Qualification Lot

A qualification lot is a special lot of wafers processed to validate that a new process, equipment, recipe, or material change meets all specifications before production release. Purpose: Demonstrate that the change produces results equivalent to or better than the existing qualified process. Risk mitigation before committing production material. Triggers: New tool installation, major preventive maintenance, recipe change, new material supplier, process improvement implementation, technology transfer. Contents: Multiple wafers (13-25 typically) representing full process conditions. May include multiple product types or test vehicles. Test plan: Comprehensive measurement plan covering all critical parameters - CD, thickness, overlay, defects, parametric electrical results, reliability. Acceptance criteria: Pre-defined specifications that qualification lot must meet. Usually same as production specifications, sometimes tighter. Duration: Qualification process can take days to weeks depending on scope. Full process qual may require processing through entire flow. Short-loop qualification: Process only the changed steps plus key downstream steps rather than full flow. Faster but less comprehensive. Split lot: May split qualification lot between qualified and new process for direct comparison. Statistical requirements: Multiple wafers and sites to demonstrate process capability (Cpk) with statistical confidence. Sign-off: Qualification results reviewed and signed off by process engineering, quality, and manufacturing management. Documentation: Formal qualification report with all data, analysis, and approval signatures. Retained for audits and regulatory compliance.