Aluminum Ion Implantation Research Articles

A Multiscale Simulation on Aluminum Ion Implantation-Induced Defects in 4H-SiC MOSFETs

Aluminum (Al) ion implantation is one of the most important technologies in SiC device manufacturing processes due to its ability to produce the p-type doping effect, which is essential to building p–n junctions and blocking high voltages. However, besides the doping effect, defects are also probably induced by the implantation. Here, the impacts of Al ion implantation-induced defects on 4H-SiC MOSFET channel transport behaviors are studied using a multiscale simulation flow, including the molecular dynamics (MD) simulation, density functional theory (DFT) calculation, and tight-binding (TB) model-based quantum transport simulation. The simulation results show that an Al ion can not only replace a Si lattice site to realize the p-doping effect, but it can also replace the C lattice site to induce mid-gap trap levels or become an interstitial to induce the n-doping effect. Moreover, the implantation tends to bring additional point defects to the 4H-SiC body region near the Al ions, which will lead to more complicated coupling effects between them, such as degrading the p-type doping effect by trapping free hole carriers and inducing new trap states at the 4H-SiC bandgap. The quantum transport simulations indicate that these coupling effects will impede local electron transports, compensating for the doping effect and increasing the leakage current of the 4H-SiC MOSFET. In this study, the complicated coupling effects between the implanted Al ions and the implantation-induced point defects are revealed, which provides new references for experiments to increase the accepter activation rate and restrain the defect effect in SiC devices.

Effect of the column design and fabrication method on the reverse recovery characteristics of 1.2 kV SiC-superjunction-MOSFETs

We investigated the effects of the column length and fabrication method of the superjunction (SJ) structure on the reverse recovery characteristics of 1.2 kV silicon carbide (SiC) SJ metal–oxide–semiconductor field-effect transistors (MOSFETs). The voltage slope (dV/dt) and reverse recovery current slope (dir/dt) values during the reverse recovery of the SJ-MOSFETs with the SJ structure formed by Aluminum (Al) ion implantation were comparable to the values of MOSFETs without SJ structure at room temperature (RT), but they increased markedly with temperature. This is caused by the reduced p-column carrier concentration at RT during short recovery transient time due to the deep hole trap (DI center) introduced by ion implantation. At 175 °C, a softer reverse recovery waveform was obtained by shortening the SJ columns. Besides, Al ion implanted SJ-MOSFETs exhibited a weaker current dependence of the reverse recovery charge Qrr at 175 °C indicating a lower carrier injection level compared to the SJ-MOSFETs with the SJ structure formed by trench formation and epitaxial growth. This is caused by the short carrier lifetime of the SJ columns due to the Al ion implantation defects. The short and Al ion implanted SJ columns are effective for soft reverse recovery characteristics in SiC-SJ-MOSFETs.

Aluminium Ion Implantation in Stainless Steel

Aluminium Ion Implantation in Stainless Steel

Study of the synergy effect of high-intensity aluminum ions implantation into titanium and energy impact on the surface

The work studies the synergy effect of high-intensity implantation of aluminum ions and thesubsequent impact of a powerful pulsed ion beam on the microstructure and properties of titanium.Specimens of titanium were implanted for one hour at a temperature of 1170 K with an ion fluenceof 1021 ions/cm2. Layers with a thickness of about 150 μm were obtained. The energy impact wascarried out by a powerful nanosecond pulsed ion beam with an ion current density on the targetof 100 A/cm2. The paper presents data on changes in the elemental composition, surface morphology,and microstructure of ion-doped and energy-modified layers. It has been established that the additionalenergy impact on the ion-doped layer of a powerful pulsed beam improves microstructure at depthsgreater than 3.4 μm. The synergistic of high-intensity ion implantation of aluminum and the energyimpact of a pulsed ion beam improves the wear resistance of titanium by eighteen folds.

