Reflective Film Thickness Measurement via Deconvolution
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Solution Overview
Problem
Conventional thin film thickness measurement techniques face challenges with poor spectral and spatial resolution due to optical aberration, making it difficult to accurately measure film thickness uniformity over larger areas and monitor thickness in small regions, such as pixel sizes, in industries like flat panel displays.
Innovation Solution
A reflective microscopy film thickness measurement method that transforms broadband reflectance wavelength functions into frequency-domain functions, performs deconvolution operations to reduce spectral and spatial image spread, and uses curve fitting with Fresnel Equations to obtain accurate film thickness measurements, effectively addressing optical aberration issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional spectral reflectance measurement method is used, then film thickness can be obtained, but spectral resolution and spatial resolution are poor due to optical aberration
Solution Approach 1:
The patent applies deconvolution processing to remove the detrimental effects of optical aberration-induced spectral and spatial spread. By mathematically reversing the convolution effect caused by the optical system, the method recovers the original spectral and spatial information that would otherwise be lost, converting the harmful aberration effects into recoverable data through computational correction
Solution Approach 2:
The patent introduces a point spread function (PSF) as an intermediary mathematical model to characterize and correct the optical aberration effects. The PSF serves as a mediator that describes how the optical system transforms the original signal, enabling the deconvolution process to reverse this transformation and recover the true spectral and spatial characteristics of the thin film
2Measurement precision
If single point measuring method is used, then measurement can be performed, but measuring time increases when film thickness uniformity of entire sample is measured
Solution Approach 1:
The patent transitions from single-point measurement to area-wide simultaneous measurement by implementing spectral imaging that captures reflectance spectra across the entire sample field of view at once. This dimensional expansion from one-point to two-dimensional spatial measurement eliminates the need for mechanical scanning, dramatically reducing measurement time while maintaining the ability to assess film thickness uniformity across the entire sample
Solution Approach 2:
The patent creates a spectral image that serves as a comprehensive copy of the film thickness information across the entire sample area. By capturing and processing a full spectral image, the system obtains thickness data for all pixels simultaneously, replacing the time-consuming sequential single-point measurement approach with a parallel full-field measurement that provides complete spatial mapping of film properties
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
The method provides improved spectral and spatial resolution, enabling accurate and efficient measurement of thin film thickness across larger areas and small regions, enhancing measurement consistency and stability compared to existing technologies.
Implementation Method 1
the reflected light from the bottom of the film is refracted to the air, and interferes with the reflected light from the surface of the film
Implementation Method 2
the reflected light from the bottom of the film is refracted to the air
Implementation Method 3
The broadband reflectance wavelength function M(λ) is transformed to a broadband frequency-domain function M(f)
Implementation Method 4
The broadband frequency-domain function M(f) is divided by a single-wavelength frequency-domain function h(f), so as to obtain an ideal frequency-domain function S(f)
Implementation Method 5
a curve fitting is performed on the ideal reflectance wavelength function S(λ) and a reflectance wavelength thickness general expression, so as to obtain a thickness of the thin film
Data Source
AI summary
A reflective film thickness measurement method includes reading an original spectral image of a thin film measured by a broadband light source passing through a measurement system, transforming the original spectral image into a broadband reflectance wavelength function and then into a broadband frequency-domain function, dividing the broadband frequency-domain function by a single-wavelength frequency-domain function to obtain an ideal frequency-domain function, inverse-transforming the ideal frequency-domain function into an ideal reflectance wavelength function, and performing a curve fitting on the ideal reflectance wavelength function and a reflectance wavelength thickness general expression, so as to obtain a thickness of the thin film. A spectral image spatial axis direction processing method is performed to eliminate optical aberration in a deconvolution manner, so as to obtain spectral images of high spatial resolution.