Novel fabrication of comb actuator using reactive ion etching of polysilicon and (110) Si anisotropic bulk etching in KOH

A bulk-micromachined interdigitated comb actuator suspended by surface-micr omachined polysilicon springs is proposed and fabricated for excitation of resonating motion. The excitation force electrically generated by the inter digitated (110) Si comb pair of 420 mu m height is more effective than that obtained using a comb pair with 3-5 mu m height fabricated by polysilicon micromachining. The interdigitated comb finger array, whose geometry is 420 mu m high, 20 mu m wide and 5 mu m from the neighboring interdigitated com b finger, is fabricated by anisotropic bulk etching of 420-mu m-thick (110) Si in KOH. A 5-mu m-thick phosphorous-doped low pressure chemical vapor de position (LPCVD) polysilicon film is used for the. fabrication of flexures of the actuator, using reactive ion etching. The double-sided aligned Fabri cation technique accomplishes not only polysilicon flexure formation on bot h sides of the actuator but also the removal of two slant (111) planes in c oncave corners of the (110) Si structure, which have limited the interdigit ated comb actuator design on (110) Si.