Novel laser ablation resists for excimer laser ablation lithography. Influence of photochemical properties on ablation

The ablation characteristics of various polymers were studied at low and high fluences. The polymers can be divided into three groups, i.e., polymers containing triazene and ester groups, the same polymers without the triazene group, and polyimide as reference polymer. At high fluences, similar ablation parameters, i.e., etch rates and effective absorption coefficients, were obtained for all polymers. The main difference is the absence of carl,on deposits for the designed polymers. At low fluences, very pronounced differences are detected. The polymers containing the photochemically most active group (triazene) exhibit the lowest threshold of ablation and the highest etch rates, followed by the designed polyesters and then polyimide. Neither the linear nor the effective absorption coefficients reveal a clear influence on the ablation characteristics. The thermal properties of the designed polymers also have only minor influence on the ablation activity. The amount of detected gaseous products follows the same trend as the ablation activity, suggesting a combined mechanism of photochemical decomposition and volume increase for the designed polymers. The different behavior of polyimide might be explained by a pronounced thermal part in the ablation mechanism.