17 December 2003 Creating direct-write gray-scale photomasks with bimetallic thin film thermal resists
Author Affiliations +
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.
© (2003) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Glenn H. Chapman, Glenn H. Chapman, Yuqiang Tu, Yuqiang Tu, James Dykes, James Dykes, Masahiko Mio, Masahiko Mio, Jun Peng, Jun Peng, } "Creating direct-write gray-scale photomasks with bimetallic thin film thermal resists", Proc. SPIE 5256, 23rd Annual BACUS Symposium on Photomask Technology, (17 December 2003); doi: 10.1117/12.518213; https://doi.org/10.1117/12.518213

Back to Top