Excimer laser lithography: Intensity-dependent resist damage

The absorption depths of Shipley AZ2400 and two Isofine e-beam resists P10 and PM20 have been measured with KrF (248 nm), KrCl (222 nm), and ArF (193 nm) excimer lasers. For all peak laser intensities at which the absorption depths were measured there was no evidence of reciprocity failure in the sensitivity response of the resists. At higher peak intensities the resists were damaged. The results show that the damage thresholds of these resists are sufficiently low that single-laser pulse exposures of thin films are not possible without damage occurring.