4-Pyrone Ester Resist Suppresses Acid Diffusion

The patent changes the chemical composition parameters of the resist film by incorporating specific polymer components (poly-4-hydroxystyrene, poly-4-methoxystyrene) and acid generators (sulfonium salt, iodonium salt) with optimized ratios. This chemical parameter optimization enables the resist to maintain high sensitivity even when exposed to high-energy electrons at 50-100 kV accelerating voltages, resolving the contradiction between resolution improvement and sensitivity loss.

The patent uses a composite resist formulation combining multiple polymer components (poly-4-hydroxystyrene as base resin, poly-4-methoxystyrene as adhesive promoter) with acid generators and quenchers. This composite material approach creates synergistic effects where each component contributes to both sensitivity enhancement and resolution maintenance under high-energy electron beam exposure.

The patent introduces a quencher component as an intermediary substance that selectively interacts with diffusing acid. The quencher captures excess acid molecules that would otherwise diffuse and cause image blur, while allowing the beneficial acid-catalyzed amplification reaction to proceed in exposed regions. This mediator approach maintains both high sensitivity and sharp resolution.

The patent creates local quality differentiation within the resist film by using components with spatially selective functions: poly-4-hydroxystyrene provides acid diffusion control in the bulk, while poly-4-methoxystyrene enhances adhesion at the film-substrate interface. The acid generator is distributed uniformly but activates locally upon exposure, creating localized chemical changes that preserve image fidelity.

The patent optimizes the PEB temperature parameter to a specific range (90-110°C) that balances acid diffusion control and sensitivity maintenance. Within this optimized temperature window, the acid diffusion is sufficiently limited to preserve resolution while the thermal energy is adequate to maintain high sensitivity and contrast through efficient acid-catalyzed deprotection reactions.

The patent creates a micro-porous structure through the polymer network that provides pathways for controlled acid transport. This porous architecture allows acid to reach necessary reaction sites for sensitivity enhancement while the pore structure itself acts as a diffusion barrier that limits excessive acid spread, enabling resolution preservation without sacrificing sensitivity.