Temperature Ion Implantation Research Articles

The Process and Mechanism of Preparing Nanoporous Silicon: Helium Ion Implantation.

Ion implantation is an effective way to control performance in semiconductor technology. In this paper, the fabrication of 1~5 nm porous silicon by helium ion implantation was systemically studied, and the growth mechanism and regulation mechanism of helium bubbles in monocrystalline silicon at low temperatures were revealed. In this work, 100 keV He ions (1~7.5 × 1016 ions/cm2) were implanted into monocrystalline silicon at 115 °C~220 °C. There were three distinct stages in the growth of helium bubbles, showing different mechanisms of helium bubble formation. The minimum average diameter of a helium bubble is approximately 2.3 nm, and the maximum number density of the helium bubble is 4.2 × 1023 m-3 at 175 °C. The porous structure may not be obtained at injection temperatures below 115 °C or injection doses below 2.5 × 1016 ions/cm2. In the process, both the ion implantation temperature and ion implantation dose affect the growth of helium bubbles in monocrystalline silicon. Our findings suggest an effective approach to the fabrication of 1~5 nm nanoporous silicon, challenging the classic view of the relationship between process temperature or dose and pore size of porous silicon, and some new theories are summarized.

(Digital Presentation) Substrate Effects in GaN-on-Si Hemt Technology for RF FEM Applications

: GaN-on-Si HEMTs are emerging as a viable candidate for front-end-of-module (FEM) implementation in 5G and beyond user equipment and small-cell applications [1][2]. This is because GaN HEMTs based power amplifiers and switches have high power handling capability as well as excellent switch figure-of-merit (Ron × Coff). The cost-effective integration of GaN HEMTs on silicon substrates not only benefit from standard CMOS back-end-of-the-line processing but also wafer-level integration with Si-CMOS [1][3], enabling complex functionality and better performance than the standalone counterparts. An example can be a hybrid beamformer where GaN HEMTs can enable much smaller antenna array and therefore a smaller system form factor. For 5G wireless applications, standalone or co-integrated GaN HEMT based FEMs can lead to a more energy efficient and compact system as compared to standalone Si-CMOS technologies. However, for both amplifiers and switches, GaN-on-Si HEMTs present thermal management and substrate loss related issues. In this work, we study and model the impact of GaN HEMT integration on Si substrate on RF substrate losses and non-linearities. The growth of III-N buffer is the most significant factor in determining RF losses and harmonic distortion contribution from the substrate. High temperature annealing and ion implantation steps encountered during HEMT processing can also degrade the substrate performance. In addition, we demonstrate a direct co-relation between substrate losses and harmonic distortion analogous to silicon-on-insulator technologies (Figure 1). However, the bias dependence of RF losses and harmonics show a strong time dependence (memory effects) which is more complex to model [11]. We discuss the approaches to understand and model these effects.

Microstructural Evolution and the Irradiation Sensitivity of Different Phases of a High Nb-Containing TiAl Alloy under He Ions Implantation at Room- and Elevated Temperatures

A high Nb-containing TiAl alloy Ti-45Al-8.5Nb-(W, B, Y) with nearly lamellar microstructure has been irradiated by 200 kV He2+ to a fluence of 1 × 1021 ions/m2 with a dose of about 1.1 dpa at 298 K and 773 K in this work. It is found that an amorphous layer formed on the surface, and no helium bubbles can be observed in the alloy after room temperature ion implantation. The surface roughness of the alloy increases significantly with the bombardment of helium ions, indicating that the ion implantation increases the surface defects. The high-temperature ion implantation leads to the phenomenon of blistering on the alloy surface, and helium bubbles are observed in both α2 and γ phases of the alloy irradiated at 773 K. The average size of the helium bubbles in the α2 (15~20nm) is larger than that in the γ (3~5 nm) phase, while the helium bubble density is opposite. Moreover, the growth mechanism of helium bubble is also investigated. By means of nanoindentation, an obvious irradiation hardening phenomenon is measured after the room temperature ion implantation. In addition, the irradiation sensitivity of different phases is also discussed in this work. The results show that the γ phase has the highest irradiation sensitivity, α2 phase second, β phase minimum. The results of this work, especially microstructure evolution and the evaluation of phase-related irradiation sensitivity during ion implantation, can be expected to provide experimental evidence for the applications of TiAl intermetallic compounds in the nuclear industries.

