Thermal behaviour of Co/Si/W/Si multilayers under high intensity excimer laser pulses

The thermal stability of e-beam deposited multilayers (MLs) for soft X-ray reflection optics was studied under XeCl laser processing in vacuum. MLs wi th five Co/Si/W/Si periods, each 13.5 nm (MLS1) or 18.4 nm (MLS2) were depo sited onto oxidized Si and irradiated at the fluences of 0.075-0.62 J cm(-2 ) by 1 or 100 pulses. The samples were analyzed by X-ray diffraction, hard X-ray reflectivity and sheet resistance measurements. The layered structure of our samples persists up to 0.62 J cm(-2) per 1 pulse for MLS2 and 0.62 J cm(-2) per 100 pulses for MLS 1 irradiations. The thermal stability of ML S 1 is even better than for W/Si MLs studied previously. In laser irradiate d samples the Co2Si3 phase which is normally formed under high pressures (> 4 GPa) was found. It has not been reported in the film couples so far. The high thermal stability and Co2Si3 formation in MLS1 are explained by compl ex Go-Si silicide formation conditions and compressive stress parallel to t he surface of irradiated samples. (C) 1999 Elsevier Science B.V. All rights reserved.