AVS 50th International Symposium
    Electronic Materials and Devices Wednesday Sessions
       Session EM-WeA

Paper EM-WeA9
Correlation Between Electrical and Microstructural Properties of Low Resistance TiAl-based Ohmic Contacts to p-type 4H-SiC

Wednesday, November 5, 2003, 4:40 pm, Room 321/322

Session: Diamond/Contacts to SiC
Presenter: S. Tsukimoto, Kyoto University, Japan
Authors: S. Tsukimoto, Kyoto University, Japan
K. Nitta, Kyoto University, Japan
M. Moriyama, Kyoto University, Japan
M. Murakami, Kyoto University, Japan
Correspondent: Click to Email
In order to understand a contact formation mechanism for TiAl-based contacts, the electrical properties and microstructure of conventional Ti/Al and recently developed Ni/Ti/Al ohmic contacts to p-type 4H-SiC were correlated. The Ti/Al and Ni/Ti/Al ohmic contacts were prepared by depositing sequentially Ni, Ti, and Al on the SiC substrates doped with Al at 4.5x10@super 18@cm@super -3@, and subsequently annealing in an ultra high vacuum at 1000°C for 2min and 800°C for 10min, respectively. These contacts provided the lowest contact resistances of 1x10@super -5@ and 7x10@super -5@ @ohm@-cm@super 2@, respectively. X-ray diffraction and cross-sectional transmission electron microscopy were used to identify reacted layers formed at the ohmic contacts/SiC interfaces. For the Ti/Al contacts, ternary Ti@sub 3@SiC@sub 2@ compound layers with a hexagonal structure were formed to grow epitaxially on the substrates. For the Ni/Ti/Al contacts, hexagonal Al@sub 4@C@sub 3@ compound layers were also formed to grow epitaxially on the SiC in addition to other binary compounds. The formation of these epitaxial carbide layers was found to have a strong influence on the contact resistances to the SiC, and was essential to prepare low resistance TiAl-based contacts. The present experiment indicated that both the Ti@sub 3@SiC@sub 2@ and the Al@sub 4@C@sub 3@ layers played a role of intermediate semiconductor layers (ISL) between p-type SiC and the contact metals, which reduced the barrier height and/or depletion region.