Overview
ISO 23131-2:2026 - Ellipsometry - Part 2: Bulk Material Model provides a standardized method for determining the optical and dielectric constants of materials using ellipsometric measurements analyzed with the bulk material model. This standard from ISO lays out clear procedures for using ellipsometry to ascertain key material constants, such as refractive index (n), extinction coefficient (k), and dielectric constants (ε1 and ε2), with a focus on direct, analytic determination when specific model assumptions are met. The document ensures consistency, reliability, and comparability of results across scientific and industrial applications.
Key Topics
- Ellipsometric Measurement Principles: Detailed procedure for measuring optical constants and interpreting ellipsometric data using polarized light reflection techniques.
- Bulk Material Model Assumptions:
- No surface films or layers (e.g., native oxides, moisture)
- Negligible surface roughness relative to measurement wavelength
- Substrate homogeneity (no lateral or vertical gradients)
- Known or absent anisotropy
- High chemical purity and a single-phase microstructure
- Sufficient substrate thickness to avoid backside reflections
- Planarity and consistent angle of incidence during measurement
- Model Validation: Guidance on validating the bulk material model through multi-angle incidence measurements and checking consistency in pseudo constants across spectral ranges.
- Measurement Uncertainty: Instructions for determining and reporting measurement uncertainty affecting ellipsometric transfer quantities (Ψ and Δ) and target constants (n, k, ε1, ε2).
- Reporting Requirements: Minimum data to include in ellipsometry test reports, such as reference to relevant ISO documents, details of model and parameters, calibration processes, model validity checks, and uncertainty estimates.
Applications
Ellipsometry employing the bulk material model is widely used in:
- Semiconductor Manufacturing: Non-destructive characterization of wafer substrates, detecting surface and interface qualities, and controlling material composition.
- Materials Science: Measurement of optical constants for dielectric, semiconductor, and metallic materials, quality control of reference materials like fused silica and silicon.
- Optical Coatings: Verification of underlying bulk material properties before or after coating application.
- Research and Development: Analysis of new materials' optical and dielectric behaviors in fields such as nanotechnology, photonics, and photovoltaics.
The bulk material model provides practical value by enabling rapid, analytic calculation of material constants without extensive fitting procedures, assuming model prerequisites are met. This approach ensures high precision and supports the traceability and reproducibility needed in regulated and quality-sensitive environments.
Related Standards
- ISO 23131 - Ellipsometry - Principles: Fundamental concepts and basic procedures for ellipsometric measurements.
- ISO/IEC Guide 98-3:2008 (GUM:1995) - Uncertainty of Measurement: Framework for expressing and calculating measurement uncertainty, referenced for uncertainty assessment in ellipsometry.
- ISO 23131-1: Ellipsometry - General Requirements (if available): Foundational requirements and definitions underpinning ISO 23131-2.
- IEC Electropedia & ISO Online Browsing Platform: Standardized terminology resources for optical measurement and material science.
Keywords: ellipsometry, bulk material model, ISO 23131-2, optical constants, dielectric constants, refractive index, extinction coefficient, measurement uncertainty, material characterization, surface analysis, semiconductor, thin films, metrology.
Conclusion: ISO 23131-2:2026 serves as a comprehensive guide for accurately determining optical and dielectric constants using ellipsometry, ensuring standardization and quality in research and industry settings where material properties are critical.