Iron-rich particles in heavily contaminated multicrystalline silicon wafers and their response to phosphorus gettering

Heavily contaminated multicrystalline silicon wafers have been studied using a scanning synchrotron x-ray fluorescence micro-probe, revealing the presence of iron-rich particles located along grain boundaries. These particles were found to be partially dissolved and removed during phosphorus gettering treatments at 900 or 1000°C for times of up to 100 min, with increased gettering efficiency at higher temperatures and times. Annealing without the phosphorus gettering layer present at the wafer surfaces resulted in no discernible reduction in particle coverage, showing that the gettering layer is essential in such heavily contaminated wafers, in order to reduce the dissolved Fe concentration below the solubility limit, and therefore allow dissolution to proceed.