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 hi gh fluences. The polymers can be divided into three groups, i.e., polymers containing triazene and ester groups, the same polymers without the triazen e group, and polyimide as reference polymer. At high fluences, similar abla tion parameters, i.e., etch rates and effective absorption coefficients, we re obtained for all polymers. The main difference is the absence of carl,on deposits for the designed polymers. At low fluences, very pronounced diffe rences are detected. The polymers containing the photochemically most activ e group (triazene) exhibit the lowest threshold of ablation and the highest etch rates, followed by the designed polyesters and then polyimide. Neithe r the linear nor the effective absorption coefficients reveal a clear influ ence on the ablation characteristics. The thermal properties of the designe d polymers also have only minor influence on the ablation activity. The amo unt of detected gaseous products follows the same trend as the ablation act ivity, suggesting a combined mechanism of photochemical decomposition and v olume increase for the designed polymers. The different behavior of polyimi de might be explained by a pronounced thermal part in the ablation mechanis m.