Unraveling the relative impact of material and optical stochastic effects on EUV LWR

Abstract

Extreme ultraviolet (EUV), with a 13.5 nm wavelength and 92 eV, produces high-resolution patterns but becomes more sensitive to stochastic effects because of its lower photon density compared to ArF and KrF, which have energies less than 10 eV. Therefore, controlling the stochastic effect is getting attention as EUV becomes mandatory to obtain ultrafine patterns. Unfortunately, various stochastic terms come from mask roughness, light-source, and photoresist materials, but each stochastic term is entangled and hard to decouple experimentally. Herein, we performed pattern shape simulation, separated each stochastic effect, and obtained patterns. Among the mask pattern roughness, photon-induced optical stochastics, and photoresist-induced material stochastics, material stochastics shows the most significant improvement on pattern break risk (2.5 nm widened failure-free window). In addition, the dispersion of photons caused by optical stochastic effects or mask pattern roughness plays a role in offsetting the excessive degradation of patterns due to material stochastic effects. Our simulation-based approach clarifies the role of each stochastic effect in pattern formation and guides process conditions and the novel photoresist development.