We present a new approach to measuring mobile charge in SiO2 without MOS test structures. The measurement is done in non-contact mode and offers a whole-wafer mapping capability of the mobile charge in single minutes. Determination of the mobile charge is based on monitoring the ion drift by measuring corresponding changes in the oxide voltage. The drift is induced on the whole wafer by corona charge deposited on SiO2 followed by 200°C annealing. Surface contamination is distinguished from bulk contamination by selecting the appropriate sequence of the corona-temperature-stress, which injects ions from the surface into the SiO2.