GETTERING CHARACTERISTICS OF HEAVY-METAL IMPURITIES IN SILICON-WAFERSWITH POLYSILICON BACK SEAL AND INTERNAL GETTERING

The gettering behavior of polysilicon back seal (PBS) and internal get tering (IG) with isothermal annealing (600-1000 degrees C) was systema tically investigated for Fe contamination by deep level transient spec troscopy (DLTS). There was a clear dependence of the PBS gettering eff iciency on the PBS deposition temperature and on annealing temperature s used in the gettering processes. The use of lower deposition tempera tures and lower gettering temperatures resulted in a higher gettering efficiency. IG efficiency has a clear dependence on size and density o f the oxygen precipitate. In the case of a bulk micro defect (BMD) den sity of 10(5) cm(-2), it was necessary for the platelet oxygen precipi tate size to be larger than 200 nm, while a polyhedral oxygen precipit ate size of 100 nm was sufficient in obtaining IG effects for an Fe co ntamination level of 10(12) atoms/cm(3) The gettering efficiency has a clear correlation with the volume of the oxygen precipitates per unit volume of the silicon wafers. These results suggest that Fe atoms are gettered within the oxygen precipitates and not in the area surroundi ng them.