Experiment and theoretical prediction for subsurface microcracks and damage depth of multi-crystalline silicon wafer in diamond wire sawing

Diamond wire saw slicing is an important process of multi-crystalline silicon (mc-Si) solar cell substrate processing. In wire sawing of silicon crystal, the brittleness removal of materials will lead to subsurface microcrack damage, reduce the fracture strength, increase the breakage probability of the as-sawn wafer and affect the subsequent surface etching texture of wafer. In this paper, a mathematical model calculating subsurface damage depth (SSD) of mc-Si is established based on the analysis of subsurface crack system in diamond wire sawing process. The correctness and rationality of the model are verified by experiments. Then, the model is used to predict the variation trend of the microcracks number (CN) and subsurface damage depth under different process parameters and saw wire parameters. The results show that the SSD decreases and CN increases with the increase of wire speed and decrease of feed speed; With the increase of abrasive density on wire surface, the SSD decreases and CN increase. The change of abrasive average size has little effect on the SSD and CN; a smaller abrasive size range is beneficial to reduce the SSD and increase CN.