Effect of Nitrogen Doping on Elevated-Metal Metal-Oxide (EMMO) Thin-Film Transistors
Nannan Lv, Zening Wang, Mengjun Du, Huaisheng Wang, Dongli Zhang, Man Wong, Mingxiang Wang
Abstract
Nitrogen doping is introduced in elevated-metal metal-oxide (EMMO) thin-film transistors (TFTs) by sputtering amorphous indium gallium zinc oxide (a-IGZO) channel in Ar and N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> gas mixture. The electrical characteristic and reliability of TFTs under negative/positive bias illumination stress (N/PBIS) are systematically investigated on TFTs of different channel lengths ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${L}\text{s}$ </tex-math></inline-formula> ). Compared with undoped TFTs, the short-channel effect (SCE) of the N-doped TFTs is significantly suppressed, the persistent photoconductivity (PPC) effect is weakened, and N/PBIS reliability is largely improved. Short- and long-channel N-doped TFTs have about the same reliability performance. X-ray photoelectron spectroscopy (XPS) analysis shows that N-doping forms Zn=N bonds in the channel and oxygen vacancies ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{O}$ </tex-math></inline-formula> ) are reduced. Based on a group of TFTs with different <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${L}\text{s}$ </tex-math></inline-formula> , channel mobility ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu _{{\mathrm {ch}}}$ </tex-math></inline-formula> ) and source–drain series resistance ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}_{{\mathrm {sd}}}$ </tex-math></inline-formula> ) are correctly extracted. In N-doped TFTs, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu _{{\mathrm {ch}}}$ </tex-math></inline-formula> has a limited decrease owing to the increase in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}_{{\mathrm {sd}}}$ </tex-math></inline-formula> . N-doped TFTs with different Ar/N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> gas-flow ratios show similar electrical and reliability performance, indicating a wide process window.