| Summary: | 碩士 === 國立臺灣大學 === 應用力學研究所 === 91 === Semi-conductor industry has entered sub-micro age with the progress of ULSI’s technology. Since aluminum interconnects are widely applied to semi-conductor devices, its reliability has great influence on lifetime of product devices.
From the past references and experiments, we found that as devices with aluminum interconnects are affected by the interaction of intense electric current and thermal stress at high temperature, energy variation will bring about atomic diffusion inside aluminum interconnects. In the meanwhile, if there is a defect inside the aluminum interconnect, pore shape change and then crack tips will be formimg due to atomic diffusion on the surface of the void. As soon as stress of crack tips exceeds the threshold, aluminum interconnects will be broken and even cut off as a result of fast fracture of crack tips, which will form open failure and defunction devices.
According to Surface Diffusion Model from Wang[4], we modify correlation of chemical potential from Wu[28] and propose the hypothesis that interconnects are made of linear elastic material and diffusion only take places on atoms distributing on the surface of voids. And we found that surface energy and elastic energy will vary during the process of pore shape change. If surface energy variation dominates, pore shape change will reach equilibrium, but if elastic energy variation dominates, pore shape change will not reach equilibrium.
We apply the Conformal Mapping Method to describe pore shapes by using analytical series. And hoe the corresponding coefficients of power series vary will indicate the process of dynamic evolution of pore shape. Beside, the stress field and displacement field around the pore can be acquired by Complex Variable Method in elasticity.
We substitute governing equation for Galerkin Approximation Method to calculate the process of dynamic evolution of pore shape, and observe how these values of energy variation relate to the geometry of pore shape. Furthermore, the stress concentration factors distribution on the pore surface will also de discussed.
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