High-voltage Ni- and Pt-SiC Schottky diodes utilizing metal field plate termination (original) (raw)

Development of process technology for fabrication of 4H-SiC silicon carbide schottky barrier diodes

In recent times, 4H-SiC has been at the center of power semiconductor device research due to its superior material properties such as large bandgap (E g ~3.26 eV), high breakdown electric field (E c ~3 MV/cm which is almost 10 times that of Si), high saturated electron velocity (~2.0×10 7 cm/s which is almost 2 times that in Si), high thermal conductivity (K ~4.9 W/cm.K) and most importantly ability to form a stable native oxide SiO 2. Schottky barrier diodes (SBDs) based on 4H-SiC offer superior dynamic performance (<20 nC reverse recovery charge for a 1200 V, 1A SBD), almost 100 times lower specific-on resistance compared to Si SBDs and PiN diodes. The higher bandgap results in much higher schottky barrier height compared to Si and GaAs resulting in extremely low leakage currents even at elevated temperatures (>300 o C operation). Edge termination and passivation is a critical technology for power devices to fully realize their voltage blocking potential. The objective of this research was to develop the process technology for fabrication of high voltage 4H-SiC SBDs. We decided to use a simple edge termination technique based on Field-Plate (FP) termination. The simplicity of FP termination lies in the fact that unlike other termination techniques such as guard rings, mesa and Junction Termination Extensions (JTE), it does not need high temperature ionimplantations. Such high temperature implantation requires the substrate to be maintained at 700-1000 o C during implantation. It also needs subsequent extreme high temperature anneals in excess of 1500 o C to reduce implantation damage. There are also design issues such as the need to optimize ring spacing. FP termination technique has long been a power horse of Si power device technology using thick SiO 2 field oxide and poly silicon as electrode overlapping the oxide. For past decade or so since its first application to SiC power device ATTENTION: The Singapore Copyright Act applies to the use of this document. Nanyang Technological University Library XI 6.5.3 Electric Field profile of FP terminated 4H-SiC SBDs along the schottky edge with 2-step Breakdown………………………………. 6.6 Conclusions………………………………………………………………. 7. Conclusions and Recommendations for Future Work………………………… 7.1 Conclusions………………………………………………………………. 7.2 Recommendations for Future Work…………………………………….

Current Voltage Characteristics of High-Voltage 4H Silicon Carbide Diodes

Materials Science Forum, 2000

+-n 0-n + 4H-SiC diodes with homogeneous avalanche breakdown at 1860 V are fabricated. The pulse current-voltage characteristics are measured in the avalanche-breakdown mode up to a current density of 4000 A/cm 2. It is shown that the avalanche-breakdown voltage increases with increasing temperature. The following diode parameters are determined: the avalanche resistance (8.6 × 10-2 Ω cm 2), the electron drift velocity in the n 0 base at electric fields higher than 10 6 V/cm (7.8 × 10 6 cm/s), and the relative temperature coefficient of the breakdown voltage (2.1 × 10-4 K-1).

Junction barrier Schottky diodes in 6H SiC

Solid-State Electronics, 1998

AbstractÐJunction barrier Schottky (JBS) diodes in 6H SiC have been fabricated and characterised electrically. This device, demonstrated in silicon technology, has the advantage of a low forward voltage drop comparable to that of Schottky diodes, as well as a high blocking voltage and low reverse leakage current of a pn junction. This is especially attractive for wide bandgap materials such as SiC in which pn junctions have a large forward voltage drop. The devices were capable of blocking up to 1100 V with a leakage current density of 0.15 A cm À2 , limited by the leakage when the drift region was fully depleted, or breakdown of the SiC material itself. The forward conduction was limited by an onresistance of 20 mO cm 2 , resulting in forward voltage drops of 2.6 V at 100 A cm À2 . #

Study of 6H–SiC high voltage bipolar diodes under reverse biases

Applied Surface Science, 2001

Silicon carbide presents electrical properties suitable for many applications especially for high voltage devices. 6H-SiC P þ NN þ structures have been fabricated following ISE software simulations in order to block voltages as high as 1.5 kV. In particular, these diodes are realized by surrounding the emitter by a p-type region called junction termination extension (JTE). Electrical characterizations under reverse bias at room temperature and in various environments (air, silicone oil) show a premature breakdown for the protected diodes. This breakdown is localized at the emitter periphery. Optical beam induced current (OBIC) measurements show a peak of photocurrent at the junction edge, indicating the presence of a high electric field. These results show a protection efficiency of 60% of the JTE. An electrical activation of the aluminum dopants implanted in the JTE around 30% is derived from the analysis of the presented results. # 2001 Published by Elsevier Science B.V.

