Onium Salt Resist Composition for Small-Pattern Lithography
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Solution Overview
Problem
Conventional resist compositions using sulfonium 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 an alkanesulfonic acid anion or arene sulfonic acid anion with a structure where a hydroxy group and a pentafluorosulfanyl group are protected with an acid labile group, bonded to adjacent carbon atoms on the aromatic ring, is used as a quencher or photoacid generator in a chemically amplified resist composition, enhancing solvent solubility and lithography properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If sulfonium salt type photoacid generators are used in resist composition, then the resist can function as a conventional photoacid generator, but acid diffusion is not sufficiently suppressed leading to degraded lithographic performance
Solution Approach 1:
The patent changes the chemical structure parameters of the photoacid generator by introducing a pentafluorosulfanyl group at the ortho position of the phenolic hydroxyl group. This structural modification alters the acid diffusion characteristics while maintaining photoacid generator functionality, thereby resolving the contradiction between sufficient acid diffusion control and conventional PAG operation.
Solution Approach 2:
The patent creates a composite photoacid generator structure combining a phenolic hydroxyl group with a pentafluorosulfanyl group in specific positional relationships. This composite molecular structure integrates both the photoacid generation capability and the acid diffusion suppression function within a single molecule, achieving improved lithographic performance.
2Manufacturing precision
If conventional photoacid generators are used, then the resist composition can be processed, but pattern collapse occurs during small-size pattern formation
Solution Approach 1:
The patent modifies the molecular parameters of the photoacid generator by adding the pentafluorosulfanyl group, which changes the acid diffusion profile. This parameter change prevents the excessive acid diffusion that causes pattern collapse in small-size patterns, thereby eliminating this harmful effect while maintaining pattern formation capability.
3Use of energy by moving object
If highly sensitive resist composition is required for ArF lithography, then exposure dose can be reduced, but acid diffusion increases making it difficult to achieve high resolution
Solution Approach 1:
The patent changes the chemical composition parameters of the photoacid generator by incorporating the pentafluorosulfanyl group, which simultaneously achieves high sensitivity (low exposure dose requirement) and high resolution by controlling acid diffusion. This parameter modification resolves the trade-off between sensitivity and 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 onium salt-based resist composition achieves high sensitivity, high contrast, and improved lithography properties like LWR, CDU, MEF, EL, and DOF, while effectively suppressing pattern collapse during small-size pattern formation.
Implementation Method 1
a photoacid generator capable of generating a strong acid
Data Source
AI summary
The onium salt has the formula (1). The chemically amplified resist composition comprising the onium salt 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.