A hysteresis-free platinum alloy flexure material for improved performance and reliability of MEMS devices

This work presents the use of a hard platinum alloy (Alloy 851) as a MEMS flexure material. Alloy 851 is the trade name for Pt alloyed with 15% Rh and 6% Ru. This alloy is an ideal spring material, as it combines many desirable properties such as biocompatibility, non-ferromagnetic, extreme corrosion resistance, good electrical and thermal conductivity, high Young´s modulus, high yield strength, and negligible hysteresis and fatigue. Alloy 851 can be exposed to fluorine and chlorine plasmas and wet chemical etches without damage and does not require protective masking, resulting in fewer fabrication steps. Control of stress as a function of deposition parameters, as well as thin-film material characteristics are discussed. The resultant flexures and their mechanical performance as supports for rotating mirror structures are described.