Atomistic Simulation of Arsenic Ion Implantation and Diffusion in Silicon

[[abstract]]Ion implantation is the key processing step in the production of integrated circuits. However, an unavoidable consequence of energetic ion bombardment is the displacement of lattice atoms, resulting in extensive damage to the silicon crystal structure. Hence understanding of ion implantation induced damage is crucial as it affects device performance.The major drawback of the ion implantation is that during implantation the crystalline lattice of the semiconductor is damaged and an annealing step is necessary to repair the damage as well as to activate the dopant. The major damages during this process are the extended defects which not only enhance the diffusion process but also have adverse effect on the device performance. Since defects are unstable as the crystal approaches the thermal equilibrium, annealing can be used to reduce the kinetic limitation on the defects and for dopant activation. Significant portion of the dopant can be electrically activated upon annealing at a relatively low temperature (550 oC). However annealing at temperature 900 oC or higher is necessary to eliminate the secondary defects which form when the primary defects are annealed.The continuum approach to modeling dopant diffusion is widely used in process simulation, but this method cannot include the evolution of the defects into the simulation. Hence a more atomistic simulation tool is necessary to study the evolution of defects during implantation and diffusion. The premiere tool in this class of atomistic simulation methods is molecular dynamics, since it as a serious limitation termed as “time-scale problem” discussed later, it cannot be used for this purpose. This leaves us to the option “Kinetic Monte Carlo” which acts as a perfect bridge between the continuum and the molecular dynamics approach, making it the perfect simulation tool to study the ion implantation and diffusion for real device dimensions and annealing time.The work described in this thesis study the behavior of defect generation, damage kinetics and amorphization during ion implantation, and recrystallization, damage evolution and dopant redistribution effects during ion implantation and annealing. Various ion implantation and annealing studies have been carried out to investigate the regrowth behavior of the damaged silicon and the evolution of the extended defects. The good agreement between simulation results and various experimental data shows that the simulations are predictive and can provide valuable insights for process optimization