Deposition of ZrO2 and HfO2 thin films by liquid injection MOCVD and ALD using ansa-metallocenezirconium and hafnium precursors

Abstract

Thin films of ZrO₂ and HfO₂ have been deposited by liquid injection metalorganic chemical vapour deposition (MOCVD) and atomic layer deposition (ALD) using a range of ansa-metallocene precursors [(Cp₂CMe₂)ZrMe₂] (1), [(Cp₂CMe₂)ZrMe(OMe)] (2) [(Cp₂CMe₂)HfMe₂] (3), and [(Cp₂CMe₂)HfMe(OMe)] (4) with O₂ (MOCVD) or ozone (ALD) as oxygen source. The crystal structures of the new complexes 2 and 3 have been determined and they are shown to be mononuclear and isostructural to complex 1, containing a chelating [Cp₂CMe₂] ligand leading to a pseudo-four-coordinate distorted tetrahedral geometry around the central Zr or Hf atom, in agreement with structures from Density Functional Theory (DFT). The ZrO₂ and HfO₂ films were deposited by MOCVD over the temperature range 400–650 °C and by ALD over the temperature range 175–350 °C. X-Ray diffraction analysis showed that the HfO₂ films deposited by MOCVD were amorphous, whereas the ZrO₂ films deposited by MOCVD were in the tetragonal phase. Auger electron spectroscopy showed that residual carbon was present in all the films and that the films grown by MOCVD contained more carbon (2.4–17.0 at.%) than the films grown by ALD (1.8–2.8 at.%). The dielectric properties of ZrO₂ and HfO₂ films deposited by ALD were evaluated using [Al/MO₂/n-Si] metal oxide semiconductor capacitor (MOSC) structures which showed that the films had low current leakage densities of less than 6 × 10⁻⁷ A cm⁻² at ±2 MV cm⁻¹.