Plasma Immersion Research Articles

4H-SiC P+N UV Photodiodes: Influence of Temperature and Irradiation

ABSTRACT4H-SiC p+n photodiodes based on ultrathin-junctions have been fabricated with distinct processes for the p+-region creation: either with Aluminium conventional ion implantation, or with Boron Plasma Ion Immersion Implantation. Spectral sensitivity measurements were performed at several temperatures from room temperature up to 340°C, with incident wavelengths ranging from 200 to 400 nm. Both responses are characterized by a stability between 200 and 270 nm, and a important increase with temperature between 270 and 380 nm. This fact has to be related to the two different kinds of optical absorption phenomena in SiC with respect to the wavelength, which are direct and indirect (phonon assisted) transitions. When decreasing the temperature, we noticed a hysteresis effect, which could be due to charge trapping by temperature activated defects. After strong proton and electron irradiations, the diodes showed a stability of the response below 270 nm, making them suitable for use in harsh environments. Simulation was performed at room temperature, with a good correlation between simulated and experimental room temperature curves.

Kinetics of post-treatment structural transformations of nitrogen plasma ion immersion implanted polystyrene

The surface chemistry of a synthetic material in contact with a biological system has a strong influence on the adhesion of proteins to the surface of the material and requires careful consideration in biomedical applications. The structure of plasma immersion ion implantation (PIII) treated polymer and its surface free energy depend on the ion fluence delivered during the treatment and on the time after the PIII treatment. These dependences have been investigated using the example of nitrogen plasma implanted polystyrene (PS). Contact angle measurements, FTIR–ATR spectra and X-ray photoelectron (XPS) spectra were acquired as a function of ion fluence and time after treatment. The results showed a close relationship to the kinetics of free radicals that had been examined in a previous study. The kinetics of oxidation and surface free energy had two stages, one with a characteristic time of several hours and the other with a characteristic time of several days. The concentration of nitrogen-containing groups decreased with time after PIII treatment, partly, due to their release from the PS surface.

Helium retention and early stages of helium-vacancy complexes formation in low energy helium-implanted tungsten

Tungsten has been selected as the material of the divertor of the ITER fusion reactor. In operation, tungsten will be submitted to high alpha particles bombardment. The consequence of helium implantation is a major issue for the reliability of tungsten components. The aim of the study was to investigate the behavior of helium implanted in tungsten at low energy and low flux. 320eV Helium ions were introduced by plasma immersion at the flux of 2.5×1018ion/m−2/s−1. The helium behavior was investigated by Nuclear Reaction Analysis and the evolution of the tungsten lattice by Positron Annihilation Spectroscopy (PAS). Helium-implanted tungsten exhibits a low retention rate (13.6% at 9.4×1019Hem−2) which decreases with the implantation fluence. The desorption of helium starts at low temperature (<400K). SEM analysis after annealing over 973K shows sparse pores probably due to bubbles opening at the surface. The creation of helium-filled defects in the near surface layer (0.5 to ∼20nm) was followed by PAS. A low level of damages was introduced by 12MeV proton irradiation, prior to He introduction and allowed to examine the influence of pre-existing defects on the helium trapping. The PAS results suggest that the early stage of the formation of helium-filled vacancy clusters does not require the presence of pre-existing vacancy and thus proceed from the trap mutation phenomenon.

High frequency and low voltage plasma immersion ion implantation of nitrogen on industrial pure iron at different Rf power

Traditional plasma ion immersion implantation (PIII) can effectively improve material mechanical property and corrosion resistance. But the modified layer by PIII is too thin for many industrial applications. High frequency and low voltage plasma immersion ion implantation (HLPIII) has advantages of PIII and nitriding. Comparing with traditional ion nitriding, HLPIII can obtain higher implantation energy and create a thick modified surface layer. In the present paper nitriding layers were synthesized on industrial pure iron using high frequency and low voltage plasma immersion ion implantation with different RF power (400 W, 600 W, and 800 W). The microstructure of the nitriding layers was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The mechanical properties such as microhardness and wear resistance were analyzed using HXD1000 microhardness and CSEM pin-on-disk wear testing machine. The anodic polarization characteristics were measured in a 0.9% NaCl solution at room temperature to examine the corrosion resistance of the nitriding layer. The results reveal that Fe 2N, Fe 3N and Fe 4N coexist in the nitriding layer. The nitriding layer is a corrosion protective coating on industrial pure iron in 0.9% NaCl solution. The hardness, wear resistance and corrosion resistance of the nitrided layers on industrial pure iron increase with RF power.

