Analysis of Ohmic Contacts Simultaneously Formed on both n-Type and p-Type 4H-SiC

In this paper, various annealing conditions using Al-based (Ti/Al/Ti/Au=70nm/100nm /5nm/120nm) and Ni-based (Ti/Ni/Ti/Au=20nm/90nm/5nm/120nm) metal contacts to n-type and p-type ion-implanted 4H-SiC epi layers have been studied in the effort to optimize simultaneous ohmic contact formation with the lowest specific contact resistance (SCR) values. Values of 1.091×10 -4 Ω∙cm 2 and 1.158×10 -5 Ω∙cm 2 were achieved using Al-based Ohmic metal contacts for p-type and n-type 4H-SiC, respectively, at an annealing temperature of 950°C and under vacuum for 90 sec. Ohmic formation mechanisms were analyzed using the X-Ray Diffraction (XRD) surface analysis method, indicating Ti 3 SiC 2 alloys to be the key intermediate layer formed at SiC/Ti interface, responsible for Ohmic properties to p-type SiC. The paper summarizes the metal process combinations possible for the formation of Ohmic contacts to both n-type and p-type 4H-SiC, offering various options in either using the same metal materials and/or common annealing conditions.