Diffusion Of Antimony Research Articles

Influence of boron on radiation enhanced diffusion of antimony in delta-doped silicon

The silicon samples used in this work contain a sequence of alternating boron and antimony spikes grown by molecular beam epitaxy. These samples were irradiated with 2.5 MeV protons at elevated temperatures ranging from 580 °C to 830 °C and characterized by secondary-ion mass spectrometry. The energy of the proton beam was chosen such that the generation rate of point defects can be considered as uniform throughout the delta-doped layers. For each sample the boron and the antimony diffusion coefficient are increased under irradiation as compared to their diffusivity in unirradiated areas. A measurable diffusion of antimony is observed in samples containing both boron and antimony spikes even at temperatures as low as 580 °C while a reference sample containing only an antimony spike do not exhibit any radiation enhanced diffusion, even at 830 °C. The boron diffusion coefficient increases as the irradiation temperature increases but the antimony diffusion coefficient decreases for the highest irradiation temperature investigated.

Engineering the diffusion behavior of dopants (B, Sb) in silicon by incorporation of carbon

Carbon doping of silicon is a subject of high interest since at high concentration (> 1×10 18 cm −3 ), carbon can reduce or even suppress the undesirable diffusion of boron in silicon-based bipolar transistors. To understand this macroscopic behavior, processes of point defect interactions (i.e. between dopants, vacancies and self-interstitials) have to be analyzed. The reduction of the boron diffusion by carbon is known to be due to the creation of a self-interstitial undersaturation. In this work we discuss the influence of the oversaturation of vacancies also produced by a high carbon concentration during annealing. Experiments with a vacancy diffusing dopant, antimony, are demonstrated to prove this effect: in a carbon rich sample, the antimony diffusion is enhanced about eight times compared to samples with a much lower carbon concentration. We also investigate the carbon co-precipitation with oxygen. We explain this affinity by an exchange of point defects and a volume compensation.

XPS investigation of the equilibrium segregation of antimony at germanium surface

Abstract X-ray Photoelectron Spectroscopy (XPS) has been used to investigate the antimony segregation at Ge surface. Heat treatments of various durations have been carried out under vacuum at T =600°C. Etching Ge surface with Argon ions prior to the heat treament enhances drastically the segregation process. A high value of the antimony diffusion coefficient ( D =7×10 −10 cm 2 /s) was obtained from the experimental data. A shift of the Ge core levels towards the high binding energies was observed as the dopant surface density increases. The shift was related to the band bending that results from a high density of surface states.

Vacancy and oxygen behavior in carbon highly doped silicon

ABSTRACTCarbon doping of silicon has gained interest since in high concentrations, carbon can reduce oreven suppress undesirable diffusion of the base dopant boron in silicon-based bipolar transistors. This behavior can only be understood in taking into account the silicon point defects i.e. vacancies and self-interstitials. In this work, we observe the oversaturation of vacancies produced by a high carbon concentration duringannealing. Experiments with a vacancy diffusing dopant, Antimony, are shown and prove this effect: in a carbon rich sample, the antimony diffusion is enhanced about 8 times compared to samples with a much lower carbonconcentration. We also investigate the carbon co-precipitation with oxygen. The carbon precipitation, asSiC, is facilitated with a high oxygen concentration. We explain this affinity by an exchange of point defects and a volume compensation. Finally, we show the precipitation of oxygen in relation to the vacancy oversaturation at 900°C.

