Onium Salt Resist Composition Suppressing Acid Diffusion
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Solution Overview
Problem
Current resist compositions using conventional sulfonium salt-type photoacid generators (PAGs) fail to fully suppress acid diffusion, leading to degraded lithography properties such as contrast, mask error factor (MEF), and line width roughness (LWR), as well as pattern collapse during small-size pattern formation.
Innovation Solution
An onium salt with an aromatic ring-bearing sulfonic acid anion, featuring an acid labile group-protected hydroxy group and a fluorinated substituent group attached to adjoining carbon atoms, is used in a chemically amplified resist composition. This onium salt acts as either a quencher or a photoacid generator, enhancing solvent solubility, sensitivity, and lithography properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional sulfonium salt-type PAGs are used, then the resist composition can be manufactured with existing technology, but acid diffusion is not fully suppressed leading to degraded lithography properties
Solution Approach 1:
The patent changes the chemical parameters of the PAG by using onium salts with specific structures (aromatic ring-bearing sulfonic acid anions with acid labile group-protected hydroxy groups and fluorinated substituent groups on adjoining carbon atoms). This structural parameter change suppresses acid diffusion while maintaining manufacturability and improving lithography properties including contrast, MEF, and LWR.
Solution Approach 2:
The patent employs composite molecular结构设计 in the onium salt, combining multiple functional groups (aromatic ring, sulfonic acid anion, acid labile group-protected hydroxy group, and fluorinated substituent group) within a single molecule. This composite structure achieves both acid diffusion suppression and high solvent solubility.
2Illumination intensity
If the resist material uses highly transparent polymers at 193 nm wavelength, then the transparency of the resin is increased, but the sensitivity and lithography properties are not sufficiently improved
Solution Approach 1:
The patent changes the chemical composition parameters by introducing onium salts with specific functional groups that enhance both transparency and sensitivity. The aromatic ring-bearing sulfonic acid anion with fluorinated substituent groups provides high 193 nm transparency while the acid labile group-protected hydroxy group enhances sensitivity and lithography properties.
3Manufacturing precision
If existing PAGs capable of generating perfluorobutanesulfonic acid are used, then the resist composition can be produced, but high resolution is difficult to achieve due to substantial acid diffusion
Solution Approach 1:
The patent modifies the PAG structure by using onium salts with aromatic ring-bearing sulfonic acid anions where the acid labile group-protected hydroxy group and fluorinated substituent group are attached to adjoining carbon atoms. This specific structural parameter change reduces acid diffusion compared to existing perfluorobutanesulfonic acid generating PAGs, enabling high resolution patterning.
4Object-generated harmful factors
If partially fluorinated alkane sulfonic acids and salts are used as PAGs, then acid diffusion is reduced, but environmental safety and ease of decomposition are unsatisfactory due to lack of decomposable substituent groups
Solution Approach 1:
The patent designs composite molecular structures where the onium salt contains an acid labile group-protected hydroxy group that can be decomposed. The aromatic ring-bearing sulfonic acid anion with fluorinated substituent groups on adjoining carbon atoms provides both acid diffusion suppression and environmental safety through decomposability of the acid labile group.
Solution Approach 2:
The patent introduces decomposable functional groups (acid labile group-protected hydroxy group) into the PAG structure, changing the chemical composition parameters to enable both acid diffusion suppression and environmental safety through controlled decomposition.
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 exhibits high sensitivity, high contrast, improved lithography properties including MEF and LWR, and minimizes the risk of pattern collapse during small-size pattern formation.
Implementation Method 1
a high sensitivity resist material capable of achieving a high resolution at a small dose of exposure is needed... photolithography using an ArF excimer laser (wavelength 193 nm)
Implementation Method 2
The ArF immersion lithography requires a resist material which is substantially insoluble in water... positive ArF resist compositions of the prior art design may be used
Implementation Method 3
current resist compositions using conventional sulfonium salt-type photoacid generators (PAGs) fail to fully suppress acid diffusion, leading to degraded lithography properties such as contrast, mask error factor (MEF), and line width roughness (LWR)
Data Source
AI summary
An onium salt consisting of an aromatic ring-bearing sulfonic acid anion and a cation, the anion having an acid labile group-protected hydroxy group and a fluorinated substituent group on the aromatic ring, is provided. A resist film of a chemically amplified resist composition comprising the onium salt has advantages including reduced LWR, high resolution, and collapse resistance when processed by the DUV, EUV or EB lithography.