BIST-Based Fault Diagnosis for PCM With Enhanced Test Scheme and Fault-Free Region Finding Algorithm

As one of the most promising candidates for nonvolatile memory, phase change memory (PCM) technology has shown great performance advantages in market applications. However, the conventional test methods have not kept pace with the development. In this article, focusing on specific PCM faults and others, an enhanced march test algorithm is proposed to achieve 100% fault coverage and diagnostic accuracy in bit-oriented PCM. The proposed algorithm is then converted for word-oriented PCM and equipped with capability to detect potential intraword impact. In addition, to reduce the dependence of memory test on the external devices, a novel storage scheme of fault information is devised. Through the modeling and simulation in C-language, this method is proven to improve the probability of finding the predefined fault-free regions in the tested memory. Finally, combining the enhanced test algorithm and the novel storage scheme, a built-in self-test (BIST) march test scheme is proposed, realizing the independent test of PCM without any external equipment. By comparison, the result of experiments, which are performed with C-language, proves that the proposed test scheme not only increases the fault coverage and diagnostic accuracy, but also reduces the additional area overhead.