Characteristics of atomic layer deposition grown HfO₂ films after exposure to plasma treatments

Ultra thin HfO₂ films were grown by the atomic layer deposition (ALD) technique using tetrakismethylethylaminohafnium (Hf[N(CH)₃(C₂H₅)]₄) and ozone (O₃) as the precursors and subsequently exposed to various plasma conditions, i.e., CCP (capacitively coupled plasma) and MMT (modified magnetron typed plasma) in N₂ or N₂/O₂ ambient. The conventional CCP treatment was not effective in removing the carbon impurities, which were incorporated during the ALD process, from the HfO₂ films. However, according to the X-ray photoelectron spectroscopy measurements, the MMT treated films exhibited a significant reduction in their carbon contents and the efficient incorporation of nitrogen atoms. Although the incorporated nitrogen was easily released during the post-thermal annealing of the MMT treated samples, it was more effective than the CCP treatment in removing the film impurities. Consequently, the MMT treated samples exhibited excellent electrical properties as compared to the as-deposited HfO₂ films, including negligible hysteresis (flatband voltage shift), a low leakage current, and the reduced equivalent oxide thickness of the gate stack. In conclusion, MMT post treatment is more effective than conventional CCP treatment in improving the electrical properties of high-k films by reducing the carbon contamination and densifying the as-deposited defective films.