Etch Rates and Qualities

The most common parameters to characterize the ablation of polymers are the ablation rates at various fluences, the threshold fluence, and the effective absorption coefficient. These values and the quality of the achieved structures can give first indications about the mechanism of ablation. For this study various designed polymers (described in more detail below) and one reference polymer were selected. 

Introducing a functional ester group that enables selective photocrosslinking without destruction of the polymer backbone can improve the stability of the polymers without changing the sensitivity to direct laser structur- 

Physical Properties of the Polymers. All polymers in this study can be classified as highly absorbing polymers (etiin 8000 cm 1 at the irradiation wavelength of 308 nm), as shown in Table 1. Cross-linking reduced the absorption coefficient only slightly for the triazene-containing polymer, while for 

Ablation at High Fluences (0.5-10 ] cm 2). The etch rates (etch depth/pulse) at high fluences were calculated from linear plots of the etch depths vs pulse number at a given fluence. All plots were linear, showing no incubation behavior as expected for highly absorbing polymers. 

The ablation parameters, aeff (effective absorption coefficient) and Fth (threshold fluence) were calculated according to Eq. 1 [73, 130], 

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