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.