Multiscale modeling of defect formation during solid-phase epitaxy regrowth of silicon

Abstract

This work presents a multiscale approach to understanding the defect formation during the evolution of solid-phase epitaxy regrowth in Si. A molecular dynamics (MD) simulation technique has been used to elucidate the defect formation mechanisms, as well as to determine their nature. A hybrid lattice kinetic Monte Carlo (LKMC)-finite element method (FEM) model fed by the outcome of MD was subsequently implemented. It scales up the simulation times and sizes, while reproducing the important features of the defected regrowth predicted previously. FEM calculations provide the strain pattern due to the density variation between the amorphous and crystalline phases, which is then taken into account by the LKMC model by including the effect of the strain in the rates of recrystallization. Overall, this multiscale modeling provides a physical explanation of the generation of defects and its relation with the presence of strain. The model also captures the character of formed defects. It distinguishes two types: twins formed at {1 1 1} planes and dislocations produced by the collapse of the two recrystallization fronts. Simulation results are validated by comparing them with significant experiments reported in the literature.

Formation of multiple dislocations in Si solid-phase epitaxy regrowth process using stress memorization technique

“…Some models explain the a-Si SPER process growth fronts exhibit nano-facets [9] and form defects at the {1 1 1} interface with intrinsic and extrinsic stress. The intrinsic stress comes from the intrinsic a-Si/Si density difference and the volumetric expansion strain effect [10]. And the extrinsic stress comes from the capping high-stress film.…”

Improved physical models for advanced silicon device processing

“…Stresses can be externally generated or appear as a result of the 2% volume expansion of amorphous Si with respect to crystal Si [108]. CMD simulations have shown that the anisotropic regrowth of the amorphous phase in thin film layers results in twin defects [102,109,110], and that when significant strains are present, a slow-down in zones with high shear strain produces the evolution of ledges that collapse and evolve into Frank partial loops [111].…”

“…To overcome the limitations of non-lattice KMC models in a computationally efficient code, Martin-Bragado et al developed a lattice KMC model that reproduces different planar SPER velocities and the formation of defects during regrowth [94,[111][112][113]. Stress information can be extracted from finite-element methods [111] and fed back and forth to the lattice KMC code.…”

“…Regrowth kinetics is modeled as a sequence of atomic recrystallization events, whose frequency is determined by a unique activation energy but with three different pre-exponential factors, characterizing the growth rates of {100}, {110} and {111} orientations. Thus, the anisotropy on the regrowth rate for the three basic planar orientations during SPER is simulated as well as the formation of twins on {111} planes, the slowed recrystallization near corners as a consequence of the shear strain, and the formation of dislocations where two recrystallization fronts meet [94,111,114]. …”

“…Stress information can be extracted from finite-element methods [111] and fed back and forth to the lattice KMC code. The model is based on the assumption that each atom in the amorphous phase needs to form two undistorted bonds with the crystal to be incorporated to the crystalline phase [106].…”