P‐7.18: Effect of gate materials and stack structure on threshold voltage of ADS Pro TFT

TFT Vth is affected by gate material, thickness and film structure. If the Al/Mo electrode is added to bottom Mo, or Al is changed to Cu, the work function of Gate increases, that is, the flat band voltage increases, and finally Vth increases. As the gate thickness increases, the gate insulator at the profile position becomes thinner, resulting in a decrease in Vth. MoNb/Cu electrode is covered with top MoNb, which inhibits the diffusion of Cu to gate insulator(GI) and reduces the dielectric loss of GI, so that Vth decreases. At the same time, Cu diffuse to GI layerr, resulting in the positive Vth shift under negative gate stressing. Once MoNb/Cu is covered with top MoNb, the diffusion of Cu ions is inhibited, Vth gradually shifts in the negative direction under negative gate stressing and the positive Vth shift is smaller under positive gate stressing, which indicates that TFT is more stable.