Evolution of One-Dimensional Gratings with High Aspect Ratios on Si(001) Surfaces by High-Temperature Annealing

We have investigated the structural evolution of one-dimensional (1D) gratings with high aspect ratios on Si(001) surfaces by high-temperature annealing. Gratings 2 µm in depth and having different pitches from 0.8 to 4.0 µm were annealed at 1100 °C under an ultrahigh vacuum condition. On the basis of observing the cross-sectional profiles of the gratings by scanning electron microscopy, the structural evolution and its dependence the grating period are characterized. The observed decay of the periodic surface structures, in which the wave heights are larger than 0.2–0.3 µm, is faster than the well-known exponential amplitude decay. We have also performed numerical simulation of the profile evolution of 1D gratings based on Mullins' theory, showing that surface self-diffusion is the predominant mass transport mechanism for the observed structural evolution.