Annihilation of photo-induced minority carrier caused by ion implantation and rapid thermal annealing

We report decreases in the minority carrier effective lifetime, τ_eff, of 700-μm-thick silicon substrates coated with 43-nm-thick thermally grown SiO₂ layers by Ge ion implantation with 1×10¹³ cm^-2 at 150 keV, and rapid thermal annealing, RTA, at 1100°C for 50 s. Ge ion implantation markedly decreased τ_eff to 1.6×10^-6 s when 635 nm light was illuminated to the implanted surface. It caused serious damage with a high surface recombination velocity, S, of 2×10⁴ cm/s and a low bulk lifetime of 5×10^ℒ6 s at the 200 μm deep surface region. Although RTA successfully recrystallized the Ge-implanted surface region, it made τ_eff low of 1.1×10^-6 in the cases of 635 nm light illumination. RTA probably caused substantial thermal stress associated with a high S of 3×10⁴ cm/s. 1.3×10⁶ Pa H₂O vapor heat treatment at 260°C for 3 h markedly increased τ_eff to 6.5×10^-4 s. Post low temperature annealing is effective to cure the recombination defect states caused by RTA.