Antimony Implantation Research Articles

P-Type ZnO Films Made by Atomic Layer Deposition and Ion Implantation.

Zinc oxide (ZnO) is a wide bandgap semiconductor that holds significant potential for various applications. However, most of the native point defects in ZnO like Zn interstitials typically cause an n-type conductivity. Consequently, achieving p-type doping in ZnO is challenging but crucial for comprehensive applications in the field of optoelectronics. In this work, we investigated the electrical and optical properties of ex situ doped p-type ZnO films. The p-type conductivity has been realized by ion implantation of group V elements followed by rapid thermal annealing (RTA) for 60 s or flash lamp annealing (FLA) on the millisecond time scale in nitrogen or oxygen ambience. The phosphorus (P)-doped ZnO films exhibit stable p-type doping with a hole concentration in the range of 1014 to 1018 cm-3, while antimony (Sb) implantation produces only n-type layers independently of the annealing procedure. Microstructural studies of Sb-doped ZnO show the formation of metallic clusters after ms range annealing and SbZn-oxides after RTA.

Deep level transient spectroscopy study of heavy ion implantation induced defects in silicon

Defects introduced by low fluence arsenic, antimony, erbium, and bismuth ion implantation have been investigated as a function of annealing temperature using deep level transient spectroscopy (DLTS) and Laplace-DLTS. The defects produced by heavy ion implantation are stable up to higher temperatures than those introduced by electron irradiation and low mass ions. This result is attributed to the enhanced defect interactions that take place in the dense collision cascades created by heavy ion implantation. As a consequence, broadened DLTS features are apparent, especially after annealing. Using high energy resolution Laplace-DLTS, the well-known singly charged divacancy and vacancy-donor pair are accompanied by additional apparent defect signals. This shows that Laplace-DLTS is highly sensitive to the type of damage present, and extreme care must be exercised for reliable Arrhenius analysis.

Electrostatically defined silicon quantum dots with counted antimony donor implants

Deterministic control over the location and number of donors is crucial to donor spin quantum bits (qubits) in semiconductor based quantum computing. In this work, a focused ion beam is used to implant antimony donors in 100 nm × 150 nm windows straddling quantum dots. Ion detectors are integrated next to the quantum dots to sense the implants. The numbers of donors implanted can be counted to a precision of a single ion. In low-temperature transport measurements, regular Coulomb blockade is observed from the quantum dots. Charge offsets indicative of donor ionization are also observed in devices with counted donor implants.

Nanotechnology Investigation of Ultra-shallow Junctions of Antimony (Sb) Implants in Conventional Silicon (Si)

The sheet resistance of the doped region in ultra-shallow junctions is critical to the speed of non-strained engineered integrated circuits. Maintaining low sheet resistance for antimony Sb implanted in Si is a difficult challenge to meet the performance requirements of future Complementary Metal Oxide Semiconductor devices (CMOS). A developed Differential Hall Measurements (DHM) is utilized to measure the dopant carrier concentration profile matches with the atomic profile measured by Secondary Ion Mass Spectroscopy (SIMS) for electrical characterization of the formed ultra-shallow junction. Present results show that decreasing the ion implant energy as 40 keV, 12 keV, 5 keV and 2 keV for the given implant dose under rapid thermal annealing (RTA) in the range from 600°C to 1100°C for 10s, results in an increase in sheet resistance from ~200 Ω/sq to ~850 Ω/sq with reduction in electrical activation percentage from ~90% to ~30%. Also the conductivity mobility decreases with implant energy while increases with annealing temperature. This reduction in electrical activation is due to reduction in junction depth from 60 nm at 40 keV to 17 nm at 2 keV accompanied with higher peak Sb concentration (≥ 2 × 1020 cm-3) as implant energy decreases for annealing temperature less than 800°C for 10s. Higher annealing temperature (i.e. > 800°C) does not improve the electrical activation while increases the sheet resistance due to the out diffusion of Sb from the active region. The best results that nearly satisfying industrial ITRS requirements corresponds to the following parameters: 5 keV implant energy with sheet resistance 400 Ω/sq, electrical activation 60%, conductivity mobility 50 cm2/Vs, peak Sb concentration of 4 × 1020 cm-3 and junction depth 22 nm.

