ION ENERGY, ION FLUX, AND ION SPECIES EFFECTS ON CRYSTALLOGRAPHIC ANDELECTRICAL-PROPERTIES OF SPUTTER-DEPOSITED TA THIN-FILMS

The effects of ion bombardment conditions on the crystallographic and electrical properties of tantalum thin films grown on SiO2 and Si have been systematically investigated in Ta thin film formation process em ploying low-energy ( < 100 eV) inert -gas ion bombardment on a growing film surface. It is demonstrated that the properties of Ta films are strongly dependent upon ion energy and ion flux as well as substrate m aterials. The bcc-Ta can be formed on SiO2 by controlling impinging io n energy and normalized ion flux defined as the ratio of ion flux to T a flux ranging lower than 20 eV and higher than 13, respectively, for Ar plasma. Based on these results, low-resistivity bcc-Ta thin films ( 14.8 mu Omega cm at 300 K) have been successfully formed. It is also e xperimentally shown that the irradiation by ions with different mass n umbers has different effects on growing film properties. even if the e nergy or momentum of the ions is the same. When normalized ion flux is 26, bcc-Ta films can be grown on Si at ion energy lower than 30 eV fo r Ar ions and at ion energy ranging from 30 to 90 eV for Xe ions. The results also suggest that there are two cases where the phase transiti on from bcc to beta occurs. One is caused by defects induced by the re coil implantation of Ta atoms due to the excessive higher-energy ion b ombardment and the other is induced by defects due to insufficient tot al energy input to a growing film surface by ion irradiation and resul ting poor film quality. (C) 1997 American Vacuum Society.