Improved Immunity to Sub-Cycling Induced Instability for Triple-Level Cell Ferroelectric FET Memory by Depositing HfZrOₓ on NH₃ Plasma-Treated Si

Split-up effect caused by sub-cycling would change the coercive voltage ( $\text{V}_{\textrm {C}}$ ) of a ferroelectric HfZrO _x (HZO) film by the induced local internal field due to oxygen vacancy (Vo) related behaviors and is detrimental to MLC operation. By depositing the HZO on NH ₃ plasma-treated Si, due to the high-quality SiN _x interfacial layer that reduces the amount of Vo in the HZO, the ferroelectric FET (FeFET) memory reveals a large memory window of 3.2 V by +6/-5 V with $5 {\mu } \text{s}$ pulse width and much improved reliability against sub-cycling for multi-level cell (MLC, 2 bits/cell) operation than those without plasma treatment. The FeFET memory also for the first time displays the stable (threshold voltage) $\text{V}_{\textrm {TH}}$ for each state for triple-level cell (TLC, 3 bits/cell) operation up to $3\times 10^{\textrm {3}}$ cycles that meets the industry requirement under strict sub-cycling and exhibiting quadruple-level cell (QLC, 4 bits/cell) operation with desirable retention, ushering in new paradigms for advanced high-density memory applications.