Effects of damages induced by indium-tin-oxide reactive plasma deposition on minority carrier lifetime in silicon crystal

A reactive-plasma deposition (RPD) process damage is evaluated for an indium-tin-oxide (ITO)/SiO2/Si structure in terms of the recombination properties at the interface. To calculate the surface recombination velocity (SRV), the defect density at the SiO2/Si interface (Dit), the effective total charge (Qtot) which is the sum of the charges in the SiO2 and the trapped charge at the SiO2/Si interface, and the workfunction of ITO at the ITO/SiO2 interface (ϕITO), are extracted by capacitance-voltage (C-V) analysis as a function of a postdeposition annealing (PDA) temperature. The Dit and Qtot significantly increase by the RPD process to 1.4×1012 cm-2eV-1 and 1.5×1012/q cm-2, respectively, and decrease by the PDA at 200 °C in N2 ambient to 1.4×1011 cm-2eV-1 and 1.1×1011/q cm-2, respectively. The ϕITO also varies from 4.80 eV to 4.35 eV by the PDA. The correlation is examined between the SRV values calculated based on the extended SRH model using the extracted Dit, Qtot, and ϕITO values [SRV(CV)], and the SRV ones obtained from the minority carrier lifetime measurements [SRV(LT)]. It is found that multiple sets of capture cross-sections were required for SRV(CV) values to coincide with SRV(LT) ones. The effect of variation in the Qtot and ϕITO on the band bending is almost canceled out in the present PDA condition. It is thus considered that the increase in Dit is the main cause to decrease the minority carrier lifetime.