Diffusion Welding Techniques for Power SiC Schottky Packaging

Abstract

This paper is devoted to the results of a diffusion welding technique applied to solve the problem of packaging for large area SiC Schottky diodes. To supply low defect density substrates for fabrication of 0.3 cm2 Schottky diodes TDI defect-reducing technology was used. Diodes were fabricated on CVD grown low-doped 4H-SiC single epitaxial layer without edge termination. Double layer Ni-Au and triple layer Ti-Ni-Au sputter metallization were used for Schottky contacts fabrication. Non-rectifying backside contacts were provided by Ni-Au metallization. Diodes were tested on-wafer and delivered for dicing, and packaging. To decrease the parasitic spreading resistance the thickness of initial sputter metallization was increased by diffusion welded 30 μm metal foil. Combined thick and plane metal layers make it possible to perform the clamp mode package used in power electronics. This scheme of packaging ensures current takeoff from the whole contact area and allows operating temperatures up to 600°C. The forward current-voltage characteristics measured at 75 A measured for packaged diodes yields 250 A/cm2 (70A) at 1.9 V forward voltage. Reverse recovery time for packaged diodes was in the range of 29-36 ns.