Doping of silicon with phosphorus end-terminated polymers: source characterization and dopant diffusion in SiO2

A polystyrene homopolymer with narrow molecular weight distribution (Mn = 2.3 ? 0.3 kg mol-1, ? = 1.05 ? 0.01) and end-terminated with a phosphorus containing moiety has been used to form P ?-layers embedded into a SiO2 matrix. The number of P atoms in the ?-layers has been stepwise increased from ~5 ? 1013 to ~1.6 ? 1014 atoms per cm2 by repeated doping cycles. The P ?-layers have been tested as diffusion sources at temperatures ranging from 1000 to 1200 ?C for different annealing times, up to 120 s. Variations of the diffusion coefficients with the annealing time have been observed and a clear dependence of diffusion coefficients on the P concentration has been highlighted. These results suggest the presence of two different P species diffusing through the SiO2 matrix; an initially fast diffusing P compound and a slow diffusing P atom incorporated into the oxide in a bound form. Collected data provide information about P diffusion in SiO2 that is fundamental to the development of predictive models for nanoscale doping processes based on the use of diffusion dopant sources generated by self-limiting reactions of dopant containing molecules onto deglazed or non-deglazed semiconductor substrates.