COMB DRIVE ASSEMBLY HAVING COMB DRIVE FINGERS WITH VARYING CROSS-SECTIONS AND METHODS OF MAKING SAME

摘要

A MEMS comb drive assembly and associated methods of fabrication are provide that are capable of gap variance between adjacent interdigitated comb drive fingers during comb drive operation. Gap variance allows for an increase in motive force by increasing the average capacitance variation of the comb structure as the distance between the comb fingers varies. The comb drive assembly includes first and second comb drive members that each comprise a series of comb drive fingers. The comb drive fingers will characteristically have cross-sections that vary in area along any lengthwise position of the comb drive finger. This variance in cross-sectional area provides for a gap differential between adjacent interdigitated comb drive fingers when the comb drive assembly is operational. As the gap varies during comb drive operation, the average variance in capacitance between opposing comb drive fingers increase, thereby increasing the motive force capabilities of the comb drive assembly. In one embodiment of the invention, the comb drive fingers are configured as wedge shaped structures in a plan view; moreover the comb drive fingers are frusto wedge shaped structures in a plan view. The wedge shaped configuration allows for the comb drive fingers of opposing comb drive members to be interdigitated such that the gap between adjacent comb fingers varies as the fingers are placed into motion. The frusto wedge shaped embodiment allows for the end of the body of the comb finger furthest from the base of the comb drive member to be truncated, so that ends of the comb drive fingers do not repeatedly contact the base of the opposing comb drive member during normal operation. In a further embodiment of the invention the comb drive assembly is a rotary comb drive assembly capable of imparting rotary motion to a torsional resonance plate. The invention further provides for methods of fabricating comb drive fingers.