Micromechanical testing of MEMS materials

This paper discusses tensile testing techniques and results derived as part of a broader microstructure-properties investigation of structural materials used in surface micromachined (SMM), and LIGA MEMS technologies. SMM techniques produce devices on the surface of a silicon wafer, with critical dimensions as small as 1-2 mum, using a subtractive multilayer film deposition process. Two structural materials have been investigated: SUMMiT(TM) polysilicon and amorphous Diamond (a-D). Mechanical properties presented in this paper on these SMM structural materials were obtained from a direct tensile testing method using the lateral force measurement capability of a nanoindentation system. LIGA, a German acronym extracted from the words "Lithographie, Galvanoformung, Abformung," is an additive process in which structural material is electrodeposited into a polymethyl-methacrylate ( PMMA) molds realized by deep x-ray lithography. LIGA tensile specimens of several different materials have been evaluated using a mini-servohydraulic load frame, designed to test specimens of sizes similar to structural components. In this paper, tensile test results from LIGA fabricated Ni and Ni-alloys and examples of their correlation to processing and microstructure will be presented. (C) 2003 Kluwer Academic Publishers.