Wafer Edge Detection via Scanning Spot
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Solution Overview
Problem
Current wafer inspection systems face challenges in accurately determining defect coordinates on wafers due to limited resolution and precision, especially when detecting edges and notches, which can lead to difficulties in defect classification and review.
Innovation Solution
A system and method that utilize a light source and optical elements to direct light beyond the wafer edge, allowing for high-confidence edge detection by scanning the edge with a spot that extends beyond the wafer, using a detector to generate output responsive to the light, and a computer processor to determine precise wafer inspection coordinates based on the edge locations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single photosensitive element is used for edge detection in spiral scanning, then inspection time is minimized, but measurement precision deteriorates due to limited resolution
Solution Approach 1:
The patent divides the single detector's output into multiple virtual channels by detecting gradual signal changes across different spiral tracks. Instead of using one detector for the entire edge, the system segments the detection task by analyzing track-to-track signal variations, effectively creating multiple measurement points from a single physical detector.
Solution Approach 2:
The patent transitions from spatial segmentation (multiple detectors at different positions) to temporal/sequential segmentation (single detector measuring across multiple tracks). By utilizing the spiral scanning's natural progression through multiple revolutions, the system adds a temporal dimension to edge detection, allowing high-resolution measurements without requiring multiple simultaneous detectors.
2Measurement precision
If multiple scans are used for edge detection, then measurement precision improves, but productivity deteriorates due to increased inspection time
Solution Approach 1:
The patent maintains continuous inspection by performing edge detection throughout multiple spiral revolutions without stopping the wafer rotation. The single detector continuously samples the edge position across each track, and the system accumulates these measurements in real-time, ensuring uninterrupted inspection while achieving high precision through multiple samples.
Solution Approach 2:
The system performs preliminary edge detection during the normal spiral scanning process itself, rather than requiring separate dedicated edge scanning steps. By detecting edge position information during each routine inspection pass, the system gathers sufficient precision data without adding extra inspection time or separate scanning operations.
3Measurement precision
If the spot size is reduced for higher resolution, then measurement precision improves, but productivity worsens due to increased scanning time
Solution Approach 1:
The patent introduces signal processing and coordinate transformation algorithms as intermediaries between the single detector and the final edge position measurement. These computational intermediaries extract precise edge location information from the gradual signal changes, achieving high measurement precision without requiring physically smaller spot sizes that would slow down scanning.
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 enables accurate and efficient determination of wafer inspection coordinates with sub-micron precision, improving edge and notch detection capabilities and reducing the complexity of defect review processes.
Implementation Method 1
Optical collection subsystems of such systems may collect light scattered by the wafer surface and detect the presence of defects of interest (DOI) on the wafer based on changes in the scattering signal.
Implementation Method 2
a light source and at least one optical element forming an illumination subsystem configured to direct light to a spot on an edge of a wafer
Data Source
AI summary
Methods and systems for determining wafer inspection coordinates for fixed location(s) on a wafer are provided. One system includes an illumination subsystem configured to direct light to a spot on an edge of a wafer. The spot extends beyond the edge of the wafer. The system also includes a stage that rotates the wafer thereby causing the spot to be scanned over the edge of the wafer. The system also includes a detector configured to detect light from the spot while the spot is being scanned over the edge and to generate output responsive thereto. The system further includes a computer processor configured to determine wafer inspection coordinates of two or more locations on the edge of the wafer based on the output and to determine wafer inspection coordinates of fixed location(s) on the wafer based on the wafer inspection coordinates of the two or more locations on the edge.