Electron cyclotron resonance (ECR) hydrogen plasma was applied at 600 degrees C to in-situ clean the silicon surface of contaminants, such as oxygen and carbon species for subsequent low-temperature epitaxial growth. The standard condition with in-situ hydrogen plasma cleaning at 600 degrees C has been optimized and process variables such as d.c, bias, cleaning time, microwave power, and cleaning gas pressure were varied with respect to the standard condition. The epitaxial films, which were deposited in our chemical vapor deposition systems, immediately after these in-situ cleaning processes were characterized by cross-sectional transmission electron microscopy, etc. The role of a hydrogen ion in in-situ cleaning was clarified by investigating cleaning efficiencies for a variety of conditions. The hydrogen ion, which was produced by ECR plasma excitement, played a crucial role in removing surface contaminants in low-temperature (600 degrees C) in-situ ECR plasma cleaning processes.