Evaluation of the electrical properties and interfacial reactions for the polycrystalline $Si1−xGex(x=0,0.6)/HfO2$ gate stack

The effect of interfacial reactions on the electrical properties of a polycrystalline (poly) $Si1−xGex/HfO2$ gate stack were evaluated in terms of annealing conditions and the results were compared with those of a conventional poly-$Si/HfO2$ system. In the poly-$Si0.4Ge0.6/HfO2$ gate stack, silicate formation was the dominant reaction at the poly-$Si0.4Ge0.6/HfO2$ interface after annealing at 900 °C, resulting in the significant decrease in leakage current. From x-ray photoelectron spectroscopy analysis, the binding states of Hf silicates were clearly observed at a binding energy of about 16.1 eV in Hf $4f$ spectra and 102.7 eV in Si $2p$ spectra. However, in the poly-$Si/HfO2$ gate stack, the accumulation capacitance became undeterminable and the leakage current increased suddenly after annealing at 900 °C due to silicide formation at the poly-$Si/HfO2$ interface. The differences in reactions between a poly-$Si/HfO2$ interface and a poly-$Si0.4Ge0.6/HfO2$ interface are attributed to the accumulation of Ge.