Multi-Beam Voltage Contrast Wafer Inspection for Time-Dependent Defects
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Solution Overview
Problem
Current single beam SEM inspection tools face limitations in detecting defects in ICs due to time-dependent electrical characteristics, as they can fail to capture defects that appear temporarily or change over time, and have fixed long time spans between image frames, leading to missed defects.
Innovation Solution
A multi-beam inspection system that uses a plurality of beams to generate multiple images of the same area of a wafer with controllable timing, allowing for the comparison of voltage contrast images to identify defects, and adjusts the stage speed to vary the time difference between scans, enabling more rapid and sensitive defect detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single beam SEM inspection tool is used, then the device complexity is reduced, but the defect detection capability deteriorates due to fixed long time spans between image frames
Solution Approach 1:
The inspection system divides the single inspection task into multiple parallel beam operations. Multiple electron beams simultaneously inspect different regions of the wafer, capturing multiple images in quick succession. This segmentation of the inspection process allows for reduced time spans between frames while maintaining system manageability.
Solution Approach 2:
The patent combines multiple electron beams into a single inspection system that operates in parallel. By merging multiple beam sources and their corresponding detection systems, the apparatus achieves high-speed multi-frame capture capability, reducing the time span between images while improving defect detection reliability.
2Productivity
If the stage speed is increased to reduce time difference between scans, then the productivity is improved, but the image quality may deteriorate due to motion blur or positioning errors
Solution Approach 1:
The system maintains continuous stage motion during the scanning process rather than stopping and starting. This continuous movement allows for optimized stage speeds that reduce inspection time while maintaining image quality through consistent positioning. The multi-beam system captures images during this continuous motion, eliminating gaps and reducing overall inspection time.
Solution Approach 2:
The patent implements dynamic stage speed control that adapts to different inspection regions and requirements. The stage speed can be varied during the inspection process to optimize both productivity and image quality, with faster speeds in less critical areas and slower speeds where higher precision is needed.
3Reliability
If multiple images are captured with small time difference, then the defect detection sensitivity is improved, but the loss of time is reduced
Solution Approach 1:
The multi-beam system implements periodic scanning patterns where multiple beams systematically scan different regions in a repeating sequence. This periodic action allows for capturing multiple images with optimized time differences, ensuring that defects appearing during the inspection window are detected while maintaining efficient use of inspection time.
Solution Approach 2:
The system performs preliminary positioning and pre-scanning operations to identify regions of interest before conducting the full multi-frame inspection. This preliminary action allows the system to focus resources on critical areas, reducing the overall inspection time while maintaining high defect detection sensitivity in the most important regions.
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 multi-beam system enhances defect detection sensitivity and throughput by capturing multiple images quickly and comparing them to identify time-dependent changes in electrical characteristics, improving the reliability of defect identification in ICs.
Implementation Method 1
The primary electrons interact with the wafer and may be backscattered or may cause the wafer to emit secondary electrons
Implementation Method 2
The primary electrons interact with the wafer and may be backscattered or may cause the wafer to emit secondary electrons
Implementation Method 3
System and method for defect inspection using voltage contrast in a charged particle system
Data Source
AI summary
A system and method for defect inspection using voltage contrast in a charged particle system are provided. Some embodiments of the system and method include positioning the stage at a first position to enable a first beam of the plurality of beams to scan a first surface area of the wafer at a first time to generate a first image associated with the first surface area; positioning the stage at a second position to enable a second beam of the plurality of beams to scan the first surface area at a second time to generate a second image associated with the first surface area; and comparing the first image with the second image to enable detecting whether a defect is identified in the first surface area of the wafer.