The laser-induced backside dry etching (LIBDE) method has been developed by analogy with the well-known LIBWE technique for micromachining of transparent materials. In our experiments tin thin films were applied as absorbing layers and the dependence of the etch depth on the applied laser wavelength was investigated. Multipulse irradiation experiments at different wavelengths have also been carried out. A fused silica plate coated by a tin layer was used as a target. The metal film-transparent material interface was irradiated through the fused silica plate by the most frequently used nanosecond excimer laser beams: ArF (193 nm), KrF (248 nm) and XeCl (308 nm). It was found that the etch depth increased linearly with decreasing wavelength in investigated range. Multipulse investigations proved that the energy of the absorbed photons has a strong influence on the mechanism of LIBDE. The etch depth-pulse number curves showed saturation at 1500 mJ cm-2 applied laser fluence at around 2, 3 and 30 pulses for 308 nm, 248 nm and 193 nm wavelengths, respectively. This indicates that the effectiveness of multipulse LIBDE increases when the wavelength of the applied laser source is decreased in the UV range. XPS and spectroscopic ellipsometric analyses showed that formation and embedding of tin-oxides into the upper surface layer can be responsible for the shift of the saturation in the case of ArF as compared with the other studied wavelengths.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Acoustics and Ultrasonics
- Surfaces, Coatings and Films