NONDESTRUCTIVE CHARACTERIZATION OF SURFACE CONTAMINANTS IN SILICON-WAFERS USING AC SURFACE PHOTOVOLTAGE METHOD

A scanning photon microscope (SPM), based on the imaging of ac surface photovoltages (SPVs), has been developed and used for nondestructive detection of impurities in silicon (Si) wafer surfaces rinsed with various solutions. When aluminum (Al), iron (Fe) and copper ate incorporated into native oxide on Si surfaces, they induce a negative charge by forming a network of (AIOSi)(-) or (FeOSi)(-). For n-type Si, this negative charge gives rise to an appreciable ac SPV, while a positive charge due to phosphorus in the form of (POSi)(+) causes an ac SPV in p-type Si. Thus, once contaminated ions are known on the basis of chemical analysis, the resulting ac SPV features can provide nondestructive information on the content and distribution of the contaminants on the Si wafer surfaces. This is what we demonstrate in the present paper.