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View Paper |
Session Topic: 3E, Temperature Session |
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Paper Title: Improving Temperature Accuracy for Rapid Thermal Processing at NIST |
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Date & Time: TUESDAY, August 6, 2002 |
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8:30 - 10:00am - PARALLEL SESSIONS - SESSION 3 |
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Speaker: B.K. Tsai
NIST |
Email: tsai@nist.gov |
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At NIST we have been developing methods to improve the temperature measurement accuracy of semiconductor materials undergoing high-temperature thermal processing. In the 600 șC to 1000 șC range, the International Technology Roadmap for Semiconductors (ITRS) requirement is for accuracies of 2 șC traceable to the ITS-90. Because of their remote-sensing convenience and slight disturbance to the wafer thermal environment, lightpipe radiation thermometers (LPRTs) are widely used in RTP tools. At NIST, we have demonstrated new methods for calibrating LPRTs against blackbodies with an uncertainty of 0.2 șC (k = 2), which is a five-fold improvement over calibration accuracy claims by commercial suppliers. As part of this effort, we have established protocols for qualifying lightpipes that will have proper characteristics to assure reliable performance in hot-walled and cold-wall RTP tool chambers. A more challenging issue is how to achieve traceable temperature measurements of such high accuracy on the semiconductor materials in their processing environment. We have studied two approaches: in-situ calibration of the LPRT against an instrumented thin-film thermocouple (TFTC) test wafer; and making model-based corrections, which account for material-chamber radiative properties and chamber geometric arrangement, to spectral radiance temperatures made by an LPRT calibrated against a blackbody. We have achieved uncertainties of 2 șC and 3.5 șC for the two methods, respectively. While the work specifically addresses a semiconductor application, the approaches have general applicability for achieving reliable, traceable temperature measurements using LPRTs in environments where effects due to target emissivity and stray irradiation need to be controlled or characterized. |
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