Implant redistribution in high-dose ion implanted and annealed silicon

Abstract

Diffusion constants of helium in gold, silver and aluminium are determined from thermal desorption experiments, giving:

Au: D ₀ = 10^?1.0 cm²/sec, ΔH = 1.70 eV

Ag: D ₀ = 10^?1.2 cm²/sec, ΔH = 1.50 eV

Al: D ₀ = 10^+0.1 cm²/sec, ΔH = 1.35 eV

The results are compared to self-diffusion and to the diffusion of other light elements in metals. Possible diffusion mechanisms are discussed.     

Impurity redistribution during laser irradiation in ion implanted silicon

(100) Silicon wafers implanted with 2 × 10^{15 31}P+/cm² at 100 keV have been annealed using a scanning beam of incoherent light. The main results obtained after annealing are: (a) the carrier concentration profile shows a complete dopant activation without diffusion of the implanted ions; (b) the values of carrier mobility are similar to those obtained by furnace annealing; (c) an improvement of minority carrier diffusion length is often observed; (d) a very good damage recovery is obtained. Transmission Electron Microscopy observations show that the residual damage is confined within a region at 0.2 μm depth and consists of dislocation loops of about 50 Å diameter. It is concluded that this technique can be used to obtain very good annealing of implanted layers.     

Raman scattering study of ion implanted and C.W.-Laser annealed polycrystalline silicon

Recovery of crystallinity in ion-implanted and c.w.-laser annealed polycrystalline silicon films has been examined by the Raman spectroscopy. The variation of the Raman frequency and width with laser annealing and thermal annealing shows the presence of uniform strain in the laser annealed polysilicon. It is found that the subsequent thermal annealing releases the strain.     

Morin transition in annealed iron implanted garnets

Y₃Fe₅O₁₂, Y₃Al₅O₁₂ and Gd₃Ga₅O₁₂ single crystal granets were implanted with 10¹⁷iron.cm⁻². Complementary techniques: CEMS, TEM and XRD at glancing angles have allowed to follow the behavior of implanted iron during thermal annealings. For Y₃Fe₅O₁₂ large α-Fe₂O₃ particles are formed after annealings and at 1200°C occurs a low temperature regime of the Morin transition at room temperature. For Y₃Al₅O₁₂, due to aluminium substitution in the precipitates, the Morin transition is only detected after an annealing at 1300°C whereas in Gd₃Ga₅O₁₂ no Morin transition is observed.     

YIG formation in annealed iron implanted YAG

YAG and YIG crystals implanted respectively with 100 keV⁵⁷Fe²⁺ ions (1 × 10¹⁷ ions.cm^?2) and 50 keV²⁷Al ions (1.1 × 10¹⁷ ions.cm^?2) have been studied by conversion electron Mössbauer spectroscopy (CEMS) directly after implantation and after annealings in air at temperatures up to 1100°C. In both as-implanted samples iron is found mainly in three states: Fe²⁺, Fe³⁺ and small metallic precipitates. Annealing behaviour is divided into two stages: (i) up to 400°C the iron has become completely oxidized and (ii) between 400 and 850°C the epitaxial regrowth of the implanted layer takes place. During this process a part of iron ions are incorporated into octahedral and tetrahedral sites, thus making a Y₃ (Al Fe)₅ O₁₂ compound. The remaining iron part precipitates in the form of Fe₂O₃ particles.     

Mössbauer spectroscopy of laser annealed tellurium implanted silicon (II).129I

Laser annealed^129mTc-implanted silicon has been investigated using¹²⁹I Mössbauer spectroscopy. At least three dopedependent charge states of substitutional iodine are found. For heavily doped p-type Si a single line component S₁, with isomer shift S=0.96(4) mm/s w. r. t. Cu¹²⁹I and an effective Debye temperature ?′=196(3) K is observed. This component is attributed to I⁺⁺. For compensated Si a single line component, S₂, assigned to I⁺, with S=2.39 (4) mm/s and ?′=170 (3) K is found. For n-type Si, a component S₃, characterized at 4.2 K by S=2.15 (4) mm/s and a quadrupole splitting eQV_zz/h=452 (8) MHz (n?0)is observed. At higher temperatures S₃ shows quadrupole relaxation and its recoilless fraction becomes strongly anisotropic. This behaviour is explained on the basis of a transition from a static to a dynamic Jahn-Teller distortion. Component S₃ has been attributed to I⁰. In the spectra of compensated and n-type Si a less well-defined component Q, with parameters resembling those of S₃ but showing no quadrupole relaxation, is observed. This component has tentatively also been assigned to I^o. The results can be understood qualitatively on the basis of a simple MO-model.     

