Systems and methods for thermal processing and temperature measurement of a workpiece at low temperatures
Systems and methods for thermal processing of a workpiece at low temperatures are disclosed. In one example implementation, a thermal processing apparatus includes a processing chamber having a workpiece support. The workpiece support can be configured to support a workpiece. The apparatus can include one or more heat sources configured to emit electromagnetic radiation in a first wavelength range to heat the workpiece to a processing temperature. The processing temperature can be in the range of about 50° C. to 150° C. The apparatus can include one or more sensors configured to obtain a measurement of electromagnetic radiation in a second wavelength range when the workpiece is at the processing temperature. The second wavelength range can be different from the first wavelength range.
1. A thermal processing apparatus comprising:
a processing chamber having a workpiece support, the workpiece support configured to support a workpiece;
a first heat source and a second heat source, each of the first and second heat source configured to emit electromagnetic radiation in a first wavelength range in a range from about 850 nanometers to about 950 nanometers to heat the workpiece to a processing temperature of from about 50° C. to about 150° C., wherein the first heat source is configured to heat a top surface of the workpiece and the second heat source is configured to heat a backside of the workpiece;
one or more additional radiation sources configured to emit electromagnetic radiation in a second wavelength range, wherein the second wavelength range comprises a wavelength from about 7 micrometers to about 12 micrometers, wherein the workpiece is at least partially transparent to the electromagnetic radiation in the second wavelength range;
a first sensor configured to obtain a measurement of electromagnetic radiation in the second wavelength range when the workpiece is at the processing temperature, wherein the second wavelength range does not overlap with the first wavelength range, wherein a spectral power density associated with the radiation from the heat source in the second wavelength range is less than about 5% of a peak spectral power density associated with the second wavelength range; and
a first window disposed between the first heat source and the workpiece and a second window disposed between the second heat source and the workpiece, the first window and second window configured to restrict wavelengths other than the second wavelength range, the first window and second window each having a first side facing the workpiece and a second and opposite side, wherein the first window and the second window comprise quartz.
2. The thermal processing apparatus of claim 1 , comprising one or more processors configured to determine a temperature of the workpiece based at least in part on the measurement of electromagnetic radiation obtained by the one or more sensors.
3. The thermal processing apparatus of claim 1 , wherein the one or more heat sources emit electromagnetic radiation in a narrow band infrared range.
4. The thermal processing apparatus of claim 1 , wherein the first wavelength range is such that the workpiece has an absorptance of greater than about 0.5 at the first wavelength range and at the processing temperature.
5. The thermal processing apparatus of claim 1 , wherein the apparatus comprises a cooled aperture or a cooled tube to restrict a field of view of the one or more sensors.
6. The thermal processing apparatus of claim 1 , wherein the one or more sensors are configured to measure electromagnetic radiation in the second wavelength range during a time period when the one or more heat sources are not emitting electromagnetic radiation in the first wavelength range.
7. The thermal processing apparatus of claim 1 , wherein the one or more heat sources comprise one or more light emitting diodes.
8. The thermal processing apparatus of claim 1 , wherein the workpiece comprises lightly-doped silicon.
9. The thermal processing apparatus of claim 1 , wherein the electromagnetic radiation in the second wavelength range passes through the workpiece prior to being measured by the one or more sensors.
10. The thermal processing apparatus of claim 9 , wherein the second wavelength range comprises a wavelength longer than about 1000 nanometers.
11. The thermal processing apparatus of claim 1 , wherein the measurement obtained by the one or more sensors is indicative of a transmittance of the workpiece, wherein the apparatus comprises one or more processors are configured to determine the temperature of the workpiece at least in part by comparing the measurement obtained by the one or more sensors indicative of the transmittance of the workpiece to a reference transmittance spectrum for a specimen having a known initial temperature.
12. The thermal processing apparatus of claim 1 , wherein the apparatus comprises one or more processors are configured to determine the temperature of the workpiece based at least in part on an emissivity of the workpiece, wherein the emissivity of the workpiece is measured in-situ.
13. The thermal processing apparatus of claim 1 , wherein the one or more additional radiation sources are positioned such that the emitted radiation is within about 10° of perpendicular to a surface of the workpiece.
14. The thermal processing apparatus of claim 1 , wherein the one or more additional radiation sources are positioned behind either the first window or the second window.