The Ultrahigh Vacuum Electron Cyclotron Resonance Chemical Vapor Deposition(UHV-ECRCVD) system whose base pressure is 1${ imes}10^{9}$ torr has been constructed. In-situ cleaning prior to the epitaxial growth was carried out at 56$0^{circ}C$ by ECR generated uniform hydrogen plasma whose density is $10^{10}/cm{3}$. The natural oxide was effectively removed without damage by applying positive DC bias(+10V) to the substrate. RHEED(Reflection High Energy Electron Diffraction) analysis has been used to confirm the removal of the surgace oxide and the streaky 2$ imes$1 reconstruction of the Si surface, and the suppression of the substrate damage is anaylized by X-TEM(cross-sectional Transmission Electron Microscopy). Surface cleaning technique by ECR hydrogen plasma confirmed good quality epitaxial growth at low temperature.