Polishing Apparatus With Three-Axis Force Sensing for End-Point Control
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Solution Overview
Problem
Existing methods for determining the frictional force between a wafer and a polishing pad in a chemical mechanical polishing process are inaccurate due to machine differences and assembly variations, leading to uncertainties in controlling the polishing end point.
Innovation Solution
A polishing apparatus equipped with a three-axis sensor system to detect forces acting on the polishing head, allowing for precise monitoring and control of the frictional force, and a control device to determine the polishing end point based on threshold values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the frictional force is determined based on the torque current of the table motor, then the frictional force can be monitored during polishing, but the determination accuracy is low due to machine difference and assembly variation
Solution Approach 1:
The patent replaces the electrical measurement method (torque current monitoring) with a direct mechanical measurement method using a load cell. The load cell is installed in the head shaft to directly measure the frictional force between the wafer and polishing pad, eliminating the influence of motor characteristics and assembly variations on measurement accuracy.
Solution Approach 2:
The load cell acts as an intermediary device that directly transmits and measures the frictional force between the wafer and polishing pad. This intermediary measurement approach provides accurate frictional force data without being affected by variations in the motor or assembly components.
2Measurement precision
If a three-axis sensor is installed adjacent to the head arm to detect forces in three axial directions, then the frictional force can be accurately determined, but the device complexity increases
Solution Approach 1:
The load cell is designed to perform multiple functions: it supports the polishing head mechanically while simultaneously measuring the frictional force. This multi-functional design achieves accurate measurement without adding separate sensor systems, thereby avoiding increased device complexity.
Solution Approach 2:
The measurement function is merged into the existing head shaft structure by installing the load cell within the head shaft. This integration combines the mechanical support function and the measurement function into a single component, avoiding the need for separate sensor systems.
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
Accurate determination of the frictional force enables precise control of the polishing process, ensuring uniformity and consistency in film removal, thereby improving the accuracy of the polishing end point detection.
Implementation Method 1
a three-axis sensor arranged adjacent to the head arm and configured to detect information on forces acting on the polishing head in three axial directions
Implementation Method 2
the frictional force generated between the substrate and the polishing head, the frictional force being calculated based on a signal sent from the three-axis sensor
Data Source
AI summary
The present application relates to a polishing apparatus. The polishing apparatus includes a three-axis sensor arranged adjacent to a head arm and configured to detect information on forces in three axes directions acting on a polishing head.