Abstract
We report on the results of our investigation of the effect of deposition temperature on molybdenum (Mo) used as Schottky contacts to fabricate silicon carbide (SiC) Schottky barrier diodes. The contacts were deposited using magnetron sputtering on n-type 4H-SiC at temperatures ranging from 25 to 900 °C. The fabricated diodes were characterized by current–voltage, current–voltage–temperature, and capacitance–voltage measurements. The diodes showed average Schottky barrier heights that decreased from 1.54 to 1.00 eV with increasing deposition temperature of the contacts. The average values of the ideality factors similarly decreased from 1.21 to 1.06 with increasing deposition temperature. However, the diodes with contacts deposited at 400–900 °C nearly maintained a constant ideality factor value of 1.06. The x-ray diffraction analysis indicated that silicides were formed at the interface for contacts deposited at or above 400 °C. The improved properties of the diodes with contacts deposited at higher temperatures are correlated with the formation of the interfacial alloys possessing improved electrical properties. This work demonstrates that high temperature deposition is another method for optimizing the properties of Mo contacts for the fabrication of 4H-SiC Schottky diodes for electronic applications in high power and high temperature environments.
Highlights
INTRODUCTIONElectronics that function reliably under adverse conditions of high temperature and high power are becoming a common necessity in power control systems, avionics, sensors, and other applications. While silicon (Si) and other traditional semiconductors have been used in many power electronic devices, it is becoming increasingly challenging to make further improvements due to limitations in the intrinsic properties of these materials. Wide bandgap semiconductors such as silicon carbide (SiC) are the materials of choice for fabricating high temperature and high power devices such as Schottky barrier diodes on account of their better material properties. Schottky barrier diodes, unlike p-n junction diodes, have zero reverse recovery time and low conduction loss, making them attractive for high frequency applications as well
The inset in this figure shows a representative plot of dV/d ln(IF) vs IF of a diode with the Mo contact deposited at 800 ○C, from which a series resistance of 7.84 Ω is obtained, with a calculated on-resistance Ron (= product of Rser and the diode area) of 1.21 mΩ cm2
Ti/silicon carbide (SiC) SBDs indicated an opposite trend, where the series resistance was found to increase as the contact deposition temperature was increased
Summary
Electronics that function reliably under adverse conditions of high temperature and high power are becoming a common necessity in power control systems, avionics, sensors, and other applications. While silicon (Si) and other traditional semiconductors have been used in many power electronic devices, it is becoming increasingly challenging to make further improvements due to limitations in the intrinsic properties of these materials. Wide bandgap semiconductors such as silicon carbide (SiC) are the materials of choice for fabricating high temperature and high power devices such as Schottky barrier diodes on account of their better material properties. Schottky barrier diodes, unlike p-n junction diodes, have zero reverse recovery time and low conduction loss, making them attractive for high frequency applications as well. Mo is the metal of choice in some of the SiC processing such as high temperature ion implantation where it is utilized as the implant masking layer.18 In their sixth generation SiC SBDs, Infineon employed Mo-based contacts with lower turn-on voltage this was accompanied by increased reverse leakage currents.. Renz et al, reported Mo/SiC SBDs with a barrier height of 1.27 eV and a significantly reduced leakage current on using a P2O5 surface passivation treatment.. The values of the reported barrier heights of these Mo/SiC SBDs range from 1.08 to 1.43 eV Most of these diodes underwent surface passivation and post-deposition annealing at ∼300–500 ○C in an inert atmosphere. This work indicates that deposition of Mo contacts at these temperatures significantly enhances the properties of 4H-SiC Schottky diodes for high temperature applications
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