Demonstration of Metal-Gated Low $V_{t}$ n-MOSFETs Using a Poly-$hbox{Si/TaN/Dy}_{2}hbox{O}_{3}/hbox{SiON}$ Gate Stack With a Scaled EOT Value

摘要

In this letter, we report that by using a thin Dysprosium oxide $( hbox{Dy}_{2}hbox{O}_{3})$ cap layer ($sim$1-nm thick) on top of SiON host dielectrics, the threshold voltage $(V_{t})$ of poly-Si/TaN gated n-FETs can be modulated to match that of the reference poly-Si/SiON devices, with a significantly scaled equivalent oxide thickness, a much reduced gate leakage, improved time-zero-break-down characteristics, and a minor degradation of the long channel devices mobility. These effects are attributed to the formation of a DySiON layer formation after full device fabrication due to the intermixing between the $hbox{Dy}_{2}hbox{O}_{3}$ cap and the SiON layer, as evidenced by a cross-sectional transmission-electron-microscopy measurement.