This article presents a method capable of easily identifying the membrane thickness of micro-sensors by a V-groove depth ruler that has been made in advance on silicon wafers before sensor fabrication. The proposed method not only provides a viable alternative to other etch-stop techniques, but can also be used as an in situ tool for depth or thickness monitoring with micrometer resolution. Without p+ diffusion or an n-epitaxial layer on silicon substrates, the batch processing capability of silicon piezoresisitve micro-sensors can be preserved with V-grooves. Furthermore, the method proposed herein could also calibrate the etching rate of anisotropic etching solutions, check the uniformity of pressure sensors and offer guidelines on how to further improve the batch process of silicon bulk micro-machining. Moreover, a revised shape of V-groove depth ruler with self-alignment capability is also proposed herein.
Journal of micromechanics and microengineering 8(3), pp.182-187