Emerging Non-Volatile Memories for Ultra-Low Power Applications

For many decades charge based storage memory technologies (DRAM, flash memory, and other) have been successfully scaled down to achieve higher speed and increased density of memory chips at lower bit cost. However, memories based on this storage principle are gradually approaching the physical limits of scalability. Although a new cell structure for DRAM has been developed by industry to overcome the scaling challenges at 30nm, future size reduction below 20nm is facing physical limitations and a process complexity results in high manufacturing costs [1]. This is the reason that new types of memories based on a different storage principle are gaining momentum. Apart from good scalability, a new type of memory must also exhibit low operating voltages, low power consumption, high operation speed, long retention time, high endurance, and a simple structure [2]. From new technologies two of the most promising candidates for future universal memory are spin transfer torque RAM (STT-MRAM) and resistive RAM (RRAM). Currently, STT-MRAM and RRAM have been demonstrated on 64 Mb [3] and 4Mb [4] test chips, respectively. These technologies would be manufacturable within 5–10 years [5]. First we briefly review the nearest future of DRAM technology, including ZRAM as a potential replacement of DRAM. Then we outline the possibility of creating a universal non-volatile memory based on resistance change and spin, the current state of these technologies, trends and challenges, and demonstrate modeling approaches.