Antimony and Boron Diffusion in Silicon and Silicon Germanium under the Influence of Point Defects Injection by Rapid Thermal Anneal

ABSTRACTThe effect of point defect injection on the diffusion of antimony and boron in silicon and silicon-germanium alloys has been studied by comparison of inert with injection diffusions. In this work, Sb and B in Si were used as control wafers to investigate Sb and B diffusion behavior in Si0.9Ge0.1. The point defect injection technique was carried out by rapid thermal annealing (RTA) Sb and B in Si and Si0.9Ge0.1 samples with the various surface coatings in either oxygen or ammonia atmospheres to inject either interstitial or vacancy defects. The diffusion profiles for as-grown and RTA annealed samples were measured by Secondary Ion Mass Spectrometry (SIMS). Diffusivities for B in Si and Si0.9Ge0.1 were obtained using computer simulations of the measured boron profiles for their annealed samples. Sb diffusion in Si and Si0.9Ge0.1 was found enhanced by vacancy injection and retarded by interstitial injection. The enhanced B diffusion in Si and Si0.9Ge0.1 was found by interstitial injection. These results confirm that Sb diffusion in Si0.9Ge0.1 is primarily dominated by vacancy-mediated mechanism, while B diffuses in Si0.9Ge0.1 by an interstitially mediated mechanism. The effect of the RTA diffusion time on the B diffusion in Si and Si0.9Ge0.1 has also been investigated. The diffusivity versus diffusion time of B in Si and Si0.9Ge0.1 for inert and injection samples is presented. It was found that the shorter annealing time had the faster diffusion. This suggested that it caused by transient diffusion effect arising from point defects.

Antimony and boron diffusion in SiGe and Si under the influence of injected point defects

The diffusion of Sb and B in both Si and SiGe is studied in this work. Injection of both interstitial- and vacancy-type point defects using rapid thermal annealing (RTA) in both NH3 and O2 atmospheres is calibrated for Sb diffusion in Si, before examining Sb diffusion in SiGe and B diffusion in Si and SiGe. Measurement of the diffusion retardation or enhancement under defect injection conditions will elucidate the diffusion mechanism and allow determination of the diffusivity, necessary for modeling of device fabrication processes. These experiments confirm the predominant mechanism for diffusion of Sb in Si and SiGe to be vacancy-mediated, while the predominant mechanism for B appears to be interstitial-mediated in Si and SiGe. The diffusivity values measured for B in Si and SiGe are reported.

Semiconductor surface diffusion: Nonthermal effects of photon illumination

Nonthermal influences of photon illumination on surface diffusion at high temperatures have been measured experimentally. Activation energies and pre-exponential factors for diffusion of germanium, indium, and antimony on silicon change by up to 0.3 eV and two orders of magnitude, respectively, in response to illumination by photons having energies greater than the substrate band gap. The parameters decrease for n-type material and increase for p-type material. Aided by results from photoreflectance spectroscopy, we suggest that motion of the surface quasi-Fermi-level for minority carriers accounts for much of the effect by changing the charge states of surface vacancies. An additional adatom-vacancy complexation mechanism appears to operate on p-type substrates. The results have significant implications for aspects of microelectronics fabrication by rapid thermal processing that are governed by surface mobility.

Diffusion of Boron, Phosphorus, Arsenic, and Antimony in Thermally Grown Silicon Dioxide

We studied the diffusion of dopant impurities, that is, ion‐implanted boron, phosphorous, arsenic, and antimony in and determined the diffusivity of the impurities in using secondary ion mass spectrometry and a process simulator. We also revealed anomalous diffusion of the dopant impurities in . © 1999 The Electrochemical Society. All rights reserved.

Activation volume for antimony diffusion in silicon and implications for strained films

The diffusivity of Sb in Si is retarded by pressure, characterized at 860 °C by an activation volume of V*=+0.07±0.02 times the Si atomic volume. V* is close to values inferred from atomistic calculations for a vacancy mechanism. Our results for hydrostatic pressure are used to predict the effect of biaxial strain on Sb diffusion. The prediction matches measured behavior for Sb diffusion in biaxially strained Si and Si–Ge films. This work lends additional support to the predominance of the vacancy mechanism for Sb diffusion and demonstrates the first steps in the development of a capability for predicting the effect of nonhydrostatic stress on diffusion.

