DC-biased PEALD and post-annealing for highly crystalline HfOx thin films

Abstract

As semiconductor devices such as dynamic random-access memory continue to scale down, the demand for high-quality, ultrathin high-k dielectric films has become increasingly critical. In this study, HfOx thin films were deposited by plasma-enhanced atomic layer deposition (PEALD) using a DC-biased remote plasma system designed to enhance oxidation reactivity while minimizing ion-induced damage. A grid-type DC plate was incorporated into the remote plasma configuration, enabling the application of DC bias during the plasma step. This modification significantly increased electron density and radical concentration, as confirmed by optical emission spectroscopy and Langmuir probe measurements. Comprehensive material characterization—including spectroscopic ellipsometry, atomic force microscopy, Auger electron spectroscopy, transmission electron microscopy, grazing-incidence X-ray diffraction, and X-ray photoelectron spectroscopy—demonstrated that applying DC bias resulted in improved conformality, reduced surface roughness, improved Hf:O ratio, and enhanced crystallinity, particularly through the promotion of the tetragonal phase following annealing. Electrical characterization of metal–insulator–metal capacitor structures further revealed that films deposited with DC bias and subsequently annealed exhibited an enhanced dielectric constant of 27 while maintaining acceptable leakage current levels. These results demonstrate that integrating a DC-biased remote plasma system into the PEALD process is an effective approach for achieving high-performance HfOx dielectrics, offering strong potential for next-generation complementary metal-oxide-semiconductor and memory device applications.