Optical monitoring and control of Si wet etching

Abstract

Light can be used to monitor and control anisotropic etching of silicon. For in situ monitoring of the Si-thickness during anisotropic wet etching in KOH, a technique based on transmission spectroscopy has been investigated. Using special self-calibrating, recursive algorithms, thickness of Si membranes can be measured in the range between 10 and 500 μm. Illuminating the Si-surface during etching with a high light intensity, etch rate of c-Si in KOH can be controlled by illumination of the silicon surface. This method might be used for maskless fabrication of simple micromechanical devices.