Method and apparatus for monitoring a microstructure etching process
An etching monitoring apparatus and related method for use in the manufacture of microstructures (and in particular MEMS) located within an etching chamber is described. The apparatus and related method operates by setting the temperature of the chamber within which the microstructure is located at a starting temperature, and maintaining the partial pressure of an etching gas within the chamber at a constant value. As a result the surface temperature of the micro structure within the chamber is primarily determined by the etch rate. Therefore, by employing a thermometer to monitor the change in etching surface temperature, a direct diagnostic for monitoring the etching process is provided.
1. An etching monitoring apparatus suitable for use with an etching chamber, the etching monitoring apparatus comprising:
a pressure controller for controlling a partial pressure of an etching gas;
a temperature controller for setting a starting temperature of the etching chamber; and
a thermometer for monitoring a surface temperature of a microstructure being etched within the chamber.
2. The etching monitoring apparatus as claimed in claim 1 further comprising a feedback loop such that the thermometer is employed to regulate the pressure controller.
3. The etching monitoring apparatus as claimed in claim 2 wherein the feedback loop also allows the thermometer to regulate the temperature controller.
4. The etching monitoring apparatus as claimed in claim 1 wherein the pressure controller comprises a gas flow controller such that the gas flow controller provides a means for regulating the flow of the etching gas.
5. The etching monitoring apparatus as claimed in claim 1 wherein the thermometer comprises a non-contact temperature sensor.
6. The etching monitoring apparatus as claimed in claim 5 wherein the non-contact temperature sensor comprises at least one pyrometer.
7. The etching monitoring apparatus as claimed in claim 5 wherein the non-contact temperature sensor is a thermal imaging camera.
8. An etching chamber suitable for etching one or more microstructures comprising an etching monitoring apparatus, the etching monitoring apparatus comprising:
a pressure controller for controlling a partial pressure of an etching gas;
a temperature controller for setting a starting temperature of the etching chamber; and
a thermometer for monitoring a surface temperature of one or more microstructures being etched within the chamber.
9. The etching chamber as claimed in claim 8 wherein the apparatus further comprises a feedback loop such that the thermometer is employed to regulate the pressure controller.
10. The etching chamber as claimed in claim 9 wherein the feedback loop allows the thermometer to regulate the temperature controller.
11. The etching chamber as claimed in claim 8 wherein the pressure controller comprises a gas flow controller such that the gas flow controller provides a means for regulating the flow of the etching gas.
12. The etching chamber as claimed in claim 8 wherein the thermometer comprises a non-contact temperature sensor.
13. The etching chamber as claimed in claim 12 wherein the non contact temperature sensor comprises at least one pyrometer.
14. The etching chamber as claimed in claim 12 wherein the non contact temperature sensor is a thermal imaging camera.
15. The etching chamber as claimed in claim 8 wherein the etching chamber further comprises a pedestal upon which the microstructure to be etched is located.
16. The etching chamber as claimed in claim 8 wherein the etching chamber further comprises a window.
17. The etching chamber as claimed in claim 16 wherein the window is transparent to infra red electromagnetic radiation.
18. The etching chamber as claimed in claim 16 wherein the window comprises Zinc Selenide.
19. The etching chamber as claimed in claims 8 wherein the etching chamber further comprises a lid.
20. The etching chamber as claimed in claim 19 wherein the window is located on the lid.
21. The etching chamber as claimed in claim 20 wherein the thermometer is located coincident with the window on the lid.
22. A method of monitoring the progress of an etching process of a microstructure located within an etching chamber, the method comprising the steps of:
setting a starting temperature of the chamber;
controlling the pressure of an etching gas within the chamber;
monitoring variation in a surface temperature of the microstructure being etched.
23. The method of monitoring the progress of an etching process of a microstructure as claimed in claim 22 wherein the step of setting the starting temperature of the chamber comprises setting the temperature of a pedestal upon which the microstructure is located.
24. The method of monitoring the progress of an etching process of a microstructure as claimed in claim 22 wherein the method further comprises the step of comparing the monitored surface temperature with a predetermined standard temperature curve.
25. The method of monitoring the progress of an etching process of a microstructure as claimed in claim 22 wherein the method further comprises the step of comparing the surface temperature of the microstructure to be etched with the starting temperature so as to determine an etch endpoint.
26. The method of monitoring the progress of an etching process of a microstructure as claimed in claim 25 wherein the step of controlling the pressure in the chamber comprises the step of reducing the partial pressure of the etching gas in the chamber as the etch process approaches the endpoint.
27. The method of monitoring the progress of an etching process of a microstructure as claimed in claim 22 wherein the step of monitoring the variation in the surface temperature of the microstructure involves the employment of one or more remote temperature sensors.
28. The method of monitoring the progress of an etching process of a microstructure as claimed in claim 22 wherein the step of controlling the pressure in the chamber comprises maintaining the pressure at a substantially constant value.
29. The method of monitoring the progress of an etching process of a microstructure as claimed in claim 22 wherein the step of controlling the pressure in the chamber comprises the step of controlling the flow of the etching gas into the chamber.