Abstract
Silicon carbide is a wide band gap semiconductor which presents excellent physical properties such as a high critical electric field strength which enables the realisation of efficient power devices [1]. The cubic silicon carbide (3C-SiC) polytype has been less investigated than the more popular hexagonal structure 4H-SiC. 3C-SiC has the advantage that it can be epitaxially grown on Si by chemical vapour deposition (CVD) [2] and presents properties suitable for achieving cost effective SiC power devices in the range 650V to 1200V. These 3C-SiC/Si substrates offer a promising alternative to the costly hexagonal SiC (4H-SiC) wafers and can also be used as template for the epitaxy of cubic GaN [3]. However, the presence of the Si substrate does limit the temperature available to anneal out the implantation damage generated by some device processing sequences.
This work investigates the properties of metal silicides as a potential Schottky contacts for high blocking voltage 3C-SiC/Si Schottky barrier diodes (SBDs). For this study, Ti and Pt silicide contacts are formed on the (100)3C-SiC surface. The influence of the silicide formation temperature (500oC-650oC) on the contact electrical properties is investigated in detail. Current voltage (I-V) and capacitance voltage characteristics (C-V) are used to evaluate the reverse leakage current and extract the Schottky barrier height as well as the concentration of electrically active dopants in the N type 3C-SiC/Si. The Pt silicide Schottky contact is found to present higher energy barrier height than the Ti silicide Schottky contact and this trend was confirmed by the associated improved reverse current in the Pt Schottky. This is a promising result as it suggests that the reverse leakage is not dominated by the stacking faults inherent to this material. Temperature dependent I-V characteristics are measured and compared to theoretical I-V curves to explore the mechanisms responsible of the reverse leakage. The effort towards high blocking voltage final SBD device requires excellent PN junction edge termination. In this work, to avoid the damage caused by Al ion implantation, the electrical properties of 3C-SiC/Si PN junction diodes fabricated by epitaxy of P type 3C-SiC layers on N type 3C-SiC/Si substrates are also investigated. The reverse current mechanisms in the PN junction and the Schottky are compared and the suitability of the PN for device termination is discussed.
[1] Kimoto, T., Cooper, J.A. Fundamentals of Silicon Carbide Technology: Growth, Characterization, Devices and Applications, Wiley, (2014)
[2] A. Severino, C. Locke, R. Anzalone, et al., ECS Transactions, 35 (6), 99 (2011)
[3] Okumura, H., Ohta, K., Feuillet, G., et al. Journal of Crystal Growth, 178 (1-2), 113, (1997)