Patterning of SU-8 resist structures using CF4

Vora, K, Holland, A, Ghantasala, M and Mitchell, A 2004, 'Patterning of SU-8 resist structures using CF4', in J.-C. Chiao et al. (ed.) Proceedings of SPIE - The International Society for Optical Engineering, Perth, Australia, 10 December 2003.

Document type: Conference Paper
Collection: Conference Papers

Title Patterning of SU-8 resist structures using CF4
Author(s) Vora, K
Holland, A
Ghantasala, M
Mitchell, A
Year 2004
Conference name Device and Process Technologies for MEMS, Microelectronics, and Photonics III
Conference location Perth, Australia
Conference dates 10 December 2003
Proceedings title Proceedings of SPIE - The International Society for Optical Engineering
Editor(s) J.-C. Chiao et al.
Publisher SPIE
Place of publication Bellingham
Abstract Carbon Tetraflouride (CF4) plasma etching condition for SU-8 negative photoresist is characterized for its potential applications in photonics and bioMEMS. The effects of main plasma etching parameters such as rf power, gas flow rate, chamber pressure and time were systematically studied and the parameters were optimized by a three-level, L9 orthogonal array of the Taguchi method. By optimization, the optimal parameter range and the weighted percent of each parameter on the final results i.e. depth, surface roughness and wall angle were determined. Photoresist & metal were used and compared as masks for plasma etching. The minimum feature size was 1?m in both cases. Results indicated that with the increase of rf power, etch rate and roughness increases almost linearly. With increase in gas flow rate, etch rate increases while roughness decreases non-linearly. Etch rate is linear with time but roughness is significantly dependent on time initially. The side-wall angle of the samples with metal mask was found to be nearly 90° whereas samples with photoresist as the mask showed poor side-wall angle and surface roughness mainly due to poor mask-resist selectivity. Optimized values of rf power, gas flow rate, time and pressure were found to be 200W, 240sccm, 20minutes and 1Torr respectively, which yielded high etch rate (80nm/min), low surface roughness (5nm) and nearly vertical side-walls (89°).
Subjects Polymers and Plastics
Keyword(s) reactive plasma etching
etch rate
Taguchi optimisation
integrated optics
DOI - identifier 10.1117/12.523903
Copyright notice © 2004 SPIE--The International Society for Optical Engineering.
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