Substrate Inspection Using Fluorescent Imaging and Optical Coherence Tomography
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Solution Overview
Problem
Existing methods for inspecting the thickness of conformal coated films on substrates, such as 2D photographic inspection and optical coherence tomography, are inadequate for accurately measuring thin films and suffer from inefficiencies and limitations in depth resolution and measurement range.
Innovation Solution
A substrate inspection apparatus that combines ultraviolet light for fluorescent imaging with optical coherence tomography (OCT) to measure film thickness, using a processor to identify regions of interest and derive thickness based on optical interference data, with the ability to measure films as thin as 30 µm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If 2D photographic inspection is used to inspect coated film thickness, then the inspection process is simple, but the measurement accuracy is insufficient and cannot accurately measure thin films
Solution Approach 1:
The patent combines 2D photographic inspection with optical coherence tomography (OCT) to create a hybrid inspection system. The 2D image provides qualitative assessment while OCT provides quantitative thickness measurement, merging the simplicity of photographic inspection with the precision of tomographic imaging to resolve the contradiction between ease of manufacture and measurement precision.
Solution Approach 2:
The patent introduces OCT as an intermediary measurement technique that bridges the gap between simple 2D photography and complex traditional microscopy. OCT serves as a mediator that provides accurate thickness measurement for thin films without requiring the complexity of confocal microscopes, thus improving measurement precision while maintaining relative simplicity.
2Measurement precision
If confocal microscope is used to inspect coated film thickness, then the measurement accuracy is improved, but the measurement time increases significantly
Solution Approach 1:
The patent extracts the thickness measurement function from the complex confocal microscope system and implements it through OCT technology. By taking out the specific measurement task and solving it through a different technological approach (OCT), the system achieves comparable or superior measurement accuracy with significantly reduced measurement time, as OCT can rapidly acquire depth information without the mechanical scanning requirements of confocal microscopes.
3Measurement precision
If OCT is used to inspect coated film thickness, then the depth measurement capability is improved, but saturation occurs at electrode parts making accurate measurement difficult
Solution Approach 1:
The patent applies local quality by using 2D photographic inspection for regions with electrodes where OCT would saturate, and reserving OCT for regions where depth measurement is needed and saturation is not an issue. This localized application strategy allows the system to leverage the strengths of each technique while avoiding their respective weaknesses, achieving accurate measurement across different substrate regions.
4Measurement precision
If traditional OCT is used for thickness measurement, then depth resolution is improved, but the measurement range is limited
Solution Approach 1:
The patent transitions from one-dimensional OCT depth measurement to two-dimensional imaging by combining OCT with 2D photographic inspection. This dimensional expansion allows the system to achieve both high depth resolution through OCT and extended measurement range through the broader contextual information provided by the 2D image, effectively resolving the contradiction between depth resolution and measurement range.
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
Accurately measures thin coated film thickness with improved efficiency and reduced measurement time compared to existing methods, while overcoming limitations of 2D photographic inspection and OCT.
Implementation Method 1
a first light source configured to radiate an ultraviolet light onto a coated film of a substrate, the coated film being mixed with fluorescent pigments; a first light detector configured to capture fluorescence generated from the coated film onto which the ultraviolet light is radiated
Implementation Method 2
a second light source configured to radiate a laser light onto the coated film of the substrate; a second light detector configured to obtain optical interference data generated from the coated film by the laser light
Data Source
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AI summary
A substrate inspection apparatus is disclosed. The substrate inspection apparatus includes: a first light source configured to radiate an ultraviolet light onto a coated film of a substrate, the coated film being mixed with fluorescent pigments; a first light detector configured to capture fluorescence generated from the coated film onto which the ultraviolet light is radiated, and to obtain a two-dimensional (2D) image of the substrate; a processor configured to derive one region among a plurality of regions of the substrate based on the 2D image; a second light source configured to radiate a laser light onto the one region; and a second light detector configured to obtain optical interference data generated from the one region by the laser light, wherein the processor is configured to derive a thickness of the coated film of the one region based on the optical interference data.