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.
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