Materials characterization of ZrO2-SiO2 and HfO2-SiO2 binary oxides deposited by chemical solution deposition

The thermal stability, microstructure, and electrical properties of xZrO(2) . (100-x)SiO2 (ZSO) and xHfO(2). (100-x)SiO2 (HSO) (x=15%, 25%, 50%, and 75 %) binary oxides were evaluated to help assess their suitability as a repla cement for silicon dioxide gate dielectrics in complementary metal-oxide-se miconductor transistors. The films were prepared by chemical solution depos ition using a solution prepared from a mixture of zirconium, hafnium, and s ilicon butoxyethoxides dissolved in butoxyethanol. The films were spun onto SiOxNy coated Si wafers and furnace annealed at temperatures from 500 to 1 200 degreesC in oxygen for 30-60 min. The microstructure and electrical pro perties of ZSO and HSO films were examined as a function of the Zr/Si and H f/Si ratio and annealing temperature. The films were characterized by x-ray diffraction, mid- and far-Fourier transform infrared (FTIR), Rutherford ba ckscattering spectroscopy, and Auger electron spectroscopy. At ZrO2 or HfO2 concentrations greater than or equal to 50%, phase separation and crystall ization of tetragonal ZrO2 or HfO2 were observed at 800 degreesC. At ZrO2 o r HfO2 concentrations less than or equal to 25%, phase separation and cryst allization of tetragonal ZrO2 or HfO2 were observed at 1000 degreesC. As th e annealing temperature increased, a progressive change in microstructure w as observed in the FTIR spectra. Additionally, the FTIR spectra suggest tha t HfO2 is far more disruptive of the silica network than ZrO2 even at HfO2 concentrations less than or equal to 25%. The dielectric constants of the 2 5%, 50%, and 75% ZSO films were measured and were observed to be less than the linear combination of ZrO2 and SiO2 dielectric constants. The dielectri c constant was also observed to increase with increasing ZrO2 content. The dielectric constant was also observed to be annealing temperature dependent with larger dielectric constants observed in nonphase separated films. The Clausius-Mossoti equation and a simple capacitor model for a phase separat ed system were observed to fit the data with the prediction that to achieve a dielectric constant larger than 10 doping concentrations of ZrO2 would h ave to be greater than 70%. (C) 2001 American Institute of Physics.