Angular rotation ion implantation technology in SiC for 4H-SiC junction barrier Schottky rectifiers

• This study proposes an angular rotation ion implantation technology. • This technology could improve the rate of finished product products to be 90%. • With the angle rotation technology, the production cost will be saved effectively. SiC is widely used for making high level power electronic devices due to its excellent properties. SiC Junction Barrier Schottky (JBS) diodes have a low reverse leakage current and could offer fast switching and the Schottky-like on-state characteristics. High temperature ion implantation has been an essential process for the mainly doping formation SiC power electronic devices. In this work, the angular rotation ion implantation technology in SiC JBS has been investigated. The distribution of the injected elements has also been simulated, and the calculated results fitted well with the experimental results. With this angular rotation technology the power loss of the SiC JBS diodes have been reduced, effectively. And the rate of finished product was turned out to be as high as 90%. This method can greatly reduce the process flow, reduce the damage to the wafer and save production cost, which has great significance in quantity production.

Activation Energy for the Post Implantation Annealing of 10<sup>19</sup> cm<sup>-3</sup> and 10<sup>20 </sup>cm<sup>-3</sup> Ion Implanted Al in 4H SiC

The activation energy for the electrical activation of 1x1019 cm-3 and of 1x1020 cm-3 ion implanted Al in 4H-SiC has been estimated. Ion implantation temperature and dose rate were in the range 430-500°C and around 1011 cm2s-1, respectively. Post implantation annealing temperatures varied between 1500 °C and 1950 °C. The annealing time per each annealing temperature was sufficiently long that the sheet resistance of the implanted layer could be equal to the stationary value at the applied annealing temperature. The Arrhenius plots of the room temperature sheet resistances with respect to the post implantation annealing temperatures featured an exponential trend for both the implanted Al concentrations. The activation energies of these plots are the activation energy for placing an implanted Al atom in a substitutional site, i.e. the electrical activation energy. Activation energies around 1 eV, equal within errors for the two implanted Al concentrations, were found.

SiC nano-dot formation in bulk-Si substrate using hot-C+-ion implantation process

We experimentally studied SiC nano-dot formation in a bulk-Si substrate fabricated by the very simple processes of a hot-C+-ion implantation into (100) bulk-Si substrate and the following N2-annealing, and the photoluminescence (PL) properties for a future Si-based photonic device. We confirmed by a transmission electron microscope that cubic and hexagonal SiC dots are formed in a C+-ion implanted Si layer, and the SiC dot diameter (3–7 nm) and density (1–2 × 1012 cm−2) depend on the process conditions. We also observed very strong PL-intensity after N2-annealing, and the broad PL spectrum can be fitted by the sum of the PL-emissions from four different cubic and hexagonal SiC-polytypes with different exciton bandgaps. The PL-properties strongly depend on the N2-annealing temperature, and hot-C+-ion implantation temperature and dose. Consequently, we successfully optimize the process conditions to improve PL-intensity, as well as to control the PL-spectrum line shape in the near-UV/visible regions.

The Influence of High-Energy Krypton Ion Implantation Temperature on Structure and Properties of Ni–Ti Alloy

The influence of the temperature of implantation of Ni–Ti shape memory alloy with 84Kr15+ions at the energy E = 147 MeV on its structural-phase state is investigated. At the implantation temperatures 250 and 300°С, within the projective range Rp and out-range area the following processes and phenomena are observed: new formation of the martensitic В19'-phase, formation of nano-sized particles of the R-phase, increase in resistivity due to the formation of radiation-defect structures, strengthening of the alloy in the austenitic structural-phase state, and longer phase-transition temperature intervals.

