Transmission-based temperature measurement of a workpiece in a thermal processing system
A thermal processing system for performing thermal processing can include a workpiece support plate configured to support a workpiece and heat source(s) configured to heat the workpiece. The thermal processing system can include window(s) having transparent region(s) that are transparent to electromagnetic radiation within a measurement wavelength range and opaque region(s) that are opaque to electromagnetic radiation within a portion of the measurement wavelength range. A temperature measurement system can include a plurality of infrared emitters configured to emit infrared radiation and a plurality of infrared sensors configured to measure infrared radiation within the measurement wavelength range where the transparent region(s) are at least partially within a field of view the infrared sensors. A controller can be configured to perform operations including obtaining transmittance and reflectance measurements associated with the workpiece and determining, based on the measurements, a temperature of the workpiece less than about 600° C.
1. A thermal processing system for performing thermal processing of a semiconductor workpiece, the thermal processing system comprising:
a workpiece support plate configured to support a workpiece;
one or more heat sources configured to heat the - workpiece;
a window disposed between the workpiece support plate and the one or more heat sources, the window comprising one or more transparent regions that are transparent to at least a portion of electromagnetic radiation within a measurement wavelength range; and
a temperature measurement system configured to obtain a temperature measurement indicative of a temperature of the workpiece, the temperature measurement system comprising:
at least one infrared emitter configured to emit infrared radiation;
at least one infrared sensor, the at least one infrared sensor configured to measure infrared radiation within the measurement wavelength range and disposed such that at least one of the one or more transparent regions is at least partially within a field of view of the at least one infrared sensor; and
a controller configured to perform operations, the operations comprising:
obtaining, from the at least one infrared sensor, one or more first measurements associated with the workpiece;
determining, based at least in part on the one or more first measurements, a temperature of the workpiece when the temperature of the workpiece is less than about 600° C.
2. The thermal processing system of claim 1 , wherein the operations further comprise:
obtaining, from the at least one infrared sensor, one or more second measurements associated with the workpiece; and
determining, based at least in part on the one or more second measurements, a temperature of the workpiece when the temperature of the workpiece is greater than about 600° C.
3. The thermal processing system of claim 2 , wherein the one or more first measurements are associated with a different optical measurement of the workpiece relative to the one or more second measurements.
4. The thermal processing system of claim 2 , wherein the one or more first measurements associated with the workpiece comprise one or more transmittance measurements and one or more reflectance measurements.
5. The thermal processing system of claim 4 , wherein the one or more second measurements comprise one or more emission measurements associated with the workpiece.
6. The thermal processing system of claim 1 , wherein the at least one infrared emitter comprises a center emitter operable to emit radiation towards a center portion of the workpiece and an edge emitter operable to emit radiation towards an edge portion of the workpiece, and wherein the at least one infrared sensor comprises a center sensor corresponding to the center emitter and an edge sensor corresponding to the edge emitter.
7. The thermal processing system of claim 1 , wherein the one or more heat sources are configured to emit broadband radiation to heat the workpiece.
8. The thermal processing system of claim 7 , wherein the window comprises one or more opaque regions are configured to block at least a portion of the broadband radiation emitted by the heat sources and within the measurement wavelength range.
9. The thermal processing system of claim 8 , wherein the one or more opaque regions comprise hydroxyl doped quartz and wherein the one or more transparent regions comprise hydroxyl free quartz.
10. The thermal processing system of claim 1 , wherein the at least one infrared emitter is pulsed at a pulsing frequency.
11. The thermal processing system of claim 10 , wherein the pulsing frequency is 130 Hz.
12. The thermal processing system of claim 1 , wherein the measurement wavelength range comprises at least one of 2.3 micrometers or 2.7 micrometers.
13. The thermal processing system of claim 1 , wherein the at least one infrared sensor comprises one or more pyrometers.
14. The thermal processing system of claim 1 , wherein the operation of determining, based at least in part on the one or more first measurements, a temperature of the workpiece when the temperature of the workpiece is less than about 600° C. comprises:
determining, based at least in part on a first transmittance measurement and a reflectance measurement, an emissivity of the workpiece; and
determining, based at least in part on a second transmittance measurement and the emissivity of the workpiece, the temperature of the workpiece.
15. The thermal processing system of claim 14 , wherein the at least one first transmittance measurement and the at least one reflectance measurement are associated with a first wavelength of the measurement wavelength range and the at least one second transmittance measurement is associated with a second wavelength of the measurement wavelength range.
16. The thermal processing system of claim 1 , wherein the controller is configured to determine a reference intensity for at least one of the plurality of infrared sensors when no workpiece is present in the workpiece processing system by performing operations comprising:
emitting a first amount of infrared radiation from the at least one infrared emitter;
determining a second amount of infrared radiation incident on the at least one infrared sensor; and
determining the reference intensity associated with the at least one emitter and the at least one sensor based at least in part on a variation between the first amount of infrared radiation and the second amount of infrared radiation.
17. A method for determining a temperature of a workpiece in a thermal processing system, the thermal processing system comprising a workpiece support plate configured to support a workpiece; one or more heat sources configured to heat the workpiece; a window disposed between the workpiece support plate and the one or more heat sources, the window comprising one or more transparent regions that are transparent to at least a portion of electromagnetic radiation within a measurement wavelength range; at least one infrared emitter configured to emit infrared radiation; and at least one infrared sensor, the at least one infrared sensor configured to measure infrared radiation within the measurement wavelength range and disposed such that at least one of the one or more transparent regions is at least partially within a field of view of the at least one infrared sensor, the method comprising:
obtaining, from the at least one infrared sensor, one or more first measurements associated with the workpiece;
determining, based at least in part on the one or more first measurements, a temperature of the workpiece when the temperature of the workpiece is less than about 600° C.
18. The method of claim 17 , wherein the method further comprises:
obtaining, from the at least one infrared sensor, one or more second measurements associated with the workpiece; and
determining, based at least in part on the one or more second measurements, a temperature of the workpiece when the temperature of the workpiece is greater than about 600° C.