Plasma-Enhanced Atomic Layer Deposition of TiN Thin Films Using Ultralow Electron Temperature Plasma

Ultralow electron temperature (ULET, Te < 0.5 eV) plasmas are applied to atomic layer deposition (ALD) for damage-free plasma processing. The effects of ULET plasma on the ALD of titanium nitride (TiN) thin films are investigated. The ULET plasma-enhanced ALD (ULET-PEALD) reduces TiN surface roughness by 60%, from 0.78 to 0.3 nm, compared to remote PEALD, and decreases resistivity from 430 μΩ·cm to 325 μΩ·cm, while improving crystallinity. Unlike remote plasma sources, ULET plasma causes less surface damage due to its lower ion energy, enabling low-energy ion surface treatment. The generation mechanism of ULET plasma and the ULET-PEALD process are explained in detail, along with an analysis of the deposited films. ULET plasmas offer great potential for applications in processes that were previously limited by concerns over plasma-induced damage.