Polymer-Bound Onium Salt Resist for Low-Diffusion Acid Control
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Solution Overview
Problem
Existing chemically amplified negative resist compositions face challenges in achieving high etching resistance, organic solvent solubility, and controlling acid diffusion, leading to issues such as pattern collapse and poor lithographic performance during the miniaturization of resist patterns.
Innovation Solution
Incorporating a polymer-bonded acid generator with repeat units derived from an onium salt containing an anion with a structure of an aromatic ring substituted with a vinyl group and a partially fluorinated sulfonate bond or amide bond, which enhances acid generation with low diffusion, improving solvent solubility and lithographic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a polymer-bonded acid generator with onium salt repeat units is used to control acid diffusion, then manufacturing precision and line edge roughness are improved, but device complexity increases due to the complex molecular structure requiring synthesis of onium salt monomers with specific anion structures
Solution Approach 1:
The patent applies parameter changes by modifying the chemical structure parameters of the acid generator. Specifically, it uses onium salt monomers with formula (A1) where the anion contains a partially fluorinated sulfonate group with variable parameters (n1, n2, R1-R6, a1-a4, b1-b6, etc.). By adjusting these structural parameters, the patent optimizes acid diffusion control while maintaining manufacturability. The fluorinated sulfonate anion structure provides appropriate acid strength and controlled diffusion characteristics.
Solution Approach 2:
The patent employs composite materials by creating a polymer with repeat units that combine multiple functional components: the onium salt structure for acid generation, the vinyl-substituted aromatic ring for polymer backbone formation, and the partially fluorinated sulfonate group for acid strength control. This composite structure within the repeat unit integrates multiple functions (acid generation, diffusion control, polymerizability) into a single molecular entity.
2Productivity
If the amount of acid generator is increased to improve sensitivity, then productivity is improved, but acid diffusion distance increases causing line edge roughness and dimensional uniformity to degrade
Solution Approach 1:
The patent uses parameter changes by modifying the acid generator structure to have appropriate acid strength through the partially fluorinated sulfonate anion. This structural parameter change allows the acid to have sufficient strength for high sensitivity while maintaining limited diffusion distance. The fluorination level and sulfonate structure parameters are optimized to balance sensitivity and precision.
Solution Approach 2:
The patent converts the potential harm of acid diffusion into a benefit by using the polymer-bonded structure where the acid is generated in situ. The acid diffusion is naturally limited by the polymer matrix, and the patent optimizes this by choosing the appropriate onium salt structure. The diffusion that would normally cause LER is converted into a controlled process that maintains sensitivity while limiting harmful diffusion effects.
3Strength
If polymers with aromatic structures and acidic side chains are used to achieve high etching resistance, then strength is improved, but absorption at wavelengths around 200 nm increases making them unsuitable for ArF excimer laser lithography
Solution Approach 1:
The patent applies parameter changes by modifying the optical parameters of the polymer through the specific onium salt structure. The vinyl-substituted aromatic ring system and partially fluorinated sulfonate anion are designed to reduce absorption at ArF excimer laser wavelengths (193 nm) while maintaining etching resistance. The fluorination and specific aromatic structure parameters are optimized for this balance.
Solution Approach 2:
The patent uses composite materials by creating a polymer structure that combines aromatic rings (for etching resistance) with vinyl groups and fluorinated sulfonate groups (for reduced UV absorption). This composite molecular structure integrates the beneficial properties of different chemical groups while minimizing their drawbacks.
4Ease of operation
If phenolic units are used as alkali-soluble units to achieve good solubility in aqueous alkaline developer, then ease of operation is improved, but transmissivity to exposure light at wavelengths of 150 to 220 nm is lost
Solution Approach 1:
The patent uses parameter changes by modifying the solubility parameters through the onium salt structure rather than using phenolic units. The polymer is designed to be soluble in organic solvents (PGMEA, etc.) used in the resist composition, eliminating the need for phenolic units. This parameter change in the solubility mechanism removes the harmful absorption issue while maintaining processability.
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 solution effectively controls acid diffusion, resulting in high-resolution patterns with reduced line edge roughness and improved pattern fidelity, while maintaining excellent etching resistance and solvent solubility.
Implementation Method 1
an acid generator which is decomposed to generate an acid upon exposure to light
Implementation Method 2
controlling the diffusion of the acid generated upon light exposure
Data Source
AI summary
Provided are an onium salt monomer which has excellent etching resistance, organic solvent solubility, and appropriate acid strength, and can generate an acid with low diffusion, a base polymer comprising a polymer-bonded acid generator using the same, a chemically amplified negative resist composition using the same, and a resist pattern forming process using the chemically amplified negative resist composition. An onium salt monomer has the formula (A1):