Scanning capacitance microscopy (SCM) is employed to study defect distribution induced by iron contamination on p-type silicon wafers. For slightly contaminated samples, SCM reveals that iron contamination induces interface traps in the defect region. Interface traps perturb significantly the depletion behavior of the silicon surface. Iron contamination also decreases the lifetime and increases the density of minority carriers in the defect region. The defects induced by iron contamination exhibit an obvious bias-dependent SCM contrast. By differential capacitance images, one can examine the defect density distribution. The influence of these microscale defects on the electrical characteristics of the metal oxide semiconductor (MOS) capacitor cannot be observed by conventional capacitance-voltage measurement. (C) 2002 The Electrochemical Society.