Sulfonium Salt Polymer Resist for High-Sensitivity EUV Patterning
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Solution Overview
Problem
Existing chemically amplified resist compositions face challenges in achieving high sensitivity, resolution, and lithography properties such as exposure tolerance, line width roughness (LWR), critical dimension uniformity (CDU), and depth of focus (DOF), particularly in photolithography processes using high-energy radiation like KrF excimer laser, ArF excimer laser, electron beam (EB), or EUV, due to issues with acid diffusion and solvent solubility of iodine-containing photoacid generators.
Innovation Solution
A sulfonium salt monomer with a nitro group and fluorosulfonate anion having an aromatic vinyl structure and an iodine atom is used to create a polymer that functions as a photoacid generator, enhancing the chemically amplified resist composition's sensitivity, lithography properties, and solvent solubility, thereby improving LWR, CDU, and DOF.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the amount of acid generator is increased to enhance sensitivity, then sensitivity is improved, but the acid diffusion distance is also increased leading to degraded LWR and CDU
Solution Approach 1:
The patent combines the acid generator function with the polymer backbone by incorporating sulfonium salt groups directly into the polymer structure. This merging allows the polymer to serve dual purposes: as the structural matrix and as the acid source, eliminating the need for separate acid generator additives that would diffuse and cause LWR/CDU degradation.
Solution Approach 2:
The patent introduces a polymer-bound sulfonium salt as an intermediary that generates acid in situ within the polymer matrix. This intermediary approach confines acid generation to the immediate polymer structure, preventing the acid from diffusing freely through the resist film while still providing sufficient acid for the chemical amplification reaction.
2Reliability
If iodine-containing photoacid generators are used to improve lithography properties, then lithography performance is enhanced, but solvent solubility decreases causing precipitation
Solution Approach 1:
The patent applies local quality by introducing iodine atoms at specific positions within the polymer chain rather than using bulk iodine-containing compounds. The iodine is incorporated into the polymer backbone at controlled densities, providing localized EUV absorption enhancement while maintaining overall polymer solubility in the resist formulation.
Solution Approach 2:
The patent creates a composite polymer structure combining organic polymer chains with iodine atoms and sulfonium salt groups. This composite material approach integrates multiple functional components (polymer matrix, iodine for EUV absorption, sulfonium for acid generation) into a single soluble molecular structure that provides both lithography performance and solubility.
3Volume of moving object
If the resist film thickness is reduced to comply with size reduction, then miniaturization is achieved, but LWR becomes greater
Solution Approach 1:
The patent extracts the acid diffusion problem from the system by eliminating the need for external acid generators that diffuse through the film. By incorporating acid generation capability directly into the polymer structure, the harmful acid diffusion process is removed, allowing thin film formation without LWR degradation.
Solution Approach 2:
The patent changes the fundamental parameter of acid generation location from a separate additive phase to an integrated polymer phase. This parameter change transforms the acid generation process from a diffusion-based mechanism to a localized in-situ generation mechanism, enabling thin film patterning with controlled LWR.
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 monomer-based polymer composition achieves high sensitivity and improved lithography properties, including high contrast, LWR, CDU, and DOF, while maintaining high solvent solubility, suitable for fine pattern formation in photolithography processes.
Implementation Method 1
a sulfonium salt monomer having a nitro group and a fluorosulfonate anion having an aromatic vinyl structure and an iodine atom
Implementation Method 2
It is known that iodine atoms are highly absorptive to EUV of wavelength 13.5 nm, and thus generate secondary electrons upon light exposure
Data Source
AI summary
A sulfonium salt monomer having the formula (A). The sulfonium salt monomer can be used for a chemically amplified resist composition having a high solvent solubility, a high sensitivity, and a high contrast, and being improved in lithography properties such as EL, LWR, CDU, and DOF, particularly when processed by photolithography using high-energy radiation such as KrF excimer laser, ArF excimer laser, an electron beam (EB), or EUV.