Wafer Handling Robot Tilt Sensing for Precise End Effector Leveling
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Solution Overview
Problem
Wafer handling robots face challenges with precision due to mechanical stack-up and deflection issues from multiple arm links, leading to increased costs and potential collisions, as conventional systems rely heavily on kinematic models and encoders that fail to account for manufacturing tolerances and deflection.
Innovation Solution
Incorporation of a tilt sensor, such as a gravitational field sensor like an accelerometer or inclinometer, to provide real-time feedback on the orientation of the robot arm relative to Earth's gravity, allowing the mechanism to pivot and adjust the robot arm to maintain a horizontal pitch angle within threshold limits, enhancing precision and reducing mechanical stack-up.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple robot arm links are used to transport wafers, then the robot can reach various positions and orientations, but mechanical stack-up and deflection issues increase, reducing placement precision
Solution Approach 1:
A tilt sensor is integrated into the robot arm to provide real-time feedback on the orientation and pitch angle of the wafer holder. This feedback loop allows the control system to detect deviations from the desired horizontal orientation and automatically adjust the arm position to maintain precision, compensating for mechanical stack-up and deflection errors
Solution Approach 2:
The patent replaces reliance on purely mechanical precision (kinematic models and encoders) with a sensor-based gravitational reference system. The tilt sensor uses Earth's gravitational field as a stable reference to directly measure orientation, substituting mechanical precision requirements with sensor-based orientation detection
2Device complexity
If conventional kinematic models and encoders are used for control, then the system structure remains simple, but precision is reduced due to inability to account for manufacturing tolerances and deflection
Solution Approach 1:
The tilt sensor provides continuous feedback on the actual orientation of the wafer holder relative to gravitational vertical. This feedback enables the control system to detect and correct for manufacturing tolerances and deflection in real-time, maintaining precision without requiring overly complex mechanical structures or tight tolerances
3Adaptability or versatility
If robot arm links are extended to reach various positions, then versatility increases, but mechanical deflection and stack-up errors increase, reducing reliability
Solution Approach 1:
The tilt sensor continuously monitors the orientation of the wafer holder during transport to various positions. By providing real-time feedback on pitch and roll angles, the system can detect deflection and stack-up errors that occur during extended reach operations and make corrective adjustments, maintaining reliability across the full range of motion
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 solution improves precision and reduces the likelihood of collisions by actively maintaining the wafer's horizontal orientation, ensuring accurate placement and reducing mechanical stress on the robot arm, thereby enhancing operational reliability and reducing costs.
Implementation Method 1
The tilt sensor may be a gravitational field sensor configured to detect orientation relative to the Earth's gravitational field
Implementation Method 2
The tilt sensor may be an accelerometer
Data Source
AI summary
Disclosed are techniques and systems for automatically determining and correcting the levelness of a wafer handling robot end effector. The systems may use a tilt sensor or a gravitational field sensor which may be calibrated to the wafer handling robot. The output from the tilt sensor may be used to determine or estimate the tilt of an end effector of the wafer handling robot and to perform correctional positioning to reduce or eliminate the tilt, to automatically teach certain positions that have reduced tilt, to perform health checks on the robot, provide feedback to a user, etc.