Papers by Keyword: Yield

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: The increasing demand for sustainable energy solutions has intensified research into biodiesel production, which relies on chemical catalysts that have an environmental impact. This study investigates the alternative methods of biodiesel production by utilizing agricultural waste, specifically rice husk, coconut husk, and chicken manure as a catalyst for biodiesel production. Laboratory experiments were conducted to extract metal oxide from agricultural waste to be used as a catalyst in the transesterification process. The obtained ash was characterized, and it was revealed that rice husk ash contained 98% SiO₂, coconut husk ash had 72.62% of K₂O, and chicken manure ash had 46.56% CaO, with higher metal oxide compositions in each material. The transesterification reaction was conducted by varying alcohol to oil ratio from 3:1, 6:1, 9:1, and 12:1, temperature (40-80°C), catalyst concentration (1.5-4.5%wt), and reaction time (20-120min) to assess catalyst efficiency. Pure CaO was used as a control catalyst for comparison. Characterization of the produced biodiesel from all catalysts was conducted and compared to ASTM D6751 standards. The results for acid value, moisture content, density, viscosity, free fatty acid, flash point, pour point, and cloud point were analyzed and found to comply with ASTM D6751 standards. On quantity determination of produced biodiesel, the most effective catalyst was chicken manure ash with a yield of 80% and the least effective catalyst was rice husk ash with 68% yield. Using agricultural waste reduces up to 40% production cost.

Abstract: Due to the lack of internationally accredited quality standards for silicon carbide (SiC) epiwafers, vendors provide defect maps using different metrology techniques and naming conventions, making it difficult to draw correlations between defect types and unclamped inductive switching (UIS) behavior. This study tested 1700 V rated Junction Barrier Schottky Diodes (JBS) using materials from five 4H-SiC epiwafer suppliers and concluded that, without maps having industry-standardized defect names and showing precise locations, sizes, and shapes, device manufacturers cannot effectively predict UIS yield and reliability.

Abstract: Silicon Carbide is an exceptionally hard and challenging to process semiconductor material. Effective device singulation retaining 100% die yield is hard to achieve with conventional saw dicing. Chips, microcracks and machining abrasions lead to reduced die strength and increased scrap. With rapid advancements in SiC device processing, resolving many fabrication issues, dicing yield losses are becoming an area of industrial concern. Plasma dicing has a proven track record in silicon and presents a potential solution to low yields during SiC dicing. Smooth vertical sidewalls with no machining damage, with etch rates approaching 5 μm/min, position SiC plasma dicing as a viable alternative ready for industrial uptake. Plasma etch processes development using Ni and Cu etch masks, with full singulation have been demonstrated, resulting in improved die strength compared to saw diced samples.

Abstract: This work discusses three aspects of the PVT growth process to reach a higher SiC crystal yield: (i) Type of carbon isolation material and procedure to maintain reproducible growth conditions from one process to the next. (ii) The pros and cons of temperature and power control (or a mixture of both) during the SiC crystal growth phase of the PVT process; and (iii) the selection of a set of process parameters and the specifications of the grown SiC crystal, which serve as a fingerprint of reproducible growth conditions (related to the selection and design of hot zone isolation components).

Abstract: Several defects were analyzed through the manufacturing chain along with their impact on devices. High kill rate of micropipes were seen on both Diodes and MOSFETs as expected. The purity of micropipe detection was found to be affected by the presence of inclusions. Inclusions were successfully sub-classified and separated out from micropipes, based on their location depth from the wafer surface. The effect on devices was found to relate to how deep the inclusion was located, with the ones at the surface having the biggest impact. Various sources of Stacking Faults (SFs) were reported, with Basal Plane Dislocations (BPDs) in the crystal being a major contributor. Higher local densities of BPDs were found to have a more detrimental effect. SFs were sub-classified using the wavelength of each peak. The effect of both overall SFs and each SF sub-type on devices was determined, each sub-type having different effect on the device. Various ways of mitigating the effects of defects and dislocations are demonstrated. Reducing killer defects, SF nucleation probability, and BPDs propagation by epitaxial process optimizations are shown. Resilience up to 3500A/cm² against bipolar degradation is demonstrated by using an engineered buffer layer. Process and device design optimizations show high resiliency against crystal and epi defects and dislocations, with improved yield and lower leakage.

Abstract: For a long time, rayon has been produced using dissolving pulp (DP). DP is typically made from wood or cotton, but it takes a long time to collect wood, and high-quality cotton must be imported from afar. Sansevieria trifasciata (ST) fiber, which contains more than 50% cellulose, offers potential as a raw material and a substitute for cotton and wood. It is simple to develop and grow. It can endure a wide range of light and temperature conditions. By using the water-pre-hydrolysis, soda-Anthraquinone cooking (soda-AQ), and elementary-chlorine-free (ECF) bleaching sequences, this work aims to convert ST into DP. Results, The DP was produced with a yield of 43.69%, a kappa value of 4.73, a viscosity of 9.3 cP, an alpha-cellulose content of 97.7% and a brightness of 90.7%, which was higher than the ISO brightness of 88%. The DP quality corresponds to the minimum DP level for rayon according to the Indonesian National Standard (SNI). It is very promising for further development, such as being used for viscose fiber production.

Abstract: This study focuses on the design and construction of an improved crushing machine with a capacity of 0.15 (150 kg/hr) tons per hour, 15 Hp, and 2910 rpm speed. The design follows criterion design guidelines to ensure the improved service life of the component. When the values produced from the current design approach were contrasted with the values and outcomes received from the analysis using the Ansys package, the design should be reliable. The hammers produced are subjected to carburisation process using bio-wastes such as coconut shells, saw dust, and palm kernel shells to enhance the reliability of the machine. The bending of the shaft is controlled during the rotation at rated speed rpm when a load is applied to the shaft. The critical speed of the shaft is experienced with deflection when the shaft rotates freely. The natural frequency and speed were put under check in order to avoid failure. The von Mises stress was employed as a yielding criterion for the shaft. It states that if the components of stress operating on a body are more than the criterion, the body will yield.

Abstract: Commercially available 4H-SiC substrate quality has improved over time, and this has extensively reduced defect concentration in the active epitaxial layer, during epi growth conditions at the interface. The objective of this work is to investigate bulk crystal quality for the purpose of future vertical power device fabrication in exfoliated, non-epitaxial, undoped material layers. Mathematical estimations on the device yield fraction, that is immune to bipolar degradation for the suggested future process were calculated based on XRT measurements to detect BPD and TSD densities on donor substrates. The full wafer BPD density maps of on-axis semi-insulating wafer substrates from two vendors were compared.

Abstract: For the ongoing commercialization of power devices based on 4H-SiC, increasing the yield and improving the reliability of these devices is becoming more and more important. In this investigation, gate oxide on 4H-SiC was examined by time-zero dielectric breakdown (TZDB) and constant current stress (CCS) time-dependent dielectric breakdown (TDDB) method in order to get insights into the influence of the epitaxial defects on the gate oxide performance and reliability. For that purpose, MOS capacitors with different gate oxides have been fabricated. Crystal defects in the epitaxial layers have been detected and mapped by ultraviolet photoluminescence (UVPL) and interference contrast (DIC) imaging. The results of the comparison of electrical data and surface mapping data indicate a negative influence on the leakage current behavior for some extended epitaxial defects. Results from TDDB measurement indicated numerous extrinsic defects, which can be traced back to gate oxide processing conditions and defect densities.