MICROSTRUCTURE, ELECTRICAL-PROPERTIES AND PASSIVATION OF DEFECTS AT THE SILICON-SILICON-DIOXIDE INTERFACE

Thermal oxidation is performed in a copper-contaminated ambient on Czo chralski and float-zone silicon, and on samples with damaged and undam aged surfaces, in order to evaluate the role of oxygen supersaturation in the starting material and the influence of formation of oxidation- induced stacking faults on the microstructure and electrical propertie s of the Si/SiO2 interface underlayers. The microstructure is controll ed using transmission electron microscopy and secondary ion mass spect rometry, and the minority carrier diffusion length is analyzed by the electron beam-induced current technique. It is shown that the thermal oxidation of Czochralski silicon induces the precipitation of large co pper colonies associated with oxidation stacking faults decorated with oxygen at the Si/SiO2 interface. In float-zone silicon the oxidation stacking faults are themselves nucleation sites of copper precipitates . When there is no oxidation stacking fault formation (undamaged initi al surface), copper precipitation may occur on dislocation nets. The e xtended defects are highly recombinant when they are associated to cop per precipitates. The diffusion length is decreased in regions free of copper colonies-which indicates the growth of point-like defects duri ng the thermal process-and partially restored by hydrogenation treatme nt.