Redistribution of recombination active defects and trapping effects in multicrystalline silicon after wet thermal oxidation

In this work we characterised recombination active defects in standard multicrystalline silicon block material by investigating the effect of a wet thermal oxidation step at 800 degC with fast temperature ramps on the effective lifetimes measured by the CDI and QSSPC methods. The average lifetime was significantly decreased by the oxidation step. An increase in the concentration of interstitial iron as well as an increase in the concentration of trapping centres after the oxidation step was observed. A detailed investigation revealed an increase in the recombination activity of grain boundaries. Modeling of measured carrier density profiles indicates that iron dissolves from precipitates in grain boundaries and diffuses into the grains during the process. It was found that iron represents a major part of the active defect concentration in the investigated multicrystalline material after the applied oxidation process.