Chemically Amplified Resist Composition with Bulky Sulfonium Salt Regulator
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Solution Overview
Problem
Chemically amplified resist compositions face challenges in minimizing line edge roughness (LER) due to uncontrolled acid diffusion during high-energy radiation exposure, affecting the resolution and uniformity of patterns in semiconductor processing.
Innovation Solution
A chemically amplified resist composition incorporating a sulfonium salt with a specific general formula, which acts as an acid diffusion regulator, is used in conjunction with a polymer that becomes soluble in alkaline developers upon acid exposure, minimizing LER by controlling acid diffusion and generating a carboxylic acid with low acidity to prevent unwanted deprotection reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a photoacid generator is used to deprotect acid labile protective groups in positive resist compositions for EB and EUV lithography, then the sensitivity of the resist film is improved, but uncontrolled acid diffusion occurs causing degradation of line edge roughness and lowering of in-plane uniformity
Solution Approach 1:
The patent introduces an acid diffusion regulator as an intermediary substance that mediates between the photoacid generator and the acid labile protective group. The regulator controls the diffusion of generated acid through the resist film, preventing uncontrolled spread while still allowing sufficient acid to reach and deprotect the intended regions, thus resolving the contradiction between sensitivity and line edge roughness
Solution Approach 2:
The patent modifies the chemical parameters of the resist composition by selecting specific combinations of photoacid generators, acid diffusion regulators, and base polymers with controlled acid diffusion characteristics. By adjusting the pKa values and diffusion coefficients of the acid-regulator system, the patent optimizes the balance between acid generation efficiency and diffusion control to achieve both high sensitivity and low line edge roughness
2Manufacturing precision
If acid diffusion is controlled to improve line edge roughness, then manufacturing precision is improved, but the deprotection reaction may not occur sufficiently in exposed regions
Solution Approach 1:
The acid diffusion regulator serves as a controlled intermediary that allows acid to diffuse to the necessary extent for complete deprotection while preventing excessive diffusion. The regulator creates an optimal diffusion pathway that ensures sufficient acid reaches all exposed regions for complete deprotection, maintaining deprotection efficiency while controlling line edge roughness
Solution Approach 2:
The patent adjusts the chemical parameters of the acid-regulator system, specifically selecting regulators with appropriate pKa values and diffusion coefficients. By optimizing these parameters, the patent ensures that acid diffusion is controlled to the precise degree needed - enough to achieve complete deprotection in exposed regions but not so much that it degrades line edge roughness
Data Source
AI summary
A resist composition is provided comprising (A) a carboxylic acid sulfonium salt whose anion moiety has a bulky structure of arenecarboxylate in which secondary or tertiary carbon atoms bond at both ortho-positions relative to the carbon atom in bond with carboxylate, as an acid diffusion regulator and (B) a polymer which is decomposed under the action of acid to increase its solubility in alkaline developer. When processed by EB or EUV lithography, the resist composition exhibits a very high resolution and forms a pattern with minimal LER.