Remarkable bias-stress stability of ultrathin atomic-layer-deposited Indium oxide thin-film transistors enabled by plasma fluorination

A low-thermal-budget fabrication approach is developed to realize high-performance fluorine-doped indium oxide (In${}_2$O${}_3$:F) thin-film transistors (TFTs) with remarkable bias-stress stability. The ultrathin transistor channel layer is prepared by a re-developed atomic layer deposition (ALD) process of using cyclopentadienyl indium(I) (InCp) and O${}_2$ plasma to deposit a crystalline In${}_2$O${}_3$ film, followed by a new fluorine doping strategy to use CF${}_4$ plasma to afford the In${}_2$O${}_3$:F layer. As revealed by the density functional theory (DFT) analysis, the fluorine doping can stabilize the lattice oxygen and electrically passivate the problematic V${}_O$ defects in In${}_2$O${}_3$ by forming the F${}_O$F${}_i$ spectator defects. Therefore, the fabricated In${}_2$O${}_3$:F TFTs show simultaneously excellent electrical performance and remarkable bias-stress stability, with high µ${}_{FE}$ of 35.9 cm${}^2$ V${}^{-1}$ s${}^{-1}$, positive V${}_{th}$ of 0.36 V, steep SS of 94.3 mV dec${}^{-1}$, small hysteresis of 33 mV, and small ΔV${}_{th}$ of -111 and 49 mV under NBS and PBS, respectively. This work demonstrates the high promise of the fluorinated ALD In${}_2$O${}_3$:F TFTs for the CMOS back-end-of-line (BEOL) compatible technologies toward advanced monolithic 3D integration. (© 2024 Wiley‐VCH GmbH)