High Current Implantation Research Articles

Accelerator of the ??-12? neutron generator as an implanter of hydrogen ions

The use of an updated accelerator of the НГ-12И neutron generator as a high-current implanter of hydrogen ions (protons and deuterons) with energies of 175–210 MeV into wafers made of crystalline silicon is described. The ion-beam scanning system used ensured nonuniformity in the irradiation of wafers with a diameter of 100 mm of <10%, which allowed the production of silicon-on-insulator wafers by the hydrogen splitting technique. The required particle fluence was ∼1017 cm−2. A slight refinement of the setup allows wafers with diameters of up to 200 mm to be irradiated. The design features of the setup as they apply to different temperature conditions (down to a temperature close to that of liquid nitrogen) of the irradiation of 100-mm-diameter wafers are described.

Radiation-induced change of polyimide properties under high-fluence and high ion current density implantation

Polyimide (PI) films were implanted with 40-keV Ar+ and 80-keV Ar(2+) ions in a fluence range of 5.0*10^14-1.5*10^17 cm-2 at ion-current densities of 1-16 uA*cm2. It is shown that the conductivity of the samples rises with the ion-current density at a fixed fluence. Electrophysical parameters of the polyimide change stepwise with the implantation fluence when it exceeds a certain value. The change of electrical parameters of the implanted PI correlates with that of the optical and paramagnetic characteristics. The phenomenon of complete volatilisation of argon implanted with an energy of 40 keV due to surface heating and disordering under the high-power beam is found. It is shown that the change of ion charge and energy at constant beam-power density causes only a quantitative change in the polymer characteristics. A model of PI alteration and carbonised phase formation, taking into account the action of the high-power ion beam and the peculiarities of PI chemical structure, is developed to explain the observed effects. Implantation at high ion-current density can be suggested as an efficient practical means to control polymer conductivity and other parameters

Secondary ion mass spectrometry analysis of implanted and rapid thermal processing annealed wafers for sub-100 nanometer technology

The characterization of ultrashallow junctions after implantation and subsequent rapid thermal processing (RTP) annealing is usually done in two ways. The sheet resistance of the junction is measured with a four-point probe and junction depth and dose are evaluated via secondary ion mass spectrometry (SIMS). After ultralow energy beamline implantation in a Varian VIISta 80 single wafer high current implanter the subsequent spike anneal for maximum activation and minimal diffusion was carried out on a Mattson 3000 Plus equipped with the flash-anneal controller. Junction depth profiling was done to monitor the influence of implant conditions and RTP annealing parameters. Measurements of junction depth, total dose, activated dose and uniformity were carried out on FEI Quadrupole SIMS tools. Queued measurements were performed on full wafers and small samples. Calibration of both junction depth and retained dose will be discussed. At very low beam energies (250 eV, oxygen, normal incidence) valuable information about depth profile shape, near surface concentration, and activated dose were obtained.

Formation of CeSi 2 on the Si surface upon high current pulsed Ce-ion implantation

Cerium-ion implantation was conducted to synthesize Ce-disilicide films on silicon wafers, using a metal vapor vacuum arc ion source. The continuous CeSi 2 films were directly obtained at relatively low temperature with neither external heating nor post-annealing and the surface morphology varied with the variation of the implantation parameters. The formation mechanism of the CeSi 2 phase is also discussed in terms of the temperature rise caused by ion beam heating and the ion dose in the far-from-equilibrium process of high current pulsed Ce-ion implantation.

Microstructural evolution of low-dose separation by implanted oxygen materials implanted at 65 and 100 keV

