Wafer Centering With Vision-Based Robot Arm Motion 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, ensuring accurate substrate placement across varying thermal conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical sensors and encoder data are used to determine substrate position, then position compensation can be provided, but the process becomes difficult and cumbersome and processing time increases
Solution Approach 1:
The patent extracts the position measurement function from the encoder system and implements it through a separate vision system. The vision system independently captures images of the substrate and robot arm, processes these images to determine position, and provides compensation without relying on encoder data, thereby simplifying the process and reducing processing time while maintaining measurement precision
Solution Approach 2:
The vision system acts as an intermediary between the robot arm and the substrate positioning control. Instead of directly using encoder data from the robot controller, the vision system captures images, processes them through image analysis algorithms, and provides position information that mediates the positioning process, making it less cumbersome and faster
2Manufacturing precision
If thermal effects are not compensated for, then the system is simpler, but substrate placement accuracy deteriorates due to thermal expansion and contraction of robot components
Solution Approach 1:
The vision system performs self-service by automatically capturing images, processing them through algorithms that detect thermal-induced position changes, and computing compensation values. This self-service capability allows the system to compensate for thermal effects without requiring complex external monitoring equipment or manual intervention, thereby improving substrate placement accuracy while limiting the increase in system complexity
Solution Approach 2:
The patent replaces mechanical thermal compensation mechanisms (such as expansion joints or active heating/cooling systems) with an optical vision-based measurement and compensation system. This substitution uses image processing and computational methods instead of mechanical adjustments, improving precision while keeping the system relatively simple
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 enhances substrate placement accuracy by decoupling motion compensation from encoder data, providing improved precision and reducing processing time, with the imaging system effectively mitigating thermal and other environmental impacts on robot arm positioning.
Implementation Method 1
an imaging system that captures images of the robot arm and compares them to calibration images to determine positional variances
Data Source
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.