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

Y 2 O 3 thin films were grown onto Si(100) substrates by atomic layer deposition (ALD) using organometallic precursors, viz. tris(cyclopentadienyl)yttrium, Cp 3 Y, and tris(methylcyclopentadienyl)yttrium, (CpCH 3 ) 3 Y (Cp = cyclopentadienyl). Water was used as oxygen source. The deposition rate of yttria in the Cp 3 Y/H 2 O process slightly increased as a function of the deposition temperature, viz. from 1.5 to 1.8 Å/cycle at temperatures from 250 to 400 °C. With the (CpCH 3 ) 3 Y/H 2 O process, a constant growth rate of 1.2−1.3 Å/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 (CpCH 3 )Y and Cp 3 Y were 0.2 and 0.5 atom %, respectively. (CpCH 3 ) 3 Y/H 2 O-processed film contained 3.1 atom % of hydrogen, whereas the Cp 3 Y/H 2 O-processed film contained 1.8 atom %. With both processes the smoothest films were obtained at or below the deposition temperature of 250 °C.