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Proceedings Paper

Creating direct-write gray-scale photomasks with bimetallic thin film thermal resists
Author(s): Glenn H. Chapman; Yuqiang Tu; James Dykes; Masahiko Mio; Jun Peng
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Paper Abstract

New types of analog gray-scale laser direct-write masks have been created using bimetallic thermal resists and a direct- write laser process. Bimetallic resists consist of two layers of thin films, eg. Bi over In or Sn over In, which react to form a low temperature alloy when a laser raises the films above the eutectic temperature. Depending on the exposure energy, resulting alloyed layers appear to become oxides, causing a change of absorption at 365nm from >3OD to <0.3OD. The thermal resists show near wavelength invariance from IR to UV. The Sn/In films, each layer ~40 nm thick, were DC-sputtered onto glass slides or quartz substrates. To make gray-scale photomasks the samples were placed on a computer-controlled high accuracy X-Y table. A bitmap gray-scale pattern was raster-scanned with a CW Argon laser (514 nm) beam. An optical shutter controlled the actual laser power applied onto the thermal resist film according to the gray-scale value. When exposed to a laser beam greater than 0.6 W, the Sn/In film became nearly transparent (0.22OD) at I-line (365nm) wavelength. Sn/In and Bi/In photomasks have been used together with a standard mask aligner to successfully pattern Shipley SPR2FX-1.3 photoresist. CF4/O2 plasma etching has been used to transfer the three-dimensional pattern to SiO2 and Si substrates. Also a 160 beam laser diode thermal imaging tool was used to create BiIn direct-write binary masks.

Paper Details

Date Published: 17 December 2003
PDF: 12 pages
Proc. SPIE 5256, 23rd Annual BACUS Symposium on Photomask Technology, (17 December 2003); doi: 10.1117/12.518213
Show Author Affiliations
Glenn H. Chapman, Simon Fraser Univ. (Canada)
Yuqiang Tu, Simon Fraser Univ. (Canada)
James Dykes, Simon Fraser Univ. (Canada)
Masahiko Mio, Yazaki Corp. (Japan)
Jun Peng, Simon Fraser Univ. (Canada)

Published in SPIE Proceedings Vol. 5256:
23rd Annual BACUS Symposium on Photomask Technology
Kurt R. Kimmel; Wolfgang Staud, Editor(s)

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