Multilayer Sample Inspection via Fabry-Perot Interferometry
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Solution Overview
Problem
Conventional inspection systems are unable to correctly determine the composition and order of layers in multilayer samples during automated manufacturing processes, leading to potential manufacturing defects due to undetected orientation issues, such as upside-down samples.
Innovation Solution
A method and system utilizing a broadband light source, single mode optical fiber, beam splitter, and computer-controlled Fabry-Perot fringe analysis to determine the thickness and order of layers by measuring optical path differences and recording interferograms, allowing for accurate identification of layer compositions and orientations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional inspection systems are used to measure layer thickness, then thickness measurement capability is provided, but the ability to determine layer composition and order is lost
Solution Approach 1:
The patent transforms the inspection approach by changing the measurement parameters from simple thickness measurements to spectral reflectance measurements across multiple wavelengths. By measuring reflectance at different wavelengths and analyzing the spectral characteristics, the system can determine both thickness and composition of layers, resolving the contradiction between measuring thickness and identifying composition/order.
2Ease of operation
If conventional inspection systems measure only thickness, then measurement simplicity is maintained, but detection of orientation defects becomes impossible
Solution Approach 1:
The patent introduces spectral reflectance analysis as an intermediary measurement method. Instead of directly observing layer orientation, the system measures reflectance at multiple wavelengths and uses the spectral characteristics as intermediaries to infer both thickness and composition/order of layers, enabling defect detection while maintaining operational simplicity.
3Loss of information
If spectral analysis at multiple wavelengths is performed, then layer composition and order can be determined, but measurement complexity increases
Solution Approach 1:
The patent applies partial action by selecting specific discrete wavelengths for measurement rather than analyzing the entire spectrum. The system measures reflectance at a subset of wavelengths sufficient to distinguish between different layer compositions and orders, achieving the necessary information without the complexity of full spectral analysis.
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 precise determination of layer thicknesses and order, preventing manufacturing defects by correctly identifying layer orientations and compositions, thus ensuring accurate processing in automated manufacturing.
Implementation Method 1
emitting, from a broadband light source, light over single mode optical fiber
Implementation Method 2
receiving, at a beam splitter, the light and splitting, at the beam splitter, the light into first and second portions
Implementation Method 3
combining, at the beam splitter, the first portion of the light after being reflected from the multilayer sample and the second portion of the light after being reflected from the reflector
Implementation Method 4
spectrally analyzing the combined light using the system for analyzing Fabry-Perot fringes
Implementation Method 5
computer-controlled system for analyzing Fabry-Perot fringes, the combined light over the optical fiber and spectrally analyzing the combined light using the system for analyzing Fabry-Perot fringes
Implementation Method 6
receiving, at a computer-controlled spectrograph included in the system for analyzing Fabry-Perot fringes, the filtered light over the single-mode optical fiber, and spectrally analyzing the filtered light using the computer-controlled spectrograph
Data Source
AI summary
Inspecting a multilayer sample may include receiving, at a beam splitter, light and splitting the light into first and second portions; combining, at the beam splitter, the first portion of the light after being reflected from a multilayer sample and the second portion of the light after being reflected from a reflector; receiving, at a computer-controlled system for analyzing Fabry-Perot fringes, the combined light and spectrally analyzing the combined light to determine a value of a total power impinging a slit of the system for analyzing Fabry-Perot fringes; determining an optical path difference (OPD); recording an interferogram that plots the value versus the OPD for the OPD; performing the previous acts of the method one or more additional times with a different OPD; and using the interferogram for each of the different OPDs to determine the thicknesses and order of the layers of the multilayer sample.