Solid Phase Epitaxy Of Si Research Articles

Molecular dynamics simulations of the solid phase epitaxy of Si: Growth mechanism and orientation effects

The solid phase epitaxy of an amorphous layer on crystalline silicon is studied by means of molecular dynamics. Three stacks of 5120, 4928, and 5184 atoms respectively oriented along the [100], [110], and [111] directions are annealed with the Tersoff interatomic potential. The regrowth proceeds via the motion of a planar interface for [100], the formation of facets for [110], and the crystallization within (111) bilayers for the third case. In the absence of crystallization defects, the velocities of regrowth are similar for [100] and [110] and two to five times lower for [111]. Moreover, defects were obtained in 8% of the cases along [100], 19% of the cases along [110], and 52% of the cases along [111] with a systematic formation of one or more twins in the last case. The results are confronted with a schematic model of the solid phase epitaxy.

Dopant-stress synergy in Si solid-phase epitaxy

The influence of dopants on stressed solid-phase epitaxy of Si was studied in B-doped material up to B concentration of ∼3.0×1020cm−3 and stress of 1.0±0.1GPa. As per the generalized Fermi level shifting model of growth enhancement in the presence of electrically active impurities, it is advanced that application of compressive stress may increase the energy difference between intrinsic Fermi and acceptor levels thus making dopant and stress effects synergistic in growth kinetics.

Effects of patterned, stressed SiN overlayers on Si solid phase epitaxy

Striking nonuniformities are observed in the solid phase epitaxy (SPE) of blanket amorphized Si layers recrystallized in the presence of stress distributions induced by a patterned SiN overlayer. Measurements conducted for a range of SiN feature sizes and intrinsic stress values allowed us to isolate the effects of stress on the crystallization front. It is concluded that SiN-induced variations in SPE rates arise both from line-edge stresses, which scale with feature stress and increase SPE rates where the hydrostatic stress is compressive, and a SiN body effect, which suppresses SPE rates under the SiN features, independent of SiN stress state.

Silicon in functional epitaxial oxides: A new group of nanostructures

The ability to integrate low-dimensional crystalline silicon into crystalline insulators with high dielectric constant (high-k) can open the way for a variety of novel applications ranging from high-k replacement in future nonvolatile memory devices to insulator/Si/insulator structures for nanoelectronic applications. We will present an approach for nanostructure fabrication by incorporation of crystalline silicon into epitaxial oxide that is based on a solid-phase epitaxy of Si. In dependence on the preparation conditions we obtained nanostructures containing an either ultra-thin single-crystalline Si quantum-well buried in single-crystalline oxide matrix with sharp interfaces or Si-nanocrystals (ncs) embedded into single-crystalline oxide layer. As an example, we demonstrate the growth of Si buried in Gd2O3 and the incorporation of epitaxial Si clusters into single-crystalline Gd2O3 on silicon as well as silicon carbide substrates using molecular beam epitaxy. The leakage current of the obtained nanostructures exhibited negative differential resistance at lower temperatures. For structures containing Si-ncs a large hysteresis in capacitance–voltage measurements due to charging and discharging of the Si-ncs was obtained.

シリコンの固形成長速度へのヒ素原子の影響に関する分子動力学解析

Solid phase epitaxy (SPE) of Si is one of the most fundamental processes in semiconductor fabrication techniques. Many experimental studies have been carried out for understanding the growth mechanism. However microscopic mechanism is not well understood. In this study, we investigated the effect of arsenic atoms on the rate of Si SPE by using molecular dynamics simulation. In the case of non-doped Si, an activation energy of SPE is found to be 2.1±0.5eV, which shows good agreement with the experimental result (2.7eV). It is also found that the energy barrier of crystallization in a/c interface amounts to be about 0.6eV, which corresponds to defect migration process. It indicates other processes such as defect formation also control the SPE process. The SPE rate increases by 2 times for 3 at% As doping and 100 times for 5 at% As doping and an activation energy remains to be constant. The increase in SPE rate would be enhanced by defect formation process in amorphous silicon, which reflects the increase in self-diffusion of silicon atoms caused by active As atoms.