Low-temperature low-damage sterilization based on UV radiation through plasma immersion

This paper introduces a new type of high-frequency (HF) sustained discharge where the HF field applicator is a planar transmission line that allows us to fill with plasma a long chamber of rectangular cross-section (typically 1 m × 15 cm × 5 cm). Peculiar interesting features of this plasma source are a low gas temperature (typically below 40 °C in the 1 Torr range in argon), broadband impedance matching with no need for retuning, stability and reproducibility of the discharge (non-resonant behaviour). This type of plasma source could be useful for web processing; nonetheless, it is applied here to plasma sterilization, taking advantage of its low gas temperature to inactivate microorganisms on polymer-made medical devices to avoid damaging them. The predominant biocide species are the UV photons emitted by the discharge whereas most plasma sterilization techniques call for reactive species such as O atoms and OH molecules, which induce significant erosion damage on polymers. Polystyrene microspheres are actually observed to be erosion-free under the current plasma sterilization conditions (scanning electron micrographs have been examined). Moreover, inactivation is quite fast: 106 B. atrophaeus spores deposited on a Petri dish are inactivated in less than 1 min. Correlation of the UV radiation with the spore inactivation rate is examined by (i) considering the emitted light intensity integrated over the 112–180 nm vacuum UV (VUV) range with a photomultiplier; (ii) looking with an optical spectrometer at the emission spectrum over the 200–400 nm UV range; (iii) using absorption spectroscopy to determine the role of the VUV argon resonant lines (105 and 107 nm) on spore inactivation. It is found that the test-reference spores are mainly inactivated by VUV photons (112–180 nm) that are primarily emitted by impurities present in the argon plasma.

Scanning Spreading Resistance Microscopy For 3D-Carrier Profiling in FinFET-based Structures

ABSTRACTJunction formation in FinFET-based 3D-devices is a challenging problem as one targets a complete conformal doping of the source/drain regions in order to produce equal gate-profile overlaps (and thus transistor behavior) on all sides of the fins. Due to the lack of predictive modeling for several of the doping strategies explored (plasma immersion, cluster implants, vapor phase deposition, etc…) it becomes difficult to correctly predict the performance of the devices and hence, accurate 3D-doping profile determination is desired. Although several dopant/carrier profiling methods exist with excellent one- or two-dimensional resolution and properties, there is an urgent need to extend these towards a quantitative three-dimensional geometry. In this work, we use scanning spreading resistance microscopy (SSRM) with dedicated FinFET test structure to obtain three-dimensional information from successive two-dimensional scanning spreading resistance maps. We also assess the validity of our methodology by comparing various sections along the fins which represent the variability due to the processing and measurement procedure.

AlN nanoclusters formation by plasma ion immersion implantation

We report on simultaneous (Al + N) implantation of Al and N into layers of amorphous thermal silica (SiO 2) in an attempt to bond Al with N and form the binary compound AlN. As an implantation technique, plasma ion immersion implantation (PIII) is used. The energy and ion fluence were varied in order to obtain nanocluster containing films in the thickness range 10–50 nm. The elemental distribution profiles in the substrate were evaluated by means of elastic recoil detection analysis technique (ERDA). The nature of the chemical bonds was determined by X-ray photoelectron spectroscopy (XPS). The simultaneous implantation using rf plasma source for N ions and a cathodic arc to produce the Al ions provides good overlap of the elemental profiles and high retained doses of Al and N are achieved. The binding energies of the Al 2 p and N 1 s core electrons indicate that formation of near-stoichiometric aluminium nitride is achieved.

Liquid crystal alignment on the a-C:H films by Ar plasma ion immersion

A plasma ion immersion treatment has been developed to enhance the liquid crystal (LC) alignment on the hydrogenated amorphous carbon (a-C:H) layer in an inductively coupled plasma (ICP) chamber. No LC alignment was observed for the a-C:H layer tilted at an angle of 0° during the bombardment with plasma ions. The LC alignment occurs for the a-C:H layer tilted at an angle of 30° or 60°. Their pretilt angles (∼ 1.4°) are approximately the same. The azimuthal anchoring strength is 1.98 × 10 - 6 J/m 2 at a tilted angle of 30° and 1.14 × 10 − 4 J/m 2 at a tilted angle of 60°. The mechanism for the LC alignment is attributed to the oblique incidence of ions within the matrix sheath of non-uniform thickness near the a-C:H surface under a negative pulse bias. The matrix sheath of non-uniform thickness is confirmed by the plasma density distribution in the ICP chamber and the X-ray photoemission spectra across the a-C:H layer.

