應力下因表面能及彈性能變化造成孔洞變形之研究
Date Issued
2005-07-31
Date
2005-07-31
Author(s)
DOI
932212E002069
Abstract
Semi-condoctor industry has entered sub-micron age with the progress of ULSIC’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 currents and thermal stress at high temperature, energy variation
will bring about atomic diffusion inside aluminum interconnects. In the meanwhile, if there is a void, which
could be an original defect or nucleates owing to atomic diffusion and keeps drifting and enlarging, inside the
aluminum interconnect, pore shape change and then crack tips will be forming 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 the references, we propose the hypothesis that interconnects are made of elastic materials 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 achieve the state of equilibrium in the form of ellipse. Otherwise, pore shape change will not
achieve the state of equilibrium but cause crack tips instead.
We will apply the Conformal Mapping Method to describe pore shapes by using power series. And how the
corresponding coefficients of power series vary will indicate the process of dynamic evolution of pores. Besides,
the distribution of elastic field and displacement field around the pore can be acquired by Complex Variable
Method.
We will substitute governing equation for Galerkin Approximation Method to acquire the threshold value of
stress of a pore in a state of a stable shape, and observe how these values relate to lifetime of interconnects.
Furthermore, the time it takes to nucleate crack tips, the size of crack tips, the stress concentration factors of
crack tips, and anisotropy of materials and stress will be discussed later.
Publisher
臺北市：國立臺灣大學應用力學研究所
Type
report
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