Investigation of interface trap states in TiN/Al2O3/p-Si capacitor by deep level transient spectroscopy

Abstract

The minority carrier (electron) capture process and the interface trap density of a TiN/Al2O3/p-Si metal–oxide–semiconductor capacitor were examined by deep level transient spectroscopy (DLTS). It was found that the activation energies of the large peaks detected at higher temperatures with gate bias voltages of 1.8, 1.5, 1.3, and 1.1 V were 0.19, 0.24, 0.29, and 0.37 eV, respectively. These energies were related to the electron-capture process from the conduction band by interface states in the upper half of the Si band gap. The interface state passivation effect of postannealing in a hydrogen ambient was studied from the minority carrier capture process and the usual DLTS signals. The Dit at an energy of 0.35 eV from the valence bandedge decreased from 1×1012 cm−2 eV−1 at the as-fabricated state to 4×1011 cm−2 eV−1 after H2 annealing at 450 °C. It was also found that the Dit at an energy of 0.3 eV from the conduction bandedge decreased to the same amount by the same annealing process.