EUV Radiation Collector with Nested Mirrors for DPP Source Integration
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Solution Overview
Problem
Current EUV radiation collectors face challenges such as wide radiation emission angles, limited directional output, material debris protection, and high complexity and cost, making them unsuitable for efficient use with DPP sources in extreme UV lithography.
Innovation Solution
A radiation collector with a primary and secondary mirror, each with a specific generatrix shape optimized for EUV radiation, allowing for efficient concentration and uniform distribution of radiation, reducing complexity and cost by eliminating the need for multiple mirrors and enabling placement between the radiation source and utilization apparatus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a DPP source is used to produce EUV radiation, then energy yield is improved and bulk is reduced, but the radiation is emitted in a wide solid angle that cannot be used directly
Solution Approach 1:
The collector divides the wide solid angle of emitted radiation into multiple zones using a primary mirror with a specific generatrix, reflecting different angular segments to a common focal region, thereby converting omnidirectional emission into a directed beam suitable for lithography
Solution Approach 2:
The patent transforms the three-dimensional wide solid angle emission into a two-dimensional concentrated spot on the wafer plane by using nested mirrors that map angular coordinates to spatial coordinates, effectively compressing the radiation distribution in one dimension while maintaining control in others
2Object-affected harmful factors
If a protection system is placed between the DPP source and the radiation utilization device, then protection against material debris is improved, but the system complexity and bulk increase
Solution Approach 1:
The nested mirror collector serves as an intermediary optical system that physically separates the DPP source from the radiation utilization device, allowing a protection system to be positioned in the intermediate space without compromising optical performance or increasing overall system complexity
Solution Approach 2:
The collector employs nested mirrors where an inner mirror is positioned within the structure of an outer mirror, creating a compact configuration that reduces bulk while maintaining the necessary optical path length for effective debris protection
3Productivity
If multiple concentric shells are used in the collector, then radiation collection proportion is improved, but the unit cost price increases
Solution Approach 1:
The patent extracts only the essential reflective surfaces needed for effective radiation collection, using a primary mirror with a specifically designed generatrix and selective secondary mirrors, thereby reducing the number of components compared to complete concentric shell designs while maintaining collection efficiency
Solution Approach 2:
The primary mirror uses a non-standard generatrix equation that optimizes radiation collection for specific angular ranges, allowing effective performance with fewer mirrors by changing the geometric parameters of the reflective surfaces rather than relying on multiple identical components
4Adaptability or versatility
If the collector is placed between the protection system and the radiation utilization apparatus, then compatibility with existing modules is improved, but the spot dimensions and angular beamwidth must be precisely controlled
Solution Approach 1:
The nested mirrors employ curved surfaces with specifically designed generatrices that focus radiation from a point source onto a small spot, using spherical and elliptical geometries to achieve precise spot dimensions and uniform angular beamwidth suitable for lithographic applications
Solution Approach 2:
The collector design achieves a balance between spot concentration and beam angular width that makes it compatible with various existing lithography modules, creating a universal interface that can be integrated into different radiation utilization apparatus without requiring precise customization for each application
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 collector achieves a high collection efficiency with a focused, uniform radiation beam, suitable for EUV lithography, reducing bulk and cost while ensuring effective protection against debris, enhancing integration and manufacturing compatibility.
Implementation Method 1
The collector comprises a primary mirror and a secondary mirror, which are arranged to reflect the collected part of the radiation first by the primary mirror then by the secondary mirror
Implementation Method 2
The secondary mirror has a second generatrix in the meridian plane, which is adapted so that this secondary mirror produces the convergent output beam on a side of the collector opposite to the source of the radiation
Data Source
AI summary
The invention relates to a radiation collector (10) designed to concentrate part of the radiation produced by a source on a spot (100). The collector includes a primary concave mirror (1) and a secondary convex mirror (2), each being rotationally symmetrical about an optical axis (X-X) of the collector. The primary mirror is configured to reflect the radiation collected with an angle of incidence (i) that is substantially constant between different points on said main mirror. Such a collector is particularly suitable for use with a discharge produced plasma source.