Thin CoSi2 layers are formed by 195 keV Co ion implantation in Si(111) substrates to a dose of 2 × 1017 Co+/cm2 at room temperature (RT) followed by annealing in N2 atmosphere at different temperatures during 1 h are investigated. The characterizations of the as-implanted and annealed samples are performed using Rutherford backscattering spectrometry (RBS) and X-ray diffraction (XRD). Also the obtained samples have been characterized by means of Raman spectroscopy. The results show that the CoSi2 phase is polycrystalline with a random crystallographic orientation

Andreas, Kolitsch

Mohamed, Sidoumou

Rachid, Ayache

English

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International Journal of Thin Film Science and Technology Volume 4 Issue 3 Sep. 2015 Article 9 2015 Ion Beam Synthesis of Cobalt Silicide Layers in Si(111) Ayache Rachid Pharmacy Department, University of Batna, Batna, 05000, Algeria., ayache_r@yahoo.fr Sidoumou Mohamed Physics Department, Faculty of Sciences, University of Blida, Blida, 09000, BP 270, Algeria., ayache_r@yahoo.fr Kolitsch Andreas Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research, POB 510119, D-01314 Dresden, Germany, ayache_r@yahoo.fr Follow this and additional works at: https://digitalcommons.aaru.edu.jo/ijtfst Recommended Citation Rachid, Ayache; Mohamed, Sidoumou; and Andreas, Kolitsch (2015) "Ion Beam Synthesis of Cobalt Silicide Layers in Si(111)," International Journal of Thin Film Science and Technology: Vol. 4 : Iss. 3 , Article 9. Available at: https://digitalcommons.aaru.edu.jo/ijtfst/vol4/iss3/9 This Article is brought to you for free and open access by Arab Journals Platform. It has been accepted for inclusion in International Journal of Thin Film Science and Technology by an authorized editor. The journal is hosted on Digital Commons, an Elsevier platform. For more information, please contact rakan@aaru.edu.jo, marah@aaru.edu.jo, u.murad@aaru.edu.jo. *Corresponding author E-mail: ayache_r@yahoo.fr © 2015 NSP Natural Sciences Publishing Cor.   Int. J. Thin. Fil. Sci. Tec. 4, No. 3, 211-213 (2015) 211 International Journal of Thin Films Science and Technology  http://dx.doi.org/10.12785/ijtfst/040309  Ion Beam Synthesis of Cobalt Silicide Layers in Si(111) Ayache Rachid 1,*, Sidoumou Mohamed 2 and Kolitsch Andreas 3 1Pharmacy Department, University of Batna, Batna, 05000, Algeria. 2Physics Department, Faculty of Sciences, University of Blida, Blida, 09000, BP 270, Algeria. 3Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research, POB 510119, D-01314 Dresden, Germany. Received: 12 Jun. 2015, Revised: 22 Aug. 2015, Accepted: 23 Aug. 2015. Published online: 1 Sep. 2015.  Abstract:Thin CoSi2 layers are formed by 195 keV Co ion implantation in Si(111) substrates to a dose of  2 × 1017 Co+/cm2 at room temperature (RT) followed by annealing in N2  atmosphere at different temperatures during 1 h are investigated.  The characterizations of the as-implanted and annealed samples are performed using Rutherford backscattering spectrometry (RBS) and X-ray diffraction (XRD). Also the obtained samples have been characterized by means of Raman spectroscopy.   The results show that the CoSi2 phase is polycrystalline with a random crystallographic orientation. Keywords: Cobalt silicide; IBS; RBS; XRD.   1 Introduction The study of transition metal silicides has attracted a great deal of interest for   their applications as contact materials, gate electrodes, or interconnect materials in microelectronic devices [1-3]. CoSi2 is of CaF2 type structure, which is similar to that of Si. At room temperature, the lattice constant of CoSi2 is 1.2% smaller than that of Si [4–6]. The Co atoms can possibly be ‘‘added ’’ into the Si lattice to convert Si to CoSi2 structure with almost no volume change. Recently, silicide nanostructures have attracted increasing interest in nanoscale device applications. Thin  silicide  films  have  been  tailored  by  ion  bombardment of  layered  structures  as  well  as  by  physical  or  chemical  vapor co-deposition,  pulsed  laser  deposition,  and  other  thin  film  deposition  methods  [7–9]. In  this work,  we  shall  report  on  the  results  of  our  study  of  buried CoSi2,  layers  formed  in  silicon  by ion beam synthesis (IBS) with subsequent high-temperature annealing to remove the residual radiation damage and to redistribute the implanted species. 