Resist Composition Inhibiting Acid Diffusion for Lithography
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Solution Overview
Problem
The negative tone pattern forming process in lithography experiences significant CD shrinkage and profile changes due to acid diffusion during the post-exposure bake to development delay, leading to degraded lithography performance and inconsistent results.
Innovation Solution
A resist composition is developed that includes a specific compound to inhibit acid diffusion, combined with a resin that changes solubility in organic solvents under acid action and a photoacid generator, along with optional additives like hydrophobic fluoro-resins and nitrogen-containing compounds, to maintain pattern integrity during delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If off-line development system is used with delay between PEB and development, then flexibility in manufacturing process is improved, but CD shrinkage and pattern profile change increase
Solution Approach 1:
The patent applies preliminary action by incorporating a base resin that undergoes solubility modification during PEB in advance. The resin is pre-designed with acid-labile groups that react during PEB to alter solubility characteristics, so that when development occurs after any delay period, the pattern dimensions are already stabilized and resistant to acid diffusion effects.
Solution Approach 2:
The patent utilizes parameter changes by modifying the chemical structure of the base resin through acid-catalyzed reactions during PEB. The acid-labile groups (such as t-butoxycarbonyl or acetal groups) undergo chemical transformation that permanently changes the resin's solubility parameters, making the pattern dimensions insensitive to subsequent acid diffusion during delay periods.
2Ease of operation
If acid diffusion is allowed during PEB delay, then simple process operation is maintained, but lithography performance degrades due to CD shrinkage
Solution Approach 1:
The patent converts the harmful effect of acid diffusion during delay into a beneficial outcome. The acid generated during exposure, which would normally cause unwanted diffusion and CD shrinkage, is instead utilized to trigger the solubility modification reaction in the base resin during PEB. This ensures that the pattern is locked in with stable dimensions, and any subsequent acid diffusion during delay has minimal impact on final pattern fidelity.
3Adaptability or versatility
If conventional positive resist composition is used for organic solvent development, then existing process compatibility is maintained, but resolution and pattern fidelity are insufficient
Solution Approach 1:
The patent employs composite materials by creating a resist composition that combines a specifically designed base resin with acid-labile groups and a photoacid generator. This composite structure integrates the benefits of organic solvent development (process compatibility) with enhanced resolution and pattern fidelity (through the controlled solubility modification mechanism). The base resin provides structural integrity while the acid-labile groups enable precise pattern definition.
Data Source
Figure 1A~1C
AI summary
A pattern is formed by coating a resist composition comprising (A) a PPD inhibitor, (B) a polymer adapted to change its solubility in an organic solvent under the action of acid, (C) a photoacid generator, and (D) an organic solvent onto a substrate, baking, exposing the resist film, PEB, and developing in an organic solvent developer. The resist composition ensures to form a pattern in a consistent manner while inhibiting any CD shrinkage and pattern profile change due to a delay from PEB to development.