BEHAVIOR OF ADSORBED OXYGEN DURING RAPID ELECTRON-BEAM HEATING OF TA TI BILAYERS ON SINGLE-CRYSTAL SILICON/

Silicidation of thin films of Ta/Ti bilayers on silicon substrates, in the temperature range 750-1 000-degrees-C, using rapid electron-beam heating is described. The redistribution of adsorbed oxygen in the met al films and its effect on the formation of the silicide is examined. It was found that the silicidation of the bimetallic films proceeded s equentially. First titanium and then tantalum layers were converted in to their respective silicides. During the growth of titanium disilicid e, adsorbed oxygen moved to the interface between the unreacted tantal um film and the grown titanium disilicide, where it formed a thin laye r of silicon dioxide. The silicon dioxide barrier inhibited silicon di ffusion and the tantalum layer only converted to silicide at temperatu res higher than 750-degrees-C which were maintained for a few seconds.