Shape deterioration of mesa structures in post-CMOS anisotropic etching ofsilicon microsensors: an experimental study

In the present study, the shape deterioration problem encountered in post-C MOS silicon anisotropic etching using Plasma Enhanced CVD (PECVD) silicon n itride masking layer has been investigated. Large shape deterioration was o bserved at every convex corner of silicon mesa structures formed with some kinds of PECVD-SiN masking layer. The cause of the problem has been clarifi ed through experiments. The fragile property of the masking material was an important factor on the resulting shape deterioration problem. It was foun d from the experimental results that compressive intrinsic stress or strong adhesion of masking material is necessary to obtain a desirable shape of m esa structures. In addition to PECVD-SiN masking layer, sputtered SiO2 laye r was also evaluated for its suitability as masking layer in post-CMOS micr omachining. It has been found that sputtered SiO2 masking layer performs we ll for post-CMOS anisotropic etching of silicon mesastructures/microsensors . (C) 2000 Published by Elsevier Science B.V.