Mobility Enhancement of Monolayer MoS2 Transistors using Tensile-Stressed Silicon Nitride Capping Layers

Strain engineering has played an important role in modern transistor technology, improving mobility in Si devices since the 90 nm node. Tensile silicon nitride (SiNx) capping layers for Si NMOS have been an effective way to enhance mobility by modifying the Si band structure [1]. 2D semiconductors such as mono-layer (IL) MoS2 are also predicted to have improved mobility under tensile strain, by reduction of intervalley scattering and effective mass [2]. However, CMOS-compatible strain techniques have yet to be demonstrated for such 2D semiconductors. Here, we demonstrate improvement in the mobility and on-state current of 1L MoS2 transistors using a high-tensile-stress SiNx capping layer. We achieve up to 47% improvement in back-gated FET (BG-FET) mobility and on-state current, then extend the technique to achieve 33% improved current drive in top-gated FETs (TG-FET), with record saturation current up to 488 µA/µm in a 200 nm long channel.