Controlled growth of HfO2 thin films by atomic layer deposition from cyclopentadienyl-type precursor and water

Abstract

HfO₂ thin films have been deposited onto p-Si(100) substrates by atomic layer deposition (ALD) using Cp₂Hf(CH₃)₂ (Cp = cyclopentadienyl) and water as precursors at 300–500 °C. Processing parameters were optimised and the ALD type growth mode corroborated at 350 °C where a deposition rate of 0.42 Å cycle⁻¹ was obtained. The crystallinity, morphology and chemical composition of the deposited films were characterised. Films deposited at 300–450 °C were polycrystalline with monoclinic (−111) as the preferred orientation. Impurity levels of the stoichiometric HfO₂ films deposited at 350 and 400 °C were very low, or below 0.4 and 0.25 atom% for carbon and hydrogen, respectively. In addition, ultrathin HfO₂ films showed good dielectric properties such as low hysteresis and nearly ideal flatband voltage.