Electron Beam and X Ray Lithography Ankit Chaudhari Musa Ibrahim Electron Beam Lithography Application Electron beam Lithography EBL is used primarily for two purposes very high resolution lithography fabrication of masks by etching process It uses Serial Lithographic system Electron Beam Sources Thermionic Emitters Electrons released due to thermal energy Photo Emitters due to incident radiations photons Field Emitters due to applied current and quantum mechanical property of electrons Procedures of EBL Sample is coated with a thin layer of resist Polymethylmethacrylate PMMA PMMA breaks down into monomers upon exposure to electrons The exposed regions can be rinsed away developed using a chemical Methyl isobutyl ketone MIBK Advantages of EBL Print complex patterns directly on wafers Eliminates the diffraction problem High resolution up to 20 nm photolithography 50nm Flexible technique Disadvantages of EBL Slower than optical lithography Expensive and complicated Forward scattering Backscattering Secondary electrons Machine structure EBL Components Deflection coils and lenses to focus the electron Beam blanking turning the beam on and off Stigmators is a special type of lens used to compensate for imperfections in the construction and alignment of the EBL Colum Vacuum to isolate the electron beam from interferences X Ray Lithography Application X ray lithography is primarily used in nanolithography 15 nm optical resolution Utilizes short wavelength of 1 nm Simple Requires no lenses Allows for small feature size Procedures of X Ray Lithography PMMA is applied to the surface of silicon wafer PMMA hardens when contacted with x rays X ray mask is applied on top of silicon wafer before exposure Absorber Membrane Synchrotron radiation 0 2 2 nm Gap between substrate and mask Advantages of X Ray Lithography Short wavelength from X rays 0 4 4 nm No diffraction effect Simple to use No lens Faster than EBL Uniform refraction pattern High resolution for small feature size Disadvantages of X ray Lithography Thin lens Distortion in absorber Cannot be focused through lens Masks are expensive to produce X Ray Lithography Machine Structure Components Absorber reduce scattering of X rays Membrane allows X rays to travel through Vacuum to isolate the X ray from interferences QUESTIONS Works Cited B Braun Producing Integrated Circuits With X ray Lithography February 4 2004 Online Available http tc engr wisc edu uer uer97 author7 index html Accessed 9 18 2011 B Hans Georg Electron Beam Lithography September 22 2008 UER Main Online Available http www ipfdd de uploads media Lithohbmain 02 pdf Accessed 9 18 2011 C Friedrich X Ray Lithography March 1 2000 Online Available http www me mtu edu microweb chap1 ch1 4 2 htm Accessed 9 19 2011 Y Jiang Electron Beam and Conventional Lithography UER Main Online Available http www dssc ece cmu edu news seminars lunch05 headsmedia 041205 pdf Accessed 9 19 2011
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