This letter reports on residual stress measurement in thin crystalline silicon wafers with a full-field near-infrared polariscope. Residual stress is analyzed in combination with observed surface defects, and the results are related to measured fracture strength variation in the wafers. Measurements indicate that there is a sawing process-related residual stress in the as-cut wafers, and that etch-removal of ∼5 μm from the wafer surface eliminates a damage layer that can significantly reduce the residual stress in the wafer, and therefore increases the observed fracture strength. There is a corresponding 2 to 3 μm reduction in the observed characteristic defect size after etching. Fracture strength anisotropy observed in the wafers is related to defect orientation (scratching grooves and microcracks) caused by the sawing process.

Abstract-This paper discusses the influence of tribology on the mechanical properties of cutting, shaping and forming silicon wafers. These processes, such as multi wire slurry sawing, diamond wire sawing, lapping and grinding, Chemical Mechanical Polishing (CMP), and dicing, utilize either a two-body or a three-body material removal, where the fundamental cutting process results from micro-fracturing of silicon by the hard abrasives. There are specific types of defects and related fracture strength characteristics for each process. The associated surface and subsurface damage, especially microcracks, have a dominant effect on the fracture strength of the silicon substrates, even playing a more significant role than edge chipping. There is a need to reduce the surface and subsurface damage, possibly through ductile regime machining/polishing, to improve the mechanical strength.