Magnesium Implantation by Plasma Immersion in Polymers for Oxidation Protection in Low Earth Orbit Environment

Magnesium ions were implanted by plasma immersion into Kapton, Mylar (PET), and polyethylene (PE) films to create a protective MgO layer for protection against atomic oxygen in low earth orbit environment. Exposure to oxygen plasmas showed improvement in oxidation resistance similar to previous results obtained with aluminum implantation. X-Ray photoelectron spectroscopy depth profile analysis showed that MgO layers had similar thicknesses and mixing layers as previous aluminum implantation. A much thinner and shallower layer was deposited on Mylar with metallic Mg together with the oxide, probably due to a lower bias voltage caused by variable plasma response to the applied voltage. Inspecting the surface with scanning electron microscope after oxidation, thermal cycling, and adhesion tests, the presence of cracks and pinholes showed a more severe degradation of the deposited layer when compared to aluminum deposition.

Features of pulse substrate bias voltage generation with electron tubes

Features of pulse substrate bias voltage generation with electron tubes in different operation modes are considered. The overstressed mode with low anode voltage and return of electrons to the grid has practical significance at bias voltages in the kilovolt range under the conditions of large substrate current fluctuations. This mode ensures small bias voltage fluctuations and effective use of the primary DC voltage. When the substrate current spontaneously rises above the critical value, the tubes automatically decrease the bias voltage and suppress current spikes and arcing. Such approach may be used in PVD processes, for ion surface treatment and ion plasma immersion implantation.

Evaluation of diamond-like carbon coatings produced by plasma immersion for orthopaedic applications

The purpose of the present study was to evaluate the properties of diamond-like carbon (DLC) coating on Ti alloy (Ti–13Nb–13Zr) produced by plasma immersion. Measurements of mechanical properties and corrosion behaviour were investigated. The corrosion studies (polarization test and electrochemical impedance spectroscopy) indicated that DLC coating could improve corrosion resistance in the simulated body fluid environment. In vivo tests were carried out by inserting 5 × 1 mm diameter DLC-coated Ti–13Nb–13Zr cylinders into both muscular tissue and femoral condyles of rats for intervals of 4 and 12 weeks postoperatively. Histological analyses showed that the DLC coatings were well tolerated in both types of implantation, demonstrating the in vivo biocompatibility of the DLC coatings produced by plasma immersion.

Surface properties and cell behaviour of diamond-like carbon coatings produced by plasma immersion

The morphology, microstructure and roughness of the diamond-like carbon (DLC) films produced by plasma immersion were investigated. Vero cells (fibroblasts) were utilized for the in vitro biocompatibility studies of the DLC-coated Ti–13Nb–13Zr alloy. In the cytotoxicity assay, fibroblast cells were cultured for a period of 24 h, and in the adhesion assay, cells were cultured for a period of 2 and 24 h. The cell morphology was investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). No evidence was found that the presence of the DLC coating had any adverse effect. Our results show that the adherence of fibroblasts was significantly enhanced when Ti alloy was coated with DLC from the uncoated.

812 炭素または窒素イオン注入した鉄鋼表面の特性

Carbon or nitrogen ion was implanted into tool steels by means of different type of ion-implantation equipment, such as beam-line and plasma immersion. Various implantation conditions were used in order to investigate relation between mechanical properties and surface modification by ion implantation. The implanted surface was characterized by X-ray diffractmeter(XRD)for identification of in-situ synthesized carbide and nitride. Auger electron spectroscopy(AES)was used to determine the depth profile of the implanted species. Substrate temperature was estimated from the hardness of tool steel substrate treated at simultaneously. Surface hardness and tribological properties were modified by ion implantation, especially in high-speed tool steel.

High Deposition Rate of Diamond-like Carbon on Trench Bottom for Acetylene Gas at Plasma Immersion and Deposition Process

A bright optical emission inside a trench in a solid object was observed during a diamond-like carbon (DLC) deposition process, with the DLC deposition rate being more than two-times faster on the trench's bottom than that on the top of the trench. We found that the secondary electrons inside the trench played an important role in the higher DLC deposition rate on the trench's bottom.

