Fabrication and characterization of pulsed laser deposited HfO₂films for high-<i>k</i>gate dielectric applications

Abstract

We investigated the structural and electrical properties of HfO2 films fabricated by the pulsed laser deposition technique. HfO2 films were deposited directly on n-Si (100) substrates and Pt coated silicon substrates, respectively, at 300°C in a 20 Pa N2 ambient, and in situ post-annealed in a 20 Pa N2 ambient. X-ray diffraction indicates that films post-annealed at temperatures more than 500°C exhibit a polycrystalline monoclinic structure. High-resolution transmission electron microscopy images clearly show that an interfacial layer (IL) between an amorphous HfO2 layer and the Si substrate exists. An x-ray photoelectron spectroscopy measurement was performed to identify this IL as nonstoichiometric Hf-silicate. The dielectric constant of amorphous HfO2 was determined to be about 26 by measuring the Pt/HfO2/Pt capacitor structures. Capacitance–voltage measurements show that a small equivalent oxide thickness of 1.26 nm for the 5 nm HfO2 film on the n-Si substrate, with a leakage current of 2.2 mA cm−2 at 1 V gate voltage was obtained.