Low-pressure chemical vapor deposition of Cu on Ru using CuI as precursor

Low-pressure chemical vapor deposition (LPCVD) of Cu using copper(I)-iodide (CuI) as precursor was experimentally studied at low temperatures around 300 degrees C with understanding molecular structure of the precursor in the gas-phase. CuI was sublimated at temperatures around 300 degrees C in an evacuated reactor of LPCVD apparatus, while CuI was evaporated at high temperatures above 600 degrees C by atmospheric pressure CVD. Density functional theory (DFT) calculations supported CuI-trimer ((CuI)(3)) highly stabilized as an in-plane triangle is a major species in the gas phase and predicted the trimer is deformed by metal-atom such as Ru and Cu. Experimental results of the LPCVD, that preferentially oriented Cu(111) grains were deposited on Ru(001) at low temperatures around 300 degrees C but any deposits was not formed on SiOx/Si by the LPCVD, clearly indicating the activation energy of the precursor dissociation on the metal surfaces is lower than that on the dielectrics. Further, significantly low activation energy for the Cu-deposition rate dependent on the substrate temperature suggested the dissociation of the precursor is not driven by the thermal activation in the gas phase but by adsorption on the metal surfaces. Furthermore, the activation energy (85 kJ/mol) for the Cu-deposition rate dependent on the substrate temperature was found to be much lower than that for the dissociation of the CuI monomer (285 kJ/mol) or trimer (400 kJ/mol) in the gas phase. This finding indicates a catalytic dissociation of CuI on Ru and Cu metallic surfaces.