5-5-3 SiC Contacts and Interconnect
All useful semiconductor electronics require conductive signal paths in and out of each device as well as
conductive interconnects to carry signals between devices on the same chip and to external circuit
elements that reside off-chip. While SiC itself is theoretically capable of fantastic electrical operation
under extreme conditions (Section 5.3), such functionality is useless without contacts and interconnects
that are also capable of operation under the same conditions. The durability and reliability of
metal–semiconductor contacts and interconnects are one of the main factors limiting the operational
high-temperature limits of SiC electronics. Similarly, SiC high-power device contacts and metallizations
will have to withstand both high temperature and high current density stress never before encountered
in silicon power electronics experience.
The subject of metal–semiconductor contact formation is a very important technical field too broad
to be discussed in great detail here. For general background discussions on metal–semiconductor contact
physics and formation, the reader should consult narratives presented in References 15 and 104. These
references primarily discuss ohmic contacts to conventional narrow-bandgap semiconductors such as
silicon and GaAs. Specific overviews of SiC metal–semiconductor contact technology can be found in
As discussed in References 105–110, there are both similarities and a few differences between SiC
contacts and contacts to conventional narrow-bandgap semiconductors (e.g., silicon, GaAs). The
same basic physics and current transport mechanisms that are present in narrow-bandgap contacts
such as surface states, Fermi-pinning, thermionic emission, and tunneling, also apply to SiC contacts.
A natural consequence of the wider bandgap of SiC is the higher effective Schottky barrier heights.
Analogous with narrow-bandgap ohmic contact physics, the microstructural and chemical state of
the SiC–metal interface is crucial to contact electrical properties. Therefore, premetal-deposition
surface preparation, metal deposition process, choice of metal, and post-deposition annealing can
all greatly impact the resulting performance of metal–SiC contacts. Because the chemical nature of
the starting SiC surface is strongly dependent on surface polarity, it is not uncommon to obtain
significantly different results when the same contact process is applied to the silicon face surface
versus the carbon face surface.