cumulative yield

**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.