Long Term Reliability and Deterioration Mechanisms of High-Temperature Metal Stacks on 4H-SiC

Kevin Brueckner; Oleg Rusch

doi:10.4028/p-K2pVqU

Paper Titles

Nickel Ohmic Contacts Formed on 4H-SiC by UV Laser Annealing
p.91

Electrical and Structural Properties of Ohmic Contacts of SiC Diodes Fabricated on Thin Wafers
p.97

Empirical Model of Low-Ohmic Nickel-Based Contact Formation on N-Type 4H-SiC Depending on Thermal Budget
p.105

Low-Ohmic Nickel Contacts on N-Type 4H-SiC by Surface Roughness Dependent Laser Annealing Energy Density Optimization
p.113

Long Term Reliability and Deterioration Mechanisms of High-Temperature Metal Stacks on 4H-SiC
p.119

Metal Contact Processing Experiments towards Realizing 500 °C Durable RF 4H-SiC BJTs
p.125

Performance Improvement by Carbon-Dioxide Supercritical Fluid Treatment for 4H-SiC Vertical Double Diffusion MOSFETs
p.131

Hydrogen Etching Process of 4H-SiC (0001) in Limited Regions
p.137

Comparative Study of the Self-Aligned Channel Processes for 4H-SiC VDMOSFET
p.145

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Long Term Reliability and Deterioration Mechanisms of High-Temperature Metal Stacks on 4H-SiC

Abstract:

In order to make SiC devices more accessible for high-temperature applications, reliable ohmic contacts and metallization systems which can also withstand extended operation at high temperatures are needed. In this work, metal layer stacks containing Ag, Ti, TiN, Ni and NiAl, where NiAl refers to a mixture of 97,4 wt% Ni and 2,6 wt% Al, were deposited on Si and SiC samples and consecutively thermally aged at 400 °C for 100 h in air. Mesa structures were found to be challenging for keeping oxygen from diffusing through the metal stack to the substrate. On flat surfaces, diffusion barriers were successfully used to protect the ohmic contact on 4H-SiC samples from oxidizing. Diffusion barriers made of TiN were found to show pore formation after the thermal treatment. The reason for the pores is thought to be gas formation, which is believed to be the result of the TiN layers containing too much nitrogen. The exact chemical composition of TiN layers therefore seems to be of vital importance for high-temperature applications.

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