Papers by Keyword: Silicon Carbide (SiC)

Abstract: This study aims to develop an electrochemical assisted fixed-abrasive lapping (ECAL) process for thinning 4H-SiC wafers (C-face). Process with 20 wt% NaNO₃ electrolyte to generate a softened passivation layer has been formed and simultaneously removed by a fixed diamond lap wheel. Electrochemical tests using a potentiostat have verified 20 V as the selected experimental potential, and a significant reduction in hardness has been confirmed by nanoindentation. Under these conditions, the 4-inch wafer has achieved a material removal rate (MRR) of 3.181 μm/h with wafer quality (Bow –7.80 μm, Warp 48.50 μm, TTV 7.70 μm). When the same conditions have been applied to 6-inch wafers, an MRR of 2.457 μm/h and wafer quality (Bow –5.00 μm, Warp 36.70 μm, TTV 6.60 μm) have been obtained. These results have demonstrated the scalability of ECAL for larger SiC substrates, offering potential for next-generation device manufacturing.

Abstract: Strain relief etching is a critical wet process technique use in high volume manufacturing of semiconductor substrates and device wafers. The goal of a strain relief etch is application dependent but can generally be considered for removal of warp/bow or improving mechanical strength by removing sub-surface damage thereby optimizing yields. Silicon Carbide (SiC) has a high chemical resistance which has blocked SiC wafer manufacturers from using strain relief etching to date. In this work, we demonstrate strain relief etching using an Advanced Chemical Etching (ACE) process of the full wafer surface on commercial grade 4H-SiC wafers and poly-SiC wafers at high etch rates (μm’s/hr) which enable ACE as a production technique. The data shows a 4 times improvement of breakage strength, from 13 to 55N, in laser split wafers. Bow and warp of ground wafers is reduced from 70/250µm to -5/25µm approx. respectively, matching Chemical Mechanical Polished (CMP) wafers which is the industrial method for preparing wafers. Thus showing the potential of stronger, flatter wafers being available for chemical mechanical polishing.

Abstract: With the growing application of wide-bandgap semiconductors such as SiC in power electronics, efficient and low-damage machining of large-diameter, high-quality 4H-SiC wafers has become a critical research priority. This study systematically compares the grinding behavior of the C-and Si-faces of laser-sliced 4H-SiC wafers and reveals the effect of crystallographic anisotropy on tool wear. In the experiments, a picosecond laser was used to induce internal crystal modification, and multiple pairs of 12-inch high-purity semi-insulating crystals and wafers were obtained through ultrasonic separation. These wafers were subsequently ground using #800/#8000 resin-bonded diamond wheels. Material removal and wheel wear were recorded in real time, and the wheel wear ratio (W/M) was adopted as the key evaluation metric. Nanoindentation and white-light interferometry were further employed to characterize the mechanical properties and surface morphology of the two crystal faces. Results show that in both rough and fine grinding, the C-face demonstrates superior material removal performance despite its higher hardness, whereas the Si-face is more prone to wheel degradation. For thin wafers, residual laser focus near the surface further aggravates wheel wear. These findings establish a link between crystallographic anisotropy, laser-modified layer position, and wheel wear behavior, providing an experimental foundation for clarifying the underlying mechanisms and developing face-specific grinding strategies for high-quality SiC wafer fabrication.

Abstract: This paper investigates the dynamic conduction behavior of silicon carbide (SiC) MOSFETs in thesub-threshold regime. We demonstrate that controlled gate bias preconditioning, combined with timeresolvedelectrical measurements in thermal equilibrium, reveals a notable drift in the source-drainvoltage Vsd. The direction of this drift depends on the polarity of gate preconditioning and is directlyrelated to variations in the channel conduction. These effects are shown to be attributed to chargerelease from deep oxide traps, leading to a gradual shift in the flat-band voltage (Vfb) over time.Experimental results reveal that these dynamic effects are most prominent in the depletion and weakinversion regimes. Our findings highlight the influence of oxide trap dynamics on the body diodeforward voltage (Vf) and its significance for the reliability of SiC devices, specifically in its role asthe temperature-sensitive parameter.

