Ferroelectric Engineering of FeFET Toward Multi-Level Coding for High-Density Nonvolatile Memory

The prospect of ferroelectric oxide by ALD (Atomic Layer Deposition) with bistable nature feature of hysteresis loops satisfies the demands of the storage signal purpose for memory. An inserted Al 2 O 3 insulator to separate the ferroelectric layers and to avoid the formation of non-ferroelectric phases is a useful method to enhance the memory window (MW) for multi-level cell (MLC) applications. The nonidentical double-HfZrO 2 (HZO) FeFET has not only a larger MW than single HZO but also improve error rate (ER). Recently, superlattice (SL) HfO 2 -ZrO 2 with physical thickness of 5 nm and low phase fraction ratio 0.101:1 of monoclinic-phase (m-phase) to orthorhombic-phase (o-phase) investigated by geometrical phase analysis (GPA) is demonstrated. The homogeneous and congruous of SL-HfZrO 2 (HZO) with sufficient f erroelectric-domain is integrated as multi-HZO stack FeFETs for multibit NVM with low |V PG/ER | = 4 V, ultra-low error rate = 7.5×10-16, record high 2-bit endurance for 109 cycles, and stable data retention > 104 s. The superlattice technique for FE-HZO is a promising concept with elevating the coherence of domain access due to high o-phase toward emerging memory applications.