Collector Mirror Gas Flow Control for EUV Debris Mitigation
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Solution Overview
Problem
Current methods for mitigating debris damage in extreme ultraviolet radiation systems, such as laser-produced plasma sources, are inadequate as they either fail to prevent contamination from reaching sensitive optical components or drive it towards them.
Innovation Solution
A collector mirror assembly with a tubular body extending through a hole in the reflective surface, guiding gas flows transversely and divergently to suppress contamination, with tapered surfaces and additional walls to control sub-flows, directing gas away from the reflective surface to focal points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a buffer gas is used in the vicinity of the plasma to mitigate debris, then debris damage to the collector mirror is reduced, but the buffer gas may drive contamination towards the collector mirror and other optics
Solution Approach 1:
The gas flow control system is segmented into multiple independent flow paths: a first gas flow through the central hole and a second gas flow through the annular opening. This segmentation allows each flow to be optimized for different functions - the central flow provides buffer gas protection while the annular flow sweeps debris away from the optics, preventing the contamination drive problem
Solution Approach 2:
Different regions of the gas flow system are given different local qualities - the central hole region provides buffer gas with specific flow characteristics for debris mitigation, while the annular opening region provides a sweeping flow for contamination removal. Each region's gas flow is optimized for its specific function rather than using a uniform approach
2Manufacturing precision
If the collector mirror is used to focus EUV radiation, then imaging capability is achieved, but the reflective surface is vulnerable to debris contamination
Solution Approach 1:
A dual gas flow intermediary system is introduced between the plasma source and the collector mirror. The first gas flow through the central hole acts as a buffer gas to mitigate debris generation, while the second gas flow through the annular opening acts as a cleaning intermediary that sweeps debris away before it can contaminate the reflective surface, protecting the imaging capability
Solution Approach 2:
The gas flow system performs preliminary action by establishing protective gas flows before debris can reach the collector mirror. The buffer gas flow is established in advance to mitigate debris formation, and the sweeping gas flow is ready to immediately remove any debris that forms, preventing contamination before it occurs
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
Effectively reduces contamination on the collector mirror and other optics by diverging and controlling gas flows, preventing debris from reaching sensitive areas and maintaining the imaging ability of the reflective surface.
Implementation Method 1
A radiation system for producing EUV radiation may include a laser for exciting a fuel to provide the plasma... The plasma may be created, for example, by directing a laser beam at a fuel, such as particles of a suitable material (e.g. tin), or a stream of a suitable gas or vapor
Implementation Method 2
The resulting plasma emits output radiation, e.g., EUV radiation
Implementation Method 3
The radiation collector may be a mirrored normal incidence radiation collector, which receives the radiation and focuses the radiation into a beam
Implementation Method 4
The tubular body is constructed and arranged to guide a main gas flow in a direction substantially transverse to the reflective surface... An opening is arranged to guide a further gas flow that diverges with respect to the main gas flow
Data Source
AI summary
A collector mirror assembly includes a collector mirror that includes a reflective surface and a hole having an edge. The hole extends through the reflective surface. The assembly also includes a tubular body having an inner surface and an outer surface. The tubular body is constructed and arranged to guide a gas flow in a direction substantially transverse to the reflective surface. The outer surface of the tubular body and the edge of the hole form an opening arranged to guide a further gas flow that diverges with respect the gas flow substantially transverse to the reflective surface.