High lateral and depth resolution ion beam analysis of laterally confined nanostructures

Quantitative analysis of thin films and nanostructures is a cornerstone in the development of future nanoelectronic devices. Within standard Ion Beam Analysis,  a high energy ion beam impinges on the sample whereby the intensity of the scattered particles and their energy contains information about the elements, their concentration and their depth distribution. The evolution on novel detector systems (multidetectors , magnetic sector with strip detector), have provided new opportunities to characterize nano-electronic films. For complex (thin layer, 3D) systems, the reconstruction of a compositional depth profile from a single RBS spectrum is not unique but a solution can be found by combining spectra recorded under different geometries. In particular a multi-detector based system offers the opportunity to combine such a parametric variation within one experiment. Based on a proper understanding of the underlying physics (HR-RBS, ERD,) and the multidimensionality of the data set, one can resolve the uncertainties and parametrize the uncertainties with respect to the composition profile and build a framework (minimization process based on maximum entropy?) generating the most probable solution.

As 3D nanostructures become the elemental building block of advanced electronic devices, the goal will also be to realize ion-scattering based 3-dimensional composition tomography of a confined nanostructure. The tomography data are derived from a series of RBS spectra on multiple devices that are recorded under varying geometry (primary beam as well as detector positions) exploiting the use of a multi-element detector set-up extensively.  For the reconstruction, a reconstruction approaches will be developed based on a generalized 3D-representation of the sample, the scattering geometry in the RBS and methodologies from other tomography fields as well as neural networks.  Experimentally, your results will be compared to results on the same nanostructures obtained with atom probe microscopy and TEM tomography. Within this work the dimensionality of the system will evolve from 1D-confined volumes down to arrays of 3D-nanostructures. The complementarity of a high resolution detector versus a multidetector for these applications will be explored in terms of accuracy, precision, beam damage, lateral and in depth resolving power.