Development of thermally-stable structures of thin SOI active layers

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In this work, thermal agglomeration phenomenon was studied for thin silicon-on insulator (SOI) layers in order to realize thermally-stable structures of SOI-MOSFETs.As the fundamental properties of the agglomeration phenomenon, the followings were typically found; (1) For (001) SOI layers, self-assembled Si islands aligned in the <310> directions are formed on the square region of the exposed SiO_2 layer, whose sides are almost parallel to the <110> directions. (2) Each of the islands is single-crystalline and surrounded by the facet planes. (3) Decreasing the SOI thickness, the islanding occurs at the lower temperature and smaller islands are formed with a higher density.According to the one-dimensional computer simulation, the ordered alignment of the islands is explained by the mechanism that the diffusion of surface Si atoms is enhanced due to the generation of the explained by the mechanism that the diffusion of surface Si atoms is enhanced due to the generation of the local distribution of surface chemical potential, or the sum of the strain and surface energies. Two-dimensional analysis is necessary for the entire understanding.Effect of the patterning the SOI layer was also studied. The patterning of the SOI layer causes the reduction of the onset temperature for the islanding, since the islanding preferentially occurs at the pattern edges. However, the islanding seems to be restrained for submicron-scale patterns, according to the preliminary experiment. Further studies on the patterning might lead to the thermally-stable SOI structures.