Wafer Position Detection via Partial Contour Scanning
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Solution Overview
Problem
Existing methods for detecting wafer position deviations require detecting the complete periphery of the wafer, making the process time-consuming and unsuitable for batch processing.
Innovation Solution
A method and apparatus that detect a part of the wafer's periphery by rotating the wafer at different speeds and using a detector to estimate the eccentric position and aiming feature position based on accumulated contour data and rotation angles, allowing for reduced detection time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the complete periphery of the wafer is detected to calculate the center deviation and notch orientation, then the measurement precision is improved, but the detection time increases significantly
Solution Approach 1:
The patent applies partial action by detecting only a portion of the wafer periphery (specifically 90 degrees or less) rather than the complete 360-degree circumference. The detector captures contour data from a limited angular range, and the controller calculates the center deviation and notch orientation based on this partial data, achieving acceptable measurement precision while significantly reducing detection time
Solution Approach 2:
The detection process is segmented into discrete angular positions. The rotation table rotates the wafer to specific angles (0 degrees, 90 degrees, 180 degrees, 270 degrees), and the detector captures contour data at each segment. This segmentation allows the system to process partial periphery data efficiently while maintaining sufficient accuracy for wafer alignment
2Productivity
If the wafer is rotated at higher speed to reduce detection time, then the productivity is improved, but the measurement precision may deteriorate
Solution Approach 1:
The system uses periodic rotation of the wafer at controlled speeds, with detection occurring at specific periodic intervals (at predetermined angles during rotation). The rotation table rotates the wafer through complete cycles, and the detector captures data at regular angular intervals, allowing high-speed operation while maintaining measurement accuracy through periodic sampling at critical positions
Solution Approach 2:
The system changes the rotation speed parameter dynamically. The rotation table can rotate at different speeds depending on the detection phase - faster speeds during initial scanning and slower speeds during precise measurement phases. This parameter adjustment allows the system to optimize between productivity and measurement precision based on the specific detection requirements
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 method significantly reduces detection time by only requiring partial periphery detection within an acceptable error range, enhancing the efficiency of wafer manufacturing processes.
Implementation Method 1
a detector (14) to detect the contour (21) of the wafer (20)
Data Source
AI summary
A method for detecting positions of wafers includes: rotating a rotation table with a wafer thereon in a first direction at a first speed; detecting a contour of the wafer rotating in the first direction at the first speed to provide contour data; rotating the rotation table in a second direction at a second speed when an aiming feature of the wafer passes the detector in the first direction at the first speed; detecting the contour of the wafer rotating in the second direction at the second speed to provide new contour data; and stopping the rotation of the rotation table and the detection of the wafer according to an accumulation of contour data and corresponding rotation angles, to estimate an eccentric position of the wafer and a position of the aiming feature when the aiming feature passes the detector in the second direction at the second speed.