonator
An improved SAW (SAWR) resonator having an improved power durability and heat resistance and a protection to prevent device failure is provided. The SAW resonator has a carrier substrate (S) and an electrode structure (ES, EF) on a piezoelectric material (PM, PL). Further, the resonator has a shunt path (PCPP) parallel to the electrode structure and provided to enable an RF signal to bypass the electrode structure. The shunt path has a temperature dependent conductance with negative temperature coefficient of resistance.
1. A surface acoustic wave (SAW) resonator, comprising:
a carrier substrate, an electrode structure, and a piezoelectric material arranged between the carrier substrate and the electrode structure; and
a shunt path arranged and configured to have a temperature dependent conductance that enables a radio frequency (RF) signal at an input of the electrode structure to bypass the electrode structure depending on a temperature of the shunt path.
2. The SAW resonator of claim 1 , further comprising reflection structures between which the electrode structure is arranged.
3. The SAW resonator of claim 1 , wherein the piezoelectric material is contained in a piezoelectric layer and the SAW resonator is a thin film SAW (TF-SAW) resonator.
4. The SAW resonator of claim 1 , further comprising a protection element, wherein the protection element establishes an element of the shunt path.
5. The SAW resonator of claim 1 , wherein the carrier substrate comprises silicon.
6. The SAW resonator of claim 1 , wherein the temperature dependence conductance of the shunt path is based on a doping.
7. The SAW resonator of claim 1 , further comprising a compensation layer between the carrier substrate and the piezoelectric material.
8. The SAW resonator of claim 7 , wherein the compensation layer comprises a silicon oxide, a doped silicon oxide, silicon dioxide, or doped silicon dioxide.
9. The SAW resonator of claim 1 , further comprising:
a shunt layer between the carrier substrate and the piezoelectric material, wherein the piezoelectric material is in a piezoelectric layer; and
a compensation layer between the shunt layer and the piezoelectric layer, wherein:
the carrier substrate comprises silicon,
the shunt layer comprises polycrystalline silicon and has a thickness between 0.01λ, and 1.0λ,
the compensation layer comprises a silicon oxide and has a thickness between 0.01λ, and 1.0λ,
the piezoelectric layer comprises lithium tantalate and has a thickness between 0.01λ, and 1.0λ,
the electrode structure comprises Al as its main constituent and has a thickness between 0.02λ, and 0.2λ, and
λ, is the acoustic wavelength of the SAW resonator's main mode.
10. The SAW resonator of claim 9 , wherein the carrier substrate is oriented such that Euler angles are (0°±10°, 0°±10°, 45°±10°) or (45°±10°, 54°±10°, 0°±) 10° with respect to the acoustic propagation direction of the SAW resonator's main mode.
11. An RF filter comprising the SAW resonator of claim 1 .
12. The SAW resonator of claim 1 , further comprising a shunt layer between the carrier substrate and the piezoelectric material, the shunt layer forming at least a portion of the shunt path.
13. The SAW resonator of claim 12 , wherein the shunt layer comprises polycrystalline silicon.
14. The SAW resonator of claim 12 , wherein the piezoelectric material is in a piezoelectric layer, and wherein the SAW resonator further comprises a compensation layer between the shunt layer and the piezoelectric layer.
15. A surface acoustic wave (SAW) resonator, comprising:
a carrier substrate, an electrode structure, and a piezoelectric material arranged between the carrier substrate and the electrode structure;
a shunt path parallel to the electrode structure and provided to enable a radio frequency (RF) signal to bypass the electrode structure, wherein the shunt path has a temperature dependent conductance; and
a shunt layer between the carrier substrate and the piezoelectric material.
16. The SAW resonator of claim 15 , wherein the shunt layer comprises polycrystalline silicon.
17. The SAW resonator of claim 16 , wherein the shunt layer has:
a conductivity below 10 −3 1/Ωcm at temperatures below 100° C.; and
a conductivity above 10 −3 1/Ωcm at temperatures above 200° C.
18. The SAW resonator of claim 15 , wherein the piezoelectric material is in a piezoelectric layer and wherein the SAW resonator further comprises a compensation layer between the shunt layer and the piezoelectric layer.
19. The SAW resonator of claim 15 , wherein the shunt layer forms at least a portion of the shunt path.
20. The SAW resonator of claim 15 , wherein the temperature dependent conductance of the shunt path is based at least in part on a doping in the shunt layer.