Thin HfO 2 films have been deposited on silicon via atomic layer deposition using anhydrous hafnium nitrate ͓Hf(NO 3) 4 ͔. Properties of these films have been investigated using x-ray diffraction, x-ray reflectivity, spectroscopic ellipsometry, atomic force microscopy, x-ray photoelectron spectroscopy, and capacitance versus voltage measurements. Smooth and uniform initiation of film growth has been detected on H-terminated silicon surfaces. As-deposited films were amorphous, oxygen rich, and contained residual NO 3 and NO 2 moieties from the nitrate precursor. Residual nitrates were desorbed by anneals Ͼ400°C, however, the films remained oxygen rich. Crystallization of thin films (Ͻ10 nm) occurred at roughly 700°C. For films less than ϳ10 nm thick, the effective dielectric constant of the film and any interfacial layer ͑neglecting quantum effects͒ was found to be in the range of kϳ10Ϫ11. From a plot of electrical thickness versus optical thickness, the dielectric constant of the HfO 2 layer was estimated to be k HfO 2 ϳ12 Ϫ14. Leakage current was lower than that of SiO 2 films of comparable equivalent thickness. The lower than expected dielectric constant of the film stack is due in part to the presence of an interfacial layer ͑likely HfSiO x). Excess oxygen in the films may also play a role in the reduced dielectric constant of the HfO 2 layer.
Atomic layer deposition of uniform thin hafnium oxide films has been demonstrated directly on H-terminated silicon surfaces using anhydrous hafnium nitrate (Hf(NO 3 ) 4 ) precursor and H 2 O vapor. Atomic layer deposition was initiated on hydrogen terminated silicon surfaces and occurred at substrate temperatures as low as 160°C. X-ray diffraction analysis indicated that as-deposited films were smooth, uniform, and amorphous, and that film morphology can be altered by a post-deposition anneal. X-ray photoelectron spectroscopy analysis indicated that films are oxygen rich, contain silicate, and that residual NO 3 and NO 2 from the precursor can be eliminated by a post-deposition anneal. For a ϳ57 Å HfO 2 film, a dielectric constant of Х 10.5 and a capacitive equivalent thickness of ϳ21 Å were obtained.
We report on the electrical properties of HfO2 deposited via atomic layer deposition using Hf(NO3)4 precursor for metal/oxide/semiconductor gate dielectric applications. Thin films, with less than 1% variation in accumulation capacitance over a 150 mm wafer, have been deposited directly on hydrogen-terminated Si wafers. The effective dielectric constant of thin (<10 nm) films was in the range of κeff=10–12, the breakdown voltage was about 6–9 MV/cm, and the leakage current was between 3–6 orders of magnitude lower than that of SiO2. The relative benefit of lower leakage current of HfO2 over SiO2 decreased with decreasing effective thickness. Electron trapping was observed under constant voltage stressing.
which could be eliminated from forming gas post-annealing process. On the electrical property measurement, the 57Å hafnium oxide thin film showed a dielectric constant of k ~ 10.5 and a capacitive equivalent thickness of approximately 21Å.
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