Si Implantation Research Articles

Stacking Fault Energy of Si Nanocrystals Embedded in SiO2

Si nanocrystals (Si nc) were produced by the implantation of Si+ into a SiO2 film on (100) Si, followed by high-temperature annealing. High-resolution transmission electron microscopy (HRTEM) observation has shown that a perfect dislocation (Burgers vector b=(1/2)〈110〉) can dissociate into two Shockley partials (Burgers vector b=(1/6)〈112〉) bounding a strip of stacking faults (SFs). The width of the SFs has been determined from the HRTEM image, and the stacking fault energy for Si nc has been calculated. The stacking fault energy for Si nc is compared with that for bulk Si, and the formation probability of defects in Si nc is also discussed. The results will shed a light on the dissociation of dislocations in nanoparticles.

Microscopic observation of lateral diffusion at Si–SiO2 interface by photoelectron emission microscopy using synchrotron radiation

The lateral surface diffusion at Si–SiO2 interface has been observed at nanometer scale using photoelectron emission microscopy (PEEM) combined with synchrotron soft X-ray excitation. The samples investigated were Si–SiOx micro-patterns prepared by O2+ ion implantation in Si (001) wafer using a mask. The lateral spacial resolution of the PEEM system was about 41nm. The brightness of each spot in the PEEM images changed depending on the photon energy around the Si K-edge, in proportion to the X-ray absorption intensity of the corresponding valence states. It was found that the lateral diffusion occurs by 400–450°C lower temperature than that reported for the longitudinal diffusion at the Si–SiO2 interface. It was also found that no intermediate valence states such as SiO (Si2+) exist at the Si–SiO2 interface during the diffusion. The observed differences between lateral and longitudinal diffusion are interpreted by the sublimated property of silicon monoxide (SiO).

Quantum confinement and electron spin resonance characteristics in Si-implanted silicon oxide films

The nature of electron and hole trapping in silicon ion–implanted silicon oxide (SiO2) with a dose of 1016 cm−2 were studied using photoluminescence and electron spin resonance (ESR) measurements. We observed an ESR signal with g = 2.006 after hole and electron injections. These results unambiguously imply that the Si nanoclusters created by the high-dose Si implants are both electron and hole traps in the SiO2 films.

Deep Energy Levels Formed by Se Implantation in Si

To transfer a photon with a 1.55μm wavelength into an electron in an integrated optoelectronic silicon waveguide detector, selenium-doped silicon with deep energy levels is used. The deep levels in the silicon with implanted selenium are studied. Three levels are observed and their captured cross sections, concentrations and in-depth profiles are measured.

Structure of self-implanted silicon annealed under enhanced hydrostatic pressure

Implantation of any ions at a sufficiently high dose and energy (E) into single-crystalline Si leads to the creation of amorphous Si (aSi), with damages peaking near the projected range (R p) of implanted species. Enhanced hydrostatic pressure (HP) at a high temperature (HT) influences the recrystallization of aSi. The structure of self-implanted Czochralski silicon (Si+ dose, D=2×1016 cm−2, E=150 keV, R p=0.22 μm) processed for 5 h at 1400 or 1520 K under HPs up to 1.45 GPa was investigated by X-ray, secondary ion mass spectrometry and photoluminescence methods. The implantation of Si produces vacancies (V) and self-interstitials (Sii). Vacancies and Siis form complex defects at HT–HP, also with contaminants (e.g. oxygen, always present in Czochralski silicon). The mobility and recombination of V and Sii as well as the kinetics of recrystallization are affected by HP, thus processing at HT–HP affects the recovery of aSi.

