Excimer (XeCl) laser processing of W/Si bilayers and multilayers up to the Si melting threshold

Abstract

Interdiffusion phenomena, thermal damage and durability of W/Si bilayers and multilayers were studied. Samples were prepared by ultrahigh vacuum electron beam evaporation onto oxidized Si. The thickness of W and Si layers and the total thickness of the structures were 1–20nm and 40–100nm respectively. The samples were irradiated by using an XeCl laser ( λ = 308 nm) with 1–300 pulses at fluences of 0.15, 0.3 and 0.6 J cm −2. Small angle X-ray scattering, large angle X-ray scattering, Rutherford backscattering, transmission electron microscopy, surface profilometry and resistometry were used for analyses. Temperature profiles in structures were obtained by numerical calculations. At 0.6J cm −2 the samples were damaged even by a single laser shot. At 0.3J cm −2 WSi 2 formation, surface roughening and ablation were observed. The threshold for considerable changes was at 3−10 shots and at 10–30 shots for bilayers with W and Si surfaces respectively and at 100−300 shots for multilayers with the same total thickness of W thermal shield. At 0.15J cm −2 the periodicity of the multilayers was preserved.