Thin separation by implanted oxygen substrates are attractive candidates for low-power, low-voltage electronic devices and can be obtained by low-dose, low-energy oxygen–ion implantation. We report in this study a variation of the process parameters that have never been investigated before, particularly for implantation with a high current density implanter. Characterization of the sample sets by transmission electron microscopy, secondary ion mass spectroscopy (SIMS), and Rutherford backscattering spectrometry (RBS) shows an optimum dose of 3.0 to 3.5 × 1017 O+/cm2 at 100 keV for forming a continuous buried oxide (BOX) layer compared to 2.5 × 1017 O+/cm2 at 65 keV. At this optimum condition for 100 keV, the thickness of Si top layers and BOX layers is in the range of 175–185 nm and 70–80 nm, respectively. Analysis of the breakdown voltage of small area capacitors shows a breakdown field in the range of 6.0–7.0 MV/cm, which is adequate for low-power, low-voltage devices. SIMS analysis shows that the maximum oxygen concentration of as-implanted samples is located at depths of 160 and 240 nm for the implantation energy of 65 and 100 keV, respectively. A significant redistribution of oxygen occurs at temperatures above 1300 °C during the ramping process. RBS analysis showed that a high-quality crystalline Si layer was produced after annealing at 1350 °C for 4 h. The defect density determined by the chemical etching method was found to be very low (&lt;300 defects per cm2) for all samples with a dose range of 3.0 × 1017 O+/cm2 to 6.0 × 1017 O+/cm2 implanted at 100 keV. However, a 65 keV sample with a dose of 4.5 × 1017 O+/cm2 contains about 109 defects per cm2. The larger defect density in the 65-keV sample may be due to the shift of oxygen depth distribution toward the surface, resulting in easier defect extension during the annealing process. The oxide precipitates in the Si overlayer play a key role in defect reduction by blocking the extension of dislocations to the surface.

Growth of DySi2 Layers on Si Surface by High-Current Dy-Ion Implantation

We report, in this paper, the synthesis of DySi2 layers on Si surfaces by high-current Dy-ion implantation in Si wafers using a metal vapor vacuum arc ion source. It was found that the continuous DySi2 layers could grow at a relatively low formation temperature of 190°C and that the surface morphology varied with the variation of the implantation parameters. The formation mechanism of the equilibrium DySi2 phase as well as the continuous DySi2 layer on Si surface is proposed in terms of ion beam heating and the effect of ion dose on the Dy-ion implantation process.

Formation of TaSi 2 and associated fractal growth on Si surface upon high current pulsed Ta-ion implantation

Using a metal vapor vacuum arc ion source, tantalum ion implantation was conducted to synthesize TaSi 2 phases on silicon wafers, and the continuous and stable TaSi 2 layers were directly obtained with neither external heating nor post-annealing. Interestingly, under some specific conditions, the formed TaSi 2 grains organized themselves in a fractal pattern featuring self-similarity. The mechanism of the TaSi 2 formation as well as the growth of the fractal pattern is discussed in terms of the temperature rise caused by the energetic Ta ions beam heating effect and the dose adjustment during high current pulsed Ta-ion implantation far from equilibrium.

Thick TiN films prepared by vacuum arc deposition and high energetic nitrogen ion beam dynamic mixing implantation

TiN films have many features, such as high wear resistance, high corrosion resistance and good oxidization resistance. With the technology of vacuum arc deposition and high current density nitrogen ion beam dynamic mixing implantation (DMI), the TiN film with a thickness of 33 μm and adhesion 58 N is synthesized on hard alloy and high-speed steel substrates. X-ray diffraction has been used to examine the crystal structure of the films. The results showed that the main phases presented in DMI films are TiN and Ti 2N and that the films revealed random growth. Cross-sectional scanning electron microscopy revealed the dense morphology and the thickness of the films. Micro-hardness tests showed that the average hardness of the films was about 2500 HK. Electrochemical experimental results indicated that DMI-TiN film had excellent corrosion resistance both in 3% NaCl solution and in 0.5 Mol H 2SO 4 solution.

Formation of MoSi 2 and associated fractal growth on Si surface upon high current pulsed Mo-ion implantation

Using a metal vapor vacuum arc ion source, continuous and stable MoSi 2 films were directly obtained by high current Mo-ion implantation into Si wafers with neither external heating nor post-annealing. Interestingly, under some specific conditions, the formed MoSi 2 grains organized themselves in fractal patterns featuring unique self-similarity. The mechanism responsible for the MoSi 2 formation as well as the growth of the fractal pattern is discussed in terms of the dynamic launching of the energetic Mo ions into Si, ion beam heating effect, and the effect of ion dose during high current Mo-ion implantation of far from equilibrium.

Formation of NdSi2 Phase by High-Current Nd-Ion Implantation

Continuous NdSi2 phase layers could be obtained by high-current Nd-ion implantation into Si using a metal vapor vacuum arc ion source and the formation temperature could be relatively low in the range from 165 to 320°C. Furthermore, the surface morphology of the Nd-ion implanted surface varied with the implantation parameters. The formation mechanism of the NdSi2 phase as well as its continuous layer is also discussed in terms of the temperature rise caused by ion beam heating and variations of the ion dose in the Nd-ion implantation process.

