TY - JOUR
T1 - Investigation of polarity effects on the degradation of Pd/Ti/Pt ohmic contacts to p-type SiC under current stress
AU - Downey, B. P.
AU - Flemish, J. R.
AU - Mohney, S. E.
N1 - Funding Information:
This work was supported in part by the Exploratory and Foundational Graduate Student Research Program provided by the Applied Research Laboratory at Penn State University and through the use of facilities at The Pennsylvania State University Materials Research Institute Nano Fabrication Network under the National Science Foundation Cooperative Agreement No. 0335765, National Nanotechnology Infrastructure Network, with Cornell University.
PY - 2011/11
Y1 - 2011/11
N2 - Degradation of low resistance Pd/Ti/Pt ohmic contacts to p-SiC under high current density stressing and the effects of polarity are presented. The Pd/Ti/Pt contact is compared to the conventional Ti/Al contact and provides a lower contact resistance, smoother surface morphology, lower required annealing temperature, and better stability under current stressing. A thick Au overlayer is added to both metallizations for continuous direct current (dc) and pulsed dc stressing. A 31% increase in total resistance is measured for the Ti/Al contacts after 20 h of continuous dc stressing at 200 mA for 5 μm radius contacts, compared to an increase of only 2.5% for the Pd/Ti/Pt contacts. Degradation of the entire anode and cathode was observed for the Ti/Al contacts, whereas damage to only the leading edge of the cathode of the Pd/Ti/Pt contacts was found. The degradation behavior of the Pd/Ti/Pt contacts is explained by a polarity effect, where the cathode reached a higher temperature than the anode under continuous dc stressing. When the contacts were instead pulsed with a dc current of 200 mA using 5 μs pulses and a 10% duty cycle, both contact schemes were electrically stable, probably due to the reduced temperature during testing. However, chemical instability of the Ti/Al contacts was still evident, and although the Pd/Ti/Pt ohmic contacts appeared unaltered, voiding between the Au bond pad and the Pd/Ti/Pt metallization occurred.
AB - Degradation of low resistance Pd/Ti/Pt ohmic contacts to p-SiC under high current density stressing and the effects of polarity are presented. The Pd/Ti/Pt contact is compared to the conventional Ti/Al contact and provides a lower contact resistance, smoother surface morphology, lower required annealing temperature, and better stability under current stressing. A thick Au overlayer is added to both metallizations for continuous direct current (dc) and pulsed dc stressing. A 31% increase in total resistance is measured for the Ti/Al contacts after 20 h of continuous dc stressing at 200 mA for 5 μm radius contacts, compared to an increase of only 2.5% for the Pd/Ti/Pt contacts. Degradation of the entire anode and cathode was observed for the Ti/Al contacts, whereas damage to only the leading edge of the cathode of the Pd/Ti/Pt contacts was found. The degradation behavior of the Pd/Ti/Pt contacts is explained by a polarity effect, where the cathode reached a higher temperature than the anode under continuous dc stressing. When the contacts were instead pulsed with a dc current of 200 mA using 5 μs pulses and a 10% duty cycle, both contact schemes were electrically stable, probably due to the reduced temperature during testing. However, chemical instability of the Ti/Al contacts was still evident, and although the Pd/Ti/Pt ohmic contacts appeared unaltered, voiding between the Au bond pad and the Pd/Ti/Pt metallization occurred.
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U2 - 10.1116/1.3659730
DO - 10.1116/1.3659730
M3 - Article
AN - SCOPUS:84255190040
VL - 29
JO - Journal of Vacuum Science and Technology B:Nanotechnology and Microelectronics
JF - Journal of Vacuum Science and Technology B:Nanotechnology and Microelectronics
SN - 2166-2746
IS - 6
M1 - 061205
ER -