Built-In Self-Test/Self-Diagnosis for RAMs

Built-In Self-Test/Self-Diagnosis for RAMs Jin-Fu Li Advanced Reliable Systems (ARES) Lab. Department of Electrical Engineering National Central University Jhongli, Taiwan

Outline • Introduction • Fault Models and Test Algorithms • Fault models • Test Algorithms • Memory BIST/BISD Design • BIST Design • BISD Design • Memory Diagnosis • Fault Diagnosis • Defect Diagnosis

Introduction • Modern system-on-chip (SOC) designs typically consist of hundreds of memories • Memories usually dominate the chip area • Furthermore, memories are designed with the aggressive design rules such that they are prone to defects • Thus the memory yield heavily impacts the SOC yield • Increasing memory yield can significantly increase the SOC yield • Yield-enhancement techniques for memories • Diagnosis & repair

SOC Yield • Yield of an SOC • Improve the yields of memories can drastically increase the yields of SOCs • For example, UltraSparc chip yield Source: R. Rajsuman, IEEE D&T, 2001

Yield Learning Curve Yield Diagnosis/repair Mature phase Repair Early phase Intermediate phase Time

Testing and Repair of RAMs in SOCs 16-core SPARC (Oracle) Niagara2 (Sun) POWER6 (IBM) • DFT features: • Scan test + test compression • Programmable memory built-in self-test (MBIST) + repair • SerDes internal and external look-back tests • DFT features: • 32 Scans + ATPG • BIST for arrays • …. • DFT features: • Logic BIST • BIST for arrays • BISR for arrays • …

Fault Models and Test Algorithms

Undoubtedly, 3D RAM will be one pioneer product using 3D integration technology Some differences exist between a 2D RAM and a 3D RAM with TSVs Those differences incur some challenges on the testing and repair of 3D RAMs Effective testing and repair techniques thus are imperative for the production of 3D RAMs Due to the uncertainty of a 3D RAM DFT/DFY/DFR techniques with the feature of adaptability is one main trend Conclusions

Built-In Self-Test/Self-Diagnosis for RAMs