Temperature controlled acoustic resonator comprising heater and sense resistors
A bulk acoustic wave (BAW) resonator device comprises a heating coil disposed over a first side of the piezoelectric layer and substantially around a perimeter adjacent to the active area of the acoustic resonator, the heating coil comprising a resistor configured to receive a heater current; and a heat sensor disposed over a second side of the piezoelectric layer and opposing the first side, the heat sensor configured to adjust the heater current in response to a temperature of the heating coil.
1. A bulk acoustic wave (BAW) resonator, comprising:
a substrate comprising a cavity having a plurality of sides;
a first electrode disposed over the cavity, the first electrode extending over at least one but not all of the sides of the cavity;
a piezoelectric layer disposed over at least a portion of the first electrode, and extending over the at least one of the plurality of sides having the first electrode extending thereover;
a second electrode disposed over the piezoelectric layer, and extending over the at least one of the plurality of sides, a contacting overlap of the first electrode, the piezoelectric layer and the second electrode forming an active area of the BAW resonator, wherein the second electrode does not overlap the first electrode over the at least one of the plurality of sides;
a heating coil disposed over a first side of the piezoelectric layer and substantially around a perimeter adjacent to the active area of the BAW resonator, the heating coil comprising a resistor configured to receive a heater current; and
a heat sensor disposed over a second side of the piezoelectric layer and opposing the first side, the heat sensor configured to adjust the heater current in response to a temperature of the heating coil.
2. The BAW resonator of claim 1 , further comprising a first conductive trace configured to provide the heater current to the heating coil.
3. The BAW resonator of claim 2 , wherein the first conductive trace extends over the at least one of the plurality of sides.
4. The BAW resonator of claim 3 , wherein the first conductive trace for providing the heater current to the heating coil comprises a metal trace having a thickness of about 300 Å to about 10000 Å, and wherein the heating coil comprises a heater resistor having a resistance between about 100Ω and about 5000Ω.
5. The BAW resonator of claim 4 , wherein the metal trace of the heating coil comprises at least one of molybdenum, tungsten and ruthenium.
6. The BAW resonator of claim 1 , wherein the piezoelectric layer comprises scandium doped aluminium nitride (ScAlN).
7. The BAW resonator of claim 6 , wherein an atomic percentage of scandium in the piezoelectric layer is approximately 0.5% to less than approximately 10.0%.
8. The BAW resonator of claim 6 , wherein an atomic percentage of scandium in the piezoelectric layer is approximately 2.5% to less than approximately 5.0%.
9. The BAW resonator of claim 1 , further comprising a second conductive trace configured to provide heat sensor current to the heat sensor, a change in the temperature of the heating coil causing a corresponding change in sensor resistance of the heat sensor.
10. The BAW resonator of claim 9 , wherein the second conductive trace extends over the at least one of the plurality of sides.
11. The BAW resonator of claim 1 , further comprising at least one tether connected between the piezoelectric layer and one of the sides of the cavity, the at least one tether being configured to limit transfer of externally applied forces to the BAW resonator.
12. The BAW resonator of claim 1 , wherein the at least one of the plurality of sides is one side of the cavity.
13. The BAW resonator of claim 1 , wherein the piezoelectric layer comprises rare-earth element doped piezoelectric material.
14. A BAW resonator structure, comprising:
a substrate comprising a cavity, the cavity comprising a plurality of sides;
a pillar formed within the cavity, the pillar comprising: a material having a coefficient of thermal conductivity that is equal to or less than a thermal conductivity of silicon (Si); and an electrical conductor disposed over an outer portion thereof;
a BAW resonator supported at a central location by the pillar and suspended over the cavity, the BAW resonator comprising: a first electrode disposed over the cavity; a piezoelectric layer disposed over at least a portion of the first electrode; and a second electrode disposed over the piezoelectric layer, a contacting overlap of the first electrode, the piezoelectric layer and the second electrode forming an active area of the BAW resonator;
a heating coil disposed over a first side of the piezoelectric layer and substantially around a perimeter adjacent to the active area of the BAW resonator, the heating coil comprising a resistor configured to receive a heater current; and
a heat sensor disposed over a second side of the piezoelectric layer and opposing the first side, the heat sensor configured to adjust the heater current in response to a temperature of the heating coil.
15. The BAW resonator structure of claim 14 , wherein the piezoelectric layer comprises scandium doped aluminium nitride (ScAlN).
16. The BAW resonator structure of claim 15 , wherein an atomic percentage of scandium in the piezoelectric layer is approximately 0.5% to less than approximately 10.0%.
17. The BAW resonator structure of claim 15 , wherein an atomic percentage of scandium in the piezoelectric layer is approximately 2.5% to less than approximately 5.0%.
18. The BAW resonator structure of claim 14 , further comprising a first conductive trace configured to provide the heater current to the heating coil.
19. The BAW resonator structure of claim 18 , wherein the first conductive trace extends over only one of the plurality of sides.
20. The BAW resonator structure of claim 14 , further comprising a second conductive trace configured to provide heat sensor current to the heat sensor, a change in the temperature of the heating coil causing a corresponding change in sensor resistance of the heat sensor.
21. The BAW resonator structure of claim 20 , wherein the second conductive trace extends over only one of the plurality of sides.
22. The BAW resonator structure of claim 14 , wherein the BAW resonator further comprises a conductive pattern provided in the cavity, the electrical conductor disposed over the outer portion of the pillar being in electrical contact with the conductive pattern.
23. The BAW resonator structure of claim 14 , wherein the material comprises non-etchable borosilicate glass (NEBSG).
24. The BAW resonator structure of claim 14 , wherein the substrate comprises a material having a lower coefficient of thermal conductivity than silicon (Si).
25. The BAW resonator structure of claim 14 , wherein the BAW resonator has an active region that is suspended entirely over the cavity.
26. The BAW resonator structure of claim 14 , wherein the piezoelectric layer comprises rare-earth element doped piezoelectric material.