Vacuum-evaporated iron caused a severe degradation in minority carrier lifetime irrespective of the cleans used indicating lifetime degradation is related to initial iron concentration, not merely to final iron concentration after cleaning. It was found to take at least three separate steps (within the RCA-based cleans) to effectively remove iron from hydrofluoric acid solution-last surfaces. It also was found that precipitates caused by iron contamination were formed underneath thermally grown silicon oxide at 920 degrees C. The defects are believed to be iron silicides formed during the oxidation of iron-contaminated silicon.