Reticle Inspection Aperture Segmentation for False Positive Reduction
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Solution Overview
Problem
Lithographic patterning devices often suffer from contamination and false positive detections during inspection, leading to inaccuracies in the patterning process and increased costs due to inefficient processing and waste.
Innovation Solution
An inspection system that uses a radiation source to irradiate multiple regions of a lithographic patterning device, with a detector and processing circuitry to discard irrelevant image data and construct a composite image, minimizing false positives by separating the illumination and observation systems to avoid interference from diffractive patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional illumination is used to inspect the entire reticle surface, then coverage is improved, but false positive detections increase due to interference from diffractive patterns
Solution Approach 1:
The illumination aperture is segmented into multiple zones (central region and annular region) that illuminate different areas of the reticle. The central region illuminates the area of interest while the annular region illuminates surrounding areas, allowing selective detection that avoids diffractive pattern interference while maintaining comprehensive coverage.
Solution Approach 2:
Different regions of the illumination aperture provide different illumination qualities to different areas of the reticle. The central region provides illumination optimized for detecting particles in the area of interest, while the annular region provides illumination for surrounding areas, with each region having tailored optical properties to minimize false positives while maintaining detection accuracy.
2Reliability
If the illumination aperture is reduced to avoid diffractive pattern interference, then false positives are reduced, but inspection coverage is limited
Solution Approach 1:
The illumination aperture is divided into a central region and an annular region, each serving distinct functional purposes. The central region is optimized for high-accuracy particle detection in the area of interest, while the annular region extends illumination coverage to surrounding areas, thereby maintaining both detection accuracy and comprehensive inspection coverage simultaneously.
Solution Approach 2:
The illumination strategy transitions from a single-aperture approach to a multi-zoned aperture approach, adding the dimension of spatial segmentation within the aperture plane. This allows the system to provide different illumination characteristics (central vs. annular regions) that simultaneously achieve high detection accuracy and extended coverage area.
3Ease of manufacture
If uniform illumination is applied across the reticle, then processing is simplified, but detection precision is reduced due to interference from multiple surfaces
Solution Approach 1:
The illumination system applies non-uniform illumination where the central region receives different illumination intensity and angular distribution compared to the annular region. This local differentiation in illumination quality enables precise particle detection in the area of interest while minimizing interference from diffractive patterns, without requiring complex processing.
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 effectively reduces false positive detections and provides accurate contamination detection, improving the reliability of the patterning process and reducing processing delays and costs.
Implementation Method 1
transmit a signal beam scattered from the reticle
Data Source
AI summary
An inspection system includes a projection system including a radiation source configured to transmit an illumination beam along an illumination path and an aperture stop configured to select a portion of the illumination beam. The inspection system also includes an aperture stop that selects a portion of the illumination beam and an optical system that transmits the selected portion of the illumination beam towards an object and transmit a signal beam scattered from the object. The inspection system also includes a detector that detects the signal beam.