The correlation between gate oxide integrity, photoconductivity amplitude and surface microroughness was systematically measured with 9 SC1 cleanings to remove residual subsurface damage induced by mirror polishing on the subsurface of silicon wafers. The same measurements were also carried out for as-epitaxial wafers as a comparison. Measured gate oxide integrity and photoconductivity amplitude in polished wafers increased with increase in the number of cleaning times and saturated after 3 cleanings, however, those for the epitaxial wafers did not vary throughout the 9 cleanings. Surface microroughness increased continuously throughout the 9 cleanings for both wafers. The 3 SC1 cleanings did remove the damage layer whose thickness was determined to be 21nm, and the photoconductivity amplitude well reflected the removal of this damage and the behavior of the gate oxide integrity. The images of the polished epitaxial wafers observed by the optical shallow defect analyzer showed many scratches which disappeared after 3 SC1 cleanings. This result gave direct evidence of the existence of residual damage and the behavior of photoconductivity amplitude and gate oxide integrity when the damage was removed.