Investigation of sputtering target re-deposits by Optical Coherence Tomography and grazing incident X-ray diffraction

Abstract

The sputtering target re-deposit grown by cumulative sputtering has been investigated in this work by studying both fresh and rigorously sputtered zirconium oxide target by Fourier Domain Optical Coherence Tomography (FDOCT), a depth resolved optical imaging modality. The Optical Coherence Tomography (OCT) depth profiles have further been analysed to extract optical attenuation coefficient of sputtered target surface as well as fresh target surface. Re-deposited sputtered target surface shows larger optical attenuation coefficient in the range of 1.5–4.4 mm−1 as opposed to that of 1.1 mm−1 for fresh ZrO2 target. The same sputtered target surfaces have also been looked into by using grazing incident X-ray diffraction technique with an optimised grazing angle of incidence. A strong correlation between structural changes of re-deposited surface and the extent of light depth penetration obtained by analysing OCT depth profiles at different locations of the sputtered target was observed. The results indicate, that FDOCT can be considered to be an effective tool to probe sputtering target re-deposits, with the advantage of being faster and non-contact method.