Sulfonium Salt Resist Composition for EUV Lithography
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Solution Overview
Problem
As feature sizes in microelectronic devices shrink, acid diffusion in resist compositions used in lithography leads to image blurring, requiring a balance between sensitivity, resolution, and edge roughness, which existing resist compositions struggle to maintain, especially at sub-45nm sizes.
Innovation Solution
A resist composition incorporating a sulfonium salt with a sulfonate anion bonded to an iodine atom and a sulfonium cation having specific hydrocarbylcarbonyl or hydrocarbyloxycarbonyl groups is developed, enhancing sensitivity and controlling acid diffusion to improve line width roughness (LWR) and critical dimension uniformity (CDU).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If acid diffusion is suppressed to improve resolution, then manufacturing precision improves, but sensitivity deteriorates
Solution Approach 1:
The patent changes the chemical parameters of the acid generator by using a sulfonium salt with a specific structure (formula 1) where the cation contains electron-withdrawing groups at positions 2 and 7. This structural modification alters the acid diffusion characteristics while maintaining high acid generation efficiency, thereby resolving the contradiction between resolution and sensitivity
Solution Approach 2:
The patent employs a composite acid generator system combining the sulfonium salt cation (formula 1) with specific anions (formula 2 or 3). This composite structure allows the cation to control acid diffusion through its electron-withdrawing groups while the anion provides stability and solubility, achieving both high resolution and sensitivity simultaneously
2Manufacturing precision
If acid diffusion is suppressed to improve resolution, then manufacturing precision improves, but edge roughness worsens
Solution Approach 1:
The patent modifies the chemical parameters of the acid generator by introducing electron-withdrawing groups (such as fluorine, chlorine, or cyano groups) at positions 2 and 7 of the sulfonium cation. This parameter change creates a balanced acid diffusion profile that maintains sharp pattern definition while ensuring sufficient acid distribution to maintain smooth edges
Solution Approach 2:
The sulfonium salt acts as an intermediary between the exposure light and the resist polymer. Its specific molecular structure (formula 1) mediates the acid generation process, controlling the diffusion distance and distribution pattern to achieve both high resolution and smooth edge profiles
3Productivity
If sensitivity is improved by increasing acid diffusion, then productivity improves, but manufacturing precision deteriorates
Solution Approach 1:
The patent changes the chemical structure parameters of the acid generator to achieve high acid generation efficiency without excessive diffusion. The sulfonium cation (formula 1) with electron-withdrawing groups at positions 2 and 7 generates sufficient acid for high sensitivity while the electron-withdrawing nature limits diffusion distance, maintaining 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 resist composition achieves high sensitivity, improved LWR, and CDU, maintaining resolution and process margin in both positive and negative tone patterns, effectively addressing the challenges of acid diffusion and image blurring.
Implementation Method 1
Iodine atoms have strong absorption for EUV light, which improves the acid generation efficiency and contrast
Implementation Method 2
image blurs due to acid diffusion become a problem
Data Source
AI summary
A resist composition comprising a sulfonium salt composed of a sulfonate anion having a carbon atom to which an iodine atom is bonded and a sulfonium cation having the formula (1) exhibits a high sensitivity and reduced LWR or improved CDU.