Effect of La and Si additives in Zr-doped HfO2 capacitors for pseudo-linear high-κ dielectric applications

Abstract

This study investigates the impact of dopants on Hf_1–xZr_xO₂-based capacitors for high-performance, hysteresis-free dielectric applications. Control of the crystalline structure of Hf_1–xZr_xO₂ films is crucial for achieving superior dielectric properties. The tetragonal (t) phase of Hf_1–xZr_xO₂ exhibits anti-ferroelectric (AFE) characteristics and shows promise due to its high dielectric constant (κ). However, hysteresis behavior in polarization–voltage sweeps due to AFE behavior presents a significant challenge, primarily due to the high energy loss when implemented in dynamic random-access-memory (DRAM) applications. To achieve hysteresis-free operation, this study focuses on suppressing AFE switching within the DRAM voltage range through Si or La doping in Hf_1–xZr_xO₂ films. Introducing small amounts of Si or La (< 1%) into Hf_1–xZr_xO₂ capacitors effectively diminishes AFE switching by influencing which structural phases are favored: Si doping tends to favor the amorphous phase, while La doping promotes the formation of the t-phase. La doping shows particular promise in enhancing pseudo-linear dielectric performance. ~ 0.9% La-doped Hf_0.25Zr_0.75O₂ capacitors exhibit a markedly improved equivalent oxide thickness (EOT) of ~ 4.8 Å and a reduced leakage current density (J_leak) of ~ 10^–7 A/cm² at 1 V, achieved at back-end-of-line (BEOL) compatible temperatures (< 400 °C). These results demonstrate a promising strategy for advancing energy-efficient high-κ dielectric materials in next-generation memory devices, offering a balanced combination of high capacitance, low leakage current, and BEOL compatibility.

Graphical Abstract