Multi-spot Scanning Collection Optics for Semiconductor Wafer Inspection
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Solution Overview
Problem
Current inspection and metrology systems for semiconductor wafers face challenges in accurately detecting defects and measuring characteristics due to issues with spot crosstalk and system complexity, particularly when using acousto-optic deflector (AOD) systems that generate multiple scanning spots with varying magnifications.
Innovation Solution
The system employs a longitudinal imaging approach with multiple detection channels, including normal and oblique illumination sub-channels, and a combination of optics elements like serrated teeth apertures and diffraction gratings to isolate and separate scanning spots, minimizing crosstalk and maintaining fixed collection magnification for efficient defect detection and characterization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple scanning spots are generated using AOD systems, then inspection throughput is improved, but spot crosstalk increases
Solution Approach 1:
The patent segments the inspection system into multiple independent detection channels (first longitudinal side channel, second longitudinal side channel, and normal channel), each responsible for collecting light from specific scanning spots. This segmentation isolates the detection paths to prevent crosstalk while maintaining high throughput through parallel processing of multiple spots
Solution Approach 2:
The patent introduces longitudinal side channels that collect light from the side (longitudinal dimension) in addition to the normal channel that collects from the top (vertical dimension). This multi-dimensional collection approach allows simultaneous detection of multiple scanning spots without interference, resolving the crosstalk issue while maintaining high inspection throughput
2Measurement precision
If multiple detection channels are added to reduce crosstalk, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent designs the multiple detection channels (first longitudinal side channel, second longitudinal side channel, and normal channel) to share common optical components and processing pathways where possible. Each channel serves a specific function for different scanning spots, but they utilize shared resources to minimize overall system complexity while maintaining high measurement precision through specialized detection paths
3Device complexity
If fixed collection magnification is used, then system complexity is reduced, but adaptability to different spot magnifications is worsened
Solution Approach 1:
The patent transitions from a single magnification system to a multi-dimensional detection approach with longitudinal side channels and normal channel operating in parallel. This allows the system to maintain fixed collection magnification for each channel while adapting to different spot magnifications through the geometric arrangement and optical path design of multiple channels, resolving the contradiction between simplicity and adaptability
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 configuration enhances the accuracy and efficiency of defect detection and measurement by minimizing spot crosstalk and system complexity, allowing for high-throughput inspection with improved sensitivity and reduced noise, while maintaining cost-effectiveness.
Implementation Method 1
an illumination channel for generating and scanning a plurality of incident beams to form a plurality of spots that scan across a segmented line comprised of a plurality of scan portions of the specimen
Implementation Method 2
measuring the amount of light scattered by the illuminated spot on the wafer
Implementation Method 3
a combination of optics elements like serrated teeth apertures and diffraction gratings to isolate and separate scanning spots
Data Source
AI summary
Disclosed are apparatus and methods for inspecting or measuring a specimen. A system comprises an illumination channel for generating and deflecting a plurality of incident beams to form a plurality of spots that scan across a segmented line comprised of a plurality of scan portions of the specimen. The system also includes one or more detection channels for sensing light emanating from a specimen in response to the incident beams directed towards such specimen and collecting a detected image for each scan portion as each incident beam's spot is scanned over its scan portion. The one or more detection channels include at least one longitudinal side channel for longitudinally collecting a detected image for each scan portion as each incident beam's spot is scanned over its scan portion.