Laser annealing of plasma-damaged silicon surface

Abstract

13.56MHz capacitance coupled Ar plasma irradiation at 50W for 120s caused serious damage at SiO2/Si interfaces for n-type 500-μm-thick silicon substrates. The 635-nm-light induced minority carrier effective lifetime (τeff) was decreased from 1.7×10−3 (initial) to 1.0×10−5s by Ar plasma irradiation. Moreover, the capacitance response at 1MHz alternative voltage as a function of the bias voltage (C–V) was changed to hysteresis characteristic associated with the density of charge injection type interface traps at the mid gap (Dit) at 9.1×1011cm−2eV−1. Subsequent 940-nm laser annealing at 3.7×104W/cm2 for 4.0×10−3s markedly increased τeff to 1.7×10−3s and decreased Dit to 2.1×1010cm−2eV−1. The hysteresis phenomenon was reduced in C–V characteristics. Laser annealing effectively decreased the density of plasma induced carrier recombination and trap states. However, laser annealing with a high power intensity of 4.0×104W/cm2 seriously caused a thermal damage associated with a low τeff and a high Dit with no hysteresis characteristic.