Papers by Keyword: Contact Resistance

Abstract: The heavily doped N+ source region in 4H-SiC MOSFETs is a critical design parameter, as its depth and the profile strongly influence contact resistivity and conduction efficiency. This work investigates the impact of varying N+ implantation depth on the electrical performances of 1.2 kV MOSFETs in both Nominal (linear cell) and Hexagonal (HEXFET) architectures. By varying implantation energy at a fixed dose, three junction depths were obtained: 0.22 µm (shallow), 0.24 µm (moderate), and 0.27 µm (deep). Transfer Length Method (TLM) measurements revealed a significant reduction in source contact resistivity with increasing depth, from 3.91×10⁻⁵ Ω·cm² (shallow) to 1.22×10⁻⁶ Ω·cm² (deep). For Nominal MOSFET design, electrical measurements confirmed a corresponding decrease in specific on-resistance (R_on,sp), from 3.05 to 2.89 mΩ·cm². However, deeper implants introduced greater lateral straggle, shortening the effective channel length and reducing the threshold voltage (V_th) from 2.25 V to 1.96 V. The channel barrier potential lowering associated with lateral straggle increased leakage current in the blocking mode, resulting in reduced breakdown voltage (BV). For Nominal MOSFETs, BV decreased from 1610 V in the shallow split to 1470 V in the deep split, while HEXFETs exhibited sharper BV degradation due to their higher channel density. To address this limitation, optimized JFET doping was introduced, restoring the BV of the deep split to 1560 V in the Nominal architecture. These results demonstrate that although increased N+ depth improves conduction by lowering contact resistance, careful co-optimization with P-well and JFET design is necessary to suppress high leakage current during blocking mode.

Abstract: In this work, an experimental methodology is presented for investigating the kinetics of competing oxidation and metal-plating processes that occur on friction surfaces under variable load conditions. The aim of the study was to determine the critical parameters for the transition between the formation of dissipative secondary structures (DSS) and metal-plating films (MPFs), as well as to evaluate the contact electrical resistance (CER) as an indicator of the structural state of the surfaces. A universal tribometer with adjustable load (0.2–40 MPa) was used to test friction pairs of steel 45 and bearing steel Shkh15, employing a vaseline oil as an inert lubricant and CIATIM-201 grease with 7% copper powder as a metal-plating additive. A clear correlation was observed between the CER, the friction coefficient (μ) and the wear intensity (I) across four operating modes. The maximum CER values (up to 40 Ω·cm²) were recorded in the DSS formation regime, whereas the minimum values (below 1 Ω·cm²) corresponded to the metal-plating regime. The results demonstrate that the structural-energetic approach enables effective diagnosis of the tribological state and that the CER parameter serves as an informative criterion for distinguishing between friction regimes.

Abstract: SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) exhibit excellent high-speed switching characteristics. However, the sheet resistance of the p-body region and the contact resistance between the p-body region and source electrode significantly degrade the switching performance. In this study, to clarify the effect of resistance on switching speed, which has not been sufficiently explored before, we used the temperature dependence of sheet and contact resistance and conducted switching tests under different temperature conditions. Furthermore, we created a circuit model that considered body effects and compared the results of the models with the measurements. We were able to reproduce the same temperature and resistance dependences as those exhibited by the experimental results, thus confirming the effectiveness of the model.

Abstract: N atoms were doped into SiN_x/4H-SiC substrates by KrF laser irradiation while the substrates were heated. The diffusion depth of nitrogen increased above the solubility limit when the sample heated to 600°C was irradiated by the laser compared to the sample at room temperature. In addition, a clear 4H-SiC pattern was observed in the cross-sectional TEM diffraction image, thereby suggesting that sufficient crystal recovery was achieved even under melt-solidification conditions owing to the effect of substrate heating.

Abstract: In this study, machine learning (ML) was employed to predict the electrical properties of finished devices, specifically focusing on the state of the contacts at the electrodes. The predictions are based on optical microscope images of the surface conditions, which were captured immediately following the laser doping of nitrogen atoms into 4H-SiC. The laser doping process involved varying the laser fluence from 0.4 to 4.0 J/cm² and using number of laser irradiation to 5, 10, 20, and 100 shots. The ML prediction was carried out in two steps. In STEP1, we classified the contact status into three types.: 1) Schottky junctions (insufficient doping), 2) Ohmic contact (good contact), and 3) Not ohmic (damage caused by laser irradiation). In STEP2, contact resistance prediction (numerical regression) was performed using the dataset predicted as an ohmic contact. As a result, we found that the three classifications in STEP1 could be predicted with a high accuracy of over 88%. Furthermore, the contact resistance prediction in STEP2 could be made with an accuracy (RMSPE: root mean square percent error) of 27.2%. Visualizing the prediction basis of numerical regression using modulus-reweighted grad-regression activation mapping (MoRAM) revealed that the ML model focused on the inside of the laser-irradiated area in the optical microscope image. The results of the scanning electron microscopy observation of the laser-irradiated area showed that ablation and residuals were generated during laser doping in that area. Consequently, it was concluded that our ML model predicted the contact resistance of the finished device taking into consideration these surface conditions. Even highly-skilled laser doping technicians have difficulty predicting the resistance values arising from the ablation and residue conditions. Based on above results, we conclude that our ML model is capable of predicting the electrical characteristics of a finished device, a task that is often considered challenging for humans.

