Collector-Free EUV Source Module Using Grazing-Incidence Mirror
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Solution Overview
Problem
Current EUV lithography systems face inefficiencies in transferring radiation from the primary source location to the secondary source location due to high thermal loading, complex and expensive collector optics, and low collection efficiency, leading to significant radiation losses and increased manufacturing costs.
Innovation Solution
The system generates a spatially limited hot plasma as a volume emitter directly illuminating the output opening without collector optics, with a plasma transverse dimension greater than the output opening, and uses a debris filter to manage debris, allowing for a collector-free design that improves collection efficiency and reduces expenditure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If nested multi-shell reflectors (Wolter design) are used for focusing radiation, then radiation can be focused to a secondary source location, but the collector absorbs 50% or more of the radiation as heat, causing thermal loading and distortion
Solution Approach 1:
The patent extracts the focusing function from the nested multi-shell reflector system and replaces it with a single grazing-incidence mirror. This eliminates the multiple reflection surfaces that cause cumulative absorption losses while maintaining the ability to focus radiation to a secondary source location.
Solution Approach 2:
Instead of using multiple nested reflectors that trap and absorb radiation, the invention inverts the approach by using a single open mirror system that reflects radiation with minimal absorption, allowing the radiation to escape after one reflection rather than undergoing multiple reflections.
2Temperature
If a cooled collector is used to handle thermal loading, then thermal distortion can be reduced, but cooling pipes must be arranged in radiation shadows, causing additional radiation losses
Solution Approach 1:
The patent removes the collector component entirely from the system, eliminating the need for cooling pipes and associated radiation shadows. The single grazing-incidence mirror design does not require active cooling infrastructure, thereby preventing the radiation losses that would result from shadowing.
3Power
If large collector optics are used to increase radiation output, then more radiation can be collected, but the vacuum chamber dimensions increase to approximately 1 m diameter and 1.5-2 m length, causing long pumping times
Solution Approach 1:
Instead of increasing collector size to improve radiation output, the invention inverts the approach by using a smaller single mirror system that achieves comparable or superior output through optimized grazing-incidence reflection geometry, thereby reducing vacuum chamber size and pumping time.
4Power
If nested multi-shell reflectors are used for focusing, then radiation can be concentrated, but the manufacture is very complicated and extremely expensive
Solution Approach 1:
The patent extracts the radiation concentration function from the complex nested multi-shell reflector system and implements it using a single grazing-incidence mirror. This simplifies manufacturing dramatically while maintaining the ability to concentrate radiation effectively.
Solution Approach 2:
The invention segments the optical system into a single independent mirror component rather than requiring multiple nested shells, making the system easier to manufacture, assemble, and maintain while achieving the same radiation concentration effect.
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 enhances the collection efficiency of EUV radiation, reduces manufacturing costs, and simplifies the system by eliminating the need for expensive collector optics, achieving comparable efficiency with reduced resources and complexity.
Implementation Method 1
a plasma generation arrangement (2) for ionization of gas for the plasma (3) which, e.g., emits a radiation in the EUV spectral region
Implementation Method 2
the plasma (3) which, e.g., emits a radiation in the EUV spectral region
Implementation Method 3
at least one debris filter (4) which is arranged between the plasma (3) and the output opening (6)
Data Source
AI summary
The invention is directed to an arrangement for generating EUV radiation particularly for source modules in exposure installations for EUV lithography for semiconductor chip fabrication. The object of the invention, to find a novel possibility for realizing an EUV source module which appreciably improves the ratio of resources to results in the transfer of radiation from the primary source location (plasma 3) to the secondary source location (output opening (6) of the source module (1)/intermediate focus plane (62)), is met according to the invention in that the plasma (3) is formed as a volume emitter for direct illumination of the output opening (6) without collector optics (5), and the transverse dimension (d) of the plasma (3) is greater than the diameter (D) of the output opening (6), wherein the extent to which the diameter is exceeded depends on the distance (L) between the plasma (3) and the output opening (6) and on the numerical aperture (NA) of the illumination system downstream.