Sulfonium Salt Resist Composition for EUV Lithography
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Solution Overview
Problem
Current chemically amplified resist compositions face challenges in controlling acid diffusion, leading to issues like line edge roughness and pattern degradation due to unwanted reactions in unexposed regions during high-energy radiation exposure, particularly in EB and EUV lithography.
Innovation Solution
A sulfonium salt with a specific structure that generates a bulky acid with controlled diffusion is introduced, incorporated into a resist composition, which includes polymers with acid labile groups and crosslinkers, to enhance pattern stability and resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional acid generators are used in chemically amplified resist compositions, then the resist can be exposed to high-energy radiation, but acid diffusion occurs leading to line edge roughness and pattern degradation
Solution Approach 1:
The patent modifies the molecular weight and structural parameters of the sulfonium salt to generate bulky acids with controlled diffusion characteristics. By changing the physical and chemical parameters of the acid generator, the patent achieves reduced acid diffusion while maintaining effective pattern exposure
Solution Approach 2:
The patent uses a composite resist composition containing sulfonium salt, polymer matrix with acid-labile groups, and crosslinking agents. This composite structure enables controlled acid diffusion and improved pattern fidelity by combining multiple functional components
2Productivity
If the resist film is made highly sensitive to reduce image-writing time, then throughput is maintained, but pattern profile stability deteriorates due to acid diffusion in unexposed regions
Solution Approach 1:
The patent incorporates crosslinking agents and acid-labile groups in the polymer matrix before exposure, creating a pre-configured structure that resists acid diffusion. This preliminary structural preparation prevents pattern degradation even when high sensitivity is required for fast throughput
Solution Approach 2:
The patent creates different functional zones within the resist composition: exposed regions undergo deprotection and dissolution, while unexposed regions maintain structural integrity through crosslinking and controlled acid diffusion barriers, achieving local differentiation of material properties
3Strength
If acid generators that generate strong acids are used to improve etching resistance, then etching resistance improves, but acid diffusion increases causing roughness and LER
Solution Approach 1:
The patent carefully selects the molecular weight and structural parameters of the sulfonium salt to generate acids with moderate strength but bulky size. This parameter optimization achieves sufficient etching resistance while the bulky structure limits diffusion and prevents line edge roughness
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 sulfonium salt-based resist composition achieves high resolution and minimal line edge roughness, maintaining pattern integrity even after prolonged exposure and development, with improved etching resistance and uniformity.
Implementation Method 1
a sulfonium salt having a general formula (1) which generates a sulfonic acid having a general formula (1a) in response to high-energy radiation or heat
Implementation Method 2
The major cause of such a change with time is diffusion of an acid generated upon exposure
Data Source
AI summary
A sulfonium salt of formula (0-1) is provided wherein W is alkylene or arylene, R01 is a monovalent hydrocarbon group, m is 0, 1 or 2, k is an integer: 0≦k≦5+4m, R101, R102 and R103 are a monovalent hydrocarbon group, or at least two of R101, R102 and R103 may bond together to form a ring with the sulfur atom, and L is a single bond, ester, sulfonic acid ester, carbonate or carbamate bond. A resist composition comprising the sulfonium salt as PAG exhibits a very high resolution when processed by EB and EUV lithography. A pattern with minimal LER is obtainable.