Ablation of silicon suboxide thin layers

Abstract

We investigate the ablation of SiO (x) thin films on fused silica substrates using single-pulse exposures at 193 nm and 248 nm. Two ablation modes are considered: front side (the surface of a film is irradiated from above) and rear side (a film is irradiated through its supporting substrate). Fluence is varied from below 200 mJ/cm(2) to above 3 J/cm(2). SiO (x) films of thickness 200 nm, 400 nm, and 600 nm are ablated. In the case of rear-side illumination, at moderate fluences (around 0.5 mJ/cm(2)) the ablation depth corresponds roughly to the film thickness, above 1 J/cm(2) part of the substrate is ablated as well. In the case of front-side ablation the single-pulse ablation depth is limited for all film thicknesses to less than 200 nm even at fluences up to 4 J/cm(2). Experimental results are discussed in relation to film thickness, fluence, and ablation mode. Simple numerical calculations are performed to clarify the influence of heat transport on the ablation process.