Papers by Keyword: Defect

Abstract: The yield of power electronic devices is influenced by many factors including crystal defects like stacking faults (SFs). There are different types of stacking faults but their influence on the finished device and its performance and the behavior of SF during processing is not fully understood yet. With our contribution, we shed light on the issue, showing four different optically characterized subtypes of SFs with different electrical behavior that can already be found after implantation and wafer annealing in photoluminescence (UVPL) imaging. This enables a distinction between different SF classes without the need for a finally processed device and the corresponding electrical characterization. The goal of this paper is to illustrate an alternative for subdividing SF types that would otherwise be detected as triangular defects without any distinction and to show the different effects those subclasses have on finished devices with non-destructive methods that can be used in between device manufacturing steps. These results will be used as basis for further studies to confirm the found classes and to compare them with research about the different crystal structures by spectral PL measurements. For better understanding of the effect on the finished device, the PL imaging data is correlated with I-V characteristics of trenched diodes and the defect types are evaluated on their effect on the I-V characteristic, identifying 3 defect types with detrimental influence on the reverse bias and blocking voltage while the forward bias characteristic and I-V characteristic of one type is not effected by the defects.

Abstract: Transverse (charge) welds form during billet transitions in aluminium extrusion when incoming material progressively replaces residual metal inside the die, defining the length of extrudate that must be scrapped. This study aimed to quantify charge weld evolution under industrially relevant conditions that are often underestimated in scrap length assessment, including multi-cavity flow imbalance, non-symmetric multi-profile placement, and billet-to-billet thermal stabilisation effects. Three case studies were analysed using finite element simulation in QForm UK: (i) the International Extrusion Benchmark 2023 multicavity die producing three hollow tubes with intentionally varied port and bearing designs, (ii) an industrial two-profile die with translated (non-mirrored) profile positioning to avoid post-extrusion rotation, and (iii) a complex industrial profile extruded over multiple consecutive billets. The benchmark study demonstrated strong agreement between simulation and experimental charge weld evolution for two profiles, supporting the reliability of the predicted cavity-dependent differences driven by port volume. In the translated two-profile configuration, the charge weld cut length required for full purity increased from 1674 mm to 1940 mm (+16.0%), and by +15.9% under the 95% industrial criterion (1458.1 mm vs 1690.7 mm). Billet-to-billet variability was substantial, with charge weld length increasing by +70.1% from the first to the fifth billet (2819.0 mm to 4791.7 mm), before stabilising. Overall, the results show that charge weld length is governed by residence-time differences through ports and flow channels, requiring profile-specific assessment and consideration of process stabilisation. In this context, FE simulation provides an effective means to localise the mixed zone and to support die optimisation strategies aimed at reducing scrap.

Abstract: In this work we present the results of a comparison between the non-contact corona-based QUAD (Quality, Uniformity and Defects) technique for inline mapping of electrically active defects in SiC epi and final wafer level electrical device data on merged PiN Schottky diodes. A new defect analysis method for the QUAD mapping is introduced that involves the creation of a die yield bin map using the in-die values of depletion voltage that facilitates the comparison to the wafer level final electrical device data. Excellent correlation of the QUAD wafer bin map results to the final wafer level electrical device data was observed, illustrating that QUAD mapping of defects in SiC epi can provide a powerful and convenient inline complement to UVPL measurements for determining which defects are electrically active and will impact device performance.

Abstract: 3-channel analysis technique consisting of optical inspection, photoluminescence and X-ray topography methods for defect inspection of SiC epitaxial wafers has been investigated. The effectiveness of SiC wafer inspection image correction to enable automatic defect analysis is verified. Next, it is shown that the 3-channel analysis technique improves SiC defect inspection accuracy compared to conventional 2-channel analysis one.

Abstract: Cd_1-0.06Mn_0.06Te epitaxial thin films were synthesis on glass substrates by the Molecular Beam Condensation (MBC) method in the vacuum evaporation equipment УВН-71-ПЗ with steam-oil pumping and nitrogen trap at working pressure of residual gas (1÷2)x10^-4 Pa. By using additional source of Te vapor and controlling temperature, it has been determined the optimum conditions for obtaining Cd_1-0.06Mn_0.06Te epitaxial films with a perfect structure, clean and smooth surface, without of second phase inclusions. XRD investigations showed that Cd_1-0.06Mn_0.06Te epitaxial films grow on glass substrates on the (111) plane of the face-centered cubic lattice with the lattice parameter of a = 6.481 Å. Effect of γ-irradiation on XRD spectra of Cd_1-0.06Mn_0.06Te epitaxial films reveals that, XRD patterns of initial and γ-irradiated samples did not show any phase transformations, however there is a variation in relative intensities of diffraction peaks. It has been found that Cd_1-0.06Mn_0.06Te epitaxial films with a film thickness of d=15 µm, absorb light up to a wavelength of λ=765 nm and at λ>765 nm the absorption begins to gradually decrease and then the material becomes transparent. The obtained results indicate that Cd_1-0.06Mn_0.06Te epitaxial films absorb light quanta in the visible and infrared spectral regions. Iirradiation of Cd_1-0.06Mn_0.06Te epitaxial films with γ rays at low irradiation doses leads to a change in the optical parameters, the profile of the spectrum curves and the intrinsic absorption edge. In additions to experimental studies, a theoretical ab initio calculations of band structure (BS) of ideal and defective semiconductors of Cd_1-0.06Mn_0.06Te has been also carried out by using Density Functional Theory (DFT) method via Atomistix ToolKit computer program. The band gap energy has been calculated as E_g = 1.6 eV for ferromagnetic (FM) and E_g = 1.7 eV for antiferromagnetic (AFM) state of Cd_1-0.06Mn_0.06Te compound. The results of theoretical calculations on the band gap energy of ideal and defective Cd_1-0.06Mn_0.06Te semiconductors are in a good agreement with experimental findings.

