MOCVD DEPOSITION OF MGAL2O4 FILMS USING METAL ALKOXIDE PRECURSORS

Amorphous thin films of MgAl2O4 have been deposited onto crystalline silicon and glass substrates from the metal alkoxide source, Mg[Al(OPri)(4)](2), at temperatures between 250 and 500 degrees C. The growth rate, which was negligible at 250 degrees C, increased with substrate temperature between 300 and 425 degrees C, consistent with a surface reaction limited process. Above 425 degrees C, the growth was limited by the availability of reactant, and no further increases in the conversion efficiency or the growth rate were observed. The volatility of the alkoxide source allowed vaporization at modest source temperatures, between 120 and 170 degrees C. The liquidity of the alkoxide at temperatures below 100 degrees C offers the possibility of low-cost, high-rate spray pyrolysis as a means of film deposition. Infrared adsorption by CH3 groups, clearly evident in films deposited at a substrate temperature of 350 degrees C, decreased with substrate temperature becoming undetectable at 500 degrees C. However, physical and electrical properties of the transparent, dense films showed little temperature dependence. Mg/Al ratios of 1:2 and high breakdown field strength were exhibited by nearly all films. Dielectric constants varied from 5 to 11 for films thicker than 1000 Angstrom as expected for a metal oxide film, but very thin films (<1000 Angstrom) frequently exhibited dielectric constants less than 2, independent of growth temperature.