Time evolution of phosphorus dose loss due to interface segregation

Different thermal processes and substrates were used to investigate the time evolution of phosphorus loss due to segregation at the Si-SiO₂ interface. Dose recovery occurred as phosphorus diffused into bulk silicon during furnace annealing. Dose loss increased when samples were cycled between silicon implantation and rapid thermal annealing (RTA). This implies that transient enhanced diffusion promotes dose loss during postimplantation RTA. Dose loss in silicon-on-insulator (SOI) substrates was characterized by using sheet resistance. The correlation between sheet resistance and dose loss was verified based on the experimental data of bulk silicon samples. Simulation results indicate that the equilibrium segregation behavior in SOI substrates is similar to that in bulk silicon substrates. The buried oxide layer in SOI substrates prevents phosphorus diffusion and increases interface area. Consequently, dose recovery in SOI substrates is not evident. The dose loss in SOI substrates is more significant than that in bulk silicon substrates.