So-called flow pattern defects in p-type (100) Czochralski wafers were characterized by using non-agitated Secco etching. It was observed that the removal rate of Si increased with increasing density of flow pattern defects. Because of the electrochemical nature of the etching process, the flow pattern defects could act as electrically active centers which facilitated H gas bubble evolution and agitation of the etching solution. Annealing at temperatures above 1000C caused a reduction in the flow pattern defect density with a uniform depth distribution within the sub-surface region. It was concluded that the dissolution kinetics of the flow pattern defects could differ from those of oxide precipitates during formation of the defect-free zone.

W.Wijaranakula: Journal of the Electrochemical Society, 1994, 141[11], 3273-7