Atomic layer deposited hafnium-based gate dielectrics for deep sub-micron CMOS technology

Abstract

The physical and electrical properties of both HfO2 and Hf-aluminate films, deposited using atomic layer deposition (ALD), were investigated in detail. As-deposited HfO2 films on chemical SiO2 are amorphous, while films deposited on thermal SiO2 are polycrystalline films. Hf-aluminate films with 25% Al remain amorphous up to 900A?C, while films with 75% Al remain amorphous even after a 1050A?C spike anneal, a typical thermal cycle experienced in CMOS processing. An extremely small flatband voltage shift of 20-40 mV, which corresponds to a very low fixed charge of 2x10^11 cm-2, was achieved with high temperature annealing (800A?C a?? 900A?C). Leakage current densities of ~ 10^-6 A/cm2 were achieved for HfO2 gate stacks (equivalent oxide thickness ~ 19 ??), 10000x lower than those for conventional SiO2 gate stacks. By varying the relative number of for HfO2 and Al2O3, a range of mixed Hf-aluminate compositions can be obtained by ALD.