Enhancement of the Stability of Ti and Ni Ohmic Contacts to 4H-SiC with a Stable Protective Coating for Harsh Environment Applications |
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Authors: | Walter Daves Andreas Krauss Volker Häublein Anton J Bauer Lothar Frey |
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Affiliation: | (1) Naval Physical and Oceanographic Laboratory, Thrikkakara P.O, Cochin, 682 021, India |
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Abstract: | We report on wafer-level measurements of the long-term stability of Ti and Ni ohmic contacts to n-4H-SiC during thermal treatments in air or air/moisture environments up to 500°C. Contact metallizations with and without
a sputtered Ti (20 nm)/TaSi
x
(200 nm)/Pt (150 nm) diffusion barrier stack and Ti (20 nm)/TiN (10 nm)/Pt (150 nm)/Ti (20 nm) interconnects were compared.
A protective coating consisting of a SiO
x
(250 nm)/SiN
y
(250 nm) stack deposited by plasma-enhanced chemical vapor deposition (PECVD) was used. The stability of the contact metallizations
during long-term thermal treatments in air and air/moisture was studied. The best performance was achieved with Ti ohmic contacts
without the Ti/TaSi
x
/Pt stack. This system successfully withstood 1000 h thermal treatment at 500°C in air followed by 1000 h at 500°C in air/10%
moisture. After the aging, the contact failure ratio was below 1% and the specific contact resistivity amounted to (2.5 ± 1.1) × 10−4 Ω cm2. Scanning electron microscopy (SEM) cross-sectional analysis indicated no degradation in the contact metallization, demonstrating
the effectiveness of the SiO
x
/SiN
y
protective coating in preventing oxidation of the contacts. These results are very promising for applications in harsh environments,
where the stability of ohmic contacts is crucial. |
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Keywords: | |
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