An efficient diagnosis scheme for random access memories

Diagnosis techniques are important for memory yield improvement. This paper presents an efficient diagnosis scheme for RAMs. The diagnosis scheme is composed of three March-based algorithms. A March-15N algorithm is used for locating and partially diagnosing faults of bit-oriented or word-oriented memories, where N represents the address number Then a 3N March-like algorithm is used for locating the aggressor words (bits) of coupling faults in word-oriented (bit-oriented) memories. It also can distinguish the faults which cannot be identified by the March-15N algorithm. Thus the proposed diagnosis scheme can achieve full diagnosis and aggressor location with (15N + 3mN) Read/Write operations for a RAM with m CFs. Subsequently, an adaptive March-like algorithm is also proposed to locate the aggressor bit in the aggressor word with 4log(2)B Read/Write operations, where B is the word width. Analysis results show that the proposed diagnosis scheme has higher diagnostic resolution and lower time complexity than other known fault location and fault diagnosis approaches.