Low Temperature Atomic Layer Deposition of Crystalline In2O3 Films

Crystalline In2O3 thin films were deposited by atomic layer deposition (ALD) using tris(2,2,6,6-tetramethyl-3,5-heptanedionato) indium(III), [In(TMHD)(3)] as an indium source and O2 plasma. Resulting growth rates were studied as a function of precursor pulse, reactant pulse, deposition temperature, and number of ALD cycles. The film growth rate was found to be 0.14 angstrom/cycle within the wide ALD temperature window of 100-400 degrees C. X-ray photoelectron spectroscopic (XPS) and X-ray diffraction (XRD) analysis revealed stoichiometric In2O3 thin films with polycrystalline cubic structure, even at 100 degrees C. All the as-deposited films were smooth, with RMS roughness values between 0.39 to 0.47 nm, as shown by atomic force microscopic (AFM) analysis. The optical properties and electrical resistivities of the films were determined by spectroscopic ellipsometry (SE) and four-point probe measurements. The highly transparent (ca. 94% in the visible region) films had a refractive index of 2.01-2.05 and a resistivity of 2.5-3 m Omega.cm.