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Study on mean stress and thickness effects on fatigue behavior of nanocrystalline Cu thin films
Recently, microelectronics related industry such as semiconductor and MEMS has grown rapidly. As the size of microsystem devices continues to decrease, the reliability and lifetime of device would be affected, with a corresponding need to understand how length scales affect mechanical behavior, accurate knowledge on the mechanical behaviors of thin-film materials has become important for the design of MEMS device.
Our study focuses on the fatigue property of copper thin-film, subjected to a periodic external force with a mean stress. The material subjected to a repeated cyclical stress, resulting in the damage of material is called fatigue. When the fatigue behavior occurs, there is no any significant change in appearance. When the mechanical properties of materials could be understood to estimate the fatigue cycles, the damages of components could be prevented.
The method of Experimental used an uniaxial micro-tensile system, with a feedback controlled loading for a mean stress, so that the copper thin-film under the same mean stress until it damage, and then repeated to give different mean stress, observe the fatigue cycle, and describe the S-N curve of copper thin-films. The experiment measured three thickness copper thin-films that include 300 nm, 500 nm and 700 nm to study the effects with different thickness.
As a result, the higher mean stress would lead to material fatigue occurs sooner. To compare with different thickness of copper thin films, the fatigue cycles would increase when the thin-film became thinker.
|Appears in Collections:||精密工程研究所|
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