line yield

**Line Yield** is the **fraction of wafers that successfully complete the entire manufacturing process flow** — measuring the manufacturing efficiency from wafer start to finished wafer, accounting for wafer breakage, process holds, scrapped wafers, and wafers removed for engineering analysis. **Line Yield Calculation** - **Formula**: $Y_{line} = frac{N_{out}}{N_{in}}$ — wafers out divided by wafers started. - **Loss Sources**: Wafer breakage, process scrap (misprocessing, contamination), engineering pulls, test wafer consumption. - **Typical**: Mature fabs achieve >95% line yield — <5% of started wafers are lost. - **Per-Step**: Each process step has its own mini line yield — cumulative product gives overall line yield. **Why It Matters** - **Cost**: Every lost wafer represents wasted processing cost ($3K-$15K per wafer at advanced nodes). - **Capacity**: Line yield directly affects effective fab capacity — 95% line yield means 5% capacity is wasted. - **Root Cause**: Tracking line yield by process step identifies the biggest loss contributors. **Line Yield** is **how many wafers survive the journey** — the fraction of started wafers that successfully complete the entire manufacturing process.