In-situ Monitoring of Electron Beam Induced Deposition by Ato

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					In-situ Monitoring of Electron Beam Induced Deposition by
Atomic Force Microscopy in a Scanning Electron Microscope

                                                                                                                                                                                                                                                                                                                                                                                                                                       Markwiesenstrasse 55
                                                                                                                                                                                                                                                                                                                                                                                                                                       72770 Reutlingen, Germany
                                                                                                                                                                        b                                                                                                                    a
 Sven Bauerdick, Claus Burkhardt, Ralf Rudorf, Wolfang Barth , Volker Bucher and Wilfried Nisch                                                                                                                                                                                                                                                                                                                                        Tel. +49 (0) 7121 5 15 30-841
                                                                                                                                                                                                                                                                                                                                                                                                                                       FAX +49 (0) 7121 5 15 30-62
                                                                                                                                                                                                                                                                                                                                                                                                                                       bauerdick@nmi.de

  Natural and Medical Science Institute, Reutlingen, Germany                                                                                                                                                                                                                                                                                                                                                                           www.nmi.de
 a
   Kleindiek Nanotechnik GmbH, Reutlingen, Germany
 b
   Nascatec GmbH, Kassel, Germany



 Introduction                                                                                                    Setup
 Scanning Electron Microscopes (SEM) are widely used for                                                         This tool is based on a LEO Gemini 1550 VP field emission SEM that
 analytics in the micro- and nanometer range. For further specific                                               is supplied with three micro manipulators (Kleindiek Nanomotor
 inspection an Atomic Force Microscope (AFM) is useful provided                                                  Micro Manipulator MM3A). We attached a piezo-resistive AFM
 that positioning of sample and tip can be obtained quickly. A new                                               cantilever (Nascatec Piezocantilever) to one manipulator, the                                                                                                                                                                                                                                              In-situ AFM
 type of AFM is proposed, whose compact and guidable setup                                                       others can guide a glass drain tube for precise local gas injection
 allows the tip to be positioned inside and under observation of a                                               or be used for any other purpose like wiring of parts of the sample.
 SEM. Thus information on lateral dimensions and material from                                                   It is useful to arrange the manipulators around the SEM lens to be
 the SEM inspection could be completed by precise topography                                                     independant of any stage movements. An external pattern                                                                                                                                                                                                                            A piezo-resistive cantilever with a high force constant of 100 N/m
 and friction measurements in-situ.                                                                              generator (Raith Elphy Quantum lithography tool) allows direct                                                                                                                                                                                                                     and a silicon tip is used for static AFM imaging in the constant
 Electron Beam Induced Deposition (EBID) of                                                                                                                                                                                                                                                                                                                                                         force mode. The scannning software (Kleindiek ScanControl) is
 tungstenhexacarbonyle has been carried out. Thus we are able                                                                                                                                                                                                                                                                                                                                       able to drive either a micro manipulator or a tube scanner, that is
 to investigate the application of various techniques to analytics,                                                                                                                                                                                                                                                                                                                                 integrated into the SEM stage.The tube scanner offers a
                                                                                                                                                                                                                                                                                                                                                                                                    maximum scan range of 6 µm. Due to its high force constant the
                                                                                                                                                                                                                                                                                                                                                                                                    AFM can also be applied to defined scratching [1].
               Electron Beam Induced
               Depositon

