Energy distribution of interface state density in Si band gap of Hafnium Silicate based MOS capacitors

Abstract

The energy distribution of interface states density, Dit, in the Si bandgap of Hafnium silicate based Metal-Oxide-Semiconductor Capacitors (MOS-C) has been studied using the alternating current (ac) conductance method. The interface trap density was higher in the upper half of the bandgap than in the lower half. Using samples of two different equivalent oxide thickness values (EOT) in the ultrathin regime, the electron traps were found to be denser in heavily scaled HfSiON based electronic devices, due to possible surface damage or to strain arising from down scaling of devices further in the ultrathin regime. The electron and hole capture cross sections were higher than values reported for SiO2 based devices, suggesting that carrier trapping was more efficient in materi-als of high dielectric constants (i.e. high-κ dielectrics) compared to SiO2, and explained why carrier mobility degradation was more severe in HfSiON