Atomic layer deposition of high-quality Al2O3 and Al-doped TiO2 thin films from hydrogen-free precursors

Abstract Possibilities for atomic layer deposition of Al 2 O 3 films from chloride and ozone were studied in order to avoid application of precursors that could leave hydrogen impurities in the films. Growth of Al 2 O 3 was obtained at substrate temperatures of 300–450 °C. At these temperatures, the growth rate was close to the values reported for corresponding H 2 O-based processes. Studies of thin-film composition revealed that reactivity of O 3 was sufficient to ensure deposition of films with chlorine concentration below 0.05 at.% at 350–450 °C. Application of the AlCl 3 –O 3 atomic layer deposition process for in situ Al-doping of TiO 2 thin films demonstrated that the amount of Al incorporated into the films during a single deposition cycle depended on the doping level. A reason for this effect was the influence of Al-doping on the phase composition of the film material. Al-doping of the TiO 2 films significantly reduced the surface roughness allowing deposition of high-density films with very flat surfaces. In capacitor structures with capacitance equivalent oxide thicknesses below 0.4 nm, the Al-doped TiO 2 films deposited from TiCl 4 , AlCl 3 and O 3 demonstrated markedly lower leakage current densities than the films with similar capacitance densities grown from TiCl 4 , Al(CH 3 ) 3 and H 2 O and from TiCl 4 , Al(CH 3 ) 3 and O 3 did.