Novel Investigation Possibilities On FEBID Deposits By Combining Dual-Beam Capabilities With In-Situ High-Speed AFM 1
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R. Winkler , C. Yang , C. H. Schwalb , M. Winhold , U. Radeschnig , S. Michelitsch , 4 2 3,4 1,5 A. Deutschinger , G. E. Fantner , E. J. Fantner , H. Plank 1
Graz Centre for Electron Microscopy, Graz, Austria; 2Laboratory for Bio- and Nano-Instrumentation, EPFL, Lausanne, Switzerland; 3 4 5 SCL Sensor Tech. Fab. GmbH, Vienna, Austria; GETec Microscopy GmbH, Vienna, Austria; Institute for Electron Microscopy, Graz University of Technology, Graz, Austria
Introduction
Correlated Microscopy
Focused Electron Beam Induced Processing (FEBIP) has developed into a powerful tool to create structures down to the lower nanoscale. That automatically implicates the need of precise measurement methods. Atomic Force Microscopy (AFM) is usually applied for height characterization with spatial nanometer resolution. With this quantitative information concerning morphology, mechanical / electric / magnetic properties, new insights into FEBIP´s fundamental processes were gained in the past.1,2,3 However, for many experiments it would be beneficial, to integrate an AFM into the fabrication instrumentation. This not only improves the workflow but also enables new types of experiments to shed a light on open questions for FEBID as well as for other scientific areas.
sample cross section
Each microscopy technique provides individual strength: SEM:
co 3D ndu to ctiv po e gr m ap ap hy &
3D M phy E S gra F A po to TM
Ÿ Imaging (morphological / material
contrast) Ÿ spatial chemical information (EDX maps)
Instrumentation
The convenient combination of 3 microscopes (SEM, FIB and AFM) into 1 instrument is realized in the AFSEMTM- concept (GETec Microscopy) by the application of self-sensing cantilevers4. With that, dual beam functionalities are maintained despite the challenging space constraints inside the vacuum chamber. In this study we present 5 representative FEBID-experiments to demonstrate novel investigation possibilities with such a device.
conductive self-sensing cantilever
Ÿ quantitative height information Ÿ mechanical properties Ÿ electrical information (shown
SEM image of gold and aluminiumoxide traces on siliconoxide
here, see also SENTINEL poster) Ÿ thermal properties (see SENTINEL poster)
chemical composition analysis (EDX)
Combining these individual strengths the correlation of SEM/AFM data sets lead to new insights as the microscopes provide complementary information.
Local distribution Local distribution Local distribution of aluminiumoxide of siliconoxide of gold
Additive Tomography
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Subtractive Tomography
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M TM )
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Height/Phase/Amplitude and Conductive AFM (mechanical & thermal in progress). Ÿ The new Triple-S scanner is especially designed to provide high-quality & high-speed AFM capabilities and all Dual Beam microscope functionalities at the same time.
AFSEM m
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[1] R. Winkler et al. ACS Appl. Mater. Interfaces (2014, 2015) [2] R. Schmied et al. Beilstein J. Nanotechnol. (2015) [3] G. Arnold et al. ACS Appl. Mater. Interfaces (2014) [4] G.E. Fantner et al. Nanotechnology (2009) [5] F. Kolb et al. Nanotechnology (2013)
High Vacuum
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reversible irreversible
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AFM cantilever
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FIB-cut cantilever
The electrical measurements in the previous experiment (ambient gas conditions) reveal a dramatic change of conductivity on a very short time scale (shaded red) right after the fabrication process (post growth stabilization). To couple these data with morphological information high-speed AFM has been applied to access volume changes during the first period.
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Therefore, we synchronized e-beam patterning and AFM scan rates to fabricate multilayers of FEBID rectangles similar to the presented additive tomography. By that, first height information 25 seconds after deposition could be acquired. The subsequent height measurements after 12 seconds revealed a large height loss (~2 nm). After about 100 seconds the height stabilized to a constant value. This is qualitatively in good agreement with electrical measurements ... although different compared to the swelling experiments (chemistry?).
