Atomic Layer Deposition and in-situ characterization of yttrium oxide and yttria-stabilized zirconia

摘要

Y_2O_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℃ - 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℃ as a function of Y(EtCp)_3 and H_2O 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℃ 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_2O_3 to ZrO_2 cycle ratio.