Material Selection and Interfacial Reaction in Ohmic-Contact Formation on SiC

Abstract

Ohmic contacts are a necessary part of microelectronic devices. In this chapter, we review the materials used for ohmic contacts and their interfacial reactions and structures on n- and p-type SiC, discuss material selection for ohmic-contact formation on SiC and the mechanism of formation of such contacts, and summarize recent advances. The metals for ohmic contacts on SiC are classified by group as the periodic table, and the relationship between the chemical reactivity of the metal with SiC and ohmic-contact formation is presented. Most metals in group VIII are excellent for ohmic contacts on n-type SiC, and only silicides and carbon are formed. A group IIIA metal, Al, is the most effective material for ohmic-contact formation on p-type SiC, and forms carbides and Si on SiC. The metals in groups IVB—VIIB generally show good thermal stability on SiC, and both silicides and carbides are formed. Various compounds, including silicides, carbides, nitrides, borides, and composites, for ohmic contacts on SiC are summarized. The recent advances in improved contacts, in our understanding of the mechanism, and in forming ohmic contacts with high thermal stability are also summarized. The role of nanosize graphitic structures in ohmic contacts and the mechanism based on catalytic graphitization are presented. Finally, challenging issues such as interfacial structural characterization on the nanometer and atomic scales and high-stability ohmic contacts in oxidizing environments are discussed.