Reliability of aluminum-bearing ohmic contacts to SiC under high current density

The degradation produced by high current density stressing of a contact to p-SiC consisting of an Al-bearing ohmic contact, a TiW diffusion barrier, and a thick Au overlayer was studied. The test structure allowed for vertical current stressing and the measurement of the specific contact resistance before and after stressing. A threshold current for contact failure was established for the Ti/Al and W/Al contacts, at which a large increase in specific contact resistance was measured and extensive voiding occurred in the ohmic contact region. The high current stressing generated a flux of Al from the ohmic contact layer, through the TiW barrier, to the surface to be oxidized, along with a flux of Au into the ohmic contact layer. The voiding in the ohmic contact layer, caused by the unequal fluxes of Al and Au, decreased the active area of the contact, consequently increasing the current density and the associated effects from electromigration and Joule heating, initiating a runaway event.

[1]  W. Kern.  Cleaning solutions based on hydrogen peroxide for use in silicon semiconductor technology , 1970 .

[2]  Melanie W. Cole,et al.  Thermal stability and performance reliability of Pt/Ti/WSi/Ni ohmic contacts to n-SiC for high temperature and pulsed power device applications , 2002 .

[3]  S. Mohney,et al.  Ta–Ru–N diffusion barriers for high-temperature contacts to p-type SiC , 2005 .

[4]  Soo Jin Chua,et al.  Contact resistivity measurement using four circular contacts , 1992 .

[5]  POLARITY EFFECT ON FAILURE OF NI AND NI2SI CONTACTS ON SI , 1997 .

[6]  Brian P. Downey,et al.  Current-Induced Degradation of Nickel Ohmic Contacts to SiC , 2009 .

[7]  R. Singh,et al.  Commercial impact of silicon carbide , 2008, IEEE Industrial Electronics Magazine.

[8]  S. Tsukimoto,et al.  Role of Interface Layers and Localized States in TiAl-Based Ohmic Contacts to p-Type 4H-SiC , 2007 .

[9]  B. Hull,et al.  Morphological study of the Al–Ti ohmic contact to p-type SiC , 2002 .

[10]  M. Wittmer.  Barrier layers: Principles and applications in microelectronics , 1984 .

[11]  T. B. Massalski,et al.  The Au−W (Gold-Tungsten) system , 1985 .

[12]  James R. Lloyd,et al.  Electromigration in Thin Film Conductors , 1997 .

[13]  Mounira Berkani,et al.  Estimation of SiC JFET temperature during short-circuit operations , 2009, Microelectron. Reliab..

[14]  T. Sakai,et al.  Correlation between the electrical properties and the interfacial microstructures of TiAl-based ohmic contacts to p-type 4H-SiC , 2004 .

[15]  Robert S. Okojie,et al.  Reliability assessment of Ti/TaSi2/Pt ohmic contacts on SiC after 1000 h at 600 °C , 2002 .

[16]  J. Scofield,et al.  Thermally stable ohmic contacts to 6H- and 4H- p-type SiC , 1998, 1998 Fourth International High Temperature Electronics Conference. HITEC (Cat. No.98EX145).

[17]  A. K. Sinha,et al.  Shallow junction cobalt silicide contacts with enhanced electromigration resistance , 1984 .

[18]  R. Sisson,et al.  The effects of processing parameters on the microstructure and properties of sputter-deposited TiW thin film diffusion barriers , 1987 .

[19]  S. Arthur,et al.  Stacking-fault formation and propagation in 4H-SiC PiN diodes , 2002 .

[20]  Robert F. Davis,et al.  A critical review of ohmic and rectifying contacts for silicon carbide , 1995 .

[21]  G. Radnóczi,et al.  Nickel based ohmic contacts on SiC , 1997 .

[22]  M. H. Woods,et al.  Elimination of Silicon Electromigration in Contacts by the use of an Interposed Barrier Metal , 1982, 20th International Reliability Physics Symposium.

[23]  I. Kiryushin,et al.  Electromigration threshold of thin-film conductors , 1990 .

[24]  R. S. Nowicki,et al.  General aspects of barrier layers for very-large-scale integration applications II: Practice , 1982 .

[25]  S. Mohney,et al.  Tantalum-Ruthenium Diffusion Barriers for Contacts to SiC , 2006 .