Interfacial reaction induced strain relaxation in Hf-silicate film on strained Si_0.7Ge_0.3 (001) as a function of annealing temperature

Hf-based dielectrics were prepared using atomic layer deposition in order to investigate the effect of Si incorporation on the interfacial reaction and thermal stability in HfO₂ films on SiGe substrates. Two concentrations [100% HfO₂ and 50% HfO₂ 50% SiO ₂(HfSiO)] were used on strained Si_0.7Ge_0.3 substrates; a partially-crystalline phase was observed in the as-grown HfO ₂ film, and was not observed in the as-grown HfSiO film. Phase separation between the SiO_x and HfO_x in HfSiO film did occur, however, when the annealing temperature was increased to over 900 °C, leading to the out-diffusion of Si from the Si_0.7Ge_0.3 substrate and the formation of a Ge-rich layer at the interface between HfSiO and Si_0.7Ge_0.3. Finally, the strain in the Si _0.7Ge_0.3 substrate was relaxed, and interfacial states greatly increased in HfSiO/Si_0.7Ge_0.3 with the 900 °C anneal.