Substrate-related defects that affect MOS yield center around either bulk impurities and precipitates or surface contamination. Uncontrolled bulk defects can cause significant refresh or leakage problems, but it has been shown that with proper processing the defects can form the basis for internal gettering that improves production performance. Surface-related yield problems reflect a joint responsibility of the wafer producer and the user, since residues, particularly organics, may also cause device performance problems. Control of these problems requires a careful analysis of all chemicals used in processing and cleaning the wafer prior to oxidations.