4H-SiC Junction Barrier Schottky Diodes Research Articles

Investigation of Stacking Faults Affecting on Reverse Leakage Current of 4H-SiC Junction Barrier Schottky Diodes Using Device Simulation

We clarified the relationship between the enhanced leakage current of SiC Junction Barrier Schottky diodes and the stacking faults in the SiC crystal at the SiC and metal electrode interface by measuring the electrical and optical properties, and confirm by using the numerical simulations. Numerical simulation considering local lowering of Schottky barrier height, which is 0.8 eV lower than that of 4H-SiC well explained the 2-4 orders of magnitude higher reverse leakage current caused by the SFs. We concluded that the locally lowering of the Schottky barrier height at the 3C-SiC layer in the 4H-SiC surface is a main cause of the large reverse leakage current.

Development of 1000V SiC JBS Diodes

High voltage 4H-SiC Ni Schottky junction barrier schottky (JBS) diode with breakdown voltage of 1000V and forward current of 1A has been fabricated. A low reverse leakage current below 4.7×10-6A/cm2 at the bias voltage of-1000V has been obtained. The forward on-state current was 1A at VF = 2.2V. The chip is 1.3mm×1.3mm. The turn-on voltage is about 1.4V. The on-state resistance is 14.5mΩ·cm2. The doping and thickness of the N-type drift layer and the device structure have been performed by numerical simulations. The SiC JBS devices have been fabricated and the processes were in detail. The die was assembled in a SMB package. The thickness of the N-epilayer is 10μm, and the doping concentration is 4×1015cm3. A floating guard rings edge termination have been used to improve the effectiveness of the edge termination technique. By using WTi/Au multilayer metal structure, the double side Au process of 4H-SiC JBS diode is formed. We use the PECVD SixNy/SiO2 as the passivation dielectric and a non photosensitive polyamide as the passivation in the end.

High-performance 4H-SiC junction barrier Schottky diodes with double resistive termination extensions

4H-SiC junction barrier Schottky (JBS) diodes with a high-temperature annealed resistive termination extension (HARTE) are designed, fabricated and characterized in this work. The differential specific on-state resistance of the device is as low as 3.64 mΩ·cm2 with a total active area of 2.46 × 10−3 cm2. Ti is the Schottky contact metal with a Schottky barrier height of 1.08 V and a low onset voltage of 0.7 V. The ideality factor is calculated to be 1.06. Al implantation annealing is performed at 1250°C in Ar, while good reverse characteristics are achieved. The maximum breakdown voltage is 1000 V with a leakage current of 9 × 10−5 A on chip level. These experimental results show good consistence with the simulation results and demonstrate that high-performance 4H-SiC JBS diodes can be obtained based on the double HARTE structure.

4.5kV SiC JBS Diodes

High voltage 4H-SiC junction barrier schottky (JBS) diode with breakdown voltage higher than 4.5 kV has been fabricated. The doping level and thickness of the N-type drift layer and the device structure have been performed by numerical simulations. The thickness of the device epilayer is 50 μm, and the doping concentration is 1.2×1015 cm3. A floating guard rings edge termination has been used to improve the effectiveness of the edge termination technique. The diodes can block a reverse voltage of at least 4.5 kV, and the on-state current density was 80 A/cm2 at VF =4 V.

Application of 1200V-8A SiC JBS Diodes in the Motor System

1200V-8A 4H-SiC junction barrier schottky (JBS) diodes were designed and fabricated based on in-house SiC epitaxy and device technology. As a free-wheeling diode for the IGBT in inverter of motor system, the 1200V SiC JBS diode was compared to the Si ultra-fast diode from Fairchild Co. Ltd. The SiC diode achieved 88% recovery loss reduction and corresponding IGBT showed 35% lower turn-on loss. So, it will promote the application of motor system in high frequency and high efficiency.

Effect of Stacking Faults in Triangular Defects on 4H-SiC Junction Barrier Schottky Diodes

The relationship between stacking faults and the position of the leakage current inside a triangular defect was analyzed. Triangular defects are categorized into two types on the basis of the current–voltage (I–V) characteristics. It was found that stacking faults (SFs) of the 3C structure inside a triangular defect increase leakage current at a reverse bias voltage as well as forward current at a low bias voltage, while SFs of the SF(4,2) structure inside a triangular defect do not lead to deterioration of device performance in this case.

Reverse Leakage Currents in High-Voltage 4H-SiC Schottky Diodes

High-voltage 4H-SiC Schottky Barrier Diodes (SBDs) and Junction Barrier Schottky (JBS) diodes have been fabricated and evaluated. Current-voltage (I-V) characteristics were measured in a wide temperature range. All diodes fabricated showed nearly ideal forward behavior. For SBDs with Schottky Barrier Height (SBH) of 1.12 eV, the reverse I–V characteristics are described well by the thermionic emission model (at voltages varying from several mV to 2 kV and temperatures ranging from 361 to 470 K) if barrier lowering with increasing band bending is taken into account. For SBDs with SBH of 1.53 eV, no thermionic current was detected in reverse direction at temperatures below ~500 K. The leakage currents appeared only at high reverse voltages and elevated temperatures. The analysis of reverse I-V characteristics allowed to propose dislocation related mechanism of current flow due to the local injection of electrons from metal to semiconductor. It is shown that defect related leakage currents can be significantly reduced by JBS-structure.

