The Optimization of 3.3 kV 4H-SiC JBS Diodes

Arne Benjamin Renz,Vasantha Pathirana,Peter Michael Gammon,Phil Mawby,Vishal Ajit Shah,Guy William Clarke Baker,Yogesh Sharma,Tanya Trajkovic,Yegi Bonyadi,Marina Antoniou,Oliver James Vavasour

doi:10.1109/ted.2021.3129705

Abstract

The article reports a comprehensive study optimizing the OFF- and ON-state characteristics of 3.3 kV junction barrier Schottky (JBS) diodes made using nickel, titanium, and molybdenum contact metals. In this design, the same implants used in the optimized termination region are used to form the P-regions in the JBS active area. The width and spacing of the P-regions are varied to optimize both the ON- and OFF-state of the device. All the diodes tested displayed high blocking voltages and ideal turn-on characteristics up to the rated current of 2 A. However, the leakage current and the Schottky barrier height (SBH) were found to scale with the ratio of Schottky to p + regions. Full Schottkys, without p + regions, and those with very wide Schottky regions had the lowest SBH (1.61 eV for Ni, 1.11 eV for Mo, and 0.87 eV for Ti) and the highest leakage. Those diodes with the lowest Schottky openings of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2 ~\mu \text{m}$ </tex-math></inline-formula> had the lowest OFF-state leakage, but they suffered severe pinching from the surrounding p + regions, increasing their SBH. The best performing JBS diodes were Ni and Mo devices with the narrowest pitch, with the p + implants/Schottky regions both <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2 ~\mu \text{m}$ </tex-math></inline-formula> wide. These offered the best balanced device design, with excellent OFF-state performance, while the Schottky ratio guaranteed a relatively low forward voltage drop.

Highlights

R ECENT progress in growth and processing technology has made wide bandgap semiconductor materials realisticManuscript received September 25, 2021; revised November 1, 2021; accepted November 17, 2021
We demonstrate a comprehensive study to optimize the use of the junction barrier Schottky (JBS) technology for the 3.3 kV blocking voltage range by improving both the termination structure and the active area of the devices, offering a novel and industrially relevant approach to using the advantages of both bipolar and unipolar device action
While interfacial formation of silicides or carbides in Mo has been shown to be very unlikely [15], the partial formation of these at 500 ◦C is possible in Ni [27] and Ti [28]–[30] silicon carbide (SiC) Schottky barrier diodes (SBDs) and could be related to the inhomogeneity in the Ti systems while being the source of reliable Ni Schottky contacts [27]

Summary

Introduction

R ECENT progress in growth and processing technology has made wide bandgap semiconductor materials realisticManuscript received September 25, 2021; revised November 1, 2021; accepted November 17, 2021. Due to its availability on large-diameter wafers (up to 150 mm), in combination with relatively low defect densities, silicon carbide (SiC)is the most widely developed wide bandgap semiconductor material [1]. Since the first SiC diodes were commercially available in 2001, Schottky barrier diodes (SBDs) and MOSFETs have penetrated the power device market and are offered by a wide range of suppliers, providing faster switching, better thermal robustness, and increased efficiency when compared with their bipolar Si counterparts [2], [3]. The materials used for ultrahigh voltage applications (≥3.3 kV) such as traction, static VAR compensation, and high-voltage direct current (HVDC) is the focus of extended research activities, where multiple unipolar and bipolar switches with blocking voltages up to and exceeding 20 kV have been successfully demonstrated [4]

Results

Discussion

Conclusion