3D Nanoprinting of Advanced Nanoprobes for Correlative AFM-SEM Characterization

The demand for correlative microscopy continuously increases as it enables a superior ensemble of informationby using various methods to combine their individual strengths. The peak performance of this approach is thedirect correlation by means of hybrid microscopes, which enable the required characterization at the verysame spot in a consecutive or even parallel way. With that, however, comes the demand for fully integrated,conflict-free combinations of different microscopy techniques. A major step in that direction is a recentlyintroduced dual system called FUSIONScope™, which represents a deeply integrated solution of scanningelectron microscopy (SEM) and atomic force microscopy (AFM). While the former enables an ideal guidancetowards the area of interest by using different detectors, the latter complements SEM capabilities by truequantitative 3D surface information with spatial nanometer resolution, which together exploit their fullpotential by a shared coordinate system and the possibility to land the AFM tip on highly exposed regions.Even more importantly, joint characterization capabilities are strongly enhanced by advanced AFM modes (seeFigure 1a), such as conductive AFM (CAFM), magnetic force microscopy (MFM), electrostatic / Kelvin forcemicroscopy (EFM / KFM), scanning thermal microscopy (SThM) or mechanical mapping, which providesfunctional information beyond SEM capabilities. For that, special AFM nano-probes are required, which typicallyachieve their intended functionality via additional thin film coatings. The latter, however, has two maindisadvantages. First, additional coatings increase the tip apex and therefore limit the resolution ofmeasurements, which is in conflict with the still decreasing feature sizes of nanoscale systems. Secondly, withcoating comes the risk of delamination during measurements, which affects resolution, the lateral correlationand the general and / or timely reliability. Therefore, to exploit the full potential of advanced AFM modes forreliable correlated microscopy with highest resolution, it is of great interest to develop new approaches for thefabrication of functional nano-probes. Following that motivation, we joined forces with industry and apply theadditive direct-write technology focused electron beam induced deposition (FEBID) for the development ofnovel 3D nano-probe concepts with industrial relevance. In this presentation, we briefly discuss the 3D nano-printing process [1] and then go through a variety of advanced, FEBID-based tip concepts for CAFM, EFM, andMFM. The joint element for all probes is the coating-free character, which eliminates the aforementioned risksduring operation. Additionally, the apex regions are routinely in the sub-10 nm regime, which allows for high-resolution imaging. Aside of comparisons to traditionally used nano-probes, which reveal the superiorperformance of FEBID-based nano-tips (see Figure 1b, c), we also present several correlated microscopyexamples to demonstrate the added value of the here presented nano-probe concepts. The contribution isrounded up by a view on currently ongoing research towards AFM-based mechanical characterization, KFM,SThM, which benefits from the unique advantages of FEBID-based nano-probes [2], [3], [4].