Silicon Interstitial Atoms Research Articles

Radiative and Magnetically Stimulated Evolution of Nanostructured Complexes in Silicon Surface Layers.

The effect of a weak magnetic field (B = 0.17 T) and X-irradiation (D < 520 Gy) on the rearrangement of the defective structure of near-surface p-type silicon layers was studied. It was established that the effect of these external fields increases the positive accumulated charge in the region of spatial charge (RSC) and in the SiO2 dielectric layer. This can be caused by both defects in the near-surface layer of the semiconductor and impurities contained in the dielectric layer, which can generate charge carriers. It was found that the near-surface layers of the barrier structures contain only one deep level in the silicon band gap, with an activation energy of Ev + 0.38 eV. This energy level corresponds to a complex of silicon interstitial atoms SiI+SiI. When X-irradiated with a dose of 520 Gy, a new level with the energy of Ev + 0.45 eV was observed. This level corresponds to a point boron radiation defect in the interstitial site (BI). These two types of defect are effective in obtaining charge carriers, and cause deterioration of the rectifier properties of the silicon barrier structures. It was established that the silicon surface is quite active, and adsorbs organic atoms and molecules from the atmosphere, forming bonds. It was shown that the effect of a magnetic field causes the decay of adsorbed complexes at the Si–SiO2 interface. The released hydrogen is captured by acceptor levels and, as a result, the concentration of more complex Si–H3 complexes increases that of O3–Si–H.

Exploration of Defect Dynamics and Color Center Qubit Synthesis with Pulsed Ion Beams

Short-pulse ion beams have been developed in recent years and now enable applications in materials science. A tunable flux of selected ions delivered in pulses of a few nanoseconds can affect the balance of defect formation and dynamic annealing in materials. We report results from color center formation in silicon with pulses of 900 keV protons. G-centers in silicon are near-infrared photon emitters with emerging applications as single-photon sources and for spin-photon qubit integration. G-centers consist of a pair of substitutional carbon atoms and one silicon interstitial atom and are often formed by carbon ion implantation and thermal annealing. Here, we report on G-center formation with proton pulses in silicon samples that already contained carbon, without carbon ion implantation or thermal annealing. The number of G-centers formed per proton increased when we increased the pulse intensity from 6.9 × 109 to 7.9 × 1010 protons/cm2/pulse, demonstrating a flux effect on G-center formation efficiency. We observe a G-center ensemble linewidth of 0.1 nm (full width half maximum), narrower than previously reported. Pulsed ion beams can extend the parameter range available for fundamental studies of radiation-induced defects and the formation of color centers for spin-photon qubit applications.

Strain relief via silicon self-interstitial emission in highly boron-doped silicon: A diffuse X-ray scattering study of oxygen precipitation

Oxygen precipitation in highly boron-doped Czochralski silicon (5 mΩ cm resistivity) was studied, and a strain-relieving mechanism involving the emission of silicon interstitial atoms (ISi) was identified. Strain-sensitive X-ray diffraction was employed, and through a comparison with complementary electron microscopy measurements a linear misfit strain ϵ=0.01 was determined. Different behavior concerning strain relaxation was measured for wafer-type samples (760 μm thickness) and thick samples (2 mm thickness), which was explained with out-diffusion of ISi in the thinner samples. Based on the experimental findings, a model was developed which invokes an increase in the solubility of interstitial silicon atoms upon boron doping. The model successfully accounts for different effects of boron doping on oxygen precipitation in silicon, which were reported on in literature such as preferential octahedral morphology of precipitates, enhanced nucleation, and relaxed accommodation of the precipitates with respect...

Identification of photoluminescence P line in indium doped silicon as InSi-Sii defect

Indium and carbon co-implanted silicon was investigated by low-temperature photoluminescence spectroscopy. A photoluminescence peak in indium doped silicon (P line) was found to depend on the position of a silicon interstitial rich region, the existence of a SiNx:H/SiOx stack and on characteristic illumination and annealing steps. These results led to the conclusion that silicon interstitials are involved in the defect and that hydrogen impacts the defect responsible for the P line. By applying an unique illumination and annealing cycle we were able to link the P line defect with a defect responsible for degradation of charge carrier lifetime in indium as well as boron doped silicon. We deduced a defect model consisting of one acceptor and one silicon interstitial atom denoted by ASi-Sii, which is able to explain the experimental data of the P line as well as the light-induced degradation in indium and boron doped silicon. Using this model we identified the defect responsible for the P line as InSi-Sii in neutral charge state and C2v configuration.

