Impact of Fin Doping and Gate Stack on FinFET (110) and (100) Electron and Hole Mobilities

Double-gate FinFET (110) (110) and (100) (100} electron mobility (μ_e) and hole mobility (μ_h) are experimentally investigated for the following: 1) a wide range of boron and phosphorus fin doping concentrations and 2) a wide variety of gate stacks combining HfO₂, SiO₂, or SiON insulators with TiN or poly-Si electrodes. It is found out that, irrespective of fin doping and gate stack, (110) (110) μ_e is competitive with the (100)(100) μ_e, while (110)(110) μ_h is ≥ 2× higher than (100) (100) μ_h. Inversion μ_e and μ_h are independent of doping as long as the effective field/doping combination enables the screening of the depletion charge. Mobility degradation with doping is significantly lower in accumulation mode (AM) than in inversion mode (IM) such that, for heavily B-doped fins, AM hole mobility exceeds the IM electron mobility even in (100) FinFETs. In undoped fins, ALD TiN gate stress is observed to improve μ_e for both orientations without degrading μ_h.