 Tungstenhexacarbonyle W(CO)6 shows a vapour pressure of 2 Torr
 @ 35 °C and serves as precursor for deposition of tungsten with
 carbon content (EDX). The external reservoir was heated to 35 °C
 but a dosing valve was used to keep the global chamber
                              -6         -5
 pressure in the range 6 10 to 3 10 mbar at a base pressure
              -6
                                                                                                                                                                                                                                                                                                                                                                                                    In-situ AFM above a sample for EBID (p-Si partially coated with 20nm
 below 2 10 mbar. Deposition has been performed at electron
                                                                                                                                                                                                                                                                                                                                                                                                    Pt) left: cantilever and holder after coarse positioning
 energies of 1keV to 30 keV, doses of 0.01 to 1.8 nC per spot and a
                                                                                                                                                                                                                                                                                                                                                                                                    right: micrograph taken while scanning the stage for AFM
 stepsize of 100 to 30 nm on p-type silicon.
                                  The glass drain tubes were 10 to
                                  50 µm in diameter and arranged
                                  to the point of deposition at a
                                  lateral distance of about 50 µm.                                                                                                                                                                                                                                                                                                                                                        In-situ Imaging


                                                                                           Conventional AFM image
                                                                                                                                                                                                                                           2800                                                                                                    12000
                                                                                                                                                                                                                                                                                                                       100nm step
                                                                                           for determination of the                                                                                                                                                                                                    30nm step
                                                                                                                                                                                                                                           2400
                                                                                                                                                                                                                                                                                                                                                               line deposition rate [nm/(nC/nm)]
                                                                                                                                                                                                     dot deposition rate [nm/(nC/dot)]




                                                                                                                                                                                                                                                                                                                                                   10000
                                                                                           deposition rate.
              Characterization by SEM and                                                                                                                                                                                                  2000
                                                                                                                                                                                                                                                                                                                                                   8000


              AFM analysis                                                                                                                                         142.18 nm
                                                                                                                                                                   71.09 nm
                                                                                                                                                                   0 nm
                                                                                                                                                                  6.01 µm
                                                                                                                                                                                                                                           1600
                                                                                                                                                                                                                                                                                                                                                   6000
                                                                                                                                                                                                                                           1200

                                                                                                                                                                                                                                                                                                                                                   4000
                                                                                           6.01 µm
                                                                                                                                                    3.01 µm                                                                                         800

                                                                                                             3.01 µm
                                                                                                                                                                                                                                                                                                                                                   2000
                                                                                                                                                                                                                                                    400
                                                                                                                                        0 µm
                                                                                                                                 0 µm




                                                                                                                                                                                                                                                        0                                                                                          0
                                                                                                                                                                                                                                                                    0            5      10           15         20         25           30
                                                                                                                                                                                                                                                                                               Uacc [kV]



                                                                                                                                                                                                                                                    6000
                                                                                                                                                                                                                                                                                                                               30nm step 3kV
                                                                                                                                                                                                                                                                                                                                         20kV
                                                                                                                                                                                                                line deposition rate [nm/(nC/nm)]




                                                                                                                                                                                                                                                    5000


                                                                                                                                                                                                                                                    4000


                                                                                                                                                                                                                                                    3000                                                                                                                                                                        Tungsten structures of 40 nm in height:
                                                                                                                                                                                                                                                                                                                                                                                                                                SEM micrograph (top left),
                                                                                                                                                                                                                                                    2000                                                                                                                                           Deposition rate at
                                                                                                                                                                                                                                                                                                                                                                                                                                conventional AFM image (top right)
                                                                                                                                                                                                                                                    1000
                                                                                                                                                                                                                                                                                                                                                                                                   different electron
                                                                                                                                                                                                                                                                                                                                                                                                                                and images obtained by in-situ AFM
                                                                                                                                                                                                                                                                                                                                                                                                   energies (top) and
                                                                                                                                                                                                                                                            0
                                                                                                                                                                                                                                                             0.00             0.01    0.02          0.03        0.04       0.05          0.06              0.07
                      -6                    -5
 EBID at pbase < 3 10 mbar, pEBID = 2 10                                                                                                                                                                                                                                                      line dose [nC/nm]

