An investigation of rod-like defects in MOS 12

A unique defect type was detected by routine KLA inspection. The shape of the defect was rod like, about 1/2 micron in width with length varying from 1 to several microns. The defects were located in the notch area (see Fig. 1) with defect counts often exceeding one thousand per wafer. Through the analysis of bitmap/visual defect overlay, it was shown these rod-like defects are yield killers. This was confirmed by cumulative probe yield maps which showed lower yields for dice located near the notch. In this paper, the mechanism for the rod-like defect formation will be described in detail. The techniques used to investigate the mechanism, defect characteristics, and yield impact will be discussed. The implementation of the solution to eliminate the rod defects will also be discussed.