Engineering chemically abrupt high-k metal oxide∕silicon interfaces using an oxygen-gettering metal overlayer

Abstract

High-$k$ metal oxide gate dielectrics may be required to extend Moore’s law of semiconductor device density scaling into the future. However, growth of a thin ${\mathrm{SiO}}_2$ -containing interface layer is almost unavoidable during the deposition of metal oxide films onto $\mathrm{Si}$ substrates. This limits the scaling benefits of incorporating high-$k$ dielectrics in future transistors. A promising approach, in which oxygen-gettering metal overlayers are used to engineer the thickness of the ${\mathrm{SiO}}_2$ -based interface layer between metal oxide and $\mathrm{Si}$ substrate after deposition of the metal oxide layer, is reported. Using a $\mathrm{Ti}$ overlayer with high solubility for oxygen on ${\mathrm{ZrO}}_2$ or ${\mathrm{HfO}}_2$ dielectrics, the effective removal of the low-$k$ interface layer at $300\mathrm{K}$ has been confirmed by electron microscopy and spectroscopy techniques. Significant enhancement of the gate capacitance density, while retaining low leakage current densities, has also been demonstrated for these interface-engineered high-$k$ gate stacks.