Parameters influencing the flatness and stability of capacitive pressure sensors fabricated with wafer bonding

In this work we present detailed optical and electrical characterization re sults on silicon capacitive pressure sensing elements. The device fabricati on technology is based on the wafer bonding technique. Using the micro-Rama n technique, we investigate the influence of specific process steps as well as of the wafer bonding conditions-performed either in air or in nitrogen ambient-on the flatness and stress distribution of the pressure sensing dia phragms. Emphasis is also given on drift as well as on fatigue measurements since these effects determine the reliability of the devices. (C) 1999 Els evier Science S.A. All rights reserved.