Yield and quality control
On the same wafer, why does making chip area smaller greatly increase the number of good chips per wafer?
- ABecause chips become heavier
- BBecause the wafer color changes
- CBecause the number of chips increases and the probability of a defect per chip also falls
Show answer and explanation
Answer: C. Because the number of chips increases and the probability of a defect per chip also falls
Smaller chips mean more chips per wafer. In addition, at the same defect density, smaller chips are less likely to contain a defect, so yield rises. Because the two effects combine, the number of good chips increases more than the area ratio alone.