Thermal and MS studies of silver(I) 2,2-dimethylbutyrate complexes with tertiary phosphines and their application for CVD of silver films

Abstract

[Ag2(CH3CH2C(CH3)2COO)2] (1), [Ag2(CH3CH2C(CH3)2COO)2(PMe3)2] (2) and [Ag2(CH3CH2C(CH3)2COO)2(PEt3)2] (3) were prepared and characterized by MS-EI; 1H, 13C, 31P NMR, variable temperature IR (VT-IR) spectroscopy and thermal analysis. MS and VT-IR data analysis suggests bidentate bridging carboxylates and monodentately bonded phosphines in the solid phase. The same methods used for gas phase analysis of 1–2 proved [(CH3CH2C(CH3)2COO)Ag2]+ as the main ion, which could be transported in the gas phase during the CVD process. In the case of 3, similar intensity to the latter ion revealed [Ag{P(C2H5)}]+ and it is responsible for the CVD performance of 3. Thermal analysis results revealed that decomposition of 1–3 proceed in one endothermic process, with metallic silver formation between 197 and 220°C. In the case of 1, VT-IR studies of the gaseous decomposition products demonstrate the presence of ester molecules and CO2, whereas for 2 the main gaseous product appeared to be acid anhydride. Therefore, 2 was not used as a silver CVD precursor. Metallic layers were produced from 3 in hot-wall CVD experiments, (between 200 and 280°C), under a total reactor pressure of 2.0mbar, using argon as a carrier gas. Thin films deposited on Si(111) substrate were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Silver films obtained at moderate temperature (220–250°C) revealed a thickness below 50nm, and were whitish colored and slightly matt.