Nickel-filled Hexsil Thermally Actuated Tweezers

Abstract

We report the first demonstration of a molded micromachine consisting of a high adpect-ratio CVD polysilicon shell filled with electroless nickel for the conductive regions, in situ P-doped polysilicon for the resistive regions, and undoped polysilicon for the insulating regions of the machine. One mask defines all regions simultaneously on the basis of mold trench width. Electroless Ni enables high current-canying capacity with minimal power dissipation. Electroless plating proceeds conformally over the entire polysilicon surface so that a deep trench can be filled by deposits growing from the sidewalls toward the middle of the trench, a distance of only a few pm. In these first prototypes, tip displacement of 25 pm was observed with a current of 300 mA at 3 V. Wire actuated, normally closed, and normally open, tweezers with 200 pm tip motion are also demonstrated.