AVS 53rd International Symposium
    Thin Film Thursday Sessions
       Session TF-ThM

Paper TF-ThM5
Solvation Effects in the Kinetics of Supercritical CO@sub 2@ Based Deposition of Metal Oxide Thin Films

Thursday, November 16, 2006, 9:20 am, Room 2022

Session: Fundamentals in Thin Film Deposition
Presenter: Q. Peng, North Carolina State University
Authors: Q. Peng, North Carolina State University
K.J. Park, North Carolina State University
D. Hojo, North Carolina State University
D. Barua, North Carolina State University
G.N. Parsons, North Carolina State University
Correspondent: Click to Email
Supercritical CO@sub 2@ (scCO@sub 2@) offers unique solvent properties for metal-organic deposition, such as high solubility, high diffusion rate, zero surface tension, and high penetration ability. In our work, supercritical carbon dioxide process has been successfully used to deposit a variety of metal oxides including Ga@sub 2@O@sub 3@, Al@sub 2@O@sub 3@, ZrO@sub 2@, FeO@sub x@, Cr@sub 2@O@sub 3@, Co@sub 3@O@sub 4@, and WO@sub x@ thin films on native oxide silicon wafer from direct pyrolysis of organometallics. Conformal and reflective metal oxide films with good adhesion have been obtained. The kinetics of Al@sub 2@O@sub 3@ and Ga@sub 2@O@sub 3@ deposition has been studied to show the mechanism of scCO@sub 2@ based deposition process. For example, for Al@sub 2@O@sub 3@ deposition from Al(acac)@sub 3@, the deposition rate at 200°C is observed to be 10nm/min, compared to <1nm/min for typical vacuum based CVD from the same precursor. Similar results were observed for Ga@sub 2@O@sub 3@ thin film from Ga(acac)@sub 3@. Moreover, an overall activation energy of 60-70 kJ/mol and 80-85 kJ/mol were observed for pyrolysis of Al(acac)@sub 3@ and Ga(acac)@sub 3@ in scCO@sub 2@ phase, respectively, which are less than typical values obtained in vacuum CVD. Solvation energy of stabilization of the reaction transition state is suggested as the main reason for the enhanced surface reaction rates. The reduced kinetic barrier will be discussed in terms of relative polarity of the solvent and transition state structure. The solvation effect of scCO@sub 2@ can enable lower process temperature to enable material processing on temperature-sensitive surfaces.