3C-SiC thin films were grown on Si(111) substrates at 1250 degrees C by horizontal low pressure chemical vapor deposition (LPCVD). We performed an exhaustive study on the effect of H-2 flow rate on the crystalline quality, surface morphologies, growth rate, n-type doping of 3C-SiC thin films and the voids at the interface. The films show epitaxial nature with high crystal quality and surface morphology increase obviously with increasing H-2 flow rate. The growth rate and n-type doping are also dependent on H-2 flow rate. The properties of the voids at the interface are discussed based on the cross-sectional scanning electron microscope characterization. Transformation of voids with increasing H-2 flow rate are attributed to higher 3C-SiC film growth rate and H-2 etching rate. The mechanism of void formation is discussed based on our model, too. The results demonstrate that H-2 flow rate plays a very important role in the heteroepitaxial growth of 3C-SiC films. (C) 2015 Elsevier B.V. All rights reserved.