Surface structure of mono-crystalline silicon wafers produced by diamond wire sawing and by standard slurry sawing before and after etching in alkaline solutions

Abstract

Fixed abrasive sawing (FAS) using diamond coated steel wires is an interesting alternative for commercial production of silicon wafers, as it has potential for increasing productivity and reducing consumables costs. The objective of this study has been to understand the differences in surface structure of Cz mono-crystalline silicon wafers produced by diamond wire sawing and by standard slurry sawing, both before and after alkaline etching. Both as-cut wafers and wafers etched in 47% KOH at 75°C for different etching times have been studied. Transmission electron microscope (TEM) investigations of the as-cut slurry wafers show an un-even surface and up to 4 µm deep micro cracks compared to the FAS wafers. Atomic force microscope (AFM) and scanning electron microscope (SEM) analyses of the ascut FAS wafers show a smooth wave-like pattern on the surface with a period of about 15 µm and amplitude of about 1 µm. During the initial part of the etching, square inverted pillars were formed for both types of wafers. The inverted pillars were initially deeper for the slurry cut wafers. The size in lateral direction of the inverted pillars increases with etching time.