Modification of electrical properties and carrier transportation mechanism of ALD-derived HfO2/Si gate stacks by Al2O3 incorporation

Effect of Al2O3 incorporation on the electrical properties and carrier transportation of atomic-layer-deposited (ALD) HfAlO high-k gate dielectrics on Si substrates have been investigated. Electrical analyses indicate that interfacial properties of HfAlO/Si gate stack have been improved and leakage current is reduced after Al2O3 incorporation into HfO2. Additionally, the HfAlO sample with precursor ratio (TEMAH: TMA) of 4:2 exhibits the lowest interface state density (D-it) of 3.6 x 10(11) cm(-2) eV(-1), the lowest border trapped oxide charge density (N-bt) of 2.4 x 10(11) cm(-2), the lower density of oxide charge (Q(ox)) of 0.9 x 10(12) cm(-2), and the lowest frequency dispersion of 0.15%. In addition, the carrier transportation mechanism for both HfO2 and HfAlO has been investigated systematically. Based on the analysis, it can be concluded that Poole-Frenkle (P-F) emission is main conduction mechanism at the low electric field, and direct tunneling (D-T)dominates the conduction mechanism at the high field, respectively. (C) 2016 Elsevier B.V. All rights reserved.