Papers by Keyword: Breakdown Voltage

Abstract: This work reports enhanced high-voltage blocking capability and an enlarged process window for junction termination extension (JTE) in SiC power devices using a hybrid random and channeling implantation for p-type doping (Al), compared with conventional random-only implantation. A three-step hybrid implantation process has been developed to replace a nine-step random implantation, achieving a similar doping profile and equivalent breakdown voltage in the JTE while significantly increasing fabrication productivity and reducing cost. Moreover, TCAD studies reveal that when using the same number of steps and ion energies as the conventional random implantation method, the JTE realized by the channeling-incorporated hybrid approach enables an increased breakdown voltage and a widened dose window in SiC devices. This is attributed to a deeper Al distribution with a lower average concentration, which effectively alleviates electric field crowding.

Abstract: Shorter channel-length and thinner gate-oxide are required for the scaling of design pitch and improving device performance. We explored variations in the channel length and gate oxide thickness for 1700 V 4H-SiC based VDMOSFETs. A design of experiments was applied to cover multiple designs and process conditions. The final device results show that the shorter channel with thinner gate-oxide leads to better device performance including lower on-resistance, higher current and transconductance. However, an increase in the device leakage starts affecting the breakdown voltage thus limiting the scaling for given process conditions, such as Pwell and JFET implants.

Abstract: In this work, variations in the channel length and gate oxide thickness are studied for the design optimization of 3300 V 4H-SiC based VDMOSFETs. For this, a batch of 3 wafers was processed and tested for key device characteristics. The results indicate shorter channel length of 0.5 μm leads to an increase in the drain leakage current, thus affecting the breakdown voltage as well. The thinner gate oxide at 50 nm demonstrates better control of threshold voltage with no variations in the gate leakage current distribution as compared to 65 nm.

Abstract: Power transformers use mineral oil as an insulating liquid due to its excellent dielectric properties. However, mineral oil is a non-renewable resource and is toxic to the environment when leaked. The purpose of this research is to examine vegetable oil containing nanotitanium dioxide as a substitute for mineral transformer oil. Vegetable insulating oils are environmentally benign and have good breakdown voltage (BV) and high ignition points that can decompose naturally in the event of a leak. Nevertheless, the high viscosity of vegetable oil slows down the flow rate in the transformer cooling. To overcome this problem, the process of transesterification was used to produce soybean methyl ester (SBME). SBME is used as an insulating liquid including composite filler of titanium dioxide (TiO₂) nanoparticles. Electrical breakdown voltage (BV) tests were performed following ASTM D1816 standards. Results demonstrated that SBME has a greater BV than natural soybean oil. Also, the addition TiO₂ nanoparticles increases the BV of the SBME’s mixture. All cases of nanoparticle methyl ester (NPME) conducted in the experiments exhibited a BV higher than 28 kV which is well above the standard value.

Abstract: In this paper we study the feasibility of the design/fabrication of a vertical trench 4H-SiC Junction Field Effect Transistor (JFET), assuming realistic constraints of the depth of the P+ implantation. The P+ doping profile is obtained using a Monte Carlo implantation simulation. The calculation used a drift-diffusion approach. The JFET aims to achieve a threshold voltage of-3V. We found that this constraint in concomitance with the proposed structure limits the breakdown voltage to approximately 200V. This is the result of a premature breakdown induced by short channel effects, namely Drain Induced Barrier Lowering (DIBL). However, a negative increase in the gate bias represses this short channel effect and improves the breakdown voltage to roughly 1800V. At this gate bias, the breakdown is induced by reaching the critical field strength of 4H-SiC at the gate P+/N junction, which causes avalanche generation of carriers. In addition, we have calculated the dependence of the threshold voltage on the drift doping and pillar width. This work also shows the vulnerability of the design to random fluctuation in the doping profile.

