Characterization of Hf0.3Al0.7Ox fabricated by atomic-layer-deposition technique using monoenergetic positron beams

Thin Hf0.3Al0.7Ox films fabricated by an atomic-layer-deposition technique were characterized using monoenergetic positron beams. From the measurements of the Doppler broadening spectra of annihilation radiation and the lifetime spectra of positrons for 3- and 7-nm-thick HfAlOx films deposited on SiON(0.9 nm)/Si, it was found that positrons in the HfAlOx films annihilate from the trapped state by open spaces that exist intrinsically in their amorphous structure. The line-shape parameter S and the positron lifetime corresponding to the HfAlOx films decreased with increasing oxygen content (0.004–1%) in the annealing atmosphere. This fact was attributed to the shrinkage of the open spaces due to the change in the matrix structure of amorphous HfAlOx. The increase in oxygen content was also found to decrease the transient current of n+-polycrystalline-Si/HfAlOx/SiON/Si. The decrease in the mean size of the open spaces and the resultant hardening of the matrix structure are considered to suppress the dielectric polarization of HfAlOx.