Structural and Reliability Analysis of Ohmic Contacts to SiC with a Stable Protective Coating for Harsh Environment Applications

Abstract

Ohmic contacts to SiC are the most crucial device components for the reliability of SiC devices in harsh environments. This work aimed at improving the reliability of Ni and Ti ohmic contacts to SiC using stable protective coatings. The stability of the contacts was investigated by means of long-term aging at 600 • C in air and air/moisture ambient as well as temperature cycling up to 700 • C in air/moisture ambient. The structural and chemical properties were investigated by means of XPS depth profiling and TEM analysis. The beneficial effect of a stable protective coating inhibiting the migration of oxygen/moisture into the contact metallization is demonstrated. Excellent reliability benchmarks are shown for Ti ohmic contacts with a PECVD a-SiO x /a-SiC protective coating. The results are very promising for harsh environment applications.

Novel copper metallization on silicon carbide electronic devices enabling increased packaging lifetime and higher junction-temperatures

“…By analyzing a sample in a FIB cross-section (see figure 6) and doing an EDX analysis, this effect could be attributed to silicon diffusion from the contact into the copper. Daves et al [6] observed also chemical reactivity of the Ni-contact during temperature storage at 600°C. In this case a reaction of Ni and Si from the contact with oxygen lead to increased resistivity and changed ohmic behavior.…”

High-temperature reliability of integrated circuit based on 4H-SiC MOSFET with Ni/Nb ohmic contacts for harsh environment applications

“…13) However, it has been reported that the high temperature reliability of the devices based on SiC MOSFET is not only governed by the high interface trap density at the SiO 2 /SiC interface but also strongly affected by the reliability of the metal/SiC contacts. [14][15][16][17][18][19][20] Therefore, to introduce the electronic circuits based on SiC MOSFET to reality, the fabrication of ohmic contact with low specific contact resistance and high temperature reliability are strongly required.…”