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In this paper, silicon (Si) nanocrystal memory using chemical vapor deposition (CVD) HfO2 high-k dielectrics to replace the traditional SiO2 tunneling/control dielectrics has been fabricated and characterized for the first time. The advantages of this approach for improved nanocrystal memory operation have also been studied theoretically. Results show that due to its unique band asymmetry in programming and retention mode, the use of high-k dielectric on Si offers lower electron barrier height at dielectric/Si interface and larger physical thickness, resulting in a much higher Jg,programming/Jg,retention ratio than that in SiO2 and therefore faster programming and longer retention. The fabricated device with CVD HfO2 shows excellent programming efficiency and data-retention characteristics, thanks to the combination of a lower electron barrier height and a larger physical thickness of HfO2 as compared with SiO2 of the same electrical oxide thickness (EOT). It also shows clear single-electron charging effect at room temperature and superior data endurance up to 106 write/erase cycles.
Date of Publication: Oct. 2003