Preparation and characterization of HfO₂ thin films by photo-assisted MOCVD

Abstract
High-k dielectric HfO₂ thin films have been prepared by photo-assisted metal-organic chemical vapor deposition (MOCVD). Vacuum ultraviolet (VUV) light is used for enhancement of chemical reaction of the source materials of (Hf(O-t-C₄H ₉)₄) (HTB) and H₂O. The absorption spectrum of HTB has been calculated with molecular orbital method. The calculated infrared absorption of HTB is found in VUV region (around 150 nm), and HfO₂ thin films were deposited under the irradiation with VUV light of a D₂ lamp including the HTB absorption band. These prepared films are characterized by FT-IR measurement to estimate the concentration of organic impurities. It shows that C-H peak drastically decreases less in the photo-assisted MOCVD film than the MOCVD. Moreover, C-V characteristics show that accumulation capacitance is increased in the film deposited under VUV irradiation. The accumulation capacitance is much increased by rapid thermal annealing (RTA) in the case of photo-assisted MOCVD. AFM observation results show that very smooth surface is obtained in the photo-assisted MOCVD films.