High current density nitrogen implantation of an austenitic stainless steel

Surface modification of AISI 304L austenitic stainless steel under high flux and low energy nitrogen ion implantation has been carried out at moderate temperatures in the range 270–400 °C with 1.2 keV ions and current densities between 0.5 and 1 mA/cm 2. The influence of temperature, current density and fluence on the nitrogen transport and the microstructure of the nitrided layer have been investigated. The nitrogen depth profiles have been determined by nuclear reaction analysis, the microstructure of the modified layers has been analysed by X-ray diffraction and transmission electron microscopy. It is shown that the processing temperature and the ion flux have a major influence on both the profile shapes and the unusually deep penetration depth of nitrogen. The results suggest that above a critical temperature the nitrogen transport increases rapidly giving rise to a flat depth profile. The formation of the well known expanded austenite γ N has been observed and its structure identified to a f.c.c. lattice containing a high density of stacking faults induced by the high level of internal stresses. The X-ray photoelectron spectroscopy study of the Cr2p 3/2, Fe2p 3/2 and N1s binding states demonstrates clearly the preferential bonding of chromium with nitrogen. The atomic transport of nitrogen and the profile shapes are discussed in relation with both the specific role of Cr and additional processes such as the formation of surface vacancies and adatoms.

Phase transformation of high speed steel after sequential nitrogen and boron high current density ions implantation

The present work continues the study of double high current ion implantation (HCII) of nitrogen and boron into AISI M2 high speed steel. The additional investigations of phase-structure state by conversion electron Mössbauer spectroscopy, glancing X-ray diffraction, Auger electron spectroscopy and tribological properties of steel were carried out. HCII of nitrogen is found to form precipitates of ε-Fe 2+ x (N,C) ( x=0.67, 1) and α″-Fe 16(N,C) 2 carbonitrides and causes strong sputtering of surface. Boron HCII forms boron film (20 nm in thickness) on the surface of steel. The best tribological properties were revealed for the N+B variant of HCII. The 2.2 times improvement of wear-resistance was reached because of surface boron films and carbonitrides enriched sublayer influence.

Structural and Morphological Evolution Emerging in Si Surface Layers upon High-Current Tb-Ion Implantation

We report, in this paper, the formation of the equilibrium TbSi2 phase and its associated surface morphology induced by high-current Tb-ion implantation into Si with applying a metal vapor vacuum arc ion source. It was found that continuous TbSi2 layers could be obtained at relatively low formation temperature ranging from 180 to 340°C and that the surface morphology varied with the variation of the implantation parameters. The formation mechanism of the equilibrium TbSi2 phase as well as its continuous layer is proposed in terms of the temperature rise caused by ion beam heating and variations of the ion dose in the high-current metal ion implantation process.

Fabrication of PrSi 2 layers and associated morphology on Si surface by a single-step high current Pr-ion implantation

PrSi 2 layers were fabricated on Si wafers with metal vapor vacuum arc ion implantation without in-situ-heating or post-annealing. Under optimal experiment conditions, the obtained PrSi 2 layers were of good crystalline structure and featured plain and continuous morphology. In addition, the formation mechanism of the PrSi 2 layers is also discussed in terms of the temperature rise caused by ion beam heating as well as the variation of ion implantation dose.

Formation of the ErSi2 phase and the associated fractal pattern on the Si surface upon high current Er-ion implantation

Using a metal vapor vacuum arc ion source, plain and continuous ErSi2 layers of good crystalline structure were formed on Si surfaces by high current Er-ion implantation. Interestingly, under some specific conditions, the formed ErSi2 grains organized themselves in a fractal pattern featuring self-similarity. The mechanism of the ErSi2 formation as well as the growth of the fractal pattern was discussed in terms of the dynamic launching of energetic Er ions into Si, beam heating effect, and the effect of ion fluence during the high current Er-ion implantation of far-from-equilibrium.

