Excimer laser ablation of novel triazene polymers: influence of structural parameters on the ablation characteristics

Abstract

Novel photopolymers based on the triazene chromophoric group have been developed. Structuring by XeCl* excimer laser irradiation at 308 nm results in ablation craters with clean contours and sharp edges; diffractionlimited resolution of =0.4 pm is achieved. A prominent feature of the triazene polymers is the complete absence of solid debris around the edges of the ablation craters, which makes these materials attractive for applications in microelectronics. The dependence of the ablated depth per pulse on laser fluence is investigated and is related to the effective absorption coefficient and the quantum yield of photochemical decompostion of the polymers in solution. Other physicochemical and thermomechanical parameters of the polymers appear to be less influential on the ablation characteristics. The high fluence limit d,,, of the etch rate per pulse is found in the range between 2 and 3 pm for all investigated materials. On exposure to several high fluence laser pulses, an ejection of material has been observed from areas that are considerably larger than the incident laser beam. This effect may be due to either an explosive event or the generation of shock waves reflected at the sample substrate.