Electrical properties and thermal stability of MOCVD grown Ru gate electrodes for advanced CMOS technology

This paper presents an overview of electrical properties measured on advanced gate stacks consisting of a Ru electrode and Hf-based gate dielectrics. The gate stack is projected for application in the sub 45 nm complementary metal-oxide-semiconductor (CMOS) technology node. Ru films were grown by metal-organic chemical vapour deposition (MOCVD) on thin HfO2, HfSiOx, HfSiON and SiO2 (control sample) dielectrics. As-deposited and forming gas annealed (90% N2 + 10% H2) samples were characterized by means of capacitance–voltage (C–V) and conductance–voltage (G–V) measurements. We discuss variation in dielectric constant, interfacial layer thickness, effective metal work function (Φm,eff), oxide charge density and density of interface traps. Ru shows Φm,eff of ∼5.1 eV for all Ru/Hf-based dielectrics gate stacks. We also investigated the thermal stability of the stacks upon rapid thermal annealing (RTA) in the temperature range 800–1000 °C for 10 s. Samples were analyzed by Rutheford backscattering spectroscopy. The results suggest a limited thermal stability of Ru/Hf-based dielectric gate stack during source/drain activation step.