Transportation of carriers in silicon implanted SiO 2 films during ionizing radiation

Silicon ion implantation has been proved to be an effective method for total-dose hardening of SiO 2 in MOS devices such as buried oxides in SOI devices, while the mechanisms are still in discussion. In this work, behavior of 10 keV X-ray induced carriers in silicon implanted thermal SiO 2 was investigated by comparing with Ar implanted SiO 2. Photoluminescence (PL) spectroscopy and TRIM calculation were used to characterize the defects of the ion implanted SiO 2 films. Metal–Oxide–Semiconductor (MOS) structures were fabricated for electrical characterization of the oxides. Positive or negative gate bias was applied during the irradiation to control the separation and transportation of radiation induced electrons and holes. Flatband voltage shifts and are extracted from high frequency capacitance–voltage (C–V) measurement results which are taken prior to and after certain total dose irradiation. The experiment result shows that both Ar and Si implantation and followed anneal could eliminate the net positive charge in SiO 2 irradiated by X-ray. But different with Ar implanted oxide, in Si implanted oxide, the reduction of positive charge is highly dependent on the implanted Si ion fluence, and is well consistent with silicon nanoclusters evolvement tendency. From these results we conclude that along with increased electron trapping at the nanostructures which is suggested by previous studies, enhanced hole trapping and recombination caused by implantation induced vacancy defects are critical mechanism of reduced total ionizing dose effects on Si implanted oxides.

Erbium environments in erbium-silicon/silica light emitting nanostructures

Co-doping of SiO2 with Si and Er to achieve silica fibre amplifiers has resulted in encouraging levels of light emission, much above those of Er-only doped SiO2. However, different fabrication methods, i.e., co-implantion and sequential implantation of Er and Si, has led to several factors difference in light levels. This paper looks into the reasons for these differences by establishing structure and local stoichiometry of the created entities via analytical transmission electron microscopy. In both cases Si-nanocrystals (NCs) have formed in the SiO2 matrix. In the former case Er-ions are co-located with /integrated within the NCs, in the latter case NCs and Er are separate. By assessing the NCs' internal and interfacial structure with the surrounding material, we attempt to identify chemical/structural Er-phases/defects and their effect on the sensitising efficiency in the Er:Si-NCs system; high resolution phase contrast- and high angle dark field imaging as well as nano-scale spatially resolved electron energy core loss- and plasmon-spectroscopy carried out in an aberration corrected dedicated STEM lend valuable support to these studies.

Etch-free formation of porous silicon by high-energy ion irradiation

In this study, porous silicon was fabricated without any chemical etching by self-ion implantation of crystalline Si performed at high temperature and at high fluences. The irradiated silicon samples, which remained crystalline under high temperature ion irradiation, exhibited an increased porous fraction with increasing sample temperature at a given fluence, up to the maximum tested temperature of 650 °C. Extremely high ion fluences of at least 2 × 10 18 ions/cm 2 were necessary to produce significant void growth. Comparisons between the porous silicon structures and irradiation-induced porous networks in Ge, GaSb, and InSb are made, and differences in the formation conditions for these porous networks are discussed.

Effect of the annealing treatments on the transport and electroluminescence properties of SiO2 layers doped with Er and Si nanoclusters.

ABSTRACTWe studied the effect of RTP and furnace annealing on the transport properties and electroluminescence of Si-nc embedded in SiO2 layers, and of Er ions coupled to Si-nc. The light emitting devices have been fabricated in a CMOS line by implantation of Si and Er in SiO2. The results show that for the same annealing temperature, furnace annealing decreases electrical conductivity and increases probability of impact excitation, which leads to an improved external quantum efficiency. Correlations between phenomenological transport models, annealing regimes, and erbium electroluminescence are observed and discussed.

Depth profiling of micrometer‐order area by mesa‐structure fabrication

AbstractFabricating mesa structures with photolithography in samples for analysis is a promising method for microarea analysis in SIMS depth profiling because undesired ions originating from the surroundings of the analysis area are eliminated. We investigated the depth profiles of B implants in Si by varying the primary ion energy, beam size, mesa size, raster area and gate area ratio. When a 50 µm × 50 µm mesa was rastered over a 60 µm × 60 µm area with a 15‐keV Cs+ beam, a dynamic range for B of 3 × 105 and a detection limit of 3.2 × 1015 atoms/cm3 were obtained. As for a smaller mesa of 9 µm × 9 µm, the depth profiles of BSi− taken over a 30 µm × 30 µm raster area with a 5 keV beam were quite comparable to those over 13 × 13 and 11 µm × 11 µm raster areas with a 15 keV beam. The major advantages of using a mesa fabrication method are minimization of the raster area and maximization of the gate area ratio without deterioration of profile quality, which is quite favorable for microarea analysis. A very small mesa of 4 µm × 4 µm was also successfully analyzed, and a dynamic range of 4 × 103 was obtained. Copyright © 2010 John Wiley & Sons, Ltd.

