High-performance short-channel self-aligned top-gate InSnZnO TFTs with a stacked Al2O3/SiO2 gate dielectric: Elucidating the enhancement mechanisms

• Realization of 1 µm short-channel SATG ITZO TFTs with Al 2 O 3 /SiO 2 stacked GI. • Outstanding electrical performance with suppressed short-channel effects. • Al 2 O 3 /SiO 2 GI passivates interface defects and enhances GI bonding network integrity. • Defect passivation mechanism elucidated via ToF-SIMS and XPS analyses. • Findings guide scaling of SATG oxide TFTs for future semiconductor engineering. Virtual and augmented reality and other next-generation displays require ultrahigh-resolution. This trend, in turn, drives aggressive pixel scaling, necessitating the miniaturization of thin-film transistors (TFTs) that control each pixel. High-performance TFTs that operate reliably in the short-channel regime are therefore essential. Herein, 1-µm short-channel self-aligned top-gate (SATG) In–Sn–Zn–O (ITZO) TFTs incorporating an Al 2 O 3 /SiO 2 dual-layer gate insulator (GI) are realized. The devices are compatible with low-temperature processing and exhibit excellent electrical characteristics: a field-effect mobility of 38.76 cm 2 /Vs, a subthreshold swing of 0.08 V/decade, a threshold voltage of −1.28 V, an on/off current ratio of ∼10 8 , a negligible drain-induced barrier lowering of ≈0 mV/V, and a threshold voltage shift of +0.23 V under negative bias stress. To elucidate the origin of the remarkable performance in these micron-scale Al 2 O 3 /SiO 2 GI devices, the fundamental dielectric properties of the GI were evaluated, and time-of-flight secondary ion mass spectrometry (ToF-SIMS) depth profiling and X-ray photoelectron spectroscopy (XPS) analysis were conducted. The results reveal that in addition to the enhanced insulating properties of the GI, the outstanding performance of the Al 2 O 3 /SiO 2 GI devices is attributable to the dielectric stack, which effectively passivates dangling bond–related defects at the GI–channel interface and strengthens the bonding network and structural integrity of the underlying SiO 2 bulk. Consequently, the high-performance 1-µm-channel SATG ITZO TFTs and the underlying mechanisms identified in this study represent substantial advancements, with implications that extend to the broader field of advanced semiconductors.