Polyurethane Elastomer Contamination Measurement for EUV Lithography
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Solution Overview
Problem
Existing particulate contamination measurement methods for EUV lithographic apparatuses leave residues, such as organic materials and metal layers, which are not acceptable for the high cleanliness requirements in EUV lithography, and can influence the contamination buildup on optics and wetting characteristics in coating processes.
Innovation Solution
A particulate contamination measurement apparatus using a polyurethane elastomer with a hardness between 20 and 80 Shore A, and a roughness of less than 1 micron Ra, which is carried by a flexible carrier and is self-adhesive, allowing for effective contact and removal of contamination particles without leaving residues, and is manufactured under controlled conditions to minimize contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional particulate contamination measurement methods are used, then particulate contamination can be detected, but residues such as organic materials and metal layers are left on the surface
Solution Approach 1:
The patent changes the physical and chemical parameters of the measurement surface material by using polyurethane elastomer with specific hardness (20-80 Shore A) and ultra-low roughness (<1 micron Ra). These parameter changes enable the material to be soft enough to conform to surface irregularities and capture particles effectively, while being chemically inert enough to avoid leaving residues on the measured surface.
Solution Approach 2:
The patent employs a composite structure consisting of a polyurethane elastomer layer carried on a flexible carrier. This composite material combines the particle-capturing properties of the elastomer with the mechanical support of the carrier, achieving both effective contamination detection and residue-free measurement.
2Measurement precision
If a softer material is used to increase contact area with contamination particles, then particle collection efficiency improves, but residue transfer risk increases
Solution Approach 1:
The patent optimizes the hardness parameter of the polyurethane elastomer to be between 20-80 Shore A, which is soft enough to conform to surface irregularities and maximize contact area with particles for effective collection, while remaining firm enough to prevent excessive material transfer to the measured surface.
Solution Approach 2:
The patent creates a localized ultra-clean measurement surface on the polyurethane elastomer with specific surface properties (hardness and roughness) that are optimized for particle capture without residue transfer, while the rest of the material structure provides mechanical support and flexibility.
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 apparatus effectively collects and detects particulate contamination without transferring residues, ensuring ultra-clean surfaces and minimizing contamination buildup, thus meeting the stringent cleanliness requirements of EUV lithography.
Implementation Method 1
a measurement surface of the flexible material will establish a greater contact area with a contamination particle than a contact area between the contamination particle and the metal surface
Implementation Method 2
The polyurethane elastomer may have a hardness that is below about 80 Shore A... allowing for effective contact and removal of contamination particles
Data Source
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AI summary
A particulate contamination measurement method and apparatus are discussed. The method, for example, comprises pressing a measurement surface (5) of a polyurethane elastomer (2) against a surface (7) to be measured, removing the polyurethane elastomer from the surface without leaving residues, then using an optical apparatus (11) to detect particles (8) which have been removed by the polyurethane elastomer from the surface and which have become attached to the polyurethane elastomer.