Analysis of oxidized film formation and evaluation of intrinsic stress in the a-Si layer of semiconductor microscopic patterned structures using molecular dynamics method

Abstract

The intrinsic stress at hetero interface is one of key factors to induce the structural instability of micropatterning in semiconductor devices, and it is essential to quantitatively predict the intrinsic stress in terms of atomic structure. In our previous study, we established the method to predict the lateral undulation buckling of micropattern using continuum buckling theory and finite element method. However, there is a possibility that several-nanometer surface oxidized layer, which is formed during oxygen plasma etching process, involves the intrinsic stress of the order of 1 GPa and affects the buckling criteria. Since the experimental measurement of the stress of such a nano-scale layer is beyond the present technology, an atomistic simulation could be a tool to discuss the possibility. In this study, we make a molecular dynamics model for the plasma etching and predict the intrinsic stress of the oxidized layer on the surface of amorphous silicon (a-Si). Our approach reveals that the layer thickness depends on the incident energy of oxygen and that the intrinsic stress exceeds 1 GPa. Therefore, we conclude that it would be possible for the oxidized a-Si film to trigger the buckling of micropatterning even if the initial a-Si structure involves no stress.