Ellipsometric Coating Thickness Measurement on Moving Substrates
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Solution Overview
Problem
Current methods for measuring thin film or coating thickness, especially those below 0.2 microns, are unreliable and not suited for real-time in-process measurement on moving substrates, particularly in industrial production environments, and are limited by their requirement for static substrates.
Innovation Solution
A system utilizing a broadband light source, polarizers, wave plates, rotating analyzers, and detectors, coupled with a computer-controlled adjustment mechanism, measures the phase shift and polarization changes of reflected light to determine coating thickness in real-time on moving substrates, ensuring accurate measurements despite substrate movement and potential disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard reflectometry based measurement techniques are used, then measurement is possible for thicker coatings, but measurement becomes unreliable when coating thickness is below 200 nanometers
Solution Approach 1:
The invention changes the measurement parameters by using elliptically polarized light instead of standard reflectometry, and by measuring multiple ellipsometric parameters (psi and delta) across multiple wavelengths to achieve reliable measurements of ultra-thin coatings below 200 nanometers
Solution Approach 2:
The invention introduces an intermediary modeling-based approach that correlates ellipsometric measurements with coating thickness through mathematical models, enabling indirect but accurate measurement of ultra-thin coatings that cannot be measured directly by standard reflectometry
2Measurement precision
If modeling-based reflectometry techniques are used for coatings less than 0.2 microns, then measurement precision is improved, but the technique requires static substrates and is not suitable for moving substrates
Solution Approach 1:
The invention makes the measurement system dynamic by implementing real-time measurements on moving substrates through synchronized detection and data processing that accounts for substrate motion, transforming a static measurement technique into a dynamic one suitable for industrial production environments
Solution Approach 2:
The invention incorporates feedback mechanisms through real-time measurement and processing of ellipsometric data from moving substrates, allowing continuous monitoring and adjustment to maintain measurement precision despite substrate motion and environmental variations
3Productivity
If real-time in-process measurement is implemented on moving substrates, then productivity is improved, but measurement reliability deteriorates due to substrate movement and disturbances
Solution Approach 1:
The invention performs preliminary actions by pre-configuring the optical system with polarizers, wave plates, and detectors positioned to capture ellipsometric parameters before substrate motion introduces measurement errors, and by pre-establishing measurement protocols that account for expected motion variations
Solution Approach 2:
The invention provides beforehand cushioning through error compensation algorithms and robust measurement techniques that anticipate and counteract the effects of substrate motion and environmental disturbances, maintaining measurement reliability despite the dynamic measurement 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
Enables real-time, inline measurement of thin film or coating thickness on moving substrates, preventing equipment damage by maintaining optimal coating thickness, reducing material waste, and providing immediate feedback for process adjustments.
Implementation Method 1
configuring a light source to generate light waves within a particular spectrum range; linearly polarizing the light waves provided by the light source through a polarizer; converting the linearly polarized light waves to circularly polarized light waves by passing the linearly polarized light waves through a wave plate
Implementation Method 2
circularly polarized light waves reflected by the coated substrate are converted to elliptically polarized reflected light waves
Implementation Method 3
measuring the phase shift and polarization changes of reflected light to determine coating thickness; Two ellipsometric parameters ψ and Δ are calculated from these three electrical signals (I1-I3)
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
The present disclosure is generally directed to methods and systems for measuring the thickness of coatings or thin films on various substrates. For example, one disclosed method includes the steps of providing and directing light waves of varying wavelengths toward a moving substrate comprising a coating, linearly polarizing the light waves, converting the linearly polarized light waves to circularly polarized light waves, analyzing elliptically polarized light waves reflected by the moving substrate, capturing analyzed light waves, generating light wave data based on the captured light waves, and determining a thickness of the coating based on the light wave data.