Atomic layer deposition of hafnium oxide dielectrics on silicon and germanium substrates

Hafnium oxide films have been deposited at 250 °C on silicon and germanium substrates by atomic layer deposition (ALD), using tetrakis-ethylmethylamino hafnium (TEMAH) and water vapour as precursors in a modified Oxford Instruments PECVD system. Self-limiting monolayer growth has been verified, characterised by a growth rate of 0.082 nm/cycle. Layer uniformity is approximately within ±1% of the mean value. MOS capacitors have been fabricated by evaporating aluminium electrodes. CV analysis has been used to determine the bulk and interface properties of the HfO2, and their dependence on pre-clean schedule, deposition conditions and post-deposition annealing. The dielectric constant of the HfO2 is typically 18. On silicon, best results are obtained when the HfO2 is deposited on a chemically oxidised hydrophilic surface. On germanium, best results are obtained when the substrate is nitrided before HfO2 deposition, using an in-situ nitrogen plasma treatment.