Influence of Microcracks on Strength of Diamond Wire Sawn Silicon Substrates

So-called microcracks are crucial for material removal during diamond wire sawing of silicon. But they also reduce the strength of silicon substrates after sawing due to the remaining subsurface damage. In order to investigate the influence of microcracks on strength of diamond wire sawn silicon substrates, more than 180 specimens of {100}-silicon were prepared using a reproducible scratching procedure with a Vickers indenter. Subsequently, 4-point bending tests were conducted parallel and perpendicular to the scratch grooves. The results indicate a clear anisotropy in the mechanical strength, which is mainly caused by median and also affected by radial cracking. The microstructural analysis of specimens with a single scratch or multiple scratches show results as a continuous as well as straight median crack propagation at a nearly constant damage depth over the complete length of the scratch groove. Additionally, in the case of multiple scratching, periodic crack kinking towards pre-damaged zones can be observed and, thus, further emphasises the importance of considering pre-existing damage in terms of material removal mechanisms and strength analyses.