Cross-linking control during imprint for hybrid lithography

Abstract

Hybrid lithography combining thermal nanoimprint with optical lithography is an effective means to prepare structures with differing geometries (nanometer, micrometer) over large areas, e.g., for sensor applications. For the realization of this technique, the suitability of photoresists for this process has to be investigated. In case of negative tone resists, the cross-linking induced or provided by exposure may be amplified in the imprint step due to heating times in the minute range. As cross-linking may impede the imprint, a subtle adjustment of the exposure dose with respect to the imprint temperature envisaged is required for successful processing. With an imprint temperature of 100 °C, good results for hybrid lithography could be obtained with two commercially available negative tone resists: ma-N 405 and ARN 4410. The latter could successfully be used for a subsequent liftoff. The best results were obtained when the resists were exposed before the imprint step.

Resist reflow minimization via viscosity control by exposure

“…Earlier experiments 11 that evaluated dose curves for the same resist (thickness 400 nm and development time 3 min) provided the key data required. This result is much better than the one obtained previously 11 with a modified order of processing (scheme B). In our current study, it is found that a flood exposure of 80 mJ/cm 2 and a masked exposure of 140 mJ/cm 2 is already too high to develop the regions without masked exposure (only flood exposed), even with development times of 20 min.…”