A new test algorithm for bit-line sensitive faults in super high density memories

As the density of memories increases, unwanted interference between cells and coupling noise between bit-lines are increased and testing high density memories for a high degree of fault coverage can require either a relatively large number of test vectors or a significant amount of additional test circuitry. Conventional test algorithms have focused on faults between neighborhood cells, not neighborhood bit-lines. A new algorithm for NPSFs, and neighborhood bit-line sensitive faults (NBLSFs) based on the NPSFs are proposed. Instead of the conventional five-cell and nine-cell physical neighborhood layouts to test memory cells, a three-cell layout which is a minimum size for NBLSF detection is used. To consider faults by maximum coupling noise by neighborhood bit-lines, we added refresh operation after write operation in the test procedure (i.e., write→refresh→read). Also, we show that the proposed algorithm can detect stuck-at faults, transition faults, conventional pattern sensitive faults, and neighborhood bit-line sensitive faults