POINT DEFECT REDISTRIBUTION IN SI1-XGEX ALLOYS

Using high resolution secondary ion mass spectrometry (SIMS) measurements we have studied the effects of germanium content on antimony diffusion in strained Si1−xGe x layers. Samples were molecular beam epitaxy (MBE) grown Si1−xGe x buried layers incorporating in situ doped antimony delta-layers. These were annealed for a variety of times and temperatures, following which SIMS profiles were taken and from these diffusivities were calculated. The results of a diffusivity versus germanium content study and a diffusivity versus time study are presented; equilibrium antimony diffusion coefficients in alloys of up to 30% germanium are given along with possible transient effects. Changes in antimony diffusivity with composition are attributed to changes in the vacancy population and the vacancy enthalpy of migration. Comparison with the diffusivity of boron versus germanium content in silicon-germanium alloys leads to the proposal that, in silicon-rich alloys, boron diffuses predominantly via the interstitialcy mechanism. The dependence of diffusivity on germanium content for boron is different from that of antimony and it is proposed that the boron diffusion mechanism changes from largely interstitialcy in silicon to vacancy in germanium—the change occurring at around 40% germanium.

The Effect of Grown-In Point Defects on Sb Diffusion in MBE-Grown Si and Sige

ABSTRACTThe diffusion of antimony in Si and SiGe under the influence of grown-in point defects is studied in this work. The layers were grown by very low temperature MBE, and the diffused profiles measured using SIMS analysis. Fast diffusion of Sb is observed in both Si and SiGe. and is thought to be caused by grown-in point defects, specifically vacancies, arising from the very low temperature MIBE growth. The vacancies may be removed by heat treatments. and it was found that the processing the samples received before the heat treatments caused the most substantial diffusion. Comparison of the diffusivities for inert diffusion at 850°C following the heat treatments suggests 30 minutes at 800°C is sufficient to remove the majority of the grown-in defects. The diffusion of Sb in Si is thus demonstrated to be a very sensitive monitor of grown-in vacancies, and dopants which diffuse at least partly by vacancy mediated processes would be expected to be affected by this effect.

Experimental Study of Self-Diffusion in Silicon Using Isotopically Enriched Structures

ABSTRACTSelf-diffusion in silicon has been studied using epitaxially grown isotopically enriched structures under nonequilibrium concentrations of intrinsic point defects created by thermal oxidation and nitridation. Comparison of identical anneals for self, antimony, and phosphorus diffusion in silicon enables us to determine bounds on the fractional contributions of microscopic mechanisms for Si self-diffusion in the temperature range 800–1100°C. We obtain direct experimental evidence for a dual vacancy-interstitial mechanism of self-diffusion in silicon and show that the fractional contribution of each mechanism has a weak dependence on temperature.

Fraction of Interstitialcy Component of Phosphorus and Antimony Diffusion in Silicon

The effect of nitride films on the diffusion of phosphorus and antimony in silicon has been investigated, in order to extract the fractional interstitialcy component of these dopant diffusion. Nitride film deposited on silicon substrate is used as an extrinsic source of vacancies. The phosphorus diffusion is retarded and the antimony diffusion is enhanced in silicon under nitride films. By observing the variation of the retardation in phosphorus diffusion and the enhancement in antimony diffusion, it is determined that the fraction of interstitialcy component in phosphorus and antimony diffusion is approximately 0.96 and 0, respectively.

Carrier dynamics in type-II GaSb/GaAs quantum dots

The optical properties and dynamics of charge carriers in self-organized arrays of type-II (staggered band lineup) GaSb/GaAs quantum dots are studied. Interband absorption from type-II quantum dots is evidenced; the energetic positions of quantum dot absorption peaks coincide with those apparent in photoluminescence spectra. (Sb,As) intermixing with an antimony diffusion length of about 1 nm is found to make an important contribution to the observed transition energies. Dipole layer formation and quantum dot state filling contribute to the luminescence blueshift with increasing excitation density. The recombination rate of electrons with localized holes drastically depends on the average carrier density. When several carriers are localized at each dot, decay time constants around 5 ns, quite similar to type-I systems, are observed. Individual, spatially indirect excitons decay with much larger time constants close to 1 \ensuremath{\mu}s. The decay time of quantum dot luminescence is independent of the temperature in the measured range $T<~65\mathrm{K}$ as expected for zero-dimensional excitons.

