5-5-3 SiC Contacts and Interconnect

5-5-3 SiC Contacts and Interconnect

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

References 105–110.

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.

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