INFLUENCE OF THE ALKALI SURFACE TREATMENTS ON THE INTERFACE-STATES DENSITY AND MINORITY CARRIER LIFETIME IN Cz–SILICON WAFER

Abstract

The chemical etching of the surface of silicon wafers is a critical step in the manufacturing process of all semiconductor devices. In this contribution, we investigate the effect of alkaline etching on minority carrier lifetime and interface-states density ([Formula: see text] of silicon wafers intended to be used as solar cell substrates. After alkali treatment, the surface morphology was analyzed using scanning electron microscopy (SEM) and UV-visible-NIR optical spectroscopy. Besides and as electrical characterizations, the minority charge carrier lifetime ([Formula: see text] was measured by the Quasi-Steady State Photoconductance technique (QSSPC), and the Electrochemical Impedance Spectroscopy was used to evaluate [Formula: see text]. These results were correlated with the surface recombination velocity (SRV) calculated by fitting the experimental data to the theory. The results of characterization showed a lower SRV and a higher apparent lifetime ([Formula: see text] obtained with 23[Formula: see text]wt.% KOH etching as compared to those obtained with 30[Formula: see text]wt.% NaOH; viz. 825[Formula: see text]cm[Formula: see text] against 1500[Formula: see text]cm.s[Formula: see text] and 32[Formula: see text][Formula: see text]s against 23[Formula: see text][Formula: see text]s, respectively. These findings were corroborated by [Formula: see text] measurements which gave [Formula: see text][Formula: see text]ev[Formula: see text]cm[Formula: see text] for KOH treatment and [Formula: see text][Formula: see text]ev[Formula: see text]cm[Formula: see text] for NaOH treatment.