Metal oxide thin films deposited from metal organic precursors in supercritical CO2 solutions

This work demonstrates a novel method for deposition of metal oxide thin films, including Al2O3, ZrO2, MnOx, and RuOx where the metal-organic precursors and oxidizing agents are delivered in liquid and supercritical CO2. A cyclic deposition process is presented where reactants are introduced sequentially to control surface adsorption and byproduct removal steps. Reactions are studied in a hot wall reactor at pressures ranging from 1600 to 3600 psi at 80-200 degrees C, and X-ray photoelectron spectroscopy and infrared transmission confirmed metal oxide formation. We show that hydrogen peroxide is a viable O source for oxide deposition, whereas tert-butyl peracetate, which is a good electron acceptor, is less suited for oxygen donation. Capacitance versus voltage analysis of resulting Al2O3 films show good dielectric properties after post-deposition anneal. We believe that the good solvation properties of supercritical CO2 can aid in the delivery of precursors and in the removal of byproducts for advanced low-temperature processing of oxides and other materials of interest in electronic applications.