The comparison of ITO ablation characteristics using KrF excimer and Nd:YGA laser

초록

We studied to develop ITO (Indium Tin Oxide) thin films ablation with a pulsed type KrF eximer(λ=248㎛) and Nd:YGA laser(λ=262 andλ=532㎛) required for the electrode patterning application in flat panel display into small geometry on a large substrate area. The threshold fluence for ablating ITO on glass substrate is about 0.1 J/ . Through the optical microscope measurement the surface color of the ablated ITO is changed into dark brown due to increase of surface roughness and transformation of chemical composition by the laser light using KrF eximer laser. And the XPS analysis showed that the relative surface concentration of Sn and In were essentially unchanged(In:Sn=5:1)after irradiating the KrF eximer laser. It has been reported that ripple like structure was formed by 2nd harmonic Nd:YLF laser (=523㎛). But in case of using 2nd harmonic Nd:YGA laser,in our study,the ablated films have well patterned and the shape is almost clean even through by-product exists in the vicinity of the etched surface region. But the films were damaged at the same laser fluence using 4th harmonic Nd:YGA laser. We will discuss this cause in terms of phton energy and the film thickness used,repetition rate and beam scan speed of each laser.