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XRR

What is XRR?

XRR (X-ray Reflectivity) is a non-destructive X-ray technique used to characterize thin films and multilayers by measuring the intensity of X-rays reflected from a surface as a function of incident angle. By analyzing the reflectivity curve (including interference fringes), XRR can determine key film properties such as thickness, density (electron density), and interfacial/surface roughness.

XRR is widely used for semiconductor and optical coatings, barrier layers, dielectric films, metal films, and multilayer stacks, where accurate thickness and interface control are critical.

What XRR Can Help You Solve

  • Thin film thickness measurement (single layer and multilayer stacks)

  • Film density estimation (relative density/electron density trends vs spec)

  • Surface and interface roughness evaluation

  • Layer uniformity and process monitoring (batch comparison, tool drift)

  • Interface quality troubleshooting (roughness/intermixing indicators)

  • Comparative studies (before/after anneal, plasma treatment, cleaning, aging)

Typical Applications

  • Semiconductor thin films: oxides, nitrides, metals, diffusion barriers, dielectric stacks

  • Optical coatings: reflective/antireflective stacks (project-dependent)

  • ALD/CVD/PVD films: growth rate verification and density comparison

  • Protective coatings: barrier and passivation layers

  • Multilayer structures: interface roughness and layer thickness control

  • R&D and QC: rapid feedback for thin film process development

Capabilities & What You Receive

Measurement Outputs

  • Reflectivity curve (intensity vs angle or q)

  • Model fitting results to extract:

    • Film thickness (nm)

    • Film density / electron density (relative to reference/material model)

    • Surface/interfacial roughness (nm)

    • For multilayers: layer-by-layer thickness and interface parameters (project-dependent)

Deliverables

  • Reflectivity plots and fit overlays

  • Extracted parameter table (thickness, density, roughness)

  • Fit model description/assumptions (layer stack used)

  • Comparative conclusions across samples/conditions (optional)

Sample Requirements

  • Sample type: flat wafers or coupons with smooth surfaces

  • Surface condition: clean, dry, minimal particles (particles can distort reflectivity)

  • Area: sufficient uniform area for the X-ray beam footprint

  • Information to provide: film stack (materials/order), expected thickness range, deposition method (ALD/CVD/PVD), substrate type, and measurement goal (single layer vs multilayer)

Not ideal for: very rough surfaces, heavily textured films, thick/opaque multilayers where fringes are not resolvable (feasibility depends on sample).

Workflow

  1. Requirement review (layer structure, expected thickness, target outputs)

  2. Measurement setup (scan range, footprint control, alignment)

  3. XRR data acquisition

  4. Model fitting (single layer or multilayer; parameter extraction)

  5. Result verification (fit quality check, sensitivity review)

  6. Reporting (plots + fitted parameters + conclusions)

FAQs

Ellipsometry is excellent for optical constants and thickness but can be model-dependent and sensitive to optical assumptions. XRR provides strong sensitivity to density and interface roughness and can be highly accurate for thickness in many thin film systems. They are complementary.

Yes, but fitting complexity increases with more layers. Providing the layer sequence and approximate thickness helps achieve reliable results.

No—XRR is generally non-destructive and requires minimal sample preparation.

High roughness or heavy particle contamination reduces fringe visibility and can limit the accuracy of thickness/density/roughness extraction.

XRR works best for thin films where interference fringes are resolvable. Very thick films may reduce fringe visibility; feasibility depends on material contrast and measurement settings.

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