A new frontside-release etch-diffusion process for the fabrication of thick Si microstructures

A new frontside-release etch-diffusion process has been developed to create released single crystal Si microstructures without the need for wafer bonding. This frontside-release process is simple and requires only a single mask. A deep dry etch is used to define the structures, followed by a short boron diffusion to convert them to p/sup ++/ Si. A short etch in ethylenediamine pyrocatechol is then used to undercut and release the structures from the frontside of the Si wafer. The structures are isolated from the substrate using a reverse biased p/sup ++//n junction. Since the structures have a high aspect ratio, beams longer than 600 /spl mu/m can be released without sticking to the substrate. Resonant microstructures have been fabricated using this process and their resonant frequency has been measured.