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

This paper reports the design, integration, modelling and characterization of single crystalline (c-Si) resistors on a 3.6 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathrm{\mu }$</tex-math></inline-formula>m-thick and 2.7 mm-diameter polyimide MEMS membrane. We propose a straightforward <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">top-down</i> fabrication scheme to integrate any microfabricated devices onto a flexible membrane. A <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">bulge-test</i> 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.