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Generation of vacancy-related defects during focused swift-ion beam implantation of silicon

Generation of vacancy-related defects during focused swift-ion beam implantation of silicon. I.Capan 1 , M.Jakšić 1 , Ž. Pastuović 1, 2 , Rainer Siegele 2 , David Cohen 2 1 Ruđer Bošković Institute, Zagreb, Croatia

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Generation of vacancy-related defects during focused swift-ion beam implantation of silicon

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  1. Generation of vacancy-related defects during focused swift-ion beam implantation of silicon I.Capan1, M.Jakšić1, Ž. Pastuović1,2, Rainer Siegele2, David Cohen2 1Ruđer Bošković Institute, Zagreb, Croatia 2 Centre for Accelerator Science, IER, ANSTO, 1 New Illawarra Rd, Lucas heights NSW 2234, Australia

  2. Introduction • Influence of high energies/high fluences of particles on silicon-based detectors; • Can heavier ions offer cost effective simulation of radiation damage produced in semiconductor detectors by p, n, e? • Ion beams  dense regions of vacancies and interstitials in bulk semiconductor  clustering; • Electrically active cluster-related damage in silicon: • Structure? • Capture kinetics? Silicon Detector Workshop

  3. Introduction • RD’s in n-type CZ Si V2(-/0) VO VO V2(=/-) ? VV Silicon Detector Workshop

  4. Introduction • Divacancy & ion mass effect Silicon Detector Workshop

  5. Introduction • Models for interpretation of the DLTS observed mass effect: (i) the lattice distortation and strain due to accumulated damage produced by heavy ions in the highly localized collision cascades can prevent, to a large extent, the electronic bond switching. The effect increases with ion mass because a density of elastic energy deposition, i.e. primary defect generation rate increases and causes larger distrortation and strain in the crystal lattice. Since the electronic bond switching is a thermally activated process, V2(=/-) peak is more influenced by the lattice strain than V2(-/0) peak (V2(=/-) defect has a low activation temperature of 115K ), PRB 55 (1997); Silicon Detector Workshop

  6. Introduction • Models for interpretation of the DLTS observed mass effect: (ii)suppression of the DLTS signal from shallow states is due to a local depletion of the carrier concentration in the dense defect cascade region which leads to incomplete occupation of the shallow states such as VO and V2(=/-) in heavy ion implanted n-Si, PRB 65 (2002); (iii) additional electrically active defects, e.g., vacancy-clusters (Vx, x>2) that artificially enhance the V2(-/0) signal, J. Appl. Phys. 93 (2003); Silicon Detector Workshop

  7. Experiment • The materials used in our experiment were phosphorus-doped Czohralski-grown (CZ) silicon wafers with initial resistivities of (1–2) cm. • The Au/n-Si Schottky diodes were formed by thermal evaporation of gold on etched Si surface • The samples (D=1mm) were uniformly irradiated at RT with scanning focused 8.3 MeV Si3+ ion micro-beam (I=5 fA @ F=4x1012 ions/cm-2s-1) up to dose of 1010 cm-2. • Deep traps were characterized with depth resolving deep level transient spectroscopy (DLTS). Silicon Detector Workshop

  8. Results  CV • Depth profile DLTS scan Averaged energy loss profiles of 8.3 MeV Si ions implanted in 100nm Au/n-Si Schottky diode (TRIM) w threshold for dense vacancy regime (PRB79) Silicon Detector Workshop

  9. Results  DLTS • Activation energy ? VO VV VP 0.17 0.23 X 0.42 0.45 Low-doped material! Is it a point-like defect? Silicon Detector Workshop

  10. Results  DLTS • Capture kinetics Point-like defect kinetics! PRB 79 075206 Silicon Detector Workshop

  11. Results • Defect depth profiling withDLTS ? VV X1 X2 Interstitial-rich region 0.42 0.53 0.78 Vacancy- rich region Two new deep defect states from interstitial-rich region emerge! Two DLTS spectra (@ -1 – -0.2 V & @-5 – -3 V) combined! Silicon Detector Workshop

  12. Results  Laplace DLTS • LDLTS measured at 225K, i.e. the activation energy of VV (-/0) ~0.4 eV for: • Vacancy-rich region (-2, -1 V) • Interstitial-rich region (-5, -2.8 V) Si : Si T=225K (Ec-0.4 eV) • LDLTS spectra from as implanted and annealed (180C 40min) sample measured at 225K for: • Vacancy-rich region (-2, -1 V) • Interstitial-rich region (-5, -2.8 V) Silicon Detector Workshop

  13. Conclusions • VO and V2(=/-) completely suppressed • 0.40 eV  vacancy-related defect • 0.40 eV  cluster-related defect • And the model is ... Silicon Detector Workshop

  14. TODO • Scanning capaictance microscopy (SCM) Silicon Detector Workshop

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