Spectroscopic Thickness Measurement Using Polarization Maintaining Fiber
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Solution Overview
Problem
Current methods for measuring the thickness and topography of slabs, particularly in semiconductor materials, face challenges in precision and accuracy, especially for materials with varying refractive indices and rough interfaces, limiting their application in advanced device processing.
Innovation Solution
A spectroscopic system employing a polarization maintaining optical fiber and a PMFBS filter is used to collect and process signals, enabling precise measurement of thickness and topography by analyzing the fringe patterns in the reflected light spectrum, which helps in determining the distance and refractive index differences between material layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional measurement methods are used for thickness and topography, then the measurement process is simple, but the measurement precision deteriorates for materials with varying refractive indices and rough interfaces
Solution Approach 1:
The patent changes the measurement parameters by using spectral interferometry instead of conventional single-wavelength methods. The system measures thickness by analyzing interference patterns across multiple wavelengths, transforming the measurement approach from direct geometric measurement to spectral analysis, which resolves the precision issue for complex materials.
Solution Approach 2:
The patent introduces an optical interferometry system as an intermediary measurement mechanism. By using light interference patterns as a mediator between the measurement system and the material properties, the system achieves high precision for thickness and topography measurements without direct physical contact or complex mechanical setups.
2Measurement precision
If conventional methods are used for measuring topography and thickness, then the equipment is simple, but the accuracy deteriorates for layered materials with rough interfaces
Solution Approach 1:
The system transforms topography measurement from direct spatial measurement to spectral domain analysis. By measuring interference patterns across a spectrum of wavelengths and converting them to spatial information through Fourier transformation, the system achieves high precision for rough interfaces and layered structures.
Solution Approach 2:
The patent replaces mechanical measurement systems with optical interferometry. Instead of using physical probes or mechanical contact methods, the system uses light waves to probe the material surface, eliminating mechanical complexity while achieving superior measurement precision for topography and interface roughness.
3Manufacturing precision
If standard optical measurement systems are used, then the system configuration is simple, but the measurement accuracy deteriorates for materials with varying refractive indices
Solution Approach 1:
The system measures thickness by analyzing the spectral interference pattern caused by varying refractive indices. Instead of assuming uniform material properties, the system captures the spectral variations and uses them to calculate accurate thickness measurements that account for refractive index changes within the material layers.
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 approach provides accurate and precise measurements of thickness and topography, even for materials with complex interfaces, enhancing the capability for advanced device processing and micro-electromechanical-systems applications.
Implementation Method 1
analyzing the fringe patterns in the reflected light spectrum
Implementation Method 2
polarization maintaining optical fiber
Data Source
AI summary
We describe apparatus for measurement of thickness and topography of slabs of materials employing probes with filters using polarization maintaining fibers.