Physical Origins of Threshold Voltage Variation Enhancement in Si(110) n/pMOSFETs

Threshold voltage V
_th
variations in scaled (110) n/pMOSFETs are systematically investigated. V
_th
variations in (110) nMOSFETs and pMOSFETs with high channel dose are larger than those in (100) nMOSFETs and pMOSFETs, respectively. Physical origins of V
_th
variation enhancement in (110) MOSFETs are analyzed on the basis of the substrate impurity concentration dependence of the body effect and S factor variations. It is found that the depletion width variations due to boron ion channeling and the interface trap density variations enhance V
_th
variations in boron-doped (110) nMOSFETs and that the interface fixed charge variations enhance V
_th
variations in arsenic-doped (110) pMOSFETs. An undoped channel combined with a steep boron profile and moderate phosphorus doping into the surface are desirable to minimize V
_th
variations in (110) nMOSFETs and pMOSFETs, respectively.