Heater elements

1 . A structure comprising:

an active device;

a heater element under the active device and within a semiconductor substrate;

a contact to the active device and providing current to the heater element; and

an airgap below the heater element.

2 . The structure of claim 1 , wherein the active device comprises a heterojunction bipolar transistor comprising a collector region, a sub-collector region, a base region and an emitter and the semiconductor substrate comprises a bulk substrate.

3 . The structure of claim 2 , wherein the contact is electrically connected to the collector region.

4 . The structure of claim 2 , wherein the heater element is separated from the sub-collector region by an isolation region of the active device.

5 . The structure of claim 4 , wherein the heater element is electrically isolated from the sub-collector region by shallow trench isolation structures.

6 . The structure of claim 2 , wherein the heater element and the sub-collector region comprise an N-type semiconductor material.

7 . The structure of claim 1 , wherein the heater element includes a main body and a reach through extending from a surface of the semiconductor substrate to the main body.

8 . The structure of claim 1 , further comprising a non-single crystal semiconductor region below the airgap.

9 . The structure of claim 1 , further comprising a plurality of airgaps below the heater element.

10 . The structure of claim 1 , wherein the heater element includes multiple fingers.

11 . The structure of claim 1 , further comprising a performance sensor, a heat sensor and control circuitry, the performance sensor detects a change in circuit performance of the active device, the control circuit receives the circuit performance from the performance sensor and governs whether the active device should be heated to anneal defects, and the heat sensor detects heat generated from the heater element.

12 . A structure comprising:

a heterojunction bipolar transistor integrated with a semiconductor substrate;

a heater element in the semiconductor substrate and which surrounds the heterojunction bipolar transistor;

a contact to the heterojunction bipolar transistor and which provides a current the heater element;

a shallow trench isolation structure isolating the heterojunction bipolar transistor from the heater element; and

at least one airgap below the heater element.

13 . The structure of claim 12 , wherein the heterojunction bipolar transistor comprises a collector region, a sub-collector region, a base region and an emitter, and the contact is electrically connected to the sub-collector region.

14 . The structure of claim 13 , wherein the heater element and the sub-collector region comprise an N-type semiconductor material, and the heater element is electrically isolated from the sub-collector region by the collector region and the shallow trench isolation structure.

15 . The structure of claim 12 , wherein the heater element includes a main body and a reach through extending from a surface of the semiconductor substrate to the main body, and the reach through surrounds the shallow trench isolation structure.

16 . The structure of claim 12 , further comprising a non-single crystal semiconductor region below the at least one airgap.

17 . The structure of claim 12 , wherein the heater element includes a reach through completely surrounding the heterojunction bipolar transistor.

18 . A device structure comprising:

an active device;

a heater element surrounding the active device, wherein the heater element is under the active device and within a semiconductor substrate;

an airgap below the heater element;

a performance sensor configured to detect a change in performance of the active device;

a heat sensor configured to detect heat generated from the heater element; and

control circuitry configured to activate the heater element when the performance sensor detects performance degradation in the active device.