Hsiao an Hsu

A Flexible IGZO Thin-Film Transistor With Stacked

This letter demonstrates the feasibility of full room temperature InGaZnO thin-film transistor (TFT) using trilayer gate dielectric on flexible substrate. Through integrating high-κ SiO₂/TiO₂/SiO₂ (STS) gate-stack as well as InGaZnO channel thickness modulation, the resulting flexible indium-gallium-zinc oxide (IGZO)/STS TFTs show low threshold voltage of 0.5 V, small subthreshold swing of 0.129 V/decade, high field effect mobility of 76 cm²/Vs , and good I_ON/I_OFF ratio of 6.7×10⁵, which have the potential for the application of high-resolution flexible display.

{\rm TiO}_{2}

We report a high performance indium-gallium-zinc oxide (IGZO)/IGZO:Ti bilayer metal-oxide thin-film transistor (TFT) with a low drive voltage of . Compared with conventional IGZO TFTs, the novel bilayer metal-oxide TFTs through IGZO thickness modulation can reach the lowest off current of 1.6×10-11 A, smallest sub-threshold swing of 73 mV/decade, and highest mobility of 63 cm2/Vs, which may create the potential application for high resolution display.

-Based Dielectrics Fabricated at Room Temperature

The HfTiO/Y₂O₃ stacked dielectric is proposed as the dielectric of metal-insulator-metal (MIM) capacitor. Y₂O₃ is more thermodynamically stable than HfTiO as contacting with TaN electrode. Interfacial layer thickness and leakage current density can be reduced by inserting a thin Y₂O₃ layer between HfTiO and TaN. The negative quadruple voltage coefficient of capacitance (VCC-α) of Y₂O₃ cancels out the positive VCC-α of HfTiO to achieve low VCC-α. The MIM capacitor structure with HfTiO/Y₂O₃ dielectric shows a capacitance density that is higher than 11 fF/μm² and VCC-α that is lower than 1222 ppm/V². The leakage currents at -1 and -2 V are 6.4 and 14 nA/cm², respectively. These results suggest that the HfTiO/Y₂O₃ stacked dielectric is a promising candidate for MIM capacitors.

High Mobility Bilayer Metal–Oxide Thin Film Transistors Using Titanium-Doped InGaZnO

This paper reports an InGaZnO thin-film transistor (TFT) that involves using fully room-temperature gate dielectrics on a flexible substrate. The wide bandgap dielectrics of HfO₂ and Y₂O₃ exhibited favorable adhesion properties on a flexible substrate compared with conventional low-κ SiO₂ film. Based on the experimental results, the room-temperature IGZO/HfO2 TFTs demonstrated effective device integrity, and achieve a low drive voltage of V, a low threshold voltage of 0.46 ±006 V, a low sub-threshold swing of 110 ±6 mV/decade and an extremely high mobility of 60.2 ±32 cm ²/V·s. The excellent performance of this TFT indicated that it demonstrates considerable potential for active-matrix liquid crystal display applications requiring low power consumption and a high driving current.

High-Performance Metal–Insulator–Metal Capacitors With

This study demonstrates the feasibility of producing a tantalum nitride (TaN) thin film as a diffusion barrier and buffer layer for p-type bismuth telluride [(Bi,Sb)2Te3] thermoelectric devices. A network of TaN with nitrogen (N) incorporation is structurally more stable on (Bi,Sb)2Te3 than the conventional Ni diffusion barrier because of less inter-diffusion and a greater likelihood of stoichiometry in the TaN/(Bi,Sb)2Te3 interface. The atomic inter-diffusion between the barrier layers and (Bi,Sb)2Te3 was evaluated in terms of interface adhesion energy using nanoscratching, and proved with first-principles calculations.

\hbox{HfTiO}/\hbox{Y}_{2}\hbox{O}_{3}

In this work, we report a one-transistor (1T) versatile memory; the memory transistor characteristics achieve sub-60-mV/dec operation and considerably low off-state leakage of 10^-15 A/μm at a supply voltage below 0.5V. The versatile memory features DRAM/NVM functions of large ΔV_T window of 2.8V, fast 20-ns speed, 10³s retention at 85°C, and long extrapolated 10¹⁶ endurance at 85°C, which show the potential for 3D memory application with severe requirement on both high density and low power consumption.

Stacked Dielectric

In this study, we investigate the impact of orientated crystalline InGaZnO (IGZO) thin film transistor. To evaluate interface thermodynamic stability of temperature-sensitive IGZO film, the film-structural stabilities of high- and low-indium-content InGaZnO were studied. With increasing annealing temperature up to 700 °C, the crystallinity becomes more pronounced while device electrical characteristics are further improved. We find that the apparently reduced off-state current can be attributed to the formation of c-axis-orientated crystalline located at the X-ray diffraction peak of . The performance improvements include a very low turn-on voltage close to zero voltage, a small subthreshold swing of 130 mV/dec, and a low off-state current of 2.4 × 10−14 A/µm at a low operating voltage of 4 V.

High Mobility Field-Effect Thin Film Transistor Using Room-Temperature High-kappa Gate Dielectrics

This study involved developing a low-power and high-mobility metal-oxide thin-film transistor that incorporated a bilayer IGZO/IGZO:Ti semiconductor material. Compared with control metal-oxide TFTs, the bilayer IGZO TFT through thickness modulation of IGZO:Ti can reach the smallest subthreshold swing (85 mV/decade) and the highest field effect mobility (49 cm2/Vs) at a drive voltage of <;3 V. This performance level improvement can be attributed to the gettering effect caused by the IGZO:Ti capping layer and its dual advantages, which enhance device mobility and improve gate swing.

Structural stability of thermoelectric diffusion barriers: Experimental results and first principles calculations

In this article, we investigate the frequency-dependent voltage nonlinearity effect of high- K Ni/SrTiO 3 /TaN and TaN/SrTiO 3 /TaN radio-frequency (rf) metal-insulator-metal (MIM) capacitors by electrical and thermal stresses. The experimental results demonstrated that the MIM-related capacitance properties, dependence of voltage and frequency, are not only affected by intrinsic dielectric properties but also shared by extrinsic effect, which possibly originated from the oxygen vacancies or electrode polarization. The high work-function Ni electrode can prevent the frequency-dependent voltage coefficient of capacitance characteristics from deterioration under the high temperature or continued voltage-stressing environments.

Low power 1T DRAM/NVM versatile memory featuring steep sub-60-mV/decade operation, fast 20-ns speed, and robust 85°C-extrapolated 10 16 endurance

In this paper, we investigated the bipolar conduction mechanism in thin-film transistors (TFTs) with oxygen plasma treatment on tin-oxide channel. The optimized p-type thin-oxide TFTs showed an on/off ratio of > 104, a threshold voltage of -1.05 V, and a field-effect mobility of 2.14 cm2·V-1·s-1. By increasing the exposure time of oxygen plasma, excess oxygen was incorporated to thin-oxide channel and converted thin monoxide to oxygen-rich n-type thin dioxide, which in turn led to n-type operation. It indicated that oxygen plasma was the critical factor to determine oxygen concentration, oxygen vacancies, metal ions and channel polarity. This proposed oxygen-content tuning through plasma treatment approach shows great promise in simplification of TFT process that can achieve n-type and p-type TFTs under the same device process.