Eddy Current Thickness Sensor for Discrete Conductive Features
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Solution Overview
Problem
Current Eddy current sensors face challenges in accurately measuring the thickness of discrete conductive features due to weak and noisy signals, compromising their accuracy.
Innovation Solution
A thickness sensor with a small sensor spot size, comprising a driver, drive coil, Eddy current reader, and processor, which generates and measures Eddy currents to produce a signal with increased spatial resolution, amplifying peaks and valleys to accurately determine the thickness of discrete conductive features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current Eddy current sensors are used to measure discrete conductive features, then the measurement capability is provided, but the signal strength becomes weak and noisy, compromising accuracy
Solution Approach 1:
The sensor system uses a small sensor spot size to concentrate the measurement on a localized discrete conductive feature, improving signal quality by focusing the Eddy current interaction on the specific feature being measured rather than averaging over a large area
Solution Approach 2:
The system dynamically adjusts measurement parameters and processes signals in real-time during the measurement process, optimizing signal quality and accuracy for each discrete feature measurement
2Measurement precision
If a small sensor spot size is used, then spatial resolution is improved and signal quality is enhanced, but the sensor coverage area is reduced
Solution Approach 1:
The measurement process is divided into multiple sequential scans across the wafer surface, with each scan covering a portion of the discrete conductive features. The small sensor spot size provides high spatial resolution for each segment, and the complete picture is reconstructed by combining results from multiple scans
Solution Approach 2:
The system compensates for the reduced sensor coverage area by adding the dimension of time through multiple sequential scans. Instead of covering a large area simultaneously, the sensor systematically scans across different regions, achieving complete coverage through temporal progression
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
The sensor provides accurate thickness measurements of discrete conductive features, enhancing spatial resolution and reducing noise, making it suitable for in-situ monitoring during polishing processes like CMP.
Implementation Method 1
The driver 12 generates and provides a driving signal to the drive coil 14. In some embodiments the driving signal is an alternating current (AC) signal. In response to receiving the driving signal, the drive coil 14 generates a magnetic field 22. When the thickness sensor 10 is disposed above or near a plurality of discrete conductive features substantially at a same level on a substrate which are separated by one or more regions of non-conductive material at substantially the same level as the discrete conductive features, the magnetic field 22 generates Eddy currents in the plurality of conductive features.
Implementation Method 2
the magnetic field 22 generates Eddy currents in the plurality of conductive features. For example, in the embodiment shown in FIG. 1, when the thickness sensor 10 is disposed above or near a discrete conductive feature 24 on a substrate 26, the magnetic field 22 generates an Eddy current 28 in the discrete conductive feature 24. The Eddy current 28, in turn, generates a secondary magnetic field 30.
Data Source
AI summary
Various embodiments provide a thickness sensor and method for measuring a thickness of discrete conductive features, such as conductive lines and plugs. In one embodiment, the thickness sensor generates an Eddy current in a plurality of discrete conductive features, and measures the generated Eddy current generated in the discrete conductive features. The thickness sensor has a small sensor spot size, and amplifies peaks and valleys of the measured Eddy current. The thickness sensor determines a thickness of the discrete conductive features based on a difference between a minimum amplitude value and a maximum amplitude value of the measured Eddy current.