Hole and electron trapping in ion implanted thermal oxides and SIMOX

Optically assisted methods of injecting either electrons or holes into SiO2 layers were used to determine the effect of ion implantation on charge tra pping in oxides, Dry-grown thermal oxides and the buried oxides of material grown by the SIMOX (separation by implantation of oxygen) process were stu died, Al, Si, and P ions were implanted into the oxides at doses of 1 x 10( 13) to 1 x 10(16) and the oxides were annealed at 700, 900, or 1050 degrees C after implantation. High dose implantations were found to create electron traps having high capture cross sections, the density of which depends on the implant species, suggesting that electron trapping is related to chemic al aspects of the implanted ion, This was supported by measurements on an o xide implanted with a large dose of Ar, which showed no increase in electro n trapping, It was found that the shift in the flatband voltage resulting f rom hole trapping Could be reduced by high dose implantations, and that thi s effect is only weakly dependent on implant species. The hole trapping res ults are explained in terms of the effect of implantation on the oxide stru cture.