Hf/Zr Superlattice-Based High-κ Gate Dielectrics with Dipole Layer Engineering for Advanced CMOS

Advanced logic transistors require gate dielectrics that achieve subnanometer equivalent oxide thickness (EOT), suppress leakage, and satisfy three key requirements: (i) compatibility with RMG-like high-temperature processing, (ii) sufficient V_th tunability for multi-V_th design, and (iii) high device reliability. However, meeting all of these requirements at once has been difficult with conventional high-κ systems. In this work, we demonstrate that our Hf/Zr-based gate stacks quantitatively satisfy these conditions. (i) After a 700 °C N₂ anneal, the HZH superlattice achieves EOT = 7.3 Å, lower than conventional HfO₂-only stacks (8.5 Å) while maintaining comparable leakage. (ii) Embedding a 3 Å Al₂O₃ dipole within the HfO₂/ZrO₂/HfO₂ superlattice (HZHA) breaks the conventional dipole trade-off, achieving an 8.4 Å EOT─lower than the 9.0 Å of a standard HfO₂/Al₂O₃ stack─while providing a > 200 mV V_FB shift, thereby enabling multi-V_th tuning without compromising scaling. (iii) Furthermore, under -2 V negative-bias temperature stress at 125 °C for 100 s, HZHA and HA exhibit comparable V_FB drifts of 87 mV and 97 mV, respectively, confirming that strong V_th tunability and subnanometer EOT can be achieved without compromising stability. In addition to these quantitative advances, this study reveals previously unreported physical insights into the dipole behavior and interfacial diffusion in ultrathin Hf/Zr multilayers. These results establish HZHA as an RMG-compatible, V_th-tunable, low-EOT dielectric platform capable of supporting logic scaling beyond the 1 nm frontier.