Plasma Enhanced Atomic Layer Deposited Ru for MIMCAP Applications

A comparative study of the growth behavior of nm-thin ruthenium layers by plasma enhanced atomic layer deposition using two ruthenium precursors is discussed. For bis(ethylcyclopentadienyl)-ruthenium or Ru(EtCp)2, we have found a large incubation time on titanium nitride when using N2/NH3 plasma. With N2/H2 plasma the incubation was significantly reduced. For (methylcyclopentadienyl-pyrrolyl)ruthenium or MCPRu, no incubation was observed for either plasmas. The measured growth per cycle was ~ 0.02 nm for Ru(EtCp)2 whereas ~ 0.04 nm for MCPRu. The top surface of the PE-ALD Ru films can be oxidized without surface roughening by applying a low pressure O2 anneal, while O3 exposure leads to roughening due to etching and re-deposition downstream of etched Ru. Awareness of the impact of oxidizing ambients on Ru is essential for successful integration of Ru layers as electrode in metal-insulator-metal capacitors.