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Nanofabrication and Soft Lithography

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					                                  Nanofabrication
                                and Soft Lithography
                                       Junior Research Seminar
                                              Spring 2004

                                                       20 April 2004




Junior Research Seminar: Nanoscale Patterning and Systems
Teri W. Odom
                              Goals of Nanofabrication
          •    Goals
                 – Parallel processing of components over
                   large areas
                 – Fabrication of structures    10 nm
                 – Cost effectiveness
          •    Function
                 – Nanoprocessors
                 – Sub-wavelength optics
                 – Biological assays
                                                                      ?
          •    Issues
                 – Material properties
                        • ultra-small grains
                        • amorphous materials
                 – Multilayer structures
                        • registration                      x 1/100
                        • alignment

Junior Research Seminar: Nanoscale Patterning and Systems
Teri W. Odom
                Making Nanostructures (< 100 nm)
            Pattern                   Electron beam, scanning probe, edge lithography



                                                            Replicate
            Master



            Replica                                                       Pattern
                                                                          transfer




            Multi-level Device
Junior Research Seminar: Nanoscale Patterning and Systems
Teri W. Odom
                          Nanofabrication Techniques


                 Scanning probe lithography


                                             Conventional lithography


                                                            Soft lithography




Junior Research Seminar: Nanoscale Patterning and Systems
Teri W. Odom
               Scanning Probe Lithography (AFM)
              Mechanical scratching                                                      Chemical modification



                                                      Molecular writing




                                    50 nm

             Electrostatic writing                                                           Magnetic writing




                       C. Lieber (Harvard), Science 257, 375 (1992); H. Dai (Stanford), APL 11, 1508 (1998)
                       C.F. Quate (Stanford), J. of App. Phys. 70, 2725 (1991); www.nanoscience.de/group_r/mfm

Junior Research Seminar: Nanoscale Patterning and Systems
Teri W. Odom
               Scanning Probe Lithography (STM)




Junior Research Seminar: Nanoscale Patterning and Systems
Teri W. Odom
                          Nanofabrication Techniques


                 Scanning probe lithography


                                             Conventional lithography


                                                            Soft lithography




Junior Research Seminar: Nanoscale Patterning and Systems
Teri W. Odom
                            Photolithography roadmap




                                                            W. Wakamiya (Selete)

Junior Research Seminar: Nanoscale Patterning and Systems
Teri W. Odom
                        Planar Fabrication Processes
                                                       LITHOGRAPHY
                                                            Expose




                                                 PATTERN TRANSFER

                   Etch                          Grow                Dope   Lift-off




Junior Research Seminar: Nanoscale Patterning and Systems
Teri W. Odom
                 Process Flow in Photolithography




Junior Research Seminar: Nanoscale Patterning and Systems
Teri W. Odom
                       Positive and Negative Resists




      •    Positive resists                                 •   Negative resists
             – Novolac/diazide photoresists                      – Poly chloromethylstyrene
                                                                 – AZ 5206 (Clariant)
             – PMMA
                                                                 – SU-8 (Microchem)
      •    Advantages
                                                            •   Advantages
             –   High resolution (300 nm)                        – More sensitive
             –   Aqueous based solvents                          – Better chemical resistance
             –   Ease of processing                              – Less expensive
             –   No swelling upon development               •   Disadvantages
      •    Disadvantages                                         – Less resolution (1 µm)
             – Less sensitive                                    – Organic based solvents


Junior Research Seminar: Nanoscale Patterning and Systems
Teri W. Odom
                                Evaporation and Lift-off




                                                            T. Odom et al. Langmuir, 18, 5314 (2002)

Junior Research Seminar: Nanoscale Patterning and Systems
Teri W. Odom
                           Electron Beam Lithography




                                                            Paul Scherrer Inst




                                                                       L. Sohn (Princeton)



Junior Research Seminar: Nanoscale Patterning and Systems
Teri W. Odom
                                Focused Ion Beam (FIB)




