Sensitivity analysis of plating conditions on mechanical properties of thin film for MEMS applications |
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Authors: | Yoonhwan Woo and Sang-Hyun Kim |
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Affiliation: | (1) Institute of Precision Engineering, National Chung Hsing University, Taichung, 402, Taiwan; |
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Abstract: | In this paper, we report the detailed investigation into the effects of plating temperature and applied current density upon
the mechanical properties of plated nickel film such as Young’s modulus and residual stresses. This method uses the resonance
method of atomic force microscope, which does not require specially microfabricated cantilevers and additional experimental
set-up. Thin layers of nickel are electroplated onto the tip surface of AFM cantilevers and plating thicknesses were measured
at the end of each plating step. The self-deformation of the released AFM cantilever is also measured as a function of the
plated nickel thickness, which is converted into the quantitative residual stress by appropriate mechanics. The measured Young’s
modulus is as high as that of bulk nickel at low plating temperature and at low applied current density, but drastically drops
at high temperature or current density. The dependence of Young’s modulus on the plating thickness is negligible in thin film
less than few microns. The residual stress is also a strong function of the process conditions, and decreased with the elevation
of the current density and plating temperature. And the intrinsic and extrinsic stresses of plated nickel are separated from
the measured residual stress, and correlated with plating conditions. Dependence of the plated thickness on Young’s modulus
and residual stress is also considered. |
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Keywords: | |
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