The Improvement of Ohmic Contacts Property in P-Type 4H-SiC LDMOSFET Using Ti(20 nm)/Al(30 nm) Electrodes

Silicon Carbide laterally diffused Metal-Oxide-Semiconductor Field Effect Transistor (SiC LDMOSFET) is widely used in high voltage integrated circuits. Until now, one of the obstacles which restrict its further development is its ohmic contact with p-type SiC. Previously, Aluminum is used to form the ohmic contact for p-type SiC. To form the ohmic contact with p-type SiC, Al metal was deposited and then annealed at high temperature subsequently. However, at high temperature, its thermal stability is supposed to be degraded, and will make the device performance getting worse. The research showed that the addition of titanium can decrease the contact resistance and improve the thermal stability. In this paper, a Ti(20 nm)/Al(30 nm) contact was formed by sputtering on p-type 4H-SiC Epitaxial film respectively with doping concentration of 1 × 10 20 cm −3 . Then, rapid thermal annealing was performed in argon atmosphere at 1000˚C for 2 min to form the ohmic contact. Transmission-line-model (TLM) method was examined to extract the contact resistivity. In case of Ti(20 nm)/Al(30 nm)/p-type SiC, a specific contact resistance of 5.71 × 10−4 Ω·cm2 was obtained, nearly one order of magnitude lower than the respected value. This research has a positive effect on the device performance of SiC LDMOSFETs.