Multiscale Simulation Approach on Sub-10 nm Extreme Ultraviolet Photoresist Patterning: Insights from Nanoscale Heterogeneity of Polymer

Abstract

We developed a multiscale model that integrates density functional theory (DFT), molecular dynamics (MD), and the finite difference method (FDM) to reflect the heterogeneous spatial distribution of the material ingredients on sub-10 nm photoresist (PR) pattern fabrication using extreme ultraviolet lithography (EUVL). It allowed the exploration of phototriggered chemical reactions at the molecular level, including photoacid generator (PAG) dissociation, acid diffusion-coupled deprotection, and solubility switching of individual polymer chains. To quantify the progress of the deprotection, a protection ratio of each pendant group was tracked to distinguish the dissoluble PR chains from the developer as the process time elapsed. Deprotection was shown to preferentially occur in the pendant group adjacent to the acid molecule (<0.74 nm), which determined the chemical gradient and solubility switching trend of the PR chains. Based on the full description of the phototriggered chemical reaction, the morphology of the PR line pattern was predicted after wiping out the dissoluble chains. We particularly examined the PAG loading effect (5.68−30.12 wt %) on the line edge roughness (LER) of the PR pattern and predicted the LER inversion phenomenon at the critical threshold PAG concentration, which qualitatively agreed with the experimental observations. Such a LER trend due to PAG loading was explained by the reciprocal interaction between the homogeneous packing of the acid from the dissoluble PR chains and the acid clustering behavior. The variation of the homogeneity of the deprotection in each pendant group was verified as a function of PAG concentration, which rationalized the existence of the reciprocal interaction.

Selective Dissolution Resistance Control of EUV Photoresist Using Multiscale Simulation: Rational Design of Hybrid System

“…A positive-tone CAR, poly­(hydroxystyrene- co -[ tert -butoxy­carbonyl]­oxystyrene), or P­(HOSt- co -tBOCSt), which has been commercially used in industry, was constructed in a computational model. The photoacid generator (PAG), triphenylsulfonium triflate (TPS-tf), was loaded by as much as 10 wt % of the resist, which showed the best LER performance among different amounts of PAGs in our previous study . To simplify the calculation, a quencher was not considered, and water was applied as an aqueous developer.…”

“…We model the all-atom MD unit cell of the PAG-blended P­(HOSt- co -tBOCSt) resist following the cell construction scheme suggested by our previous work, which involves statistical ensemble dynamics for energetically favorable structures. Atomistic modeling and MD simulation were performed with the Materials Studio 2016 program package, and a polymer consistent force field (PCFF) was applied to describe the intra- and intermolecular interactions of the PR mixture.…”

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

“…Phenomena of these stochastic events are LER, LWR, and stochastic defects such as pinching and bridges [16]. Compared to previous LER modeling of ArF resists, precise EUVL process modeling of LER has been a hot issue [17][18][19][20]. The fin and gate critical dimension (CD) LERs of FinFET devices can seriously degrade performance and yield [21,22].…”

Molecular Modeling of EUV Photoresist Revealing the Effect of Chain Conformation on Line-Edge Roughness Formation

“…Rarely has the physical description of polymer chains and their movements been reported. Recently, Kim et al [25][26][27] studied the mechanism of photochemical reactions in an EUV photoresist matrix and the resulting pattern edge morphology with atomic molecular dynamics simulation, although time and length scales are relatively short and small due to the nature of the simulations. Ideally, EUV photoresist simulations should involve the modeling of relevant components, explicitly polymer chains and additives, with a good understanding of complex physical and chemical reaction occurring under the lithographic conditions, at dimension and time scales relevant for patterning.…”