Combining AFM with FIB/SEM in Nanofabrication

The ongoing trend towards miniaturization of components in electronics and other technologies isdriving the development of suitable fabrication- and analysis tools for nanoscale structures.Versatile tools in this context are dual beam microscopes that combine a Scanning ElectronMicroscope (SEM) with a Focused Ion Beam (FIB). These beams enable nanofabrication viasubtractive structuring (FIB milling, etching) and additive manufacturing (Focused Particle BeamInduced Deposition), as well as obtaining a variety of information about the sample (e.g. differentimaging modes, X-ray spectroscopy). In contrast, for complementary information such as thequantitative sample morphology in 3D, mechanical, electrical and magnetic surface properties,Atomic Force Microscopy (AFM) is often the method of choice. While usually both techniques aredone one after the other, for many questions it is advisable or even partly unavoidable to applyFIB/SEM and AFM in situ, in parallel or simultaneously. Therefore, integrating an AFM into aFIB/SEM chamber can provide new insights that are not accessible with stand-alone microscopes.In this contribution we first discuss the benefits of AFM measurements in vacuum compared toambient conditions. In a first use cases we present 3-dimensional reconstructions of samplevolumes where the physical properties (e.g. mechanical, magnetic, electrical) can be mapped foreach layer using advanced AFM modes and then correlated with information obtained byFIB/SEM. The individual layers can be produced either by FIB-slicing (subtractive tomography) orby layer-by-layer growth (additive tomography). Figure 1 shows subtractive tomography of polymerbeads in an aluminum matrix, where the stiffness in each FIB slice was measured by the AFM. Anexample of additive tomography is given in Figure 2, where the electron beam was used to depositsingle layers of material (FEBID), while the AFM monitored the layer-by-layer growth in situ [1]. Inother applications, the SEM can be used to select the region of interest and precisely position theAFM for mechanical testing of nanostructures. In addition, we present correlative characterizationof FIB cuts in a multilayer system combining FIB-SEM-EDX and AFM techniques. Again, we gobeyond simple AFM based height and phase imaging and use more advanced AFM modes(magnetic/electric force, conductive AFM) to obtain comprehensive information of the sample.However, such AFM modes require specialized nanoprobes, therefore, we briefly outline thefabrication route of such advanced AFM tips via 3D-nanoprinting. The selected examples alldemonstrate the advantages of correlative microscopy of a FIB-SEM dual beam microscope withan in situ AFM.