CMP Eddy Current Thickness Correction for Wafer Edge Accuracy
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Solution Overview
Problem
Existing polishing apparatuses using eddy current sensors struggle with reduced accuracy in measuring film thickness at the edges of substrates due to incomplete magnetic flux utilization, leading to inaccuracies in the detection of film thickness.
Innovation Solution
A polishing apparatus equipped with an eddy current sensor that corrects film thickness measurements by determining a first distance between points on a coordinate system and the center of a circle formed by impedance components, using a correction coefficient to improve accuracy at substrate edges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If film thickness measurement is performed at edges of substrate using eddy current sensor, then measurement coverage is improved, but measurement precision deteriorates due to incomplete magnetic flux utilization
Solution Approach 1:
The patent applies parameter changes by introducing a correction coefficient that modifies the relationship between impedance values and film thickness. The correction coefficient is determined based on the distance from the substrate center, transforming the measurement parameters to compensate for edge effects. This allows accurate film thickness measurement across the entire substrate surface including edges, resolving the contradiction between expanded measurement coverage and maintained precision.
2Measurement precision
If correction coefficient is introduced to improve edge measurement accuracy, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The correction coefficient method modifies measurement parameters through software calculation rather than hardware modification. The system calculates the distance from substrate center and applies appropriate correction coefficients to impedance measurements, achieving improved edge measurement precision without adding physical components or significantly increasing device complexity.
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
Enhances the accuracy of film thickness measurements at substrate edges by correcting for inaccuracies using a correction coefficient, ensuring precise planarization in semiconductor manufacturing.
Implementation Method 1
The eddy current sensor causes the polishing target such as a conductive film to induce eddy current therein, and detects a change of thickness of the polishing target from a change of a magnetic field generated by the eddy current induced in the polishing target.
Implementation Method 2
detects a change of thickness of the polishing target from a change of a magnetic field generated by the eddy current induced in the polishing target.
Data Source
AI summary
A film thickness measuring apparatus and an end point detector monitor a film thickness of a conductive film based on an output of an eddy current sensor disposed in a polishing table. The output of the eddy current sensor includes an impedance component, and when a resistance component and a reactance component of the impedance component are associated with the respective axes of a coordinate system having two orthogonal coordinate axes, at least some points on the coordinate system corresponding to the impedance component form at least a part of a circle. The film thickness measuring apparatus determines a distance between a point on the coordinate system and the center of the circle, determines the film thickness from the impedance component and corrects the determined film thickness using the determined distance.