Low resistance cathode metallization and die-bonding in silicon carbide p-n junction diodes

We investigated how surface roughness, intentionally induced by chemical-mechanical polishing, affects the formation of ohmic contacts to an n-type 4H-SiC using a common circular transmission length method (CTLM). Nickel metal was used as the cathode ohmic contacts to n-type SiC. The specific contact resistance (SCR) for the un-polished sample (F I) and polished samples (F2 and F3) was 5.4 x 10(-3) Omega cm(2) and 4.2 x 10(-3) Qcm(2), respectively, We found out that the un-polished sample (F1) had much higher SCR than the samples, F2 and F3. In addition, we did not see any difference between the differently polished samples, F2 and F3, indicating that there was no dependence on the face type of SiC (Si- or C-face) in the values of SCR. We also investigated the die-bonding processes with the surface roughness and metallization schemes' effects.