Power MEMS Materials and Structures

Abstract

The favorable scaling of the strength of brittle materials at small scales has the potential to enable a new class of devices: power MEMS. In this paper the effect of scale on the structural design of such devices is discussed with particular reference to the MIT microengine project. The initial goal of this project is to produce a turbine generator by deep reactive ion etching single crystal silicon. The design and fabrication of such a device offers significant challenges and opportunities. The major structural challenges arise from the very high stress levels (~ 1 GPa) required to achieve acceptable turbomachinery performance and the associated need to measure accurately the material properties. The task is further complicated by the need to achieve a good structural design within the constraints imposed by microfabrication processes. The major opportunities arise from the use of silicon at very small lengthscales. In particular, the use of microfabrication techniques offers the potential to control the processing-induced flaw size such that very high strengths can be obtained.