ELECTRON TRAP GENERATION IN THERMALLY GROWN SIO2 UNDER FOWLER-NORDHEIM STRESS

Electron trap generation in thermally grown silicon dioxide (SiO2) during Fowler-Nordheim (FN) stress is investigated by using an aluminium-gated capacitor structure. The generated electron traps are characterized by the avalanche electron injection technique. The experimental results support the model that electron trapping in oxide follows the first-order kinetics and may have multiple-capture cross sections. It is found that both donorlike (positive charge related) and acceptorlike (neutral before capturing electron) traps are generated and they behave differently. The donorlike trap is not stable at or above room temperature and its effective density saturates as the stressing time increases, while the opposite is true for the acceptorlike trap. The electron-capture cross section of donorlike trap spreads from 10(-18) to over 10(-14) cm2, but the capture cross section of the generated acceptorlike trap is limited in the range of (4.5-9) x 10(-17) cm2. The acceptorlike trap is generated by the interaction between free holes and SiO2 and hole trapping leads to donorlike traps. The relation between the generated trap and the as-grown trap will be discussed. Comparison of the electron traps generated by FN stress with those by irradiation and hot hole injection indicates that the electron trap generation under these different stressing conditions is controlled by the same mechanism. The necessary condition for electron trap generation is the presence of holes in the oxide, rather than a high electrical field.