Smooth and Conformal TiO 2 Thin-Film Formation Using Supercritical Fluid Deposition

Abstract

Conformal TiO2 having a smooth surface was deposited using a flow-type reactor for supercritical fluid deposition (SCFD). Ti(O-iPr) 2 (tmhd)2 was selected as the best candidate for SCFD from among three candidates because it exhibited the best results according to the following criteria: solubility in supercritical CO2 (scCO 2), carbon impurities in the TiO2, and surface morphology of the deposited film. The growth rate increased with increasing temperature from 200 to 300°C. The activation energy in this temperature range was measured to be about 46.3 kJ/mol. Compared with conventional methods, such as chemical vapor deposition (CVD; activation energy of 85 kJ/mol, decomposition temperature above 450°C), TiO2-SCFD had a much lower activation energy owing to the solvent effect of scCO2. We also examined the growth-rate dependence on the precursor concentration and found first-order reaction kinetics such that the surface reaction rate constant (ks) was as low as 2.0 × 10-6 m/s at 300°C. This process resulted in good step coverage during film formation on trenches with an aspect ratio of 12.5. © 2013 The Electrochemical Society.