We investigated the effect of hydroxyethyl cellulose (HEC) concentration in the alkaline slurry on the surface qualities of polished silicon wafers after touch polishing, such as the number of remaining particles and the haze level. They significantly decreased and saturated over the addition of a 0.2 wt % HEC. We attributed these surface quality enhancements to a formation of nanometer-sized passivation layers onto the silicon wafer and colloidal silica surfaces during touch polishing. The formation of passivation layers were shown by the results of investigations with an average particle size, the zeta potential of abrasives, the contact angle, and X-ray photoelectron spectroscopy measurements.