Fa-Hsyang Chen

Impact of Ti doping in Sm2O3 dielectric on electrical characteristics of a-InGaZnO thin-film transistors

We investigated the impact of Ti doping in the Sm2O3 dielectric on the electrical stress-induced instability in amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs). With increasing stress time in a-IGZO TFT devices, a small initial positive shift followed by a negative shift of threshold voltage is characterized in the Sm2O3 dielectric, whereas only positive shift of threshold voltage is observed for Ti-doped Sm2O3 dielectric. The positive shift of the threshold voltage can be explained by charge trapping in the Sm2O3 film and/or the Sm2O3/IGZO interfaces, while the negative shift of threshold voltage is probably due to the extra charges from the IGZO channel by self-heating effect.

Comparison of High-

In this paper, we compared the structural and electrical properties of high- κ Gd₂O₃ and GdTiO₃ gate dielectrics for an amorphous indium-gallium-zinc oxide ( α-IGZO) thin-film transistor (TFT) application. In comparison with the Gd₂O₃ dielectric, the α-IGZO TFT featuring the GdTiO₃ dielectric exhibited better electrical characteristics in terms of a large field effect mobility of 26.9 cm²/Vs, a low threshold voltage of 0.04 V, a high ION/IOFF ratio of 1.2×10⁸, and a low subthreshold swing of 200 mV/decade. We attribute these results to the incorporation of Ti into the Gd₂O₃ film, forming a smooth surface and thus reducing density of interface states at the oxide/channel interface. In addition, the stability of threshold voltage on high- κ Gd₂O₃ and GdTiO₃ a-IGZO TFTs was studied under positive gate bias stress.

\kappa~{\rm Gd}_{2}{\rm O}_{3}

In this study, we report the structural and electrical characteristics of high-κ Sm2O3 and SmTiO3 charge trapping layers on an indium–gallium–zinc oxide (IGZO) thin-film transistor (TFT) for non-volatile memory device applications. The IGZO TFT non-volatile memory featuring a SmTiO3 charge trapping layer exhibited better characteristics, including a larger memory window (2.7 V), long charge retention time (105 s with charge loss <15%) and better endurance performance for program/erase cycles (104), compared with a Sm2O3 charge trapping layer. These results can be attributed to the SmTiO3 film possessing a high dielectric constant and deep trapping level. The high-κ SmTiO3 is an excellent candidate for use as the trapping layer in IGZO TFT non-volatile memories.

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We investigate the electrical stress-induced instability in amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs) with Sm2O3 gate dielectrics. Tow-step electrical degradation behavior in Sm2O3 a-IGZO TFT devices was found under high gate and drain voltage stress during 1000 s. A typical small positive shift followed by an unusual negative shift of threshold voltage is characterized in our TFT devices. We believe that the positive shift of the threshold voltage is due to charge trapping in the gate dielectric and/or at the channel/dielectric interfaces, while the negative shift of threshold voltage can be attributed to the generation of extra electrons from oxygen vacancies in the a-IGZO channel. We suggested that the amount of oxygen vacancies and the quality of the high-κ gate dielectric probably affect the degradation behavior of a-IGZO TFT devices.

{\rm GdTiO}_{3}~\alpha

In this brief, a high-performance amorphous InGaZnO (α-IGZO) thin-film transistor (TFT) with a HfO₂/Lu₂O₃/HfO₂ (HLH) sandwich gate dielectric is demonstrated for the first time. Compared with the Lu₂O₃ dielectric, the α-IGZO TFT device using an HLH sandwich gate dielectric exhibited a low threshold voltage of 0.43 V, a high field-effect mobility of 17.2 cm² /Vs, a small subthreshold swing of 104 mV/decade, and a high I_ON/I_OFF current ratio of 3.08 × 10^-7, presumably because of the reduction of surface roughness at the dielectric-channel interface. Furthermore, the reliability of voltage stress can be improved using an HLH sandwich dielectric structure.

-InGaZnO Thin-Film Transistors

In this study, we developed an amorphous indium-gallium-zinc oxide (α-IGZO) thinfilm transistor (TFT) incorporating high-κ Sm₂TiO₅ gate dielectrics. The high-κ Sm₂TiO₅ α-IGZO TFT after annealing at 400°C exhibited very good electrical characteristics, such as a high I_on/off ratio of 5.27×10⁷, a high field-effect mobility of 27.8 cm²/V-sec, a low threshold voltage of 0.2 V, and a low subthreshold swing of 136 mV/decade. These results are probably due to the incorporation of Ti into the Sm₂O₃ film, resulting in the formation of good Sm₂TiO₅ gate dielectric and low density of interface states at the oxide/channel interface.

Electrical characteristics of gallium–indium–zinc oxide thin-film transistor non-volatile memory with Sm2O3 and SmTiO3 charge trapping layers

In this paper, we propose Al/SiO₂/Dy₂O₃/ SiO₂/ Si, Al/SiO₂/DyTi_xO_y/SiO₂/Si, and Al/Al₂O₃/DyTi_xO_y/SiO₂/Si as charge-trapping memory devices incorporating high-<i>k</i> Dy₂O₃ and Ti-doped Dy₂O₃ films as charge-trapping layers, and SiO₂ and Al₂O₃ films as blocking layers. The Al/Al₂O₃/DyTi_x O_y/ SiO₂/Si memory device exhibited a larger memory window of ~4.5 V (measured at a sweep voltage range of ±9 V), a smaller charge loss of ~20% (measured time up to 10⁶s and at 85^°C), and better endurance (program/erase cycles up to 10⁴) than other devices. These results suggest higher probability for trapping the charge carrier due to the Ti content in the Dy₂O₃ film, which produce a high dielectric constant and suppress the formation of the Dy-silicate layer, and create a deep trap level in the DyTi_xO_y film.

Investigation of tow-step electrical degradation behavior in a-InGaZnO thin-film transistors with Sm2O3 gate dielectrics

In this paper, a HfO2/Er2O3/HfO2 (HEH) stacked structure was developed as a gate dielectric for amorphous InGaZnO (α-IGZO) thin-film transistor (TFT) applications. Atomic force microscopy and X-ray photoelectron spectroscopy were used to study the morphological and chemical features of Er2O3 and HEH films. In comparison to the Er2O3 dielectric, the α-IGZO TFT device incorporating a HEH stacked dielectric exhibited a lower threshold voltage of 0.7 V, a higher Ion/Ioff current ratio of 2.86 × 107, a larger field-effect mobility of 15.8 cm2 V−1 s−1, and a smaller subthreshold swing of 101 mV per dec, suggesting a smooth surface at the dielectric-channel interface. Furthermore, the threshold voltage stability of α-IGZO TFT under positive gate voltage stress can be improved by using a HEH stacked structure.

High-Performance Amorphous InGaZnO Thin-Film Transistors With HfO 2 /Lu 2 O 3 /HfO 2 Sandwich Gate Dielectrics

In this study, we develop a high-performance metal-insulator-metal (MIM) capacitor using a high- k Lu2 O3 amorphous film for radio-frequency and mixed-signal applications. The Ni/ Lu2O3/TaN capacitor exhibited a high capacitance density, a low leakage-current density, and a relatively low quadratic voltage coefficient of capacitance. The leakage current at the low electric field (<; 1.4 MV/cm) was dominated by the Schottky emission, whereas the Poole-Frenkel effect plays in the high electric field. In addition, the effects of constant voltage stress on leakage current and voltage linearity were comprehensively investigated, and excellent device reliability was also demonstrated. The Ni/ Lu2O3/TaN MIM capacitor appears to be very promising for future IC technologies.