3-dimensional scalable pressure sensors: device and process design

Abstract

We present the design, process flow and packaging scheme for a novel 3D capacitive MEMS pressure sensor. These sensors present a paradigm shift in pressure sensor technology. They contain an array of vertical diaphragms perpendicular to the wafer plane where each pair of diaphragms requires orders of magnitude lower footprint than traditional in-plane sensors. The sensor can be arrayed or scaled up for increased sensitivity and can be absolute, gauge or differential. Fabrication requires 2-4 masks depending on process flow and has been greatly simplified, without reduction in performance, for high yield and low cost. Multiple geometries have been modeled with sensitivities reaching several fF/kPa and temperature characteristics better than conventional devices. Pressure and electrical ports are individually interchangeable between front and back sides. This allows for a simple design that has only Si facing the sensing environment and the electrical connections on the backside.