Simulation of phosphorus, arsenic or antimony ion implantation in silicon targets

AbstractThe aim of this work was to study the behaviors of P+, As+ and Sb+ ions implanted in silicon targets. The investigation was mainly performed by simulation using the SRIM2006 (stopping and range of ions in matter) program. Several quantities, such as the depth profiles of the ion concentration, stopping powers and radiation damage, were predicted. Besides, an experimental study was carried out particularly for the case of Sb+ ions. The antimony ion implantation was performed to a dose of 5 × 1015 Sb+ cm−2 at 120 keV energy into an Si(100) target. The samples were analyzed by means of Rutherford backscattering spectroscopy (RBS) using He+ particles. A discrepancy between the experimental and simulated antimony depth profiles was revealed. In the case of phosphorus and arsenic, the simulated projected ranges (Rps) were compared with literature values and good agreement has been obtained. Finally, it is necessary to note that the predictions of some effects related to ion implantation (annealing temperature, crystallographic orientation of the targets, multi‐implantations, etc.) are not possible via the SRIM code. Copyright © 2010 John Wiley & Sons, Ltd.

Experimental characterization of monocrystalline Si targets implanted with Sb + ions

Monocrystalline silicon targets were submitted to a beam of antimony ions. The Si(1 1 1) substrates were implanted at an energy of 120 keV, at room temperature, to a dose varying from 1×10 15 to 5×10 15 Sb + cm −2. To recover the radiation defects generated by Sb + ions, a thermal annealing was performed, at 900 °C for 30 min under very high vacuum. The study of antimony ion implantation in the monocrystalline silicon targets was performed by means of different experimental techniques: X-ray diffraction, optical and electrical measurements. The perturbations enhanced by Sb + ion implantation and the recovery of the damage were investigated with great interest. Although the selected techniques are not frequently applied to investigate such phenomena, they have provided important results. In as-implanted specimens, it was found that the radiation damage increased with the increase of antimony dose. After the annealing treatment, a good recovery of defects was obtained especially in the samples implanted with the low dose (i.e. 1×10 15 Sb + cm −2).

High temperature antimony ion implantation in strained silicon-on-insulator

We present experimental results on shallow junction formation in strained silicon-on-insulator by antimony ion implantation and standard rapid thermal processing. An attempt is made to obtain Sb activation without layer amorphization by implanting Sb at elevated temperature. The focus is on studying the Sb activation during implantation at high temperature. Rutherford backscattering spectrometry and secondary ion mass spectroscopy are employed for characterization of Sb diffusion in amorphous and crystalline Si. The results are discussed in terms of the defect reaction kinetics involved.

Improved determination of phosphorus contamination during ion implantation by SRP and simulations

Experimental determination of phosphorous cross-contamination during antimony implantation is presented. As a suitable structure for this experiment, a buried layer was employed which is created by implanting antimony followed by a long diffusion process. The implanted samples were analysed by SIMS and spreading resistance (SRP) methods. SRP method has been improved by applying a correction for the carrier spilling effect. A conversion chart for p– n junction depth dependence on phosphorus doping has been calculated by program SUPREM-IV. Comparison of SRP and SIMS methods has shown that SRP method can be used for monitoring the phosphorus cross-contamination and can be easily implemented as an in-line monitor and present an alternative to expensive and time consuming SIMS analysis.

MEIS study of antimony implantation in SIMOX and vacancy-rich Si(1 0 0)

Medium energy ion scattering was used to study the distribution of ion-implanted Sb dopant in Si with excess vacancies and separation by implanted oxygen (SIMOX) substrates and the effects of thermal treatments. Extra vacancies in Si were generated by N or O pre-implantations at high temperature. Effects related to the different chemical nature of the pre-implanted species are expected under these conditions. Different Sb annealing behaviours and distributions were observed for O and N pre-implanted Si. The oxygen-containing samples (SIMOX and O pre-implanted Si) presented higher substitutionality after long annealing times. The nitrogen pre-implanted Si presented the lowest amount of segregated Sb and more uniform dopant distribution. Both pre-implanted samples, N and O, had a large dopant loss to the atmosphere during annealing.

