Micro-XRF Analysis for Thin-Substrate Layer Thickness
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
X-ray fluorescence analysis of thin layers on substrates faces interference issues due to overlapping spectral lines from layers on opposite surfaces, particularly when the substrate is thin and layers have common elemental composition, limiting the accuracy of thickness and composition measurements.
Innovation Solution
A method and system for X-ray Fluorescence (XRF) analysis that involves directing an X-ray beam onto a sample with initial and target measurements to produce reference and target spectra, reducing the contribution of initial layers to the target spectrum, and estimating parameters of second layers using iterative attenuation evaluation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If X-ray microfluorescence analysis is performed on thin substrates with layers on both surfaces, then the measurement can be performed on thin substrates, but the spectral lines from layers on the opposite surface overlap and reduce measurement accuracy
Solution Approach 1:
The patent segments the total XRF signal into distinct components: signal from the upper surface layers, signal from the lower surface layers, and substrate contribution. By mathematically separating these overlapping spectral components, the method isolates the signal of interest from the interfering opposite surface layers, thereby resolving the spectral line overlap problem and improving measurement accuracy.
Solution Approach 2:
The patent performs preliminary measurements and characterizations before the actual thickness and composition analysis. This includes measuring the XRF spectrum of the substrate alone, characterizing the lower surface layers' contribution, and establishing reference data. These preliminary actions enable the subsequent subtraction and isolation of the upper surface layers' signal, improving the accuracy of the final measurement.
2Use of energy by moving object
If the substrate is made thin to allow X-ray beam penetration, then the analysis can be performed, but the interference from the opposite surface increases
Solution Approach 1:
The patent extracts and removes the interfering signal components from the total measured spectrum. By taking out the substrate contribution and the lower surface layers' XRF signal through mathematical subtraction, the method isolates the upper surface layers' signal. This extraction process enables accurate measurement on thin substrates by eliminating the harmful interference that increases with substrate thinness.
3Adaptability or versatility
If layers with common elemental composition are present on both surfaces, then the substrate structure is symmetric, but the spectral lines overlap and reduce estimation accuracy
Solution Approach 1:
The patent introduces mathematical modeling and signal processing as intermediaries between the overlapping spectral signals and the final measurement results. By using computational methods to deconvolve the overlapping spectral lines and separate the contributions from identical layers on opposite surfaces, the method enables accurate parameter estimation even when the substrate structure is symmetric and spectral interference is present.
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
Improves the accuracy of estimating thickness and elemental composition of layers on one surface by reducing interference from layers on the opposite surface, enhancing the precision of layer deposition control in semiconductor manufacturing processes.
Implementation Method 1
X-ray fluorescence (XRF) measurement... X-ray fluorescence using sub-millimeter, focused excitation beams... X-ray source, which irradiates the sample, and an X-ray detector, for detecting the X-ray fluorescence emitted by the sample in response to the irradiation
Data Source
AI summary
A method for X-ray Fluorescence (XRF) analysis includes directing an X-ray beam onto a sample and measuring an XRF signal excited from the sample, in a reference measurement in which the sample includes one or more first layers formed on a substrate, and in a target measurement after one or more second layers are formed on the substrate in addition to the first layers, so as to produce a reference XRF spectrum and a target XRF spectrum, respectively. A contribution of the first layers to the target XRF spectrum is reduced using the reference XRF spectrum. A parameter of at least one of the second layers is estimated using the target XRF spectrum in which the contribution of the first layers has been reduced.