Study of the influence of a powerful pulsed ion beam on titanium deeply-doped with aluminum

The work studies the synergy effect of high-intensity implantation of aluminum ions and the subsequent impact of a powerful pulsed ion beam on the microstructure and properties of titanium. Specimens of titanium were implanted for 1 h at a temperature of 1170 K with an ion fluence of 1021 ions/cm2. Layers with a thickness of about 150 μm were obtained. The energy impact was carried out by a powerful nanosecond pulsed ion beams with an ion current density on the target of 100 A/cm2. The paper presents data on changes in the elemental composition, and microstructure of ion-doped and energy-modified layers. It has been established that the additional energy impact on the ion-doped layer of a powerful pulsed beam improves microstructure at depths of about 4.31 μm. The synergistic of high-intensity ion implantation of aluminum and the energy impact of a pulsed ion beam improves the wear resistance of titanium by eighteen folds.

The Effect of Aluminum Ion Implantation on the Physical and Mechanical Properties of the Surface Layers of Stainless Steel AISI 321

The Effect of Aluminum Ion Implantation on the Physical and Mechanical Properties of the Surface Layers of Stainless Steel AISI 321

Cathodoluminescence Characterization of Point Defects Generated through Ion Implantations in 4H-SiC

The high quality of crystal growth and advanced fabrication technology of silicon carbide (SiC) in power electronics enables the control of optically active defects in SiC, such as silicon vacancies (VSi). In this paper, VSi are generated in hexagonal SiC (4H) samples through ion implantation of nitrogen or (and) aluminum, respectively the n- and p-type dopants for SiC. The presence of silicon vacancies within the samples is studied using cathodoluminescence at 80K. For 4H-SiC samples, the ZPL (zero phonon line) of the V1′ center of VSi is more intense than the one for the V1 center before annealing. The opposite is true after 900 °C annealing. ZPLs of the divacancy defect (VCVSi) are also visible after annealing.

Ion implantation and activation of aluminum in bulk 3C-SiC and 3C-SiC on Si

Ion implantation and activation of aluminum in bulk 3C-SiC and 3C-SiC on Si

Investigation of source materials, co-gases, and methods for aluminum ion implantation

Investigation of source materials, co-gases, and methods for aluminum ion implantation

An Efficient 4H-SiC Photodiode for UV Sensing Applications

In this paper, we report experimental findings on a 4H-SiC-based p-i-n photodiode. The fabricated device has a p-type region formed by ion-implantation of aluminum (Al) in a nitrogen doped n-type layer. The dark reverse current density reaches 38.6 nA/cm2 at −10 V, while the photocurrent density rises to 6.36 µA/cm2 at the same bias under λ = 315 nm ultraviolet (UV) radiation with an incident optical power density of 29.83 μW/cm2. At the wavelength of λ = 285 nm, the responsivity is maximum, 0.168 A/W at 0 V, and 0.204 A/W at −30 V, leading to an external quantum efficiency of 72.7 and 88.3%, respectively. Moreover, the long-term stability of the photodiode performances has been examined after exposing the device under test to several cycles of thermal stress, from 150 up to 350 °C and vice versa. The achieved results prove that the examined high-efficiency UV photodiode also has a stable responsivity if subjected to high temperature variations. The proposed device is fully compatible with the conventional production process of 4H-SiC components.

Influence of the aluminum ion implantation dose on the phase composition of submicrocrystalline titanium

We report the study of commercially pure titanium (VТ1-0 alloy under Russian classification) in the submicrocrystalline state obtained by the abc-pressing method with the surface modified by the ion implantation technique. Ion implantation was performed using aluminum ions at irradiation doses 1 × 1017, 5 × 1017, and 10 × 1017 ion/cm2 using a MEVVA5.RU source. The grain longitudinal and transverse dimensions were determined before and after ion implantation for varying irradiation doses. We studied the influence of ion implantation and the irradiation dose on the elemental and phase composition of the surface layers of VT1-0 alloy. It has been found that ion implantation results in restructuring of titanium surface layers and in a change of the grain size with the depth of the surface layers. For example, the grain longitudinal size decreases 5 times at the dose rate of 1·1017 ion/cm2. It has been found that aluminum ion implantation modifies the surface layers containing intermetallic phases of TiAl3, Ti3Al, and aluminum and titanium oxides (Al2O3, TiO2, TiO и Ti2O3). Increasing the irradiation dose does not qualitatively change the alloy phase composition, but affects the quantitative characteristics of the formed secondary phases.

