Growth and characterization of MOMBE grown HfO ₂

HfO ₂ dielectric layers were grown directly on the p-type Si (1 0 0) by metalorganic molecular beam epitaxy (MOMBE). Hafnium tetra-butoxide was used as a Hf precursor and pure oxygen was introduced to form an oxide layer. The properties of the layers with different thicknesses were evaluated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), and capacitance-voltage (C-V) and current-voltage (I-V) analyses. XRD and HRTEM results showed that the HfO ₂ films thinner than 12 nm were amorphous while the films thicker than 12 nm began to crystallize in the tetragonal and the monoclinic phases. The XPS spectra of O 1s show that the O-Si binding energies shifted to the lower binding energy with increasing the HfO ₂ layer thickness. Moreover, the snap back phenomenon is observed in accumulation capacitance. These changes are believed to be linked with the decomposition of SiO and the crystallization of HfO ₂ layer during the film growth.