Defect Inspection Illuminance Adjustment via Histogram Correlation
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Solution Overview
Problem
In photolithography processes for semiconductor device manufacturing, defect inspection is time-consuming due to the need to repeatedly adjust and compare images of substrates at different illuminances to set optimal illuminance levels, making it difficult to accurately judge defects when luminance is too high or low.
Innovation Solution
A method involving illuminance adjustment steps where different illuminances are applied to multiple measurement regions on a substrate while moving, with image processing to find a reference luminance through histograms, allowing for automatic setting of optimal illuminance based on correlation analysis, reducing the need for multiple substrate movements and direct image comparisons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the luminance of the image of the wafer is too high or too low, then defects on the wafer cannot be judged, but appropriately adjusting the illuminance requires repeatedly moving the wafer and picking up images at different illuminances which takes a long time
Solution Approach 1:
The patent applies preliminary action by pre-establishing the correlation between illuminance and reference luminance through histogram analysis before actual defect inspection. The system performs illuminance adjustment using the established correlation to directly determine optimal illuminance without repeated trial-and-error movements, thus resolving the contradiction between measurement precision and time loss.
2Reliability
If the optimum illuminance is set by repeatedly applying illumination and picking up images at different illuminances, then the balance of luminance can be checked, but the wafer must be moved many times which increases inspection time
Solution Approach 1:
The patent replaces the mechanical trial-and-error system with an automated computational system. Instead of mechanically moving the wafer multiple times to check luminance balance, the system uses histogram analysis and correlation calculations to automatically determine the optimal illuminance, thereby maintaining reliability while improving productivity.
3Manufacturing precision
If multiple images are picked up and compared to set optimal illuminance, then appropriate luminance balance can be achieved, but the process becomes time-consuming
Solution Approach 1:
The patent applies parameter changes by transforming the illuminance setting process from a multi-step mechanical adjustment into a computational parameter optimization problem. The system changes the approach from physically moving the wafer and comparing images to analyzing luminance parameters through histograms and calculating correlations, thereby achieving precise illuminance setting with minimal time loss.
Data Source
AI summary
The present invention includes an illuminance adjustment step of setting an optimum illuminance of the illumination; and a defect inspection step of picking up the image of the substrate illuminated with the illumination at the optimum illuminance, wherein the illuminance adjustment step has: a first step of applying illuminations at different illuminances to a plurality of measurement regions on a front surface of the substrate and picking up an image of each of the measurement regions, while moving the substrate; a second step of making a luminance of the picked up image of each of the measurement regions into a histogram to find a reference luminance where an integral value from a maximum luminance side of the histogram is a predetermined value; and a third step of calculating a correlation between each of the reference luminances and the illuminance, and setting based on the correlation an illuminance at which the reference luminance coincides with a predetermined luminance, as the optimum illuminance.