Comparison among lifetime techniques for the detection of transition metal contamination

A systematic comparison among the most common methods (surface photovoltage (SPV), Elymat, and microwave-detected photoconductive decay (μ-PCD)) for lifetime measurements is presented. Though these techniques are very different from each other, we show that, where bulk-diffused impurities are concerned, they agree very well with each other, provided they are properly used. er to validate these techniques for the quantitative evaluation of bulk-diffused contaminants, iron and chromium implantations were carried out. An excellent correspondence was found between Elymat and μ-PCD data. In addition, the lifetime dependence on iron dose was studied and the expected behaviour was verified over two orders of magnitude. Elymat and μ-PCD measurements have also been applied to the study of contaminants segregated at wafer surface, such as nickel and copper. Both these techniques are very sensitive to surface-segregated metals, though under these conditions the correlation between Elymat and μ-PCD data is somewhat different with respect to samples with metals dissolved in the bulk. A measurement procedure is proposed in order to discriminate bulk and surface recombination.