Improvements in the electrical properties of high-k HfO2 dielectric films on Si1−xGex substrates by postdeposition annealing

The changes in atomic-layer-deposited HfO2 films on Si and Si1−xGex (x=0.1, 0.2, and 0.3) substrates by postdeposition annealing were studied. The migration of Ge reduced the capacitance equivalent thickness while keeping the leakage current density almost invariant after annealing. High resolution x-ray photoelectron spectroscopy and secondary ion mass spectroscopy analyses confirmed that Ge atoms which had diffused into the HfO2 layer during the deposition were drawn back to the substrate by annealing which was accompanied by the decrease in the interfacial strain energy. A very low interface trap density (1.3×1010cm−2eV−1) was obtained when x=0.3.