Scanning Electron Microscopy vs Focused Ion Beam Caitlyn Gardner Quang T Huynh Concepts and fundamentals of Scanning Electron Microscopes Diffraction limit of light Any atoms are small than half of a wavelength of light is too small to see with light microscope Electrons have much shorter wavelength than light Secondary electrons Scattered electrons X rays Auger electrons Specimen current Application of SEM Generate high resolution images in nano scales Texture Chemical composition Examine microfabric and crystallography orientation in materials SEM Components Electron source Gun Electron lenses Sample Stages Detectors for all signals of interest Display Data output devices Infrastructure requirements Power Supply Vacuum system Cooling system Vibration free floor Room free of ambient magnetic and electric field Structure of a SEM Figure Typical structure of scanning electron microscope 1 Radiolarian Magnification X 500 Figure 2 Radiolarian 6 Magnification X 2 000 Advantages High magnification from 10 to 500 000x By 2009 the world s highest SEM resolution is 0 4nm at 30kV Can be applied to wide range of applications in the study of solid materials Large depth of field Easy to operate with user friendly interfaces Highly portable Safe to operate Disadvantages Sample must be solid and small enough to fit in the chamber Vacuum Some light elements can not be detected by EDS detectors Many instruments cannot detect elements with atomic numbers less than 11 Low conductivity sample must have conductive coating to prevent damage from conventional SEMs Focused Ion Beam FIB Similar to SEM Energized Ga ions Applications Sputtering Ion Milling Imaging Circuit Edit Figure FIB system 4 Sputtering And Imaging Strengths Ability to cross section small High beam current sputtering Low beam current imaging targets Fast high resolution imaging with good grain contrast Very precise milling Good SEM sample prep Limitations Vacuum Imaging process may spoil subsequent analyses Residual Ga Ion beam damage lowered resolution Circuit Edit Strengths Modifications can be made to circuits Cut traces or add metal connections Navigation system Repair mistakes multiple possible Quicker easier cheaper than new set in fab lab Performance optimization Limitations Backside modifications are time consuming Smaller features more complex Dual Beam Combination of SEM and FIB systems Accurate ion milling or deposition of materials with high resolution imaging References 1 Digivick Delicate Online Available http www digitalsmicroscope com scanning electron microscope5 10 11 2011 2 EAG Focused Ion Beam FIB Online Available http www eaglabs com techniques analytical techniques fib php 10 8 2011 3 IBM Focused Ion Beam FIB Online Available http www almaden ibm com st scientific services materials analysis fib 10 8 2011 4 M Brucherseifer SEM FIB Online Available http www brucherseifer com html sem fib html 10 8 2011 5 Swapp S Scanning Electron Microscopy SEM Online Available http serc carleton edu research education geochemsheets technique s SEM html 10 9 2011 6 Museum of Science Online Available http www mos org sln SEM newradio html
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