Interfacial reactions during sputter deposition of Ta and TaN films on organosilicate glass: XPS and TEM results

The evolution of the interface between organosilicate glass (OSG) and sputter deposited Ta or TaN films has been characterized by X-ray phototelectron spectroscopy (XPS). Cross-sectional TEM (XTEM) was also used to analyze Ta/OSG and TaN/OSG/interfaces for samples formed under different deposition conditions. XPS data show that Ta deposition onto OSG results in formation of an interphase between 1 and 2 nm thick composed of oxidized Ta and C. Metallic Ta is then formed on top of the interfacial region. In contrast, Ta-rich TaN formation occurs with some nitridation of the substrate, but with no significant interphase formation. The XPS data are consistent with the XTEM data. The XTEM results for Ta/OSG indicate a spatially irregular interface over a length scale of 2 nm, while results for TaN/OSG indicate a spatially abrupt region.