Validation of a CMOS-MEMS accelerometer based on FGMOS transduction by electromechanical modification of its coupling coefficient

This paper presents the design and fabrication of an accelerometer prototype through a CMOS silicon foundry with a technology able to deliver a floating-gate MOS transistor (FGMOS). The design of this device included a comb drive capacitor, with aluminum as the structural layer, in order to transform the FGMOS in an inertial sensor and its performance was evaluated electromechanically modifying the coupling coefficient of this FGMOS. A post-process micromachining step was added after the IC chip was received from the foundry. The case here described consists on a surface micromachining step such that the structural layer—aluminum in the case here reported—can be completely released making available a variable coupling capacitor (with air as dielectric) having free movement from which a variable coupling coefficient can be established. The results of a dynamic analysis applied to the resulting CMOS-MEMS structure are shown, demonstrating that this approach is interesting and promisorious as an option for inertial sensors.