Wafer Edge Detection Noise Reduction for Notch Mark Positioning
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Solution Overview
Problem
Existing substrate positioning technologies face challenges in accurately detecting notch marks on transparent wafers due to saturated data generated by noise light, leading to erroneous judgments and reduced positioning accuracy.
Innovation Solution
A substrate positioning device and method that employs a rotary stage, a light sensor, and a control unit for noise reduction processing, interpolating abnormal data, and notch mark judgment to differentiate between noise areas and actual notch marks, ensuring accurate positioning based on specific judgment conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a light-transmitting sensor is used to detect the notch mark on a transparent wafer, then the detection capability is improved, but saturated data is generated due to noise light transmission through the entire wafer area
Solution Approach 1:
The patent segments the wafer edge into multiple detection points and uses a light-transmitting sensor to detect light transmission at each point. By dividing the detection task into discrete segments (edge points with notch vs. regular edge points), the system can identify the notch mark through pattern recognition while using the light-transmitting sensor's high sensitivity to detect the subtle differences in light transmission caused by the notch geometry.
Solution Approach 2:
The patent applies local quality by focusing the light transmission detection specifically on the edge region of the wafer where the notch mark is located, rather than detecting through the entire wafer area. The light-transmitting sensor is positioned to detect only local edge characteristics, which allows high-resolution detection of the notch mark while avoiding the problem of saturated data from noise light passing through the bulk of the transparent wafer.
2Reliability
If a light-reflecting sensor is used to detect the notch mark on a transparent wafer, then saturated data generation is reduced, but detection accuracy deteriorates because light is transmitted through the entire wafer area
Solution Approach 1:
The patent inverts the conventional approach by using a light-transmitting sensor (typically used for opaque objects) instead of a light-reflecting sensor (typically used for transparent objects). This inversion allows the system to exploit the high light transmission properties of transparent wafers to detect the notch mark through subtle variations in light transmission at the edge, achieving both high detection accuracy and reduced data saturation by properly positioning the sensor to detect only edge-specific light transmission patterns.
3Manufacturing precision
If noise reduction processing is applied to eliminate sudden abnormal data, then positioning accuracy is improved, but processing complexity increases
Solution Approach 1:
The patent applies preliminary action by implementing noise reduction processing as a pre-processing step before notch mark detection and positioning. The system first identifies and eliminates sudden abnormal data (noise) from the raw detection signals, then proceeds with notch mark identification and positioning based on the cleaned data. This preliminary noise reduction improves positioning accuracy by preventing false detections, while the automated nature of the processing keeps complexity manageable.
Solution Approach 2:
The patent uses feedback mechanisms in the noise reduction processing by comparing detected edge shape data with expected patterns and identifying deviations that indicate noise. The system continuously monitors detection data, compares it against reference patterns, and applies corrective filtering when abnormal patterns are detected, creating a feedback loop that maintains high positioning accuracy while adapting to different wafer 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
The solution effectively reduces erroneous notch mark judgments by eliminating sudden abnormal data and interpolating edge shape data, thereby improving the accuracy of notch mark detection and positioning on both transparent and nontransparent wafers.
Implementation Method 1
Light that is radiated toward the wafer edge is transmitted through the edge, and the notch mark is thus detected as the quantity of transmitted light changes at the notch mark
Implementation Method 2
a light-reflecting sensor, instead of a light-transmitting sensor is used in conjunction with such a transparent wafer to detect the notch mark by radiating light from one side of the transparent wafer and receiving the light reflected from the wafer
Data Source
AI summary
Noise reduction processing for detecting the circumferential edge of a wafer W placed on a rotary stage with a light-transmitting sensor, obtaining detection values provided by the light-transmitting sensor as substrate edge shape data, detecting sudden abnormal data in the substrate edge shape data, eliminating the detected sudden abnormal data and interpolating the substrate edge shape data with estimated data generated based upon surrounding data in place of the abnormal data, notch mark judgment processing for detecting a notch mark candidate in the substrate edge shape data having undergone the noise reduction processing and making a decision as to whether or not the sets of data corresponding to the notch mark candidate area satisfies a predetermined judgment condition, and substrate positioning processing for positioning the substrate based upon a notch mark that satisfies the predetermined judgment conditions are executed.