In-Series Phase-Change Memory Pair for Enhanced Data Retention and Large Window in Automotive Application

Non-volatile memory (NVM) constitutes a vital component within automotive embedded systems and must comply with specific reliability standards. However, very few NVMs meet the stringent grade 0 criteria outlined by AEC-Q100, which necessitates operation up to 150°C. While phase-change memory (PCM) demonstrates relative resilience to high temperatures, its inherent trade-off between retention and on/off ratio remains unavoidable. To overcome this trade-off, we propose connecting two complementary phase-change materials in series to leverage the strengths of each material. One material provides large on/off ratio even right after the RESET programming, while another material provides a long retention time, enabling the 2R-device to secure sufficient margin throughout the long retention period for large temperature range. After the retention-failure of one device with a sizable on/off ratio, the other device, with increasing resistance due to drift, maintains an adequate margin. Experimental demonstrations of 2R-devices, based on GST225 and GaSbGe, exhibit their operation at temperatures of up to 130°C, exhibiting a larger window compared to PCM only with GaSbGe. Furthermore, the 10-year retention temperature of the 2R-device is 153°C, suggesting that 2R-devices have the potential to meet grade 0 requirements.