Effect of Annealing on the Interfacial and Structural Properties of Amorphous Silicon-Hafnia Films

Chemical and physical properties of the interface formed between amorphous silicon (a-Si) and hafnium oxide (HfO2) were investigated using X-ray reflectivity (XRR) and X-ray photoelectron spectroscopy (XPS). XRR showed that the interface layer formed between the a-Si and HfO2 layer had a thickness of 0.7 ± 0.3 nm and a density of 4.4 ± 0.2 g/cm3. Based on the XPS results, the interface comprised HfO2, silicon oxide, and hafnium silicate phases. High-temperature annealing led to the conversion of elemental silicon and nonstoichiometric silicate into silicon dioxide phases. This reaction was also accompanied by the chemical reduction of the HfO2 phase. Annealed films crystallized into the monoclinic phase of HfO2 with a preferred orientation along the (111) axis.