The neutralization of Na+ ions in HCl grown SiO2

Experiments have been done to measure the trapping and neutralization kinetics of sodium ions in Al-SiO2-Si structures using oxides grown with HCl-Ar/O mixtures. The trapping of sodium at the Si-SiO2 interface was quantified by thermally stimulated ionic current (TSIC) measurements made at negative applied electric fields following positive bias temperature stress. There were three distinct types of behavior depending on the chlorine content of the oxide. For chlorine contents ≳3.0×1015 atoms cm−2 the TSIC results showed two sodium peaks, with maxima at about 0.8 and 1.5 eV, corresponding to states at the Si-SiO2 interface in which the ions were on the whole charged and neutral, respectively. Complete neutralization of the sodium, and good stability with respect to detrapping from the Si-SiO2 interface under typical device operating conditions, was possible only in samples containing ≳3.0×1015 Cl atoms cm−2. A Schottky-type variation of the neutral peak trap energy with applied field was measured, with coefficient (19±1)×10−5 eV V−1/2 cm1/2. For chlorine contents in the range (0.9–2.8)×1015 cm−2 the TSIC spectra showed two overlapping peaks, with maxima at 0.8 and about 1.25 eV. In this case only part of the second peak at energies above 1.25 eV corresponded to ions which were completely neturalized. For chlorine contents <0.8×1015 cm−2, the TSIC spectra showed only one sodium peak, at about 0.8 eV, similar to that observed in dry-grown oxides which do not contain chlorine. It was found that a fraction of the ions, about 20%, were neutralized even in dry-grown oxides. The amount of sodium neutralization was measured as a function of time and temperature of positive-bias stress, magnitude of applied electric field, and oxide chlorine content. A method was used which separated the rate of neutralization at the Si-SiO2 interface from the overall process. For samples with chlorine content ≳3.0×1015 cm−2, the time dependence of the interfacial neutralization process was consistent with a model in which lateral diffusion of sodium, to chlorine-containing ’’islands’’ at the Si-SiO2 interface, is the rate-limiting process. The activation energy of the interfacial neutralization process, (0.87±0.15)eV, is in agreement with that of lateral diffusion, (0.8±0.2)eV.

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The neutralization of Na+ ions in HCl grown SiO2

Cited by 3 publications

References 3 publications

The effect of Ti and Ti/Au metallisation on mobile charge in HCl grown oxides

The effect of Ti and Ti/Au metallisation on mobile charge in HCl grown oxides

Characterization of Dielectric Films

Sodium passivation in Al-SiO2-Si structures containing chlorine

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