Study of Lifetime Degradation in n-type Silicon Due to Oxidation of Boron-rich Layer

Various boron diffusion techniques are being investigated to fabricate n-type Si cells. Thermal oxidation is often used in photovoltaic to remove boron-rich layer (BRL) formed as a byproduct of boron diffusion because it interferes with surface passivation. However, oxidizing the BRL can cause a severe degradation in bulk lifetime. In this paper, high resolution electron microscopy (HREM) was performed to detect the presence of BRL after B diffusion and its removal after subsequent oxidation. In addition, bulk lifetime of n-type Si with BRL was measured after various oxidation conditions to systematically investigate the BRL-induced lifetime degradation mechanism in n-Si. The primary metal impurity responsible for the bulk lifetime degradation was concluded to be Fe in this study.