Limitations for aggressively scaled CMOS Si devices due to bond coordination constraints and reduced band offset energies at Si-high-k dielectric interfaces

The three chemical bonding effects at Si-dielectric interfaces that are important in substituting alternative gate dielectric materials for SiO2 in aggressively scaled CMOS are (i) the character of the interface bonds, either isovalent with bond and nuclear charge balanced as in Si-SiO2, or heterovalent, where there is an inherent mismatch between bond and nuclear charge, (ii) physical bonding constraints related to the average number of bonds/atom, N-av and (iii) reduced conduction band offset energies in transition metal (T-M) elemental and binary oxides that are derived from increased ionic bonding and d-state contributions to the lowest conduction bands, These effects are discussed with respect to several different emerging high-k materials including (i) nitrides, (ii) T-M oxides, (iii) alloys of SiO2 and T-M oxides and (iv) Al2O3. (C) 2000 Published by Elsevier Science B.V.