2  Experimental Details A buried cobalt silicide layer was produced by 195 keV Co+  ion implantation with a dose of   2x1017Co+/cm2at room temperature (RT) into a chemically cleaned p-type Si(111) wafer. The ion source is a DANPHYSIK high current implanter operated at 20-200 keV with magnetic scan and current limit less than 10 mA. When the implantation is completed, the samples are then annealed  in N2 atmosphere at different temperatures in the range of 600-1000 °C during 1h.  Rutherford backscattering spectrometry (RBS) was performed on the as-implanted and annealed samples with 1.7 MeV He+ ions at the scattering angle of 170° between the incoming and outgoing beam line. The experimental spectra were analyzed by SIMNRA computer program [12].  XRD measurements were performed in a θ-2θ geometry using  CuKα radiation. Furthermore, the obtained samples have been characterized by Raman spectroscopy. 3 Results and Discussion  Figure 1shows the random RBS spectrum of the annealed sample at 600°C during 1h implanted with high current density confirming the formation of the silicide, as the spectrum shows a clear step just behind the Si leading edge. The arrows  (labeled  Co  and  Si)  indicate  the  energy  for  backscattering  He+ ions  from  these  elements  at  the  surface. The  SIMNRA  simulation  of  RBS  spectrum  allows  the determination of  the  depth  profile  of  Co  and  Si  elements  (see  inset,   figure 1)  and the  confirmation of  the  formation  of  thin  CoSi2 buried  layer  (40x1015atms/cm2). The SIMNRA simulation of RBS spectrum indicates the existence of pure Si layer at the sample surface. Also the depth profiles of Si and Co elements (not shown) obtained by SIMNRA confirm the formation of buried CoSi2 layer (7x1015atms/cm2) during the ion implantation (for the as-implanted sample).  Figure 2 shows the RBS spectra of the as-implanted and annealed samples. It can be seen that by increasing the temperature treatment, the height of Co signal decreases 212                                                                                                                                           R. Ayache et al.: Ion beam synthesis…    © 2015 NSP Natural Sciences Publishing Cor.  whereas the energetic width increases, at the same time, the Si signal around, channel 520, corresponding to CoSi2 layer is extended.  Figure 1: Random RBS data for the annealed sample at 600°C during 1h. Inset Co and Si depth profile deduced from RBS spectrum. Also the heat treatment leads to the diffusion of oxygen from the surface to the interior of Si substrate. XRD was performed to investigate the formation of the Co silicide phases and Si crystal orientation.  Figure 2: RBS spectra for the as-implanted and annealed samples at different temperatures for 1h.            Figure 3 is a XRD spectrum showing Si peaks from Co-induced poly-Si films. Si peaks of    (1 1 1), (2 2 0), and    (3 1 1) were observed at 28.628, 47.68, and 56.388, respectively.  During annealing at different temperatures in the range of 600-1000 °C for 1 h, X-ray-diffraction measurements show diffraction peaks of the CoSi2 phase. From this, it can be concluded that ion implantation of such a high fluence at RT produces an amorphous layer of Si mixed with the implanted Co atoms. This layer does not recrystallize epitaxially but rather in a polycrystalline form with a more or less orientation of the crystals; the CoSi2 phase is polycrystalline with a crystallographic orientation determined by the random orientation of Si crystals. This is a heteroepitaxial Si film growth above the CoSi2 layer. This is due to a small lattice mismatch between Si and CoSi2 [13].  