Prominent luminescence of silicon-vacancy defects created in bulk silicon carbide p\u2013n junction diodes

We investigate fluorescent defect centers in 4H silicon carbide p–n junction diodes fabricated via aluminum-ion implantation into an n-type bulk substrate without the use of an epitaxial growth process. At room temperature, electron-irradiated p–n junction diodes exhibit electroluminescence originating from silicon-vacancy defects. For a diode exposed to an electron dose of 1 times 10^{18},{{mathrm{cm}}}^{-2} at 800,{{mathrm{keV}}}, the electroluminescence intensity of these defects is most prominent within a wavelength range of 400–1100,{{mathrm{nm}}}. The commonly observed {{mathrm{D}}}_1 emission was sufficiently suppressed in the electroluminescence spectra of all the fabricated diodes, while it was detected in the photoluminescence measurements. The photoluminescence spectra also displayed emission lines from silicon-vacancy defects.

Growth of 4H-SiC recombination-enhancing buffer layer with Ti and N co-doping and improvement of forward voltage stability of PiN diodes

“Bipolar degradation” phenomenon has severely impeded the development of 4H-SiC bipolar devices. Their defect mechanism is the expansion of Shockley-type stacking faults from basal plane dislocations under the condition of electron-hole recombination. To suppress the “bipolar degradation” phenomenon, not only do the basal plane dislocations in the 4H-SiC drift layer need eliminating, but also a recombination-enhancing buffer layer is required to prevent the minority carriers of holes from reaching the epilayer/substrate interface where high-density basal plane dislocation segments exist. In this paper, Ti and N co-doped 4H-SiC buffer layers are grown to further shorten the minority carrier lifetime. Firstly, the dependence of Ti doping concentration on TiCl<sub>4</sub> flow rate in 4H-SiC epilayers is determined by using single-dilution gas line and double-dilution gas line. Then the p<sup>+</sup> layer and p<sup>++</sup> layer in PiN diode are obtained by aluminum ion implantation at room temperature and 500 ℃ followed by high temperature activation annealing. Finally, 4H-SiC PiN diodes with a Ti, N co-doped buffer layer are fabricated and tested with a forward current density of 100 A/cm<sup>2</sup> for 10 min. Comparing with the PiN diodes without a buffer layer and with a buffer layer only doped with high concentration of nitrogen, the forward voltage drop stability of those diodes with a 2 μm-thick Ti, N co-doped buffer layer (Ti: 3.70 × 10<sup>15</sup> cm<sup>–3</sup> and N: 1.01 × 10<sup>19</sup> cm<sup>–3</sup>) is greatly improved.

Ion implantation of aluminum in 4H-SiC epilayers from 90 keV to above 1 MeV

The depth profiles of aluminum (Al) ion implantation on 4H-SiC epilayers with implantation energy range from 90 keV to above 1 MeV have been studied. The SIMS profiles show that the channeling effect is significantly reduced as the energy increases. This is attributed to the dechanneling effects due to the introduction of interstitial type defects created by preceding implanting ions under high-implantion energy and high-dose level conditions. We compare experimental data with simulation results based on SRIM™ program and Sentaurus™ Monte Carlo (MC) model. The SRIM simulation shows good agreement with the experimental profiles around the projected range, but could not reproduce the channeling tails of the profiles. The calibrated sentaurus MC model can show good agreement with the experimental profiles of projected range and channeling. The effect of tilt angle and implantation temperature on the channeling in the calibrated sentaurus MC model is also studied.

The effect of aluminum ion implantation on the grain size and structure of UFG titanium

Using the transmission electron microscopy technique, we have studied the structural-phase state of UFG titanium with an average grain size ~0.2 μm implanted with aluminum ions. An MEVVA-V.RU source has been used to implant the specimen at room temperature, implantation time 5.25 h, and irradiation dose 1 · 1018 ion/cm2. To produce the UFG titanium samples, we have employed the combined multiple uniaxial pressing technique (abc-pressing) followed by grooved rolling and subsequent annealing at 573 K for 1 h. The samples have been studied in two states: 1) before implantation (initial state) and 2) after implantation at a distance 70–100 nm from the sample surface. We have obtained the aluminum concentration profile of implanted α-Ti. It has been established that the maximum concentration of aluminum is 70 at.% and the thickness of the implanted layer is 200 nm. We have determined the grain distribution functions over the grain size, calculated the grain anisotropy coefficient before and after implantation. It has been established that implantation decreases the average longitudinal and transversal sizes of α-Ti grains, and reduces the anisotropy coefficient by three times. It has been established that aluminum implantation into titanium brings about formation of a whole set of phases with different crystal lattices, namely, β-Ti, TiAl3, Ti3Al, TiC, and TiO2.

