Mechanical Characterization of Ni-Based Alloy Thin Film by SPM Tensile Testing

点击翻译按钮获取中文摘要

This research investigated mechanical characteristics of micro scale single crystal silicon (SCS) and UV-LIGA Nickel (Ni) films used for micro electromechanical systems (MEMS). Compact tensile tester operated in Scanning Probe Microscope (SPM) was developed for accurate evaluation of Young's modulus, tensile strain, and strength of microscale SCS and UV-LIGA Ni specimens. SCS specimens with nominal dimensions of 20 pm in thickness, 50 p.m in width, and 600 pm in length were prepared by a conventional photolithography and etching processes. UV-LIGA Ni specimens, with a thickness of 15 pm, a width of 50 pm, and a length of 600 p.m in nominal dimensions, were also fabricated by electroplating using a UV thick photoresist mold. All specimens have line patterns on their specimen gauge section to measure axial elongation under tensile stressing. The SCS specimens showed linear stress-strain relation and brittle fracture, whereas the UV-LIGA Ni specimens produced elastic-inelastic deformation … More behavior.Young's modulus of SCS and UV-LIGA Ni specimens obtained from tensile tests averaged 169.2 GPa and 183.6 GPa, respectively, which closed to those of the bulk materials. However, ultimate tensile strength of both materials showed larger value than that in bulk, 1.47 GPa for SCS and 0.98 GPa for Ni specimens. Yield stress and breaking elongation of UV-LIGA Ni specimens were also quite different from those of buLk Ni.Mechanical properties of the UV-LIGA Ni specimens were also studied at elevated temperatures to propose a simple constitutive equation on the assumption that the total strain increment was a linear superposition of elastic, plastic and creep strain increments. An optimum design of the micro connector by finite element analyses has been performed using the constitutive equations.Finally, magnetic domain pattern of permalloy thin films, which were know to be Ni-based alloy, was measured by magnetic force microscope (MEM) to reveal the effect of film thickness on the width of domain walls. Domain walls increased with a reduction of film thickness, which was caused by the transition of domain walls from Block type to Cross-tie type. Less