Plasma Enhanced Atomic Layer Deposited Ruthenium 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 N-2/NH3 plasma. With N-2/H-2 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 similar to 0.02 nm for Ru(EtCp)(2) whereas similar to 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 O-2 anneal, while O-3 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.