Design And Research Of Copper-based P-type SiC Ohmic Contact

As a prominent representative of third-generation semiconductors,SiC is widely used in high-frequency and high-voltage devices because of its many excellent characteristics.In the manufacturing process of SiC devices,obtaining an ohmic contact with good stability and low contact resistivity is the focus of attention.As a current research hotspot,p-type SiC ohmic contact still has many problems:the formation mechanism of ohmic contact is not yet clear;the annealing temperature required for the formation of ohmic contact is too high;the thermal stability and reliability of ohmic contact are poor,and the specific contact resistance is larger.This paper mainly studies several p-type SiC ohmic contacts:Cu/Ti/Al,Cu/Ti/Al/Ni,Ti/Al/Ni and Cu/Ti/Al/W.Cu/Ti/Al contact mainly studies the effects of different annealing temperatures and different ratios of Ti/Al thickness on electrical properties.Cu/Ti/Al/Ni contact studies the effect of annealing temperature on electrical properties.In addition,the electrical characteristics between Cu/Ti/Al/Ni contacts and Cu/Ti/Al,Ti/Al/Ni and Cu/Ti/Al/W contacts are compared and analyzed.The linear transmission line model(TLM)is used to measure the specific contact resistance of the sample.Analyze the mechanism of ohmic contact formation through structural characterization.Scanning electron microscope(SEM),X-ray diffraction(XRD),transmission electron microscope(TEM)and energy dispersive X-ray(EDX)are used to analyze the formation of phases and the distribution of elements and the morphology of contact interfaces.This paper studies the electrical characteristics of Cu/Ti/Al ohmic contacts with different Ti/Al ratios.When Ti:Al=1:6,Cu/Ti/Al contacts can form ohmic contacts at 800?annealing,and the minimum specific contact resistance is 2.0×10^-5?·cm².When Ti:Al=1:4,the specific contact resistance value of Cu/Ti/Al contact does not change much with the annealing temperature.Although the thickness ratios of the Ti and Al layers are different,the electrical properties of the ohmic contact after annealing at 800-1000°C are very good,and the contact resistivity can be close to the order of 10^-5?·cm².This paper also studies the electrical properties of Cu/Ti/Al/Ni ohmic contacts.After annealing at 900°C,the Cu/Ti/Al/Ni contact formed an ohmic contact with a specific contact resistance of8.9×10^-4?·cm².The addition of Cu can reduce the SiC doping concentration and annealing temperature of the ohmic contact formed by the Cu/Ti/Al/Ni contact,and the process cost and preparation difficulty can be reduced.Compared with Cu/Ti/Al contact,metallic Ni as a protective layer can effectively improve the thermal stability of the ohmic contact and limit the oxidation of the contact surface.In addition,comparing the electrical characteristics of Cu/Ti/Al/Ni and Cu/Ti/Al/W contacts,Ni has a better effect as a protective layer.