Extremely Scaled (∼0.2 nm) Equivalent Oxide Thickness of Higher-k (k = 40) HfO2 Gate Stacks Prepared by Atomic Layer Deposition and Oxygen-Controlled Cap Post-Deposition Annealing

Abstract

We fabricate ultrathin HfO2 gate stacks of very high permittivity by atomic layer deposition (ALD) and oxygen-controlled cap post-deposition annealing. The HfO2 layer is directly deposited on a wettability-controlled Si surface by ALD. To enhance permittivity, a cubic crystallographic phase is generated in ALD-HfO2 by short-time annealing with a Ti capping layer. The Ti layer absorbs residual oxygen in the HfO2 layer, which suppresses the growth of the interfacial SiO2 layer. The dielectric constant of ALD-HfO2 is increased to ∼40, and a gate stack of extremely scaled equivalent oxide thickness (∼0.2 nm) is obtained.