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

Paper EM-WeA8
Improved Titanium / Nickel Ohmic Contacts on N-Type 4H Silicon Carbide

Wednesday, November 5, 2003, 4:20 pm, Room 321/322

Session: Diamond/Contacts to SiC
Presenter: J.H. Park, University of Florida
Authors: J.H. Park, University of Florida
P.H. Holloway, University of Florida
Correspondent: Click to Email
Nickel (Ni) contacts are the most commonly used ohmic contacts to n-type silicon carbide (SiC). Unfortunately, the Ni contacts exhibit rough interface morphology after high temperature annealing. In addition, the reaction to form the silicide liberates carbon, which can segregate to the metal-semiconductor interface. These two factors limit the reliability of the Ni contacts to n-SiC for high temperature and power applications. The electrical and structural properties of electron-beam evaporated nickel/titanium metal contacts to n-type 4H SiC were studied by current-voltage (I-V), Auger electron spectroscopy (AES), secondary ion mass spectrometry (SIMS) and X-ray diffraction (XRD) techniques. Nickel/titanium metal contacts on the 4H SiC were rectifying as deposited but turned to ohmic after rapid thermal annealing (RTA) at 1000°C for 2 minutes in nitrogen. The nickel/titanium contacts were converted to the layer sequence of titanium carbide/nickel silicide/SiC by annealing. This structure had a low specific contact resistance of 10@super -5@ @ohm@-cm@super 2@. A shallower and smoother nickel silicide/SiC interface was obtained as compared to the conventional only-nickel contacts. The nickel silicide layer was formed on SiC by a nickel-SiC reaction during high temperature annealing which left excess carbon at the interface between the silicide and SiC. Titanium reacted with the carbon to form a titanium carbide layer on the nickel silicide, which led to reduced carbon excesses at the interface and lower resistance of the ohmic contacts. The phase inverting mechanisms and the effects of nickel/titanium thickness on this process have been studied. Phase analysis of the nickel silicides and titanium carbides using XRD and TEM will be reported.