Contact Length Scaling in Dual-Gate IGZO TFTs
Zijing Wu, Jiebin Niu, Congyan Lu, Ziheng Bai, Kaifei Chen, Zhenhua Wu, Wendong Lu, Menggan Liu, Fuxi Liao, Di Geng, Nianduan Lu, Guanhua Yang, Ling Li
Abstract
In this work, the contact length scaling in dual-gate (DG) InGaZnO (IGZO) thin film transistors (TFTs) was experimentally investigated. With source/drain metal of Nickel (Ni) deposited in ultra-high vacuum condition ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim \,\,{8}\times {10} ^{-{8}}$ </tex-math></inline-formula> Torr), the contact resistance ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}_{C}{)}$ </tex-math></inline-formula> is achieved to be as low as <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$340~\Omega \cdot \mu \text{m}$ </tex-math></inline-formula> at an overdrive voltage of 2.5 V with contact resistivity <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\rho _{C}$ </tex-math></inline-formula> = <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${1}.{72}\times {10} ^{-{7}}\,\,\Omega \cdot $ </tex-math></inline-formula> cm2. Scaling the contact length ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${L}_{C}{)}$ </tex-math></inline-formula> from 300 nm to 20 nm is then performed for both long-channel and short-channel DG IGZO TFTs and find that, in long-channel devices, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${L}_{C}$ </tex-math></inline-formula> can be scaled down to 20 nm without noticeable performance degradation; in short-channel devices, a shorter <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${L}_{C}$ </tex-math></inline-formula> (< 30nm) would cause a pronounced performance degradation, including lower current density and worse subthreshold swing. Based on this observation, ultra-scaled high-performance DG IGZO TFTs are fabricated with a record-low contact pitch of 80 nm ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${L}_{C}$ </tex-math></inline-formula> = 40 nm and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${L}_{\textit {CH}}$ </tex-math></inline-formula> = 40 nm), achieving an ultra-high <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}_{\textit {ON}}$ </tex-math></inline-formula> of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$68.4\,\,\mu \text{A}\cdot \mu \text{m}^{-{1}}$ </tex-math></inline-formula> (at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{G} $ </tex-math></inline-formula> = <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\textit {TH}}+1$ </tex-math></inline-formula> V and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\textit {DS}}$ </tex-math></inline-formula> = 1 V) and a low SS of 83.4 mV <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula> dec <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-{1}}$ </tex-math></inline-formula> .