Radiation Chemistry in Chemically Amplified Resists

Abstract

Historically, in the mass production of semiconductor devices, exposure tools have been repeatedly replaced with those with a shorter wavelength to meet the resolution requirements projected in the International Technology Roadmap for Semiconductors issued by the Semiconductor Industry Association. After ArF immersion lithography, extreme ultraviolet (EUV; 92.5 eV) radiation is expected to be used as an exposure tool for the mass production at or below the 22 nm technology node. If realized, 92.5 eV EUV will be the first ionizing radiation used for the mass production of semiconductor devices. In EUV lithography, chemically amplified resists, which have been the standard resists for mass production since the use of KrF lithography, will be used to meet the sensitivity requirement. Above the ionization energy of resist materials, the fundamental science of imaging, however, changes from photochemistry to radiation chemistry. In this paper, we review the radiation chemistry of materials related to chemically amplified resists. The imaging mechanisms from energy deposition to proton migration in resist materials are discussed.

Estimation of resist sensitivity for extreme ultraviolet lithography using an electron beam

“…8 A standard resist pattern formation model of EUV CARs including radiation chemistry was proposed by Kozawa et al (2001). 9 Based on this model, the RLS trade-off problem of EUV resists has been improving steadily due to worldwide research efforts. This approach is now reaching the physical limit of the model, thus novel processes and materials for resist sensitivity enhancement are necessary to solve the RLS trade-off problem.…”

“…The difference between EB and EUV resists is the energy absorption processes. [7][8][9] The EB-and EUV-induced radiation chemistry in CARs has been discussed from the perspective of the configuration of spurs, acid yield, and acid distribution. 10 Recently our research group found that the resist sensitivity in the EUV/soft X-ray region can be estimated from the exposure results at any wavelength in this region 11,12 and also from the exposure results for EB.…”

Theoretical Study of Ionization of Polymers for EUV Resist

“…From Figs. 7-8, we found poly(4-hydroxy styrene) has less energy barrier of ionization than poly(acrylic acid) , which coincides with more unstable radical cations of poly(acrylic acid) [14,15]. Figures 9 and 10 shows the decrease of electrons on substituent before and after ionization of poly(4-hydroxy-2,3,5,6-tetra substituted styrene) and poly(α-substituted acrylic acid), respectively.…”

“…Also the barrier energy does not depend on the ring number. Though the radical cation after ionization generates at the side-chain of the polymer [15], the ring ester does not affect the degree of ionization. Figure 25 shows the energy barrier of poly(methacrylic acid) polymers of the sensitization unit.…”

Modeling and Simulation of Line Edge Roughness for EUV Resists

“…Simulation parameters are described in Table 2. LER is inversely proportional to the concentration gradient of the molecules that determine the solubility of the resist (chemical gradient) [13,14]. Since the LER of resist processes is determined by various chemical components during resist processes, LER equations can be assumed that [ ] where…”