Matthias Böhringer

In noncontact charge-carrier lifetime techniques based on surface photovoltage measurements, uncontrolled surface recombination at the wafer back side may strongly interfere with carrier recombination in the silicon bulk for certain applications. An enhanced surface recombination rate decreases the sensitivity to metallic impurities in the bulk and may furthermore result in misleading data. To circumvent this problem, we use dedicated monitor wafers with a high/low p+∕p0p+∕p0 -junction close to the rear surface, where an electrostatic potential barrier hinders excess minority carriers to recombine at the back side. The benefit of this concept in lifetime measurements employing open-circuit photovoltage decay is demonstrated for the routine supervision of oxidation furnaces and implantation beam lines.