Acetal-Based Resist Compositions for ArF Lithography Resolution
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Solution Overview
Problem
Current resist materials for ArF excimer laser lithography face challenges in achieving high resolution and controlled acid migration, leading to issues like pattern density dependency and optical proximity effects, which hinder further miniaturization and resolution enhancement in semiconductor manufacturing.
Innovation Solution
Development of acetal compounds and polymers with specific chemical structures that form the basis of resist compositions, allowing for high-resolution micropatterning through controlled acid migration and improved mask fidelity, particularly suited for immersion photolithography using ArF excimer laser radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If strong acid type photoacid generator is used, then exposure dose can be reduced to relatively low level, but deactivation of generated acid by air-borne basic substances has large influence causing T-top pattern profile
Solution Approach 1:
The patent changes the chemical parameters of the acid labile protecting group from conventional types (tert-butoxycarbonyl, tert-butyl, 2-tetrahydropyranyl, 1-ethoxyethyl) to a specific acetal structure with formula (1). This new structure has different acid reactivity characteristics that reduce sensitivity to acid deactivation by air-borne basic substances while maintaining acceptable exposure dose levels, thereby improving pattern profile quality.
Solution Approach 2:
The patent uses a composite approach by combining the acetal compound of formula (1) with other resist composition components (base resin, acid generator, solvent) to create a formulated resist material. This composite formulation allows optimization of multiple parameters simultaneously, balancing exposure dose requirements with pattern profile quality and reducing the harmful effects of acid deactivation.
2Manufacturing precision
If 2-tetrahydropyranyl and 1-ethoxyethyl are used as protective groups, then resolution is improved due to high reactivity with acids, but thermal stability is poor and shelf stability is compromised
Solution Approach 1:
The patent modifies the chemical structure of the acid labile protecting group by introducing the specific acetal framework of formula (1) with variables R1-R4 and X1. This structural parameter change maintains the necessary acid reactivity for high resolution while improving thermal stability and shelf stability compared to conventional acetal groups like 2-tetrahydropyranyl and 1-ethoxyethyl. The specific substitution patterns in formula (1) provide enhanced stability without sacrificing resolution.
3Ease of manufacture
If conventional acid labile protecting groups are used, then resist material can be formulated, but noticeable line density dependency and optical proximity effect occur
Solution Approach 1:
The patent systematically changes the chemical parameters of the acid labile protecting group by using the acetal structure of formula (1) with specific substituent patterns (R1-R4, X1). This parameter change modifies the acid migration behavior and deprotection characteristics, thereby reducing line density dependency and optical proximity effects while maintaining ease of resist material formulation and processing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The acetal-based resist compositions demonstrate high resolution and minimized pattern density dependency, enabling precise micropatterning and improved mask fidelity in semiconductor manufacturing, addressing the limitations of existing resist materials.
Implementation Method 1
Migration of the acid occurs during PEB. Since chemically amplified resist materials depend on the function of the acid to act as a catalyst to promote deprotection reaction, moderate acid migration is necessary.
Implementation Method 2
the acid generated upon exposure triggers deprotection reaction on the base resin which proceeds during heat treatment following exposure (post-exposure bake or PEB)
Data Source
AI summary
An acetal compound of formula (1) is provided wherein R1 is H, methyl or trifluoromethyl, R2 is a monovalent C1-C10 hydrocarbon group, R3 and R4 are H or a monovalent C1-C10 hydrocarbon group, R2 and R3 may together form an aliphatic hydrocarbon ring, and X1 is a single bond or a divalent C1-C4 hydrocarbon group. A polymer comprising recurring units derived from the acetal compound is used as a base resin to formulate a resist composition which exhibits a high resolution when processed by micropatterning technology, especially ArF lithography.