Laser-cleaning of atmospheric pressure plasma jet etched Zerodur

Atmospheric pressure plasma jet (APPJ) etching of Zerodur® with fluorine containing process gases leads to the generation of non-volatile metal fluorides which remain on the surface and form a residual layer. This results in masking effects and therefore an increasing roughness and altered etching behavior. The removal of the residual layer by laser irradiation has already been demonstrated and the aim of the present work is to further develop this process combination by reducing the residual layer thickness. For this purpose, etchings were performed with APPJ and the resulting residues were subsequently irradiated with an excimer laser (λ = 248 nm) with varying fluence. The samples were analyzed by white light interferometry, scanning electron microscopy, and energy dispersive X-ray spectroscopy. In the fluence range of 0.3-0.6 J·cm⁻² the residual layer can be removed without damaging the glass ceramic surface. EDX measurements show similar results for the laser-cleaned regions and an untreated Zerodur reference indicating that the residual layer can completely be removed.