Fluorine incorporation during Si solid phase epitaxy

We have investigated the F incorporation and segregation in preamorphized Si during solid phase epitaxy (SPE) at different temperatures and for several implanted-F energies and fluences. The Si samples were amorphized to a depth of 550nm by implanting Si at liquid nitrogen temperature and then enriched with F at different energies (65–150keV) and fluences (0.07–5×1014 F/cm2). Subsequently, the samples were regrown by SPE at different temperatures: 580, 700 and 800°C. We have found that the amount of F incorporated after SPE strongly depends on the SPE temperature and on the energy and fluence of the implanted-F, opening the possibility to tailor the F profile during SPE.

Fluorine segregation and incorporation during solid-phase epitaxy of Si

We report on the F incorporation into Si during solid-phase epitaxy (SPE) at 580°C and with the presence of B and∕or As, clarifying the F incorporation mechanism into Si. A strong segregation of F at the moving amorphous–crystalline interface has been characterized, leading to a SPE rate retardation and to a significant loss of F atoms through the surface. In B- or As-doped samples, an enhanced, local F incorporation is observed, whereas in the case of B and As co-implantation (leading to compensating dopant effect), a much lower F incorporation is achieved at the dopant peak. The F enhanced incorporation with the presence of B or As is shown to be a kinetic effect related to the SPE rate modification by doping, whereas the hypothesis of a F–B or F–As chemical bonding is refused. These results shed new light on the application of F in the fabrication of ultrashallow junctions in future generation devices.

The role of antiphase boundaries during ion sputtering and solid phase epitaxy of Si(0 0 1)

The Si(001) surface morphology during ion sputtering at elevated temperatures and solid phase epitaxy (SPE) following ion sputtering at room temperature has been investigated using scanning tunneling microscopy. Two types of antiphase boundaries form on Si(001) surfaces during ion sputtering and SPE. One type of antiphase boundary, the AP2 antiphase boundary, contributes to the surface roughening. AP2 antiphase boundaries are stable up to 700 °C, and ion sputtering and SPE performed at 700 °C result in atomically flat Si(001) surfaces.

Reply to “Comment on ‘Molecular-dynamics simulations of solid-phase epitaxy of Si: Growth mechanisms’ ”

We have investigated atomic diffusion properties near the amorphous/crystalline $(a/c)$ Si(001) interface during solid-phase epitaxy (SPE) of Si based on molecular-dynamics simulations using the Tersoff potential. It has been found that the mean-square displacement of the Si atoms in an amorphous layer with a thickness of 10 \AA{} at the $a/c$ interface is larger than that in bulk amorphous Si. This can be attributed to local heating due to crystallization of amorphous Si during SPE growth.

Formation and Characterization of Spe Grown Ultra-Thin Cobalt Disilicide Film

AbstractUltra-thin epitaxial CoSi2 films formed by Co(3∼5nm)/Ti(1 nm)/Si(100) and Co(3∼5nm)/Si(lnm)/Ti(Inm)/Si are studied. The multilayers are deposited by ion-beam sputtering. Rapid thermal annealing (RTA) is used for silicidation. XRD, RBS, TEM, AFM, four-point probe, I-V and C-V measurements are carried out for characterization. The XRD spectra show the CoSi2 film formed by Co/Ti/Si or Co/Si/Ti/Si solid phase epitaxy has, epitaxial characteristic. XTEM shows that the film is continuous. RBS/Channeling shows that the formed CoSi2 has sharp interface with a minimum channeling yield of Co signal of 40%. AFM shows that the surface of ultra-thin CoSi2 film is smooth with a roughness of nearly 0.7 nm. The Rs∼T relationship shows that the CoSi2 films formed by Co/Si/Ti/Si reaction have the best thermal stability (stable up to 900°C). Those formed by Co/Ti/Si reaction are stable up to 850°C, while those formed by Co/Si reaction are only stable up to 750°C. By fitting the experimental I-V and C-V curves of the epitaxial CoSi2/Si Schottky diodes, barrier heights of around 0.6 eV and close to unity ideality factors are obtained.

