Grazing-Incidence Field Mirrors for EUV Inspection Throughput
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Solution Overview
Problem
EUV inspection systems face challenges with high-throughput operation due to the short wavelength, energetic photons, and low radiance of EUV radiation sources, necessitating large object fields and detector arrays, which are not efficiently addressed by existing technologies.
Innovation Solution
The use of grazing incidence mirrors to split collected light into multiple fields, allowing for the placement of readout electronics outside the illuminated area, thereby increasing photon collection efficiency and reducing shot noise, while using time-delay-integration sensors to generate images from these fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If large object fields and detector arrays are used to increase signal integration rate, then throughput is improved, but device complexity and cost increase
Solution Approach 1:
The detector array is segmented into multiple independent linear detector arrays that can be independently controlled and read out. This segmentation allows parallel processing of different regions of the object field, increasing throughput without requiring a single complex large-scale detector array
Solution Approach 2:
The system employs periodic scanning motion where the object or detector moves in a periodic manner to scan different regions of the object field over time. This temporal multiplexing allows a smaller detector array to achieve the same effective coverage area, reducing device complexity while maintaining high throughput through rapid periodic scanning
2Measurement precision
If larger detector arrays are used to cover increased object fields, then signal integration rate improves, but readout time and noise increase
Solution Approach 1:
The detector array is divided into multiple linear detector arrays with independent readout circuits. Each linear array can be read out simultaneously or in a time-multiplexed fashion, reducing the total readout time compared to a single large array while maintaining the same total detection area and signal integration capability
Solution Approach 2:
The system uses multiple smaller linear detector arrays that cover the required object field area collectively. Each linear array processes a portion of the total signal, allowing parallel or sequential readout that is faster than reading out a single equivalent-sized array, thus reducing readout time while achieving the same total signal integration
3Device complexity
If readout electronics are placed within the illuminated area to simplify optics, then device complexity decreases, but photon collection efficiency decreases due to blocked light paths
Solution Approach 1:
The system uses a linear detector array arrangement where the readout electronics are positioned along one dimension (the length of the linear array) rather than across the entire two-dimensional illuminated area. This dimensional optimization allows readout electronics to be placed at the edges of the illumination path, minimizing blockage of photons while maintaining simplified optical coupling
Solution Approach 2:
The linear detector array acts as an intermediary between the illuminated object field and the readout electronics. By positioning the linear array at an optimal location where it can collect photons from the object field while keeping readout electronics outside the main illumination path, the system mediates between the conflicting requirements of optical simplicity and photon collection efficiency
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 photon collection efficiency, reduces shot noise, and improves tool throughput by optimizing the placement of readout electronics and increasing the number and size of sensors, facilitating faster defect detection in EUV inspection systems.
Implementation Method 1
one or more grazing incidence mirrors, wherein the one or more grazing incidence mirrors are configured to split a collected light into at least two fields, wherein the at least two fields include one or more reflected fields, wherein the one or more grazing incidence mirrors are disposed in a path of the one or more reflected fields such that the one or more reflected fields reflect from the one or more grazing incidence mirrors
Data Source
AI summary
Collected light may be split into fields using grazing incidence mirrors to avoid illuminating gaps between the active areas for readout electronics. The grazing incidence mirrors may reduce lost field space in the integrating direction by splitting the imaging field in that direction to allow the readout electronics to be outside of the field. The fields may be split so there is space for readout circuits but no associated light on the readout circuits. The size of the illumination may then be decreased and/or the number and/or size of sensors increased to improve the photon collection efficiency. The better photon collection efficiency may reduce shot noise and/or improves tool throughput.