Dimensional Metrology Using Scanning Probe Microscopy

Dimensional metrology using scanning probe microscopy (SPM) refers to the precise measurement of three‐dimensional features at the micro‐ and nanoscale by raster-scanning a sharp probe across a surface. Since its inception, atomic force microscopy (AFM) and related probe techniques have evolved from qualitative imaging tools into quantitative metrological instruments capable of sub-nanometre accuracy. Central to this evolution are advances in probe control, thermal-drift compensation, interferometric position sensing and tip-characterisation protocols. These developments enable traceable measurements of step heights, surface roughness, critical dimensions and three-dimensional form. The global significance of SPM metrology spans semiconductor manufacturing, precision optics, biomaterials and fundamental studies of materials properties, where reliable dimensional data underpin process control, calibration of reference artefacts and the realisation of SI units at the nanoscale.

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Recent studies have introduced an artificial intelligence-based controller for AFM that dynamically adjusts scan parameters to minimise control deviations while prioritising probe and sample safety. By training the AI on simulated scans, the new approach reduced root-mean-square control errors by a factor of four compared with conventional PID schemes and demonstrated robust asymmetric responses in complex measurement scenarios. In parallel, metrological AFM systems equipped with built-in interferometers have been improved by novel correction methods for high-order nonlinearity. Employing an auxiliary capacitive sensor or an external flat artefact, researchers have effectively suppressed third- and fourth-order interferometric errors, reducing step-height uncertainty to 0.3 nm (k = 2) and enhancing repeatability across multiple positions. A third strand of progress targets the accurate characterisation of AFM tip geometry. By scanning purpose-built line-width standards with precisely calibrated sidewall features, teams have reconstructed tip profiles to within 0.4 nm agreement across tip-characteriser combinations. This refinement of tip-shape knowledge has led to traceable corrections of measured sample profiles, achieving repeatability of 0.3 nm on nanofeatures and reproducibility of under 1 nm across probes. Together, these advances illustrate how intelligent control, refined error-correction and rigorous tip-characterisation converge to elevate SPM from a laboratory imaging tool to a global reference method for dimensional metrology.

Dimensional Metrology Using Scanning Probe Microscopy publication trend

The graph below shows the total number of articles in dimensional metrology using scanning probe microscopy across all publications each year (not limited to Nature Index journals).

Technical terms

Scanning probe microscopy: A family of techniques that maps surface topography and properties by mechanically scanning a fine probe across a specimen.

Atomic force microscope: A form of SPM in which a cantilever with a nanoscale tip senses forces from the sample surface to generate topographical images.

Tip wear: The progressive alteration of a probe’s geometry due to mechanical abrasion or fracture during scanning.

Interferometric nonlinearity: Measurement errors in position sensing arising from high-order distortions in optical interferometer signals.

Tip characteriser: A reference artefact with known dimensions used to reconstruct the geometry of an AFM probe.

Traceability: The ability to relate measurement results to national or international standards through an unbroken chain of calibrations.

References

1. A New Kind of Atomic Force Microscopy Scan Control Enabled by Artificial Intelligence: Concept for Achieving Tip and Sample Safety Through Asymmetric Control. Nanomanufacturing and Metrology (2024).
2. Correction of Interferometric High-Order Nonlinearity Error in Metrological Atomic Force Microscopy. Nanomanufacturing and Metrology (2022).
3. Accurate tip characterization in critical dimension atomic force microscopy. Measurement Science and Technology (2020).