ALD La-based oxides for vt-tuning in high-k/metal gate stacks

Accurate thickness and composition control for ultra-thin films is demonstrated for the atomic layer deposition (ALD) of La2O 3 and HfLaO. Growth studies indicate a linear growth without substrate inhibition for La2O3 and HfLaO ALD on HfSiO and hydroxylated SiO2, respectively. Layer closure studies on HfSiO show a fast La2O3 layer closure. Vt-tuning in a high thermal budget NMOS transistor flow is established (i) by inserting sub-nm La2O3 capping layers between the HfSiON gate oxide and the TaCx metal electrode and (ii) by replacing the HfSiON gate oxide film by HfLaO. Changing the La2O3 capping layer thickness from 0 till 1 nm, results in tunable Vtshifts up to ∼ 600mV while retaining low equivalent oxide thickness (EOT), high mobility, and low gate leakage current. Hf-rich HfLaO gate dielectric layers resulted in a V t-shift of ∼ 250 mV and EOT values down to 1.1 nm. © The Electrochemical Society