DIC Prism Shear Calibration for Uniform Defect Inspection
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Solution Overview
Problem
Existing defect inspection and categorization methods for compound semiconductor wafers and glass substrates using differential interference contrast microscopes face challenges in maintaining consistent light signal intensity due to varying shear amounts, leading to inconsistent brightness and difficulty in setting uniform inspection thresholds across different apparatuses.
Innovation Solution
A method and apparatus that calculates the shear amount of a differential interference contrast prism by capturing multiple interference contrast images, obtaining phase distributions, measuring fringe intervals, and adjusting the prism's position to maintain consistent path differences between ordinary and extraordinary light, enabling uniform inspection conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the shear amount of the differential interference contrast prism is not calculated and adjusted, then the inspection process can be performed quickly, but the intensity of the received light signal cannot be maintained constant leading to inconsistent brightness
Solution Approach 1:
The patent applies preliminary action by calculating the shear amount of the differential interference contrast prism before performing defect inspection. The shear amount is calculated using a quadric surface and captured images, and the prism position is adjusted in advance based on this calculation. This preliminary adjustment ensures that the path difference between ordinary and extraordinary light is standardized, thereby maintaining constant light signal intensity consistency before the actual inspection begins.
2Measurement precision
If the path difference of the differential interference contrast prism is adjusted, then the light signal intensity can be maintained constant, but the inspection conditions become complex requiring precise control
Solution Approach 1:
The patent applies self-service by enabling the system to automatically calculate the shear amount and adjust the prism position without requiring manual intervention or complex external control systems. The calculation is performed using the captured images of the quadric surface and the phase shift method, and the adjustment is executed based on the calculated shear amount, making the system self-regulating and simplifying the overall control complexity.
3Adaptability or versatility
If different shear amounts are used in different apparatuses, then each apparatus can be optimized for its specific application, but machine differences arise making it difficult to conduct uniform inspection
Solution Approach 1:
The patent applies parameter changes by calculating the actual shear amount parameter of each differential interference contrast prism and adjusting the prism position accordingly. This allows each apparatus to be optimized for its specific application while ensuring that the shear amount parameter is standardized across all apparatuses. The calculated shear amount is used to adjust the prism position, thereby achieving both optimization and uniformity in inspection conditions.
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 precise calculation of shear amounts, ensuring consistent light signal intensity and reducing machine differences, thereby facilitating accurate defect inspection and categorization across various samples using the same apparatus.
Implementation Method 1
A differential interference contrast microscope separates illumination light into ordinary light and extraordinary light by a differential interference contrast prism
Implementation Method 2
capturing a plurality of interference contrast images of a quadric surface included in an object surface by the interference optical system
Data Source
AI summary
A calculation method according to the present disclosure is a calculation method of calculating a shear amount produced by a predetermined optical element which is arranged on an optical path of an image-capturing optical system. The calculation method includes a step of capturing a plurality of interference contrast images of a quadric surface included in an object surface by the image-capturing optical system while changing a phase difference between two rays of divided light, a step of obtaining a phase distribution from the plurality of interference contrast images by a phase shift method, a step of measuring a fringe interval of interference fringes due to the quadric surface based on the phase distribution, and a step of calculating the shear amount of the optical element based on a constant in a formula expressing the quadric surface and the fringe interval.