Overlapping Swath Imaging for Photon-Efficient Field Uniformity
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Solution Overview
Problem
Conventional inspection tools face challenges in achieving uniform illumination across the imaging field, particularly for extreme ultraviolet (EUV) tools, which operate with low photon counts and high photon shot noise, leading to nonuniform illumination spots and reduced photon utilization.
Innovation Solution
A swath imaging system that combines overlapping swath images using Time-Delay-Integration (TDI) sensors to compensate for nonuniformities caused by beam profiles, optics, and detector responsivity, achieving high image uniformity by summing or averaging overlapping portions of swath images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional illumination approaches are used, then field uniformity is improved, but photon efficiency deteriorates
Solution Approach 1:
The imaging field is divided into multiple overlapping swaths that are scanned across the sample. Each swath captures a portion of the sample with illumination, and the overlapping regions allow for computational combination to achieve uniformity while maintaining photon efficiency through the scanning process.
Solution Approach 2:
The system transitions from a single static illumination field to a dynamic scanning process that moves the illumination beam across the sample in a controlled manner. This temporal and spatial dimensionality change allows the same illumination to serve multiple regions, improving photon efficiency while maintaining uniformity through computational processing.
2Measurement precision
If higher light intensities are used to compensate for smaller pixels, then imaging resolution is improved, but field uniformity deteriorates
Solution Approach 1:
The system performs preliminary scanning of the sample with the illumination beam, capturing multiple overlapping swaths before final image processing. This preliminary action allows the system to later combine the swaths computationally to achieve uniform illumination distribution, enabling high resolution imaging without sacrificing field uniformity.
Solution Approach 2:
Multiple copies of the sample region are captured through overlapping swaths, and these copies are then computationally combined to create a unified image with uniform illumination. This copying and combination process allows high light intensities to be used for resolution while maintaining uniformity through the aggregation of multiple lower-intensity measurements.
3Stability of the object's composition
If conventional illumination systems are used, then field uniformity is achieved, but device complexity increases
Solution Approach 1:
The patent replaces complex optical systems with computational methods. Instead of using complicated optical components to achieve field uniformity physically, the system uses computational algorithms to combine overlapping swaths and correct nonuniformities in software, thereby reducing optical device complexity while maintaining field uniformity.
Solution Approach 2:
The system changes the approach from physical optical parameter adjustment to computational parameter processing. By capturing multiple swaths with known illumination characteristics and then adjusting the image data parameters computationally, the system achieves field uniformity without requiring complex optical components, reducing overall device complexity.
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 system enhances image uniformity, improves photon efficiency, and maintains throughput by reducing system complexity and manufacturing tolerances, suitable for EUV inspection tools with nonuniform illumination profiles.
Implementation Method 1
one or more Time-Delay-Integration (TDI) sensors configured to capture a plurality of swath images of the sample associated with the plurality of swaths
Implementation Method 2
an illumination source configured to illuminate a sample with an illumination beam
Data Source
AI summary
A swath imaging system may include an illumination source configured to illuminate a sample with an illumination beam, a stage to scan the sample with a scan pattern including swaths extending along a scan direction when implementing the inspection recipe, one or more TDI sensors configured to capture swath images of the sample, and a controller. The plurality of swaths may be distributed along a step direction orthogonal to the scan direction, and at least some of the plurality of swath images overlap along the step direction. The controller may implement the inspection recipe by receiving the plurality of swath images, combining the plurality of swath images into a uniformized image where overlapping portions of the plurality of swath images are combined within the uniformized image, and generating one or more measurements of the sample based on the uniformized image.