Eddy Current Sensor Trajectory Identification for CMP Endpoint Detection
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Solution Overview
Problem
Eddy current sensors in substrate polishing apparatuses face challenges in accurately detecting the substrate polishing endpoint due to signal amplitude changes caused by factors other than conductive layer thickness, requiring precise specification of the sensor's trajectory to ensure high accuracy.
Innovation Solution
A method is developed to identify the trajectory of the eddy current sensor by obtaining a sensor output map as three-dimensional data, extracting a trajectory with a profile most similar to the real-time polishing signal, and normalizing amplitudes to determine similarity, allowing for accurate endpoint detection and progress monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If eddy current sensor is used to detect substrate polishing endpoint, then polishing progress can be monitored, but signal amplitude changes due to factors other than conductive layer thickness reduce detection accuracy
Solution Approach 1:
The system continuously monitors the eddy current sensor signal during polishing and compares it against reference data. The controller uses this feedback to distinguish between signal changes caused by polishing progress versus those caused by other factors like substrate position or sensor trajectory variations, thereby maintaining accurate endpoint detection despite signal amplitude fluctuations
Solution Approach 2:
The system changes the parameter being measured from raw signal amplitude to a normalized polishing progress metric. By transforming the signal through comparison with reference data and calculating polishing progress as a ratio, the system eliminates the effect of amplitude variations while preserving the information about actual polishing advancement
2Measurement precision
If trajectory of eddy current sensor is not precisely specified, then device operation is simpler, but polishing endpoint detection accuracy deteriorates
Solution Approach 1:
The system creates a reference copy of the eddy current sensor signal obtained under known conditions (before polishing or from a reference substrate). This reference signal serves as a template against which actual polishing signals are compared, allowing the system to identify trajectory effects without needing to physically track or specify the sensor trajectory during polishing
Solution Approach 2:
The system performs preliminary measurement to obtain reference data before the actual polishing process. This reference data captures the sensor signal characteristics including trajectory effects, which are then used during polishing to compensate for trajectory variations without requiring real-time trajectory specification or adjustment
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 enables precise detection of the substrate polishing endpoint and monitoring of polishing progress, improving the accuracy and reliability of the CMP process.
Implementation Method 1
The eddy current sensor is configured to detect a thickness of a conductive layer on a substrate surface
Data Source
AI summary
To specify a trajectory of an eddy current sensor provided on a polishing table of a substrate polishing apparatus, disclosed is a method of identifying a trajectory of an eddy current sensor as seen from a substrate in a substrate polishing apparatus having a polishing table and a polishing head. The method includes: obtaining a sensor output map as three-dimensional data; polishing the substrate; obtaining a profile of the real-time polishing signal as two-dimensional data; and extracting a trajectory having a profile most similar to the profile of the real-time polishing signal as two-dimensional data from the sensor output map as three-dimensional data and identifying the extracted trajectory as a trajectory of the eddy current sensor as seen from the substrate.