A convex-corner preservation principle in bulk micromachining and its application to nano-point needles

A 150 /spl mu/m-height spired structure having a 50 nm of summit curvature was batch fabricated. The process is a self-convergent bulk micromachining using a commercially-available fused quartz wafer. 2500 probes are available from one 5-inch square quartz wafer, so that the structure can readily be applied to low-cost volume production of SPM/SNOM probes. Moreover, the important discovery in the present work is the fundamental principle that is often misunderstood or ignored by MEMS researchers: convex corners are unexceptionally preserved by isotropic etching. The principle will allow many researchers to obtain nanoscopic structures in simple processing.