Lifetime improvement in Czochralski-grown silicon wafers by the use of a two-step annealing

Minority-carrier lifetime improvement by a two-step annealing has been demonstrated using MOS capacitors fabricated on Czochralski-grown (CZ) silicon wafers. It is shown that an intrinsic gettering effect does not always follow a single annealing in an oxygen-free ambient, even in the wafers containing high oxygen content (∼1018 cm−3). This is probably because nuclei of precipitate-dislocation complexes (PDC) are two small in size to grow into PDC during a single annealing of recent high-grade CZ wafers. In the present study, an additional low-temperature annealing at 800 °C is performed in order to improve the situation. A few critical conditions to the effectiveness of the intrinsic gettering are discussed in connection with the crystalline quality of the wafer.