Suppression of the Short-Channel Effect in Dehydrogenated Elevated-Metal Metal- Oxide (EMMO) Thin-Film Transistors

Abstract

Characteristics of amorphous indium- gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs) are highly dependent on the hydrogen (H) content within the device architecture, for example in the etch-stop layer (ESL) of the elevated-metal metal-oxide (EMMO) TFTs. The serious apparent “short-channel effect (SCE)” was caused by the H diffusion from source/drain (S/D) to channel. Such SCE deterioration can be suppressed by thermal dehydrogenationat a cost of long annealing time, especially for a transistor architecture with a-IGZO S/D covered with H-rich silicon nitride (SiN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> :H) and further capped with metallic H-diffusion barrier. The dehydrogenation efficiency is found to be significantly enhanced by fluorinating the a-IGZO. By optimizing the device architecture and/or the fluorination process to enhance the dehydrogenation, the SCE can be efficiently eliminated with well-maintained performance even for 2 μm-long a-IGZO TFTs.