X-ray Diffraction Beam Blocker for Epitaxial Layer Relaxation
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Solution Overview
Problem
High-resolution X-ray diffractometry struggles to accurately measure features of epitaxial thin-film layers due to strong diffraction peaks from substrates masking weaker features, and existing methods lack sensitivity and precision in detecting layer relaxation and dopant concentrations.
Innovation Solution
The method involves directing a converging X-ray beam towards a sample with multiple crystalline layers, using a beam blocker to isolate and enhance the detection of weaker diffraction peaks and fringe patterns, and employing asymmetric diffraction modes to increase peak separation and accuracy, along with a beam limiter to reduce the X-ray spot dimension and improve measurement precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional XRD measurement is used, then the substrate diffraction peak is detected, but the weaker epitaxial layer features are masked and cannot be accurately measured
Solution Approach 1:
The patent extracts and removes the harmful substrate diffraction peak from the measurement spectrum by using a beam blocker positioned at the substrate peak angle, allowing the weaker epitaxial layer features to be detected without masking
Solution Approach 2:
The measurement process is segmented into two parts: first measuring the substrate peak to determine its angular position, then using a beam blocker to exclude that specific angular range during the actual epitaxial layer measurement, enabling selective detection of layer features
2Measurement precision
If a beam blocker is introduced to block substrate peaks, then measurement sensitivity improves, but device complexity increases
Solution Approach 1:
The beam blocker serves multiple functions: it blocks substrate diffraction peaks, defines the angular acceptance range of the detector, and can be adjusted to accommodate different measurement configurations, reducing the need for separate components
Solution Approach 2:
The beam blocker acts as an intermediary element between the X-ray source and detector, selectively controlling which angular ranges reach the detector without requiring complex electronic or mechanical systems
3Manufacturing precision
If the X-ray beam is focused to a small spot, then spatial resolution improves, but the measurement time increases
Solution Approach 1:
The patent employs dynamic scanning of the focused X-ray beam across the sample surface, allowing the beam to rapidly move between measurement points while maintaining focus, thereby reducing total measurement time compared to static measurements
Solution Approach 2:
The continuous scanning motion maintains the focused beam continuously engaged with different sample regions without interruption, eliminating the need to refocus or reposition between measurements and reducing overall measurement time
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 significantly enhances the sensitivity and accuracy of X-ray diffraction measurements, allowing for precise characterization of epitaxial layers, including dopant concentrations and relaxation, thereby improving the monitoring and production of semiconductor devices.
Implementation Method 1
X-ray diffractometry (XRD) is a well-known technique for studying the crystalline structure of matter. In XRD, a sample is irradiated by a monochromatic X-ray beam, and the locations and intensities of the diffraction peaks are measured.
Implementation Method 2
For a given wavelength λ and lattice plane spacing d, diffraction peaks will be observed when the X-ray beam is incident on a lattice plane at angles θ that satisfy the Bragg condition: nλ=2d sin θ
Data Source
AI summary
A method for analysis includes directing a converging beam of X-rays toward a surface of a sample having an epitaxial layer formed thereon, and sensing the X-rays that are diffracted from the sample while resolving the sensed X-rays as a function of angle so as to generate a diffraction spectrum including a diffraction peak and fringes due to the epitaxial layer. A characteristic of the fringes is analyzed in order to measure a relaxation of the epitaxial layer.