Tensile Testing of Ultra-Thin-Film Materials Deposited on Polyimide for Mems Applications
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A newly developed approach to thin-film tensile testing has been utilized for evaluating ultra-thin-films of about 60-100 nm in thickness. Thin sputtered metal films deposited on 3.5 gm thick polyimide film substrates were tested using a Mesotronix nanotensiometer. Modifications to sample handling and zero strain calibration helped to improve testing reproducibility. The response of a thin-film metal was determined by subtracting the response of the polyimide carrier film from that of the metal-on-polyimide composite. Stress-strain curves for two amorphous alloys sputtered from Al-25 at% Ti and Nb-25 at% Al targets exhibited well-defined elastic regions followed by brittle behavior. The ultimate tensile strengths (UTS) were about 1200 MPa for the Al-Ti and 1700 MPa for the Nb-Al, both of which occurred near the elastic strain limit of about 2%. After recrystallization at 280°C for an hour, the Al-Ti film showed what appears to be an upper and lower yield point, in addition to strain hardening. Initial yielding occurred at a strain of about 1.2% and a stress of about 800 MPa, while the UTS of about 1000-1060 MPa occurs at strains as high as 9%. Stress relaxation measurements performed on both the amorphous and the recrystallized films showed lower values of stress relaxation at 1% strain compared to low alloy polycrystalline Al films.
[1] Paul S. Ho,et al. Thickness dependent mechanical behavior of submicron aluminum films , 1997 .
[2] Larry J. Hornbeck,et al. Digital Light Processing for high-brightness high-resolution applications , 1997, Electronic Imaging.
[3] P. Ho,et al. Film Thickness Effect on Tensile Properties and Microstructures of Submicron Aluminum Thin Films on Polyimide , 1996 .
[4] A. Cottrell,et al. Dislocations and plastic flow in crystals , 1953 .