Determination of phosphorus contamination during antimony implantation by measurement and simulation

Experimental determination of phosphorus cross-contamination during antimony implantation is presented. As a suitable structure for this experiment, a buried layer was employed which is created by implanting antimony followed by a long diffusion process. The samples implanted in different implanters were analysed by secondary ion mass spectrometry (SIMS), four-point probe and spreading resistance methods. The obtained results were compared with those calculated by program SUPREM-IV. Methods that can and cannot be used to determine phosphorus contamination during antimony implantation and to estimate the fluence of phosphorus being co-implanted with antimony are described in detail.

A novel split-gate MOSFET design realized by a fully silicided gate process for the improvement of transconductance and output resistance

Work function tuning of nickel silicide (NiSi) gates was utilized to fabricate a novel split-gate MOSFET with improved device performance. The MOSFET with a NiSi split gate has been achieved by implanting antimony into the polysilicon gate from the drain side with a tilt angle, followed by a full nickel-silicidation process. The laterally nonuniform antimony implantation causes the NiSi gate work function to vary from the source side to the drain side due to the dopant segregation effect. Improved current drive and output resistance are observed in the MOSFET with such a NiSi split gate. Metal gate advantages and NiSi process simplicity were also realized in the split-gate process, and gate oxide quality did not degrade due to the low temperature process. This split-gate design is expected to be applicable in the nanoscale regime by optimizing process conditions.

Energy Dependence of Radiation Damage in Sb-Implanted Si(100)

Extended defects formed by antimony ion implantation in Si(100) are investigated as a function of the implant energy. After implantation, spike annealing and furnace annealing are performed to examine the evolution of defects. The amorphization/recrystallization of the implanted layer is examined by transmission electron microscopy (TEM), photothermal characterization, and Raman spectroscopy. Secondary-ion mass spectroscopy is employed to identify the dopant distribution before and after annealing. Cross-sectional TEM reveals that, at a dose of , Sb implantation is sufficient to induce an amorphous-like layer in Si(100). After spike annealing, the amorphous-like layer restores to the crystalline state, but defects are observed when the Sb implantation energy is greater than . For implantation, extended defects appear at the near-surface and the end-of-range (EOR) regions. It is observed that near-surface defects diminish after spike annealing at temperatures higher than , while the EOR defects become coarse at . A comparison between the spike annealing and the furnace annealing for the sheet resistance and the EOR defect is also addressed.

안티몬 이온주입시 Sb2O3빔튜닝 방법 및 모니터링 연구

안티몬 이온주입시 Sb₂O₃빔튜닝 방법 및 모니터링 연구

Concentration profiles of antimony-doped shallow layers in silicon

Antimony implants at 40 keV and at a dose of 4 × 1014 cm−2 have been characterized for their potential use in n-type shallow junction formation. The electrical characterization was done using sheet resistivity and Hall effect measurements. High electrical activities (>80%) and low sheet resistance values (<200 Ω/□) were obtained for annealing temperatures below 800 °C. A novel differential Hall effect technique was used to obtain doping profiles at a depth resolution down to 1 nm, with a comparison made between these and Rutherford backscattering (RBS) measurements of the atomic profile as a function of annealing temperature. The antimony shows insignificant diffusion for annealing temperatures of 800 °C and below, with junction depths of about 60 nm. Electrical activation correlates well with the substitutional fraction of antimony determined by RBS.

Study on End-of-Range Defects Induced by Sb Implantation

ABSTRACTExtended defects formed by antimony ion implantation in Si(100) was investigated as a function of the implant energy. The implanted layer was examined by cross-sectional electron microscopy (TEM). Post-implantation spike-annealing was also performed from 950°C to 1095°C to examine evolution of defects. From the TEM study, the threshold energy to induce visible defects for Sb implantation was found to be more than 50 keV. A mapping for the location of defects was constructed by TEM and secondary ion mass spectroscopy (SIMS). The end-of-range (EOR) defects, which were possibly formed during the solid phase epitaixy regrowth, were located near the lower bound of the transition region. For 70-keV implantation, extended defects appear at the near-surface and the EOR region. It was observed that the near-surface defects diminished after annealing at more than 1050°C, while the EOR defects became coarsening at 1095°C.

The Local Structure of Antimony in High Dose Antimony Implants in Silicon by XAFS and SIMS.

