Papers by Keyword: Diffusion Welded Contacts

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Authors: Oleg Korolkov, Toomas Rang, A. Syrkin, V. Dmitriev
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.
Authors: Oleg Korolkov, Natalja Sleptsuk, Toomas Rang, A. Syrkin, Vladimir Dmitriev
Abstract: For more authentic comparison of Schottky parameters between combined sputter (Ti/Ni/Au) and diffusion welded (DW) Al contact and direct DW Al contact to SiC the forward current-voltage characteristics were measured at the temperature range 293-473 K on full-packed 0.3 cm2 Schottky diodes. Surprising fact was discovered that the temperature behaviour of parameters remains of the same character for both kind of contacts but for the combined sputter- DW samples the values of parameters is much closer in magnitude to sputter contacts. Apparently, chemical treatment before the DW process preserves untouched the contact surface layer formed by annealing of initial sputter metallization of the chips (e.g. Ni2Si, Ti3SiC2), and this layer serves as barrier during diffusion welding. In the second part of the work we give the results on long-term reliability testing where through the SiC Schottky diode with the DW Al contacts during 300 hr has been passed constant forward stabilized current of 100 A/cm2 density. The primary and final values of Uf for DW Schottky contact have not changed during the test.
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