Photoluminescence evolution in self-ion-implanted and annealed silicon

Si⁺ ion-implanted silicon wafers are annealed at different temperatures from room temperature to 950~℃ and then characterized by using the photoluminescence (PL) technique at different recorded temperatures (RETs). Plentiful optical features are observed and identified clearly in these PL curves. The PL spectra of these samples annealed in different temperature ranges are correspondingly dominated by different emission peaks. Several characteristic features, such as an R line, S bands, a W line, the phonon-assistant W^\rm TA and Si^\rm TO peaks, can be detected in the PL spectra of samples annealed at different temperatures. For the samples annealed at 800~\du, emission peaks from the dislocations bounded at the deep energy levels of the forbidden band, such as D_1 and D₂ bands, can be observed at a temperature as high as 280~K. These data strongly indicate that a severe transformation of defect structures could be manipulated by the annealing and recorded temperatures. The deactivation energies of the main optical features are extracted from the PL data at different temperatures.     

Bonding of fluorine-implanted and annealed silicon

The effects of low temperature annealing on crystalline silicon samples, made amorphous by the ion-implantation of fluorine ions, has been studied using infrared spectroscopy. The implantation process is shown to result in a metastable state which, upon subsequent thermal annealing, converts to the well-characterized stretching and bending modes found in deposited silicon-fluorine films. Using arguments based on molecular orbital theory and model calculations, the metastable state is identified as a silicon-fluorine-silicon bridge.     

Mössbauer spectroscopy of laser annealed tellurium implanted silicon (I).119Sn and125Te

Laser annealed Te-implanted silicon has been investigated using¹¹⁹Sn and¹²⁵Te Mössbauer spectroscopy. The¹¹⁹Sn Mössbauer spectra consist of a single lorentzian, known to be due to substitutional Sn atoms in Si, independent of the type of doping of the silicon. The results on¹²⁵Te revcal at least two different components. In heavily doped n-type Si a single line component is observed with an isomer shift of 0.15 (5) mm/s with respect to SnTe and an effective Debye temperature of 207 (3) K. Heavy p-doping leads to another single line component with an isomer shift of ?0.13 (5) mm/s and an effective Debye temperature of 232 (3) K. These components are ascribed to the neutral and doubly positive charge state of substitutional Te atoms, respectively.     

Impurity effects in amorphous germanium and silicon

A systematic study of the hoping conductivity of amorphous germanium-transition metal (Cr, Co, Fe) films reveals an exponential decrease of the hopping parameter, T_o, as a function of the transition metal concentration. A similar, but often unnoticed, behavior is found in the literature. A linear decrease in the energy gap as a function of concentration is postulated as an explanation.     

Impurity micropotentials in commercial silicon crystals

The use of very cold neutrons, of laser mass spectrometry, and of secondary-ion mass spectrometry has revealed the presence of microprecipitates in commercial Si crystals grown by the Czochralski method and by float zoning.Neutron-Physics Laboratory, Lebedev Physics Institute, Academy of Sciences of the USSR. Translated from Preprint No. 149 of the Lebedev Physics Institute, Academy of Sciences of the USSR, Moscow, 1988.     

Photoacoustic monitoring of damage in ion implanted and annealed si layers

The photoacoustic technique has been used to characterize ion implanted Si layers, as a function of the implantation conditions of ion dose and energy and of thermal annealing conditions, through the determination of the material thermal conductivity and optical absorption coefficient. It was found that the technique can discriminate between amorphous material obtained under different implantation conditions. Regarding the annealed samples, different results have been obtained for amorphous as-implanted, fine grain polycrystalline, highly defective single crystalline and defect-free single crystalline materials.     

Surface topography of laser annealed silicon

The topography of silicon has been studied by Nomarski and scanning electron microscopy and by light diffraction techniques. In addition to the previously known ripple structure with wavelength perpendicular to the laser E vector, two new ripple structures of other orientations have been found. The heights of the structures have been determined for the first time.     

