Stationary Camera Array for Wafer Metrology at High Transfer Speeds
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Solution Overview
Problem
High-speed wafer transfer in semiconductor processing hampers accurate in-situ measurement of wafer geometry, particularly film layer concentricity and width, due to motion-induced image distortion, necessitating a method to correct for distortion without slowing down the wafer motion.
Innovation Solution
A system with a camera and light source array positioned to capture undistorted images of the wafer in motion, utilizing an image control processor to correct for velocity-induced distortion by accessing robot motion data, adjusting frame rates, and using diffused light to ensure accurate imaging across the wafer diameter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the wafer is imaged during high-speed transfer, then productivity is maintained, but image distortion occurs due to motion
Solution Approach 1:
The system uses robot position feedback to dynamically adjust camera frame timing and image processing parameters. By receiving real-time position data from the robot controller, the system compensates for motion-induced distortion through coordinate transformation and selective frame capture, enabling accurate measurements during high-speed wafer transfer
Solution Approach 2:
The system dynamically changes camera parameters including frame rate, exposure timing, and trigger intervals based on robot position and speed. By adjusting these parameters in response to motion conditions, the system maintains image accuracy throughout the wafer transfer process without reducing transfer speed
2Measurement precision
If the wafer is slowed down or stopped for imaging, then image accuracy is improved, but productivity decreases
Solution Approach 1:
The system maintains continuous wafer transfer motion during image capture by synchronizing camera frame acquisition with robot position. Instead of stopping or slowing the wafer, the system continuously images while the wafer moves, using motion compensation algorithms to maintain accuracy throughout the transfer process
Solution Approach 2:
The system pre-synchronizes camera triggering with robot position data and pre-calculates coordinate transformation parameters based on expected motion trajectories. This preliminary preparation enables real-time compensation during imaging without interrupting the transfer process
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
Enables accurate measurement of wafer geometry and defect detection without interrupting high-speed wafer transfer, improving productivity by maintaining continuous motion during imaging.
Implementation Method 1
A camera is stationed at a fixed position and facing a transit path portion of the workpiece transit path
Implementation Method 2
A light source is provided at a fixed position facing the transit path portion and comprising an elongate light emitting array
Data Source
AI summary
A metrology system has an elongate stationary camera pixel array facing a workpiece transit path of a robot with an field of view corresponding to a workpiece diameter and extending transverse to the transit path portion, and a stationary elongate light emitting array generally parallel to the pixel array. An image control processor causes the camera to capture successive image frames while the robot is moving the workpiece through the transit path.