Novel process for a monolithic integrated accelerometer

A monolithic sensor, fabricated using a technology that combines surface micromachining with a BiCMOS process, is described. The capacitive sensing element consists of a 10 mu m thick layer of polysilicon that is deposited in an early stage of the IC fabrication sequence. A high degree of synergy is achieved and conflicting issues regarding the merging of the processes are avoided by using IC processing steps for manufacturing of the sensor element. Adhesion between parts of the sensor structure, during their release, is eliminated by using an HF vapor phase etching process for the sacrificial layer. The completed sensor has been characterized successfully.