In this letter, self-aligned top-gate (SATG) amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs) with an 8.62-nm SiO ₂ gate dielectric grown by conventional plasma enhanced chemical vapor deposition (PECVD) at 300 °C are fabricated. The results show that the ultrathin PECVD SiO ₂ film has excellent dielectric properties, such as a low leakage current density of 10 ⁻⁸ A/cm ² at 2 MV/cm, a high breakdown electric field of 9.3 MV/cm, and an almost independent capacitance of bias frequency. The fabricated SATG a-IGZO TFTs with the ultrathin SiO ₂ gate dielectric exhibit high electrical performances, with major parameters, including a low gate leakage current of 10 ⁻¹³ A, a small subthreshold swing value of 124 mV/decade, a decent field-effect mobility of 10.13 cm ² / $\text{V}\cdot \text{s}$ , and a high ON/OFF current ratio up to 10 ⁸ . Furthermore, the TFTs also show a good electrical stability under positive and negative gate bias stresses.

Electrical characteristics of self-aligned top-gate (SATG) amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) with 4 nm-thick atomic-layer-deposited (ALD) AlO _x gate insulator (GI) are investigated. It is demonstrated that the SATG a-IGZO TFTs present high-performance metrics including a near-ideal subthreshold swing ( SS ) of 60.9 mV/dec, a low off-state current below 10 ⁻¹² A, a positive ${V}_{\text{th}}$ of 0.1 V, and a decent mobility of 14.1 cm ² / $\text{V}\,\cdot $ s. In addition, the TFTs exhibit negligible ${V}_{\text{th}}$ shifts less than 0.02 V against electrical bias stresses. Both high performance and excellent stability are thus simultaneously achieved for the ultrathin GI of amorphous oxide semiconductor (AOS) TFTs.

Magnesium (Mg)-induced metallization of amorphous indium-gallium-zinc-oxide (a-IGZO) films is investigated to develop a self-aligned (SA) top-gate (SATG) a-IGZO thin-film transistor (TFT) technology. The high-conductive and SA a-IGZO source/drain (S/D) regions are well realized by a short time of sputtered deposition of Mg onto the a-IGZO film on a heated substrate, followed by the removal of the spare Mg on the surface in hot water. It is shown that the resistivity of the a-IGZO films is lowered to about 4 x 10⁻³ Ω cm from over 10⁴ Ω cm with a 36-s Mg deposition at 300°C. The metallization effect is believed to be the consequence of a large number of donor-like defects (oxygen vacancies) generated by oxidation-reduction reaction at the interface between the Mg and a-IGZO films. The SATG a-IGZO TFTs fabricated by the proposed technology show excellent electrical characteristics, such as a field-effect mobility of 19.5 cm²V⁻¹s⁻¹, a subthreshold swing of 0.19 V/dec, an on-/off-current ratio of over 10⁹, a low S/D series resistance of 2.1 Ω cm, a small channel length shrinking of around 0.1 μm, and a high stability against electrical stresses.

We herein demonstrate a self-aligned top-gate (SATG) coplanar amorphous InGaZnO (a-IGZO) thin-film transistor (TFT) technology, with the gate length ( ${L}_{\text {g}}$ ) down-scaled to 97 nm, and gate insulator (GI) AlOx to 4 nm (equivalent oxide thickness = 2.4 nm). The fabricated TFT exhibits a large on-current ( ${I} _{\text {ON}}$ ) of $17.9~\mu \text{A}/\mu \text{m}$ , a high on/off current ratio over 109, a positive threshold voltage ( ${V} _{\text {TH}}$ ) of 0.07 V, and a minimum drain-induced barrier lowering (DIBL) of 77 mV/V. The well-maintained performances of the TFTs even in the nanoscale regime can be ascribed to the abrupt homojunction at source-drain sides and high-quality of ultrathin gate insulator of AlOx by atomic layer deposition (ALD). With the excellent scaling metrics and compatibility with modern integrated circuit (IC) process, the developed SATG a-IGZO TFT technology is compatible with the back-end-of-line(BEOL) and 3D integrations of advanced ICs.