Improvements in minority carrier recombination lifetime in Czochralski (CZ) grown silicon wafers and the special problems of measuring such values are discussed. A further problems lies in tracking down the causes of the remaining limits to carrier lifetime. At the values of lifetime which will be required for future multimegabit applications, defect densities are in the 10 10 cm -3 range and below. This stretches the limits of current analytical techniques. New minority carrier lifetime analysis techniques have been developed which offer the potential of whole wafer spectroscopic images of bulk contamination in the sub-ppt range. These techniques can also be applied to a wide range of contamination problems in IC manufacturing.