Symmetrical threshold voltage in complementary metal-oxide-semiconductor field-effect transistors with HfAlOx(N) achieved by adjusting Hf∕Al compositional ratio

Abstract

We propose a method for restoring the symmetry in the threshold voltage (Vth) in complementary metal-oxide-semiconductor field-effect transistors (FETs) with a Hf-based high-k dielectric. This technique is based on the Al composition adjustment in the HfAlOx(N) dielectric film to achieve the symmetric Vth. The asymmetry of ∣Vth∣ in n and p metal-oxide-semiconductor FET (MOSFETs) due to the Fermi-level pinning at the interface between the poly-Si gate electrode and Hf-based high-k dielectric is considered to be induced independently by two kinds of interfacial dipoles. The adjustment of the Al content in HfAlOx(N) enables us to balance these dipoles. Vth values of n- and p-MOSFETs are shifted in the positive direction as the Al content in HfAlOx(N) increases. Symmetrical Vth values can be obtained for poly-Si and single fully silicided nickel gate electrodes when the Al contents are about 25 and 7at.% in HfAlOx(N), respectively.