Thickness Dependence of Furnace N2O-Oxynitridation Effects on Breakdown of Thermal Oxides

Toshimasa MATSUOKA  Shigenari TAGUCHI  Kenji TANIGUCHI  Chihiro HAMAGUCHI  Seizo KAKIMOTO  Junkou TAKAGI  

IEICE TRANSACTIONS on Electronics   Vol.E78-C   No.3   pp.248-254
Publication Date: 1995/03/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Sub-1/4 Micron Device and Process Technologies)
N2O-oxynitridation,  charge-to-breakdown,  thin dielectrics,  MOS structure,  dielectric reliability,  

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Thickness dependence of breakdown properties in control and N2O-Oxynitrided oxides was investigated. Nitrogen atoms piled up at the Si/SiO2 interface increase charge-to-breakdown (QBD) under substrate injection conditions for oxide thickness below 10 nm, while no meaningful improvement is observed above 10 nm. This thickness dependence is explained by the fact that N2O-oxynitridation reduces oxide defects near the Si/SiO2 interface. N2O-oxynitridation of the oxides reduces the number of neutral electron traps due to the chemical reaction of oxide defect with nitrogen atoms. Electron trapping of N2O-oxynitrided oxides is significantly suppressed; the reduction of electron trapping events into neutral electron traps increases QBD under substrate injection. On the other hand, under gate injection, N2O-oxynitrided oxides show low rate of hole trapping during the initial stress period. However, in heavily injected condition, electron trapping is not suppressed, resulting in little improvement of QBD. In addition, the control and N2O-oxynitrided oxides show quite similar dependence of QBD on stress current density, which is related primarily to the carrier transport phenomena (tunneling, traveling, impact ionization and hole injection).