Polishing Apparatus Swing Arm Radius Determination
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Solution Overview
Problem
Existing polishing apparatuses face challenges in determining the radius of a wafer from its center when the swing arm is swung during polishing, making it difficult to accurately measure changes in the wafer's state and control the supply of polishing liquids.
Innovation Solution
A configuration that includes a distance determining section to calculate the distance from the axis of rotation to the measuring section, allowing for precise determination of the wafer's radius and enabling accurate end-point detection of polishing based on physical quantity measurements and determined distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the swing arm is swung during polishing, then the measurement track becomes curves of various sizes passing through points other than the center, but the radius from the center cannot be uniquely determined
Solution Approach 1:
The patent transitions from one-dimensional radial measurement to two-dimensional coordinate-based measurement. By determining both the angle of rotation of the polishing table and the swinging angle of the swing arm, the system calculates the sensor position using coordinates (Rs*cos(θs), Rs*sin(θs)) relative to the wafer center, enabling unique radius determination even when the swing arm moves.
Solution Approach 2:
The system continuously monitors the angle of rotation of the polishing table and the swinging angle of the swing arm, using this feedback information to dynamically calculate the sensor's position and the corresponding radius from the wafer center, ensuring accurate measurement throughout the polishing process.
2Area of stationary object
If the sensor measures wafer state at varying radii when swing arm is swung, then measurement coverage increases, but the ability to detect changes at the same radius is lost
Solution Approach 1:
The system uses feedback from angle sensors to continuously track the sensor position and identifies measurement points at the same radius by comparing calculated radius values. This enables comparison of wafer state changes at identical radii even as the swing arm moves, maintaining measurement precision while expanding coverage.
Solution Approach 2:
By adding the angular dimension to the measurement system, the patent enables comprehensive mapping of wafer properties across different radial positions and angular positions, allowing for both expanded coverage and precise change detection through coordinate-based analysis.
3Quantity of substance
If liquid supply timing is not precisely controlled when swing arm is swung, then liquid may be supplied outside the wafer area, but precise timing control becomes difficult
Solution Approach 1:
The system uses real-time feedback from angle sensors monitoring both the polishing table rotation and swing arm movement to dynamically calculate when the sensor enters and exits the wafer area. This feedback mechanism automatically adjusts liquid supply timing, making precise control achievable despite the complex swinging motion.
Solution Approach 2:
The system calculates the expected entry and exit times of the sensor relative to the wafer area in advance based on the known swing arm trajectory and polishing table speed, preparing the liquid supply system to activate and deactivate at the correct moments before the sensor actually enters or exits the measurement zone.
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 detection of the polishing end-point and appropriate liquid supply timing, even when the swing arm is swung, ensuring consistent polishing quality and preventing over- or under-polishing.
Implementation Method 1
an end point detection apparatus using an optical end point detection sensor
Implementation Method 2
an eddy current end point detection sensor
Data Source
AI summary
A polishing table holds a polishing pad. A top ring holds a semiconductor wafer. A swing arm holds the top ring. The swing arm swings around a swing center on the swing arm during polishing. An optical sensor is disposed on the polishing table and measures an optical characteristic changeable in accordance with a variation in film thickness of the semiconductor wafer. A fluid supply control apparatus determines a distance from an axis of rotation to the optical sensor when the semiconductor wafer is rotated by the top ring. An end point detection section detects a polishing end point indicating an end of polishing based on the optical characteristic measured by the optical sensor and the determined distance.