Sulfonium Salt Resist Composition Suppressing Acid Diffusion
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Solution Overview
Problem
Conventional photoacid generators used in resist compositions for microfabrication fail to adequately suppress acid diffusion, leading to degradations in lithography properties such as contrast, mask fidelity, and pattern rectangularity, especially as circuit line widths reduce and exposure light wavelengths decrease.
Innovation Solution
A sulfonium salt with a specific structure is used as a photoacid generator in a resist composition, minimizing acid diffusion and improving lithography properties like exposure latitude, mask error factor, and line width roughness when processed by KrF excimer laser, ArF excimer laser, EUV, or EB lithography.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional photoacid generators are used to achieve high sensitivity in resist composition, then exposure sensitivity is improved, but acid diffusion increases leading to degradation in pattern precision and mask fidelity
Solution Approach 1:
The patent changes the chemical structure parameters of the photoacid generator by introducing a specific sulfonium salt structure with a sulfonium cation containing a nitrogen-containing six-membered aromatic ring and a perfluoroalkanesulfonate anion. This structural parameter change reduces acid diffusion while maintaining high sensitivity, resolving the contradiction between pattern precision and acid diffusion.
Solution Approach 2:
The patent creates a composite photoacid generator system combining a specific cation structure (with nitrogen-containing aromatic ring) and perfluoroalkanesulfonate anion. This composite structure achieves both high sensitivity and reduced acid diffusion, simultaneously improving pattern precision without sacrificing exposure sensitivity.
2Productivity
If circuit line widths are reduced to achieve higher integration, then device integration is improved, but acid diffusion degradation becomes more severe affecting lithography properties
Solution Approach 1:
The patent modifies the photoacid generator parameters by using a sulfonium cation with basicity carefully controlled through the nitrogen-containing aromatic ring structure. This parameter optimization enables reduced acid diffusion that is critical for maintaining lithography properties at smaller circuit line widths, supporting higher device integration.
3Measurement precision
If exposure light wavelength is decreased to achieve finer patterns, then pattern resolution is improved, but acid diffusion impact on mask fidelity increases
Solution Approach 1:
The patent changes the photoacid generator structure to a sulfonium salt with perfluoroalkanesulfonate anion, which generates acids with reduced diffusion characteristics. This parameter change in acid behavior enables better mask fidelity maintenance even when using shorter exposure wavelengths for finer pattern resolution.
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 effectively suppresses acid diffusion, enhancing lithography performance by improving exposure latitude, mask error factor, and line width roughness, thereby supporting precise micropatterning and maintaining sensitivity.
Implementation Method 1
a sulfonium salt having a formula (1) as a photoacid generator, wherein acid diffusion is minimized
Data Source
AI summary
On use of a sulfonium salt of specific structure as PAG, acid diffusion is suppressed. A resist composition comprising the sulfonium salt forms a pattern with improved lithography properties including EL, MEF and LWR when processed by lithography.