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

Abstract

The thermal stability of e-beam deposited multilayers (MLs) for soft X-ray reflection optics was studied under XeCl laser processing in vacuum. MLs with five Co/Si/W/Si periods, each 13.5 nm (MLS1) or 18.4 nm (MLS2) were deposited 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 MLS1 irradiations. The thermal stability of MLS1 is even better than for W/Si MLs studied previously. In laser irradiated samples the Co 2Si 3 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 Co 2Si 3 formation in MLS1 are explained by complex Co–Si silicide formation conditions and compressive stress parallel to the surface of irradiated samples.