Growth, microstructure and electrical properties of sputter-deposited hafnium oxide (HfO2) thin films grown using a HfO2 ceramic target

Hafnium oxide (HfO2) thin films have been made by radio-frequency (rf) magnetron-sputtering onto Si(1 0 0) substrates under varying growth temperature (Ts). HfO2 ceramic target has been employed for sputtering while varying the Ts from room temperature to 500 deg. C during deposition. The effect of Ts on the growth and microstructure of deposited HfO2 films has been studied using grazing incidence X-ray diffraction (GIXRD), and high-resolution scanning electron microscopy (HR-SEM) coupled with energy dispersive X-ray spectrometry (EDS). The results indicate that the effect of Ts is significant on the growth, surface and interface structure, morphology and chemical composition of the HfO2 films. Structural characterization indicates that the HfO2 films grown at Ts < 200 deg. C are amorphous while films grown at Ts > 200 deg. C are nanocrystalline. An amorphous-to-crystalline transition occurs at Ts = 200 deg. C. Nanocrystalline HfO2 films crystallized in a monoclinic structure with a (-1 1 1) orientation. An interface layer (IL) formation occurs due to reaction at the HfO2-Si interface for HfO2 films deposited at Ts > 200 deg. C. The thickness of IL increases with increasing Ts. EDS at the HfO2-Si cross-section indicate that the IL is a (Hf, Si)-O compound. The electrical characterization using capacitance-voltage measurements indicate that the dielectric constant decreases from 25 to 16 with increasing Ts. The current-voltage characteristics indicate that the leakage current increases significantly with increasing Ts due to increased ILs.