Improvement in drain-induced-barrier-lowering and on-state current characteristics of bulk Si fin field-effect-transistors using high temperature Phosphorus extension ion implantation

In this paper, high temperature Phosphorus ion implantation is applied to p-type Si (1 0 0) substrates and n-type bulk Si fin field-effect-transistors. Phosphorus profiles and sheet resistance on p-type Si (1 0 0) substrates are analyzed. High temperature ion implantation shows less Phosphorus diffusion after rapid thermal annealing compared to room temperature ion implantation. In n-type bulk Si fin field-effect-transistors with wide spacers and ion implanted source and drain, the high temperature extension ion implantation shows better electrical characteristics in terms of drain-induced-barrier-lowering, on-state resistance, on-state current, and off-state current. In n-type bulk Si fin field-effect-transistors with narrow spacers and Phosphorus in-situ doped Si epi source and drain, drain-induced-barrier-lowering and off-state current characteristics are improved by high temperature extension ion implantation, compared to room temperature extension ion implantation. Phosphorus distribution in fin field-effect-transistors is analyzed by scanning spreading resistance microscopy. Suppression of Phosphorus diffusion into the channel area is confirmed.

Preparation of new photocatalytic materials using ion implantation method

The materials containing titanium supported on stainless steel foil 12X18N10T (AISI 321) were prepared by low temperature ion implantation method. Samples were investigated by means of XRD, SAXS, AFM, XPS and SEM methods. Any reflexes of titanium compounds were determined (XRD) but XPS data permit to identify the presence of titanium nitride, its oxide and oxynitride on surface samples. It was shown, that the synthesized samples are more active in visible range than under UV irradiation in photodegradation of benzene in aqueous solutions. Influence of pretreatment temperature on photoactivity of the samples is connected with nitrogen removal from synthesized composites.

Effect of Ion Implantation-Induced Defects on Leakage Current Characteristics of IEMOS

We investigated the relationship between ion implantation-induced defects and electrical characteristics, especially focusing on the leak failure rate in SiC IEMOSs and PN diodes. It was found that dislocation exists in each leakage point by analyzing identical leak-failed IEMOS by emission microscopy and refraction X-ray topography. The leak failure rate of the PN diodes and IEMOS was improved with an increase in the ion implantation temperature under the implantation and annealing conditions used in this experiment. It is considered that ion implantation-induced defects lead to an increase in leak failure rates, and also enable a decrease in leak failure rates by raising the implantation temperature up to 600 deg.C.

Nano-SiC region formation in (100) Si-on-insulator substrate: Optimization of hot-C+-ion implantation process to improve photoluminescence intensity

We experimentally studied the optimization of the hot-C+-ion implantation process for forming nano-SiC (silicon carbide) regions in a (100) Si-on-insulator substrate at various hot-C+-ion implantation temperatures and C+ ion doses to improve photoluminescence (PL) intensity for future Si-based photonic devices. We successfully optimized the process by hot-C+-ion implantation at a temperature of about 700 °C and a C+ ion dose of approximately 4 × 1016 cm−2 to realize a high intensity of PL emitted from an approximately 1.5-nm-thick C atom segregation layer near the surface-oxide/Si interface. Moreover, atom probe tomography showed that implanted C atoms cluster in the Si layer and near the oxide/Si interface; thus, the C content locally condenses even in the C atom segregation layer, which leads to SiC formation. Corrector-spherical aberration transmission electron microscopy also showed that both 4H-SiC and 3C-SiC nanoareas near both the surface-oxide/Si and buried-oxide/Si interfaces partially grow into the oxide layer, and the observed PL photons are mainly emitted from the surface SiC nano areas.

Reduced Junction Leakage by Hot Phosphorus Ion Implantation of NiGe-Contacted Germanium n+/p Shallow Junction

Effects of hot phosphorus (P) implantation on the NiGe-contacted Ge n+/p junction are studied in this work. At an adequately high ion-implantation temperature (150°C), the P depth profiles of the hot-implanted samples are similar to that of the room-temperature implanted ones. Hot P implantation is demonstrated effectively in reducing ion implantation induced defect formation and suppressing nickel atoms diffusion. Therefore, hot P implantation is efficient in lowering junction leakage and excellent junction characteristics exhibiting $\sim 1\times 10^{6}~{J}_{ \mathrm{\scriptscriptstyle ON}}/{J}_{ \mathrm{\scriptscriptstyle OFF}}$ ratio is achieved.

