Substrate Inspection Apparatus for Thin Coated Film Thickness Measurement
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Solution Overview
Problem
Existing substrate inspection methods, such as 2D fluorescent photography and optical coherence tomography (OCT), face challenges in accurately measuring the thickness of thin coated films and are prone to errors due to light saturation and the complexity of OCT systems, especially when the coated film is thin (about 30 µm) or when using reference mirrors and other elements.
Innovation Solution
A substrate inspection apparatus and method that uses a light source to radiate laser light onto a coated film, detecting optical interference between reflected and penetrating light to derive the film's thickness, without requiring a reference mirror, and adjusts the light source based on reflectivity to ensure accurate measurements, utilizing a processor to generate sectional images and determine thickness from boundary lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical coherence tomography (OCT) is used to inspect the thickness of the coated film, then the thickness measurement capability is improved, but light saturation occurs due to reflection by a reference mirror causing measurement errors
Solution Approach 1:
The patent removes the reference mirror from the OCT system, extracting the problematic component that causes light saturation. The system uses only the measurement light path that penetrates the coated film and scatters from the substrate, eliminating the interference between reference and measurement light that causes saturation errors.
Solution Approach 2:
The patent introduces a beam splitter as an intermediary element that separates the measurement light path from the reference light path. The beam splitter directs measurement light through the coated film to the substrate while blocking the reference light path, preventing light saturation at the detector.
2Measurement precision
If optical coherence tomography (OCT) is used to inspect the thickness of the coated film, then the thickness measurement capability is improved, but the system becomes complex with many elements such as reference mirror, window glass, beam splitter
Solution Approach 1:
The patent removes unnecessary components from the OCT system, specifically the reference mirror and window glass, retaining only the essential elements (light source, beam splitter, detector) needed for thickness measurement. This extraction simplifies the overall system structure while maintaining measurement capability.
Solution Approach 2:
The patent enables the coated film itself to serve as the reference by using its back surface (substrate interface) as the reflection point. This self-service approach eliminates the need for an external reference mirror, simplifying the system while maintaining the interferometric measurement principle.
3Ease of operation
If 2D fluorescent photographic inspection is used to inspect the coated film, then the inspection process is simple, but only qualitative inspection is performed and accurate thickness measurement is not achieved
Solution Approach 1:
The patent replaces the 2D photographic inspection system with an optical coherence tomography system that uses light interference principles. This substitution transitions from qualitative visual inspection to quantitative thickness measurement while maintaining operational simplicity through automated processing.
Solution Approach 2:
The patent transitions from 2D surface inspection to 3D cross-sectional imaging by utilizing the depth-resolved nature of OCT. The system generates sectional images showing the coated film thickness in the depth direction, adding the third dimension (depth) to the inspection capability.
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 accurate measurement of thin coated film thickness, reduces measurement errors by eliminating light saturation issues and simplifying the system, and allows for efficient thickness measurement of coated films without the need for complex OCT components.
Implementation Method 1
reference light, that is generated by the laser light being reflected from a surface of the coated film
Implementation Method 2
measurement light, that is generated by the laser light penetrating the coated film and being scattered
Implementation Method 3
optical interference data on an interference between reference light, that is generated by the laser light being reflected from a surface of the coated film, and measurement light, that is generated by the laser light penetrating the coated film and being scattered
Data Source
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AI summary
A substrate inspection apparatus is disclosed. The substrate inspection apparatus according to the present disclosure may include: a light source configured to radiate laser light onto a coated film that is spread on a region of a substrate; a light detector configured to obtain optical interference data on an interference between reference light, that is generated by the laser light being reflected from a surface of the coated film, and measurement light, that is generated by the laser light penetrating the coated film and being scattered; and a processor configured to derive a thickness of the coated film corresponding to the region, based on the optical interference data.