Two-dimensional simulation of pattern-dependent oxidation of silicon nanostructures on silicon-on-insulator substrates

摘要

Pattern-dependent oxidation (PADOX) of silicon nanostructures fabricated on silicon-on-insulator (SOI) substrates is simulated. In order to reproduce the characteristic features of PADOX in the simulation, the volume expansion due to silicon oxidation is treated as a dilational strain, and the strain is applied to a transition region in which silicon is converted to oxide. In addition, the silicon oxide and transition layer are treated as viscoelastic solids, and the stress dependencies of the oxidation reaction, oxygen self-diffusion in the oxide, and oxide viscosity are taken into account. The simulated silicon and oxide shapes after oxidation satisfactorily reproduce the experimental results. The simulation results suggest that the rounded silicon shapes that appear after oxidation are mainly caused by the stress-induced reduction of oxide viscosity. Moreover, we obtain oxidation-induced strain and stress from the simulation. Based on the strain obtained, the electron potential profile responsible for the operation of single-electron transistor (SET) is investigated. The compressive strain in the silicon wire region of SETs reduces the bandgap, and this reduction is critical for the formation of the potential profile responsible for SET operation.