Direct writing in self-developing resists using low-power cw ultraviolet light

Direct writing of micron-sized features in self-developing photoresists is demonstrated using less than 1 mW of cw ultraviolet light at 257 nm. No energy density or intensity thresholds for ablation are observed. Ablation depth depends only on the deposited energy density and is independent of the rate of deposition; that is, the self-developing process is reciprocal. We have determined that an environment containing oxygen is necessary for complete self-developing; in the absence of O₂ the process is self-limiting. Patterns created in poly(methyl methacrylate) have been faithfully reproduced into silicon substrates using reactive-ion etching.