4H-SiC MISFETs with nitrogen-containing insulators

摘要

4H-SiC MISFETs with nitrogen-containing insulators have been fabricated and characterized. Several techniques have been explored to incorporate nitrogen in the gate insulator in order to improve the density of interface states and thereby the channel mobility. The techniques are N_2O-grown oxides, the oxidation of a surface layer co-implanted with N~+ and Al~+, deposited SiO_2 annealed in N_2O and NO, and deposited SiN_x/SiO_2 annealed in N_2O. By optimizing the formation process of the gate insulators, MIS capacitors with N-containing insulators have demonstrated an interface state density close to the conduction band edge below , 2 ×10~(11) cm~(-2) eV~(-1), which is one or two orders-of-magni-tude lower than that of MOS capacitors with oxides grown in dry O_2. The channel mobility of the n-channel 4H-SiC(0001) MISFETs with N-containing insulators is increased to about 30 cm~2/Vs. In addition, an even higher channel mobility of 50 cm~2/Vs has been realized by utilizing N-containing insulators adequately processed on the 4H-SiC(000l) face. From the experimental results, the dominant scattering mechanisms in SiC MISFETs have been identified; Coulomb scattering and electron trapping at interface states dominate the channel mobility in SiC MOSFETs with thermally-grown and deposited SiO_2. The application of N-containing insulators to p-channel 4H-SiC MIS devices is also discussed.