Structured thin film

SiO2 staircase on a Si substrate Height Measurements

The DHM® Reflectometry Analysis software enables to measure the height profile of transparent steps on a reflective substrate. A publication compares successfully DHM® and mechanical probe measurements.


  • Microscope: DHM® 2200
  • Objective: 20x
  • Software: Reflectometry Analysis Software
  • Sample
    • Substrate: Si
    • Steps material: SiO2
    • Nominal step heights: 375nm, 525nm, 975nm, 1200nm and 1275nm.


Each step’s thickness and material refractive indices are retrieved by Reflectometry analysis.

The precision of the DHM® Reflectometry analysis has been proven by comparative measurements with different methods (mechanical profilometer, AFM). Moreover the edges of the steps are better highlighted with DHM® optical acquisition while with a mechanical profilometer, the edges are rounded because of the radius of the scanning tip.

THe DHM® Reflectometry analysis method retains DHM® subnanometric resolution and large vertical measurement range capability and enables fast and complete 3D representation of the staircase.


Digital holographic reflectometry, T. Colomb, S. Krivec, H. Hutter, et al. Optics Express 18 (4), 3719–3731 (2010)

SiO2 Staircase on Si substrate
Measurement comparison between DHM® (red) and a mechanical profilometer

Si-SiO2-Au SIMS Crater Depth Measurements

A specific application is Secondary Ion Mass Spectrometry (SIMS). It consists of measuring the depth of a crater dug through multiple layers of transparent and non-transparent materials.  SIMS is a technique to analyze the composition of solid surfaces and thin films by sputtering the surface of the specimen with a focused primary ion beam and collecting and analyzing ejected secondary ions. The mass/charge ratios of these secondary ions are measured to determine the composition of the surface to a depth of 1 to 2 nm. Knowing SIMS crater depth with nanometric resolution is essential for characterization of chemical composition as a function of the depth.


  • Microscope: DHM® 2200
  • Objective: 20x
  • Software: Reflectometry analysis
  • Sample: Secondary Ion Mass Spectrometry (SIMS) target sample: crater dug through layers of Au-SiO2-Si
    • Au: thickness (40 +/- 10) nm
    • SiO2: thickness (100 +/- 20) nm


The accuracy of crater depth measurement with DHM® has been successfully compared with standard methods such as mechanical profilometer. The results show that the unique DHM® technology and non-contact method does not only provide an accurate depth measurement but also a fast complete 3D characterization without damaging the sample.
The crater structure is too large to be measured with AFM, which is generally limited to 100x100um area.


“Digital Holographic Reflectometry for Semi-Transparent Multilayers Measurement“, T. Colomb & al. 2012 International Symposium on Optomechatronic Technologies (ISOT 2012)

SIMS crater
Measurement comparison between DHM and a mechanical profilometer