KINETICS OF LASER THERMAL-DECOMPOSITION OF TRIMETHYLAMINE ALANE

Using a focused Ar ion laser emitting at 514 nm, aluminum dots have be en deposited on silicon-coated quartz substrate via a pyrolytic decomp osition of trimethylamine alane. The growth kinetics of these Al dots was investigated as a function of the precursor pressure (1 to 7.5 mba r) and the laser-induced temperature. The threshold temperature for th e onset of growth was observed to be 210 degrees C. Deposition rates a s high as 3 mu m/s have been obtained at temperatures of about 300 deg rees C and were found to be independent of the precursor partial press ure. The activation energy of the deposition process was determined to be 18 kcal/mol. In order to understand the growth mechanism of these dots, several elementary steps occurring at the aluminum surface have been assumed involving AIH(3) as well as AlH2 and AlH adspecies. From this study it is concluded that the desorption of the hydrogen molecul es is the rate-limiting step in the laser chemical vapor deposition of Al from trimethylamine alane.