Atomic Force Microscopic Observations of Diamond-like Carbon (DLC) Films Produced by Plasma Immersion and Fibroblasts Cultured on DLC

Diamond-like carbon (DLC) films have been intensively studied with a view to improving orthopaedic implants. Studies have indicated smoothness of the surface, low friction, high wear resistance, corrosion resistance and biocompatibility [1-4]. DLC coatings can be deposited using various techniques, such as plasma assisted chemical vapour deposition (PACVD), magnetron sputtering, laser ablation, and others [5]. However it has proved difficult to obtain films which exhibit good adhesion. The plasma immersion process, unlike the conventional techniques, allows the deposition of DLC on three-dimensional workpieces, even without moving the sample, without an intermediate layer, and with high adhesion [6], an important aspect for orthopaedic articulations. In our previous work, DLC coatings were deposited on silicon and Ti-13Nb-13Zr alloy substrates using the plasma immersion process for the characterization of microstructure, mechanical properties and corrosion behaviour [7-9]. Hardness, measured by a nanoindenter, ranged from 16.4-17.6 GPa, the pull test results indicate the good adhesion of DLC coatings to Ti-13Nb-13Zr, and electrochemical assays (polarization test and electrochemical impedance spectroscopy) indicate that DLC coatings produced by plasma immersion can improve the corrosion resistance [9].

Platelet Adhesion Study and Characteristic of Hydrogenated Carbon Films Synthesized by PIII-D

Amorphous hydrogenated carbon (a-C:H) thin films were deposited on silicon wafers and Ti6Al4V substrate using plasma ion immersion implantation and deposition (PIII-D) at room temperature (R.T.). The composition and structure of a-C:H films were employed by X-ray photoelectron spectra (XPS) and Raman spectra. Nano-indenter tests measured the hardness of the films. In addition, wettability and bloodcompatibility were investigated. In this paper, the effects of hydrogen content on structure, mechanical properties, surface wettability and haemocompatibility were discussed.

The Influence of the Defect Structure on the Nitriding of Fe by PIII

Plasma ion immersion implantation is a promising technique for nitriding. A case study of the characterization of the plasma ion immersion implantation nitriding of iron alloys is the plasma ion immersion implantation nitriding of pure Fe. A set of Fe samples of 99.98% purity and with different defect structure was plasma ion immersion implantation nitrided at different temperatures. Depth profiling of the samples was achieved using positron annihilation spectroscopy with a slow positron beam and nanoindentation. A correspondence was found between the line shape parameter S and the hardness of the plasma ion immersion implantation treated samples.

Hydrogen storage in the bubbles formed by high-flux ion implantation in thin Al films

The storage of implanted hydrogen in 2–5 μm thick Al films on stainless steel substrates was investigated in this work. Plasma immersion 1 keV H 2 + ion implantation was used to load hydrogen into the Al film. The correlation between the effusion of the implanted hydrogen and the evolution of surface morphology was studied by thermal desorption spectroscopy and scanning electron microscopy. It has been found that as-implanted hydrogen at temperatures below 320 K is associated with defects and is chemically bonded at the grain boundaries of nanocrystallites. At higher temperatures, the released hydrogen is accommodated in bubbles. The major part of hydrogen effuses at ∼630 K and the effusion process is controlled by the migration of hydrogen through the surface oxide layer.

Characterization of a high-density plasma immersion ion implanter with scaleable ECR large-area plasma source

A key issue for future high-performance CMOS techniques is the fabrication of 12 in. or larger silicon-on-insulator (SOI) wafers with thickness of the top silicon layer under 25 nm. The electron cyclotron resonance (ECR) plasma ion immersion implanters (ECR-PIII) are viable candidates to realize the above. We designed an ECR-PIII in which we integrated the new concept of a large-area plasma source. This new plasma source is an array of elementary ECR plasma sources created by an assembly of m linear microwave sources. Each linear microwave source has n radiating elements ( n> m) and includes a system of permanent magnets that create magnetic induction for ECR to occur in the processing chamber. An array of 90 elementary ECR plasma sources generate highly homogeneous dense plasma with dimensions permitting processing of 12-in. wafers. Since hydrogen implantation requiring high dose often results in blistering of the wafer surface, a new Smart-Cut™-like technology has been suggested (US Patent 6,352,909) where the one-step hydrogen implantation is replaced by a two-step process. The designed ECR-PIII can offer substantial advantage in providing the high yield of protons used for the micro-bubble formation in the two-step process.

Mechanism of apatite formation on hydrogen plasma-implanted single-crystal silicon

Hydrogen is implanted into single-crystal silicon wafers using plasma ion immersion implantation to improve the surface bioactivity and the mechanism of apatite formation is investigated. Our micro-Raman and transmission electron microscopy results reveal the presence of a disordered silicon surface containing Si–H bonds after hydrogen implantation. When the sample is immersed in a simulated body fluid, the Si–H bonds on the silicon wafer initially react with water to produce a negatively charged surface containing the functional group (Si–O−) that subsequently induces the formation of apatite. A good understanding of the formation mechanism of apatite on hydrogen implanted silicon is not only important from the viewpoint of biophysics but also vital to the actual use of silicon-based microchips and MEMS inside a human body.