Hydrogen effect on solid phase epitaxy of Si on Si (0 0 1) surface

Solid phase epitaxy (SPE) of amorphous Si layers of several tens of monolayers on hydrogen-adsorbed Si (0 0 1) substrates was studied in situ by low-energy time-of-flight (TOF) Rutherford Backscattering (RBS)-channeling spectrometry using 25 keV hydrogen ions, and by reflection high energy electron diffraction (RHEED). The SPE has not occurred at all for heating to 600°C even in the case of less than 1 ML adsorption of hydrogen on the Si (0 0 1) surface. Although the SPE has occurred for heating to 700°C, polycrystalline, or {1 1 1} faceted surface were formed. We did not obtain pronounced differences between the effects of the hydrogen adsorption of more or of less than 1 ML on the SPE of Si on Si (0 0 1). In the case of high density hydrogen-containing amorphous Si on a Si (0 0 1) clean surface the SPE has occurred at 600°C, and a {1 1 1} faceted surface was observed. Hydrogen adsorption obstructs the SPE of Si on Si (0 0 1) even if the coverage is less than 1 ML. The rise of the SPE temperature of amorphous Si on a hydrogen-adsorbed Si (0 0 1) surface is attributed to the hydrogen adsorption on the surface.

Stress reduction and interface quality of buried Sb δ doping layers on Si(001)

We have investigated the width dependence of Sb delta (δ) doping layers grown by Si solid phase epitaxy (SPE) on the Sb surface reconstruction prior to Si deposition. Depending on the Sb adsorption conditions a 2×1 and a 2×n surface reconstruction is observed. Measurements of crystal truncation rods and x-ray standing waves show a drastically reduced interface roughness and a better crystal quality for δ layers grown on Sb:Si(001)−2×n substrates in comparison to Sb:Si(001)-2×1, which we attribute to reduced surface stress of the Sb:Si(001)-2×n reconstruction.

Si/Pd ohmic contact to n -GaP based on thesolid phase regrowth principle

A Si/Pd ohmic scheme (contact resistivity ~2 × 10-4 Ω-cm2 ) annealed between 400 and 650°C has been developed for n-GaP (n~5 × 1017 cm3). The ohmic contact formation mechanism can be rationalised in terms of the solid phase regrowth (SPR) principle and the solid phase epitaxy of Si on n-GaP.

Formation of β-FeSi2, by thermal annealing of Fe-implanted (001) Si

Epitaxy of semiconducting β-FeSi2 on Si is of interest for optoelectronic device technology, because of its direct bandgap of ≈0.9 eV. Several techniques, including solid phase epitaxy (SPE) and ion beam synthesis, have been successfully used to grow β-FeSi2 on either Si (001) or (111) wafers. In this paper, we report the epitaxial formation of β-FeSi2 upon thermal annealing of an Fe-Si amorphous layer formed by ion implantation.Si (001) wafers were first implanted at room temperature with 50-keV Fe+ ions to a dose of 0.5 - 1×1016 cm−2, corresponding to a peak Fe concentration of cp ≈ 2 - 4 at.%, and subsequently annealed at 320, 520, and 900°C, in order to induce SPE of the implanted amorphous layer. Cross-sectional high-resolution electron microscopy (HREM) was used for structural characterization.We find that the implanted surface layer ( ≈100 nm thick) remains amorphous for samples annealed at 320°C for as long as 3.2 h, whereas annealing above 520°C results in SPE of Si, along with precipitation of β-FeSi2.

Comparison Between Ion-Beam and Thermal-Annealing Induced Solid Phase Epitaxy in Fe-Implanted Si

Rutherford backscattering spectrometry and transmission electron microscopy were used to compare thermally induced solid phase epitaxy (SPE) with ion-beam induced epitaxial crystallization (IBIEC) of Fe-implanted Si (001). It was found that thermal annealing leads to both Si SPE and β-FeSi2 precipitation at 520°C, but has no visible effect at 320°C. In contrast, Si SPE and FeSi2 precipitation occur at both 320 and 520°C, when ion irradiation is introduced. The precipitates grow epitaxially as γ-FeSi2 at 320°C, but consist of both β-FeSi2 and γ-FeSi2 at 520°C. It was also found that thermal annealing at 520°C results in Fe segregation toward the surface, while IBIEC basically retains the as-implanted Fe profile.

