FeFET-based MirrorBit cell for High-density NVM storage

HfO2-based Ferroelectric field-effect transistor (FeFET) has become a center of attraction for non-volatile memory applications because of their low power, fast switching speed, high scalability, and CMOS compatibility. In this work, we show an n-channel FeFET-based Multibit memory, termed MirrorBit, which effectively doubles the chip density via programming the gradient ferroelectric polarizations in the gate using an appropriate biasing scheme. We have experimentally demonstrated MirrorBit on GlobalFoundries HfO2-based FeFET devices fabricated at 28 nm bulk HKMG CMOS technology. Retention of MirrorBit states has been shown up to $10^5$ s at different temperatures. Also, the endurance is found to be more than $10^3$ cycles. A TCAD simulation is also presented to explain the origin and working of MirrorBit states based on the FeFET model calibrated using the GlobalFoundries FeFET device. We have also proposed the array-level implementation and sensing methodology of the MirrorBit memory. Thus, we have converted 1-bit FeFET into 2-bit FeFET using a particular programming scheme in existing FeFET, without needing any notable fabrication process alteration, to double the chip density for high-density non-volatile memory storage.