Atomic layer deposition of thin hafnium oxide films using a carbon free precursor

Thin HfO2 films have been deposited on silicon via atomic layer deposition using anhydrous hafnium nitrate [Hf(NO3)(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 NO3 and NO2 moieties from the nitrate precursor. Residual nitrates were desorbed by anneals >400degreesC, however, the films remained oxygen rich. Crystallization of thin films (<10 nm) occurred at roughly 700 degrees C. For films less than similar to 10 nm thick, the effective dielectric constant of the film and any interfacial layer (neglecting quantum effects) was found to be in the range of k similar to 10-11. From a plot of electrical thickness versus optical thickness, the dielectric constant of the HfO2 layer was estimated to be k(HfO2)similar to 12 -14. Leakage current was lower than that of SiO2 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 HfSiOx). Excess oxygen in the films may also play a role in the reduced dielectric constant of the HfO2 layer.(C) 2003 American Institute of Physics.