Evaluation of ZrO/sub 2/ gate dielectrics for advanced CMOS devices

Abstract

We discuss modeling issues of ZrO/sub 2/ insulating layers fabricated by metal-organic chemical vapor deposition (MOCVD). Tunneling through such layers cannot be described within the established Tsu-Esaki model due to the presence of a strong trap-assisted tunneling component. Trap energy levels and. concentrations can be extracted from the time constants of the measured trap charging and discharging processes. A trap concentration of 4.5/spl times/10/sup 18/ cm/sup -3/ with a trap energy level of 1.3 eV below the ZrO/sub 2/ conduction band edge was found for the considered layer. The parameters are used to simulate a 50 nm 'well-tempered' MOSFET and the influence of the high-/spl kappa/ dielectric on the threshold voltage was studied. Two counteracting effects are found: while the fringing fields from the drain contact reduce the threshold voltage, the presence of traps in the dielectric can lead to a strong increase of the threshold voltage.