Cascade and cluster of correlated reactions as causes of stochastic defects in extreme ultraviolet lithography

Abstract

Background: Stochastic defects are becoming major concern in the future extreme ultraviolet (EUV) lithography as their probability P d exponentially increases with decreasing feature size and is highly sensitive to variations in process/mask conditions. Photon shot-noise and discrete/ probabilistic nature of materials have been blamed as their causes. Aim: We introduce models for relating P d to photon and resist statistics under various exposures and material conditions and analyze their impact in future EUV lithography. Approach: Three-dimensional reaction distribution is calculated by a fully coupled Monte Carlo simulation including discrete photon, photoelectron scattering, and resist stochastics. Then probability models predict P d from statistical data extracted from Monte Carlo results. Results: Stochastic defect generation is enhanced by cascade and/or cluster of correlated reactions among nearby polymers/molecules due to secondary electrons (SE)/acid diffusion and SEs generated along scattered photoelectron trajectories. P d decreases with increasing reaction density, suppressing effective image blur, and introducing quenchers, where reaction density is limited by SE, photoacid generator, and reaction site. Defect probability increases with decreasing target size for the same k1-factor, while strongly dependent on image slope and defocus. Conclusions: Our analyses suggest that applying EUV lithography to smaller target requires careful material choice, extremely precise process control, and further EUV power enhancement.

Bioinspired Algorithms for Multiple Sequence Alignment: A Systematic Review and Roadmap

“…In bioinformatics, MSA is a vital process essential for evolutionary research [14,15] and aids in predicting the structure and function of unidentified proteins [16,17]. The MSA problem primarily involves aligning multiple biological sequences and optimizing a specific statistic, such as the count of aligned bases [18].…”

Line-Edge Roughness from Extreme Ultraviolet Lithography to Fin-Field-Effect-Transistor: Computational Study

“…In exposure process in Figure 1, EUV photons are absorbed at random positions of an EUV resist due to exposure parameters such as local light intensity related to imaging system and resist absorption. Incident EUV light collides with an atom of an EUV resist and the atom emits photoelectrons in arbitrary directions through ionization process [13,15]. Each photoelectron moves and stops until its energy becomes lower than a certain threshold energy.…”

“…In addition, EUV photons contribute to fluctuation of acid generation and reaction with quenchers due to random location of PAG and quencher [13,14]. Therefore, during EUVL processes, stochastic EUV photons initiate random physical and chemical events in terms of multi-photon effect in frequency distribution and cascade and cluster of correlated reactions in special distribution [15]. Phenomena of these stochastic events are LER, LWR, and stochastic defects such as pinching and bridges [16].…”

Contribution of EUV resist counting statistics to stochastic printing failures

“…4, bridge failures have a size of ∼15 nm. In lieu of detailed theoretical molecular-scale analysis linking the internal length scales to the observed failure dimension, 9 as a simplification we adopt the 15-nm experimental value as the characteristic length scale for stochastic failures at 36-nm pitch and focus on the properties of individual volume elements (voxels) whose x, y, and z dimensions are of this characteristic length. This implicitly assumes the physicochemical effects that in aggregate produce a failure site are isotropic.…”