Fluorination of aluminum oxide gate dielectrics using fluorine neutral/ion beams

The effect of the fluorination of aluminum oxide (Al2O3) in an oxide-nitride-aluminum oxide (SiO2-Si3N4-Al2O3, ONA) layer through fluorine (F) ion and neutral-beam treatments on the characteristics of the ONA layer was investigated to study the effect of charge-related damage during F ion beam treatment. The treatment with an F beam at approximately 10 eV energy produced an about-5-nm-thick fluorinated alumina layer by replacing the aluminum-oxygn (Al-O) bonding with Al-F bonding for both the F neutral-beam and F ion beam treatments. Moreover, no significant differences in the physical and chemical properties of the ONA layers treated with the two beams were observed. When the electrical characteristics of the metal-oxide-semiconductor (MOS) devices were compared, however, the lowest leakage current and highest memory window characteristics were observed in the MOS device fabricated with an F neutral beam, due to the Al-F layer formed on the Al2O3 surface. In the case of the MOS device fabricated with the F-ion-beam-treated ONA layer, however, lower electrical characteristics were observed compared to the MOS device fabricated with the F-neutral-beam-treated ONA layer, possibly due to the charge-related damage that occurred during the F ion beam treatment, even though the memory characteristics were improved compared to the reference due to the Al-F layer formed on the Al2O3 surface.