Planar edge termination design and technology considerations for 1.7-kV 4H-SiC PiN diodes

2005

This paper presents the design, fabrication, and comparison of different planar edge termination techniques on high-voltage 4H-SiC PiN diodes, including single-and double-junction termination extensions (JTE), floating guard rings, and a novel termination structure, the so-called "floating guard rings-assisted JTE." The influence of the anode metal edge location over different periphery regions on the breakdown voltage is also discussed, as well as the effect of a field plate and the passivation layer on the reverse characteristics. The terminations were studied by way of two-dimensional numerical device simulations and they are confirmed by fabricating and measuring 1.7-kV 4H-SiC aluminum implanted PiN diodes. It is shown that the novel termination structure provides the best results achieving the highest breakdown voltages with good production yield. The fabricated diodes also exhibited excellent forward current characteristics with a low on-state voltage drop of 3.0 V at 100 A/cm 2 , thanks to the low specific contact resistivity achieved (= 1 10 5 cm 2) after the high-temperature treatment of the anode contact. High-temperature reverse current-voltage measurements were also carried out and are presented and discussed. Index Terms-Electric breakdown, high-power semiconductor diodes, p-in diode, silicon carbide (SiC). I. INTRODUCTION S ILICON CARBIDE (SiC) as a base material for highpower, high-temperature, and high-frequency devices has demonstrated its great potential over the past recent years. The physical background of this potential is given by its superior material properties such as wide bandgap, high breakdown electric field, high thermal conductivity, and high-saturation electron drift velocity [1]. Important for power devices, the 10 increase in critical electric field of SiC allows high-voltage blocking layers to be approximately 10 thinner than those of Si-based devices, thus reducing the device on-resistance and power losses while maintaining the same high blocking capability. Unfortunately, breakdown voltages for planar junctions suffer from an acute reduction due to the well-known device edge field crowding effect [2], limiting the potential performance of

Characteristics of Ni/SiC Schottky diodes grown by ICP-CVD

Solid-state Electronics, 2006

A Ni/SiC Schottky diode was fabricated with an a-SiC thin film grown by the inductively coupled plasma chemical vapor deposition, ICP-CVD method on a (1 1 1) Si wafer. The a-SiC film was grown on a carbonized Si layer that the Si surface had been chemically converted to a very thin SiC layer by the ICP-CVD method at 700°C. To reduce defects between the Si and a-SiC, the surface of the Si wafer is slightly carbonized. The film characteristics of a-SiC were investigated by employing TEM and FT-IR. A sputtered Ni thin film was used for the anode metal. The boundary status of the Ni/SiC contact was investigated by AES as a function of annealing temperature. It is shown that the ohmic contact could be acquired below 1000°C annealing temperature. The forward voltage drop of the Ni/a-SiC Schottky diode is 1.0 V at 100 A/cm 2 . The breakdown voltage is 545 V which is five times larger than the ideal breakdown voltage of a silicon device. Also, the dependence of barrier height on temperature was observed.

Dynamic behavior of Ti/4H-SiC Schottky diodes

2012 16th IEEE Mediterranean Electrotechnical Conference, 2012

The wide band gap (3.2 eV) allows the silicon carbide (SiC) to work at high temperatures with high voltages and currents, to switch large power densities and reduce losses. The 4H-SiC polytype is the most widely used material for electronic applications. Despite the development of manufacturing technology of SiC wafers, this material has structural defects, such as micropipes, dislocations and inclusions of polytypes. In this paper, the defects and dynamic performance of the SiC Schottky diodes is studied and the obtained maximum reverse voltage is 600V. The reverse recovery time is evaluated to 135ns. The results demonstrate the effectiveness of the SiC devices in reducing the overall system losses generated by switching transitions compared to silicon based diodes. We introduced the parameters found in the Ti/4H-SiC Schottky diode in the Pspice model for simulation. We compared these results with the model using Matlab-Simulink to see the behavior of the switching cell and to deduce the equivalent circuit of diode in dynamic transitions.