Creating precise 3D microstructures using laser direct-write bimetallic thermal resist grayscale photomasks

Glenn H. Chapman; James Dykes; David Poon; Chinheng Choo; Jun Wang; Jun Peng; Yuqiang Tu

doi:10.1117/12.601545

12 April 2005 Creating precise 3D microstructures using laser direct-write bimetallic thermal resist grayscale photomasks

Glenn H. Chapman, James Dykes, David Poon, Chinheng Choo, Jun Wang, Jun Peng, Yuqiang Tu

Author Affiliations +

Proceedings Volume 5713, Photon Processing in Microelectronics and Photonics IV; (2005) https://doi.org/10.1117/12.601545
Event: Lasers and Applications in Science and Engineering, 2005, San Jose, California, United States

Abstract

Previous research demonstrated Sn/In and Bi/In bimetallic thermal resists are promising new materials for direct-write analogue grayscale photomask processes. These materials turn transparent with increased laser exposure power and their optical density changes smoothly from 3 OD when unexposed to less than 0.22 OD when fully exposed. The transparency is the result of an oxidation process that is controllable with exposure to generate the grayscale levels in the photomask. In order to produce precise 3D structures in regular photoresists, the steps involved in microlithography must be quantified and examined. The lithographic process includes drawing 8-bit grayscale bitmap patterns, computer-aided laser writing photomasks on bimetallic films, and regular photoresist exposure using a mask-aligner. Compensation during the mask-writing process was necessary since the relationship between the optical density of the exposed bimetallic films and the laser writing power was not completely linear. In addition, the response of the photoresists to the mask exposure time was also a non-linear relationship. To investigate the resolution limit for Bi/In and Sn/In bimetallic thermal resists as a masking material, we used a modified form of interference lithography to expose and develop structures in Bi/In resists with widths that are less than 200 nm. As a result of the lithography, we were able to create structures in the Bi/In films that are up to 20 times smaller than previously obtained using the direct-write method.

Citation Download Citation

Glenn H. Chapman, James Dykes, David Poon, Chinheng Choo, Jun Wang, Jun Peng, and Yuqiang Tu "Creating precise 3D microstructures using laser direct-write bimetallic thermal resist grayscale photomasks", Proc. SPIE 5713, Photon Processing in Microelectronics and Photonics IV, (12 April 2005); https://doi.org/10.1117/12.601545

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