lower specification limit

**LSL** (Lower Specification Limit) is the **minimum acceptable value for a measured parameter** — the lower engineering boundary below which the product fails to meet performance, reliability, or quality requirements. **LSL in Practice** - **CD Control**: LSL for gate CD might be target - 2nm — below this causes leakage or reliability issues. - **Film Thickness**: LSL for barrier layer thickness — below this allows metal diffusion. - **Adhesion Strength**: LSL for film adhesion — below this causes delamination. - **Drive Current**: LSL for transistor Idsat — below this means the transistor is too slow. **Why It Matters** - **Pass/Fail**: Measurements below LSL result in product rejection — the lower quality boundary. - **Cpk (Lower)**: $Cpk_{lower} = frac{ar{x} - LSL}{3sigma}$ — measures capability relative to the lower limit. - **Asymmetric Risk**: Upper and lower failures often have different consequences — LSL and USL may have different criticalities. **LSL** is **the minimum required** — the lower engineering limit below which product performance or reliability is compromised.