Analysis on gate-oxide thickness dependence of hot-carrier-induced degradation in thin-gate oxide nMOSFET's

The analysis indicates that a thinner gate oxide nMOSFET shows smaller degradation. Mechanisms for the smaller degradation were analyzed using a simple degraded MOSFET model. It was found that the number of the generated interface states is defined uniquely by the amount of peak substrate current, independently from the gate-oxide thickness. The major cause of the smaller degradation in the thinner gate-oxide device is smaller mobility degradation due to the generated interface states. The degraded mobility was measured and formulated. The smaller mobility degradation is explained by the difference between the vertical electric field dependence of the Coulomb scattering term and that of the phonon term under the inversion condition. The effect of a larger channel conductance, due to the larger inversion charges for the thinner gate-oxide device, is the secondary cause for the smaller degradation.>