Image-processing-based analysis of subsurface damage in diamond wire sawing of silicon wafer

Subsurface damages (SSDs) greatly deteriorate the mechanical properties and increase the processing costs of the wire-sawn silicon wafer, which should be evaluated accurately and quickly. In this paper, a theoretical model is presented for determining the SSD depth with the surface fracture parameters of the silicon wafer based on the scratch fracture mechanics of brittle materials. Meanwhile, an image processing method is integrated into the model to extract the fracture parameters. To validate the model, a series of experiments were carried out on (100) single-crystal silicon ingots using multi-wire sawing equipment under various slicing parameters. The wafer surface morphology was observed by laser scanning confocal microscopy, and its subsurface morphology was determined by cross-section scanning microscopy. The determined SSD depth is compared with the experimental one. The result shows that the image-processing-based model can accurately and quickly determine the SSD depth in the silicon wafer with an average relative error of less than 12% and within about 15 seconds. The model provides an important means for non-invasive evaluation of the SSDs in diamond wire sawing of silicon wafer.