N-dipole material for stacked transistors

Abstract

Dipole engineering techniques for devices of stacked device structures are disclosed herein. An exemplary method for forming a gate stack of a transistor (e.g., a top transistor) of a transistor stack includes forming a high-k dielectric layer, forming an n-dipole dopant source layer over the high-k dielectric layer, performing a thermal drive-in process that drives an n-dipole dopant from the n-dipole dopant source layer into the high-k dielectric layer, and forming at least one electrically conductive gate layer over the high-k dielectric layer after removing the n-dipole dopant source layer. A drive-in temperature of the thermal drive-in process is less than 600° C. (e.g., about 300° C. to about 500° C.). The n-dipole dopant is strontium, erbium, magnesium, or a combination thereof. The method can further include tuning thermal drive-in process parameters to provide the gate dielectric with an n-dipole dopant profile having a peak located at a high-k/interfacial interface ±0.5 nm.