Effect of NH3 and N2 annealing on the interfacial and electrical characteristics of La2O3 films grown on fully depleted SiGe-on-insulator substrates

Abstract

The interfacial structure and the electrical properties of pulsed laser deposition derived La2O3 ultra-thin films on fully depleted SiGe-on-insulator (FD SGOI) substrates before and after post-annealing in NH3 and N2, respectively, have been investigated comparatively. The results from high-resolution transmission electron microscopy and x-ray photoelectron spectroscopic revealed that interface reactions take place after the NH3 and N2 annealing process, but, as compared with the N2 annealing process, the NH3 annealing process can effectively decrease the thickness of the interfacial layer and incorporate more nitrogen at the dielectric/SiGe interface, resulting in smaller equivalent oxide thickness. The La2O3 capacitors annealed in NH3 show good capacitance–voltage characteristics with negligible hysteresis, smaller interface trap density and lower gate-leakage current density in comparison with those of capacitors annealed in N2. It is demonstrated that the NH3 annealing process can be a promising technology in improving the quality of high-k dielectric on FD SGOI substrates.