Polishing Apparatus Swing Arm Torque Detection
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Solution Overview
Problem
The existing polishing apparatuses face challenges in accurately detecting the end point of polishing, especially when the swing arm is in motion, due to noise and fluctuation in motor current, leading to potential over- or under-polishing issues.
Innovation Solution
A configuration that includes a polishing apparatus with a detection section to increase the change amount of the output signal while swinging the polishable object around the swing center, allowing for improved detection of frictional force changes between the polishing pad and the object, synchronized with the swing motion and arm torque fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If motor current is used to detect polishing end point, then detection method is simple, but noise and fluctuation occur when swing arm is in motion reducing detection accuracy
Solution Approach 1:
The patent introduces a swing arm torque detection mechanism as an intermediary element to detect polishing end point. Instead of directly using motor current which is noisy during swing motion, the system detects torque on the swing arm through a torque sensor, providing a cleaner signal that accurately reflects frictional force changes during polishing while the swing arm is in motion.
2Area of stationary object
If swing arm is used to hold top ring, then polishing coverage is improved, but torque current fluctuation increases making end point detection difficult
Solution Approach 1:
The patent extracts the torque detection function from the motor current measurement system. By placing a dedicated torque sensor on the swing arm, the system separates torque detection from the noisy motor control circuitry, enabling accurate measurement of frictional force changes even while the swing arm is actively moving and providing broad polishing coverage.
3Manufacturing precision
If polishing is performed with swing arm motion, then polishing uniformity is improved, but frictional force signal becomes noisy reducing detection sensitivity
Solution Approach 1:
The patent uses the swing arm torque sensor as an intermediary that directly measures frictional force changes at the point of contact between the polishing pad and workpiece. This direct measurement approach maintains high detection sensitivity even during swing arm motion, allowing the system to benefit from improved polishing uniformity while accurately detecting end point through frictional force changes.
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 the accuracy of polishing end point detection, reducing noise and improving sensitivity to frictional force changes, thereby preventing over- or under-polishing.
Implementation Method 1
a detection section configured to detect a change in a frictional force between the polishing pad and the polishable object
Implementation Method 2
a third electric motor configured to swing the swing arm around a swing center on the swing arm
Data Source
AI summary
A polishing pad is held using a polishing table. The polishing table is driven to rotate using a first electric motor. The top ring for holding a semiconductor wafer and pressing the top ring against a polishing pad is driven to rotate by a top ring motor. The top ring is held by the swing arm. The swing arm is made to swing around a swing center on the swing arm by a swing shaft motor. A first output is generated by detecting a current value of the swing shaft motor. While polishing the semiconductor wafer by causing the semiconductor wafer to swing around the swing center on the swing arm, a change of a frictional force between the polishing pad and the semiconductor wafer is detected by increasing a change amount of the first output.