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Proceedings Paper

Ultrasonic monitoring of photoresist processing
Author(s): Susan L. Morton; F. Levent Degertekin; Butrus T. Khuri-Yakub
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Paper Abstract

A high frequency ultrasonic technique has been developed to monitor photoresist processing in situ during semiconductor manufacturing. Photoresist pre-exposure bake and development have been monitored using the sensor, and the post-exposure bake has been studies as well. The in-situ glass transition temperature (Tg) was determined during the prebake for I-line films down to 0.6micrometers as well as for chemically- amplified DUV resist of similar thicknesses. Using classical reflection theory, photoresist properties such as the density, thickness and acoustic velocity were determined during processing. This in situ parameter inversion method can be used to determine process endpoint if the optimal density, velocity, and thickness are predetermined. The Tg for post-exposure bake of I-line resists is expected to be the Tg of the novolac resin alone, without solvent present. Measurements using the described sensor have confirmed that the resin Tg during postbake is 118 degrees C, the value of Tg provided by Shipley. This provides a measurement of postbake as well as a confirmation that the sensor is measuring Tg accurately. The development process was also monitored using this sensor. Results prove the usefulness of this sensor for in situ measurements of resist thickness changes during development. This was verified for different exposure doses and for resist coated on a wafer with circuit topography.

Paper Details

Date Published: 14 June 1999
PDF: 8 pages
Proc. SPIE 3677, Metrology, Inspection, and Process Control for Microlithography XIII, (14 June 1999); doi: 10.1117/12.350823
Show Author Affiliations
Susan L. Morton, Stanford Univ. (United States)
F. Levent Degertekin, Stanford Univ. (United States)
Butrus T. Khuri-Yakub, Stanford Univ. (United States)

Published in SPIE Proceedings Vol. 3677:
Metrology, Inspection, and Process Control for Microlithography XIII
Bhanwar Singh, Editor(s)

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