Chemically Amplified Negative Resist with Onium-Salt Acid Generator
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Solution Overview
Problem
Existing chemically amplified resist compositions face challenges in achieving high resolution, reduced line edge roughness (LER), and forming patterns with high fidelity, particularly in the context of ArF excimer laser lithography, due to issues with acid diffusion and compatibility with substrates like chromium compounds.
Innovation Solution
Incorporating an onium salt with a sulfonic acid anion having a substituted fused ring structure and an aromatic sulfonic acid structure as an acid generator, along with specific base polymers, to control acid diffusion and enhance pattern formation, resulting in improved resolution and reduced LER.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional acid generators are used in chemically amplified resist compositions, then the resist can be processed, but acid diffusion occurs leading to reduced resolution and increased line edge roughness
Solution Approach 1:
The patent changes the chemical parameters of the acid generator by using specific onium salts with sulfonic acid anions having substituted fused ring structures. This modification alters the acid generation characteristics to reduce diffusion while maintaining catalytic activity for pattern formation.
Solution Approach 2:
The patent employs composite material design by combining specific base polymers with onium salt acid generators that have particular molecular structures. This composite approach creates a resist system where the acid generator is optimized to work synergistically with the polymer matrix to minimize acid diffusion and reduce line edge roughness.
2Reliability
If phenolic units are used in resist compositions for KrF excimer laser lithography, then high etching resistance is achieved, but strong absorption at 200 nm prevents use in ArF excimer laser lithography
Solution Approach 1:
The patent applies local quality by introducing fluorinated aromatic groups at specific positions within the onium salt structure. This localized modification allows the molecule to maintain etching resistance through aromatic structure while the fluorine substitution reduces absorption at the 157 nm ArF excimer laser wavelength.
Solution Approach 2:
The patent changes the optical parameters of the resist materials by incorporating fluorinated aromatic groups into the onium salt structure. This chemical modification shifts the absorption characteristics to be transparent at ArF excimer laser wavelengths while preserving the etching resistance properties.
3Ease of manufacture
If chromium compound layers are deposited on photomask substrates, then photomasks can be formed, but the surface material impacts the pattern profile of the overlying resist film
Solution Approach 1:
The patent introduces a specific onium salt composition as an intermediary between the chromium compound layer and the resist system. This acid generator acts as a mediator that facilitates proper pattern transfer while minimizing adverse interactions with the chromium surface, thereby maintaining rectangular pattern profiles.
4Manufacturing precision
If low-sensitivity resist is used in multibeam mask writing process, then roughness is improved, but optimization of resist composition for high-dose region is required
Solution Approach 1:
The patent achieves universality by developing a resist composition with onium salt acid generators that performs optimally across different exposure conditions including both low-dose multibeam mask writing and high-dose applications. The specific sulfonic acid anion structure provides consistent performance regardless of dose variations, reducing the need for separate composition optimizations.
Data Source
Figure 1
AI summary
A chemically amplified negative resist composition comprising (A) a photoacid generator in the form of an onium salt containing a sulfonic acid anion having a substituted fused ring structure and an aromatic sulfonic acid structure and (B) a base polymer is provided. The resist composition exhibits a high resolution during pattern formation and forms a pattern with satisfactory LER and fidelity.