Papers by Keyword: ISDG

Abstract: A micro-scale uniaxial tension test method for measuring material mechanical properties of thin film materials is introduced in this paper. A self-developed test device is established based on the CMT8202 tension test machine. The Interference Strain/Displacement Gauge (ISDG) method is used to measure the strain in the micro-samples. The three dimensional finite element method (FEM) is utilized to optimize specimen geometry configuration and to reduce the stress concentration in specimen around grip region. The experiments are carried out for the polycrystalline copper thin film. The results show that stress-strain curves and the Young’s modulus of the thin film material can be obtained by micro-scale tension test. The Young’s modulus determined by micro-sample for polycrystalline copper thin film has a good agreement with published results.

Abstract: The accurate characterization of linear coefficient of thermal expansion (CTE) of thin films is vital for predicting the thermal stress, which often results in warpage and failure of a MEMS structure. In this paper, special emphasis is placed on the development of novel test method to extend an ISDG (Interferometric Strain/Displacement Gage) technique to the direct and accurate CTE measurement of MEMS materials, AlN and Au. The freestanding AlN and Au films are 1 μm thick and 5 mm wide. Strain is directly measured by a brand-new digital type ISDG with two Cr lines deposited on the specimen while heating a specimen in a furnace. The whole test system is verified first by measuring the CTE for the NIST’s SRM (Standard Reference Material) 736 (Cu) block. The measured CTE is 17.3 με/oC up to 167 oC, which agrees well with the NIST’s certified value. The CTE of Au is 25.4 ± 1.15 με/oC and that of AlN film is 3.77 ± 0.12 με/oC. The in-plane displacement resolution is about 5 nm at the best circumstances.