Study on deprotonation from radiation-induced ionized acrylate polymers including acid-generation promoters for improving chemically amplified resists

Abstract

The demand for improved performance of chemically amplified resists (CARs) is continually increasing with the development of extreme ultraviolet lithography. Acid-generation promoters (AGPs) increase the sensitivity of CARs by increasing the initial acid yield immediately after the exposure process. However, the detailed mechanism of acid-yield enhancement has not been clarified yet. Deprotonation from the ionized polymer (i.e., radical cations) is an important reaction to assess acid generation. In this study, we investigated the dynamics of the radical cations of methacrylate polymers and the effect of an AGP on deprotonation from the radical cations formed by ionizing radiation. We clarified that the promotion of deprotonation by the AGP is more effective for the polymer with lower deprotonation efficiency. In addition, a molecular-level approach using density functional theory and molecular dynamics calculations were carried out.

Sensitization of polymethacrylate resist with adding acid-generating promoters upon exposure to EUV light

“…We have previously shown that the initial acid yield prior to PEB can be increased by 10%-20% by adding 12 wt% DTS to P1-4. 32) The resist sensitivity increased 1.7 to 7.5 times more with 10 wt% DTS addition than without. This indicates that the effectiveness of DTS is greater than the degree of increase in the initial acid yield.…”

“…We have shown that the initial acid yield of the polymers is on the order of P4 > P3 > P2 > P1. 32) By contrast, EUV sensitivity is on the order of P1 > P4 > P3 > P2. Thus, P1 has the highest sensitivity despite its lower initial acid yield.…”

“…29) Moreover, in ArF lithography, the addition of di-p-tolyl sulfone (DTS) as an AGP to methacrylate polymers has been found to increase the initial acid yield. 32) In this study, we investigate the effect of adding DTS to an acrylate polymer on the EUV sensitivity and EB patterning. In addition, we use the quartz crystal microbalance (QCM) method to analyze the effect of DTS addition on the resist development process.…”

Chemical Structure–Physicochemical Property Relationships of Copolymers Utilizable for Negative-Tone Photoimaging via Chemical Amplification

“…The chemistry of CAR has been altered such that the mechanism for light-mediated solubility modulation became valid with different light sources including DUV and EUV. The CAR system has been optimized for lithographic techniques using KrF and ArF excimer lasers; however, in EUV lithography, one challenging issue still remains to be addressed: trade-off relationship among resolution, line edge roughness (LER), and sensitivity, the-so-called RLS trade-off. − Different chemistries have been proposed to resolve this issue; however, because of the strong compatibility of CARs with the current semiconductor device fabrication process, CAR still remains an important candidate for single-digit nanometer technical nodes with EUV lithography. − …”

Indium nitrate hydrate films as EUV resists by evaluating with 92-eV electron beam

“…2 The requirement of thin resists in EUV lithography further exacerbates the problem. One approach to improve CARs' performance in EUV is to add more photoacid generators in the resist, 3,4 which has limited success. Inorganic resists, in particular metal oxides, which are not used in DUV lithography are studied as potential EUV resists because elements such as metals, semimetals, and transition metals have larger EUV absorption cross-sections than carbon.…”