Er离子注入的富硅SiO2MOS-LED的可见和红外电致发光特性

Metal-oxide-semiconductor structure of ITO/Si-rich SiO2∶Er/Si containing erbium ions and silicon nanocrystals was fabricated by ion implantation of Si and Er combined with post-annealing.The electroluminescence spectra and current-voltage characteristics were measured to investigate the influence of silicon concentration on the excitation mechanism of luminescence centers and conductance process.It was found that the excitation mechanism of erbium ions was variational in the MOS-LED with silicon content.For the silicon concentration less than 5%,the upper levels of erbium can be excited by resonant energy transfer from silicon-oxygen deficiency centers,which induce an enhancement of the 522 nm peak emission intensity of Er3+ ion.For the silicon concentration above 5%,the excess silicon formed silicon nanocrystals by post-annealing.The direct tunneling of electrons between silicon nanocrystals dominate the conductance,resulting a decrease of average energy of hot electrons and quenching of all the electroluminescence peaks of erbium.

Silicon and selenium implantation and activation in In 0.53Ga 0.47As under low thermal budget conditions

Si and Se implantations have been systematically investigated in In 0.53Ga 0.47As. Different implant doses and various activation anneals with temperatures up to 700 °C have been examined. Raising Si implant dose from 1 × 10 14 to 1 × 10 15 cm −2 was found to increase the active doping concentration by about a factor of two. As confirmed by Transmission Electron Microscopy (TEM) and electrical measurements, the rest of the implanted Si ions remain as defects in the crystal and degrade the mobility. It was also confirmed from Secondary Ion Mass Spectrometry (SIMS) that the Si diffusivity in InGaAs is negligible up to 700 °C implant activation anneal making Si a suitable option for the formation of shallow junctions in InGaAs. The activation efficiency, sheet resistance, carrier density and mobility data of 25 keV Se and Si implanted InGaAs layers are also presented under various activation anneal temperatures.

Study of annealing induced redistribution of implanted Au in Si: Fluence dependence

One hour 500 °C air annealing induced movement of implanted Au in Si have been studied for 32 keV Au implantation in Si, in the fluence range of 1 × 10 15 – 1 × 10 17 ions cm - 2 . Samples were characterized using Rutherford backscattering spectrometry and cross-sectional transmission electron microscopy. The results indicate that, depending on the initial state of Au in the matrix, there is a clear difference in the diffusion behaviour of Au in Si. When Au is precipitated as gold-silicide nanoclusters inside the Si matrix, annealing is found to cause diffusion of Au into the bulk Si. Compared to this, for a random atomic distribution of Au in an amorphous Si matrix, annealing is found to result in out-diffusion of Au towards the surface.

The effects of the annealing time on helium implantation in Si

The modifications induced in silicon samples by helium implantation before and after isothermal annealing at 673 K have been investigated. The surface morphology has been detected by atomic force microscopy. A hillock structure is observed on the sample surface before and after annealing for 5–10 min. Surface blister formation is observed with an increasing annealing time. The variation of crystal damage with annealing time has been investigated by Rutherford backscattering/channeling. The intensity of the damage peak first increases with annealing time, reaches maximum at an annealing time of 60 min and then decreases. Helium-induced bubbles and residual defects have been observed by transmission electron microscopy, which shows that dislocations are close to the bubbles.

Thermal stability of intermediate band behavior in Ti implanted Si

Ti implantation in Si with very high doses has been performed. Subsequent Pulsed Laser Melting (PLM) annealing produces good crystalline lattice with electrical transport properties that are well explained by the Intermediate Band (IB) theory. Thermal stability of this new material is analyzed by means of isochronal annealing in thermodynamic equilibrium conditions at increasing temperature. A progressive deactivation of the IB behavior is shown during thermal annealing, and structural and electrical measurements are reported in order to find out the origin of this result.

