Chemical Vapor Deposition of Aluminum Oxide Thin Films Using Dimethylaluminum Isopropoxide as a Single Source Precursor

William J. Sweet III, Benjamin W. Schmidt, and Bridget R. Rogers. Chemical and Biomolecular Engineering Department, Vanderbilt University, 2400 Highland Ave., 107 Olin Hall, Nashville, TN 37235

            Ceramic oxides such as Al2O3 and HfO2 are useful in microelectronics and as high temperature thermal barriers. Thin films of these materials are attractive alternatives to SiO2 due to their dielectric attributes. Characterization and control of their properties are keys to development for use in CMOS devices. Chemical vapor deposition (CVD) is a popular processing method due to high deposition rates and good conformality. The CVD process is inherently sensitive to the choice of precursor. This study examines the use of dimethylaluminum isopropoxide (DMAI) and methylaluminum di-isopropoxide (MADI) as CVD precursors to aluminum oxide films. DMAI and MADI are respectively the one and two methyl-isopropoxide substituted derivatives of the popular precursor trimethylaluminum (TMA), making them similar in structure to aluminum tri-isopropoxide (AIP). TMA exhibits a high vapor pressure and is a liquid at room temperature, but is dangerous to handle and requires an additional oxidant. AIP is a single-source precursor but requires heating for melting and adequate vaporization, which can lead to system incompatibilities. Deposited films are characterized by X-ray photoelectron spectroscopy (XPS), Auger Electron Spectroscopy (AES), Rutherford backscattering spectrometry (RBS), and variable angle spectroscopic ellipsometry. Understanding the relationships between precursor structures and film composition, microstructure, and processing windows will help the development of application specific precursors.