PAG Study in EUV Lithography

Abstract

Extreme Ultraviolet (EUV) has already achieved the initial requirements for 32 nm DRAM half pitch lithography rule and is known as one of the most promising next generation lithography techniques to be realized for 22 nm patterning technology though strict requirements for the power of the light sources, lithographic performance of the photoresist and the manufacturing and inspection of masks are still remaining,.In this report, we investigated the photolithographic characteristics of Photoacid Generator (PAG) additive approach in EUV lithography with different polymer platforms and sulfonium-type PAGs compared with other exposure techniques to understand the relationship between lithography results and photoresist materials. Four different sulfonium nonafluorobutanesulfonate; triphenylsulfonium nonafluorobutanesulfonate (TPS), tri(4-methoxy-3,5-dimethylphenyl) sulfonium nonafluorobutanesulfonate (MDP), tri(4-methoxy-3-methylphenyl)sulfonium nonafluorobutanesulfonate (MMP) and tri(4-methoxy-3-phenylphenyl)sulfonium nona-fluorobutanesulfonate (MPP) were employed as PAG in order to study the fundamental properties, such as sensitivity, photo-efficiency, lithographic performance , in the two different model formulations, poly(hydroxystyrene) (PHS) type and poly(methacrylates)-type, under three different exposures of 193 nm (ArF), Electron Beam (EB) and EUV.

EUV-induced activation mechanism of photoacid generators: key factors affecting EUV sensitivity

“…1) and experimental data from Ref. 10. -2c, we checked the linear dependence of experimental KrF exposure Dose on the LUMO, Band gap, and pKa parameters, respectively.…”

“…Asakura et al [10] measured the Dose under KrF, EB, and EUV exposure on four different three-fold symmetrically substituted TPSs PAG molecules, as shown in Figure 1. The Same nonafluorobutanesulfonic acid was used as a counter anion for PAG-cations, and propylene glycol methyl ether acetate (PGMEA) was used as a solvent.…”

Novel Mechanism-Based Descriptors for Extreme Ultraviolet-Induced Photoacid Generation: Key Factors Affecting Extreme Ultraviolet Sensitivity

“…Asakura and coworkers [10] measured three types of the dose-to-size under DUV(ArF) and EUV exposure of four different PAG cations with three-fold symmetry, as shown in Figure 3. Nonafluorobutanesulfonate was the common counter anion of each PAG, and propylene glycol methyl ether acetate (PGMEA) was used as the casting solvent.…”

“…Calculated chemical properties of four TPSs (Figure 3) and actual ArF dose-to-clear (E 0 ) and EUV dose-to-size (E size ) (50 nm pitch line-and-space patterning) from Ref. [10]. Table 1 lists the DFT-calculated properties, including LUMO, band gap energies, and the experimental ArF and EUV exposure dose of PAG cations in Figure 3 from Asakura et al [10].…”

“…Herein, we targeted triphenylsulfonium (Ph 3 S + , TPS) cation, a conventional PAG cation, and its derivatives with symmetrically and unsymmetrically substituted functional groups, as shown in Figure 3. We first tried to reveal the effects of conventional calculated properties (HOMO, LUMO, band gap, pKa) of TPS-based cations on the EUV exposure dose based on the published experimental data (Asakura et al) [10]. Next, we investigated the entire photo-reaction mechanism of TPS cations under EUV exposure in order to determine the key parameters of the acid generation and EUV exposure dose.…”