Inductive Wafer Plating Sensor Interface for Low-Noise Thickness Measurement
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Solution Overview
Problem
Conventional inductance sensors for measuring the thickness of plating on semiconductor wafers suffer from narrow measurement bands, excessive noise, and drift, making accurate determination of electrical conductivity challenging.
Innovation Solution
A sensor interface comprising an inductance to digital converter (LDC), microcontroller (MCU), digital to analog converter (DAC), and amplifier is used to convert oscillation frequency data into a 0-10V analog signal, enabling precise measurement of plating thickness up to 10 μm with reduced noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional inductance sensors and analog circuits are used for measuring plating thickness, then the measurement setup is simple, but the measurement range is narrow and the precision is poor due to noise and drift
Solution Approach 1:
The patent replaces conventional analog inductance sensing circuits with a digital measurement system based on inductance-to-digital converters (LDC). This substitution eliminates analog noise and drift issues while providing high-resolution digital output for accurate plating thickness measurement across an extended range up to 10 μm
Solution Approach 2:
The patent changes the operating parameters of the inductance sensor by using variable frequency excitation signals and implementing digital signal processing. This allows the system to maintain high measurement precision across a broader plating thickness range by adapting measurement parameters dynamically
2Adaptability or versatility
If conventional analog sensors are used, then the device complexity is low, but the measurement range is limited and noise susceptibility is high
Solution Approach 1:
The patent implements a multi-functional sensor interface that combines LDC, microcontroller, DAC, and amplifier components to create a universal measurement system. This system can measure plating thickness across a wide range (including up to 10 μm) while providing both digital and analog output options, making it adaptable to different measurement requirements
Solution Approach 2:
The patent introduces intermediate conversion stages (inductance-to-digital converter and digital-to-analog converter) that bridge the gap between the sensor output and the measurement system. These intermediaries enable extended measurement range and reduced noise while maintaining system manageability through modular architecture
3Reliability
If analog circuits are used for inductance measurement, then the system is simple, but the measurements are susceptible to excessive noise and drift
Solution Approach 1:
The patent replaces vulnerable analog measurement circuits with a digital-based inductance measurement system using LDC. This substitution fundamentally improves measurement reliability by eliminating analog noise and drift, providing stable and repeatable measurements across the extended plating thickness range
Solution Approach 2:
The patent implements feedback mechanisms through the microcontroller that monitor and compensate for measurement variations. The system uses digital signal processing and adaptive algorithms to maintain high measurement stability and reliability, correcting for environmental factors and sensor variations in real-time
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 system provides a broader measurement range and reduces noise, allowing for accurate thickness measurement of up to 10 μm, improving electrical conductivity assessment.
Implementation Method 1
an inductance sensor and an analog circuit... These circuits sensors are only able to target a narrow functional band of measurement when determining the thickness of plate up on wafers
Data Source
AI summary
A sensor interface configured to determine a thickness of plating on a wafer, including an inductance to digital converter (LDC) configured to receive an input from a coil sensor, and configured to convert the input to data, a microcontroller (MCU) configured to receive the data, a digital to analog convertor (DAC) configured to convert the data to an analog signal, and an amplifier configured to output a 0-10V analog signal. Further, a method of using the sensor interface including converting an oscillation frequency into data with the LDC, reading the data into the MCU, converting the data to an analog signal with the DAC, providing a selectable voltage offset and gain of the analog signal with the amplifier, outputting a 0-10V analog signal with the amplifier, and determining the thickness of plating on the wafer.