Sulfonium Salt Resist Composition for Acid Diffusion Control
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Solution Overview
Problem
Current chemically amplified resist compositions face challenges in controlling acid diffusion, leading to issues such as line edge roughness (LER) and dimensional uniformity (CDU) of patterns, especially in the miniaturization of resist patterns for semiconductor fabrication, where high-energy radiation is used for pattern formation.
Innovation Solution
A chemically amplified positive resist composition utilizing a betaine sulfonium salt with specific alkyl or fluorinated alkyl groups and a sulfoneamidate anion is developed, which enhances solvent solubility and improves lithographic performance by reducing acid diffusion and maintaining pattern profile stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional acid generators are used in chemically amplified resist compositions, then the resist film can be processed with high sensitivity, but acid diffusion occurs leading to poor resolution and increased line edge roughness
Solution Approach 1:
The patent introduces a sulfonium salt as an intermediary substance between the acid generator and the resist film. This sulfonium salt acts as a quencher that intercepts and neutralizes the acid generated during exposure, preventing it from diffusing into the resist film and causing unwanted reactions. The sulfonium salt is positioned in the acid generation region, serving as a mediator that controls acid mobility while maintaining the overall sensitivity of the resist system.
Solution Approach 2:
The patent modifies the chemical parameters of the resist composition by incorporating specific sulfonium salts with defined molecular structures (including aromatic rings, alkyl groups, and specific functional groups). These parameter changes in the chemical composition allow for precise control over acid diffusion behavior, transforming the uncontrolled acid diffusion problem into a manageable chemical reaction system that improves resolution while maintaining sensitivity.
2Manufacturing precision
If the resist film is scanned region by region with electron beam, then high resolution patterns can be formed, but the processing time increases significantly
Solution Approach 1:
The patent applies preliminary action by pre-positioning the sulfonium salt quencher in the resist film before exposure occurs. This pre-placed quencher is ready to immediately neutralize acid as soon as it is generated during exposure, eliminating the need for post-exposure correction steps and reducing the overall processing time while maintaining high resolution patterns.
Solution Approach 2:
The sulfonium salt quencher performs self-service by automatically neutralizing acid diffusion without requiring external intervention or additional processing steps. The quencher is inherently part of the resist composition and acts autonomously during exposure, reducing the need for complex external control systems and decreasing processing time while maintaining pattern quality.
3Stability of the object's composition
If acid diffusion is not controlled, then the resist composition can be simpler, but the pattern profile changes over time until post exposure baking
Solution Approach 1:
The patent merges the functions of the acid generator, the quencher, and the resist material into a single integrated composition system. The sulfonium salt is incorporated directly into the resist film matrix, combining multiple functions (acid generation, acid quenching, and pattern formation) into one unified system that maintains stability without requiring separate components or complex processing steps.
Solution Approach 2:
The sulfonium salt compound performs multiple functions simultaneously: it acts as a quencher to neutralize acid, serves as a structural component of the resist film, and influences the overall chemical environment during exposure. This multi-functionality reduces the need for separate additives and simplifies the overall composition while maintaining pattern profile stability throughout the processing sequence.
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 composition achieves high-resolution resist patterns with reduced LER and improved CDU, suitable for advanced lithography processes like EB and EUV, ensuring good rectangular profile and solvent solubility.
Implementation Method 1
the acid diffusion has a significant impact on sensitivity and resolution
Implementation Method 2
a resist composition comprising a resin to which a sulfonic acid generated upon exposure is bonded to control acid diffusion
Implementation Method 3
In the lithography process of forming patterns with a feature size of 0.2 μm or less, chemically amplified resist compositions utilizing acid as a catalyst are mostly used. Here, as the energy source for exposure, high-energy radiation such as UV, deep UV or EB is used.
Implementation Method 4
The EB lithography utilized as the ultrafine processing technology is indispensable for the processing of photomask blanks
Implementation Method 5
Patent Documents 1 and 2 describe acid generators capable of generating bulky acids for controlling acid diffusion and reducing LER
Implementation Method 6
chemically amplified resist compositions utilizing acid as a catalyst are mostly used
Implementation Method 7
a base polymer having introduced therein repeat units capable of generating acid upon exposure sometimes encounters a problem with respect to its solubility in organic solvent
Data Source
AI summary
The sulfonium salt monomer has the formula (A) below. The chemically amplified positive resist composition includes the sulfonium salt monomer. The chemically amplified positive resist composition is processed by photolithography using, in particular, high-energy radiation such as KrF excimer laser, ArF excimer laser, EB or EUV, has good solvent solubility, and is excellent in lithographic performance such as resolution, LER and a pattern profile.