Physical trends of High-k oxides

The properties of rare-earth and transition metal oxides of interest for the development of future silicon nanoelectronics will be reviewed. As an introduction, the motivation for using high-k insulators for MOSFET applications will be given together with a basic enlightenment on two crucial intrinsic properties of gate insulators: the dielectric constant, k, and the energy offset value, ∆E, in relation to silicon. It will be demonstrated how these quantities govern initial navigation along metals in the periodic system to find future oxide candidates with feasible leakage characteristics. An overview will be included on the restraining influence of lower-k interlayers, interface states and oxide traps together with a critical survey of existing characterization methods for crucial quantities. Chemical properties like reactivity, structural stability and hygroscopic qualities of interesting oxides will be treated together with reliability issues. Finally, the future challenge of keeping up gate insulator development with the perspectives of the ITRS roadmap will be discussed

Compensation effects at electron traps in semiconductors

The basic qualities for fulfilling the Meyer-Neldel rule (MNR) for thermal electron emission from semiconductor traps are investigated. A trap model including vibronic properties is used with varying entropy arising from the change in elasticity of the ionic part of the trap potential when an electron transition takes place. This gives rise to a system where the compensation effect originates from the increasing entropy change as a function of the enthalpy supply needed for the transition process in concord with Yelon-Movaghar theory. The entropy increase connects to a decrease in the activation energy for electron capture, which amplifies the compensation effect for MNR manifestation. By comparing with experimental data, the result achieved from the model clarifies the experimental observation of class partitioning for centers in GaAs, obeying the MNR. Furthermore, it is demonstrated that traps at metal-oxide-silicon interfaces, with the same properties as bulk traps following the MNR, give rise to capture cross-sections steeply increasing with the Gibbs free energy involved in carrier emission, as found by experiment

Physical trends of High-k oxides

The properties of rare-earth and transition metal oxides of interest for the development of future silicon nanoelectronics will be reviewed. As an introduction, the motivation for using high-k insulators for MOSFET applications will be given together with a basic enlightenment on two crucial intrinsic properties of gate insulators: the dielectric constant, k, and the energy offset value, ∆E, in relation to silicon. It will be demonstrated how these quantities govern initial navigation along metals in the periodic system to find future oxide candidates with feasible leakage characteristics. An overview will be included on the restraining influence of lower-k interlayers, interface states and oxide traps together with a critical survey of existing characterization methods for crucial quantities. Chemical properties like reactivity, structural stability and hygroscopic qualities of interesting oxides will be treated together with reliability issues. Finally, the future challenge of keeping up gate insulator development with the perspectives of the ITRS roadmap will be discussed

Electron states in MOS systems (Invited)

The properties of charge carrier traps in the oxide bulk, at high-k/silicon transition regions, at the silicon interface and as dipoles are discussed from physical and electrical perspectives. In order to elucidate the charging properties of oxide traps, the statistical mechanics for occupation is derived based on a constant pressure ensemble and used to interpret the influence of negative-U states occurring in high-k oxides. For the transition region close to the silicon interface, the existence of unstable traps in the continuous shift of the energy bands between SiO2 and HfO2 is pointed out. The physical background for electrical measurements on interface states is examined and, finally, dipoles constituted by traps in high-k dielectrics for regulating threshold voltage of MOS transistors are considered

Compensation effects at electron traps in semiconductors

The basic qualities for fulfilling the Meyer-Neldel rule (MNR) for thermal electron emission from semiconductor traps are investigated. A trap model including vibronic properties is used with varying entropy arising from the change in elasticity of the ionic part of the trap potential when an electron transition takes place. This gives rise to a system where the compensation effect originates from the increasing entropy change as a function of the enthalpy supply needed for the transition process in concord with Yelon-Movaghar theory. The entropy increase connects to a decrease in the activation energy for electron capture, which amplifies the compensation effect for MNR manifestation. By comparing with experimental data, the result achieved from the model clarifies the experimental observation of class partitioning for centers in GaAs, obeying the MNR. Furthermore, it is demonstrated that traps at metal-oxide-silicon interfaces, with the same properties as bulk traps following the MNR, give rise to capture cross-sections steeply increasing with the Gibbs free energy involved in carrier emission, as found by experiment