Polishing Apparatus End-Point Detection Sensor with Pot Core
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Solution Overview
Problem
Conventional eddy current sensors used in polishing apparatuses have a broad spot diameter, limiting their ability to accurately measure film thickness, especially near the edges of semiconductor wafers, due to their large coil diameter and distance from the substrate, which affects detection accuracy and precision in end-point detection during polishing.
Innovation Solution
The polishing apparatus incorporates a pot core with a magnetic core and peripheral wall portion, arranged to reduce the distance between the sensor and the substrate, featuring a compact design with separable components to adjust for different polishing pad thicknesses, and includes a detection coil positioned closer to the substrate for enhanced sensitivity and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a conventional eddy current sensor with a large coil diameter is used, then the sensor can detect film thickness over a broad range, but the spot diameter becomes large and measurement precision is reduced
Solution Approach 1:
The sensor coil is divided into multiple independent coil units arranged in an array. Each coil unit has a small diameter and detects film thickness at a specific location. By combining measurements from multiple segmented coils, the system achieves both localized precision and broad coverage through electronic scanning or simultaneous multi-point detection.
Solution Approach 2:
The invention transitions from a single large coil detecting a broad area to multiple small coils arranged in a two-dimensional array. This dimensional transformation allows precise localization of film thickness variations across the substrate surface while maintaining comprehensive detection coverage through the array configuration.
2Area of stationary object
If the distance between the eddy current sensor and the substrate is increased, then the sensor can operate over a larger area, but the detection sensitivity and accuracy decrease
Solution Approach 1:
Multiple small-diameter coils are arranged in an array pattern, allowing each coil to maintain a small distance from the substrate for high sensitivity while collectively covering a broad detection area. The segmented coil structure enables precise local measurements that can be synthesized into comprehensive substrate-wide film thickness maps.
3Measurement precision
If the coil diameter is reduced to decrease spot diameter, then measurement precision is improved, but the distance from the substrate must be reduced which is limited by the polishing pad thickness
Solution Approach 1:
The sensor system uses multiple small-diameter coils arranged in an array, where each coil maintains an optimal small distance from the substrate (limited by polishing pad thickness) to achieve high detection accuracy. The small coil diameter ensures a concentrated magnetic flux and small spot diameter, while the array arrangement compensates for the limited working distance by providing multiple measurement points.
Solution Approach 2:
The invention moves from a single-point measurement with variable distance to a multi-point array configuration where all coils operate at a consistent, optimized distance from the substrate. This dimensional transition allows the system to maintain precise measurements across the entire substrate area without requiring variable sensor-to-substrate distances.
4Area of stationary object
If a broad detection range is used, then coverage is improved, but the ability to detect edge portions and narrow features is lost
Solution Approach 1:
The detection system is segmented into multiple coil units arranged in an array that extends to the edges of the substrate. This segmentation allows independent measurement at each location, including edge portions and narrow features, while collectively providing comprehensive coverage. The fine spatial resolution of individual coils enables detection of localized film thickness variations that would be averaged out in a broad single-coil system.
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 configuration allows for high-sensitivity measurement of film thickness in a smaller range, improving detection accuracy and enabling precise end-point detection, even near the edges of semiconductor wafers, by minimizing the spot diameter and optimizing the magnetic flux distribution.
Implementation Method 1
an exciting coil that is arranged at the magnetic core portion and configured to form eddy current in the polishing target object
Implementation Method 2
a detection coil that is arranged at the magnetic core portion or the peripheral wall portion and configured to detect the eddy current formed in the polishing target object
Data Source
AI summary
An end-point detection sensor 50 detects an end point of polishing, the end-point detection sensor 50 being arranged in a polishing table 100. The end-point detection sensor 50 has a pot core. The pot core 60 has a bottom portion 61a, a magnetic core base portion 61b and a peripheral wall base portion 61c. The end-point detection sensor 50 has an exciting coil 62, and a detection coil 63. The back surface 101b of the polishing pad 101 has a space 30 which is arranged at a portion facing the polishing table 100 and houses a magnetic core extension portion 8 and a peripheral wall extension portion 11. The magnetic core extension portion 8 and the peripheral wall extension portion 11 extending to the space 30 are located in the space 30.