Semiconductor Wafer Inspection Standard Setting for Defect Detection
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Solution Overview
Problem
Current light-scattering type surface inspection apparatuses for semiconductor wafers lack sensitivity in detecting abnormal substances due to insufficient consideration of apparatus-induced and probabilistic overlooking rates, leading to potential noise misclassification as defects.
Innovation Solution
A method to set evaluation standards for semiconductor wafers using a light-scattering type surface inspection apparatus by determining the number of inspections and detection threshold based on specific overlooking rates, accounting for both apparatus-induced and probabilistic factors to enhance detection sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a light-scattering type surface inspection apparatus is used to detect abnormal substances on semiconductor wafer surfaces, then defect detection capability is provided, but the sensitivity is insufficient due to apparatus-induced and probabilistic overlooking rates
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing the relationship between inspection times and overlooking rates in a table before actual inspection. This allows the system to quickly determine the appropriate number of inspections needed to achieve a target overlooking rate without performing complex real-time calculations, thereby improving detection sensitivity while maintaining reliability.
Solution Approach 2:
The patent implements feedback by using the calculated overlooking rate to adjust and determine the number of inspection times. The system continuously refines the inspection strategy based on the relationship between inspection frequency and overlooking probability, ensuring that detection sensitivity is optimized while keeping the overlooking rate within acceptable limits.
2Reliability
If multiple inspections are performed to reduce overlooking rate, then detection reliability improves, but inspection time and productivity decrease
Solution Approach 1:
The patent resolves this contradiction by pre-calculating the optimal number of inspections for various target overlooking rates and storing these values in a reference table. During actual operation, the system simply retrieves the pre-determined inspection count based on the desired reliability level, avoiding the need to perform multiple inspections and thus maintaining high productivity while ensuring detection reliability.
Solution Approach 2:
The patent changes the parameter of inspection time by determining it based on the target overlooking rate rather than using a fixed number of inspections. This allows flexible adjustment of inspection duration to match the required reliability level, optimizing the balance between detection reliability and inspection efficiency.
3Measurement precision
If the detection threshold is lowered to increase sensitivity, then more abnormal substances are detected, but noise misclassification increases
Solution Approach 1:
The patent applies feedback by using the calculated overlooking rate as a control parameter to adjust the detection process. The system determines the appropriate detection threshold and inspection frequency based on the target overlooking rate, creating a feedback loop that balances sensitivity improvement with noise suppression, thereby reducing misclassification while maintaining high detection capability.
Solution Approach 2:
The patent changes the detection threshold parameter dynamically based on the target overlooking rate rather than using a fixed threshold. This allows the system to optimize the balance between detecting true abnormalities and avoiding noise misclassification by adjusting the threshold according to the desired reliability level.
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 allows for more sensitive detection of abnormal substances on semiconductor wafers, improving the quality and reliability of wafer evaluation by reducing overlooking rates and distinguishing between noise and actual defects.
Implementation Method 1
a light-scattering type surface inspection apparatus which detects the abnormal substances present on the surface of a semiconductor wafer as a light point defect
Data Source
AI summary
The method of setting the evaluation standard of a semiconductor wafer includes setting the A and B on the basis of an abnormal substances overlooking rate “a” specific to the light-scattering type surface inspection apparatus specified by an apparatus-induced abnormal substances overlooking rate Φ due to the light-scattering type surface inspection apparatus and a probabilistic abnormal substances overlooking rate, in which A is the number of times of inspection, B is an abnormal substances detection threshold, the apparatus-induced abnormal substances overlooking rate Φ is higher as the target abnormal substances size to be detected is smaller, and the probabilistic abnormal substances overlooking rate is lower as the number of times of inspection increases.