Tanguy Terlier oral presentation (FN2-Tue1-1-4)
Correlative method for 3D chemical image using SPM and ToF-SIMS
Korea Institute of Science & Technologies, 5, Hwarang-ro 14-gil, Seongbuk-gu, 02792 Seoul, Korea, Republic of
Nowadays, an important issue in Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) is to perform three-dimensional chemical mapping of structured samples with a complex architecture, conserving as well high spatial resolution (lateral and in-depth) as high mass resolution. During the surface analysis, only a projection into 2D surface mapping is achieved which twist the topographic render after the in-depth analysis. Moreover, the use of ion beam sputtering, such as in dual beam ToF-SIMS analysis, induces preferential sputtering and damage accumulation due to the sputter beam. So, the surface roughness generated by the sputtering affects the depth profiling of ToF-SIMS. In consequence, the authentic 3D chemical distribution as a function of the depth is completely distorted or lost.
Alternative approaches to resolve the artifacts of 3D chemical images exist. Among these solutions, the use of Scanning Probe Microscopy (SPM), in combination with ToF-SIMS permits to correct the depth scale of the data and to reduce the artifacts due to the depth profiling . In addition to the data correction, correlative approach using SPM and ToF-SIMS offers the unique possibility to couple topography with 3D chemical information.
In this work, it is proposed to present a universal method for the data correction of 3D chemical information achieved by ToF-SIMS; Firstly, we have merged the 2D ToF-SIMS mapping with AFM topographic image for each data point. Using this way, we have been able to visualize the local effects of the ion beam bombardment according to the chemical composition of the area. Then thanks to the AFM data, we have used a sputtering mode, based on the sputter rate and roughness of each components, to correct the voxel positions of each ToF-SIMS slice which has permitted to obtain, on the one hand, the 3D chemical mapping of the samples and on the other hand, a most accurate depth profile. To improve the data correction, PCA treatments [2, 3] were applied, both of chemical mapping and in-depth data point, to identify the different phase of components into the analyzed volume.
To illustrate the new potentials of this methods, we have characterized two different samples, a 3D structured inorganic multilayer and a self-assembled block copolymer film. Correlative method for 3D chemical image can be applied for a large range of characterization techniques utilizing an ion sputter gun with the spectroscopic analysis in combination with SPM technique.
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