Si solid phase epitaxy on Si-Sb and Si-B surface phases

Results of LEED-AES study of the formation of buried Si-Sb and Si-B surface phases in Si(100) and Si(111) are presented, including preparation and characterization of surface phases, estimation of the crystalline quality of epitaxial Si films grown on surface phases, and examination of smearing of sharp concentration profiles in the growth direction subsequent to silicon epitaxial overgrowth.

Retardation and Enhancement in Lateral Solid Phase Epitaxy of Si on SiO2 by MeV Electron Beam Irradiation

ABSTRACTWe have demonstrated the high energy (MeV) electron beam irradiation effects on lateral solid phase epitaxy (L-SPE) of Si-on-insulator (SOI). Thinned samples were set on a hot stage in a 2 MeV electron microscope and L-SPE growth under 2 MeV electron irradiation conditions was monitored in-situ by using the same microscope. L-SPE growth rate for the irradiation dose of 1021 cm−2 was enhanced by about 1.5 times greater than that under unirradiated condition. For electron beam irradiation doses higher than about 1023 cm−2, L-SPE growth was suppressed. Displacement of Si atoms, contamination effect and ionization effect are discussed as causes for the growth rate retardation and enhancement of L-SPE by electron beam irradiation.

Effect of Nonhydrostatic Stress on Crystal Growth Kinetics

ABSTRACTThe effect of nonhydrostatic stresses on the solid phase epitaxial growth rate of crystalline Si(100) into self-implanted amorphous surface layers has been measured. Uniaxial stresses of up to 6 kbar (0.6 GPa) were attained by bending wafers over SiO2 rods and annealing at a temperature too low for plastic deformation to relieve the stress in the crystal, but high enough for solid phase epitaxial growth to proceed. The growth rate on the tensile side was greater than that on the compressive side of the wafer, in marked contrast to the enhancement observed from hydrostatic pressure. The phenomenology of an “activation strain”, the nonhydrostatic analogue of the activation volume, has been developed to characterize the results. Combined with the measurement of the activation volume, the measurement reported here permits us to characterize to first order the entire activation strain tensor corresponding to the transition state for solid phase epitaxy of Si(lOO). We conclude that the transition state for this process is “short and fat”; that is, the fluctuation to the transition state involves an expansion in the two in-plane directions and a contraction in the direction normal to the surface large enough to make the overall volume change negative. The symmetry of the measured activation strain tensor is inconsistent with all bulk point defect mechanisms for solid phase epitaxy. The relevance of the activation strain formalism to heteroepitaxy and vapor phase epitaxy is discussed.

Structural characterization of an Sb delta-doping layer in silicon

Delta-function doped layers in Si have been prepared by deposition of Sb on Si(001) followed by solid phase epitaxy of Si. The morphology and the crystal quality of the grown structures are characterized in situ during all stages of preparation by high-resolution Rutherford backscattering spectrometry. The obtained doping profile is found to consist of a <0.8-nm-wide spike and a 4-nm-long tail in front of the spike. A large fraction of about 70% of the Sb atoms is confined to the spike while the remaining 30% is located in the tail. Ion channeling and blocking measurements demonstrate that at least 95% of the Sb atoms is located on substitutional lattice sites. At temperatures exceeding 1000 K, the Sb profile broadens and Sb atoms diffuse towards the surface where they desorb.

Dependence of Al-Si/Si contact resistance on substrate surface orientation

The dependence of Si growth on substrate orientation in the aluminium-silicon system is investigated. The Si epitaxial growth is found to show a strong dependence on the substrate surface orientation similar to the growth from Si-implanted amorphous Si. The Si growth at contact cuts changes in its quantity with substrate orientation, and Si SPE (solid-phase epitaxy) does not occur seriously on -oriented substrates under the temperature in the experiment. As a result, the contact resistance of -oriented samples increases rapidly with sintering time and its dispersion also increases, while those of -oriented samples stay constant. The -oriented surface is the most prominent for the contact-resistance stability. >