Applied Surface Science, Vol.208, 199-204, 2003
Etching of fused silica and glass with excimer laser at 351 nm
The etching of solid surfaces at the interface to liquids is a new promising method for micro-machining of transparent materials. To extend the method to additional materials the pulsed radiation of a XeF-excimer laser (351 nm) was used for etching different types of glass (Coming Inc.: Pyrex, 7059 and Schott Group: D263, AF45) and fused silica for comparison. The etch rates of the investigated materials increase almost linear at low laser fluences. Threshold fluences for glass as low as 0.5 J/cm(2) and etch rates from 6 to 10 nm per pulse at 1 J/cm(2) have been determined. The etch rate and the threshold fluence depend also on the used liquid, consisting of a solvent (acetone, toluene) and a certain concentration of dissolved pyrene, but only little on the glass type. Due to the low etch rate typically very smooth surfaces are achieved. The surface roughness measured by AFM on Coming 7059-glass at an etch depth of 3.7 mum is as low as 4 nm. Contrary to the other glasses the surface roughness of Pyrex. is much higher and dominated by typical arbitrary etch pits with micron dimensions. Comparing the etching of fused silica at a wavelength of 248 and 351 run the used solution influences both the etch threshold and the etch rate. In accordance to earlier investigations at 248 nm also XeF-laser etching at the interface to an absorbing liquid results in a good surface quality, well defined patterns and almost no debris deposition. Thus, this technique is a good candidate for precise micro-machining applications. (C) 2002 Elsevier Science B.V. All rights reserved.