Electron Beam Inspection Scan Pattern Optimization for Wafer Hotspots
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Solution Overview
Problem
Current wafer inspection systems face a trade-off between sensitivity and throughput, with high sensitivity leading to low throughput due to increased overhead times in detecting small defects like litho hotspots, which are challenging to inspect efficiently as they are small and often require extensive stage movement and alignment.
Innovation Solution
An electron beam inspection system with a controller that generates optimized scan patterns to minimize dwell time between areas of interest on the wafer, allowing for flexible stage movement and variable speed, enabling efficient imaging of only critical areas while skipping non-relevant regions, thus reducing overhead and improving sensitivity and classification of small systematic defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the electron beam scans the entire wafer surface with high sensitivity to detect small defects, then defect detection sensitivity is improved, but inspection throughput decreases due to increased overhead time from stage moving, settling, aligning, and focusing
Solution Approach 1:
The patent divides the wafer inspection into multiple swaths, with each swath containing multiple areas of interest (AOIs). Instead of scanning the entire wafer uniformly, the system segments the inspection into targeted AOIs within each swath, allowing high-sensitivity inspection of critical areas while skipping non-critical regions, thus improving throughput without sacrificing sensitivity for small defects like litho hotspots
Solution Approach 2:
The patent applies different inspection strategies to different regions of the wafer by identifying and prioritizing areas of interest (AOIs) within each swath. The electron beam focuses its high-sensitivity scanning only on these localized AOIs rather than uniformly scanning the entire wafer surface, enabling optimized sensitivity and throughput by matching inspection intensity to local defect risk
2Measurement precision
If the electron beam dwells longer on each area to improve image quality and defect detection, then measurement precision is improved, but inspection time increases reducing productivity
Solution Approach 1:
The patent applies partial action by scanning only the necessary areas (AOIs) within each swath at high resolution, rather than scanning the entire wafer at full resolution. The electron beam dwells on AOIs with appropriate dwell time for quality inspection, while rapidly transitioning between AOIs and skipping non-critical areas, thus achieving sufficient image quality for defect detection without excessive total inspection time
Solution Approach 2:
The system performs preliminary identification of areas of interest (AOIs) within each swath before the actual electron beam scanning begins. This preliminary action allows the system to pre-plan the scan pattern and dwell times for each AOI, optimizing the balance between image quality and inspection time by knowing in advance which areas require detailed examination
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 significantly reduces overhead times, enhances the effectiveness of electron beam scanning, and allows for better sensitivity and classification of small defects, optimizing inspection time and throughput by focusing on specific areas of interest, thereby improving overall wafer inspection efficiency.
Implementation Method 1
an electron beam generator unit configured to generate an electron beam
Data Source
AI summary
An inspection tool includes a controller that is configured to generate a scan pattern for an electron beam to image areas of interest on the wafer. The scan pattern minimizes dwell time of the electron beam on the surface of the wafer between the areas of interest. At least one stage speed and at least one raster pattern can be selected based on the areas of interest. The controller sends instructions to electron beam optics to direct the electron beam at the areas of interest on the surface of the wafer using the scan pattern.