A Study on the Sub-Micron LIGA Process

Abstract

Microstructures with sub-micron widths and gaps (lines and spaces) can be applied to practical and high performance MEMS devices. In the sub-micron LIGA process, one of the most crucial considerations is the fabrication of an X-ray mask with thick X-ray absorbers having sub-micron width. An X-ray mask, which is composed of 1μm-thick Au with a 0.6μm line width and a 0.2μm space as absorbers, 2μm-thick SiC with 240MPa of tensile stress as a membrane and 625μm-thick Si as a frame, was fabricated. As a result of the sub-micron LIGA process, a sub-micron PMMA structure with a maximum aspect ratio of 85, corresponding to 0.2μm minimum width, 6μm length and 17μm height, and sub-micron Ni structures with a maximum aspect ratio of 75, corresponding to 0.2μm minimum width and 15μm height, were fabricated.