Nickel surface micromachining

This paper describes a one-mask surface micromachining process in which nickel is used as a structural material and polysilicon as a sacrificial layer. High-aspect-ratio photolithography, up to 20 /spl mu/m thickness, is used for making a plating mold. Electroless plating on polysilicon is used for nickel deposition. 1 to 5 /spl mu/m thick polysilicon is deposited in a low-pressure chemical vapor deposition (LPCVD) process. A short pretreatment etch of polysilicon prior to electroless plating, causes the polysilicon surface to become porous, providing a suitable mechanical bonding site for excellent adhesion of nickel. KOH is used for etching the polysilicon sacrificial layer for releasing a nickel moving part. Using this process, electrostatic nickel microactuators ranging from 5 to 20 pm in thickness are fabricated.