Non-intrusive mapping of subsurface defects in semiconductors

We have adapted differential interference contrast Nomarski microscopy in the transmission configuration to the problem of mapping subsurface defects in semiconductors. We have demonstrated the ability to rapidly measure the depth of the precipitate-free-zone in silicon with a reproducibility of ±1 m in whole Si wafers up to 200 nm in diameter, having an extrinsic doping concentration up to 7×10¹⁹ cm^–3 and a nominal, as received, back side roughness. Because our subsurface defect profiler is completely non-destructive, product wafers can be inspected at various stages of processing and immediately returned to the production line.