Scan Compression

Scan compression is a technique that reduces scan test data volume by compressing stimulus and responses - Decompressors expand tester patterns on-chip and compactors fold responses back to limited tester channels.

What Is Scan compression?

• Definition: A technique that reduces scan test data volume by compressing stimulus and responses.
• Core Mechanism: Decompressors expand tester patterns on-chip and compactors fold responses back to limited tester channels.
• Operational Scope: It is used in semiconductor test and failure-analysis engineering to improve defect detection, localization quality, and production reliability.
• Failure Modes: Over-aggressive compression can reduce diagnostic resolution and increase unknown-value sensitivity.

Why Scan compression Matters

• Test Quality: Better DFT and analysis methods improve true defect detection and reduce escapes.
• Operational Efficiency: Effective workflows shorten debug cycles and reduce costly retest loops.
• Risk Control: Structured diagnostics lower false fails and improve root-cause confidence.
• Manufacturing Reliability: Robust methods increase repeatability across tools, lots, and operating corners.
• Scalable Execution: Well-calibrated techniques support high-volume deployment with stable outcomes.

How It Is Used in Practice

• Method Selection: Choose methods based on defect type, access constraints, and throughput requirements.
• Calibration: Tune compression ratio against coverage, diagnostic quality, and X-tolerance limits.
• Validation: Track coverage, localization precision, repeatability, and field-correlation metrics across releases.

Scan compression is a high-impact practice for dependable semiconductor test and failure-analysis operations - It cuts tester memory and test time for large designs.