High temperature annealing behavior of electron traps in thermal SiO2

The effect of high temperature post oxidation annealing on deep and shallow electron traps in thermally grown SiO2 on silicon was studied using the avalanche injection method. N2 or Ar anneal leads to removal of water related traps; some of the 5 × 10−19 cm2 deep centers persist during this treatment and shallow traps with cross sections in the 10−16 and 10−15 cm2 ranges are generated. These same deep and shallow traps are found on samples with poly Si gate which have been subjected to a high temperature post deposition anneal. Upon filling the shallow traps at 100 K part of the charge is being transferred to the 5 × 10−19 cm2 trap at this temperature. The observed behavior suggests that at least a substantial fraction of these traps are levels belonging to the same defect center. A brief O2 anneal at high temperature suffices to considerably reduce the density of the 5 × 10−19 cm2 deep and the shallow centers. It is proposed that the traps are caused by oxygen deficiency of the SiO2 and are O3Si· ·SiO3 and/or single O3Si· centers. Additional centers (O3SiO· ·SiO3; O3SiO· and O3Si·) may result from the split off of water from the oxide.