Improving the performance properties of titanium alloy VT6 after ion implantation with copper and aluminum ions

The objective of this work was to study the processes occurring on the surface of VT6 titanium alloy samples when implanting with copper and aluminum ions. Elemental composition, structural-phase state, mechanical and tribological properties of VT6 titanium alloy surface layers modified by aluminum and copper ions was being researched. As can be seen from the undertaken studies, the mode of high-intensity ion-implantation process makes it possible to obtain ion doped surface layers of VT6 alloy containing finely dispersed intermetallic phases and a solid solution of aluminum and copper in titanium of a composition varying in depth. The thickness of the ion-doped layer, the average grain size of the intermetallic phases and their conglomerates increases with the increase in implantation dose while aluminum implantation is in progress. It has been shown that the implantation of aluminum and copper ions into VT6 alloy leads to a considerable increase in its microhardness and wearability. Based on the research results, a conclusion on the positive effect of a structural-phase state of ion-doped titanium layers on their mechanical and tribological properties of VT6 titanium alloy has been drawn.

P-type doping of Ge by Al ion implantation and pulsed laser melting

Germanium recently attracted a renewed interest for its potential applications in several fields such as nanoelectronics, photonics, plasmonics, etc., but well-known issues about doping at high concentration and controlling impurity profiles prevent its integration in technology. To this purpose, p-type doping aluminum ion implantation followed by pulsed laser annealing in the melting regime has been investigated for the first time. In particular, two different regimes have been studied, in order to explore the limit of incorporation for such a method: 6.4 × 1014 Al/cm2 and 4.2 × 1015 Al/cm2, both at 25 keV, corresponding to concentrations below and above the solid solubility, respectively. We found that in the former case, oxygen contamination precludes full activation (<60%), as suggested by Raman characterizations. Besides, secondary ion mass spectrometry evidences pronounced out-diffusion and pile-up of the dopant near the surface. In the letter case, remarkable (~1 × 1020 Al/cm3), although partial (~30%), electrical activation is obtained, independently on O occurrence. Therefore, O-Al and Al-Al clustering are proposed as concurrent mechanisms, limiting full activation at high implanted dose. Nevertheless, the samples display good crystalline quality and, surprisingly, a significant thermal stability (up to 600° C).

