Hydrogen diffusion and passivation processes inp- andn-type crystalline silicon

Several deuteration experiments on crystalline silicon have been performed for various shallow dopant impurities (B and Al for p-type silicon; P and As for n-type silicon) and for different temperatures and times of plasma exposure. Deuterium diffusion depth profiles obtained by secondary-ion mass spectroscopy (SIMS) were simulated with an improved version of a previously reported model. A careful analysis of the SIMS data has allowed the reduction of the number of fit parameters, by excluding the ${\mathrm{H}}_2$-molecule formation and by a rough estimate of the neutral-deuterium diffusion coefficient and of the surface concentration of neutral deuterium. The diffusion coefficients and related activation energies of the hydrogen species ${\mathrm{H}}^0$, ${\mathrm{H}}^{\mathrm{-}}$, and ${\mathrm{H}}^{+}$ were determined, leading to a stated ranking of the mobilities in the order ${\mathrm{H}}^0$<${\mathrm{H}}^{\mathrm{-}}$<${\mathrm{H}}^{+}$. The dissociation energies of BH, AlH, and PH complexes were also calculated and have allowed us to deduce the corresponding bonding energies of the complexes, which suggest a scaling of the complex stability in the order PH<BH<AlH. Free-carrier depth profiles obtained by high-frequency capacitance-voltage measurements, combined with chemical etching, provided direct evidence of the rate of passivation of the shallow p-type-dopant impurities. The comparison between both couples of depth profiles (deuterium diffusion and carrier concentrations), in the case of p-type silicon, showed good agreement between the deactivation process of dopants and the corresponding depth penetration of deuterium.