Incorporating nitrogen in dipole engineering for multi-threshold voltage applications in stacked device structures

Abstract

Dipole engineering techniques are disclosed that incorporate dipole dopant and/or nitrogen into gate dielectrics (e.g., high-k dielectric layers thereof) to realize multi-threshold voltage transistor tuning of transistors. The dipole engineering techniques include (1) forming a dipole dopant source layer over gate dielectrics of some transistors, but not other transistors, (2) forming a mask over gate dielectrics of some transistors, but not other transistors, (3) performing a nitrogen-containing thermal drive-in process, and (4) removing the dipole dopant source layer and the mask after the nitrogen-containing thermal drive-in process. The nitrogen-containing thermal drive-in process diffuses nitrogen and dipole dopant (n-dipole dopant and/or p-dipole dopant) into unmasked gate dielectrics having the dipole dopant source layer formed thereon, nitrogen into unmasked gate dielectrics, and dipole dopant into masked gate dielectrics having the dipole dopant source layer formed thereon. Masked gate dielectrics without the dipole dopant source layer formed thereon remain undoped.