Fast and blister-free irradiation conditions for cross-linking of PMMA induced by 2 MeV protons

• Main Authors: Unai S., Puttaraksa N., Pussadee N., Singkarat K., Rhodes M.W., Whitlow H.J., Singkarat S.
• Format: Conference or Workshop Item
• Language: English
• Published: 2014
• Online Access: http://www.scopus.com/inward/record.url?eid=2-s2.0-84869083589&partnerID=40&md5=78a304c96fa9315dbdd5870d7b09fd83; http://cmuir.cmu.ac.th/handle/6653943832/6791
• Institution: Chiang Mai University

For soft lithography, the conventional negative tone resists, such as SU-8, that are used to create the mold have a number of drawbacks. PMMA, which is normally used as a positive tone resist, can be used as a negative resist by using high-fluence irradiation conditions. In this report, we outline optimization of the irradiation conditions for PMMA thin films using 2 MeV H + ions to exploit their ability to work as a negative tone resist at ion fluences above 1.0 × 10 15 ions cm -2. The main aim was to induce cross-linking while maintaining the exposed regions free of blisters and maintaining short irradiation times. We found that by using a two-step process with a low-flux irradiation, followed by a high-flux irradiation, the exposure time could be shortened by ∼50%. We also found that ion fluences greater than 5.0 × 10 15 ions cm -2 minimized the distortion in stitched regions. © 2011 Elsevier B.V. All rights reserved.