Excimer-laser ablation and etching

The characteristics of excimer lasers and the nature of ablation and etching processes are described. The two kinds of laser ablation mechanisms, thermal and electronic, are discussed. Thermal processes all rely on an intense laser pulse to heat a surface very rapidly. Electronic mechanisms do not rely on heating. Two of these quantum-type processes have been discussed widely. In the first, laser photons directly excite and break the bonds of the solid, causing ejection of material. In the second, photoexcitation creates electron-hole pairs, the potential energy of which can be coupled directly into kinetic energy of the atoms via a radiationless process. The energized atoms are able to overcome the surface binding energy, and again material is ejected. Pulsed laser etching has many of the same physical-interaction mechanisms as laser ablation but requires an active chemical medium to be in contact with the solid because laser-induced chemical reactions serve as the driving force for material removal. Issues that must be addressed prior to the successful implementation of an excimer-laser fabrication tool are discussed. The use of patterned beams for direct patterning of surfaces is considered. Microelectronic applications suitable for excimer-laser ablation and etching are examined.<>