Figure 3: XRD patterns of the as-implanted and annealed samples for different annealing thermal.            Raman peaks of the cobalt silicide layer formation are shown in Figure 4 in the range of 200–600 cm−1.The first order Raman spectrum of crystalline Si is characterized by the presence of one peak corresponding to the only Raman active phonon that is allowed by the crystal symmetry. This peak has a Lorentzian shape, centered at a wavenumber of    520 cm-1 with a full width at half maximum (FWHM) of about 3 cm-1 at room temperature. As shown in Figure 4, two clear bands at 300 and 325 cm-1 can be observed. With the increase of temperature from 600 to 1000°C, the intensity of the band at 300 cm-1 gradually increases. The shift peak of Si at ∼468 cm−1 in the as-implanted sample related to the damage induced during the ion implantation of cobalt into a silicon substrate. Inset Figure 4 shows the variations of the Raman peak intensities of the band at 520 cm-1    of the as-implanted and annealed samples with varying temperatures. Upon  post-thermal  annealing,  the  damage  in   the  Si substrates  and  CoSi2,  films  decreases  gradually. A small Raman peaks at ∼325 cm−1 are attributed to the one-phonon LO vibration mode of CoSi2 is observed as well [14].  Figure 4: Raman scattering spectrum at RT for the as-implanted and annealed samples. Int. J. Thin. Fil. Sci. Tec. 4, No. 3, 211-213 (2015) / http://www.naturalspublishing.com/Journals.asp                                                213           © 2015 NSP          Natural Sciences Publishing Cor.  4 Conclusion  Implantation of 195 keV Co+ with a dose of 2x1017 at./cm2 in Si(1 1 1)  substrates at room temperature followed by annealing in an N2  atmosphere at different temperatures during 1 h allows the formation of a continuous buried CoSi2 layer. The CoSi2 phase is polycrystalline with a randomly crystallographic orientation. The Raman peak intensities of the band at 520 cm-1  increase after annealing by thermal reflection of the recrystallization of silicon substrate. Acknowledgments  We acknowledge the technical assistance   of the IBC team at Helmholtz-Zentrum. Special thanks go to Mrs. Scholz for the XRD measurements and Mrs. Lucchesi for her help with Raman spectroscopy. References [1] L.J. Chen and K.N. Tu,  Mater. Sci. Reports. 6 (1991) 53-140. [2] S.P.  Murarka, J.  Vac.Sci.Technol.  17(1980)  775-792. [3]Karen  Maex, Materials  Science  and  Engineering,Rll  (1993)  53-153 [4]O. P. Karpenko, S. M. Yalisove, J. Appl. Phys.80, 11 (1996) 6211-6218 [5] A. Vantomme, M.A.Nicolet, N. David Theodore, J. Appl. Phys. 75 (1994) 3882-3891. [6] P.A. Bennett, D.J. Smith, IK. Robinson, Applied Surface Science 180(2001) 65-72 [7] S.  Bocelli, G.  Guizzetti, F.  Marabelli,  G.  Thungstriom, C.S.  Petersson, Applied Surface  Science  91 (1995)  30- 33. [8] M.  Novakovic,  M.  Popovic,  K.  Zhang,  K.P.  Lieb,  N.  Bibic, Applied  Surface  Science  295 (2014) 158-163 [9]D. Smeets, J. Demeulemeester, D. Deduytsche, C. Detavernier, C. M. Comrie, C. C.Theron,C. Lavoie, A. Vantomme, J. Appl. Phys. 104 (2008) 103538 [10] A.H.  Reader,  A.H.  van  Ommen,  P.J.W.  Weijs,  R.A.M.  Wolters,  D.J.  Oostra,  Rep.  Prog.Phys.  56  (1993)  1397-1467. [11] A.  Vantomme,  M.F.  Wu,  U.  Wahl,  J.  De  Wachter,  S.  Degroote,  H.  Pattyn,  G.  Langouche,  H.  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Ion Beam Synthesis of Cobalt Silicide Layers in Si(111)

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Ion Beam Synthesis of Cobalt Silicide Layers in Si(111)

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