Oxide Charge Trapping Induced by Ion Implantation in SiO2

Experimental measurements directed at understanding oxide modifications induced by Na+ and Al ion implantation are described. Both implanted species created high dark conductivity in unannealed specimens. This had a temperature dependence independent of ion type suggesting that the conductivity is related to displacement damape. Internal photoemission studies showed that Na+ implantation had produced a barrier lowering at both interfaces and also permitted sub-threshold photoemission starting with photons of about 1 eV. Thermal annealing returned the oxide to its insulating state and removed the sub-threshold photoemission. Photo-depopulation measurements indicated that the oxide still contained electron traps not present in the unimplanted samples.