Growth and characterization of Hf-silicate/Al2O3 gate stacks grown on Si(100) by self-limiting atomic layer deposition

Abstract

A thin film structure of a HfSixOy/Al2O3/Si gate stack was fabricated on Si(100) by self-limiting atomic layer chemical vapor deposition (ALCVD). An atomically flat interface of Al2O3/silicon was observed and the impurity concentrations in the bulk film were below the XPS detection limit. Hf-silicate (HfSixOy) film was deposited using tetrakis-diethylamido-hafnium [Hf(N(C2H5)(2))(4)] and tetra-n-butyl-orthosilicate [Si(OC4H9)(4)], The grown Hf-silicate film showed a Si-rich composition (similar to 30% HfO2), whereas an Al2O3 layer showed a stoichiometric composition ratio of O/Al. The electrical properties of the gate stack were characterized using capacitance-voltage (C-V) and current-voltage (I-V) measurements of the metal-oxide-metal (MIM) structure. The dielectric constant (k similar to 10.5) of the HfSixOy/Al2O3 film was higher than that (k similar to 8.1) of an Al2O3 single layer of a similar thickness. Rapid thermal annealing (RTA)-treated HfSixOy/Al2O3 films showed a positive shift in flat band voltage (V-fb), whereas as-deposited samples did not show positive shifts in V-FB. The leakage current densities (J(g)) of the as-grown and the annealed HfSixOy/Al2O3 films were both below 1 X 10(-7) A/cm(2) at a bias of -1.0 V.