Atomic-Layer-Deposited In-Sn-O Thin-Film Transistors With Robust Thermal Stability at 400 C and Downscaling of Channel

Ultrathin indium tin oxide (ITO) films are investigated for back-end-of-line (BEOL) compatible thin-film transistors (TFTs) by plasma-enhanced atomic layer deposition (PEALD). By optimizing the ITO channel composition and thickness and a novel post-channel annealing (PCA) process, the resulting TFT exhibits high performance (mu(FE)= 28.3 cm(2)/V center dot s, V-th = -0.29 V, SS = 123 mV/dec, and I-ON/I-OFF = 8.1 x 10(9)) and especially extraordinary thermal stability. The thermal treatment at 400 degrees C for 60 min in N-2 only generates very small variations of -0.17 V and -1.4% for V-th and mu(FE), respectively. Moreover, the optimized device also shows excellent positive/negative bias temperature stress (PBTS/NBTS) stabilities even at 2 MV/cm and 125 degrees C. Furthermore, when the channel length is reduced to 60 nm, the outstanding electrical performance is demonstrated, such as an I-ON/I-OFF similar to 10(10), an I-ON of 715 mu A/mu m, and an R-C of 0.542 Omega center dot mm. Thus, our work provides a promising candidate for BEOL compatible transistors in monolithic 3-D integration.