Preparation of Ru thin film layer on Si and TaN/Si as diffusion barrier by plasma enhanced atomic layer deposition

Abstract

The growth behavior of plasma enhanced atomic layer deposited (PEALD) ruthenium (Ru) thin film was systematically studied in the context of its application to a copper diffusion barrier. The Ru layer was grown on bare Si and a 30 nm bottom wide nano-patterned trench with an aspect ratio of 4. Bis(ethylcyclopentadienyl)ruthenium [Ru(EtCp) 2] was used as a precursor and NH 3 was used as a plasma enhanced reactant, respectively. To obtain optimal deposition conditions, a Ru thin film was grown on non-patterned bare Si and ALD grown TaN substrate. The process parameters were precisely controlled, resulting in a uniform Ru film layer at 8-inch full wafer scale with a growth temperature of 290 °C and 230 mTorr of working pressure. The experimental results showed typical ALD grown thin film characteristics with a linear relation between film thickness and number of cycles. The growth rate was saturated at 0.35 Å/cycle for TaN and 0.33 Å/cycle for Ru. Based on the optimal conditions obtained from the non-patterned wafer, Ru thin film was deposited on 30 nm bottom width nano-patterned Si and TaN/Si trench with an aspect ratio of 4 to investigate the conformity. The conformity was measured to be 0.86 on Si and 0.97 on the TaN/Si trench, which indicates excellent step coverage. The physical properties of the Ru/TaN bilayer studied by X-ray diffraction and transmission electron microscopy (TEM) showed that a dense amorphous phase Ru thin film layer was successfully grown using PEALD. Our study indicated that reliable self-limited ALD characteristics and excellent conformal deposition of the Ru/TaN bilayer on both bare substrate and the 30 nm wide nano-patterned trench.