Published in SPIE Microelectronic Processing Integration, Volume 1594, January 1, 1991, pages 146-152.
Copyright © 1991 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. This paper is also available at http://dx.doi.org/10.1117/12.56629.
NOTE: At the time of publication, the author Richard Savage was not yet affiliated with Cal Poly.
This paper explores the methodologies of real-time measurement of photoresist film thickness on silicon wafers using multi-wavelength reflection interferometry. Reflected light from the wafer's surface, containing the interference profile, is collected in-situ via a fiber optic cable and film thickness is determined in real-time via a pattern recognition algorithm. The instrumentation used to make this measurement and its application toward optimizing track performance during spin-coating and back are discussed. Data demonstrating basic thickness versus spin-time and thickness versus bake-time profiles acquired on-line without process disruption are presented along with its utilization toward minimizing process set-up and machine qualification. Moreover, the advantages of characterizing film thickness on-line and in real-time are reviewed.
Materials Science and Engineering