The dependence of room-temperature oxidation of silicon catalyzed by Cu3Si on silicide thickness, silicide grain size and the substrate orientation has been investigated by transmission electron microscopy (TEM), X-ray diffractometry and Auger electron spectroscopy. The extent of oxidation was found to depend critically on the starting film thickness of Cu3Si. The oxidation was found to be more restricted on (111)Si than that in (001)Si samples. The SiO2 layer thickness was found to decrease with the average grain size of the starting Cu3Si layer. High-resolution TEM revealed that the oxidation is initiated at the grain boundaries. An oxide film as thick as 4.5 mu m was grown at room temperature over a period of two weeks in (001) samples. The growth of the thick oxide film was achieved by minimizing the grain size of Cu3Si through a reaction between Cu and an intermediate amorphous silicon layer at 200 degrees C. Mechanisms for catalytic oxidation of silicon in the presence of Cu3Si are discussed.