Abstract: A systematic experimental study is conducted on floating field rings (FFR) incorporated into 4H-SiC junction barrier Schottky (JBS) diodes across four voltage ratings 650, 1200, 1700 and 3300V, in pursuit of highly efficient FFR designs. 30 designs of FFR in 3 categories are studied for each voltage rating, and the measured breakdown voltage (Vbr) of JBS divided by ring system width (W) is taken as the figure of merit (FOM) of each design. The influence of ring spacing, ring width and number of rings on Vbr is studied in detail. It is found that the initial ring spacing (S1) is critical in determining the highest Vbr achievable by a certain design, and its optimum value increases as voltage rating increases. TCAD simulation verifies the importance of S1. For designs with a small ring system width, subsequent ring spacing can also become important. Ring width does not have a definitive effect, and Vbr saturates beyond a certain ring number. The design with the highest Vbr may not render the highest FOM. Even style designs with appropriate ring spacings can be advantageous likely due to less susceptibility to variation of field oxide charge, and more tolerance to fabrication error, as well as ease of design.

Abstract: In order to expand the possibilities of practical application of polymeric materials we studied syndiotactic 1,2-polybutadiene (1,2-SPB). The experimental procedure and the MV-002 device for determining the breakdown voltage and electrical breakdown of a polymer are described in detail. Mathematical models of the dependence of the breakdown voltage of the polymer on the frequency and magnitude of the electrical breakdown of the polymer on the thickness of the sample have been built and studied. Regression analysis was used for mathematical data processing. The reliability of the results obtained is proved by the methods of test statistics.

Abstract: – The research on CPO as an insulator to replace mineral oil. The CPO was heated using vacuum distillation technology. The parameters used are the temperature of 110°C to 170°C with the difference of 10°C and the vacuum pressure of 0 mmHg to-600 mmHg with the difference of 200 mmHg. The highest breakdown voltage measurement of 49 kV (170°C-600 mmHg), the lowest viscosity is 20 mPas (170°C-600 mmHg), the lowest water content was obtained at 30 (160°C-400 mmHg). The vacuum pressure and temperature rise causes the high breakdown voltage and viscosity are high and the water content is low. The relationship between vacuum pressure and breakdown voltage is y = 5.8 x + 7 with R² of 0.9397, the viscosity is y = -2x + 35.67 with R² of 0.9231 and the water content is y=-7.25x2 + 22.95x + 106.75 with R² of 0.9945.

Abstract: Breakdown voltage happens when an electrically insulating material, exposed to a sufficiently high voltage, then instantly becomes an electrical conductor, and flows through it with electrical current. However, a high breakdown voltage would give a low-power efficiency which is bad for Switched Mode Power Supply (SMPS) devices. Also, it would lead to low efficiency. Therefore, a low efficiency leads to a bad system’s performance, and the switching characteristics would also decrease. This in return, cannot be applied to power electronics such as switching devices. Therefore, this work focused on decreasing the breakdown voltage in a DC-DC converter for a step-down chopper circuit or buck converter. The simulation of the circuit is done by using the LTSpice software. The parameters varied are the input voltage, capacitor, and duty cycle. The input voltage supplied to the circuit is 12V and the output voltage obtained is half of the input voltage at the steady-state response. Where this proves the decrement of the breakdown voltage in the chopper circuit.

Abstract: Mineral oil has been used as electrical insulation for a long time due to its availability, excellent cooling and dielectric property. However, petroleum sources are nonrenewable, and it is depleting. Vegetable insulating oil is an alternative since it is renewable, environment-friendly, biodegradable, high fire-point, and has a good electrical breakdown voltage level. These properties can make vegetable insulating oil as a replacement for mineral oil that is going to be limited in availability. Nevertheless, vegetable insulating oil have high viscosity, leading to a slow flow rate on the cooling performance. This research is to investigate the breakdown voltage of palm oil-based liquid insulators. This liquid is palm oil methyl esters-based nanofluids (NPME) that was converted from the transesterification process to reduce viscosity and mixed with graphene nanoparticles. These nanofluids were also aged by thermal aging at 100 °C for 168, 336 and 504 hours before testing for their electrical breakdown voltage. The results show that the transesterification process can reduce the viscosity of palm oil by about 6.6 times. Also, the breakdown voltage of nanofluids is higher than bare palm oil methyl ester after thermal aging for 504 hours.