Radial yield variations in semiconductor wafers

Detailed examination of yield data from several different products in two different technologies and two different wafer sizes has shown a pronounced radial dependence. In all cases, the yield profile has a distinct knee starting at about 10 mm from the wafer periphery, dropping steeply within the final 5 mm. The similarity in yield profile near the periphery across all the products examined suggests that edge yield loss is of a gross nature and is not caused by design, technology, wafer size, or random defects.