Fluorinated copolymer resists for high-resolution negative-tone lithography: Preparation and patterning performance

Area of Science:

• Materials Science
• Polymer Chemistry
• Nanotechnology

Background:

• Advanced lithography demands high-resolution and stable photoresists.
• Development of high-performance resist materials is critical for next-generation microfabrication.

Purpose of the Study:

• To design and synthesize a novel ternary copolymer photoresist (PTAF).
• To optimize PTAF preparation and investigate its properties and lithographic performance.
• To elucidate the negative-tone imaging mechanism of the PTAF system.

Main Methods:

• Synthesis of poly(tert-butyl methacrylate-co-adamantyl methacrylate-co-[trifluoroethyl methacrylate/1,1,1,3,3,3-hexafluoroisopropyl isobutyrate methacrylate]) copolymers (PTAF).
• Single-factor experimental design for condition optimization.
• Characterization of molecular weight distribution, thermal properties (T_d, T_g), and hydrophobicity.
• Electron-beam lithography (EBL) for performance evaluation and mechanistic studies.

Main Results:

• PTAF synthesized with narrow molecular weight distribution (PDI = 1.2-1.3) and M_n ≈ 4271 g mol^-1.
• Exhibits good thermal stability (T_d = 212°C, T_g = 105°C) and pronounced hydrophobicity.
• Achieved high-resolution patterns (16.5 nm linewidth) via intrinsic negative-tone behavior without external photoacid generators.

Conclusions:

• PTAF serves as a high-performance ternary copolymer photoresist platform.
• Fluorinated monomers initiate in situ acid generation, enabling polarity reversal and solubility switch.
• Provides valuable insights for designing polymer-based resists for advanced lithography, including EUV applications.