Laser-induced back-side wet etching of fused silica with an aqueous solution containing organic molecules

The laser-induced back-side wet etching of fused silica with aqueous solutions of pyranine (8-hydroxy-1,3,6-pyrenetrisulfonic acid trisodium salt) is reported. KrF and XeF excimer lasers were employed as light sources. Well-defined line-and-space and grid micropatterns, free of debris and microcracks, were obtained. Compared with other organic solutions, the aqueous pyranine etching medium etches more slowly but produces a higher quality etched surface. With the KrF laser, the etch rate ranged from 0.02 to 0.12 nm pulse(-1), depending on the dye concentration and the fluence of the laser. The etch rate decreased dramatically when the XeF laser was employed, which was partially attributed to the lower absorption efficiency of the aqueous pyranine solution at the XeF laser wavelength.