A built-in self-repair scheme for multiport RAMs

Built-in self-repair (BISR) techniques have been widely used for enhancing the yield of embedded memories. This paper presents an efficient BISR scheme for multiport RAMs (MPRAMs). The BISR scheme has a defect-location module (DLM) executing a defect-location algorithm to locate inter-port defects. This enhances the fault-location capability of the applied test algorithm with only a few amount of cost of testing time. A built-in redundancy analyzer (BIRA) executing a proposed redundancy analysis algorithm is also proposed to allocate two-dimension redundancy of MPRAMs. Experimental results show that if a faulty MPRAM has 20% inter-port faults, the DLM can boost the increment of repair rate from 8.4% to 14.4% for different redundancy configurations. The area cost of the BIRA and DLM is small, it is only about 1% for a 4096 × 128-bit MPRAM with 1 spare row and 1 spare IO.