A vertical convex corner compensation and non {111} crystal planes protection for wet anisotropic bulk micromachining process

Abstract

In general, convex corner structures and non {111} crystal planes will be undercut during wet anisotropic etching. These characteristics have been extensively exploited to fabricate freely suspended thin film structures. On the other hand, these effects have to be reduced or prevented in various applications. This study has successfully demonstrated a novel process to exploit the characteristics of DRIE to assist wet anisotropic etching. To this end, protecting structures including vertical posts and vertical walls were employed to protect convex corners and non {111} crystal planes from undercutting. In applications, the experimental results show that mesas and cavities with arbitrary shapes can be fabricated using wet anisotropic etching. Moreover, these mesas and cavities can further integrate with suspended thin film structures and the structure formed by the inclined {111} crystal planes. Hence, the variety of bulk micromachined MEMS devices will significantly increase.