Low Temperature Deposition of Metal Oxide Thin Films in Supercritical Carbon Dioxide Using Metal-organic Precursors

Abstract

A novel chemical route in thin film formation that includes the use of inorganic and organic peroxides and metal organic complexes soluble in supercritical carbon dioxide has been investigated for the deposition of alumina, titania and zirconia thin films at low temperatures (<150°C). The metal organic precursors used include: Al(acac) 3 , OTi(tmhd) 2 , and Zr(acac) 4 . Tert-butyl peroxide, and a 30% aqueous solution of hydrogen peroxide were used as oxidants. Depositions were carried out in a 25 ml hot wall reactor at pressures ranging from 2100 to 3900 psi at 80-140°C. The deposited thin films were investigated by using X-ray photoelectron spectroscopy (XPS) and transmission Fourier transform infrared spectroscopy (FTIR). XPS and FTIR results indicate the formation of metal oxides thin films with some bonded carbon. The deposition temperatures achieved in this process are substantially lower than those used in conventional vacuum deposition techniques making feasible the deposition on temperature sensitive substrates and organic materials required for the development of hybrid organic/inorganic devices. Processing at low temperatures in supercritical carbon dioxide may provide the basis for the development of an alternative, environmentally friendly, thin film deposition technique for the processing of nanostructures.

Smooth and Conformal TiO2Thin-Film Formation Using Supercritical Fluid Deposition

“…Therefore, these three titanium precursors with tmhd or acac ligands were chosen as potential precursors for TiO 2 -SCFD at low process temperatures. The thermal decomposition temperatures of the precursors were reported to be around 400 • C under vacuum conditions; [28][29][30] thus, a decomposition temperature below 400 • C in SCFD would prevent thermal damage on integrated logic circuits. Table I shows the solubilities of these precursors in scCO 2 and the corresponding properties of the deposited films.…”