 mbar, WD = 12 mm and step = 100/ 50/
 30 nm                                                                       240                                                 100nm step 8000                                                                                             70
                                                                                                                                                                                                                                                                                                                         100nm step 3kV
                                                                                                                                                                                                                                                                                                                                   20kV
                                                                                                                                                                                                                                                                                                                                                       70
                                                                                                                                                                                                                                                                                                                                                                                                     Conclusions
 Top: deposition at electron energies of                                     220                                                 30nm step
                                                                                                                                                                                                                                                                                                                         30nm step 3kV
                                                                                                                                                                                                                                                                                                                                  20kV
                                                                                                                                                              7000
                                                                                                                                                                                                                                             60                                                                                                        60
 1.5, 3, 5, 10, 20 and 30 keV                                                200
                                                                             180                                                                              6000                                                                                                                                                                                                                                  A new tool is proposed that combines SEM and AFM analysis and
                                                                                                                                                                            linewidth [nm/(nC/nm)]




 Bottom: deposition at 3 keV and doses of
                                                     dotsize [nm/(nC/dot)]




                                                                                                                                                                                                                                             50                                                                                                        50
                                                                             160
                                                                                                                                                              5000                                                                                                                                                                                                                                  allows electron beam induced chemical reactions. EBID of
                                                                                                                                                                                                                                                                                                                                                            linewidth [nm]




 0.61, 0.25, 0.12, 0.06, 0.04 and 0.01 nC
                                                                                                                                                                                                     dotsize [nm]




                                                                             140                                                                                                                                                             40                                                                                                        40
                                                                             120                                                                              4000                                                                                                                                                                                                                                  tungsten was carried out and characterized relative to patternsize
                                                                                                                                                                                                                                             30                                                                                                        30
                                                                             100                                                                              3000                                                                                                                                                                                                                                  and deposition rate. The latter is comparable to or higher than
                                                                             80
  Dotsize (step=100 nm) and linewidth                                        60
                                                                                                                                                              2000                                                                           20                                                                                                        20
                                                                                                                                                                                                                                                                                                                                                                                                    results presented elsewhere [2] and the global chamber pressure
  (step=30 nm) of the obtained tungsten                                      40                                                                               1000                                                                           10                                                                                                        10
                                                                                                                                                                                                                                                                                                                                                                                                            -5            -6
                                                                                                                                                                                                                                                                                                                                                                                                    of 2 10 to even 6 10 mbar is much below typical setups [2,3].
                                                                             20
  structures at different electron energies (left)                                                                                                            0
                                                                                                                                                                                                                                                    0                                                                                                  0                                            Characterization of EBID calls for precise lateral and topography
                                                                                   0   5      10        15             20   25                 30
                                                                                                                                                                                                                                                            0.0         0.2     0.4   0.6     0.8         1.0   1.2      1.4      1.6        1.8
  and exposure doses (right).                                                                        Uacc [kV]                                                                                                                                                                                                                                                                                      measurements and thus shows the benefit of in-situ AFM
                                                                                                                                                                                                                                                                                            dose [nC/step]
                                                                                                                                                                                                                                                                                                                                                                                                    monitoring in a SEM.

 References                                                                                                            Links                                                                                                                                                                                                                                                                           Information
 [1] C. Burkhardt, S. Bauerdick, R. Rudorf, W. Nisch, V. Bucher, W. Barth,                                             http://www.uni-tuebingen.de                                                                                                                                                                                                                                                     NMI
 A. Ehrmann, T. Lutz, J. Rau, this proceedings                                                                         http://www.leo.de                                                                                                                                                                                                                                                               www.nmi.de
          .                    .
 [2] H.W.P Koops, R. Weiel, D.P Kern, T.H. Baum, JVST B6(1) (1988) 477-                                                Http://www.nanotechnik.com                                                                                                                                                                                                                                                      Sven Bauerdick
 481                                                                                                                   http://www.nascatec.com                                                                                                                                                                                                                                                         bauerdick@nmi.de
 [3] R.R. Kunz, T.M. Mayer, JVST B6(5) (1988) 1557-1564                                                                http://www.raith.de                                                                                                                                                                                                                                                             +49 (0) 7121 - 51530 841                   MNE, Lugano 2002