Formation of D-Center in p-Type 4H-SiC Epi-Layers during High Temperature Treatments

The current work is devoted to studying the evolution of deep level defects in the lower half of the 4H-SiC bandgap after high temperature processing and ion implantation. Two as-grown and pre-oxidized 4H-SiC sets of samples have been thermally treated at temperatures up to 1950 °C for 10 min duration using RF inductive heating. Another set of as grown samples was implanted by 4.2 MeV Si ions at room temperature (RT) with different doses (1-4×108 cm-2). The so-called “D-center” at EV+0.6 eV dominates and forms after the elevated heat treatments, while it shows no change after the ion implantations (EV denotes the valence band edge). In contrast, the concentration of the so-called HK4 level at EV+1.44 eV increases with the implantation dose, whereas it anneals out after heat treatment at ≥ 1700 °C.

Experimental study of mechanical and tribological behavior of nitrogen ion-implanted chromium thin films

Pure chromium coatings can act as decorative or corrosion-resistant coating, but they present poor tribological properties. Even electroplated hard chrome coatings present some problems, as micro-cracks that reduce their corrosion protection and induce fatigue failure. In addition, Cr plating and its dangerous process with Cr VI baths has been banished in several countries. Physical or chemical post-coating treatments can be applied onto coatings in order to enhance their surface properties, as high temperature oxidation, chemical baths or ion implantation. Plasma immersion ion implantation process was carried on PVD chromium coatings as a post-coating treatment and nitrogen ions were implanted on the surface of deposited chromium thin films, by means of two different plasma sources for ion implantation. Both configurations for plasma sources led to the formation of nitride compounds on the surface of the films. The treated films presented low coefficient of friction, high hardness and better adhesion when compared to the untreated film.

Ion beam synthesis of ZrCxOy nanoparticles in cubic zirconia

{110}-oriented yttria-stabilized zirconia single crystals have been implanted with low-energy C ions in an axial direction, at room temperature and at 550 °C. Room temperature ion implantation generated a damage layer that contains the expected dislocation loop clusters. Strikingly, the high temperature implantation produced zirconium oxycarbide nanoparticles (ZrCxOy) at a shallow depth in the yttria-stabilized cubic zirconia crystal, with a diameter in the range of 4–10 nm. Moreover, in the high concentration region of implanted C ions, between 100 and 150 nm below the surface, a number of large precipitates, up to 20 nm, were observed.

Silicon defects characterization for low temperature ion implantation and RTA process

In the last years a lot of effort has been directed in order to reduce silicon defects eventually formed during the ion implantation/anneal sequence used in the fabrication of CMOS devices. In this work we explored the effect of ion implant dose rate and temperature on the formation of silicon defects for high fluence 49BF2 implantations. The considered processes (implantation and annealing) conditions are those typically used to form the source/drain regions of p-channel transistors in the submicron technology node and will be detailed in the document. Characterization of implant damage and extended silicon defects left after anneal has been performed by TEM. Dopant distribution and dopant activation has been investigated by SIMS and SRP analysis. We have verified that implant dose rate and temperature modulate the thickness of the amorphous silicon observed after implant, as well as the concentrations of silicon defects left after anneal. Effect of high dose rate low temperature implantation on product device was also evaluated, showing a reduction of leakage current on p-channel transistors. Experimental set up, results and possible explanation will be reported and discussed in the paper.

