LASER CHEMICAL VAPOR-DEPOSITION OF COBALT THIN-FILMS

Smooth cobalt thin films have been deposited by decomposing dicobalt octacarbonyl [Co2(CO)8] with 248 nm excimer laser radiation. Area selective deposition has been achieved by imaging a mask onto soda-lime glass and Suprasil quartz substrates. The decomposition has been found to be partially due to thermal decomposition of the cobalt carbonyl on the laser-heated surface and partially due to photolysis of adsorbed cobalt carbonyl molecules. The crystalline structure of the cobalt films was found to depend on the laser fluence. For a fluence below 115 mJ cm-2 per pulse, the hcp phase was produced, but for higher fluences the fcc phase was formed, and was found to be stable at room temperature. Examination of the optically smooth surface of the low fluence films showed nanometer scale ridges parallel to the gas flow direction.