Post-annealing temperature dependences of electrical properties and surface morphologies for arsenic ion-implanted 4H-SiC at high temperature

High-temperature ion implantation of arsenic (As⁺) into the 4H-silicon carbide (SiC) substrates with high dose of 7×10¹⁵ cm^-2 has been investigated as an effective doping method of n-type dopant for SiC power electron devices fabrication. Regardless of the ion implantation temperature, the sheet resistances (R_s) decrease below 1600 °C post-annealing and increase above 1700 °C as the post-annealing temperature increases. The specified low R_s value is achieved in the sample implanted at 500 °C and annealed at 1600 °C, an order of magnitude smaller than that implanted at room temperature (RT). Atomic force microscopy (AFM) images reveal that the surface roughness of ion-implanted SiC increases with the increase of post-annealing temperature. Secondary ion mass spectroscopy (SIMS) results show that As⁺ dopant depth profiles of the sample implanted at 500 °C do not change before and after the post-annealing. On the other hand, for the sample implanted at RT, the As⁺ concentration in the ion-implanted layer decreases due to the outer-diffusion. These results indicate that high-temperature ion implantation is an effective method to prevent the outer-diffusion of As⁺ dopants during high-temperature post-annealing. It is considered that these post-annealing temperature dependences are caused by the evaporation of SiC surface layer.