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

TL;DR

This paper introduces a new Hf/Zr-based gate dielectric that enables advanced transistors by achieving ultra-thin oxide thickness and reliable performance.

Contribution

HZHA superlattices with embedded Al2O3 dipoles enable subnanometer EOT and multi-Vth tuning while maintaining stability.

Findings

HZH superlattices achieve 7.3 Å EOT after high-temperature annealing with low leakage.

HZHA stacks provide 8.4 Å EOT and >200 mV VFB shift for multi-Vth design.

HZHA and HA stacks show similar VFB drift under stress, confirming stability.

Abstract

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.

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