Ablation characteristics of material by excimer laser under different gas pressure and species

Abstract

In order to discuss ablation characteristics of materials by excimer laser, beam-plume(plasma) interaction was analyzed. In excimer laser processing, plasma is produced at delay time of 3-25ns and expands up to the height of 0.2-0.4mm during laser pulse, of which absorption coefficient is 2-15mm−1. Incident laser beam is absorbed by the laser-induced plasma at later part of the laser pulse. A plasma absorption model where plasma expands vertically was developed, and by using the model effect of beam absorption and beam scattering on processing phenomena was estimated. Non-umiform plasma is produced by plasma expansion, and thereby the depth of drilled hole becomes non-uniform at hole edge. At later part of laser pulse, small particles are produced in plume and scattering of incident beam is occured. Although total energy of scattered beam is much smaller than that of absorbed beam by plasma, the small particles deposites around processed area as debris. Volume of debris decreases under low gas pressure or light gas species such as He.In order to discuss ablation characteristics of materials by excimer laser, beam-plume(plasma) interaction was analyzed. In excimer laser processing, plasma is produced at delay time of 3-25ns and expands up to the height of 0.2-0.4mm during laser pulse, of which absorption coefficient is 2-15mm−1. Incident laser beam is absorbed by the laser-induced plasma at later part of the laser pulse. A plasma absorption model where plasma expands vertically was developed, and by using the model effect of beam absorption and beam scattering on processing phenomena was estimated. Non-umiform plasma is produced by plasma expansion, and thereby the depth of drilled hole becomes non-uniform at hole edge. At later part of laser pulse, small particles are produced in plume and scattering of incident beam is occured. Although total energy of scattered beam is much smaller than that of absorbed beam by plasma, the small particles deposites around processed area as debris. Volume of debris decreases under low gas pressure or...