Eddy Current Sensor Coil Layout for Low-Noise Film Thickness Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional eddy current sensors for film thickness measurement in semiconductor polishing processes face increased noise and require frequent readjustment due to environmental changes, such as temperature variations, affecting measurement accuracy.
Innovation Solution
An eddy current sensor configuration incorporating a magnetic material with an excitation coil, detection coil, and correction coil, where the detection coil has a larger cross-sectional area and more turns than the correction coil, and both coils are wound around a magnetic material with a pod-shaped core, directly connected to an impedance converter or amplifier, reducing noise and the need for readjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an RF amplifier is used to amplify the difference between output signals of detection coil and dummy coil, then the signal can be detected, but noise is increased
Solution Approach 1:
The patent removes the RF amplifier component from the signal processing chain. Instead of using an RF amplifier to amplify the difference between detection coil and dummy coil outputs, the invention directly processes the signals without this noise-introducing component, thereby extracting the harmful amplification function while maintaining signal detection capability through alternative means.
Solution Approach 2:
The patent introduces a bridge circuit configured with a variable resistor as an intermediary element to balance the output signals from the detection coil and dummy coil. This bridge circuit serves as a mediator that equalizes the signals before further processing, eliminating the need for RF amplification and subsequent noise introduction while maintaining measurement capability.
2Measurement precision
If a bridge circuit with variable resistor is used to detect signal difference, then signal detection is enabled, but readjustment is necessary due to environmental changes
Solution Approach 1:
The patent implements a self-balancing mechanism where the bridge circuit automatically compensates for environmental changes such as temperature variations. The system uses the variable resistor in the bridge circuit to maintain balance between detection coil and dummy coil outputs without requiring external manual readjustment, enabling the system to self-correct for environmental drift.
Solution Approach 2:
The patent employs a feedback mechanism through the bridge circuit that continuously monitors and balances the output signals from the detection coil and dummy coil. This feedback system automatically adjusts for environmental changes by maintaining signal balance, eliminating the need for periodic manual readjustment and ensuring consistent measurement accuracy under varying conditions.
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 the sensitivity of the detection coil, stabilizes film thickness measurements, and reduces noise, providing improved accuracy and reliability in film thickness detection.
Implementation Method 1
The eddy current sensor has an excitation coil that generates a magnetic flux. The eddy current sensor generates an eddy current in the conductive film by overlapping (interlinking) a part of the generated magnetic flux over the conductive film of the substrate.
Implementation Method 2
The detection coil and the correction coil are wound to surround the first pillar and/or the external wall. The detection coil and the correction coil detect a change in the eddy current generated in the conductive film.
Data Source
AI summary
Provided is an eddy current sensor having an improved sensitivity in a detection coil of the eddy current sensor compared with a conventional one. An eddy current sensor (210) includes a magnetic material, a detection coil (34), a correction coil (166), and an excitation coil. The excitation coil is wound to surround the first pillar and/or the external wall of the magnetic material and generates an eddy current in a conductive film. The detection coil (34) and the correction coil (166) are wound to surround the first pillar and/or the external wall and detects a change in the eddy current generated in the conductive film. An amount of change in an output signal of the correction coil (166) when the eddy current generated in the conductive film changes is less than an amount of change in an output signal of the detection coil (34). One end of the correction coil (166) is directly connected to one end of the detection coil (34), and another end of the correction coil and another end of the detection coil are directly connected to an impedance converter (124) or an amplifier.