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Physical Failure Analysis SEM-FIB-TEM-AFM Physical Failure Analysis SEM-FIB-TEM-AFM Michael Schmidt Apr 2018 EMAF Electron Microscopy and Analysis Facility 0.5 nm layer – 2 atoms thick Trace Analysis - 0.001 % (10ppm) inclusions 11 inclusions - each 300nm diameter - in 1600 µm2 field! 0.001 vol% / 10 ppm 1 : 100,000 Spot the black ball!? 20 nm Ti buried under 13,000 nm Cu 20nm 13μm Correlative Microscopy A single method of characterisation does not answer all analytical questions SEM FIB EDX STEM DF FIB-SEM Serial sectioning/3D reconstruction TEM SAED Complementary analysis techniques on the exact same sample location Cryo SEM for life science Impact • 4000+ analyses • Every group within Tyndall • 20+ industry partners • 40+ publications • 10+ NAP projects • 5 PhDs Contacts • [email protected] – Head of centre/group • [email protected] – SEM/FIB/EDX • [email protected] – TEM/FIB/HREDX • [email protected] – FIB/HRSEM/EDX Every nanometer matters in 3D patterning Scanning Electron Microscope - SEM Electron interaction with sample Comparing Microscopes LIGHT MICROSCOPE ELECTRON MICROSCOPE Electrons are used to “see” – The source of The ambient light source is light is replaced by an electron illumination light for the microscope gun built into the column The lens type Glass lenses Electromagnetic lenses Focal length is charged by Magnification Magnification is changed by changing the current through method moving the lens the lens coil Viewing the Fluorescent screen or Eyepiece (ocular) sample digital camera Entire electron path from Use of vacuum No vacuum gun to camera must be under vacuum How is Resolution Affected by Wavelength? 6 orders of magnitude improvement Visible light: wavelength 390-700 nm resolution: 0.2 μm = 200 nm Electrons: wavelength@200kV 0.003 nm theoretical resolution 0.0012 nm = 0.012 Å = 1.2 pm 2/3 speed of light grating laser layered sample Focused Ion Beam - FIB What is a Focused Ion Beam? (FIB) Platinum Nano-Wire Cross-section of a semiconductor wafer imaged with a plasma FIB Physical Failure Analysis What is a DualBeam™ System? False colouring for improved visualisation of grains in poly- crystalline material a) b) y = 0 c) y = 36 nm d) y = 72 nm e) y = 108 nm f) y = 144 nm g) y = 180 nm h) y = 216 nm i) y = 252 nm j) y = 288 nm k) y = 324 nm l) y = 360 nm 55 nm 200 nm Defected region only in low index (110) grains (321) Videos of 3D projections TEM cross section preparation TEM cross section preparation (Scanning) Transmission Electron Microscope – (S)TEM TEM Schematic STEM 2D layered material on sapphire 0.5 nm layer 2 atoms thick Sources of contrast Diffraction contrast - some grains diffract more strongly than others; defects may affect diffraction Mass-thickness contrast - absorption/ scattering. Thicker areas or materials with higher Z are dark Electron Diffraction Diffraction contrast image Bright field Dark field • Only main beam is used. Aperture in back focal plane blocks diffracted • Instead of main beams beam, use a diffracted beam • Image contrast mainly due to subtraction of • Move aperture to intensity from the main diffracted beam or tilt beam by diffraction incident beam Bright field imaging Dark field imaging Defect visualisation STEM modes Bright field imaging Dark field imaging Cs Corrected vs. uncorrected image Nano-analytical EDX: Compositional maps of a device Atomic Force Microscope - AFM Atomic Force Microscope • The cantilever is designed with a very low spring constant (easy to bend) so it is very sensitive to force. • The laser is focused to reflect off the cantilever and onto the sensor • The position of the beam in the sensor measures the deflection of the cantilever and in turn the force between the tip and the sample. How the AFM Works • The AFM brings a probe in close proximity to the surface • The force is detected by the deflection of a spring, usually a cantilever (diving board) van der Waals force curve • Forces between the probe tip and the sample are sensed to control the distance between the the tip and the sample. Two Modes Repulsive (contact) • At short probe-sample distances, the forces are repulsive Attractive Force (non-contact) • At large probe-sample distances, the forces are attractive The AFM cantelever can be used to measure both attractive force mode and repulsive forces. Raster the Tip: Generating an Image • The tip passes back and forth in a straight line across the sample (think old typewriter or CRT) Scanning Tip Scanning • In the typical imaging mode, the tip- sample force is held constant by adjusting the vertical position of the tip (feedback). • A topographic image is built up by the computer by recording the Raster Motion Raster vertical position as the tip is rastered across the sample. Scanning the Sample • Tip brought within nanometers of the sample (van der Waals) Radius of tip limits the accuracy of analysis/ resolution Other Types of SPM Techniques • Lateral Force Microscopy (LFM) • Frictional forces measured by twisting or “sideways” forces on cantilever. • Magnetic Force Microscopy (MFM) • Magnetic tip detects magnetic fields/measures magnetic properties of the sample. • Electrostatic Force Microscopy (EFM) • Electrically charged Pt tip detects electric fields/measures dielectric and electrostatic properties of the sample • Chemical Force Microscopy (CFM) • Chemically functionalized tip can interact with molecules on the surface – giving info on bond strengths, etc. • Near Field Scanning Optical Microscopy (NSOM) • Optical technique in which a very small aperture is scanned very close to sample • Probe is a quartz fiber pulled to a sharp point and coated with aluminum to give a sub-wavelength aperture (~100 nm) Magnetoelectric Switching of B6TFMO Thin Films Amplitude B = 0 mT Phase Magnetoelectric Switching of B6TFMO Thin Films Amplitude B = +250 mT Phase Moving single atoms with STM tip - Nanolithography https://www.youtube.com/watch?v=oSCX78-8-q0 Correlative microscopy A single method of characterisation does not answer all analytical questions FIB SEM EBSD AFM FIB-SEM Serial sectioning/3D reconstruction TEM SAED Complementary analysis techniques on the exact same sample location Tools available in EMAF, Tyndall Contacts • [email protected] – Head of centre/group • [email protected] – SEM/FIB/EDX • [email protected] – TEM/FIB/HREDX • [email protected] – FIB/HRSEM/EDX.
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