A fast, preparation-free method to detect iron in silicon

Abstract

Iron is one of the most important impurities in silicon integrated-circuit technology. We present a fast (5 min), essentially preparation-free large-area (25 cm2 ) technique to determine the Fe concentration in boron-doped silicon with a sensitivity of 2–5×1011 cm−3. The principle of the method is based on the fact that interstitially dissolved Fe undergoes a reversible pairing reaction with boron and that the minority-carrier diffusion length—as measured by the surface photovoltage method—is modified by this reaction. The method has been calibrated by deep-level transient spectroscopy and is also suitable to measure a surface Fe contamination in combination with a rapid thermal annealing diffusion step.