Prediction of low-energy boron doping profile for ultrashallow junction formation by hybrid molecular dynamics method

Our original hybrid method combining tight-binding quantum chemical and classical molecular dynamics was first applied to the low-energy doping process of boron into a silicon substrate, which has a depth of more than 10nm that is needed to evaluate an ultrashallow junction position. Tightbinding quantum chemical molecular dynamics calculation was used for an injected boron atom and surrounding silicon atoms within a sphere with a radius of 0.5nm centered at the boron atom. This method is advantageous in treating the many-body collision effect and electron-electron interaction, which are more important in low-energy doping, compared with the Monte Carlo method with binary collision approximation. A comparison with a plasma doping experiment was also carried out. The junction positions were 6.2nm for boron doping at an initial kinetic energy of 200 eV in the simulation results and 6.4nm for 200 eV in the experimental results. Good agreement between simulation and experimental results indicates that our hybrid molecular dynamics method is applicable to doping profile prediction in a silicon structure with a depth of more than 10nm that is needed to evaluate ultrashallow junction formation.