Processing of Y2O3 Thin Films by Atomic Layer Deposition from Cyclopentadienyl-Type Compounds and Water as Precursors

Y2O3 thin films were grown onto Si(100) substrates by atomic layer deposition (ALD) using organometallic precursors, viz. tris(cyclopentadienyl)yttrium, Cp3Y, and tris(methylcyclopentadienyl)yttrium, (CpCH3)3Y (Cp = cyclopentadienyl). Water was used as oxygen source. The deposition rate of yttria in the Cp3Y/H2O process slightly increased as a function of the deposition temperature, viz. from 1.5 to 1.8 A/cycle at temperatures from 250 to 400 C. With the (CpCH3)3Y/H2O process, a constant growth rate of 1.2-1.3 A/cycle was achieved in a wide deposition temperature range of 200-400 C. The ALD-type growth mode was corroborated in both processes at 250 and 300 C. The deposited films were characterized by XRD, AFM, and TOF-ERDA for crystallinity, morphology, and chemical composition, respectively. Carbon impurity levels for films deposited at 300 C from (CpCH3)Y and Cp3Y were 0.2 and 0.5 atom %, respectively. (CpCH3)3Y/H2O-processed film contained 3.1 atom % of hydrogen, whereas the Cp3Y/H2O-processed film contained 1.8 atom %. With both processes the smoothest films were obtained at or below the deposition temperature of 250 C.