Wafer Centering Using Imaging-Based Robot Arm Compensation
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Solution Overview
Problem
Existing substrate processing systems face challenges in achieving precise substrate positioning due to thermal effects and other variabilities, which can lead to inaccurate placement, especially in semiconductor manufacturing where increased handling accuracy is crucial.
Innovation Solution
The implementation of an imaging system that captures images of the robot arm and compares them to calibration images to determine positional variances, allowing for motion compensation without relying on real-time encoder data, thereby ensuring accurate substrate placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If manual centering method is used, then device complexity is reduced, but manufacturing precision deteriorates due to time-consuming and tedious alignment process
Solution Approach 1:
The system uses the wafer's own markings (notches, tabs, or patterns) as reference features for automatic centering. The marking detection unit detects these self-provided features, and the control unit automatically calculates and adjusts the wafer position based on the detected marking positions, enabling the wafer to center itself without manual intervention.
Solution Approach 2:
The patent replaces manual mechanical alignment operations with an automated optical-electronic system. The marking detection unit (optical sensor) detects wafer markings, and the control unit (computer algorithm) calculates centering adjustments, substituting the mechanical manual centering process with an automated detection-and-control system.
2Productivity
If automatic centering method is implemented, then productivity is improved through automated handling, but device complexity increases due to additional detection and control systems
Solution Approach 1:
The marking detection unit serves multiple functions: it detects wafer presence, identifies wafer orientation, locates centering reference markings, and provides data for centering calculations. This multi-functional sensor reduces the need for separate detection devices, thereby limiting the increase in device complexity while enabling automated centering and handling.
Solution Approach 2:
The patent combines the marking detection function with the wafer inspection and positioning system. The control unit integrates marking detection data with wafer handling control, merging multiple functions into a unified automated centering system that improves productivity without proportionally increasing complexity.
3Loss of time
If conventional alignment method is used, then equipment cost is reduced, but loss of time increases due to manual centering operations
Solution Approach 1:
The wafer markings (notches, tabs, or patterns) are pre-formed during wafer manufacturing as reference features. These preliminary markings enable the automatic centering system to quickly locate and align wafers without time-consuming manual measurement and marking operations during processing.
Data Source
Figure 1A~1F
Figure 1C~1E
Figure 2A
AI summary
A substrate transport apparatus including a transport chamber, a drive section, a robot arm having an end effector at a distal end configured to support a substrate and being connected to the drive section generating at least arm motion in a radial direction extending and retracting the arm, an imaging system with a camera mounted in a predetermined location to image at least part of the robot arm, and a controller connected to the imaging system to image the arm moving to a predetermined repeatable position, the controller effecting capture of a first image of the robot arm proximate to the repeatable position decoupled from encoder data of the drive axis, wherein the controller calculates a positional variance of the robot arm from comparison of the first image with a calibration image, and from the positional variance determines a motion compensation factor changing the extended position of the robot arm.