In Situ Atomic Force Microscopy Depth-Corrected Three-Dimensional Focused Ion Beam Based Time-of-Flight Secondary Ion Mass Spectroscopy: Spatial Resolution, Surface Roughness, Oxidation
Pillatsch L.; Kalácska, S.; Maeder, X.; Michler, J.
Microscopy and Microanalysis, 2021
This work from 2021 demonstrates improved automation of measurements compared to the 2012 report from the same group (https://doi.org/10.1155/2012/180437). These measurements were then used to study local sputtering rates in the sample.
FIB-SIMS, as performed by TOFWERK’s fibTOF, inherently performs three dimensional measurements by sputtering away the sample. However, for samples that do not have a homogenous composition and crystal structure, the conversion from the equivalent concepts of completed rasters (frames), total sputtering time or charge per unit area to a sputtered depth is fraught with difficulties. Furthermore, some materials – even having uniform composition and crystal orientation – will roughen or develop surface structures under the FIB beam.
The very small sputtered areas and shallow sputtered depth make the use of traditional depth profiling methods impossible. This issue can be addressed with use of an atomic force microscope (AFM) to measure the depth and then interpolate the true depth of each pixel for all of the raster images collected by the secondary ion mass spectrometer. For the best performance, it is necessary to use an AFM that is in situ within the FIB-SEM chamber to eliminate the time needed to remove the sample several times during a FIB-SIMS measurement for acquiring the AFM depths . In this work, the authors describe this approach using a fibTOF for the SIMS measurements and a prototype SEM compatible AFM.