Alternative Organometallic Precursors for CVD of Tungsten

Abstract

ABSTRACTTwo solid, air stable, volatile tungsten complexes, tris(methylvinylketone) tungsten, I, and tris(butadiene)tungsten, II, have been investigated as precursors for chemical vapor deposition (CVD) of tungsten containing films. Thermal gravimetic analysis, (TGA), of I and II under argon showed the onset of decomposition at 140°C and 150°C, respectively. A rapid weight decrease corresponding to loss of all three ligands, methylvinyl ketone or butadiene, was observed.Tungsten film growth under hydrogen using I was investigated on Si, SiO2, Cu, TiN, Si, and Pt substrates. Selective tungsten film growth on platinum using a hydrogen carrier was observed at temperatures above 200°C. No appreciable tungsten deposition was observed on clean Si, SiO2. Cu or TiN surfaces below 400°C. No oxygen or carbon was detected in these films to the level of EDX analysis (∼1%) for depositions at 200°C. Increased growth temperatures resulted in increasing amounts of oxygen incorporation. The films grown at 200°C were smooth whereas cracking was observed in films grown at 300°C. The volatile products from the deposition were identified by a combination of gas chromatography and mass spectrometry. Small amounts of methylvinylketone. and methylethylketone were observed. Higher molecular weight species are as yet unidentified, but constituted the majority of the products.