X-ray Reflectometry (XRR) is an analytical technique that measures the intensity of X-rays reflected off a flat surface or thin film at very shallow angles (typically < 0-5°). By analyzing how the reflected intensity changes with the incident angle, it provides highly precise, non-destructive information about:
Thickness: Of single layers or complex multilayer stacks.
Density & Roughness: Electron density (related to material density) and interfacial/surface roughness.
Interfacial Structure: Quality and sharpness of interfaces between layers.
Principle
Principle
Reflection Principle: X-ray reflectometry (XRR) measures the reflection of X-rays at material surfaces. Most X-rays reflect at shallow angles, with minimal penetration.
Critical Angle: Below a specific angle, all X-rays are totally reflected, which relates to the material's electron density.
Kiessig Fringes: Reflected X-rays create interference patterns, providing information about layer thickness and density.
Reflectivity Curve: The XRR data shows a curve based on the angle of incidence, revealing structural characteristics through oscillations related to thickness and electron density.
Principle
Test Procedure
Our XRR testing workflow typically includes:
Sample Preparation: Ensure the sample surface is clean and smooth. The sample should be flat and uniform to obtain accurate measurements.
In addition to providing the crystallization direction of the sample, XRR can also calculate the grain size, crystallinity, and can be used with a database to measure the composition ratio.
Yes. XRR is non-destructive and probes all interfaces (e.g., SiO₂/SiN on silicon).
Applicable industries
Applicable Material Types:
Metals: Thin films and multilayers of metals such as copper, aluminum, titanium, and their alloys.
Semiconductors: Silicon, germanium, and compound semiconductor thin films and structures.
Glass: Glass substrates and coatings for thickness, density, and interface analysis.
Ceamics: Ceramic thin films, coatings, and functional layers.
Polymers: Polymer films, coatings, composites, and functional layers for composition and depth profiling.
Industrial Application
Industries and Applications:
Aerospace sector: analyze thin film coatings on components for thickness, uniformity, and interface quality.
Electronic industry: characterize semiconductor thin films, multilayers, and interfaces for device fabrication and quality control.
Plastics industry: evaluate polymer film thickness, uniformity, and surface or interface properties.
Surface technology: assess the quality and structure of surface treatments, coatings, and multilayer systems.
Environmental monitoring: analyze thin film deposits, contaminants, or residues on various substrates.
Industrial Applications
Thin Film Thickness Measurement: Silicon Dioxide on Silicon
To precisely control the insulating properties of semiconductor devices, a silicon dioxide (SiO₂) layer is deposited on a silicon wafer. The target thickness is around 50 nm. XRR is used to measure the actual thickness, density, and interface roughness of the SiO₂ layer. The X-ray reflectivity curve is collected and fitted with a theoretical model, yielding a thickness of 48.7 nm, a density close to the bulk value, and a smooth interface. This ensures the film meets the process requirements for device fabrication.
In the production of high-reflectivity mirrors, alternating layers of metal (e.g., molybdenum) and dielectric (e.g., silicon) are deposited on a glass substrate. Each layer is designed to be a few nanometers thick. XRR is employed to analyze the total thickness, individual layer thicknesses, and interface quality. The reflectivity data reveals well-defined Kiessig fringes, indicating sharp interfaces and uniform layers. The fitting results confirm the intended multilayer structure, and any deviations can be quickly identified and corrected in the deposition process.
sample status: flat and smooth,
roughness: less than 5nm
size: 2x2cm
height: less than 1cm
Setup: Place the sample in the XRR instrument. Align the X-ray source and detector to the sample surface at a specific angle.
X-ray Generation: The X-ray source generates X-rays, which are directed towards the sample at varying angles.
Data Collection: As the angle of incidence changes, the instrument measures the intensity of the reflected X-rays. This is done over a range of angles, typically from below the critical angle to above it.
Data Analysis: The collected data is plotted as a reflectivity curve (reflectivity vs. angle). This curve is analyzed to extract information about the sample's thickness, density, and roughness using mathematical models.
Model Fitting: Fit the experimental data to theoretical models to determine the structural parameters of the sample.
Interpretation: Analyze the results to understand the sample's properties, such as layer thickness and electron density.
X-ray reflectometry (XRR) is a non-destructive technique that studies thin films, surfaces, and interfaces. It measures X-ray intensity at grazing incidence angles, providing detailed information on the surface and near-surface region. XRR characterizes thin film thickness, density, and roughness, as well as interfacial properties. It's applied in materials science, physics, chemistry, and biology to investigate various materials. XRR's high sensitivity and non-invasive nature make it ideal for understanding material properties at the nanoscale, optimizing deposition processes, and improving device performance.
