Very Low-Work-Function ALD-Erbium Carbide (ErC2) Metal Electrode on High- $K$ Dielectrics

Erbium carbide (ErC
₂
) prepared by atomic layer deposition (ALD) is successfully demonstrated for the first time as a novel work function (WF) metal for nMOSFET applications. The prepared ErC
₂
shows a very low effective WF (eWF), as low as 3.9 eV on HfO
₂
, yet with excellent thermal stability. In addition, it did not show significant Fermi-level pinning on high-k dielectrics even after high-temperature annealing. The low eWF property of ErC
₂
originates from the properties of the lanthanide family, while its good thermal stability is attributed to the properties of metal carbides. ALD-ErC
₂
has superior conformality over other deposition methods, and thus is a strong candidate for 3-D structure devices.