Self-Segregating Topcoat Compositions for Immersion Lithography
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Solution Overview
Problem
In immersion lithography, topcoat layers used to prevent photoresist leaching into immersion fluids can cause contamination and affect process window and critical dimension variation, leading to micro-bridging defects and reduced device yield, necessitating improved self-segregating topcoat compositions.
Innovation Solution
Aqueous alkali-soluble topcoat compositions comprising a matrix polymer and additive polymers with specific monomer units, designed to inhibit photoresist migration and enhance water receding contact angles, providing improved developer solubility and reduced defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a topcoat layer is used to prevent photoresist leaching into immersion fluid, then contamination of the optical lens is reduced, but micro-bridging defects occur and device yield decreases
Solution Approach 1:
The topcoat composition uses multiple polymers with different properties (aqueous alkali-soluble matrix polymer, water-soluble polymer, and organic-soluble polymer) that self-segregate to provide different functions at different locations: the water-soluble polymer provides high water receding contact angle at the water interface to prevent water marks, while the organic-soluble polymer provides good developer solubility at the photoresist interface to prevent micro-bridging defects
Solution Approach 2:
The invention uses a composite topcoat material consisting of multiple polymer components with distinct solubility characteristics. The combination of aqueous alkali-soluble polymer, water-soluble polymer, and organic-soluble polymer creates a multi-functional topcoat that simultaneously addresses water repulsion and developer penetration requirements
2Object-affected harmful factors
If topcoat layer is applied over photoresist layer, then barrier function is provided, but process window and critical dimension variation are affected
Solution Approach 1:
The invention optimizes specific parameters of the topcoat composition including the molecular weight, concentration, and type of each polymer component. The aqueous alkali-soluble polymer has a specific molecular weight range (10,000-1,000,000) and the composition ratios are carefully controlled to achieve the desired balance between barrier function and CD control
3Object-affected harmful factors
If topcoat with low receding contact angle is used, then water mark defects are reduced, but scan speed must be reduced
Solution Approach 1:
The topcoat composition contains a water-soluble polymer that automatically migrates to the water interface during coating and drying, self-organizing to provide high water receding contact angle (75-85 degrees) without requiring external intervention. This self-segregation occurs based on the thermodynamic preference of the water-soluble polymer to be at the water interface
4Stability of the object's composition
If topcoat layer is used to prevent leaching, then immersion fluid properties are maintained, but micro-bridging defects increase
Solution Approach 1:
The topcoat composition uses an organic-soluble polymer specifically to provide good solubility in organic developers at the photoresist interface, preventing micro-bridging defects in developed patterns, while maintaining the overall integrity of the topcoat barrier function
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 topcoat compositions effectively minimize photoresist migration into immersion fluids, maintaining refractive index compatibility and enabling faster scanning speeds with reduced micro-bridging defects, thus enhancing process throughput and device yield.
Implementation Method 1
self-segregating topcoat compositions to form a graded topcoat layer
Implementation Method 2
a layer of the topcoat composition in a dried state has a water receding contact angle of from 75 to 85°
Data Source
AI summary
Topcoat layer compositions suitable for use in forming a topcoat layer over a layer of photoresist include: a matrix polymer which is aqueous alkali soluble; a first additive of mer which is aqueous alkali soluble and comprises polymerized units of a monomer of the following general formula (I):wherein: R1 is hydrogen or a C1 to C6 alkyl or fluoroalkyl group; R2 is a C3 to C8 branched alkylene group; and R3 is a C1 to C4 fluoroalkyl group; and wherein the first additive polymer is present in the composition in an amount less than the matrix polymer, and the first additive polymer has a lower surface energy than a surface energy of the matrix polymer; wherein a layer of the topcoat composition in a dried state has a water receding contact angle of from 75 to 85°. The compositions find particular applicability to immersion lithography processing.