High surface integrity fabrication of silicon wafers using a newly developed nonwoven structured grind-polishing wheel

Abstract

Silicon wafer is a predominant substrate material in integrated circuits (IC) manufacturing. Currently, grinding is employed as a major machining method for back-thinning and flattening of the wafers. To obtain high surface/subsurface quality of ground silicon wafer, a novel nonwoven structured grind-polishing wheel with ultrafine abrasives is developed in this work. The developed wheel uses zirconia (ZrO2) with a grit diameter of 200 nm as abrasives, where the nonwoven fibers are employed as structures to support the abrasives. By measuring the surface and subsurface quality of ground silicon, grinding performance of the developed grind-polishing wheel is investigated and compared to that of #8000 diamond wheel, which is a commercial grinding wheel with the smallest grit size. The grinding experimental results show that the surface produced by the developed wheel has a surface roughness Ra of 0.45 nm, and a thickness of subsurface damage layer about 67 nm. In addition, the material removal rate for silicon wafers machined by the developed wheel is 0.86 μm/min. Compared with the #8000 diamond wheel, the developed wheel is more suitable for the semi-fine finishing process to produce a smooth surface at reduced time and cost.