Onium Salt Resist Composition for Acid Diffusion Suppression
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Solution Overview
Problem
Conventional resist compositions using onium salt type photoacid generators fail to sufficiently suppress acid diffusion, leading to degraded lithographic performance such as contrast, line width roughness (LWR), critical dimension uniformity (CDU), mask error factor (MEF), exposure latitude (EL), and depth of focus (DOF), and pattern collapse during small-size pattern formation.
Innovation Solution
An onium salt containing a fluoroalkanesulfonic acid anion with an aromatic ring protected by an acid labile group and a pentafluorosulfanyl group bonded to adjacent carbon atoms is used as a photoacid generator in a chemically amplified resist composition, enhancing solvent solubility and sensitivity, and improving lithography properties like LWR, CDU, MEF, EL, and DOF.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional onium salt type photoacid generators are used, then the resist composition can be manufactured with existing materials, but acid diffusion is not sufficiently suppressed leading to degraded lithographic performance
Solution Approach 1:
The patent modifies the molecular structure of the onium salt by introducing a pentafluorosulfanyl group and an acid labile group at specific positions in the aromatic ring. This structural parameter change increases the steric bulk and electron-withdrawing capability, which suppresses acid diffusion while maintaining photodecomposition performance, thereby improving lithographic precision without sacrificing manufacturability.
Solution Approach 2:
The patent creates a composite photoacid generator structure by combining the onium cation with a specially designed anion containing both the pentafluorosulfanyl group and the acid labile group. This composite structure achieves synergistic effects where the pentafluorosulfanyl group suppresses acid diffusion and the acid labile group enhances sensitivity, resolving the contradiction between manufacturing feasibility and performance.
2Manufacturing precision
If the resist composition is designed for high resolution, then pattern fidelity improves, but pattern collapse occurs during small-size pattern formation
Solution Approach 1:
The patent introduces an acid labile group that undergoes chemical transformation upon acid generation. This parameter change in the chemical structure of the anion enhances the solubility contrast between exposed and unexposed regions, improving pattern fidelity while the steric bulk from the pentafluorosulfanyl group prevents excessive swelling, thereby avoiding pattern collapse.
3Ease of manufacture
If existing photoacid generators are used, then the resist composition can be produced with available chemicals, but solvent solubility and sensitivity are insufficient
Solution Approach 1:
The patent modifies the anion structure by adding the pentafluorosulfanyl group, which contains sulfur and fluorine atoms. This parameter change in molecular weight and polarity improves solvent solubility while the acid labile group enhancement increases sensitivity. The structure remains based on conventional onium salt architecture, maintaining ease of manufacture through available synthetic routes.
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 contrast, high sensitivity, and reduced pattern collapse during small-size pattern formation, with improved lithography properties such as LWR, CDU, MEF, EL, and DOF.
Implementation Method 1
Photoacid generators that generate perfluorobutanesulfonic acid are currently used. However, when these salts are used for the resist composition, diffusion of the generated acid is large
Implementation Method 2
when these salts are used for the resist composition, diffusion of the generated acid is large, and it is difficult to achieve high resolution
Data Source
AI summary
The chemically amplified resist composition comprises an onium salt as a photoacid generator. The resist composition has a high solvent solubility and a high sensitivity and being improved in lithography properties such as LWR, CDU, MEF, EL, and DOF with high contrast when processed by photolithography using high-energy radiation such as KrF or ArF excimer laser, EB, or EUV; and a pattern forming process using the chemically amplified resist composition. The onium salt has the formula (1):