Spatially resolved lifetimes in EFG and String Ribbon silicon after gettering and hydrogenation steps

Lifetime improvement in EFG and String Ribbon silicon by gettering. or defect passivation has been investigated by photoconductance decay. But in contrast to former studies measurements. have been carried out in a spatially resolved way. In this way the mapping techniques have been found-to be indespensible for an accurate study of processing steps' impact on material quality. This is due, to very strong lifetime variations that have been measured throughout the wafer (between < 1 mus and > 300 mus), and because areas of the same starting quality have turned out to react very differently on applied processing steps. Consequently, the results of integral measurements strongly-depend on the nature of the areas incorporated in the specific sample. A statistical evaluation of the mapped lifetimes gives an impression of the uncertainties inherent to integral measurements.