Thin Hf0.6Si0.4Ox and Hf0.3Al0.7Ox films fabricated by metal-organic chemical-vapor deposition and atomic-layer-deposition techniques were characterized using monoenergetic positron beams. Measurements of the Doppler broadening spectra of annihilation radiation and the lifetime spectra of positions indicated that positrons annihilated from the trapped state by open volumes that exist intrinsically in amorphous structures of the films. For HfSiOx, the mean size of the open volumes and their size distribution decreased with increasing postdeposition annealing (PDA) temperature. For HfAlOx, although the overall behavior of the open volumes in response to annealing was similar to that for HfSiOx, PDA caused a separation of the mean size of the open volumes. When this separation occurred, the value of the line-shape parameter S increased, suggesting an oxygen deficiency in the amorphous matrix. This fragmentation of the amorphous matrix can be suppressed by decreasing the annealing time.

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The effects of nitridation on open volumes in thin HfSiOx films fabricated by metal-organic chemical vapor deposition were studied using monoenergetic positron beams. It was found that positrons were annihilated from the trapped state by open volumes that exist intrinsically in amorphous HfSiOx structures. In an as-deposited film, the positrons were annihilated from two different types of open volume. After plasma nitridation, the probability of positrons trapped by larger open volumes decreased, which is attributed to nitride trapped by such regions. The mean size of the open volumes increased after annealing, suggesting expansion of the open volumes due to the incorporation of nitride into the HfSiOx matrix.

Open volumes in strained SiN films deposited on Si substrates by microwave plasma enhanced chemical vapor deposition were probed using monoenergetic positron beams. Positrons were found to annihilate from the trapped state by open volumes which exist intrinsically in amorphous structures of SiN. The formation of positronium atoms in large open volumes was observed. From their lifetimes, the estimated mean size of such volumes was 0.02–0.5nm3. A clear correlation between the size distribution of open volumes and the stress in the substrate was obtained. The relationship between the open volumes and impurities in the films is also discussed.

Vacancy-impurity complexes in polycrystalline Si (poly-Si) used as a gate electrode of the metal-oxide-semiconductor field-effect transistor (MOSFET) were probed using monoenergetic positron beams. Doppler broadening spectra of the annihilation radiation and the positron lifetimes were measured for poly-Si(150nm)∕HfSiON(5nm)∕Si. In addition, first principles calculations were used to identify impurities coupled with defects in the poly-Si film. The major defect species in the poly-Si film was identified as vacancy-type defects; their mean open volume was close to that of a divacancy. Vacancy-oxygen complexes were observed in the P-implanted poly-Si film after annealing (at 1000°C); the number of oxygen atoms coupled with each defect was estimated to be one or two. For the B-implanted poly-Si film, however, the formation of the complexes was suppressed, suggesting the formation of oxygen clusters or precipitate. We discuss the interaction between such oxygen-related defects and boron in terms of the electric properties of p-channel MOSFETs.

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