Mechanism of Defect Formation during Low-Temperature Si Epitaxy on Clean Si Substrate

Defects having a mound structure are formed during Si epitaxy on (001) Si substrates by low-pressure chemical vapor deposition at a low temperature of 700°C under the condition of high deposition pressure, even if the surface is atomically clean. The structure of the mound was a quadrangular pyramid, in which high-density {111} twins exist. The formation of such defects is due to the high pressure of SiH 4 and H 2 . Epitaxial growth with high perfection is suppressed by the high pressure of the H 2 ambient, because hydrogen suppresses both the decomposition of SiH 4 and the migration of atoms on the surface. However, at the same time, a growth front that can realize the high deposition rate is preferred under the condition of high SiH 4 pressure. Crystalline structure with {111} twins is favorable for attaining the high growth rate because terraces and steps are formed at the growth front. Thus mounds are formed due to the higher deposition rate on the edge of {111} twins than that on the (001) plane.