Suspended Si Microstructures with Rounded Concave and Sharp Convex Corners Using Wafer Bonding and Wet Anisotropic Etching

Abstract

In this paper, we report the fabrication method of suspended silicon microstructures with rounded concave and sharp convex corners of required thickness over controlled etch depth cavities. The fabrication process uses wafer bonding and wet anisotropic etching in pure and surfactant added TMAH. In order to reduce the undercutting at rounded concave and sharp convex corners, various types of non-ionic surfactants namely NC-200, Triton-X-100 and polyethylene glycol (PEG) with very small amount (0.1% by volume) were studied in 25 wt% TMAH solution. The non-ionic surfactants were preferred to preserve the CMOS compatibility of TMAH solution. The aforementioned surfactants were found to be very effective in terms of reducing the undercutting at both types of corners.