Defect analysis and defect tolerant design of multi-port SRAMs

Multi-port SRAMs are often implemented using static random access memory (SRAM) due to its fast operation and the ability to support multiple read and write operations simultaneously, thus increasing data throughput in embedded systems and meeting the expected demands of parallel or pipelined microprocessors. With the continuous scaling of transistor feature size, designing low power robust memories and investigating their failure characteristics become critical. In this paper, we study the defects occurring in the multi-port SRAM cells. The memory is modeled at the transistor level and analyzed for electrical defects by applying a set of test patterns. Not only have existing models been taken into account in our simulation but also a new fault model, namely, simultaneous deceptive destructive read fault for the multi-port memory is introduced. In addition, we extend our study to the defect tolerant design of memories by proposing a differential current-mode sense amplifier for 3-port SRAM based register file. We examine the fault models of resistive defects within the SRAM cell and its failure boundary. A read disturb fault for multi-port memories is tested on the faulty cell by simultaneous read operations with different numbers of ports. Experimental results show that the proposed current-mode sensing scheme has improvements for memory fault-tolerance of resistive defects at 4.6× for dual-port read and 5.8× for 3-port read compared to voltage-mode sensing with 0.18 μm manufacturing process technology.