Defect Inspection Device with Focal Misalignment Correction
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Solution Overview
Problem
Existing defect inspection methods for semiconductor wafers struggle to detect minute defects without being affected by positional variations in the substrate height, leading to misalignment and reduced accuracy in defect detection.
Innovation Solution
A defect inspection device with a stage unit and light irradiation system that uses linearly shaped light inclined relative to the wafer surface, featuring multiple optical sensor arrays for detecting scattered light in different directions, and a processing unit that corrects for focal misalignment to combine signals effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple detectors are arranged in different directions to detect scattered light from defects, then defect detection capability and classification accuracy are improved, but misalignment occurs due to substrate height variations (pitching and yoking)
Solution Approach 1:
The patent applies preliminary action by calculating the expected positional misalignment between detectors based on substrate height variations before actual defect detection occurs. The control unit predicts misalignment amounts using predetermined values related to substrate height, allowing the system to compensate for these misalignments in advance during the detection process.
Solution Approach 2:
The patent implements feedback by using the detected misalignment information to adjust and correct the detection signals from multiple detectors. The control unit processes the misalignment data and applies correction to the detection signals, ensuring accurate defect detection despite substrate height variations. This closed-loop approach continuously monitors and corrects alignment issues.
2Productivity
If the wafer is continuously moved at high speed to increase inspection throughput, then productivity is improved, but positional variations in substrate height cause misalignment in detection
Solution Approach 1:
The patent applies preliminary action by pre-calculating misalignment compensation values based on the high-speed movement parameters and substrate height characteristics before defect detection. This allows the system to maintain detection accuracy even during rapid wafer translation without requiring slow-downs.
Solution Approach 2:
The patent implements feedback by continuously monitoring detection signals during high-speed wafer movement and dynamically adjusting for misalignment in real-time. The control unit processes misalignment information and corrects detection signals on-the-fly, enabling high throughput while maintaining precision through active compensation.
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 the detection of more minute defects by processing signals from multiple detectors without being affected by substrate height variations, improving defect detection accuracy and classification.
Implementation Method 1
a light irradiation unit which irradiates the test specimen placed on the stage unit with linearly shaped light from a direction inclined relative to a normal direction of a surface of the stage on which the test specimen is placed
Implementation Method 2
a first light collecting/detecting unit which collects and detects light reflected/scattered in a first direction from the test specimen irradiated with the linearly shaped light
Data Source
AI summary
To process a signal from a plurality of detectors without being affected by a variation in the height of a substrate, and to detect more minute defects on the substrate, a defect inspection device is provided with a photoelectric converter having a plurality of rows of optical sensor arrays in each of first and second light-collecting/detecting unit and a processing unit for processing a detection signal from the first and the second light-collecting/detecting unit to determine the extent to which the positions of the focal points of the first and the second light-collecting/detecting unit are misaligned with respect to the surface of a test specimen, and processing the detection signal to correct a misalignment between the first and the second light-collecting/detecting unit, and the corrected detection signal outputted from the first and the second light-collecting/detecting unit are combined together to detect the defects on the test specimen.