Temperature-dependent characteristics of 4H—SiC junction barrier Schottky diodes

The current—voltage characteristics of 4H—SiC junction barrier Schottky (JBS) diodes terminated by an offset field plate have been measured in the temperature range of 25–300 °C. An experimental barrier height value of about 0.5 eV is obtained for the Ti/4H—SiC JBS diodes at room temperature. A decrease in the experimental barrier height and an increase in the ideality factor with decreasing temperature are shown. Reverse recovery testing also shows the temperature dependence of the peak recovery current density and the reverse recovery time. Finally, a discussion of reducing the reverse recovery time is presented.

High Temperature Capability of High Voltage 4H-SiC JBS

This paper presents the high blocking capability of the 4H-SiC tungsten Schottky and junction barrier Schottky (JBS) diodes at room temperature as well as at high operating temperature. First, we present the design of the proposed devices and the process employed for their fabrication. In a second part, their forward and reverse characteristics at room temperature will be presented. Our rectifiers exhibit blocking capability up to 9kV at room temperature. Then, we investigate the reverse current behaviour at 5kV from room temperature to 250°C under vacuum. JBS and Schottky devices that are capable to block 8kV at room temperature, show leakage current inferior to 100µA at 250°C when reverse biased at 5kV. It confirms the capability of Silicon Carbide to produce devices capable of operation at temperatures and voltages above the Silicon limits.

Study of the effect of lithography deviation on 4H-SiC floating junction junction barrier Schottky diode

The breakdown voltage of 4H-SiC junction barrier schottky diode with floating junction is larger than that of traditional junction barrier Schottky diode under the condition of the same fixed on-resistance. It is a crucial technology that the alignment of lithography between p+ region of floating junction and main junction. The simulation results obtained using two-dimensional simulator ISE show that the breakdown voltage obviously drops with the deviation of lithography increasing. Although the breakdown characteristics of the dislocation and the alignment structure are similar, the series resistance of the dislocation structure is larger than the latter when the forward voltage is larger than 2 V.

Edge termination study and fabrication of a 4H-SiC junction barrier Schottky diode

The 4H-SiC junction barrier Schottky (JBS) diodes terminated by field guard rings and offset field plate are designed, fabricated and characterized. It is shown experimentally that a 3-μ P-type implantation window spacing gives an optimum trade-off between forward drop voltage and leakage current density for these diodes, yielding a specific on-resistance of 8.3 mΩ·cm2. A JBS diode with a turn-on voltage of 0.65 V and a reverse current density less than 1 A/cm2 under 500 V is fabricated, and the reverse recovery time is tested to be 80 ns, and the peak reverse current is 28.1 mA. Temperature-dependent characteristics are also studied in a temperature range of 75 °C-200 °C. The diode shows a stable Schottky barrier height of up to 200 °C and a stable operation under a continuous forward current of 100 A/cm2.

Study of 4H-SiC JBS Diodes Fabricated with Tungsten Schottky Barrier

Tungsten is a suitable metal contact for high-temperature applications. We fabricated 1.7-kV and 6-kV 4H-SiC junction barrier Schottky (JBS) diodes with a tungsten Schottky contact with different geometries, and their forward characteristics were measured up to 300°C. The 1.7-kV diodes exhibited unipolar conduction up to 6 V at 275°C, whereas 6-kV diodes showed ideal on-resistance, Ron. An optimized JBS design permits a higher breakdown voltage to be obtained than for the pure Schottky diode, with a reasonable increase (10%) of the on-resistance. Results demonstrate the feasibility of tungsten JBS diodes for fast-switching, high-voltage, and high-temperature applications.

Fabrication and characteristics of a 4H-SiC junction barrier Schottky diode

4H-SiC junction barrier Schottky (JBS) diodes with four kinds of design have been fabricated and characterized using two different processes in which one is fabricated by making the P-type ohmic contact of the anode independently, and the other is processed by depositing a Schottky metal multi-layer on the whole anode. The reverse performances are compared to find the influences of these factors. The results show that JBS diodes with field guard rings have a lower reverse current density and a higher breakdown voltage, and with independent P-type ohmic contact manufacturing, the reverse performance of 4H-SiC JBS diodes can be improved effectively. Furthermore, the P-type ohmic contact is studied in this work.

