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.
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.
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.
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.