Abstract: Nowadays, the growing worldwide electrification requires new materials for power management. SiC currently dominates the market thanks to excellent energy efficiency and broad operating capabilities. The present paper proposes an experimental study of the Ni-SiC backside ohmic contact formation using 308 nm nanosecond laser annealing (NLA). After Nickel (80 nm) sputtering over 4H-SiC wafers, various laser conditions are investigated, with energy density (ED) ranging from 2.4 to 5.4 J/cm², pulse number from 1 to 20 and chuck temperature from 25 °C (RT) to 400 °C. For all series, a common scenario is noticed as the ED increases, with first solid-state reactions, then local melt and, finally, complete top layer melt and de-wetting at high ED. An in-depth understanding of the impact of laser conditions on these stages is achieved, based on electrical data, Raman spectroscopy, optical microscopy, Scanning Electron Microscopy (SEM) and Scanning Transmission Electron Microscopy (STEM). Results reveal that both high pulse numbers and the use of a hot chuck enable to significantly reduce the ED needed to form low resistance contacts. In addition, sheet resistances and contact resistivities are linked to the microstructure evolution upon NLA exposure. As a proof-of-concept, an acceptable process point yields a contact resistivity around 5×10^-5 Ω cm² when the wafer is processed at 25 °C and a value as low as 10^-5 Ω cm² for 400 °C processing. The mechanisms involved and discussed in the present work may very likely pave the way for other contact formation with limited thermal budget.

Abstract: As a branch of 3D printing technology, metal 3D printing is an important advanced manufacturing processing method. Metal 3D printing technology has been widely applied in a variety of areas, including the aerospace field, biomedical research and mold manufacturing. This paper proposed a new method for melting metal wires via contact resistance heating. Through the combination of a numerical control technique, a mechanical structure and computer software, a metal 3D printing device was designed based on the principle of fused deposition modeling. The printing nozzle of the device can be heated to over 1400°C in a few minutes. Additionally, we performed experiments with aluminum wire to demonstrate the feasibility of the printing method. The designed consumer-level desktop metal 3D printer cost less than 1500 dollars to fabricate.

Abstract: 3D Simulation was carried out and compared with fabricated ZnO NWFET. The device had the following electrical output characteristics: mobility value of 10.0 cm²/Vs at a drain voltage of 1.0 V, threshold voltage of 24 V, and subthreshold slope (SS) of 1500 mV/decade. The simulation showed that the device output results are influenced by two main issues: (i) contact resistance (R_con ≈ 11.3 MΩ) and (ii) interface state trapped charge number density (Q_IT = 3.79 x 10¹⁵ cm^-2). The Q_IT was derived from the Gaussian distribution that depends on two parameters added together. These parameters are: an acceptor-like exponential band tail function g_GA(E) and an acceptor-like Gaussian deep state function g_TA(E). By de-embedding the contact resistance, the simulation is able to improve the device by producing excellent field effect mobility of 126.9 cm²/Vs.

Abstract: Based on the laboratory micro-motion contact resistance test system, fretting characteristics of the two contact pairs of gold-plated probe and tin-plated samples, gold-plated samples and tin-plated probe, is carried out at different plating thickness, contact force and temperatures. The contact pairs after the fretting experiment were subjected to temperature and humidity test and salt spray test to analyze its environmental reliability. 0.76μmAu-Sn has better fretting characteristics than 4μm Sn-Au. When the contact force is greater than or equal to 100 gf, the two kinds of contact pair exhibit good fretting characteristics. Thickness of sample plating is more important than that of probe. The influence of ambient temperature on fretting contact performance is the weakest. The increase of contact resistance of contact pair 4μm Sn-Au is higher than that of 0.76μmAu-Sn after accelerated environmental simulation experiments.

Abstract: The new technology of ensuring efficiency of reducers of construction machines is offered. The technology is based on the application of hardening coatings on the contact surface of the gear teeth. To implement the method, the authors developed an installation for applying hardening coatings by ion implantation. Similar devices used for the application of hard materials in the form of diffusion coatings on hot parts of tooling and machine parts are described. It is shown that the proposed installation has a greater technical and economic efficiency compared to existing analogues. The description of the design and operating principle of the proposed device is presented. The results of experimental researches of efficiency of the offered technology are presented. The modes of processing allowing to achieve the maximum indexes of working capacity are picked up. The conducted researches have shown the efficiency of the offered technology for the details from hard alloys.