White-Light Interferometer Thin Film Thickness Profile Measurement
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Solution Overview
Problem
Conventional white-light interferometers face challenges in real-time measurement and external vibration resistance, struggle to simultaneously measure the thickness and profile of transparent thin films due to limitations in filtering range and resolution, and require time-consuming numerical analysis for obtaining thickness and profile information.
Innovation Solution
The method involves polarizing white light and separating it into horizontally and vertically polarized components, generating coherent light from reflections on the thin film's surfaces, and using interference patterns to extract phase information for thickness and profile measurement, employing techniques like Fast Fourier Transform and high-pass filtering to isolate and analyze frequency components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an AOTF is applied to a white-light interference system to separate thickness and profile information, then thickness and profile can be independently measured, but the system performs poorly with respect to real-time measurement and external vibrations
Solution Approach 1:
The patent extracts the AOTF component from the interferometer system and replaces it with a blocking plate mechanism. This separation allows the interferometer to operate independently without the AOTF's limitations, enabling real-time measurement and vibration resistance while maintaining the ability to measure both thickness and profile through the blocking plate's on/off states
Solution Approach 2:
The patent replaces the AOTF (acousto-optic tunable filter) with a mechanical blocking plate system. This substitution eliminates the AOTF's poor real-time performance and vibration sensitivity, using a simpler mechanical on/off blocking mechanism that is more robust and suitable for real-time measurements
2Measurement precision
If a blocking surface is turned on or off to independently measure thickness and profile, then separate measurement is achieved, but simultaneous measurement of both parameters becomes difficult
Solution Approach 1:
The patent enables continuous measurement of both thickness and profile by maintaining the interferometer in a ready state where the blocking plate can be rapidly switched between on and off positions. This allows sequential measurement of both parameters without significant time loss, as the system remains operational and ready for immediate measurement transitions
Solution Approach 2:
The patent employs a dynamic blocking plate mechanism that can rapidly switch between blocked and unblocked states, enabling the system to adaptively measure both thickness and profile parameters in a flexible, time-efficient manner without being constrained by fixed measurement modes
3Measurement precision
If numerical analysis using least square fitting is performed to obtain thickness and profile information, then measurement data is processed, but the time required for measurement greatly increases
Solution Approach 1:
The patent performs preliminary signal processing by capturing interference patterns and extracting basic parameters (such as optical path difference) before final thickness and profile calculations are completed. This preliminary action reduces the computational burden and time required for subsequent numerical 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
This approach enables simultaneous and efficient measurement of thin film thickness and profile in real-time, improving measurement accuracy and reducing the time required for data acquisition while being resistant to external vibrations.
Implementation Method 1
converting white light into light polarized in an arbitrary direction
Implementation Method 2
separating the polarized light into horizontally polarized light and vertically polarized light
Implementation Method 3
generating coherent light while the light incident on the measurement object is reflected from an upper surface and a lower surface of the thin film and reflected light beams interfere with each other
Implementation Method 4
separating the coherent light according to frequency and obtaining an interference pattern at each frequency
Data Source
AI summary
Disclosed herein is an apparatus and method for measuring the thickness and profile of a transparent thin film using a white-light interferometer. The apparatus and method separate coherent light according to frequency, obtain a first interference pattern at each frequency, separate composite coherent light according to frequency, and obtain a second interference pattern at each frequency. Further, the apparatus and method obtain a phase, generated by the thickness of the thin film, from the first interference pattern, and acquire only information about the thickness of the thin film. Further, the apparatus and method obtain a phase from the second interference pattern, and acquires information about the profile of the thin film, including information about the thickness of the thin film. Further, by using the thin film thickness information, information about the profile of the thin film is acquired from the thin film profile information including the thin film thickness information. Therefore, the present invention can process a measurement region with respect to a single point or single line through real-time measurement and a single measurement without requiring a separate driving device, and is resistant to external vibration.