Large boron‐interstitial cluster modelling in BF3 plasma implanted silicon

AbstractBF3 plasma immersion ion implantation (PIII) is a promising technique in the race for highly boron doped P+/N ultra‐shallow junctions (USJs) in complementary metal oxide semiconductor (CMOS) silicon technologies. Implantation conditions used in BF3 PIII lead to high super‐saturations (≥1 × 1020 cm–3) of both boron and silicon interstitial atoms in the implantation region. In such conditions, very large loop‐shaped boroninterstitial clusters (BICs) are formed during subsequent thermal anneals, as confirmed by transmission electron microscopy (TEM) measurements.In this study, amorphizing BF3 PIII implants (10 keV, 5 × 1015 cm–2) followed by different thermal anneals were carried out in order to investigate the large BICs precipitation. A ”large BICs“ model based on moments approach allowed to reproduce the experimental data including boron diffusion profiles (obtained by SIMS) and boron electrical activation obtained by Hall effect sheet resistance measurements.(© 2014 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Hydrostatic pressure effect on dislocation evolution in self-implanted Si investigated by electron microscopy methods

The influence of enhanced hydrostatic pressure on evolution of dislocations in self-implanted silicon during annealing at different temperatures was investigated by means of electron microscopy methods. It is found that the main cause of the pressure impact differs for various annealing temperatures. The annealing under enhanced pressure at lower temperature (1070 K) has a negligible effect on structure of dislocations located in a thin layer (end-of-range (EOR) defects). At this temperature, enhanced pressure mainly increases the density of microdefects with oxygen precipitation. It is found that after high-temperature annealing (1400 K), enhanced hydrostatic pressure (HP) reduces dislocation density near the surface; however, dislocations extend deeper into the substrate as compared to the samples annealed under atmospheric pressure. The effect is attributed mainly to the reduction of silicon interstitial-atoms migration towards the surface due to increase in energy necessary to make silicon interstitial atom occupy a lattice site at the surface.

Interstitial charge states in boron-implanted silicon

It is becoming increasingly clear that simulation models of transient enhanced diffusion (TED) in silicon need to incorporate interstitial charging effects accurately in order to adequately reproduce experimental data near the surface and near the underlying junction. However, in the case of boron TED, the relevant charge states and ionization levels of both boron and silicon interstitial atoms are known only imperfectly. The present work attempts to describe this behavior more accurately via simulations of implanted profiles that employ a model whose kinetic parameters have been determined with considerable confidence by rigorous systems methods. The results suggest that B has two relevant charge states: (+) and (−). The corresponding states for Si are (++) and (0). The effective ionization levels for B and Si are 0.33±0.05 and 0.12±0.05eV above the valence band maximum, respectively.

Direct evidence of the recombination of silicon interstitial atoms at the silicon surface

In this experiment, a Si wafer containing four lightly doped B marker layers epitaxially grown by CVD has been implanted with 100 keV Si + ions to a dose of 2 × 10 14 ions/cm 2 and annealed at 850 °C for several times in an RTA system in flowing N 2. TEM and SIMS analysis, in conjunction with a transient enhanced diffusion (TED) evaluation method based on the kick-out diffusion mechanism, have allowed us to accurately study the boron TED evolution in presence of extended defects. We show that the silicon surface plays a key role in the recombination of Si interstitial atoms by providing the first experimental evidence of the resulting Si ints supersaturation gradient between the defect region and the surface. Our results indicate an upper limit of about 200 nm for the surface recombination length of Si interstitials at 850 °C in a N 2 ambient.

Diffusion enhanced carbon loss from SiGeC layers due to oxidation

The effect of annealing 25-nm-thick pseudomorphic Si{sub 0.7865}Ge{sub 0.21}C{sub 0.0035} layers on silicon substrates in nitrogen or oxygen at 850{sup o}C was examined for different silicon cap thicknesses and annealing times by x-ray diffraction and secondary-ion mass spectrometry. Carbon is found to diffuse rapidly out of the SiGeC layer and even out of the sample entirely, an effect that is enhanced by oxidation and thin cap layers. All substitutional carbon can be removed from the sample in some cases, implying negligible formation of silicon-carbon complexes. Furthermore, it is found that each injected silicon interstitial atom due to oxidation causes the removal of one additional carbon atom for the SiGeC layer.

Silicon Interstitial Driven Loss of Substitutional Carbon from SiGeC Structures

ABSTRACTThe effect of annealing silicon capped pseudomorphic Si0.7865Ge0.21C0.0035 or Si0.998C0.002 layers on silicon substrates in nitrogen or oxygen at 850°C was examined using x-ray diffraction (XRD) and secondary ion mass spectrometry (SIMS). Most substitutional carbon is lost from the alloy layers due to carbon out-diffusion rather than from precipitation. The carbon is found to diffuse more rapidly out of the SiGeC layer than the SiC layer after nitrogen and the carbon is found to leave the sample entirely, an effect that is enhanced by oxidation and thin cap layers. All substitutional carbon can be removed from the sample in some cases implying negligible formation of silicon-carbon complexes. Furthermore, it is found that each injected silicon interstitial atom due to oxidation causes the removal of one additional carbon atom for the SiGeC layer.

