Extended Design Space of Silicon-on-Nothing MEMS.

Complex monolithic Si MEMS can be created using a single mask by extending the empty-space-in-silicon (ESS) or silicon-on-nothing (SON) technology. The fabrication combines isotropic and anisotropic etching with selective removal of passivation layers followed by hydrogen annealing. The resulting expanded design space includes multilayer structures and embedded cavities. The MEMS formation by the hydrogen annealing is simulated both at large scales and microscopic scales that together predict the shape of the finished MEMS. We demonstrate the accuracy of our process and simulations by fabricating single- and double-layer evacuated silicon voids that form Fabry-Perot optical pressure sensors with the sealed voids as pressure references. We also create multi-layered sensors with an integrated photonic crystals sensing diaphragm for improved optical readout. The sensors have a calculated 6.7 $\mu \text{V}$ /Pa sensitivity and low noise over a dynamic range of over 70.9 kPa. [2019-0091] [ABSTRACT FROM AUTHOR]