(Invited) Current Status of High-k and Metal Gates in CMOS

Continued scaling of microelectronic devices has driven the change from SiO2 to alternative, Hf-based, high-k gate dielectric materials in recent years. This materials change has enabled device performance scaling without the gate leakage current becoming unacceptably high. The change from doped poly-Si to metal(s) as the gate electrode material also occurred simultaneously with the introduction of high-k materials, as the resulting high-k / metal gate (HKMG) device can effectively overcome depletion effects in poly-Si gate devices. Processing of the metal gate stack is a challenging task in terms of meeting requirements in effective work function for both nMOS and pMOS, as well as enabling low resistivity gate/contact metal fill. The introduction of 3D device structures such as FinFETs serves as an inflection point for novel materials and the transition from PVD to ALD processes.