Visualizing Dynamic Etching in MEMS VR-CAD Tool

Abstract

In this paper we introduce our virtual etching as part of MAGDA a CAD system for Micro Electro Mechanical Systems (MEMS). Virtual prototyping visualizations require fast algorithms for visualization that are suitable for interactive design. Modern MEMS simulators do not offer dynamic visualizations for etching. Etching progress is time dependent, typically calculated with Finite Element Analysis, which has too slow a calculation time, hence is not suitable for interactive design. Etching progress is important in MEMS with small dimensions, where Silicon technology must be used, with its repeated cycles of deposition and lithography/etching until the desired structure is formed. While etching performance is well known from the Integrated Circuit processing, it is not so predictable in MEMS because the shapes are more complex. Underetching is not desired in IC technology, but it is crucial in shaping MEMS structures. We use a Marker/String method for the progressive mesh as a faster method suitable for interactive design. The method is not known much for etching; but used in other applications. We have found a way of overcoming swallowtail conditions that appear on corners. We are also able to simulate underetching. In this paper we demonstrate the progress of etching using a circular lithography mask calculated in 2D then rotated, and a square mask calculated in 3D. In both cases we are able to simulate underetching. The method can be extended into larger material removal CAD visualizations. In this way we made a step towards filling a long existing need in virtual prototyping.