EUV Projection Lens Dynamic Wavefront Correction
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Solution Overview
Problem
Anamorphic projection lenses in EUV lithography face challenges in maintaining high resolution and throughput due to increased object-side numerical aperture, leading to astigmatic wavefront aberrations and reduced imaging quality, particularly when correcting for reticle displacement and oblique incidence of radiation.
Innovation Solution
A dynamic wavefront manipulation system is integrated into the projection lens, allowing for real-time adjustment of mirror positions and shapes to correct astigmatic wavefront aberrations caused by reticle displacement, using manipulators that can move mirrors in their rigid body degrees of freedom or deform their surfaces, enabling precise control of the wavefront during scanning operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the object-side numerical aperture is increased to achieve higher resolution, then the resolution capability improves, but astigmatic wavefront aberrations increase and imaging quality deteriorates
Solution Approach 1:
The patent employs a dynamic wavefront manipulation system with adjustable mirrors that can change their position and orientation in real-time during scanning operations. This dynamic adjustment allows the system to compensate for astigmatic wavefront aberrations that arise when the object-side numerical aperture is increased, thereby maintaining imaging quality while achieving higher resolution capability
Solution Approach 2:
The patent changes the parameters of the wavefront manipulation system (mirror positions, orientations, and shapes) to correct astigmatic aberrations. By dynamically adjusting these parameters, the system can maintain optimal imaging quality across different numerical aperture settings and during scanning operations, resolving the contradiction between resolution improvement and imaging quality degradation
2Manufacturing precision
If the imaging scale is reduced to halve the object-side numerical aperture and angles of incidence, then astigmatic aberrations are reduced, but the exposed field size and throughput are reduced
Solution Approach 1:
The dynamic wavefront manipulation system allows the patent to maintain a larger imaging scale (higher throughput) while dynamically correcting astigmatic aberrations during scanning. The system can adjust mirror parameters in real-time to compensate for the increased aberrations that result from operating at larger imaging scales, thus preserving both productivity and imaging quality
Solution Approach 2:
By dynamically changing the parameters of the wavefront manipulation system during scanning operations, the patent can operate at larger imaging scales that provide higher throughput while still maintaining control over astigmatic aberrations through real-time parameter adjustment, resolving the trade-off between productivity and aberration control
3Manufacturing precision
If mirrors are moved rapidly during scanning operations to correct wavefront aberrations, then imaging quality is maintained, but the system complexity and control difficulty increase
Solution Approach 1:
The wavefront manipulation system is segmented into multiple independent mirrors, each capable of being controlled separately. This segmentation allows the complex task of wavefront correction to be divided into simpler individual mirror adjustments, making the system more manageable despite its overall complexity
Solution Approach 2:
The system employs feedback control where the actual wavefront aberrations are measured and used to adjust the mirror parameters in real-time. This feedback mechanism simplifies the control of the complex system by using actual performance data to guide adjustments, ensuring imaging quality is maintained while managing system complexity through intelligent control
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 solution effectively compensates for astigmatic wavefront aberrations, maintaining high imaging quality and throughput by dynamically adjusting the optical effects of the projection lens, even during rapid scanning operations, thereby enhancing the ability to produce finer structures without significant reductions in field size or throughput.
Implementation Method 1
a multiplicity of mirrors having mirror surfaces arranged in a projection beam path between the object plane and the image plane in such a way that a pattern of a mask that is arranged in the object plane is imagable into the image plane by means of the mirrors
Data Source
AI summary
A projection lens is disclosed for imaging a pattern arranged in an object plane of the projection lens into an image plane of the projection lens via electromagnetic radiation having an operating wavelength λ from the extreme ultraviolet range. The projection lens includes a multiplicity of mirrors having mirror surfaces arranged in a projection beam path between the object plane and the image plane so that a pattern of a mask in the object plane is imagable into the image plane via the mirrors. A first imaging scale in a first direction running parallel to a scan direction is smaller in terms of absolute value than a second imaging scale in a second direction perpendicular to the first direction. The projection lens also includes a dynamic wavefront manipulation system for correcting astigmatic wavefront aberration portions caused by reticle displacement.