Interface defects in HfO₂, LaSiO_x, and Gd ₂O₃ high- k /metal-gate structures on silicon

In this work, we present experimental results examining the energy distribution of the relatively high (>1× 1011 cm-2) electrically active interface defects which are commonly observed in high-dielectric-constant (high- k) metal-insulator-silicon systems during high- k process development. This paper extends previous studies on the Si(100) SiOx HfO2 system to include a comparative analysis of the density and energy distribution of interface defects for HfO2, lanthanum silicate (LaSiOx), and Gd2 O3 thin films on (100) orientation silicon formed by a range of deposition techniques. The analysis of the interface defect density across the energy gap, for samples which experience no H2 N2 annealing following the gate stack formation, reveals a peak density (∼2× 1012 cm-2 eV-1 to ∼1× 1013 cm-2 eV-1) at 0.83-0.92 eV above the silicon valence bandedge for the HfO2, LaSiOx, and Gd2 O3 thin films on Si(100). The characteristic peak in the interface state density (0.83-0.92 eV) is obtained for samples where no interface silicon oxide layer is observed from transmission electron microscopy. Analysis suggests silicon dangling bond (Pbo) centers as the common origin for the dominant interface defects for the various Si(100) SiOx /high- k /metal gate systems. The results of forming gas (H2 N2) annealing over the temperature range 350-555°C are presented and indicate interface state density reduction, as expected for silicon dangling bond centers. The technological relevance of the results is discussed.