Polarization-State-DependentCharge Screening in Metal-Ferroelectric-MetalMemcapacitors Enabled by an IGZO Oxygen Reservoir Layer

초록

An indium-gallium-zinc oxide (IGZO) oxygen reservoir layer (ORL) was introduced at the bottom interface of W/Hf0.5Zr0.5O2 (HZO)/W memcapacitors to induce asymmetric capacitance modulation without relying on domain pinning. The IGZO layer exhibits a polarization-state-dependent capacitance response, transitioning between a limited-screening state and an efficient-screening state during the bias sweep, which modulates the charge-screening response of the stack. This polarization-state-dependent charge-screening response results in asymmetric capacitance peaks during polarization switching and enables a significantly enhanced capacitance memory window (CMW). Equivalent circuit analysis quantitatively reveals the contribution of the IGZO layer and confirms its role in governing the observed C-V asymmetry. Systematic variation of stack configuration and IGZO thickness demonstrates that a bottom-interfaced, thickness-optimized IGZO layer maximizes both asymmetry and CMW. In addition, the IGZO layer functions as an oxygen reservoir, suppressing oxygen-vacancy-induced degradation and improving endurance. The device further exhibits stable analog synaptic characteristics, and a retention-aware state pruning strategy is introduced to mitigate retention-induced degradation, preserving read margin and improving computational accuracy under noise-aware conditions. These results establish IGZO-integrated MFM memcapacitors as a viable platform for high-performance ferroelectric capacitive memory and neuromorphic systems.

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