Integration of Hard Repair Techniques with ECC for Enhancing Fabrication Yield and Reliability of Embedded Memories

Error correction code (ECC) and hard repair (built-in self-repair) techniques by using redundancies have been widely used for improving the yield and reliability of memories. The target faults of these two schemes are soft errors and permanent faults, respectively. In recent works, there are also some techniques integrating ECC and BISR to deal with soft errors and hard defects simultaneously. However, this will compromise reliability since some of the ECC protection capability is used for repairing hard defects. To cure this dilemma, we propose an ECC-enhanced BISR (EBISR) technique which uses ECC to repair single permanent faults first and spares for the remaining faults in the production/power-on test and repair stage. However, techniques are proposed to maintain the original reliability during the on-line test and repair stage. We also propose the corresponding hardware architecture of the EBISR scheme. A simulator is implemented to evaluate the hardware overhead, repair rate, and reliability. Experimental results show that the proposed EBISR scheme can improve yield and reliability significantly with negligible hardware overhead.