Minority Carrier Annihilation in Lateral Direction Caused by Recombination Defects at Cut Edges and Bear Surfaces of Crystalline Silicon

Abstract

We report on the photo-induced minority carrier annihilation effect in the lateral direction caused by cut edges and partially formed bare surfaces for 500-µm-thick n-type silicon substrates coated with thermally grown SiO2 layers. A 9.35 GHz microwave transmittance measurement system with illumination with a 0.2-cm-wide 635-nm continuous wave light beam was used to measure spatial distribution of the minority carrier effective lifetime τeff. A mechanical cut decreased τeff in a 0.9-cm-wide region from the cut edges. τeff decreased from 3.4×10-3 (initial) to 6.5×10-4 s at cut edges. A simple model of carrier diffusion in the lateral direction with a carrier lifetime of 3.4×10-3 s and a recombination velocity of 500 cm/s at the cut edges well explained the experimental spatial change in τeff near the cut edges. A similar widely spatial decrease in τeff was also observed in the region coated with thermally grown SiO2 layers near the bare silicon surface formed by partial etching of SiO2.