EUV Mirror Surface Defect Mitigation via Spin-Coating
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Solution Overview
Problem
Existing techniques for manufacturing EUV and X-ray optics are expensive and time-consuming, and they struggle to achieve the necessary high spatial frequency surface roughness (HSFR) and low defect tolerances required for optimal performance.
Innovation Solution
A method involving spin-coating a material onto the curved mirror surface to cover defects and improve surface smoothness, followed by curing to harden the thin film, thereby reducing HSFR and defect counts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional polishing techniques (IBF, MRF, CMP, CCOS) are used to achieve required surface smoothness, then surface quality can be improved, but the process becomes expensive and time-consuming
Solution Approach 1:
The patent applies preliminary action by performing spin-coating of a planarization layer before the final polishing stage. This preliminary coating fills in surface irregularities and defects, creating a more uniform base surface that reduces the amount of subsequent polishing required, thereby decreasing overall processing time while maintaining high surface quality
Solution Approach 2:
The patent introduces an intermediary material layer (planarization layer composed of spin-coat glass or similar materials) between the substrate and the final optical surface. This intermediary layer acts as a mediator that fills defects and roughness features, allowing the final polished surface to achieve required smoothness with less aggressive polishing that would otherwise be time-consuming
2Manufacturing precision
If conventional polishing techniques are used to achieve required surface smoothness, then surface quality can be improved, but manufacturing cost increases
Solution Approach 1:
The spin-coating step is performed as a preliminary, low-cost operation before expensive polishing processes. This preliminary action fills defects and creates a more uniform surface, reducing the amount of expensive polishing time required and thereby lowering overall manufacturing cost while achieving the same surface quality
Solution Approach 2:
The patent uses a disposable planarization layer made from inexpensive spin-coat glass or similar materials that can be easily applied and removed. This cheap intermediary layer fills expensive-to-correct defects, allowing the final optical surface to be polished more economically without compromising quality
3Ease of manufacture
If traditional fabrication methods are used, then manufacturing process is simple, but high spatial frequency surface roughness (HSFR) and defects cannot be sufficiently reduced
Solution Approach 1:
The patent applies preliminary spin-coating to fill in high spatial frequency roughness and defects before final polishing. This preliminary action addresses HSFR issues that would be difficult and time-consuming to correct through polishing alone, thereby improving manufacturing precision without significantly complicating the overall process
Solution Approach 2:
The patent changes the physical state and properties of the surface by applying a planarization layer through spin-coating, which fills defects and modifies surface topology. This parameter change in surface structure allows subsequent polishing to achieve much lower HSFR and defect levels than would be possible with traditional methods alone
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 method effectively reduces HSFR to less than 1 nm and decreases the number of defects to less than one per square millimeter, enhancing the performance of EUV and X-ray optics.
Implementation Method 1
The spin-coated material is then cured, for example, by UV irradiation, to harden the thin film and reduce the number of defects and HSFR on the curved mirror surface.
Data Source
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AI summary
A method of making a mirror for use with extreme ultraviolet (EUV) or X-ray radiation is disclosed. The method includes: a) providing an optical element having a curved mirror surface, wherein the curved mirror surface comprises localized defects that degrade performance of the curved mirror surface; b) spin-coating the curved mirror surface with a material to cover at least some of the defects; and c) curing the spin-coated material on the curved mirror surface to reduce the number of defects and improve the performance of the curved mirror surface. Also disclosed is a mirror made by the method.