SURFACE-STRUCTURES AND GROWTH MODES FOR CU ON SI(100), SI(110) AND SI(111) SURFACES DEPENDING ON CU SEGREGATION BY HEAT-TREATMENT

Cu has a large diffusion coefficient in Si, like Ni, and hence the dep osited Cu atoms on the Si clean surfaces diffuse into the bulk with in creasing temperature and segregate to the surface by quenching. Thus, the surface reconstructed structure changes by heat treatment dependin g on the surface Cu concentration induced by heat treatment. Moreover, the quantity of Cu segregation decreases with increasing annealing ti me, because the diffused Cu atoms are trapped to islands on the surfac e while annealing. The quantity of diffusing Cu atoms into the bulk an d the desorption temperatures of Cu from the reconstructed surfaces de pend on the crystallographic orientations of the substrate surface. Di fferent cohesive energies of the surface superstructures and different temperatures of the Cu segregation depending on surface orientations are discussed based on the structures on Cu-Si layers formed on the Si (100), (110) and (111) surfaces.