Exposure dependence of the developed depth in nonadiabatic photolithography using visible optical near fields

We have developed new type of photolithography based on a nonadiabatic photochemical process that exposes an ultraviolet-photoresist using a visible optical near field. Investigating the exposure dependence of the developed depth using nonadiabatic photolithography, we found that the depth increased with the exposure threshold. To explain this result, the optical field intensity was simulated by using the finite-difference time-domain method. The evolution of the developed depth was proportional to the optical field intensity and its spatial gradient, agreeing closely with the simulated result that took into account the nonadiabatic processes. Another experimental result is to support our explanation, that in nonadiabatic photolithography, a component of the exposure progresses inside the photoresist.