Adaptive Sensing Voltage Modulation Technique in Cross-Point OTS-PRAM

Phase-change random access memory with an ovonic threshold switch (OTS-PRAM) has become increasingly popular as an alternative to resolve the problem caused by the small capacity of dynamic random access memory and the high latency of NAND flash memory in computing systems. However, an OTS has a temperature-dependent OFF-current ( I_{\mathrm {off}} ) and threshold voltage ( V_{\mathrm {TH}} ). This causes I_{\mathrm {off}} of a cell ( I_{\mathrm {off\_{}CELL}} ) and V_{\mathrm {TH}} of a cell ( V_{\mathrm {TH\_{}CELL}} ) to become temperature-dependent, inducing a sensing error during read operations. In this article, an adaptive sensing voltage modulation (ASVM) technique is proposed that adaptively controls the bitline and wordline voltage depending on the change in temperature to compensate for the temperature-dependent variation in voltage drop caused by I_{\mathrm {off\_{}CELL}} and V_{\mathrm {TH\_{}CELL}} . The HSPICE simulation results, with an industry-compatible 250-nm complementary metal-oxide-semiconductor process for the 20-nm PRAM technology, show that the OTS-PRAM with the proposed ASVM can achieve a bit error rate below 0.1 ppm within the operating temperature range of 0 °C-85 °C.