Super-resolution Interference Lithography using Photochromic Photoresists: Towards bulk volume nanopatterning

Inspired from Stimulated Emission Depletion microscopy, two-color photolithography utilizes optically switchable excitation and inhibition pathways for nanopatterning with feature-sizes below the diffraction limit. However, the vast majority of such systems developed thus far, are limited to point-by-point serial writing. Here, we utilize the non-equilibrium kinetics of photochromic spirothiopyran monolayers to develop a super-resolution interference lithography scheme and demonstrate large area nanopatterning with feature sizes below 100 nm using a 2 W 532 nm laser. Extending this technique to the third dimension for nanopatterning in thick photoresists requires overcoming significant challenges due to the multiple process parameters that need to be optimized. In order to facilitate this, we develop an efficient electromagnetic (EM) perturbation theory approach that facilitates fully coupled simulations of EM and chemical kinetics to quantitatively analyze the influence of time dependent optical dynamics such as absorption, diffraction, and intensity modulation on the resist chemical kinetics. This ability to compute the coupled optical and chemical dynamics of such systems allows for the design of optimized exposure strategies for parallel nanopatterning in thick resists.