Interface formation during molecular beam epitaxial growth of neodymium oxide on silicon

Abstract

The Si/dielectric interface properties influence device performance significantly. Often the interface is not stable and changes during and/or after the growth. For a better understanding of the interface and layer formation processes of Nd2O3 on Si(001), as an example for the lanthanide oxides, well-defined experimental studies by reflection high-energy diffraction and x-ray photoelectron spectroscopy were performed under ultraclean ultrahigh vacuum conditions of molecular beam epitaxy. Complementary investigations were performed by transmission electron microscopy. We found that Nd2O3 is a candidate for replacing silicon dioxide as gate dielectric in future Si devices with suitable band gap and offset with respect to silicon. However, under ultrahigh vacuum conditions, silicide formation occurs in the initial stage of growth, which can result in large silicide inclusions and hole formation during further growth. This effect can be completely prevented by modifying the oxygen partial pressure during the interface formation and layer growth.

Current transport mechanisms in metal – high-k dielectric – silicon structures

“…At room temperature for p-type silicon doped with impurity concentration 3 16 cm 10 5   , the Fermi level is situated at 0.13 eV above the Si valence band [26]. The valence band offset at the Gd 2 O 3 /Si interface lies in the range from 2.3 to 2.78 eV [3,27,28] in dependence on methods of measurement and at Nd 2 O 3 /Si interface is equal to 2.7 eV [29]. Thus, in Gd 2 O 3 location of the deep levels takes place at 2.5 to 3.0 eV above the valence band edge, and in Nd 2 O 3 the deep levels are situated at 2.9 eV above the valence band edge.…”

Growth and characterization of crystalline gadolinium oxide on silicon carbide for high- application

“…Commercially available, granular stoichiometric Gd 2 O 3 material was evaporated using an electron-beam heating with typical rates in the range of 0.01 nm/s. Since electron-beam evaporated REO layers are usually oxygen deficient [22], the Gd 2 O 3 layers were subjected to additional molecular oxygen during growth, which was introduced into the growth chamber using a piezo leak valve to adjust an oxygen partial pressure of 1.5×10 −7 mbar. For the electrical characterization, capacitors were fabricated without leaving the vacuum by the deposition of a metal gate (200 nm Pt) on the Gd 2 O 3 layer at room temperature through a mask in a separate chamber.…”

Crystalline Nanoscale M<SUB>2</SUB>O<SUB>3</SUB> (M=Gd, Nd) Thin Films Grown by Molecular Beam Epitaxy on Si(111)

“…During the layer growth, additional molecular oxygen was supplied into the chamber due to the oxygen deficiency in the rare-earth oxides evaporated by electron beam. 9,10) The substrate temperature was set to 948 K and the partial pressure of oxygen was kept at 5 Â 10 À7 mbar, which was controlled by a piezo leak valve. Crystal structures of the grown oxides were examined along the out-of-plane, in-plane, and asymmetric reciprocal space directions, as schematically shown in Fig.…”