Effects of Surface and Crystalline Defects on Reverse Characteristics of 4H-SiC Junction Barrier Schottky Diodes

To clarify the relationship between the dispersed reverse characteristics of 4H-SiC junction barrier Schottky (JBS) diodes and defects, we investigated the sensitivity of the reverse characteristics to surface and crystalline defects in 4H-SiC epitaxial layers. Strong correlations were obtained between the reverse characteristics of 4H-SiC JBS diodes and surface defects. Micropipes or particles reduced blocking voltage and carrot defects increased leakage current. Furthermore, the leakage current of 4H-SiC JBS diodes depends on the etch pit density of threading dislocations (TDs). Etch pits formed from TDs increased leakage current by about 10-9 A in samples without surface defects. In addition, hexagonal etch pits formed from unusual crystalline defects were observed; they also increased leakage current.

Effects of Surface and Crystalline Defects on Reverse Characteristics of 4H-SiC Junction Barrier Schottky Diodes

To clarify the relationship between the dispersed reverse characteristics of 4H-SiC junction barrier Schottky (JBS) diodes and defects, we investigated the sensitivity of the reverse characteristics to surface and crystalline defects in 4H-SiC epitaxial layers. Strong correlations were obtained between the reverse characteristics of 4H-SiC JBS diodes and surface defects. Micropipes or particles reduced blocking voltage and carrot defects increased leakage current. Furthermore, the leakage current of 4H-SiC JBS diodes depends on the etch pit density of threading dislocations (TDs). Etch pits formed from TDs increased leakage current by about 10-9 A in samples without surface defects. In addition, hexagonal etch pits formed from unusual crystalline defects were observed; they also increased leakage current.

600V-30A 4H-SiC JBS and Si IGBT Hybrid Module

600V-30A 4H-SiC Junction Barrier Schottky（JBS）diodes were designed and fabricated using SiC epitaxy and device technology. SiC JBS diodes were packaged in Si IGBT module，and switching measurements were done at 125°C. As free-wheeling diode for Si IGBT, 600V SiC JBS diode was compared to 600V ultra-fast diode from International Rectifier. SiC diode achieved 90% recovery loss reduction and corresponding IGBT showed 30% lower turn-on loss. However, SiC JBS diode has larger on-state voltage drop due to small chip area. On-state power loss will be lowered by increasing SiC chip area.

Study of 4H-SiC junction barrier Schottky diode using field guard ring termination

This paper reports that the 4H-SiC Schottky barrier diode, PiN diode and junction barrier Schottky diode terminated by field guard rings are designed, fabricated and characterised. The measurements for forward and reverse characteristics have been done, and by comparison with each other, it shows that junction barrier Schottky diode has a lower reverse current density than that of the Schottky barrier diode and a higher forward drop than that of the PiN diode. High-temperature annealing is presented in this paper as well to figure out an optimised processing. The barrier height of 0.79 eV is formed with Ti in this work, the forward drop for the Schottky diode is 2.1 V, with an ideality factor of 3.2, and junction barrier Schottky diode with blocking voltage higher than 400 V was achieved by using field guard ring termination.

Influence of Lateral Spreading of Implanted Aluminum Ions and Implantation-Induced Defects on Forward Current–Voltage Characteristics of 4H-SiC Junction Barrier Schottky Diodes

Forward current density (JF)-forward voltage (VF) characteristics are experimentally and computationally investigated for 4H-silicon carbide junction barrier Schottky (JBS) diodes with a lightly doped (3 - 5 times1015 cm-3) drift layer and 2-mum-wide p+ stripe regions separated by 1 mum. The JF-VF characteristics of fabricated JBS diodes are compared with those of Schottky barrier diodes simultaneously fabricated on the same epitaxial wafers. These JF-VF characteristics are also compared with those of simulated JBS diodes, assuming boxlike and Monte Carlo-simulated profiles of aluminum. In the simulation of aluminum ion implantation, concentration contours of created interstitials and vacancies are calculated, and their influence on the JF-VF characteristics of JBS diodes is discussed in terms of degradation of electron mobility in the surface region of the drift layer.

Characterization of 4H-SiC Junction Barrier Schottky Diodes by Admittance vs Temperature Analyses

Schottky barrier diodes and junction barrier Schottky diodes are investigated by thermal admittance spectroscopy, and by Capacitance-Voltage measurements. Samples are protected with surrounding junction termination extension and p+ ring. Temperature dependence of the doping level is first calculated. Then admittance spectra allow detecting defects and extracting their activation energies and capture cross sections. Results seem to indicate the presence of interfacial defects and defects due to the implantation process.

Effect of the Doping Concentration and Space of Both p-Grid and Field Limiting Ring on 4H-SiC Junction Barrier Schottky Diode with Single Ion Implantation Process

The effect of the doping concentration and space of both p-grid and FLR on the electrical performances of 4H-SiC JBS diode has been investigated. A 4H-SiC JBS diode with the p-grid space of 3um, the FLR space of 3um, and the doping concentration of 5E18cm-3 showed the highest blocking voltage of 1500V.