Study of erbium-doped silicon nanocrystals in silica

Er-doped SiO2 and Er-doped Si-NCs embedded in a SiO2 matrix were produced by Er and/or Si ion beam implantation of a Si (100) substrate. The composition and distribution of implanted Er varies in samples either with or without Si implants. HAADF and EELS detail in samples with Si implants, the Si and Er distribution is identical, and within a band of ~110 nm width at ~75 nm below the SiO2 surface. Intense PL emission at 1.54 μm confirms formation of ErSi2, for the majority of aggregates, is unlikely. The present investigation details most Si-NCs are surrounded by Er2O3, or possess this phase within.

Study of Si implantation into Mg‐doped GaN for MOSFETs

AbstractIn this paper we focus on activation and diffusion during annealing of silicon after implantation into Mg‐doped GaN epitaxial layers. The Si diffusion was analyzed for different capping materials and compared to an uncapped sample. Investigation of the Si concentration obtained from secondary ion mass spectroscopy (SIMS) and comparison with calculation revealed several diffusion constants. Different diffusion behaviours at the surface were detected for different Si concentrations around the solubility of Si in GaN. Further, we found similar Si activation efficiencies in GaN for high and low fluences, after taking into account the compensation of electrons by the p‐type background doping. In addition, we investigated the insulation between Si implanted islands in p‐type GaN and the effect of additional Ar+ implantation. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Effects of fin width on memory windows in FinFET ZRAMs

The effects of fin width on the memory windows of nMOS and pMOS FinFET transistors operated in ZRAM mode are investigated as a function of applied back-gate programming bias during the write pulse. The memory window and retention time of ZRAM cells programmed with a back-gate pulse decrease with decreasing fin width, which is a result of the increased electrostatic shielding by the side-gates of the FinFETs. The gate length and fin width dependences of the memory windows obtained for devices programmed via gate-induced drain leakage (GIDL) are also evaluated for potential ZRAM operation. In contrast to back-gate programming, the memory window increases with decreasing fin width for GIDL programming, which is a much more desirable device scaling trend. Retention times of up to several seconds can be observed in ZRAMs programmed by GIDL with ms length pulses. Memory cycling results demonstrate that the GIDL programming conditions used here do not degrade the device significantly. Shorter retention times are typical of excess charge in the ZRAM body, whereas the relatively longer retention times observed here may be attributed to the injection and trapping of charge in the gate and/or buried oxide near the drain. This could point the way towards improved ZRAM retention properties, since processing techniques such as Si implantation can enhance charge trapping in SOI buried oxides, which in turn may increase retention times for shorter write pulses.

Probing Ar ion induced nanocavities/bubbles in silicon by small-angle x-ray scattering

Small-angle x-ray scattering (SAXS) measurements have been performed to investigate the nanocavities/bubbles and the amorphous silicon surrounding the cavities/bubbles generated after high fluence medium-energy (60 keV) Ar ion implantation in single crystalline Si as a function of incidence angle (with respect to the surface normal of the sample). The measurements were carried out using a high flux/high transmission laboratory scale SAXS set up with Mo-Kα radiation in transmission geometry. The scattering data have been used to calculate the average size (Dave), number density (dN), and volume fraction (Vf) of cavities/bubbles in ion induced amorphous layer of the crystalline Si substrate. The novelty of the SAXS technique applied in the present case lies on its ability to detect ultrafine defect features of size even less than 1 nm, which is otherwise impossible from the transmission electron microscopy measurements usually employed for inert gas ion induced cavities/bubbles in amorphous silicon.

Optical properties of Si+ implanted PMMA

In the present work, low energy ion beam irradiation was used for surface modification of polymethyl-methacrylate (PMMA) using silicon (Si+) as the ion species. After high doses ion implantation of Si+ in the polymer material, a characterization of the optical properties was performed using optical transmission measurements in the visible and near infra-red (IR) wavelength range. The optical absorption increase observed with the ion dose was attributed to ion beam induced structural changes in the modified material.