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 Vth tunability for multi-Vth 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 VFB shift, thereby enabling multi-Vth tuning without compromising scaling. (iii) Furthermore, under -2 V negative-bias temperature stress at 125 °C for 100 s, HZHA and HA exhibit comparable VFB drifts of 87 mV and 97 mV, respectively, confirming that strong Vth 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, Vth-tunable, low-EOT dielectric platform capable of supporting logic scaling beyond the 1 nm frontier.