Automated Optical Microscope for 3D Wafer Surface Measurement
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Solution Overview
Problem
Current 3-D measurement techniques for wafers during fabrication are inefficient and prone to human error, as they rely on manual focusing of microscopes, which can lead to defects being missed or misidentified, especially when dealing with semi-transparent layers and metal layers.
Innovation Solution
An automated system that varies the distance between the sample and the objective lens of an optical microscope at predetermined steps, captures images, determines characteristic values, and compares them to identify focused surfaces, allowing for accurate measurement of distances between surfaces, including semi-transparent and metal layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual focusing of microscope is used, then operation simplicity is maintained, but measurement precision and reliability deteriorate due to human error
Solution Approach 1:
The patent replaces the manual mechanical focusing operation with an automated optical measurement system. The system uses an optical microscope connected to a camera and computer, where the computer automatically controls the focusing mechanism and processes images to determine 3D information, eliminating human error in manual focusing while maintaining operational simplicity through automated control.
Solution Approach 2:
The measurement system performs self-service by automatically capturing images at different focal depths, processing the images through algorithms, and calculating 3D measurements without requiring continuous human intervention. The system autonomously adjusts focus, captures multiple images, and computes the results, making the measurement process self-sufficient and highly precise.
2Measurement precision
If automated image capture at multiple distances is performed, then measurement precision improves, but productivity decreases due to multiple capture steps
Solution Approach 1:
The system maintains continuity of useful action by automatically capturing a series of images at continuously varying focal depths without manual intervention between captures. The microscope continuously adjusts focus while the camera continuously captures images, creating an uninterrupted sequence of measurements that improves precision while the automation maintains productivity.
Solution Approach 2:
The system performs preliminary action by capturing multiple images at different focal distances in advance, storing them for subsequent processing. This preliminary capture of data at various depths allows the computer to later analyze and reconstruct 3D information without requiring repeated measurements, improving both precision and efficiency.
3Reliability
If human users focus microscope manually, then ease of operation is maintained, but reliability deteriorates due to human error in defect detection
Solution Approach 1:
The system implements feedback by capturing images at multiple focal depths and using computer algorithms to analyze the images and determine which contains the sharpest focus. The system provides feedback on the quality of focus for each captured image and automatically selects the optimal image for measurement, ensuring high reliability while the automated process maintains ease of operation through single-button initiation.
Solution Approach 2:
The patent replaces manual human operation with an automated optical measurement system that uses computer-controlled focusing and image processing. This substitution eliminates human error in defect detection while maintaining ease of operation through automated control, where the system performs all complex operations automatically after initial setup.
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 method enables fast and reliable 3-D information generation, reducing human error and improving defect detection accuracy during wafer fabrication by providing precise measurements of surface distances and layer thicknesses.
Implementation Method 1
determining a characteristic value of each pixel in each captured image; determining, for each captured image, the greatest characteristic value across all pixels in the captured image
Data Source
AI summary
A method of generating 3D information includes: varying the distance between the sample and an objective lens of the optical microscope at pre-determined steps, capturing an image at each pre-determined step; determining a characteristic value of each pixel in each captured image; determining, for each captured image, the greatest characteristic value across all pixels in the captured image; comparing the greatest characteristic value for each captured image to determine if a surface of the sample is present at each pre-determined step; determining a first captured image that is focused on a first surface of the sample based on the characteristic value of each pixel in each captured image; determining a second captured image that is focused on a second surface of the sample based on the characteristic value of each pixel in each captured image; and determining a first distance between the first surface and the second surface.