COPPER SILICIDE FORMATION BY RAPID THERMAL-PROCESSING AND INDUCED ROOM-TEMPERATURE SI OXIDE-GROWTH

The growth of copper silicide has been studied by rapid thermal processing (RTP) of 500 Å of Cu on Si substrates. Interaction between the diffusing metal and Si starts at 250-300°C. Annealing at higher temperatures yields complete silicidation to Cu3Si. This leads to strong modifications of the Auger line shapes of both Si and Cu. A plasmon peak located 20 eV below the main peak is the fingerprint in the Cu spectrum. Strong features at 80, 85.6, 89.2, and 93.2 eV as well as a 1 eV shift of the 90.4 eV peak appear in the Si L2,3VV spectrum. Whether for Cu films annealed in nitrogen or in vacuum, exposure of the silicide to air results in the growth of silicon oxide at room temperature and continues until the silicide layer is totally converted. This repeatable and controllable oxidation of silicon is accompanied by changes in resistivity and color reflecting the extent of the process. For Cu/CoSi 2/Si structures, the cobalt silicide acts as a transport medium for the growth of the copper silicide and also serves as a cap preventing the oxidation of the final CoSi2/Cu3Si/Si contacts.