CVD Copper Deposition from CuI(HFAC)TMVS Studied Through a Modeling Experimental Design

Thin copper films were grown using hexafluoroacetylacetonato-copper(I) trimethylvinylsilane [Cu(hfac)tmvs].This precursor was delivered through a bubbler using hydrogen as carrier gas. Water vapour was used as reactant. The films were deposited on sputtered titanium nitride substrate, at wafer temperatures between 100°C and 210°C. An excess of water leads to the formation of copper oxide and films with a high resistivity. But no water leads to a poor nucleation and very low deposition rate. The way of injecting water plays an important role in the process: water at the beginning of the deposition time helps the nucleation and has to be stopped after a few minutes to avoid the oxidation of the film. An optimization of the operating conditions was carried out through the use of screening and modeling experimental designs. The influence of substrate temperature, carrier gas flow, water flow, water injection time and bubbler pressure was studied and leads to experimental laws, which are showing the dependence of the resistivity and the deposition rate with any of these parameters. An optimum working point was found, in term of resistivity. In that case, X-Ray Photoelectron Spectroscopy (XPS) indicate a pure copper phase. The resistivity was 1.9 μω.cm after annealling. The adhesion on TiN substrate is excellent according to the scotch tape test. Very high conformal deposition is obtained on 0,4 μm width, 1 μm deep.