Effects of post metallization annealing on the electrical reliability of ultra-thin HfO/sub 2/ films with MoN and WN gate electrodes

Abstract

Aggressive scaling of CMOS devices for submicron technology has enabled the exponential growth of MOSFETs in complexity and functionality over the past decades. HfO/sub 2/ films have been shown to be promising high-k candidates. Among refractory metal nitrides, WN and MoN are the promising candidates for gate electrode materials because of their excellent diffusion barrier properties and high melting points. The origin of traps in high-k dielectrics, however, still remains a question. When an electron current is passed through the HfO/sub 2/ of a MOS capacitor, defects such as electron traps, interface states, etc., gradually build up in the oxide. The stress induced leakage current (SILC) is correlated with the tunneling current through the oxide layer during electrical stress. A conductive path is created in the gate oxide layer after reaching a critical trap density, called soft breakdown (SBD). Then, the Joule heating in the local conductive path leads to lateral propagation of the leakage spots and the oxide is finally broken down, i.e. hard breakdown (HBD). The present work is focused on the electrical reliability aspects of different gate electrodes (MoN and WN) with ultra thin HfO/sub 2/ (5 nm) for MOS capacitor fabrication.