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Proceedings Paper

Real-time control of photoresist absorption coefficient uniformity
Author(s): Arthur Tay; Weng-Khuen Ho; Xiaodong Wu; Kuen-Yu Tsai
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Paper Abstract

Critical dimension (CD) or linewidth is one the most critical variable in the lithography process with the most direct impact on the device speed and performance of integrated circuit. The absorption coefficient is one of the photoresist properties that can have an impact on the CD uniformity. The absorption coefficient determined the required exposure dose for printing the features. Hence, nonuniformity in absorption coefficient across the substrate will lead to nonuniformity in the linewidth. This paper presents an innovative approach to controlling the within wafer photoresist absorption coefficient uniformity. Previous works in the literature can only control the average uniformity of the absorption coefficient. Our approach uses an array of spectrometers positioned above a multizone bakeplate to monitor the absorption coefficient. The absorption coefficient can be extracted from the spectrometers data using standard optimization algorithms. With these in-situ measurements, the temperature profile of the bakeplate is controlled in real time by manipulating the heater power distribution using conventional proportional-integral (PI) control algorithm. We have experimentally obtained a repeatable improvement in the absorption coefficient uniformity from wafer-to-wafer and within wafer. A 50% improvement in absorption coefficient uniformity is achieved.

Paper Details

Date Published: 17 May 2005
PDF: 9 pages
Proc. SPIE 5755, Data Analysis and Modeling for Process Control II, (17 May 2005); doi: 10.1117/12.598582
Show Author Affiliations
Arthur Tay, National Univ. of Singapore (Singapore)
Weng-Khuen Ho, National Univ. of Singapore (Singapore)
Xiaodong Wu, National Univ. of Singapore (Singapore)
Kuen-Yu Tsai, Intel Corp. (United States)

Published in SPIE Proceedings Vol. 5755:
Data Analysis and Modeling for Process Control II
Iraj Emami, Editor(s)

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