CF4:O2 surface etching for the improvement of contact resistance and high-temperature reliability in Ni/Nb ohmic contacts on n-type 4H-SiC

Abstract

The influence of CF4:O2 surface etching on the formation of Ni/Nb ohmic contact to n-type 4H-SiC substrates was investigated. The specific contact resistivity extracted from the transmission line model showed that the contact with CF4:O2 etching had lower contact resistance than that of the sample without the etching process. The X-ray diffraction results showed that a higher concentration of Ni2Si formed at the interface of the contact after the fabrication process resulted in a lower specific contact resistivity. Moreover, the depth distribution of the elements revealed that under the CF4:O2 surface etching, a low density of the excess carbon atoms at the interface of the contact was observed. Transmission electron microscopy also confirmed that the low concentration of excess carbon atoms and the high density of Ni2Si at the interface play an important role in low specific contact resistivity as well as the high temperature reliability of the Ni/Nb/4H-SiC contacts undergoing CF4:O2 treatment.