Abstract: This paper describes process and device simulation results of SiC floating junction
Schottky barrier diodes (Super-SBDs). Two-dimensional process simulation of a SiC device is implemented using the customized ISE’s process simulator “DIOS”. The simulation results reproduce the experimentally observed buried floating junction structure of a SiC Super-SBD. The device simulation method using the anisotropic impact ionization coefficients is formulated. The effect of
anisotropic avalanche breakdown field on termination structures of SiC SBDs is examined. Finally, by the device simulation we have shown that the trade-off between the on-state resistance and the breakdown voltage of the super-SBD that contains two drift layers exceeds that of the conventional SBD.
Abstract: Other than open micropipes (MP), overgrown micropipes do not necessarily lead to a^significantly reduced blocking capability of the affected SiC device. However they can lead to a degradation of the device during operation. In this paper the physical structure of overgrown micropipes will be revealed and their contribution to the leakage current will be shown. The possible impact of the high local power dissipation in the surrounding of the overgrown micropipe will be discussed and
long term degradation mechanisms will be described. Failure simulation under laboratory conditions shows a clear correlation between the position of overgrown micropipes and the location of destructive burnt spots.
Abstract: SiC 600 V Schottky barrier diodes (SBD) are already available in the market and 1.2 kV have been announced. As the highest market for power devices is foreseen for blocking voltages in the range of 600 up to 1700V, we have developed 1.2kV SBDs. In this paper we report the latest results obtained on those diodes, underlining their high temperature working operation capability (up to 200°C). Forward characteristics, reverse leakage current and switching recovery time
dependence on temperature have been analysed. The good thermal behaviour of the 1.2 kV SiC SBDs is compared with that of ultra-fast PN-Si diodes (RHRP8120) of the same breakdown voltage.
Abstract: The static and dynamic electrical characterization of power Schottky rectifiers both with Ti and Ni2Si as Schottky metals having low negative coefficient of the breakdown voltage versus temperature will be presented in this paper. The values of the barrier height are respectively 1.28eV and 1.68eV, as extracted using the Tung’s model for inhomogeneous contacts from forward currentvoltage
characteristics. These values were found to be in good agreement with those obtained by means of capacitance-voltage measurements. The breakdown voltage shows an almost linear dependence from the temperature for both types of devices. The extracted coefficients are respectively -0.08V/°C and -0.11V/°C, thus guarantying stable and reliable behaviour. Very short reverse recovery time at RT and at 125°C confirms the good thermal stability of these devices.
Abstract: Planar microwave Schottky diodes on 4H-SiC have been designed, processed and
measured. Different Schottky metals were tested to study the influence on the microwave performance. A maximum extrinsic cut-off frequency of 30.8GHz was achieved for a Tungsten/SiC-Schottky diode. The diode geometry dependence on both the cut-off frequency and the breakdown voltage was investigated. The breakdown voltage was found to be linearly dependent on the anode-cathode distance.
Abstract: We present a theoretical and experimental study on the design, fabrication and
characterization of Schottky Barrier Diodes (SBD) on commercial 4H-SiC epitaxial layers. Numerical simulations were performed with a commercial tool on different edge termination structures, with the aim of optimizing the device behavior. For each termination design, SBD were fabricated and characterized by means of electrical measurements vs. temperature. Simulations provided also useful data for the assessment of the device process technology.
Abstract: In this work we demonstrate performant characteristics of 1.2KV Schottky, Junction
Barrier Schottky (JBS) and implanted PN diodes processed on the same 4H-SiC wafer. A bi-layer Ni/Ti scheme for the contact metallisation submitted to high temperature rapid thermal anneals is proved to form good ohmic contact on p+ implanted areas while maintaining good Schottky characteristics on lightly doped n-type regions. I-V characteristics have been evaluated from room temperature up to 560K. At room temperature, Schottky diodes have slightly better specific onresistance, but when working temperature is increased, the JBS diode exhibits better characteristics due to the temperature dependent activation of bipolar current injection from the p+ grid. From reverse measurements, the JBS diodes showed lower leakage current and higher breakdown voltages in comparison to that of the Schottky diodes in the whole range of temperatures.
Abstract: We demonstrate a new high-voltage p+ Si/n- 4H-SiC heterojunction diode (HJD) by numerical simulation and experimental results. This HJD is expected to display good reverse recovery because of unipolar action similar to that of a SiC Schottky barrier diode (SBD) when forward biased. The blocking voltage of the HJD is almost equal to the ideal level in the drift region of n- 4H-SiC. In addition, the HJD has the potential for a lower reverse leakage current compared with the SBD. A HJD was fabricated with p+-type polycrystalline silicon on an n--type epitaxial layer of 4H-SiC. Measured reverse blocking voltage was 1600 V with low leakage current. Switching characteristics of the fabricated HJD showed nearly zero reverse recovery with an inductive load circuit.
Abstract: In this paper, we extend the super junction concept to SiC high voltage devices and
further expand the SiC theoretical limit. It is shown that the super-junction concept can reduce the theoretical specific on-resistance by several times to several orders of magnitude for both silicon and SiC. The unique merit of SiC super-junction devices is that the required P and N pillars have a much smaller aspect ratio and may be easier to form than their silicon counterparts. Furthermore,
SiC super-junction devices are much less sensitive to charge imbalance issue than silicon SJ devices.