Si nanocrystal memory devices self-assembled by in situ rapid thermal annealing of ultrathin a -Si on SiO₂

Si-nanocrystal memories have been fabricated using the thermal agglomeration of an ultrathin (0.9-3.5 nm) amorphous Si (a -Si) film. The a -Si was deposited by electron beam evaporation followed by in situ annealing at 850°C for 5 min. Hemispherical nanocrystals were obtained with a dot density up to 3.9× 1011 cm-2, and a stored charge density of 4.1× 1012 cm-2 (electron + hole) was achieved. The data retention characteristics of nanocrystal-embedded devices have shown a 1 V memory window after 100 h. Well-separated Si nanocrystals with a 23-32% surface-coverage ratio have been successfully demonstrated. The process compatibility of the proposed technique was also discussed.