A very large Paul trap ion gun for delivering bunched low energy ion beams

Ions extracted from mass separators normally have energies in the range of tens of kilovolts and poor emittances, and are thereby not suited for soft landing, especially in ion deposition applications. In this article a system is described that has been developed for in-flight capture of continuous 60 keV ion beams and delivering them as low energy beam pulses of less than 1 μs duration and energies of less than 5 keV. They are also cooled so that their emittances and energy spreads are considerably reduced from those of the original beam. The basis of the system is a very large Paul trap as a collection system, together with a pulse-down cavity for modifying the energy of the delivered beam. The performance of the system has been analyzed using time-of-flight of the extracted ions. Experimental results are presented, together with numerical simulations of the results that lead to an understanding of the spatial and momentum properties of the ion collection in the trap. The results show how such collection systems can be designed for specific purposes, such as high-current implantation or precise implantation of smaller collections. Such a system can also be used where the ultimate destination is storage in an electromagnetic trap at ground potential.

Space charge compensation of low energy ion beam

Compensation of the space charge of high perveance, low energy ion beam in beam lines for ion implantation and isotope separation has been investigated. Space charge compensation and overcompensation by ions will be considered. Different mechanisms of the compensating particle formation such as ionization by the beam, secondary emission, electronegative gas admixture, and external plasma sources will be discussed. Advanced space charge compensation increases an intensity of low energy ion beam after analyzer magnet up to 3–4 times. Space charge compensation of positive ion beam by admixture of electronegative gases and damping of the beam instability will be discussed. Up to 6 mA of B+11 ions with energy 3 keV, 11 mA with 5 keV, and 18 mA with 10 keV have been transported through an analyzer magnet of a high current implanter with space charge neutralization by electronegative gases.

A decaborane ion source for high current implantation

Progressive semiconductor device scaling in each technology node requires the formation of shallower junctions, and thus lower energy implants. The difficulties associated with extraction and transport of low energy beams often result in a loss in wafer throughput. Implantation of boron using the molecular compound decaborane has been found to allow for the shallow implantation of boron without a significant design change in the implanter. The decaborane molecule has 10 boron atoms and 14 hydrogen atoms. The implanted dose is ten times the electrical dose and the implanted depth is equivalent to the depth of a boron beam at 1/11th of the extraction energy. This advantage can only be exploited with an ion source that does not destroy the fragile molecule. We report on the design of an ion source capable of ionizing decaborane without significant fragmentation of the molecule. After it was shown that the decaborane molecule fragments above 350 °C an ion source was designed to prevent thermal dissociation of the molecule. Competitive boron dose rates were achieved using this source in a commercial high current implanter. In addition, evidence is shown that a decaborane dimer is formed in the ion source and can be implanted.

Surface morphology and structural changes in insulators induced by high-current 60 keV Cu− implantation

Surface morphology and structural changes of amorphous (a-), crystalline (c-) SiO2 and MgAl2O4 spinel, implanted with high-current Cu− of 60 keV, were studied using atomic force microscopy. Kinetic variation of the surface morphology was evaluated by changing dose rate from 1 to 100 μA/cm2. In the cases of a-SiO2 and c-SiO2, the surface morphology significantly varied with dose rate: dome-type textures in the lower dose-rate region caused radiation-induced roughening, while net-type ones in the higher region occurred with radiation-induced smoothing. Step-height measurements showed radiation-induced expansion and compaction for c-SiO2 and a-SiO2, respectively. Radiation-induced amorphization is responsible for the expansion processes of c-SiO2. Contrarily, no amorphization was observed in the spinel up to dose rates of about 100 μA/cm2, although radiation-induced swelling, due to defect accumulation, was discernible by the step-height measurement. The surface morphology and the roughness of the spinel were not very dependent on dose rate. The results of c-SiO2 and a-SiO2 indicate that both of them are subjected to enhanced changes in surface morphology and microstructures and that high-current implantation causes highly dynamic states in the near-surface region. On the other hand, the results for the spinel show pronounced stability and that the spinel may be used as an effective substrate for optical modification, even for high-current ion implantation.

High current metal-ion implantation to fabricate metal silicides

Using a metal vapor vacuum arc (MEVVA) ion source, metallic silicides, such as C54-TiSi 2, NiSi 2, COSi 2, NbSi 2 and TaSi 2, etc., with good electrical properties were obtained directly on Si wafers by high current metal-ion implantation with neither in situ heating nor post-annealing. Semiconducting silicides, such as β-FeSi 2 and CrSi 2, were also directly formed on Si wafers by MEVVA ion implantation with unique physical properties. The growth mechanism of the metal silicides is also discussed for Ni–Si as a representative system.