Integration of 3.4 nm HfO2 into the gate stack of MOS2 and WSe2 top-gate field-effect transistors
One of the main challenges inhibiting the integration of 2D crystals into top-gate field-effect transistors (FETs) is deposition of a uniform, scalable, high-quality dielectric. The most common and controlled method of deposition of thin dielectric films is atomic layer deposition (ALD); however, the inert surface of 2D materials offers no nucleation sites for the ALD precursors, resulting in non-uniform island growth [1-2]. While ALD can be used to grow thick high-k films on 2D crystals such as transition metal dichalcogenides (TMDs) [3-4], ultrathin films (< 5 nm) have not been possible without additional surface modification steps or the addition of a buffer layer [5-8]. In this work, we demonstrate the ability to grow sub-5 nm thick high-k films onto 2D crystals, including MoS2 and WSe2, using plasma-enhanced ALD (PEALD). Furthermore, we analyze the impact of the PEALD process on the 2D crystals and demonstrate the utility of the sub-5 nm films by fabricating top-gate FETs.