                                            www.fibics.com




Junior Research Seminar: Nanoscale Patterning and Systems
Teri W. Odom
                             Nano-Imprint Lithography
                                                               mask




                                                            patterned resist




                                                                       S. Chou (Princeton)   Nanonex

Junior Research Seminar: Nanoscale Patterning and Systems
Teri W. Odom
                    Laser-assisted Direct Imprinting




                                                            S. Chou (Princeton), Nature 417, 835 (2002)

Junior Research Seminar: Nanoscale Patterning and Systems
Teri W. Odom
                               Nanosphere Lithography
                                                            Colloidal crystal mask




                                                              Ag Nanoparticles




   R. P. van Duyne (Northwestern)

Junior Research Seminar: Nanoscale Patterning and Systems
Teri W. Odom
                          Nanofabrication Techniques


                 Scanning probe lithography


                                             Conventional lithography


                                                            Soft lithography



Junior Research Seminar: Nanoscale Patterning and Systems
Teri W. Odom
                        Soft Lithographic Techniques
                                                 Microcontact printing   Micromolding in capillaries
                                                        (µCP)                     (MIMIC)




                                                 Microtransfer molding    Near field lithography
                                                         (µTM)




Junior Research Seminar: Nanoscale Patterning and Systems
Teri W. Odom
                                Micromolding Techniques




  G.M. Whitesides, Angewandte Chemie 37, 550-575 (1998)


Junior Research Seminar: Nanoscale Patterning and Systems
Teri W. Odom
                                  Replica Molding (REM)



                                                            12 nm




                                                            8 nm




Junior Research Seminar: Nanoscale Patterning and Systems
Teri W. Odom
                          Microtransfer Molding (µTM)




                                                            G.M. Whitesides, Angewandte Chemie 37, 550-575 (1998)



Junior Research Seminar: Nanoscale Patterning and Systems
Teri W. Odom
               Micromolding in Capillaries (MIMIC)




                                                            G.M. Whitesides, Angewandte Chemie 37, 550-575 (1998)


Junior Research Seminar: Nanoscale Patterning and Systems
Teri W. Odom
                         MIMIC of Systems in Solvent




                                                            G.M. Whitesides, Angewandte Chemie 37, 550-575 (1998)

Junior Research Seminar: Nanoscale Patterning and Systems
Teri W. Odom
        Solvent Assisted Micromolding (SAMIM)
         •     PDMS mold is wet with a solvent that swells the polymer
         •     Solvent dissolves a thin layer of polymer
         •     Polymer/solvent conforms to mold pattern
         •     Solvent evaporates and pattern solidifies
                                     SAMIM; wet mold with
                                     solvent, place on photoresist




                                                                   Allow solvent to evaporate,
                 photoresist
                                                                   remove mold
                                solvent



                                                        embossed
                                                         pattern
                                                                                Whitesides, G.M. 1998, Appl. Phys. Lett. 73, 2893


Junior Research Seminar: Nanoscale Patterning and Systems
Teri W. Odom
        Summary of Nanolithography Strategies
              •    Photons
                    – UV, DUV, EUV, x-rays
                    – Diffraction, depth of focus
              •    Particles
                    – Electrons and ions
                    – Writing is serial, writing area is small
              •    Physical contact
                    – Printing, molding, embossing
                    – Adhesion of mold and replica, pattern transfer element
              •    Edge-based technologies
                    – Near field phase shifting lithography, topographic methods
                    – Diffraction
              •    Deposition
                    – Shadow evaporation
                    – Low flexibility in fabricating masks
              •    Self-assembly
                    – Surfactant systems, block copolymers
                    – Control over order, density of defects     G. Whitesides (Harvard), Chem. Rev. 99, 1823 (1999)


Junior Research Seminar: Nanoscale Patterning and Systems
Teri W. Odom

				
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