Immersion Lithography Topcoat Composition for Water Mark Defect Reduction
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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, and there is a need for topcoat compositions with higher receding contact angles to enable faster scan speeds and improved throughput.
Innovation Solution
The development of topcoat compositions comprising a polymer system with a matrix polymer and a surface active polymer, along with a solvent system including gamma-butyrolactone and/or gamma-valerolactone, which are self-segregating to minimize photoresist material migration into the immersion fluid, providing improved water receding contact angles and developer solubility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a topcoat layer is used to prevent photoresist leaching into immersion fluid, then photoresist material migration is reduced, but water receding contact angle decreases causing water mark defects
Solution Approach 1:
The topcoat composition uses a block copolymer with distinct segments: a first block providing water receding properties at the immersion fluid interface, and a second block providing resistance to photoresist material migration at the photoresist interface. This local differentiation of material properties within the same topcoat layer resolves the contradiction by allowing each interface to have optimized characteristics for its specific function.
Solution Approach 2:
The invention employs a composite block copolymer structure combining hydrophobic blocks (for water receding) and photoresist-resistant blocks (for preventing material migration). This composite material approach allows simultaneous achievement of high water receding contact angle and effective photoresist material migration prevention, which cannot be achieved with single-function materials.
2Reliability
If topcoat layer thickness is increased to improve barrier properties, then photoresist leaching is reduced, but micro-bridging defects increase reducing device yield
Solution Approach 1:
The invention changes the chemical composition parameters of the topcoat material rather than relying solely on thickness increases. By selecting specific block copolymers with appropriate hydrophobicity and photoresist resistance properties, effective barrier performance is achieved at optimal thicknesses that prevent micro-bridging defects while maintaining leaching prevention.
3Productivity
If scan speed is increased to improve throughput, then productivity increases, but water droplets are left behind causing resist sensitivity alteration
Solution Approach 1:
The topcoat layer is applied in advance to establish a hydrophobic surface that actively repels water droplets before the scanning process begins. This preliminary protective action ensures that even at high scan speeds where water droplets might otherwise be left behind, the resist sensitivity remains unchanged because the water receding property prevents droplet formation and adhesion.
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 significantly reduce photoresist material migration into the immersion fluid, enhance water contact angle characteristics, and allow for faster scanning speeds and improved process throughput by maintaining high receding contact angles and developer solubility, thus addressing the challenges of micro-bridging defects and yield reduction.
Implementation Method 1
self-segregating topcoat compositions to form a graded topcoat layer
Implementation Method 2
the surface active polymer has a lower surface energy than a surface energy of the matrix polymer
Implementation Method 3
direct contact between the immersion fluid and photoresist layer can result in leaching of components of the photoresist into the immersion fluid
Implementation Method 4
a solvent system comprising a first organic solvent chosen from gamma-butyrolactone and/or gamma-valerolactone, and a second organic solvent
Data Source
AI summary
Topcoat compositions are provided that can be used in immersion lithography to form photoresist patterns. The topcoat compositions include a polymer system that includes a matrix polymer and a surface active polymer. The matrix polymer is present in the composition in a larger proportion by weight than the surface active polymer, and the surface active polymer has a lower surface energy than a surface energy of the matrix polymer. A solvent system includes a first organic solvent chosen from gamma-butyrolactone and/or gamma-valerolactone, and a second organic solvent. The first organic solvent has a higher surface energy than a surface energy of the surface active polymer, and a higher boiling point than a boiling point of the second organic solvent.