Impurity pairs and excitation relaxation in doped silicon

The kinetics of photoconductivity is studied in silicon doped with B, Al, Ga, In, P, As, and Sb with concentrations of 10₁₆–10₁₈cm_?3 at 4.2 and 10.5 K placed in an 8-mm microwave electric field under pulsed impurity excitation. It is found that infrared absorption by impurity pairs and a slow component of photoresponse relaxation arise at close impurity concentrations. It is shown that this component is due to an increase in the polarization hopping conductivity in the presence of the optical charge exchange of impurity states—isolated impurities and impurity pairs and dipoles (pairs of the major and compensating impurities). The hopping transfer processes of ion charges in the course of relaxation are analyzed. It is shown that the main contribution to polarization photoconductivity comes from hopping transitions in impurity pairs at relatively small concentrations and from hopping with the participation of isolated ions at increased concentrations.     

Interstitial type defects in implanted silicon

Silicon layers implanted with boron, lithium, phosphorus, and silicon are investigated by x-ray measurements of the lattice constant. It is established that, as a result of ion implantation in silicon, stable interstitial complexes are generated in concentrations comparable to those of vacancy type defects. The interstitial complexes are annealed in stages, viz., I at 140, II at 500°C in the case of irradiation of silicon with light ions, and I at 180, II at 560°C in crystals irradiated with medium mass ions.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 76–80, July, 1984.The authors are grateful to V. D. Tkachev for useful discussion of the results.     

Raman scattering studies in phosphorus implanted and laser annealed boron doped Si

Implantation of P in B bulk doped Si (hole concentration = 2.1×10²⁰ cm^?3) followed by multiple pulse laser annealing with a XeCl laser has produced the incorporation of P in substitutional sites of the matrix and also charge carrier compensation. We report in this paper light scattering studies of these samples, in which a decrease of the hole-induced softening of the Si-Raman line is observed. This softening depends on the type and concentration of free carriers and thus, in our case, on the degree of compensation. This softening is discussed in terms of the interaction of the continuum of free carrier excitations with the Raman phonon. We also report the observation of the vibrations of ¹¹B-³¹ P pairs.     

Lattice reordering in Pb implanted Ge crystals

Channeling effect and sheet resistivity techniques have been used to investigate the damage induced by 40 keV Pb implantation in Ge crystals. At 450° the reordering of the Ge lattice occurs simultaneously to the out-diffusion of the implanted Pb atoms while the recovery of the sheet resistivity occurs at higher temperatures. 90% of the implanted atoms still retained in the crystal are located in substitutional sites. Work supported in part by Centro Siciliano di Fisica Nucleare e di Structura della Materia and by Gruppo Nazionale di Struttura della Materia del Consiglio Nazionale delle Ricerche.     

Surface analysis of thermally annealed porous silicon

Quasi-monocrystalline porous silicon (QMPS) has high potential for photovoltaic application for its enhanced optical absorption compared to bulk silicon in the visible range of solar spectrum. In this study, QMPS was formed from low porosity (∼20-30%) porous silicon (PS) produced by electrochemical anodization, and thermal annealing in the temperature range 1050-1100 °C under pure hydrogen ambient for a duration of 30 min. We analyzed the material surface by grazing incidence X-ray diffraction (GIXRD), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and dynamic secondary ion mass spectroscopy (SIMS) study. The crystallinity was confirmed by GIXRD while FESEM studies revealed that the surface layer is pore free with voids embedded inside the body. AFM studies indicated relatively smooth and uniform surface and the dynamic SIMS study showed the depth profiles of impurities present in the material.     

Laser induced reorder in Pb implanted Ge

Ge samples implanted with 40 keV Pb at a fluence of 3×10¹⁵/cm² were irradiated with ruby laser single pulses of 15ns duration. Reordering of the damaged layer occurs for energy density irradiation above 0.6 J/cm². The Pb atoms redistribute with a large component at the sample surface which is easily etched off. The remaining part of Pb impurities is substitutionally located, and the concentration exceeds the solid solubility limit by three order of magnitude. The formation of the metastable solution is explained in terms of a transient liquid layer produced during laser irradiation.