The removal of metal impurities from the surface of Czochralski wafers using a porous silicon-based gettering under a gas flow HCl/O2 dry

Abstract

In this paper, the gettering of Czochralski silicon (CZ) with a porous silicon layer (PSL) oxidized in the presence of hydrochloric acid (HCl) gas was well discussed. The porous silicon damage reduces the activity of the contaminants in silicon and seems to be more effective when used in combination with HCl treatments. This process combined both mechanical and chemical parts to enhance the impurity removal. The getter was evaluated by means of the Hall Effect device to measure the carrier mobility. An enhancement of a minority carrier lifetime was evaluated by the QSSPC technique. The C–V characteristics indicated a decrease of the bulk dopants concentration. In the dark I–V characteristics, we observed a reduction of the leakage current density (JL) which goes back to the important decrease of the majority carriers. However, this new process can getter unwanted impurities deep-levels and enhanced the photovoltaic properties of solar cells.