Negative Resist Composition for EUV Lithography
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Solution Overview
Problem
In EUV lithography, forming patterns with pitches shorter than the exposure wavelength is challenging due to low dissolution contrast and image blur issues caused by acid diffusion in negative resist materials, which affects the resolution and line width roughness (LWR) of microelectronic devices.
Innovation Solution
A negative resist composition comprising a base polymer, a sulfonium salt with at least two polymerizable double bonds as a quencher, and an acid generator capable of generating a fluorinated sulfonic acid, which reduces acid diffusion and enhances dissolution contrast during organic solvent development, thereby improving resolution and LWR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If chemically amplified resist compositions are designed to enhance sensitivity and contrast by acid diffusion, then sensitivity and contrast are improved, but image blur occurs due to acid diffusion
Solution Approach 1:
A crosslinker is introduced as an intermediary substance that mediates between the acid diffusion process and the polymer structure. The crosslinker reacts with polymer chains to form a crosslinked network that confines acid diffusion while maintaining the chemically amplified resistance mechanism, thus resolving the contradiction between enhanced contrast and image blur
Solution Approach 2:
The resist composition is formulated as a composite material containing polymer, acid generator, and crosslinker components. This composite structure enables simultaneous achievement of high sensitivity (through chemical amplification), high contrast (through controlled acid diffusion), and sharp images (through crosslinking-induced acid confinement)
2Measurement precision
If a crosslinker capable of inducing reaction between polymer molecules is used in negative resist material, then dissolution contrast is improved, but swell occurs due to penetration of developer between partially crosslinked polymer segments
Solution Approach 1:
Crosslinking is performed preliminarily during the baking process before developer application. This preliminary crosslinking action creates a sufficiently dense network structure that prevents developer penetration and subsequent swelling, while still allowing the crosslinker to provide dissolution contrast enhancement
3Measurement precision
If crosslinking is performed in negative resist material, then dissolution contrast is enhanced, but pattern collapse and degradation of CDU or edge roughness occur
Solution Approach 1:
The crosslinking parameters (temperature, time, crosslinker concentration) are optimized to achieve complete crosslinking without excessive swelling. The baking conditions are specifically controlled to ensure the crosslinked network forms with appropriate density and uniformity, preventing pattern collapse while maintaining high dissolution contrast
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 resist composition achieves high resolution and reduced LWR, along with improved critical dimension uniformity (CDU), effectively addressing the limitations of existing negative resist materials in EUV lithography.
Implementation Method 1
an acid generator capable of generating a fluorinated sulfonic acid
Implementation Method 2
a sulfonium salt with at least two polymerizable double bonds as a quencher
Implementation Method 3
image blurs due to acid diffusion become a problem
Data Source
AI summary
A negative resist composition is provided comprising a base polymer, a quencher in the form of a sulfonium salt of a weaker acid than a sulfonic acid which is fluorinated at α- and/or β-position of the sulfo group, the sulfonium salt having at least two polymerizable double bonds in the molecule, and an acid generator capable of generating a sulfonic acid which is fluorinated at α- and/or β-position of the sulfo group. The resist composition adapted for organic solvent development exhibits a high resolution and improved LWR or CDU.