Comparison of Ohmic Contact Characteristics of Different Metal on N Type 4H-SiC

Ohmic contact testing structures have been prepared on n type 4H-SiC layer with different multiple-layer metal, such as Ti/Ni/Au, Cr/Ni/Au and Ni/Ti/Au by magnetic sputter process. Special contact resistances about 10-6cm2 are achieved using TLM measurements. The composition of the alloy areas have been analyzed through XPS and AES, and the results show that the C vacancies induced by carbonides formation are important for ohmic contacts of Ti and Cr to SiC. However, the Ni/SiC structures need a relatively higher alloy temperature, so that the out diffusion of C atoms can offset the lack of Si in the top layer of SiC.