Novel Technology for Capacitive Pressure Sensors with Monocrystalline Silicon Membranes

We report on a novel surface micromachining technology for the fabrication of capacitive absolute pressure sensors. The pressure sensitive membrane is formed by single crystal silicon enabling excellent long term stability. The membrane formation is based on the Advanced Porous Silicon Membrane (APSM) process [1], which is currently applied to piezoresistive transducers. Expanding this technology to capacitive transduction allows for a greater flexibility in tailoring the sensor properties to specific applications [2]. This expansion is implemented by adding a poly-Si counter electrode layer on top of the membrane in a surface micromachining step. Since only front side processing on standard silicon substrates is used, this method is very cost-efficient and fully CMOS-compatible, enabling monolithic integration of circuitry.