Variability Improvement by Si Surface Flattening of Electrical Characteristics in MOSFETs With High-k HfON Gate Insulator

Variability improvement of metal-oxide-semiconductor field-effect transistors (MOSFETs) characteristics with high-k HfON gate insulator by Si surface flattening was investigated. The Si surface flattening process was carried out by Ar/4.9%H₂ anneal utilizing rapid thermal annealing system. The HfON gate insulator was formed by the in-situ Ar/O₂ plasma oxidation of HfN utilizing electron cyclotron resonance plasma sputtering followed by the post deposition anneal at 600 °C for 1 min. The Si surface flattening was found to significantly improve the threshold voltage variability (ΔV_TH) of MOSFET with HfON gate insulator for the first time. Furthermore, the stability of the device characteristics was improved up to the measurement temperature of 100 °C by introducing the Si surface flattening process.