MICROMOTOR FABRICATION

This paper presents a detailed discussion of micromotor fabrication and related critical issues. The micromotors under study are of the variable-capacitance side-drive type with salient-pole and wobble (harmonic) designs. Polysilicon surface micromachining forms the basis of the micromotor fabrication process. In this process, LPCVD heavily phosphorus-doped polysilicon is used for the structural parts, LPCVD silicon nitride is used for electrical isolation, and CVD low-temperature oxide is used as the sacrificial material. The fabrication process impacts the performance characteristics of the micromotor through the reproduction accuracy of the design geometry and through the modification of the characteristics of contacting surfaces. Pattern definition and delineation are among the most critical steps of the micromotor fabrication process because of the increasing surface topography during fabrication and the large film thicknesses utilized. The release and testing process can affect the frictional characteristics of the micromotor significantly, determining success or failure of operation by dielectric excitation.