Methods and apparatus providing thermal isolation of photonic devices
Described embodiments include photonic integrated circuits and systems with photonic devices, including thermal isolation regions for the photonic devices. Methods of fabricating such circuits and systems are also described.
1. An integrated structure comprising:
a substrate having an upper surface;
a trench formed in the upper surface of the substrate;
a device formation region over the upper surface of the substrate;
a temperature-sensitive photonic device formed in the device formation region;
a heating device formed in the device formation region for heating the temperature-sensitive photonic device, wherein the heating device is located over the trench; and
a thermal isolation region formed directly under the heating device and laterally separated from the temperature-sensitive photonic device such that the thermal isolation region is not formed directly under the temperature-sensing photonic device, wherein the thermal isolation region is located in the trench, such that the thermal isolation region is provided in the upper surface of the substrate, and wherein the thermal isolation region thermally isolates the substrate from the heating device.
2. The integrated structure of claim 1 , wherein the thermal isolation region and the trench both extend under the temperature-sensitive photonic device.
3. The integrated structure of claim 1 , further comprising a waveguide formed in the device formation region, and wherein the thermal isolation region and the trench both extend under the waveguide.
4. The integrated structure of claim 1 , further comprising a waveguide formed in the device formation region, and wherein the waveguide is separated from the trench by a portion of the substrate.
5. The integrated structure of claim 1 , wherein the thermal isolation region comprises a physical gap between the heating device and substrate.
6. The integrated structure of claim 5 , wherein the physical gap is further provided on a side of the heating device.
7. The integrated structure of claim 1 , wherein the thermal isolation region is a first thermal isolation region, and further comprising a second thermal isolation region under the temperature-sensitive photonic device.
8. The integrated structure of claim 7 , wherein the second thermal isolation region is located in the trench.
9. The integrated structure of claim 7 , wherein the first thermal isolation region and the second thermal isolation comprise separate materials.
10. The integrated structure of claim 7 , wherein the trench is a first trench, and wherein the second thermal isolation region is located in a second trench.
11. The integrated structure of claim 1 , wherein the thermal isolation region comprises a low thermal conductivity material within the trench.
12. The integrated structure of claim 11 , wherein the low thermal conductivity material has a thermal conductivity that is less than approximately 0.006 W/cm° C.
13. The integrated structure of claim 11 , wherein the low thermal conductivity material comprises an oxide doped with a material having a lower thermal conductivity than the oxide.
14. The integrated structure of claim 11 , wherein the low thermal conductivity material comprises silicon dioxide that has been doped with a dopant having a lower dielectric constant than the silicon dioxide.
15. The integrated structure of claim 14 , wherein the dopant comprises fluorine or carbon.
16. The integrated structure of claim 11 , wherein the low thermal conductivity material comprises porous silicon dioxide.
17. The integrated structure of claim 11 , wherein the low thermal conductivity material comprises spin-on silicon dioxide.
18. The integrated structure of claim 1 , wherein the temperature-sensitive photonic device comprises a carrier wave modulator.
19. The integrated structure of claim 1 , wherein the temperature-sensitive photonic device comprises a laser.
20. The integrated structure of claim 1 , wherein the trench and the thermal isolation region form a shallow trench isolation region.