[cis-(1,3-diene) _2W(CO) _2] complexes as MOCVD precursors for the deposition of thin tungsten - Tungsten carbide films

摘要

Tungsten - tungsten carbide thin films are deposited by metal-organic (MO)CVD on silica-coated silicon wafers using [cis-(1,3-butadiene) _2W(CO) _2] and [cis-(1,3-cyclohexadiene) _2W(CO) _2], respectively, as tunable precursor complexes. The compounds are prepared through photochemical ligand exchange reactions from [W(CO) _6] and fully characterized, including X-ray structure determination and detailed differential thermal analysis (DTA)/thermogravimetry (TG) investigations. Gas-phase diffusion coefficients and the vapor pressure of the compounds are calculated. The MOCVD experiments are performed in a vertical cold-wall reactor and the exhaust gas is analyzed by gas chromatography (GC). X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM) measurements are utilized for film characterization. Consequences of the high oxophilicity of freshly formed tungsten surfaces, consecutive surface reactions of the complex ligands, film growth, and film properties are discussed. Inside the layers, tungsten carbide is identified as the main component.