Abstract: This work investigates the short-circuit (SC) reliability of Split-Gate (SG) versus planar 4H-SiC MOSFETs through TCAD simulations. While SG-MOSFETs effectively reduce gate-drain capacitance and improve switching performance, SG-MOSFETs exhibit enhanced short-circuit failure effects. Structural optimization—such as thicker drift regions, extended gate lengths, and narrowed JFET widths—can improve SC withstand time (SCWT). However, SG-MOSFETs suffer from intensified electric field crowding and enhanced drain-induced barrier lowering (DIBL), leading to greater post-SC leakage and thermal instability. Results suggest SG-MOSFETs require careful field and oxide engineering to ensure reliability under fault conditions.

Abstract: The repetitive peak forward surge current (I_F,RM) is a practically important parameter for SiC Schottky diodes, as it ensures reliable and robust circuit designs. However, there is no established method and criterion for this imperative parameter. Manufacturers predominantly provide the non-repetitive peak forward surge current value (I_F,SM) in datasheets, which is generally determined from derated measured peak currents that cause diode failures. Consequently, it is assumed that I_F,SM enables diodes from various manufacturers with different structural designs to be compared in terms of their repetitive surge current performance. In this paper, we will demonstrate the need for a consistent criterion and a method to determine I_F,RM by analyzing repetitive surge currents in representative commercially available SiC Schottky diodes. The analysis is based on a recently proposed method and criterion for the repetitive peak surge current in SiC Schottky diodes that ensures the junction temperature does not exceed the maximum device rating, which is 175°C for the commercially available devices analysed in this study.

Abstract: Radiation-hardened SiC power devices are essential to prevent leakage degradation and catastrophic failures such as SEE and SEB. Lateral device structures lower the risk of contact shorting by providing greater physical separation between conductive regions. Wider device geometries also improve radiation tolerance, as larger dimensions can accommodate charge buildup with less effect on device performance. In addition, RESURF structures enhance robustness by shifting the high electric field into the bulk, which reduces the impact of radiation-sensitive interface states on breakdown.

Abstract: In this study, we conducted in-situ measurements on a SiC JFET operational amplifier operating under gamma-ray irradiation. It shows that the radiation did not affect the output waveform or voltage gain, but shifted the output offset voltage. This shift may result mainly from holes generated by irradiation and trapped in the oxide layer, which modified the I-V characteristics of the level-shifting diodes. It can be compensated by applying bias voltage, and it may also be prevented by optimizing the diode structure and/or circuit topology.

Abstract: A laser-based experimental system was developed to investigate Single Event Burnout (SEB) in high-voltage silicon carbide (SiC) devices. By enabling transient measurements under high reverse-bias conditions, the setup emulates ion-induced charge generation with femtosecond laser pulses. Time-resolved waveforms and charge collection trends were obtained, showing consistency with previous heavy ion experiments. This confirms the system’s capability to reproduce SEB-relevant dynamics. Further improvements in spatial resolution and impedance matching are required for detailed analysis of internal charge transport mechanisms.

Abstract: This paper presents the development of a confocal Optically Detected Magnetic Resonance (ODMR) system to study diamond and Silicon Carbide (SiC) for reactor dosimetry and quantum defect analysis. Initially, Nitrogen-Vacancy (NV) centers in diamond were characterized to establish a performance baseline, followed by plans to map and quantify color center populations in SiC crystals before and after alpha and neutron irradiation. By correlating ODMR data with electrical performance metrics, we aim to optimize fabrication and annealing protocols to investigate fast neutron sensitivity. The ODMR system, integrated with a home-built confocal microscopy setup, includes a microwave antenna, magnet, laser, objective, and advanced measurement devices such as Si-APD and Time Tagger 20 for high-resolution T2* and T2 measurements. The characterization of the instrument includes high-resolution fluorescence and ODMR spectra of NV centers in diamond, and improved resolution with confocal optics. Ongoing work focuses on correlating luminescence with reactor neutron fluence and the long-term goal is for the advancing SiC irradiation for integrated spin defect analysis.