Mechanical resonating structures including a temperature compensation structure
Mechanical resonating structures are described, as well as related devices and methods. The mechanical resonating structures may have a compensating structure for compensating temperature variations.
1. A device comprising:
a mechanical resonating structure configured to support Lamb waves, the mechanical resonating structure including:
an active layer; and
a multi-layer compensating structure coupled to the active layer, the multi-layer compensating structure comprising:
first and second layers each having a stiffness that increases with increasing temperature over at least a first temperature range; and
a third layer between the first layer and the second layer, the third layer being formed of a material different than a material of which at least one of the first and second layers is formed.
2. The device of claim 1 , wherein the active layer comprises a piezoelectric material.
3. The device of claim 1 , wherein the multi-layer compensating structure is configured to provide the mechanical resonating structure with a temperature coefficient of frequency (TCF) having an absolute value of less than 10 ppm/K over a second temperature range from approximately −40° C. to approximately 85° C.
4. The device of claim 3 , wherein the TCF is approximately 0 ppm/K over a range of at least 5° C. within the second temperature range.
5. The device of claim 1 , wherein the multi-layer compensating structure is configured to provide the mechanical resonating structure with a TCF having an absolute value of less than 4 ppm/K over a second temperature range spanning at least 40° C. and centered approximately at 25° C.
6. The device of claim 5 , wherein the absolute value of the TCF is less than 0.5 ppm/K.
7. The device of claim 1 , wherein the active layer comprises aluminum nitride.
8. The device of claim 1 , wherein the first layer and the second layer of the multi-layer compensating structure are formed of a first material.
9. The device of claim 1 , wherein the first layer and the second layer of the multi-layer compensating structure have approximately the same thickness as each other.
10. The device of claim 1 , wherein the first layer is formed of silicon dioxide.
11. The device of claim 1 , wherein the third layer is formed of a material selected from the group consisting of silicon, silicon carbide, sapphire, quartz, germanium, gallium arsenide, aluminum nitride and diamond.
12. The device of claim 1 , wherein the first temperature range spans at least 100° C.
13. The device of claim 1 , wherein the first temperature range is between −40° C. and 85° C.
14. The device of claim 1 , wherein the active layer is formed of silicon.
15. The device of claim 1 , wherein the active layer is formed on the compensating structure.
16. A device comprising:
a resonating structure configured to support Lamb waves and including:
an active layer; and
a multi-layer compensating structure coupled to the active layer, the multi-layer compensating structure comprising
first and second layers each having a stiffness that increases with increasing temperature over at least a first temperature range, and
a third layer between the first and second layers,
wherein the first layer of the multi-layer compensating structure is formed of a first material and wherein the third layer is formed of a second material different than the first material, and
wherein the first material is silicon dioxide and the second material is silicon, and wherein a ratio of a total thickness of one or more layers of the resonating structure comprising the first material to a total thickness of one or more layers of the resonating structure comprising the second material is between 1:0.75 and 1:2.
17. The device of claim 16 , wherein the active layer comprises a piezoelectric material.
18. The device of claim 17 , wherein the multi-layer compensating structure is configured to provide the resonating structure with a temperature coefficient of frequency (TCF) having an absolute value of less than 10 ppm/K over a second temperature range from approximately −40° C. to approximately 85° C.
19. The device of claim 18 , wherein the active layer is formed of aluminum nitride.
20. A device comprising:
a multi-layer resonating structure including:
an active layer configured to support Lamb waves; and
a multi-layer compensating structure coupled to the active layer, the multi-layer compensating structure comprising:
first and second layers each having a stiffness that increases with increasing temperature over at least a first temperature range, and
a third layer formed of silicon, wherein the third layer is between the first and second layers, and wherein the first layer and/or the second layer is not formed of silicon.
21. The device of claim 20 , wherein the active layer comprises a piezoelectric material.
22. The device of claim 20 , wherein the first temperature range spans at least 100° C.