Improving the ALD-grown Y₂O₃/Ge interface quality by surface and annealing treatments

Highlights: • Investigation of interfacial mechanisms for hydrofluoric and thermal pre-treated Ge-surfaces. • Improvement of interface trap density due to proper annealing treatments. • Further improvement of interfacial and electrical properties due to catalytic acting thin platinum layer. - Abstract: Metal Oxide Semiconductor capacitors are investigated, employing ALD grown Y₂O₃ as gate dielectric, and n-type (1 0 0) germanium as channel substrate. The effect of post deposition annealing (PDA) in oxygen and forming gas atmosphere using a thin catalytically acting platinum (Pt)-layer on the Y₂O₃/Ge interface is electrically analyzed for buffered hydrofluoric (BHF) and thermally pre-treated Ge-surfaces. The Pt-assisted PDA ensures even for BHF pre-treated samples very low values for the interface trap density D_it of 1.55 × 10¹¹ eV⁻¹ cm⁻² and low leakage current densities J of <7 × 10⁻⁹ A/cm² outperforming conventional PDA treatments. The interfacial formation of GeO₂ and yttrium germanate after PDA is proven by using X-ray Photoelectron Spectroscopy measurements.