Postdeposition Annealing‐Induced Suppression of Interfacial Dead Layers and Oxygen Vacancies in Source‐Tied Covering Metal‐Integrated Oxide‐Channel FeFETs

Postdeposition annealing (PDA) with an insulating Al ₂ O ₃ capping layer is demonstrated as a crystallization strategy for reliable source‐tied covering metal (SCM)‐integrated oxide‐channel ferroelectric field‐effect transistors (FeFETs). Conventional postmetallization annealing (PMA) with TiN promotes high remanent polarization but induces oxygen scavenging, oxygen‐vacancy formation, and interfacial dead layers, which accelerate leakage and cycling degradation. By decoupling HZO crystallization from direct HZO/TiN interaction, the PDA process suppresses interfacial defect generation and stabilizes the ferroelectric/channel stack. Capacitor analysis shows that PDA‐treated HZO exhibits lower leakage current, a thinner interfacial dead layer, and endurance exceeding 10 ⁶ cycles. When integrated into SCM‐integrated FeFETs using an In ₂ O ₃ channel, the PDA scheme maintains a stable memory window of 12.63 V after 10 ³ cycling during ISPP/ISPE operation and preserves an 8.43 V retention window after cycling. The devices further exhibit endurance up to 10 ⁵ cycles, outperforming PMA counterparts that suffer rapid memory‐window collapse. These results establish PDA using an insulating capping layer as an effective route toward reliable, low‐thermal‐budget oxide‐channel FeFETs for high‐density three‐dimensional ferroelectric NAND memory.