On yield, fault distributions, and clustering of particles

Increasing the levels of semiconductor integration to larger chips with more transistors causes the fault and defect distributions of VLSI memory chips to deviate increasingly further from simple random Poisson statistics. The spatial distributions of particles on semiconductor wafers have been analyzed to gain insight into the nature of integrated circuit defect statistics. The analysis was done using grids of squares known as quadrats. It was found that the cluster parameter, which until now has been treated as a constant, did vary with quadrat area. The results also show that the deviation from Poisson statistics continues to increase into the realm of wafer-scale integration or WSI. Computer simulations were used to verify this effect.