Papers by Keyword: Implantation

Abstract: This paper presents the development and optimization of a 1.2 kV Silicon Carbide (SiC) Trench MOSFET with a Bottom P-well (BPW), designed to achieve a compact structure and a simplified fabrication process. By performing the BPW implant before the trench etching process and utilizing it in conjunction with a shallow trench, the process complexity was reduced while maintaining effective corner coverage of the trench gate. Comprehensive simulations and unit process analyses were conducted to evaluate the effects of the hard mask sidewall angle, P-well, and JFET implant doses on device characteristics. Optimal performance was achieved by introducing an additional P+ implant in the P-well region, which significantly enhanced breakdown voltage without affecting channel properties. The optimized device demonstrated a specific on-resistance (R_on,sp) of 2.2 mΩ·cm², a breakdown voltage (BV) of 1600 V, and a threshold voltage (V_th) of 3 V, with potential further reductions in R_on,sp through substrate thinning.

Abstract: Semiconductor devices rely on the incorporation of donor and acceptor atoms into the crystal lattice to form locally doped regions. For dopant atoms incorporated into SiC by ion implantation, a high-temperature annealing step is required to achieve electrical activation. This annealing step is accompanied by redistribution of the implanted atoms. The influence of the annealing parameters on dopant redistribution is crucial when aiming for ever smaller device dimensions. In this work, we present a consistent analysis of the diffusion of Al implanted in 4H-SiC after high-temperature annealing at 1650 °C and 1800 °C for different annealing times. We identify the equilibrium diffusion coefficient at long annealing times from Al profiles obtained by SIMS analyses for both annealing temperatures. The temperature dependence is determined using an Arrhenius representation. This allows to quantify the equilibrium diffusion lengths for the actual temperature profiles, including heating and cooling rates. We find that the measured diffusion lengths for short annealing times are larger than expected from equilibrium diffusion and attribute the excess length to transient enhanced diffusion. Comparing the transient diffusion lengths of room-temperature and 500 °C-implanted samples, we conclude that the transient behavior is likely related to residual crystal damage induced during the implantation process.

Abstract: The problem of crystal damage recovery and of impurity substitution in implanted semiconductors is considered from a statistical mechanical viewpoint. This is done by resorting to a thermodynamic pseudo-potential originally developed for cooperative structural rearrangements in disordered systems close to their glass transition. The dependence of the substitutional fraction φ on the post-implantation annealing temperature T_ann in Al/4H-SiC systems is discussed in the light of these ideas. After completion of the annealing process, an Arrhenius plot of φ(T_ann) shows a slope in the order of 1 eV or less, depending on the amount of lattice damage initially produced by the implantation. Slopes ∼4 eV are found after incomplete annealing, indicating that substitution occurs mainly in damaged crystal cells. These concepts are suggested to be used for optimization of the doping procedure by ion implantation.

Abstract: Osseointegration prosthesis is a directly implanted fixation in the bone for limb amputees. It has been used as an excellent alternative for amputees experiencing difficulties from the use of a traditional socket type prosthesis. A novel implant used for implanted prosthetics is designed and it depended on polymer as a primary material to increase bone osseointegration. As an alternative to the metallic material on the interface with the bone. The design consists of several parts and relies on thread to increase installation. This research aims to overcome the problems of loss implantation by using new designs for fixations. Evaluated this design by FEA (Finite element analysis) in different load cases to obtain the distribution of stress and force reaction when the implant displacement was applied. The polymeric part was designed in two shapes, each shape relies on a different size of threaded to verify the change of fixation with the threaded. As for the metal part, two cases were used, the first case, stainless steel 316L, and the second case titanium metal to reach the best stress distribution in this design.

Abstract: A systematic germanium (Ge) and vanadium (V) study on 4H-SiC epitaxial layers is presented. Electrical results of TLM structures which were fabricated on these layers revealed that highly-doped Ge and V-implanted layers showed extremely low specific contact resistivity, down to 2 x 10^-7 Ω.cm². Current flow in the conducting state of Schottky barrier diodes has been successfully suppressed in some implanted layers, with highly V doped samples showing current density values of approximately 1 x 10^-5 Acm^-2 at 10 V. DLTS spectra reveal the presence of germanium and vanadium centers in the respective samples as well as novel peaks which are likely related to the formation of a novel GeN center.

Abstract: In this work the effect of the ion implantation on the dislocations structure of the 4H-SiC epilayer after the KOH etching has been investigated. The study was conducted using both Aluminum (Al) and Phosphorous (P) species for p-type and n-type, respectively. The ion implantations of Al and P were carried out at different energies (30–200 keV) to achieve 300 nm thick acceptor box profiles with a concentration of about 10²⁰ at/cm3. The implanted samples were annealed at high temperatures. With sequential sacrificial and stopping layer both species has been implanted on the same sample. Morphological charaterization of the samples (optical microscope and SEM) shown different structural modification of the dislocations (experically TED) after the KOH etching of the samples.

Abstract: 3C-SiC layers of different microstructures (monocrystalline (100) and (111) oriented and polycrystalline) were implanted with high energy (800 keV) ¹²⁹Xe⁺⁺ ions. Implantations were performed at room temperature (RT) and at 500 °C using two different fluences of Φ₁ = 1x10¹⁶ and Φ₂ = 1x10¹⁷ at/cm². Surface blistering was only observed for RT and Φ₂ implantations into poly-SiC material while mono-SiC kept rather smooth surface. This was due to more homogeneous Xe bubbles distribution (200 nm deep) in the mono-SiC than in the poly-SiC. Xe retention was found to be almost complete for all samples. Some Xe enhanced diffusion was detected in the poly-SiC material which was attributed to grain boundaries. Some irradiation-induced oxidation effect was evidenced, O element being located at the depth where Xe bubbles are accumulating. This was more pronounced for poly than for mono-SiC. These results demonstrate that SiC microstructure affects many aspects of its behavior upon Xe irradiation.

Abstract: The electron microscopic and diffraction analysis presented in the article showed that the structure of the surface layer of the titanium alloy OT4 after implantation at an accelerating voltage of 30 kV from the cathode Cu-Pb-Bi has a different hierarchical character. As a result of investigations of each of the levels, it was determined experimentally that the deformation mechanism under the action of internal stresses, as well as diffusion-relaxation reactions, are the main reasons for their formation, leading to the appearance of structural features in the surface layer of the OT4 alloy. In this case, penetration of alloying components to a depth of 10-25 nm is observed.

Abstract: The possibility to analyze micrometer scaled 2D implantation profiles is essential for improving SiC power devices. Due to the fact that the oxidation rate depends on the doping concentration a rather simple method was developed in order to decorate highly doped (aluminum) implantation profiles. For this purpose, different samples were grinded with a shallow bevel angle and subsequently oxidized. It could be shown that this method allows analyzing the implantation depth of different box-shape implanted samples. Furthermore the ability to distinguish micrometer scaled 2D profiles for a state-of-the-art SiC power device could be shown.

Abstract: Ranges for Al implantations into 4H-SiC (0001) were compared between channeled-ion implantation (without using a MeV implanter) and non-channeled ion implantation using an ion energy E₀ in the Bethe–Bloch region (IIBB). Since the latter (i.e., projected range of 7.5 μm at E₀ = 26 MeV) was larger than the former (i.e., maximum channeled range of 3.4 μm at E₀ = 900 keV), IIBB was concluded to be suitable to minimize the repeat count of epitaxial growth/ion implantation steps used in the fabrication of 4H-SiC superjunction power devices.