Enhancement of breakdown voltage for Ni-SiC Schottky diodes utilizing field plate edge termination

The silicon carbide (SiC) material is being spotlighted as a next-generation power semiconductor material due to the characteristic limitations of the existing silicon materials. SiC has a wider band gap, higher breakdown voltage, higher thermal conductivity, and higher saturation electron mobility than Si. However, actual SiC SBDs exhibit a lower dielectric breakdown voltage than the theoretical breakdown voltage that causes the electric field concentration, a phenomenon that occurs on the edge of the contact surface as in the conventional power semiconductor devices. In this paper, we designed an edge termination structure using a field plate structure through oxide etch angle control, and optimized the structure to obtain a high breakdown voltage. The experiment results indicated that oxide etch angle was 45° when the breakdown voltage characteristics of the SiC SBD were optimized and a breakdown voltage of 681V was obtained.

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High Voltage Silicon Carbide Devices

MRS Proceedings ◽

10.1557/proc-512-77 ◽

1998 ◽

Vol 512 ◽

Cited By ~ 22

Author(s):

B. Jayant Baliga

Keyword(s):

Silicon Carbide ◽

Breakdown Voltage ◽

High Voltage ◽

Impact Ionization ◽

Voltage Drop ◽

Schottky Diodes ◽

Inversion Layer ◽

Drift Region ◽

Edge Termination ◽

Silicon Devices

ABSTRACTProgress made in the development of high performance power rectifiers and switches from silicon carbide are reviewed with emphasis on approaching the 100-fold reduction in the specific on-resistance of the drift region when compared with silicon devices with the same breakdown voltage. The highlights are: (a) Recently completed measurements of impact ionization coefficients in SiC indicate an even higher Baliga's figure of merit than projected earlier. (b) The commonly reported negative temperature co-efficient for breakdown voltage in SiC devices has been shown to arise at defects, allaying concerns that this may be intrinsic to the material. (c) Based upon fundamental considerations, it has been found that Schottky rectifiers offer superior on-state voltage drop than P-i-N rectifiers for reverse blocking voltages below 3000 volts. (d) Nearly ideal breakdown voltage has been experimentally obtained for Schottky diodes using an argon implanted edge termination. (e) Planar ion-implanted junctions have been successfully fabricated using oxide as a mask with high breakdown voltage and low leakage currents by using a filed plate edge termination. (f) High inversion layer mobility has been experimentally demonstrated on both 6H and 4H-SiC by using a deposited oxide layer as gate dielectric. (g) A novel, high-voltage, normally-off, accumulation-channel, MOSFET has been proposed and demonstrated with 50x lower specific on-resistance than silicon devices in spite of using logic-level gate drive voltages. These results indicate that SiC based power devices could become commercially viable in the 21st century if cost barriers can be overcome.

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A semi-theoretical relationship between the breakdown voltage of field plate edge and field plate design in planar P–N junction terminated with finite field plate

Microelectronics Journal ◽

10.1016/s0026-2692(01)00053-2 ◽

2001 ◽

Vol 32 (9) ◽

pp. 763-767 ◽

Cited By ~ 3

Author(s):

Jin He ◽

Xing Zhang

Keyword(s):

Finite Field ◽

Breakdown Voltage ◽

Plate Edge ◽

Theoretical Relationship ◽

Field Plate ◽

Plate Design

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High Voltage Schottky Barrier Diodes on P-Type SiC using Metal-Overlap on a Thick Oxide Layer as Edge Termination

MRS Proceedings ◽

10.1557/proc-572-75 ◽

1999 ◽

Vol 572 ◽

Cited By ~ 3

Author(s):

Q. Zhang ◽

V. Madangarli ◽

S. Soloviev ◽

T. S. Sudarshan

Keyword(s):

Schottky Barrier ◽

Oxide Layer ◽

Breakdown Voltage ◽

Schottky Diodes ◽

Schottky Barrier Diodes ◽

Edge Termination ◽

Forward Current ◽

Current Voltage ◽

Thick Oxide Layer ◽

P Type

ABSTRACTP-type 6H SiC Schottky barrier diodes with good rectifying characteristics upto breakdown voltage as high as 1000V have been successfully fabricated using metal-overlap over a thick oxide layer (∼ 6000 Å) as edge termination and Al as the barrier metal. The influence of the oxide layer edge termination in improving the reverse breakdown voltage as well as the forward current – voltage characteristics is presented. The terminated Schottky diodes indicate a factor of two higher breakdown voltage and 2–3 times larger forward current densities than those without edge termination. The specific series resistance of the unterminated diodes was ∼228 mΩ-cm2, while that of the terminated diodes was ∼84 mΩ-cm2.

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High Voltage P-N Junction Diodes in Silicon Carbide Using Field Plate Edge Termination

MRS Proceedings ◽

10.1557/proc-572-81 ◽

1999 ◽

Vol 572 ◽

Author(s):

R. K. Chilukuri ◽

P. Ananthanarayanan ◽

V. Nagapudi ◽

B. J. Baliga

Keyword(s):

Breakdown Voltage ◽

Dielectric Material ◽

High Resistivity ◽

Leakage Currents ◽

Plate Edge ◽

Field Plate ◽

P Type ◽

Post Implantation ◽

Anneal Temperature ◽

Ion Implanted

ABSTRACTIn this paper, we report the successful use of field plates as planar edge terminations for P+-N as well as N+-P planar ion implanted junction diodes on 6H- and 4H-SiC. Process splits were done to vary the dielectric material (SiO2 vs. Si3N4), the N-type implant (nitrogen vs. phosphorous), the P-type implant (aluminum vs. boron), and the post-implantation anneal temperature. The nitrogen implanted diodes on 4H-SiC with field plates using SiO2 as the dielectric, exhibited a breakdown voltage of 1100 V, which is the highest ever reported measured breakdown voltage for any planar ion implanted junction diode and is nearly 70% of the ideal breakdown voltage. The reverse leakage current of this diode was less than 1×10−5 A/cm2 even at breakdown. The unterminated nitrogen implanted diodes blocked lower voltages (∼840V). In contrast, the unterminated aluminum implanted diodes exhibited higher breakdown voltages (∼80OV) than the terminated diodes (∼275V). This is attributed to formation of a high resistivity layer at the surface near the edges of the diode by the P-type ion implant, acting as a junction termination extension. Diodes on 4H-SiC showed higher breakdown than those on 6H-SiC. Breakdown voltages were independent of temperature in the range of 25 °C to 150 °C, while the leakage currents increased slowly with temperature, indicating surface dominated components.

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