Wafer Centering via Defect Pattern Transfer on Chuck
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Solution Overview
Problem
The accuracy of wafer placement on a chuck during semiconductor manufacturing is compromised due to mis-calibration between robotic devices and the chuck, leading to potential defects in the fabrication process as the wafer may not be centered correctly, affecting the desired results of wafer fabrication processes.
Innovation Solution
A method and system that acquire defect metrology data from the wafer surface after contact with the chuck, determine the center coordinate of the chuck within the wafer's coordinate system, calculate the offset between the chuck and wafer centers, and adjust the wafer handling mechanism to align the wafer center with the chuck center, using support features on the chuck to transfer a defect pattern that is analyzed to determine the necessary adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a robotic device is used to place the wafer on the chuck, then the wafer can be handled and positioned automatically, but the placement accuracy deteriorates due to mis-calibration between the robotic device and the chuck spatial position
Solution Approach 1:
The system performs preliminary calibration by placing a test wafer on the chuck, capturing an image of the wafer position relative to the chuck, determining the offset between the robotic device's coordinate system and the chuck's coordinate system, and storing this calibration data for use in subsequent wafer placement operations. This preliminary action enables the robotic device to automatically compensate for mis-calibration and achieve accurate centering.
2Productivity
If the wafer is placed without centering verification, then the process is faster and simpler, but the fabrication process results deteriorate due to non-centered wafer positioning
Solution Approach 1:
The system replaces mechanical centering verification methods with an optical imaging system that captures an image of the wafer position on the chuck. The image is processed to determine the wafer center coordinates and compare them with the chuck center, automatically calculating the offset. This substitution maintains high productivity while ensuring reliable fabrication results through accurate digital measurement and correction.
3Manufacturing precision
If defect metrology data is acquired and analyzed to determine chuck center coordinates, then the wafer centering precision is improved, but the measurement and detection complexity increases
Solution Approach 1:
The system creates a digital copy of the wafer and chuck spatial relationship by capturing an image and processing it to extract coordinate information. Instead of performing complex physical measurements, the system uses image processing to generate a digital representation of the wafer position, from which the offset between wafer center and chuck center is calculated. This copying approach simplifies the measurement process while maintaining high precision.
Data Source
AI summary
A wafer handling mechanism is operated to place a wafer on a chuck. A chucking force is then applied to the wafer, whereby wafer support features of the chuck transfer a defect pattern onto a surface of the wafer. The surface of the wafer is analyzed by a defect metrology tool to obtain a mapping of the defect pattern transferred onto the surface of the wafer. A center coordinate of the chuck within a coordinate system of the wafer is determined by analyzing the defect pattern as transferred to the surface of the wafer. A spatial offset between the center coordinate of the chuck and the center of the wafer is determined. The spatial offset is used to adjust the wafer handling mechanism so as to enable alignment of the center of the wafer to the center coordinate of the chuck.