Segmented EUV Collector Mirrors for Precision and Debris Mitigation
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Solution Overview
Problem
EUV light sources face challenges in minimizing debris generation during plasma creation, which can damage optical elements and reduce operational efficiency, and existing collector mirrors struggle with maintaining high surface finish and figure accuracy as they increase in size.
Innovation Solution
The development of EUV optics, including collector mirrors, fabricated using multiple discrete substrates secured together by bonding or brazing, with a smoothing layer and multilayer coatings, and a support structure with actuators for precise alignment and adjustment, to minimize debris impact and maintain optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the collector mirror size is increased to collect more EUV light, then the light collection efficiency is improved, but the surface finish and figure accuracy deteriorate due to manufacturing difficulties
Solution Approach 1:
The patent divides the large collector mirror into multiple smaller mirror segments that can be manufactured with high precision individually. Each segment maintains excellent surface finish and figure accuracy while being assembled to form a large effective aperture for collecting EUV light, thus resolving the contradiction between size and manufacturing precision.
Solution Approach 2:
The patent employs composite mirror structures combining multiple materials with different properties (e.g., low thermal expansion substrates with highly reflective coatings) to maintain surface stability and optical precision in the large-scale collector mirror, overcoming the manufacturing precision limitations that would affect monolithic large mirrors.
2Power
If the plasma power is increased to generate more EUV light, then the EUV output is improved, but the debris generation increases which damages optical elements
Solution Approach 1:
The patent extracts and removes debris particles from the plasma chamber environment before they can reach and damage the optical elements. This is achieved through debris mitigation systems such as magnetic fields or physical barriers that separate harmful debris from the optical path, allowing high plasma power operation without proportional increase in optical damage.
Solution Approach 2:
The patent introduces intermediary protective measures between the plasma source and optical elements, such as protective coatings on mirrors or intermediary chambers that filter debris. These intermediaries allow high power plasma operation while protecting the optical train from debris contamination.
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
This approach reduces debris-related damage and enhances the ability to accurately direct EUV light, improving the operational efficiency and longevity of EUV light source optics while maintaining high reflectivity and surface quality.
Implementation Method 1
the required plasma can be produced by irradiating a target material, such as a droplet, stream or cluster of material having the required line-emitting element, with a laser beam
Implementation Method 2
Once generated, the EUV light is typically reflected by a multi-layer mirror, sometimes called a collector mirror
Implementation Method 3
coating each the substrate with a respective EUV reflective multilayer coating
Data Source
AI summary
In a first aspect, a method of fabricating an EUV light source mirror is disclosed which may comprise the acts/steps of providing a plurality of discrete substrates; coating each substrate with a respective multilayer coating; securing the coated substrates in an arrangement wherein each coated substrate is oriented to a common focal point; and thereafter polishing at least one of the multilayer coatings. In another aspect, an optic for use with EUV light is disclosed which may comprise a substrate; a smoothing layer selected from the group of materials consisting of Si, C, Si3N4, B4C, SiC and Cr, the smoothing layer material being deposited using highly energetic deposition conditions and a multilayer dielectric coating. In another aspect, a corrosion resistant, multilayer coating for an EUV mirror may comprise alternating layers of Si and a compound material having nitrogen and a 5th period transition metal.