An undercoat layer is used between a transparent conductive oxide and a glass substrate in thin film solar cells and low-emissivity windows. The focus of this work was to compare silicon oxynitride and silicon oxycarbide processes to deposit a single undercoat layer for fluorine-doped tin oxide. The coatings were made with atmospheric pressure chemical vapor deposition on soda-lime glass. Substrate temperatures were 590-630 degrees C as the process is intended for off-line coating application. The growth profile of silicon oxynitride and silicon oxycarbide was similar in both processes. It was shown that the growth rate can be controlled with different process parameters such as deposition temperature and silane concentration. Film composition and its optical properties depend on precursor feed ratios. Deposition temperature is expected to have more effect on the composition of silicon oxycarbide films. (C) 2012 Elsevier B.V. All rights reserved.