Micro-Pirani vacuum gauges
Micro-Pirani gauge vacuum gauges are described that use low-thermal conductivity support elements. A micro-Pirani gauge or vacuum sensor can include a heating element operative to heat a gas and to produce a signal corresponding to the pressure of the gas; a platform configured to receive the heating element, with the platform having a first coefficient of thermal conductivity; and a support element connected to a substrate and configured to support the platform with the heating element within an aperture disposed in the substrate, with the support element having a second coefficient of thermal conductivity, where the second coefficient of thermal conductivity is less than the first coefficient of thermal conductivity. Multimode pressure sensing including a micro-Pirani gauge are also described.
1. A micro-Pirani vacuum sensor comprising:
a heating element operative to heat a gas and to produce a signal corresponding to the pressure of the gas;
a platform configured to receive the heating element, wherein the platform has a first coefficient of thermal conductivity; and
a support element connected to a substrate and configured to support the platform with the heating element within an aperture disposed in the substrate, wherein the support element has a second coefficient of thermal conductivity, and wherein the second coefficient of thermal conductivity is less than the first coefficient of thermal conductivity.
2. The micro-Pirani sensor of claim 1 , wherein the second coefficient of thermal conductivity is at least one order of magnitude less than the first coefficient of thermal conductivity.
3. The micro-Pirani sensor of claim 1 , wherein the second coefficient of thermal conductivity is at least two orders of magnitude less than the first coefficient of thermal conductivity.
4. The micro-Pirani sensor of claim 1 , wherein the second coefficient of thermal conductivity is less than or equal to 0.2 W/mK.
5. The micro-Pirani sensor of claim 1 , wherein the support element comprises parylene, polyamide, polyimide, polytetrafluoroethylene (PTFE), silicon oxide, or silicon nitride.
6. The micro-Pirani sensor of claim 1 , wherein the support element comprises a continuous diaphragm.
7. The micro-Pirani sensor of claim 1 , wherein the support element is perforated or patterned.
8. The micro-Pirani sensor of claim 1 , wherein the heating element comprises nickel, titanium, platinum, silicon or polysilicon.
9. The micro-Pirani sensor of claim 1 , wherein the heating element comprises a material having a temperature coefficient of resistance greater than or equal to 0.003/° C.
10. The micro-Pirani sensor of claim 1 , wherein the platform comprise aluminum nitride, silicon nitride, sapphire, diamond, or aluminum oxide.
11. The micro-Pirani sensor of claim 1 , wherein the heating element is disposed within the platform and not directly exposed to the gas.
12. The micro-Pirani sensor of claim 1 , wherein the platform is disposed within the support element and not directly exposed to the gas.
13. The micro-Pirani sensor of claim 1 , further comprising a cap connected to the substrate and covering the support element, wherein the cap is configured to form a volume with a gap between a wall of the cap and the support element supporting the platform, wherein gap is a desired size, and wherein the gap provides a mean free path of a desired size for gas molecules within the volume.
14. The micro-Pirani sensor of claim 1 , wherein the micro-Pirani vacuum sensor has a dynamic range of pressure measurement that includes 1×10E-6 Torr.
15. A dual-mode vacuum sensor comprising:
(A) a first vacuum sensor with a first dynamic range of pressure measurement, the first vacuum sensor comprising a micro-Pirani vacuum sensor having,
(i) a heating element operative to heat a gas and to produce a signal corresponding to the pressure of the gas;
(ii) a platform configured to receive the heating element, wherein the platform has a first coefficient of thermal conductivity; and
(iii) a support element connected to a substrate and configured to support the platform with the heating element within an aperture disposed in the substrate, wherein the support element has a second coefficient of thermal conductivity, and wherein the second coefficient of thermal conductivity is less than the first coefficient of thermal conductivity; and
(B) a second vacuum sensor having a second dynamic range of pressure measurement.
16. The dual-mode vacuum sensor of claim 15 , wherein the second coefficient of thermal conductivity is at least one order of magnitude less than the first coefficient of thermal conductivity.
17. The dual-mode vacuum sensor of claim 15 , wherein the second coefficient of thermal conductivity are less than or equal to 0.2 W/mK.
18. The dual-mode vacuum sensor of claim 15 , wherein the support element comprises parylene, polyamide, polyimide, or polytetrafluoroethylene (PTFE).
19. The dual-mode vacuum sensor of claim 15 , wherein the support element comprises a continuous diaphragm.
20. The dual-mode vacuum sensor of claim 15 , wherein the support element is perforated or patterned.
21. The dual-mode vacuum sensor of claim 15 , wherein the heating element comprises nickel, titanium, platinum, silicon or polysilicon.
22. The dual-mode vacuum sensor of claim 15 , wherein the heating element comprises a material having a temperature coefficient of resistance greater than or equal to 0.003/° C.
23. The dual-mode vacuum sensor of claim 15 , wherein the platform comprise aluminum nitride, silicon nitride, sapphire, diamond, or aluminum oxide.
24. The dual-mode vacuum sensor of claim 15 , wherein the heating element is disposed within the platform and not directly exposed to the gas.
25. The dual-mode vacuum sensor of claim 15 , wherein the platform is disposed within the support element and not directly exposed to the gas.
26. The dual-mode vacuum sensor of claim 15 , further comprising a cap connected to the substrate and covering the support element, wherein the cap is configured to form a volume with a gap between a wall of the cap and the support element supporting the platform, wherein gap is a desired size, and wherein the gap provides a mean free path of a desired size for gas molecules within the volume.
27. The dual-mode vacuum sensor of claim 15 , wherein the micro-Pirani vacuum sensor has a dynamic range of pressure measurement that includes 1×10E-6 Torr.
28. The dual-mode vacuum sensor of claim 15 , wherein the second sensor comprises a micro-Pirani vacuum sensor.
29. The dual-mode vacuum sensor of claim 15 , wherein the second sensor comprises a capacitance manometer.
30. The dual-mode vacuum sensor of claim 15 , wherein the second sensor comprises a piezoresistive manometer.
31. The dual-mode vacuum sensor of claim 15 , wherein the second sensor comprises a resonator pressure sensor.
32. A method of manufacturing a micro-Pirani vacuum sensor, the method comprising:
depositing a first layer of platform material on a first side of a substrate;
depositing heating element material on the first layer of platform material;
depositing a second layer of platform material on the heating element material and the first layer of platform material together;
forming a platform supporting the heating element material;
depositing a first layer of support element material over at least a portion of the substrate and at least a portion of the platform, wherein the support element material has a lower coefficient of thermal conductivity than that of the platform material; and
removing substrate material adjacent to the platform, wherein an aperture is made in the substrate, and exposing a portion of the platform and the first layer of support element material.
33. The method of claim 32 , further comprising depositing a second layer of material on the second side of the substrate and on the exposed portion of the platform and first layer of support element material.
34. The method of claim 32 , further comprising providing a substrate having a passivation layer on first and second sides.
35. The method of claim 34 , wherein the passivation layer comprises silicon oxide or silicon nitride.
36. The method of claim 32 , wherein depositing a first layer of support element material comprises depositing the material over an entire extent of a surface of the platform.
37. The method of claim 32 , wherein the support element material comprises parylene, polyamide, polyimide, or polytetrafluoroethylene (PTFE).
38. The method of claim 32 , wherein removing substrate material adjacent to the platform comprises backside etching.
39. The method of claim 32 , wherein depositing a first layer of support element material comprises patterning an exposed area of the platform.