POLYSILICON INTEGRATED MICROSYSTEMS - TECHNOLOGIES AND APPLICATIONS

Co-fabrication of polysilicon microstructures with CMOS electronics en ables monolithic inertial. sensors to be fabricated. Correlations are well established between the deposition, doping, and annealing conditi ons of LPCVD polysilicon and its mechanical properties, such as residu al Strain, strain gradient, and Young's modulus. Surface passivations for alleviating stiction have been demonstrated recently that greatly reduce the tendency for polysilicon microstructures to adhere to adjac ent surfaces when dried after release by wet etching and rinsing, or w hen brought into contact due to mechanical shock during use. Sigma-del ta control strategies are attractive for linearizing closed-loop senso rs and are well suited to implementation in CMOS. Basic design princip les for sense elements and electromechanical actuation in a single str uctural layer of polysilicon have emerged rapidly in the past several years. Monolithic polysilicon integrated sensors for the X, Y, and Z c omponents of linear acceleration, angular rate, and angular accelerati on have been demonstrated using the BiMEMS process of Analog Devices, Inc. Mechanical suspensions, electrostatic actuators and capacitive pi ckoffs, and interface- and control-circuit building blocks are all por table to alternative integrated technologies that share the basic char acteristic of thin, laminar suspended microstructures.