ISO 18516:2019

Overview

ISO 18516:2019 specifies standardized methods to determine lateral resolution and sharpness for beam‑based surface chemical analysis techniques - covering spatial ranges from nanometres to micrometres. It applies to scanning probes (finely focused beams scanned over a field of view) and full‑field imaging instruments (broad beam + imaging optics + pixelated detector). The standard supports measurement of features and layers with nanometre thickness and individual nano‑objects, helping users quantify imaging performance for AES, SIMS, XPS and similar techniques.

Key topics and technical requirements

• Scope and applicability: Beam‑based surface chemical analysis instruments; both scanning and full‑field imaging modes.
• Primary measurement methods:
  • Straight edge method (edge spread function, ESF) - for determining edge sharpness and related parameter D.
  • Narrow line (narrow stripe) method (line spread function, LSF) - for measuring imaged stripe width w and LSF characteristics.
  • Grating method - using periodic structures to estimate effective lateral resolution r by visual inspection or numerical line‑profile analysis.
• Instrument and sample handling: Requirements and recommendations for test samples, cleaning, mounting, instrument operation and data acquisition.
• Analytical outputs: Definitions of sharpness parameters, procedures to derive line/edge spread functions, and criteria for effective lateral resolution.
• Uncertainty and reporting: Guidance on reporting results, estimation of uncertainties and practical considerations (noise, sampling, signal‑to‑noise ratio). Annexes provide detailed uncertainty analysis and a practical SIMS example.
• Practical measurement elements: Consideration of scan direction dependence, plateau/length requirements for test features, and sampling density for gratings.

Practical applications and users

• Instrument manufacturers: Specifying, benchmarking and verifying imaging performance during design and QA.
• Analytical laboratories: Routine function checks, optimizing instrument settings for required lateral resolution, and documenting performance under Good Laboratory Practice (GLP).
• Accredited testing labs: Creating SOPs and measurement protocols to support accreditation (for example, ISO 17025) and consistent inter‑laboratory comparison.
• Researchers in nanotechnology and surface science: Quantifying spatial resolution when imaging nano‑scale chemical distributions.

Practical takeaway: choose the measurement method according to expected resolution (e.g., straight edge or narrow line for higher detail, gratings for graded/visual checks), follow sample preparation and data acquisition guidance, and use the reporting/uncertainty annexes to support traceable results.

Related standards and references

• ISO/TR 19319 (theoretical background referenced in ISO 18516)
• ISO 17025 (laboratory accreditation considerations)
• ISO/TC 201 (technical committee for surface chemical analysis)

Keywords: ISO 18516:2019, lateral resolution, sharpness, surface chemical analysis, AES, SIMS, XPS, beam‑based methods, straight edge method, narrow line method, grating method, nanometres to micrometres.