Tailoring polymer microstructure for the mitigation of the pattern collapse in sub-10 nm EUV lithography: Multiscale simulation study

Abstract

Photoresist (PR) nanopatterning using extreme-ultraviolet-lithography (EUVL) drives significant advances in integrated-circuit downsizing; however, sub-10 nm nodes severely suffer from collapse in the rinsing process (structural rigidity ↓, capillary force ↑ in denser line patterns). To mitigate collapse, we propose a new type of photoresist, hybrid material, with delicate polymer microstructure across the exposure boundary; a blend of linear chains for exposed domain and crosslinked network for masked area. This hybrid system is synthesized in a computational model through exposure-bake-curing process that generates a steep chemical gradient at the exposure boundary of polymer and triggers selective crosslinking reaction on the protected functional groups. The crosslinked structure is formed exclusively for the protection group-rich unexposed region; thus, the chemical joints tightly anchor the masked chains in aqueous solution, leading to nanoscale smoothing on the interfacial surface. Moreover, chemical linkage on the residual chains contributes to force delivery on the polymer matrix under macroscopic strain. Among the candidate materials, the hybrid resist incorporating a bicyclic crosslinker exhibits the best load transfer efficiency (E 101.4% ↑) and uniform interfacial surface (roughness 26.4% ↓), which significantly alleviates mechanical deformation and extends the critical aspect ratio of the pattern over the neat system. © 2020 Elsevier B.V.