Eddy Current Sensor Edge Resolution via Segmented Cores
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Solution Overview
Problem
Existing semiconductor processing methods face challenges in accurately determining the thickness of conductive layers, particularly at the edge of substrates during chemical mechanical polishing, due to difficulties in measuring non-uniformities and maintaining precision amidst substrate movement and vibration.
Innovation Solution
An eddy current monitoring system with elongated core portions arranged to follow the curvature of the substrate and positioned in a figure-eight configuration with opposing coils, allowing for precise measurement of conductive layer thickness by inducing magnetic fields and averaging thickness measurements along the substrate edge, thereby reducing sensitivity to movement and vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional eddy current sensor with single core portion is used, then the measurement is simple, but the measurement precision at substrate edge is insufficient
Solution Approach 1:
The sensor core is divided into multiple core portions (first core portion and second core portion) positioned at different distances from the substrate edge. This segmentation allows each core portion to independently measure thickness at different locations, with the first core portion specifically capturing edge region data and the second core portion capturing center region data, thereby improving overall measurement precision at the substrate edge.
Solution Approach 2:
Different core portions are positioned at different locations relative to the substrate edge to provide location-specific measurement capabilities. The first core portion is positioned closer to the substrate edge to capture edge region thickness variations, while the second core portion is positioned farther away to capture center region thickness, ensuring that each region is measured with appropriate sensitivity.
2Productivity
If the substrate moves during measurement, then the measurement speed is improved, but the measurement precision deteriorates due to vibration and movement
Solution Approach 1:
By dividing the measurement into multiple core portions that can be independently positioned, the system can selectively use the first core portion for edge measurements and the second core portion for center measurements. This segmentation allows continuous measurement during substrate movement without sacrificing precision, as each core portion provides stable reference points for its respective measurement zone.
Solution Approach 2:
The system processes signals from multiple core portions to determine thickness at different locations, using the relative positioning information to compensate for substrate movement and vibration. By comparing measurements from the first and second core portions, the system can identify and correct for movement-induced errors, maintaining measurement precision during high-speed operation.
3Measurement precision
If core portions are positioned closer to the substrate edge, then the edge measurement capability is improved, but the sensitivity to vibration increases
Solution Approach 1:
The measurement system is segmented into multiple core portions with different positioning strategies. The first core portion is positioned closer to the substrate edge to capture edge thickness variations, while the second core portion is positioned farther away to provide a more vibration-resistant reference measurement. This segmentation allows the system to benefit from both edge-proximity measurements and stable reference measurements.
Solution Approach 2:
The second core portion acts as an intermediary reference that is less sensitive to vibration. By comparing measurements from the first core portion (edge-proximity, high edge-resolution) with the second core portion (center-positioned, low vibration sensitivity), the system can compensate for vibration effects while maintaining edge measurement capability.
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 enhances measurement accuracy and spatial resolution, enabling more precise adjustment of processing parameters and improving within-wafer and wafer-to-wafer uniformity by providing consistent thickness data near the substrate edge.
Implementation Method 1
an eddy current sensing system may be used to induce eddy currents in a conductive region on the substrate to determine parameters such as the local thickness of the conductive region
Implementation Method 2
A coil can be coupled with the core portions. The coil can be driven by a current source and a sense system can derive a characteristic of a conductive region on the substrate from eddy currents induced in the conductive region by the coil
Data Source
AI summary
An apparatus for monitoring the thickness of a conductive layer on a substrate includes a support to hold a substrate having a conductive layer, an eddy current monitoring system including a first plurality of core portions, and a motor to cause relative motion between the support and the eddy current monitoring system such that the substrate moves across the first plurality of core portions in a direction that defines a first axis. At least one core portion is positioned further from a second axis than at least two other core portions. The second axis is orthogonal to the first axis.