Transistor threshold voltage modulation by Dy2O3 rare-earth oxide capping: The role of bulk dielectrics charge

The mechanism governing threshold voltage (Vt) modulation in NiSi/SiON n-channel metal-oxide-semiconductor field-effect transistors when doping with rare-earth elements (dysprosium or Dy in this work) is studied. In addition to the widely reported interface dipole theory, this letter provides additional evidence that the bulk trapping charges (related to the unintermixed Dy2O3 layer after device fabrication) can play an important role in determining the device Vt for the above-mentioned gate stacks. It is thus suggested that a careful design of the capping layer thickness and the thermal budget for intermixing the capping layer with host dielectrics is necessary to eliminate the impact from bulk trapping charges to the device performance.