Yu Chien Chiu

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

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.

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 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.

An Oxygen Gettering Scheme for Improving Device Mobility and Subthreshold Swing of InGaZnO-Based Thin-Film Transistor

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.

Bipolar Conduction in Tin-Oxide Semiconductor Channel Treated by Oxygen Plasma for Low-Power Thin-Film Transistor Application

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.

Gettering Effect Induced by Oxygen-Deficient Titanium Oxide in InZnO and InGaZnO Channel Systems for Low-Power Display Applications

This paper reported the IGZO and IZO thin-film transistor (TFT) with titanium-oxide semiconductor as channel capping layer. After the TiOx Gettering process, the oxygen vacancies in IGZO channel were successfully modified to maximize the carrier concentration and device mobility. The superior transfer characteristics included a low sub-threshold swing of 79 mV/decade, a very high mobility of 68 cm2/V·s, and good on/off-current ratio of 5.61×106. However, the IZO channel with nano-crystallized grains and without Ga atom doping showed unfavorable transistor characteristics. In addition to apparently degraded transfer properties, the spontaneously oxidized TiOx capping layer also lead to an increase of channel parasitic resistance that limits the output driving current. Therefore, we believe that the existence of Ga-O bonds among IGZO channel would be helpful to stabilize oxygen diffusion behavior and electric structure during Gettering process.

Impact of nanoscale polarization relaxation on endurance reliability of one-transistor hybrid memory using combined storage mechanisms

We demonstrate a novel hybrid nonvolatile memory integrated with a charge trapping mechanism and a ferroelectric polarization effect. The hybrid memory features a large threshold voltage window of 2V, fast 20-ns program/erase time, tight switching margin, and long 1012-cycling endurance at 85oC. Such excellent endurance reliability at 85°C can be ascribed to the introduction of charge-trapping node into the design of memory structure that not only weakens temperature-dependent polarization relaxation, but also improves high-temperature endurance reliability.

Performance Enhancements in p-Type Al-Doped Tin-Oxide Thin Film Transistors by Using Fluorine Plasma Treatment

This letter reports on a tin oxide (SnO) thin-film transistor (TFT) with p-type conduction that uses aluminum (Al) doping in the SnO active channel layer. Performance enhancements were further achieved by applying fluorine plasma treatment on the p-type Al-doped SnO channel layer. The effects of the fluorine plasma treatment were also investigated. By tuning the power of the fluorine plasma treatment on the p-type Al-doped SnO channel layer, the optimal TFT device showed a very high on/off current ratio of

One-transistor ferroelectric versatile memory: Strained-gate engineering for realizing energy-efficient switching and fast negative-capacitance operation

2.58\times 10^{\mathrm {6}}

Temperature-Dependent Transfer Characteristics of Low Turn-On Voltage InGaZnO Metal-Oxide Devices With Thin Titanium Oxide Capping Layers

and a low threshold swing of 174 mV/decade, which could be attributed to the passivation effect of the plasma fluorination on the dominant donor-like traps at the SnO/HfO2 interface, as reflected by the suppression of the hysteresis phenomenon, the low density of interface traps, and the small subthreshold swing. The results indicate that the p-type Al-doped SnO TFT device with fluorine plasma treatment has considerable potential for application in future high-performance displays.

High V th enhancement mode GaN power devices with high I D, max using hybrid ferroelectric charge trap gate stack

In this work, we report a ferroelectric versatile memory (FE-VM) with strained-gate engineering. The memory window of high strain case was improved by ~47% at the same ferroelectric thickness, which agrees with the increase of orthorhombic crystallinity. Based on a reliable first principle calculation (FPC), we clarify that the gate strain accelerates the phase transformation from metastable monoclinic to orthorhombic and thus largely enhances the ferroelectric polarization without increasing dielectric thickness. On the other hand, the orthorhombic FE-AFE phase transition plays a key role in realizing negative capacitance (NC) effect at high gate electric field. This 1T strained-gate FE-VM with ferroelectric NC achieves a sub-60-mVdec subthreshold swing (SS) over ~4 decade of ID to provide a 1~10 fA/μm Ioff and >108 Ion/Ioff ratio, which allows for a fast 20-ns P/E switching during 1012 cycling endurance.