Plasma-Enhanced Atomic Layer Deposition of Yttrium Carbide Thin Films as a Promising Transition Metal Carbide for Dual Diffusion Barrier in Cu and Ru Metallization

Abstract

Transition metal carbides (TMCs) possess superior properties compared to transition metal nitrides (TMNs). However, despite their advantages, atomic layer deposition (ALD) and plasma-enhanced ALD (PEALD) techniques for these materials, particularly yttrium carbide (YCx), have not been thoroughly investigated. This study introduces a PEALD approach for fabricating high-quality YCx thin films with excellent uniformity and precise thickness control. With a focus on their potential as advanced diffusion barriers, the research employs a metal-organic Y precursor in combination with H-2 plasma to produce highly crystalline, low-resistivity YCx films. To refine the deposition process, critical parameters such as temperature (ranging from 150 degrees C to 350 degrees C), precursor pulse time, and plasma exposure duration were carefully optimized. Under these conditions, the film exhibited a growth rate of similar to 0.13 nm per cycle at 250 degrees C. Structural and compositional analysis using advanced microscopy and spectroscopic techniques confirmed the formation of a nanocrystalline rhombohedral phase, a C-to-Y atomic ratio of similar to 0.46, and a film density of 4.63 g/cm(3). Furthermore, the deposited films demonstrated exceptional step coverage of 95% within a trench structure with an aspect ratio of similar to 1.5 and a bottom width of 265 nm. Post-annealing studies revealed that the films maintained their thermal and crystallographic stability between 500 degrees C and 800 degrees C. Additionally, the YCx films effectively functioned as a dual diffusion barrier for Cu and Ru (40 nm), exhibiting thermal stability up to 900 degrees C. These results underscore the potential of YCx films for applications in advanced semiconductor technologies.