Abstract: In this study, the use of the Fourier synthesis and the so-called Maximum Entropy Method (MEM) are evaluated in order to reveal the crystalline defect of the T’-type structure of one of 214 cuprate system, namely Pr_2-xCe_xCuO₄ (PCCO) powders. In the low-level density, the MEM calculations give a clear picture of the scattering and can eliminate the secondary scattering which may bother the main electron distribution of the specific atomic site. The covalent-bond is even clearer to be seen rather than the one obtained by the Fourier synthesis. This brings a further suggestion to use the MEM calculations in case of describing the scattering density of electron. Moreover, by means the used of the MEM calculations, the defect induced magnetism including the role of the tetravalent ionic doping and the annealing reduction effect is briefly discussed in this report.

Abstract: 8 inch 4H-silicon carbide (SiC) development faces challenges first from obtaining high-quality 8 inch SiC seed substrate, then reducing grown-in crystal residual stress and defects in the following crystal growth process. Here we report the diameter expansion process from 6 inch 4H-SiC seed substrate to 8 inch 4H-SiC crystal. Based on simulation and experimental results, it is deduced that an optimized radial temperature gradient (RTG) zone in the range of 0.10-0.12 °C/mm is essential for high-quality and efficient SiC crystal diameter expansion. According to the RTG calculation, diameter expansion process is designed and 8 inch 4H-SiC crystal as well as seed substrate is achieved. With the obtained seed substrate, high-quality 8 inch 4H-SiC crystal is developed and the following polished 4H-SiC substrate quality is characterized.

Abstract: The recently introduced corona charge non-contact capacitance-voltage technique, CnCV, is analyzed considering the production needs of epitaxial SiC wafers. The interfering mechanism of charge dissipation on fresh epitaxial 4H-SiC is identified as surface diffusion and is effectively eliminated by optimized ultraviolet pretreatment (UVPT). It is shown that optimized UVPT increases the CnCV dopant measurement voltage range and the depth of profiling. Concurrent UVPT and measurement provides a practical solution for improving throughput for multiple wafers. Electrical defect mapping shows that UVPT reduces the effective defect size. This will be helpful to avoid defects in patterns used for CnCV dopant measurements.

Abstract: Gel phantoms are useful materials for medical diagnostics and impact testing. The gel phantoms can be tailored to suit various tissues from the bulk, microscopic and molecular components. These components have responses under an AC electric field. In this work, a gel phantom was prepared using a commercially-available gel powder. Cylindrical samples with varying degrees of defects were cut from the prepared gel phantom and tested using an AC impedance analyzer. The defects were created by piercing a needle along the center plane of the sample and the degree of defects was varied by increasing the number of piercings in the sample. The conductivity of the sample at lower frequencies was influenced by the mechanism involved in water leakage due to piercing while the conductivity at higher frequencies was dominantly affected by space charge relaxation and structural conductivity barriers. The Nyquist plots obtained were seen to exhibit modified Randles-type behavior. Equivalent circuit fittings showed the parameters to be distinct with varying degrees of defects.

Abstract: This study offers a comprehensive examination of the behavior of 3C-SiC crystals grown on 4° off-axis (100) Si substrates with different off-axis angles along <110> and <100> for N and Al doping, respectively. The investigation takes advantage of molten KOH etching to conduct an in-depth investigation of the average density and size of the SFs inside the crystal for both n- and p-type doped 3C-SiC epitaxial layers. Moreover, 3C-SiC grown on a <100> off-cut substrate was revealed to have a greater concentration of SFs due to the absence of self-annihilation along the plane (-1-10). Considering two different doping ranges suitable for IGBTs and MOSFETs development, the impact of doping and off-angle on the crystal quality, concentration, and length distribution of SFs was then investigated in order to quantify the influence of N and Al incorporation on the structural and optical characteristics of the semiconductor. It turned out that under heavy nitrogen doping (~10¹⁹ cm^-3), when the dopant concentration grew, the average length of the stacking faults (SFs) expanded while their density dropped.