A process fabricate 100 m high aspect ratio micro-optical structures by direct X-ray exposure and development of polymethylsilsesquoixane spin- on glass (GR 650) is presented. This process is an advance over the previous process of fabrication micro-optical components by molding GR 650 using polymethylmethacrylate (PMMA) molds patterned by deep X-ray lithography (DXRL). The process presented in this article utilizes GR 650 as a DXRL resist. The polymethylsilsesquoixane is converted to silica on the surface exposed to air, and cross linked throughout the bulk. X-ray irradiated regions are then selectively retained by development in an organic solvent. A technique to cast 100 m thick GR 650 films was established. Although the height of the structures fabricated was 100 m, this technique can be extended to larger structural heights. An alternative positive tone process was also developed in which the irradiated regions of GR 650 films are etched in buffered HF. The structural height achieved by positive tone processing, however, was limited to 15 (mu) m, which is the depth of conversion to silica. Surface and bulk compositions of the irradiated films were measured by XPS and Fourier Transform infrared spectroscopy.

Date Published: 18 August 2000
PDF: 8 pages
Proc. SPIE 4179, Micromachining Technology for Micro-Optics, (18 August 2000); doi: 10.1117/12.395695

Published in SPIE Proceedings Vol. 4179:
Micromachining Technology for Micro-Optics
Sing H. Lee; Eric G. Johnson, Editor(s)