Carbon redistribution and precipitation in high temperature ion-implanted strained Si/SiGe/Si multi-layered structures

We report on the segregation of carbon atoms and structural transformations in strained multilayered Si/SiGe/Si structures after molecular-beam epitaxial (MBE) growth, carbon ion implantation and thermal treatment at different conditions. The idea behind this study was that due to their specific strain distribution, pseudomorphic layers of Si/SiGe promote spatial separation of vacancies and interstitials followed by segregation of foreign dopant atoms. High temperature ion implantation was used for injection of carbon atoms as well as point defects in the strained layers. The defects were investigated by transmission electron microscopy (TEM), dopant depth profiles by secondary-ion-mass spectrometry (SIMS), and optical properties by Raman scattering measurements. Based on SIMS data we demonstrate anomalous redistribution of the implanted carbon atoms around the strained SiGe/Si layers which results in their accumulation on the Si side and depletion on the SiGe side of the structure. The TEM study demonstrates formation of plate-like defects, stacking faults and thin carbon-precipitated flakes distributed along the Si/SiGe interfaces. Raman spectra reveal peaks at 1600 and 2700cm−1 which might be associated with carbon-related phases. The concept of strain-enhanced separation of point defects and dopant precipitation is discussed.

Nanocrystal- and Dislocation-Related Luminescence in Si Matrix with InAs Nanocrystals

We have studied the influence of ion implantation and post-implantation annealing regimes on the structural and optical properties of silicon matrix with ion-beam synthesized InAs nanocrystals. (100) Si wafers were implanted at 25 and 500 ◦C, subsequently with high fluences of As and In ions. After implantation the samples were processed by furnace and rapid thermal annealing at 900, 950 and 1050 ◦C. A part of the samples implanted at 25 ◦C was additionally exposed to H+2 ions (100 keV, 1.2 × 10 cm−2 in terms of atomic hydrogen). This procedure was performed to obtain an internal getter. In order to characterize the implanted samples transmission electron microscopy and low-temperature photoluminescence techniques were employed. It was demonstrated that by introducing getter, varying the ion implantation temperature, ion fluences and post-implantation annealing duration, and temperature it is possible to form InAs nanocrystals in the range of sizes of 2–80 nm and create various concentration and distribution of different types of secondary defects. The last ones cause in turn the appearance in photoluminescence spectra dislocation-related D1, D2 and D4 lines at 0.807, 0.870 and 0.997 eV, respectively.

Ion implantation techniques for non-electronic applications

Ion implantation techniques have been used to improve surface properties for over more than four decades. Metallurgical application of ion beam techniques was first reported in the 70s by Harwell laboratory (UK), and by the Naval Research Laboratory (USA), mainly focused to nitrogen implantation of steels. From those first results to today ion implantation techniques have been introduced in many different applications for industrial sectors such as the aeronautical and biomedical. This paper presents some of the most important actual applications of ion implantation techniques. Different strategies of conventional Ion Implantation (II), Low energy-High Temperature Ion Implantation (LEHT), and Plasma Immersion Ion Implantation (PIII) are studied and compared in terms of modified surface properties and industrial application niches. Furthermore, the reported results show how these different treatments have a big potential for research in smart and nano-functional surfaces in applications including biomaterials and many other specific developments.

Strain Stability and Carrier Mobility Enhancement in Strained Si on Relaxed SiGe-on-Insulator

A low thermal budget process to fabricate strained Si metal-oxide-semiconductor field-effect transistors (MOSFETs) on a strain-relaxed silicon–germanium-on-insulator (SGOI) by strain engineering is described. The strain stability in the top strained Si is studied after low temperature oxidation, ion implantation, and rapid thermal annealing, and only 7–9% relaxation is observed. The Ge content distribution in a strained-silicon-on-insulator (SOI) is investigated to validate the process with a low thermal budget. Ge, reaching the strained interface, inevitably degrades the gate oxide properties. The electron and hole mobility values in the biaxial strained-SOI are investigated and compared to those in MOSFETs fabricated in strain-relaxed SGOI and SOI substrates. Both carrier mobilities are enhanced, and the process is much simpler than using uniaxial strained Si. The relaxed-SGOI MOSFETs possess the lowest carrier mobility, and both the electron and hole mobility values in the strained-SOI MOSFETs are enhanced compared to the devices fabricated in the control samples and bulk Si. The SiGe layer in strained-SOI can lead to a larger leakage current.