Phase image
References
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height (nm)
In this example we deconstruct a FEBIDmultilayer system (Pt-C 3D-pyramide covered with Au-C, SiOX, Pt-C, Au-C and Pt-C dots) in 100 nm cuts performed with Ga+-Ions. After each slice AFM and SEM images were acquired. The data of each cut are stacked together afterwards to a complete 3D reconstruction. Simultaneous AFM-phase imaging allows laterally a distinction of materials with different mechanical properties of each slice.
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AFM
Sample
To gain sub-surface information of a sample the milling capability of the Ion Focused Ion Beam can be used. In the past, layer-by-layer material bea m removal and SEM/EDX imaging was realized in the slice-and-view technique. Including AFM-functionality, additional information about heights, material (phase image) or conductivity can be gained. Especially electron-sensitive samples like polymers or TMSC can be reconstructed, substituting SEM imaging with AFM imaging.
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N 2+ O2+ H 2O
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Ÿ Implementation of several AFM-modes: Tapping/Contact,
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Simultaneous FEBID / AFM S GI
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Ÿ A tip-scanning
approach instead of a scanning stage system allows an easy integration into FIB/SEM. Ÿ High speed AFM scanning enables sub-minute image acquisition times.
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deposit in nitrogen ambient Ÿ An irreversible swelling under ambient air Ÿ The volume changes are in agreement with correlated electrical measurements Ÿ In principle these results can be explained by the compression & relaxation which entails variable grainto-grain distances and thus variations of the macroscopic current
Acknowledgements
1,30 1,25
voltage (V)
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and Triple-S by GETec Microscopy are Atomic Force Microscopes designed to operate in SEMs or Dual Beam Microscopes. Ÿ Due to the applied self-sensing technology (piezoresistive elements are incoporated in the cantilever) no space consuming optical detection systems are required.
Ÿ A reversible swelling of
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AFSEM and Triple-S
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These experiments reveal
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Deposition of a FEBID-pad from MeCpPtMe3 precursor AFM height imaging in-situ under vacuum conditions Introduction of nitrogen gas and acquisition of AFM image Evacuate chamber and AFM imaging under vacuum again Venting chamber and taking AFM image in ambient air Pumping chamber and acquire AFM height data under vacuum
1 µm
The in-situ growth tracking not only reveals vertical growth rates, but also exposes a base broadening in the first 100 nm, in agreement with literature2. 175
1. 2. 3. 4. 5. 6.
FEBID Sample
avaraged pad height (nm)
After each layer an in-situ AFM height image was acquired to control and adapt vertical growth rates.
TM ) EM FS (A AFM
Here we demonstrate an experiment in the following steps:
SEM image
Air
Sample
Vacuum
x 3 2 1
N2
S AFM
Here we deposit a miniature model of the Matterhorn from the MeCpPtIVMe3 precursor.
3D-AFM image
How a FEBID deposit changes its properties in different ambient gas conditions is an open but very important question. Electrical in-situ measurements in different environments suggest a variation of conductivity. The correlation of these electrical properties with volumetric changes on the lower nanoscale (swelling/compression) becomes possible with the AFSEMTM. Hence, one gets insights into the interaction of FEBID materials with different gas types.
Electron
GI
Precise deposition / etching / ion milling on the lower nanoscale is a very challenging task as numerous parameter (patterning parameter, pattern size, precursor material, substrate, ...) influence the final result 1 . Especially, for applications where defined nanometer-thin layers are of essential relevance (i.e. FEBID gas sensor5) or multi-layer systems the integrated AFSEMTM microscope provides (sub-)nm height information of the processed layers right after fabrication.
Ambient Gas Conditions
voltage (V)
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time (s)
Contact
We gratefully acknowledge Prof. Dr. Ferdinand Hofer, Jürgen Sattekow, Tobias Strunz, Franz Hofbauer, Vlado Stavrov and Nahid email: harald.plank@felmi-zfe.at Hosseini for supporting work. We also thank the FFG Austria (base project Nr. 830186), the European Union (EUROSTARS Project E! robert.winkler@felmi-zfe.at 8213 and 7th Framework Programme [FP7/2007-2013] under Grant Agreement no. 312483 (ESTEEM2)), and the COST funding (CM web: www.felmi-zfe.at 1301) for financial support. 3 µm