Moderní experimentální metody Elektronová spektroskopie a mikroskopie IV Elektronová mikroskopie ● Transmisní ● Rastrovací ● Běžné přidružené analytické metody ● EDS, WDS ● EELS ● Elektronová difrakce ● EBSD ● LEED ● RHEED Scanning probe microscope © 2013 FEI Basic Microscope Classifications Charged particle microscopeOptical (light) microscope Optical (light) microscope objective lens light beam specimen light source Scanning probe microscope laser diode X, Y piezoelectric scanner Z piezoelectric scanner cantilever sample (stationary) mirror multiple segmentphotodiode (position sensitive detector) Charged particle microscope objective aperture selected area aperture condenser aperture electron source first condenser lens second condenser lens fluorescent screen microcondenser lens specimen (thin) objective imaging lens objective condenser lens diffraction lens intermediate lens first projector lens second projector lens projector chamber (Illustration of a TEM shown) © 2013 FEI Comparing Microscopes LIGHT MICROSCOPE ELECTRON MICROSCOPE Use of vacuum No vacuum Entire electron path from gun to camera must be under vacuum The source of illumination The ambient light source is light for the microscope Electrons are used to “see” – light is replaced by an electron gun built into the column The lens type Glass lenses Electromagnetic lenses Magnification method Magnification is changed by moving the lens Focal length is charged by changing the current through the lens coil Viewing the sample Eyepiece (ocular) Fluorescent screen or digital camera © 2013 FEI CORE TECHNOLOGY: The Electron Gun • Three main sources of electrons: • Tungsten • LaB6 (lanthanum hexaboride) • Field Emission Gun (FEG) • Different costs and benefits of each • Each selected primarily for their brightness © 2013 FEI CORE TECHNOLOGY: Electromagnetic Lenses electron beam soft iron pole piece electrical coil © 2013 FEI What is a Transmission Electron Microscope? projector lens electron source condenser system specimen (thin) objective lens Electron microscopy Electron microscopy © 2013 FEI TEM Aberration Correction • Chromatic aberration is distortion that occurs when there is a failure of a lens to focus all colors (wavelengths) to the same convergence point. • Correcting the aberration is necessary, otherwise the resulting image would be blurry and delocalized, a form of aberration where periodic structures appear to extend beyond their physical boundaries. • Recent improvements in aberration correction have resulted in significantly-improved image quality and sample information. • Spherical aberration occurs when parallel light rays that pass through the central region of the lens focus farther away than the light rays that pass through the edges of the lens. • Result is multiple focal points and a blurred image. Chromatic AberrationSpherical Aberration © 2013 FEI What is Scanning Transmission Electron Microscopy? STEM image of a 32nm semiconductor device Elemental map of a 45 nm PMOS transistor structure EDX map of semiconductor device © 2013 FEI What is a Scanning Electron Microscope? vacuum electron beam impact area electron source © 2013 FEI Comparing SEM and TEM TEM SEM Imaging Electrons must pass through and be transmitted by the specimen Information needed is collected near the surface of the specimen Electron Beam Broad, static beams Beam focused to fine point; sample is scanned line by line Voltages Needed TEM voltage ranges from 60-300,000 volts Accelerating voltage much lower; not necessary to penetrate the specimen Image Rendering Transmitted electrons are collectively focused by the objective lens and magnified to create a real image Beam is scanned along the surface of the sample to build up the image Interaction of the beam electrons Specimen must be very thin Wide range of specimens allowed; simplifies sample preparation Electron microscopy Electron microscopy Electron microscopy Sekundární elektrony – topografický kontrast Zpětně odražené – chElectron microscopyický kontrast Electron microscopy Electron microscopy WDS: better energy resolution better precission longer time Electron microscopy Electron microscopy FEI V400ACE Focused Ion Beam © 2013 FEI What is a Focused Ion Beam? (FIB) Cross-section of a semiconductor wafer imaged with a plasma FIB Physical Failure Analysis Platinum Nano-Wire FIB-cut in steel v2a EE by 1nA to 1B milling-002 steel EELS Electron microscopy EELS EELS EELS EELS EELS EELS EBSD EBSD EBSD EBSD Electron diffraction Electron diffraction Electron diffraction Electron diffraction Electron diffraction Electron diffraction Electron diffraction Electron diffraction Electron diffraction Electron diffraction Electron diffraction Electron diffraction Electron diffraction