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

Abstract

The fixed charges (Nf) and the "slow" (Nsi) and "fast" (Dit) 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 Nf, Nsi and Dit with various post-annealing conditions were evaluated. Annealing under a H2 atmosphere effectively reduced the Nf, Nsi, and Dit. The Dit 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.