Defect density, often written D0, counts killer defects per square centimeter. The simple Poisson yield model predicts die yield as e to the power of minus die area times D0: a 1 square centimeter die at a D0 of 0.1 yields about 90 percent, and at 0.5 only about 61 percent. Real defects cluster, so the Murphy model or a negative binomial model with a clustering factor fits large die better and predicts higher yield than plain Poisson.
D0 came down from 0.25 to 0.12 after the filter change. On a 1 square centimeter die that's about eleven points of yield.
Also heard as
- D0
- D-naught
- defects per square centimeter
Related terms
Yield
Fraction of units that come out good at a step or across a whole process, the headline number for any production line.
Killer defect
Defect that lands where it causes a die to fail, as opposed to a harmless cosmetic or nuisance defect.
Wafer map
Picture of a wafer showing each die's test result or measurement by location, used to spot spatial failure patterns.
DPMO
Defects per million opportunities: defect count scaled by the number of chances for a defect in each unit.