Fluorinated Copolymer Resist Inhibiting Pattern Collapse

The patent introduces fluorine atoms into the polymer structure by replacing hydrogen atoms with fluorine atoms in specific positions (R1, R2, R5, R6 groups). This chemical parameter change fundamentally alters the polymer's properties: fluorine atoms increase liquid repellency and reduce surface energy, preventing developer and rinse liquid from wetting the resist pattern surfaces, thereby eliminating capillary forces that cause pattern collapse during development and rinsing

The patent creates a composite polymer structure by copolymerizing fluorinated monomers with conventional resist monomers (α-methylstyrene and/or methyl α-chloroacrylate). This composite approach combines the high sensitivity and main chain scission properties of conventional positive resists with the liquid repellency and pattern stability provided by fluorinated groups, achieving both high sensitivity and pattern collapse resistance simultaneously

The patent applies fluorine atoms locally at specific positions on the polymer chain (R1, R2, R5, R6 groups) rather than throughout the entire structure. This localized fluorination provides sufficient liquid repellency for pattern stability while preserving the bulk polymer's main chain scission properties and sensitivity. The fluorinated groups act as surface-modifying entities that do not interfere with the radiation response of the polymer backbone

The patent optimizes the fluorine content and molecular weight parameters to balance pattern stability and sensitivity. By controlling the degree of fluorination and selecting appropriate molecular weights, the patent achieves a parameter regime where both pattern collapse resistance and high sensitivity are simultaneously realized, transforming the trade-off into a synergistic relationship