Thermal evolution of extended defects in implanted Si:: impact on dopant diffusion

Annealing of ion-implanted Si leads to the formation of various extrinsic defects which affect dopant diffusion. In this paper, we describe the mechanisms by which, small clusters evolve into {1 1 3} defects, then transform into dislocation loops of either faulted or perfect type, upon annealing, the former being the only one to survive for long annealing times. This approach assumes that these defects exchange Si interstitial atoms upon annealing and that the reduction of the formation energies of the defects due either to their size increase or to a change in their structural characteristics is the driving force for their thermal evolution. Since the supersaturation of silicon interstitial atoms in dynamical equilibrium with these defects is an exponential function of these formation energies, a realistic description of the time-evolution of this supersaturation in the defect region and in the whole wafer responsible for transient-enhanced diffusion of boron, can be obtained.

Investigation of the interaction between silicon interstitials and dislocation loops using the wafer bonding technique

In this work, we investigate (i) the interaction of silicon interstitial atoms during thermal oxidation of silicon with a dislocation loop layer positioned at different distances from the surface as well as (ii) the interaction between two loop layers positioned at different depth distances. In both experiments, interstitials are injected by surface oxidation. The results show a linear dependence of the injection flux of interstitials with the inverse of the distance of the loop layer from the surface and a small leakage (16%) of the injected interstitials escaping from the upper and becoming bounded to the deeper loop layer. The experiments are performed using the wafer bonding technique that allows versatility on their design.

The Impact of Point Defects on Stress-Induced Dislocation Generation in Silicon

AbstractFactors responsible for the onset of dislocation generation in the fields of localized high stresses have been studied in LOCOS-isolated test structures by means of preferential etching, junction leakage analysis, and computer simulation. A strong correlation between densities of stacking faults and dislocations was observed in the experiments. Defect distributions also correlated to leakage currents. 2D simulations of stresses, interstitial injection, and stacking fault growth during field oxidation showed that maximum resolved shear stress in the structures did not exceed the critical level for dislocation generation and that the agglomeration of silicon interstitial atoms did not play a notable role in dislocation nucleation. Dislocation and stacking fault formation was attributed to surface mechanical damage introduced during plasma processing.

Charge state of intrinsic interstitial defects and their substitution of boron atoms in the silicon lattice

The displacement of boron atoms from silicon lattice sites by silicon interstitial atoms was studied, by galvanomagnetic and x-ray methods. The substitution is controlled by the charge state of the interstitial defects. The charge transfer was effected by a change in the level of ionization during implantation by varying the ion-beam density and during annealing by additional electron bombardment.

The effect of carbon and boron on the accumulation of vacancy-oxygen complexes in silicon

Abstract By means of IR-absorption measurements the dose dependencies of the concentrations of vacancy-oxygen complexes (VO), interstitial oxygen atoms (QI), substitutional carbon atoms (CS) and interstitial carbon-oxygen complexes (CIOI) in n- and p-type silicon irradiated with 1.1 MeV electrons have been investigated. The observed increase of the production rate of VO-complexes with the rise of carbon and boron atoms concentrations (these impurities act as sinks for silicon interstitial atoms) has been explained in terms of annihilation of the vacancies and interstitials on the oxygen atoms. The results obtained show that boron atoms are more effective sinks than carbon atoms for the interstitial silicon atoms. That seems to be connected not only with the higher probability of boron injection into interstitial position but also with the further capture of interstitial silicon atoms on the interstitial boron. i.e. with the interstitial cluster formation.

The creep behaviour of some silicon-containing titanium alloys

An investigation has been made of the secondary creep behaviour of binary TiSi alloys containing ~ 0.6 and 1 wt.% Si and of a Ti-5 wt.% Zr1 wt.% Si alloy. The Ti-1 wt.% Si alloy, as-quenched from the β-phase region, showed a high resistance to creep; this is associated with silicon in solid solution and the consequent dynamic strain ageing effect arising from a silicon-interstitial atom interaction. The precipitation of Ti 5Si 3 by ageing reduced the creep resistance. The presence of zirconium substantially improved the creep resistance in the aged condition. Values of the “stress exponent” at strain rates >10 −10 s −1 were in the range 5–20, but showed no systematic variation with alloy composition or heat treatment. Values of the apparent activation energy for secondary creep depended on the silicon content, and were greater than those for diffusion of substitutional elements in titanium.

Dynamic strain ageing in some titanium-silicon alloys

An investigation has been made of the mechanical properties of titanium and of Ti-0.5 wt.% Si and Ti-1.O wt.% Si alloys in the temperature range 300–900K. Dynamic strain ageing (D.S.A.), characterised by serrated yielding, has been observed between 700 and 825K and has been studied by measurements of strain rate sensitivity and of stress relaxation. The D.S.A. is attributed to interstitial atoms, and is increased in magnitude by the presence of silicon, probably due to lattice distortions resulting from silicon-interstitial atom pairs; the temperature of dynamic strain ageing is reduced by increases in silicon or oxygen content. The powerful solid solution strengthening role of silicon at elevated temperatures may arise from the intensification of the interstitial strain ageing effect by the silicon.