Atomic Layer Deposition and in-Situ Characterization of Yttrium Oxide and Yttria-Stabilized Zirconia

Abstract

Y 2 O 3 and YSZ thin films were thermally deposited by atomic layer deposition in a commercial ALD cross flow reactor. Using a Low Vapor Pressure Delivery system, tris(ethylcyclopentadienyl) yttrium - Y(EtCp) 3 - heated at 120˚C - was used as a precursor. Tetrakis(dimethylamido)zirconium - TDMAZr and water were used for ZrO 2 . In-situ quartz crystal microbalance and spectroscopic ellipsometry were implemented in order to rapidly screen the ALD process space from 150 to 300˚C as a function of Y(EtCp) 3 and H 2 O doses and purge conditions. The optimized process led to excellent wafer-scale performances with good thickness uniformity and excellent process reproducibility. The yttria film properties were optimal around 225-250˚C with a high refractive index (1.93), low carbon concentration (<0.1%) and Y 0.4 O 0.6 stoichiometry. The growth of ternary YSZ oxides was monitored by QCM and showed that the composition of yttria in zirconia was readily controlled by adjusting the Y 2 O 3 to ZrO 2 cycle ratio.