Microsystem Technologies

, Volume 8, Issue 4, pp 308–313

Reduction of diffraction effect of UV exposure on SU-8 negative thick photoresist by air gap elimination

  • Y.-J. Chuang
  • F.-G. Tseng
  • W.-K. Lin

DOI: 10.1007/s00542-002-0176-8

Cite this article as:
Chuang, YJ., Tseng, FG. & Lin, WK. Microsystem Technologies (2002) 8: 308. doi:10.1007/s00542-002-0176-8

Abstract

 This paper reports a novel way to compensate the air gap between photomask and photoresist for eliminating UV light diffraction on photoresist, which greatly increases the sidewall straightness of high-aspect-ratio resist structures. In this research, SU-8 negative tone photoresist was used for experiments, and glycerol was employed as an index match material for bridging air gap between photomask and photoresist during exposure. Results showed that a high aspect ratio wall structure of 156 μm thick and 25 μm wide had a 45% pattern width error when exposed under 100 μm air gap, while glycerol compensated process accomplished a straight resist wall without appreciable error. This method is simple and cheap to employ, compared to the usage of costly thick-photoresist-film spinner for resist planarization. Numerical simulation on the diffraction effect upon the structure wall has also been conducted. The calculated and experiment wall profiles showed similarity in trend.

Copyright information

© Springer-Verlag Berlin Heidelberg 2002

Authors and Affiliations

  • Y.-J. Chuang
    • 1
  • F.-G. Tseng
    • 1
  • W.-K. Lin
    • 1
  1. 1.Department of Engineering and System Science, National Tsing Hua University, Hsinchu, Taiwan, China e-mail: fangang@ess.nthu.edu.twTW

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