The effect of NH4OH concentration on surface qualities, namely, haze level, roughness, and number of remaining particles after final-touch polishing, of silicon wafers was investigated. This investigation found that the surface qualities of the final touch polished silicon wafers were degraded by the agglomeration of colloidal silica abrasives and a weakly formed passivation layer on the silicon-wafer surface at lower NH4OH concentration and enhanced with increasing NH4OH concentration in alkaline slurry. These results were confirmed by measuring the secondary-abrasive size, zeta potential of the colloidal silica abrasive in the slurry, and X-ray photoelectron spectroscopy on the silicon-wafer surface. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3571006] All rights reserved.