Impurity Diffusion in SiGe Alloys: Strain and Composition Effects

ABSTRACTThe advent of epitaxial-growth techniques dedicated to the growth of epitaxial layers of group-IV semiconductors and their alloys has opened up new possibilities for novel types of diffusion experiments and thus for critical tests of existing diffusion theories. It is now possible to grow test structures for diffusion consisting of well-defined narrow distributions of tracer impurities in epitaxial layers of biaxial-strained or relaxed alloys of different compositions. This enables studies of alloy effects and/or strain effects on diffusion with varying strain energy for a well-defined type of strain (tensile or compressive). A review is presented on recently published results on impurity diffusion in strained and relaxed, epitaxial SiGe alloy layers. As almost all these studies have focused on boron and antimony diffusion, these two impurities will have the leading roles in this review.

Impurity Diffusion in SiGe Alloys: Strain and Composition Effects

ABSTRACTThe advent of epitaxial-growth techniques dedicated to the growth of epitaxial layers of group-IV semiconductors and their alloys has opened up new possibilities for novel types of diffusion experiments and thus for critical tests of existing diffusion theories. It is now possible to grow test structures for diffusion consisting of well-defined narrow distributions of tracer impurities in epitaxial layers of biaxial-strained or relaxed alloys of different compositions. This enables studies of alloy effects and/or strain effects on diffusion with varying strain energy for a well-defined type of strain (tensile or compressive). A review is presented on recently published results on impurity diffusion in strained and relaxed, epitaxial SiGe alloy layers. As almost all these studies have focused on boron and antimony diffusion, these two impurities will have the leading roles in this review.

Rutherford back-scattering measurements of antimony diffusion in nanocrystalline copper

Antimony diffusion in nanocrystalline copper with average grain size about 50 nm and porosity 75% of theoretical value was studied at the temperature range 50–100 °C using Rutherford backscattering spectrometry. Based on the metallographic data, a diffusion cluster model is proposed. According to this model, diffusion occurs along cluster boundaries following by nanograins boundaries diffusion. Both grain and cluster boundary diffusion coefficients of Sb in n-Cu were calculated from this model. Obtained activation energy values for Sb diffusion along grain (0.39 eV) and cluster (0.41 eV) boundaries are close to each other, and more probably describe surface mass transport than grain boundary.

Diffusion in relaxed and strained SiGe layers

A review is given of recent experimental studies of Si-Ge interdiffusion and boron and antimony diffusion in relaxed and biaxial-tensile and biaxial-compressive strained Si1-xGex for 0 ⩽ x ⩽ 0.50.

Fabrication of n- and p-channel in-plane-gate transistors from Si/SiGe/Ge heterostructures by focused laser beam writing

Focused laser beam writing is applied for thermally activated diffusion of dopants into strained Si/Ge modulation-doped heterostructures. Lateral p- and n-type potential barriers of sub-μm width are achieved by local diffusion of boron and antimony into n- and p-type heterostructures, respectively. The potential modulation is determined from the temperature dependence of the thermionic current over the barrier. These npn and pnp structures can be used to fabricate in-plane-gate transistors which show transistor action up to room temperature.

Diffusion of Sb in relaxed Si1−xGex

Diffusion of antimony in relaxed Si1−xGex alloy layers grown by molecular beam epitaxy has been studied as a function of the composition for 0≤x≤0.5. The diffusivity of antimony was found to increase with the Ge alloy content, and the extracted activation energies for diffusion were found to decrease with increasing germanium content in the investigated composition range. The activation energies, however, are significantly higher than the corresponding activation energies obtained by an extrapolation between the activation energy in pure silicon and germanium.