Achieving Equivalent Oxide Thickness Scaling of a ZrO₂ Dielectric Thin Film via Gd Doping without Sacrificing Tetragonal Crystallinity

In this study, we examine the potential of Gd dopants to replace Al dopants in ZrO₂-based dynamic random-access memory (DRAM) capacitors. While using Al dopants is a practical approach to solving the leakage current problem of ZrO₂, it induces tetragonal crystallinity deterioration of the ZrO₂ dielectric thin film, thereby decreasing the capacitance. The Gd-doped ZrO₂ dielectric thin film demonstrated promising results in suppressing the leakage current while preserving the tetragonal crystallinity. Moreover, the suppression of the leakage current mechanism by Gd doping is discussed and shown to be due to the increasing conduction band offset caused by the acceptor (p-type) doping effect. Consequently, the Gd-doped ZrO₂ achieved a minimum equivalent oxide thickness value of 0.76 nm while satisfying the specifications of the DRAM leakage current density (<10^-7 A/cm² at an applied voltage of +0.8 V).