HIGH-ACCURACY X-RAY REFLECTIVITY STUDY OF NATIVE-OXIDE FORMED IN CHEMICAL TREATMENT

High-accuracy X-ray reflectivity measurements using synchrotron radiation have been carried out to study native oxides formed during various chemical-cleaning processes on Si wafer. Clear differences in the density of native oxides between various chemical treatments were obtained from the normalized reflectivity for the first time. Native oxides formed by HCl and NH4OH solutions have a low density, in contrast to the oxides formed by H2SO4 solution and UV/O-3 whose densities are close to that of thermal oxide. These results are closely related to the results of chemical studies and the etching characterization of native oxides.