Surface morphology and sub-surface damaged layer of various glasses machined by 193 nm ArF excimer laser

摘要

Owing to the high bonding energy, most of the glasses are removed by photo-thermal rather than photo-chemical effectrnwhen they are ablated by the 193 or 248nm excimer lasers. Typically, the machined surface is covered by re-depositedrndebris and the sub-surface, sometimes surface as well, is scattered with micro-cracks introduced by thermal stressrngenerated during the process. This study aimed to investigate the nature and extent of the surface morphology and subsurfacerndamaged (SSD) layer induced by the laser ablation. The effects of laser parameters such as fluence, shot numberrnand repetition rate on the morphology and SSD were discussed. An ArF excimer laser (193 nm) was used in the presentrnstudy to machine glasses such as soda-lime, Zerodur and BK-7. It is found that the melt ejection and debris depositionrntend to pile up higher and become denser in structure under a higher energy density, repetition rate and shot number.rnThere are thermal stress induced lateral cracks when the debris covered top layer is etched away. Higher fluence andrnrepetition rate tend to generate more lateral and median cracks which propagate into the substrate. The changes ofrnmechanical properties of the SSD layer were also investigated.