Defect Inspection Device Illumination Intensity Control
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Solution Overview
Problem
Current defect inspection techniques for semiconductor substrates face challenges in detecting minute defects of 20 nm or less due to faint scattered light signals being buried in noise, thermal damage issues, and reduced inspection speed, especially at the center of the sample, where thermal damage is overestimated, and defect detection sensitivity varies with illumination spot position.
Innovation Solution
A defect inspection device with an irradiating unit that adjusts illumination light to maintain 50% intensity at the center and less than 0.1% elsewhere, a scanning unit for perpendicular scanning, and a detecting unit to process scattered light signals for defect presence and dimension determination, ensuring high accuracy and reduced thermal damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If illumination power is increased to detect minute defects, then defect detection sensitivity is improved, but thermal damage to the sample increases
Solution Approach 1:
The illumination intensity distribution is made non-uniform with a peak at the center position. This local quality approach concentrates illumination power where it is most needed for detecting minute defects, while reducing intensity at peripheral positions to minimize thermal damage. The illumination intensity at the center is maintained at 50% or more relative to the maximum, enabling detection of defects with dimensions of 20 nm or less without excessive thermal damage to the sample.
Solution Approach 2:
The illumination intensity distribution is dynamically adjusted during scanning based on the radial position of the illumination spot. By controlling the illumination intensity according to position, the system optimizes the balance between detection sensitivity and thermal damage prevention in real-time during the inspection process.
2Productivity
If scan speed is increased to improve inspection efficiency, then productivity is improved, but defect detection sensitivity deteriorates due to reduced irradiation time
Solution Approach 1:
The illumination intensity is locally enhanced at the center position where minute defects are most likely to be missed due to brief passage. By concentrating illumination power at the center, the system compensates for the reduced irradiation time at high scan speeds, maintaining detection sensitivity without sacrificing productivity.
3Stability of the object's composition
If uniform illumination is used across the sample surface, then inspection consistency is improved, but thermal damage at the center is overestimated
Solution Approach 1:
Instead of uniform illumination, the system applies local quality by creating a non-uniform illumination intensity distribution with a peak at the center. This approach actually improves inspection consistency for minute defects at the center while reducing thermal damage, as the enhanced center illumination compensates for the brief passage time during 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
Enables fast and accurate detection of minute defects across the entire sample surface with reduced thermal damage and stable inspection results, improving defect detection sensitivity and dimension calculation precision.
Implementation Method 1
illumination light is focused into dimensions of several tens of μm on the sample surface to detect a minute defect, light scattered by the defect is collected and detected
Data Source
AI summary
Proposed is a defect inspection method whereby: illuminating light having a substantially uniform illumination intensity distribution in one direction of a sample surface irradiated on the sample surface; multiple scattered light components, which are output in multiple independent directions, are detected among the scattered light from the sample surface and multiple corresponding scattered light detection signals are obtained; at least one of the multiple scattered light detection signals is processed and the presence of defects is determined; at least one of the multiple scattered light detection signals that correspond to each of the points determined by the processing as a defect is processed and the dimensions of the defect are determined; and the position and dimensions of the defect on the sample surface, at each of the points determined as a defect, are displayed.