Sub-5-Å La2O3 In Situ Dipole Technique for Large VFB Modulation With EOT Reduction and Improved Interface for HKMG Technology

In this article, an in situ La-dipole technique with atomic-scale atomic layer deposition (ALD) La $_{{\text{2}}}$ O $_{{\text{3}}}$ in laminated high- k dielectric stacks is presented, where the large flat-band voltage ( V $_{{\text{FB}}}$ ) modulation range is observed. Meanwhile, the lower equivalent oxide thickness (EOT) and improvements in other electrical properties are obtained. With the in situ 4.6 Å La $_{{\text{2}}}$ O $_{{\text{3}}}$ under HfO $_{{\text{2}}}$ , a 710 mV V $_{{\text{FB}}}$ negative modulation range and a 0.15-nm EOT reduction are obtained. As for the gate leakage, more than two orders of magnitude decreasing under the same overdrive bias-voltage is achieved, and the same decreasing level of the voltage hysteresis under dual-sweeping is demonstrated for both obviously suppressed trap/detrap electron density ( N $_{{\text{ot}}}$ ) and interface trap density ( D $_{{\text{it}}}$ ) by in situ La-dipole technique. Meanwhile, since the interdiffusion of La atoms and Si atoms was observed by high-resolution transmission electron microscope (HRTEM) image and energy dispersive X-ray (EDX) analysis, an interpretative model with LaSiO $_{{\textit{x}}}$ formation by the element interdiffusion between laminated layer is proposed for explaining of electrical characteristics improvement by in situ La-dipole technique. The results exhibit a promising approach for multiple threshold voltage (multi- V $_{{\text{t}}}$ ) formation and further performance boosting in future nanosheet gate-all-around field effect transistors (NS GAA-FETs).