FeFET Based Nonvolatile TCAM and DRAM Development

Ferroelectric Field Effect Transistor (FeFET) is a promising nonvolatile device which provides high integration density, fast programming speed, and excellent CMOS compatibility. In general, the non-volatility of FeFET is impacted by its physical structure and there is a trade-off between data retention time and device endurance. To improve the cell endurance, for example, the ferroelectric layer of FeFET needs to be programmed to a low polarization level, leading to a short retention time. In ferroelectric DRAM (FeDRAM) design, degradation in FeFET retention time and write-read disturbance requires the FeDRAM cells to be periodically refreshed in order to prevent data loss. In this work, I propose a novel adaptive refreshing and read voltage control scheme to minimize the energy overheads associated with FeDRAM refreshing while still achieve high cell access reliability. In addition to the DRAM application FeFET based TCAM memory is also studied. TCAM (ternary content addressable memory) is a special memory type that can compare input search data with stored data, and return location (sometime, the associated content) of matched data. TCAM is widely used in microprocessor designs as well as communication chip, e.g., IP-routing. Following technology advances of emerging nonvolatile memories (eNVM), applying eNVM to TCAM designs becomes attractive to achieve high density and low standby power. In this work, I examined the applications of three promising eNVM tech-nologies, i.e., magnetic tunneling junction (MTJ), memristor, and ferroelectric memory field effect transistor (FeMFET), in the design of nonvolatile TCAM cells. All these technologies can achieve close-to-zero standby power though each of them has very different pros and cons