ISO 11952:2019

Overview - ISO 11952:2019 (SPM calibration)

ISO 11952:2019 provides a metrological framework for the calibration of scanning‑probe microscopes (SPMs) used to determine geometric quantities at the highest level of traceability. The standard is intended for calibration providers, national metrology institutes and specialist laboratories, not for routine industry-level checks. Its main goals are to increase comparability of SPM measurements by traceability to the unit of length, define minimum calibration and acceptance requirements, assess an instrument’s “calibrate‑ability”, and specify reporting and uncertainty evaluation methods.

Key topics and technical requirements

• Scope and objectives: Traceability, minimum calibration procedures, scope of calibration (measurement ranges, environments, temporal stability), and reporting.
• Metrological categories and preliminary characterization: Classification of SPMs into metrological categories (A, B, C), warm‑up/waiting times, drift and stability checks, and external influence assessment (thermal, acoustic, vibration).
• Calibration of scan axes: Procedures for calibrating x, y and z axes including lateral calibration (Cx, Cy), rectangularity (ϕxy), and vertical calibration (Cz); determination of deviations and nonlinearity.
• Measurement standards and handling: Requirements for flatness standards, step‑height standards and 3D artefacts; handling and selection guidance for measurement standards used in SPM calibration.
• Extended tests: Optional extended calibrations for scan speed, angle, eccentricity and 3D measurement standards to characterise more complex distortions.
• Uncertainty evaluation: A model consistent with ISO/IEC Guide 98‑3 (GUM) for calculating measurement uncertainty for simple geometric measurands; Annexes include lateral uncertainty treatments.
• Reporting requirements: What to include in calibration reports - equipment, ambient conditions, scan ranges, measurement standards and acceptance statements.

Practical applications and who uses it

• Calibration laboratories and national metrology institutes ensuring traceable SPM measurements.
• Instrument manufacturers and service providers performing high‑level calibrations or issuing traceable certificates.
• Research facilities and advanced nanometrology users requiring documented, high‑accuracy geometric measurements (pitch, step height, surface topography).
• Useful where measurement comparability, documented uncertainty and formal reporting are required for SPM‑based dimensional metrology.

Related standards

• ISO/IEC Guide 98‑3 (GUM) - uncertainty evaluation model referenced in the standard.
• ISO 5436‑1 - referenced in annex comparisons for step‑height determination.

Keywords: ISO 11952:2019, scanning‑probe microscopy, SPM calibration, scan axes calibration, geometric quantities, traceability, measurement uncertainty, metrology.