AbstractOne of the important challenges in semiconductor industry is to sustain high concentration of dopant atoms electrically active in very small areas. In investigating the optimum post implantation treatment methods that will help to attain these conditions, the local structural information around the dopant atom is crucial. In this study, we have used secondary ion mass spectroscopy (SIMS) and x-ray absorption fine structure spectroscopy (XAFS) to obtain the concentration depth profiles and the local structural information around the Sb atom in laser thermal annealed (LTA) Sb implants in Si wafers. The Sb implant doses used in this work are 6.4x1015/cm2 and 2.0x1016/cm2. The XAFS results for the 6.4x1015/cm2 Sb dose sample do not exhibit any rhombohedral-Sb precipitation as the Fourier Transformed (FT) data can be fit successfully using only substitutional-Sb in the Si lattice sites. However, a multi-shell analysis of the Fourier Transformed (FT) data for the 2.0x1016/cm2 Sb dose sample clearly indicates there is a substantial contribution from the Sb-Sb scattering, which is a signature of precipitated form of Sb.

Implanted collector profile optimization in a SiGe HBT process

Optimization of implanted collector doping profiles for a high-speed, low-voltage SiGe HBT process has been investigated experimentally and by device simulations. A low-energy antimony implantation has been combined with a standard selectively implanted collector using phosphorous, to achieve improved control of the collector doping profile. The simulations indicate that the narrow n-type doping peak formed by the antimony implantation allows the cut-off frequency f T to be increased without degrading the collector emitter breakdown voltage BV CEO. The fabricated devices demonstrate a highest f T of 60 GHz. Depending on the collector profile BV CEO values between 1.5 and 2 V were obtained.

Frequency optimization of Si MESFET model with Pearson distribution (FMA)

We present a new analytical model for switching characteristics of Si d-MESFETs using Pearson distribution (FMA) under thermal annealing. The analysis is carried out with phosphorus, arsenic and antimony implants. The effects of profile shape on the switching characteristics are analysed. A detail investigation of drain-source resistance and time constants is reported. The dependence of implant dose and energy has also been studied. The analysis is further extended to demonstrate the figure of merit of a FET device which leads to the optimization of device performance in high frequencies.

Formation of Counter Doped Shallow Junctions by Boron and Antimony Implantation and Codiffusion in Silicon

ABSTRACTVery shallow p+/n junctions (lower than 60 nm) have been fabricated by implanting Sb and subsequently BF2, at a higher dose, in a n-type Si substrate. The preamorphisation with Sb avoids the B channeling and increases the n-type doping in the junction region, thus confining the depth of the p layer. Furthermore, both the transient enhanced diffusion, being the B implanted in a preamorphized layer, and the standard diffusion, due to the pairing between donors and acceptors, are strongly reduced. This procedure allows us to obtain very shallow junctions even after annealings with relatively high thermal budget, like 800 C/8h, or 900 C/lh, or 950 C/15min or 1000 C/60s. Dopant diffusion is strongly affected by the direct donor-acceptor interaction. Good agreement between experimental and simulation results can only be obtained using a simulation code which takes into account the formation of neutral, near immobile, Sb-B pairs.

Antimony implantation into Si-B doping superlattices—damage and enhanced diffusion

The influence of a heavy Sb ion implantation and subsequent annealing cycles in the temperature range of 800–1000 °C on B-delta doping superlattices in silicon layers grown by molecular beam epitaxy (MBE) was analyzed. Secondary ion mass spectroscopy (SIMS) measurements of these structures are used to investigate the generation and diffusion of point defects. The enhanced diffusion of B from the delta doping spikes in as grown and Sb implanted layers was theoretically described by solving the diffusion equation using the point defect model of TSUPREM−4 for different initial point defect distributions. To fit the experimental SIMS profiles the positively charged B-interstitial diffusion coefficient was changed from the default value of D=0.68 cm2/s to D=0.45 cm2/s. It was found that the given MBE growth process produces interstitials and vacancies with an almost constant average value of about 5×1016 cm−3. The Sb-implanted B modulation doped superlattice allows us to obtain a depth profile of the defect concentration. Assuming an overlapping of a constant value of 5×1016 cm−3 for interstitials and vacancies caused by the MBE growth with a distribution coming out of a damage calculation during Sb implantation, consisting of a flat high concentration region with an exponential decrease towards the level of the MBE layer, the main features of the B diffusion profile in the superlattice could be fitted. Thus, a simple initial point defect distribution model after implantation was able to explain the experimental situation.