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

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 (YC<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf>), have not been thoroughly investigated. This study introduces a PEALD approach for fabricating high-quality YC<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> 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<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> plasma to produce highly crystalline, low-resistivity YC<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> films. To refine the deposition process, critical parameters such as temperature (ranging from 150 °C to 350 °C), precursor pulse time, and plasma exposure duration were carefully optimized. Under these conditions, the film exhibited a growth rate of ~0.13 nm per cycle at 250 °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 ~0.46, and a film density of 4.63 g/cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup>. Furthermore, the deposited films demonstrated exceptional step coverage of 95% within a trench structure with an aspect ratio of ~1.5 and a bottom width of 265 nm. Post-annealing studies revealed that the films maintained their thermal and crystallographic stability between 500 °C and 800 °C. Additionally, the YC<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> films effectively functioned as a dual diffusion barrier for Cu and Ru (40 nm), exhibiting thermal stability up to 900 °C. These results underscore the potential of YC<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> films for applications in advanced semiconductor technologies.