(Invited) Al+ Ion Implanted 4H-SiC: Electrical Activation versus Annealing Time

The selected area doping by ion implantation is often used in the fabrication of 4H-SiC electronic devices; DMOSFETs and JTE are here cited as examples. In the ion implantation technology, the key parameters are: implantation temperature, dose rate per ion energy, ion implanted dopant depth profile, post implantation annealing temperature, and post implantation annealing time. In the case of 4H-SiC, the most of the litterature focus on finding the post implantation annealing parameters that maximize the doping efficiency per ion implanted dopant concentration, or, that give the sufficient electrical activation for obtaining the desired device performance. This results in a multitude of reported electrical data, taken in heterogeneous samples. Recently, an empirical model for previewing the electrical activation per ion implanted dopant species versus dopant concentration has been proposed [1] on the base of published data. This model [1] could be a useful tool for sufficiently reliable device designs. Nevertheless, recent results on the electrical activation of ion implanted P and Al in 4H-SiC [2-3] show that the data trends used in [1] may require adjustments. Moreover, a full description of the thermodynamics controlling the phenomenon of the electrical activation of ion implanted dopants in 4H-SiC, should require dedicated experiments; examples of which can be found in [4-5]. It is relevant to cite the fact that the results of [4] allowed the authors to perform realistic previsions about the electrical trasport in Al ion implanted 4H-SiC after post implantation annealing at a temperature and for times never explored before, as shown in [6]. The present work will resumes the latest results on the electrical activation of aluminum [2] and phosphorous [3] ion implanted in 4H-SiC with typical concentration values for n-channel DMOSFETs. These values are in the range 3×1018 - 1×1019 cm-3. Post implantation annealing temperature is relative low: 1600 °C. This is a conservative value for minimizing step bunching formation at the oxide/semicondutor interface in the channel region. The annealing time ranges from 5 min to 15 h. The temperature dependence of resistivity and Hall coefficent is measured in the range 70-640 K. Experimental data are analysed to extract donor and acceptor concentration, dopant compensation, and carrier mobility. For comparison purposes, both published and original results obtained for identical ion implanted dopant species and similar ion implanted dopant concentration in high purity semi insulating (HPSI) 4H-SiC, but higher post implantation annelaing temperature, will be shown too. The aim of this work is to produce results that help in featuring the balance between electrical activation and compensation as far as the annealing time increases at a fixed annealing temperature. The DMOSFETs doping configuration has been chosen because timely. [1] V. Simonka et al., "Transient model for the electrical activation of aluminium and phosphorous-implanted silicon carbide", J. Appl. Phys. 123, 235701 (2018). [2] R. Nipoti et al., "Low concentration Aluminum ion implantation in 4H-SiC", submitted to ICSCRM2019, Tokyo, Sept. 29 - Oct. 4, 2019. [3] A. Parisini et al., "Phosphorous doping by ion implantation in 4H-SiC DMOSFETs", submitted to ICSCRM2019, Tokyo, Sept. 29 - Oct. 4, 2019. [4] R. Nipoti et al. "About the Electrical Activation of 1×1020 cm-3 Ion Implanted Al in 4H-SiC at Annealing Temperatures in the Range 1500 - 1950°C", Mater. Sc. Forum, 924, 333-338 (2018). [5] R. Nipoti et al., "Activation energy for the post implantation annealing of 1019 cm-3 and 1020 cm-3 ion implanted Al in 4H SiC.", proceedings of ECSCRM2018, Birmingham, accepted for publication in Mater. Sc. Forum on Jan. 29, 2019. [6] R. Nipoti et al., "1300°C Annealing of 1×1020 Al+ Ion Implanted 3C-SiC", proceedings of ECSCRM2018, Birmingham, accepted for publication in Mater. Sc. Forum on Jan. 29, 2019.

VT6 TITANIUM ALLOY WEARABILITY INCREASE VIA IMPLANTATION OF COPPER AND ALUMINUM IONS

The relevance of the article is due to the fact that the use of titanium alloys within friction joints is restrained by their low resistance to wear while traditional methods of increasing their wear resistance are ineffective. The objective of this work was to study the processes occurring on the surface of VT6 titanium alloy samples when implanting with copper and aluminum ions, as well as in friction. Elemental composition, structural-phase state, mechanical and tribological properties of VT6 titanium alloy surface layers modified by aluminum and copper ions during the high-intensity ion-implantation process was being researched. As can be seen from the undertaken studies, the mode of the high-intensity ion-implantation process makes it possible to obtain ion doped surface layers of VT6 alloy containing TiAl, Ti3Al, Ti3Cu, Ti2Cu, TiCu finely dispersed intermetallic phases and a solid solution of aluminum and copper in titanium of composition varying in depth. The thickness of the ion-doped layer, the average grain size of the intermetallic phases (from 18 to 55nm) and their conglomerates (from 45 to 280 nm) increases with the increase in implantation dose from 2⋅1017 to 1.2⋅1019 ion/cm2 while aluminum implantation (from 0.42 to 2.1 μm) is in progress. It has been shown that the implantation of aluminum and copper ions into VT6 alloy leads to a considerable increase in its microhardness and wearability. Based on the research results, a conclusion on the positive effect of a structural-phase state of ion-doped titanium layers on their mechanical and tribological properties of VT6 titanium alloy has been drawn.

Selection of ion species suited for channeled implantation to be used in multi-epitaxial growth for SiC superjunction devices

Discrepancies in reported electronic stopping cross sections and simulated concentration-depth profiles in 4H-SiC for low-velocity ions have made it difficult to select ion species suited for channeled implantation to be used in multi-epitaxial growth for superjunction devices. In this study, a parallel-scanning system was used to vertically implant 9 × 107-cm s−1 ions into a nominal (0001) wafer at RT. Among the possible channeled implantations of nitrogen or phosphorus ions into p-type 4H-SiC and boron or aluminum ions into n-type 4H-SiC, aluminum-ion implantation into n-type 4H-SiC was concluded to be the best for minimizing repetition of the epitaxial growth/ion implantation steps.