《Materials Science & Engineering B》
Development of Ni/Al and Ni/Ti/Al Ohmic Contact Materials for p-Type 4H-SiC
作者:
R Konishi，R Yasukochi，O Nakatsuka，Y Koide，M Moriyama
关键词:
Ohmic contact；p-type silicon carbide；NiAl；NiTiAl
摘要:
New Ni/Al and Ni/Ti/Al ohmic contact materials (a slash '/' indicates the deposition sequence) were developed by depositing on p-type 4H-SiC substrates with doping concentrations (N) of 3.0-9.0x10cmand subsequently annealing at 800C in an ultra high vacuum chamber. In contrast with conventional Ti/Al ohmic contacts, which must be annealed at temperatures above 1000C, both the Ni/Al contacts and Ni/Ti/Al contacts showed ohmic behavior after annealing at 800C. The lowest specific contact resistances of the Ni/Al contacts and the Ni/Ti/Al contacts (prepared by annealing at 800C) were 5x10and 6.6x10惟 cm, respectively. The later value is the lowest contact resistance ever obtained by annealing at such a low temperature. A theory indicates that a contact resistance less than 1.0x10惟 cmwould be obtained for the Ni/Ti/Al contacts when the hole concentration in the SiC is greater than 1.0x10cm. In addition, the Ni/Ti/Al contacts showed excellent thermal stability during isothermal annealing at 400C for 10 h in Ar atmosphere. The microstructural analysis at the metal/SiC interfaces showed that the Ni/Al contacts and the Ni/Ti/Al contacts reacted with the SiC substrates after annealing at 800C; the Ni/Al contacts formed NiSi and NiAlcompounds, and the Ni/Ti/Al contacts formed ternary TiSiCcompounds in addition to these binary compounds. A correlation between the electrical properties and the microstructure is discussed.
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