Contact Length Scaling in Dual-Gate IGZO TFTs

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 (similar to 8 x 10(-8) Torr), the contact resistance (RC) is achieved to be as low as 340 Q mu m at an overdrive voltage of 2.5 V with contact resistivity rho C = 1.72 x 10(-7) Omega.cm(2). Scaling the contact length (LC) 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 LC can be scaled down to 20 nm without noticeable performance degradation; in short -channel devices, a shorter L-C (<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 (L-C = 40 nm and L-CH = 40 nm), achieving an ultra -high ION of 68.4 Amu m(-1) (at VG = V-TH+1 V and V-DS = 1 V) and a low SS of 83.4 mVdec(-1).