Nondestructive Observations of Surface Flaws and Contaminations in Silicon Wafers by Means of a Scanning Photon Microscope

Abstract
A scanning photon microscope based on ac surface photovoltage imaging was applied for nondestructive observations of surface scratches and surface contaminations by SO4 2- in 125 mm diameter n-type silicon wafers. The scratches and contaminations create bulky and interface traps, resulting in lower ac surface photovoltages. The ac surface photovoltages attained between 35 through 150 µV have a relationship with the concentration of SO4 2- analyzed by ion chromatography ranging between 102 and 2×104 ng/wafer, implying that the present method is useful and simple for evaluation of the contaminated level of wafer surfaces in a nondestructive and noncontact manner.