The role of nanoclusters in reducing hole trapping in ion implanted oxides

At the 2000 IEEE Nuclear and Space Radiation Effects Conference, it was shown that the negative shift in flatband voltage that results from hole injection is reduced in oxides that have been implanted with large doses of Al, Si, or P ions. In the present paper, we study the basic mechanism responsible for this reduced shift in the flatband voltage in more detail by comparing electron and hole trapping in Si and Ar implanted oxides. We find that in Si implanted oxides, the reduction in the shift of the flatband voltage is accompanied by the formation of entities in the oxide that have a large electron capture cross section, and that can become positively charged by photoemitting electrons. Photoluminescence studies indicate that these entities are Si nanoclusters. Oxides implanted with large doses of Ar do not form clusters, and these oxides show neither a reduction in the shift of the flatband voltage nor the formation of large capture cross-section electron traps. We show evidence that the nanoclusters reduce the shift of the flatband voltage by trapping protons formed during hole injection.