Electron trapping probabilities in hydrogen ion implanted silicon dioxide films thermally grown on polycrystalline silicon

Abstract

Fowler–Nordheim tunneling currents in hydrogen ion implanted and as-grown SiO2 films, thermally grown on polycrystalline silicon(polysilicon), have been investigated. The ion implantation is performed through the SiO2 films for hydrogenation of the grain boundary states in the polysilicon layer on which the SiO2 is grown. A model of Groeseneken and Maes is used to include in the calculations the field enhancement caused by asperities at the SiO2–polysilicon interface. The oxide field reduction, caused by electron capture in initially neutral electron traps into the SiO2, is also modeled. Electron trapping probabilities, defined as the product of the bulk electron trap density in SiO2 and the electron capture cross section of the traps are determined in both as-grown and hydrogen ion implanted oxides. In the hydrogen ion implanted oxides electron trapping probabilities higher than three orders of magnitude are obtained. Native electron traps in the as-grown oxides with capture cross section of the order of 10−20cm2, as well as ion implantation generated electron traps with capture cross section of the order of 10−18cm2 are deduced from the calculated trapping probabilities.