Post-Annealing Effects on Fixed Charge and Slow/Fast Interface States of TiN/Al₂O₃/p-Si Metal–Oxide–Semiconductor Capacitor

The fixed charges (N_f) and the "slow" (N_si) and "fast" (D_it) interface states of TiN/Al₂O₃/p-Si metal–oxide–semiconductor (MOS) capacitors were investigated by the capacitance–voltage and deep level transient spectroscopy (DLTS) method. In addition, small pulse DLTS (SP-DLTS) analysis was performed for a more precise estimation of energies and capture cross sections of the interface states. The variations in the N_f, N_si and D_it with various post-annealing conditions were evaluated. Annealing under a H₂ atmosphere effectively reduced the N_f, N_si, and D_it. The D_it at an energy of 0.35 eV from the valence band decreased from 1×10¹² cm^-2eV^-1 at the as-fabricated state to 4×10¹¹ cm^-2eV^-1 after annealing at 450°C. A large peak related to minority carrier capture was detected in the high temperature region of the DLTS results. The peak intensity also decreased after hydrogen annealing. This suggests that the interface states in the upper half of the Si band-gap decrease with H₂ annealing.