Cumulative Yield is the total yield considering all yield loss mechanisms across the entire manufacturing flow — calculated as the product of individual yields at each stage: $Y_{cum} = Y_{line} imes Y_{wafer} imes Y_{die} imes Y_{package} imes Y_{test}$, representing the overall fraction of good products from starting wafers.

Cumulative Yield Components

• Line Yield: Fraction of wafers completing the process flow.
• Wafer Yield (Die Yield): Fraction of die on each wafer that are functional — the dominant yield component.
• Package Yield: Fraction of die that survive packaging — assembly and wire bonding/bumping yield.
• Test Yield: Fraction of packaged devices that pass final test — functional and parametric testing.

Why It Matters

• Total Cost: Cumulative yield determines the true cost per good die — all losses compound.
• Bottleneck: The lowest-yielding step dominates — focusing improvement on the bottleneck has the most impact.
• Economics: Going from 90% to 95% yield at any step reduces cost per good die by ~5%.

Cumulative Yield is the bottom line of manufacturing — the overall fraction of good chips from the total manufacturing investment.