Wafer V-Notch Center Alignment Using Laser Contour Detection
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Solution Overview
Problem
Current methods for positioning the center of a V-type notch on wafers result in significant positioning errors due to the small width and shallow depth of the notch, leading to inaccuracies in crystal orientation measurement, which affects product yield and electrical performance.
Innovation Solution
A system comprising a positioning back plate, vacuum suction cup, line laser contour detection sensor, data processing device, and servo motor is used to determine the center of a concentric circle corresponding to the V-type notch edges, judge its position relative to a reference scale line, and rotate the wafer to align the notch with the target center position, reducing errors and improving measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a V-type notch with small width and shallow depth is processed on the wafer edge, then the crystal orientation identification is facilitated, but the positioning accuracy of the notch center deteriorates
Solution Approach 1:
The patent introduces a reference scale line as an intermediary element on the positioning back plate. This reference line serves as a mediator between the V-type notch and the measurement system, providing a stable reference for accurate center positioning. The reference scale line allows the system to overcome the inherent positioning difficulties of small, shallow notches by providing an external reference framework.
Solution Approach 2:
The patent replaces manual mechanical positioning methods with an automated optical-mechanical system. A line laser contour detection sensor is used to automatically detect the V-type notch and calculate its center position, eliminating the need for manual visual alignment. This substitution of mechanical manual operation with automated sensing and calculation significantly improves positioning accuracy.
2Device complexity
If manual positioning methods are used for the V-type notch, then the device complexity is reduced, but the positioning accuracy and measurement reliability deteriorate
Solution Approach 1:
The patent replaces manual mechanical positioning with an automated system comprising a line laser contour detection sensor, data processing device, and servo motor. The sensor automatically detects the notch geometry, the data processing device calculates the center position and determines rotation parameters, and the servo motor executes precise rotation. This automated mechanical-optical system replaces simple manual operations while dramatically improving measurement accuracy.
Solution Approach 2:
The system implements a feedback loop where the line laser contour detection sensor continuously monitors the V-type notch position, the data processing device calculates the deviation from the target center, and the servo motor adjusts the wafer rotation accordingly. This closed-loop feedback mechanism ensures high positioning accuracy by constantly comparing actual position with target position and making real-time corrections.
3Loss of time
If the V-type notch is positioned away from the target center, then the wafer rotation adjustment is unnecessary, but the crystal orientation measurement accuracy deteriorates
Solution Approach 1:
The system performs preliminary detection of the V-type notch position using the line laser contour detection sensor before the actual crystal orientation measurement. The data processing device calculates the center position and determines the required rotation angle in advance. This preliminary positioning action ensures that the notch is correctly aligned before measurement begins, preventing measurement errors without requiring time-consuming trial-and-error adjustments.
Solution Approach 2:
The patent replaces time-consuming manual alignment adjustments with an automated rotation system. The data processing device calculates the precise rotation angle needed, and the servo motor executes the rotation automatically. This mechanical automation of the alignment process both improves accuracy and reduces the time required compared to manual positioning methods.
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 reduces positioning errors, enhances measurement accuracy, saves labor costs, and improves production efficiency by accurately aligning the V-type notch with the reference scale line, ensuring precise crystal orientation measurement.
Implementation Method 1
a vacuum suction cup, embedded in the circular hole; the vacuum suction cup is used to adsorb the wafer with the back of the wafer tightly attached to the positioning back plate
Implementation Method 2
a line laser contour detection sensor, used to collect edge data of the V-type notch
Data Source
AI summary
A method is for positioning a center of a V-type notch of a wafer. The method includes: determining, based on collected edge data of a V-type notch of a wafer, a center of a concentric circle corresponding to edges of the V-type notch; and judging, based on a position relation between the center and a set reference scale line, whether the V-type notch is at a preset target center position. The method also includes determining, based on the position relation between the center and the set reference scale line, a rotation direction and rotation angle of the wafer when the V-type notch is out of the preset target center position; and driving, according to the rotation direction and rotation angle of the wafer, the wafer to rotate until the V-type notch is rotated to the preset target center position.