A multiscale simulation model is developed for optimizing the parameters of SiO 2 plasma-enhanced atomic layer deposition of high-aspect-ratio hole patterns in three-dimensional (3D) stacked memory. This model takes into account the diffusion of a precursor in a reactor, that in holes, and the adsorption onto the wafer. It is found that the change in the aperture ratio of the holes on the wafer affects the concentration of the precursor near the top of the wafer surface, hence the deposition profile in the hole. The simulation results reproduced well the experimental results of the deposition thickness for the various hole aperture ratios. By this multiscale simulation, we can predict the deposition profile in a high-aspect-ratio hole pattern in 3D stacked memory. The atomic layer deposition parameters for conformal deposition such as precursor feeding time and partial pressure of precursor for wafers with various hole aperture ratios can be estimated.

Molecular beam epitaxy (MBE) regrowth of GaAs on periodically inverted GaAs(100) substrates using arsenic dimers (As2) was studied. We found that we can reduce corrugations on the regrown GaAs by MBE growth using As2 at considerably higher substrate temperatures (∼450 °C) than in the case of growth using arsenic tetramers (∼300 °C). This result indicates that As2 MBE regrowth can be used to fabricate highly efficient GaAs/AlGaAs wavelength conversion waveguiding devices owing to a reduction in the propagation losses caused by interface corrugations. We also estimated the diffusion lengths of Ga atoms coexisting with As2 on GaAs(100) surfaces from experimental thickness variations on the basis of a diffusion equation analysis.