Depth and profile control in plasma etched MEMS structures

We have achieved uniform etched depth regardless of feature size by employing a combination of anisotropic plasma etching in inductively coupled plasma (ICP) followed by wet etching. In our approach, the original feature is divided into small elementary features in a mosaic-like pattern. These individual small features are all the same size and thus exhibit identical etch rates and sidewall profiles. Final patterns are completed by wet etching: the ridges between the elementary features are removed in TMAH. In this paper, we present the results obtained using this dry/wet etching sequence. The benefits and limitations of this method are described. Extensions to more complex multidepth structures are discussed.