Design, Fabrication, Modeling and Characterization of a Polyimide-Based Membrane for High Strain Studies in Microfabricated Devices

Abstract

This paper reports the design, integration, modeling and characterization of single crystalline (c-Si) resistors on a 3.6 μm-thick and 2.7 mm-diameter polyimide MEMS membrane. We propose a straightforward top-down fabrication scheme to integrate any microfabricated devices onto a flexible membrane. A bulge-test setup is assembled to measure the deflection of the membrane under a white light interferometer. In addition, a finite elements method (FEM) model is introduced to predict the behavior of the membrane under increasing pressure up to 80 kPa. The parameters of the FEM simulation are tuned with the deflection results to extract the strain tensor, showing a maximal biaxial strain of 0.37% at 80 kPa in the 300 nm-thick c-Si devices. Raman spectroscopy is finally employed to confirm the FEM results by comparing the estimated Raman peak-shift with actual Raman measurements. The shift predicted using phonon-deformation potential (PDP) theory shows excellent agreement with the experimental validation, giving confidence in the FEM model.