TFT Characteristics Research Articles

Synthesis, oxide formation, properties and thin film transistor properties of yttrium and aluminium oxide thin films employing a molecular-based precursor route.

Combustion synthesis of dielectric yttrium oxide and aluminium oxide thin films is possible by introducing a molecular single-source precursor approach employing a newly designed nitro functionalized malonato complex of yttrium (Y-DEM-NO21) as well as defined urea nitrate coordination compounds of yttrium (Y-UN 2) and aluminium (Al-UN 3). All new precursor compounds were extensively characterized by spectroscopic techniques (NMR/IR) as well as by single-crystal structure analysis for both urea nitrate coordination compounds. The thermal decomposition of the precursors 1–3 was studied by means of differential scanning calorimetry (DSC) and thermogravimetry coupled with mass spectrometry and infrared spectroscopy (TG-MS/IR). As a result, a controlled thermal conversion of the precursors into dielectric thin films could be achieved. These oxidic thin films integrated within capacitor devices are exhibiting excellent dielectric behaviour in the temperature range between 250 and 350 °C, with areal capacity values up to 250 nF cm−2, leakage current densities below 1.0 × 10−9 A cm−2 (at 1 MV cm−1) and breakdown voltages above 2 MV cm−1. Thereby the increase in performance at higher temperatures can be attributed to the gradual conversion of the intermediate hydroxy species into the respective metal oxide which is confirmed by X-ray photoelectron spectroscopy (XPS). Finally, a solution-processed YxOy based TFT was fabricated employing the precursor Y-DEM-NO21. The device exhibits decent TFT characteristics with a saturation mobility (μsat) of 2.1 cm2 V−1 s−1, a threshold voltage (Vth) of 6.9 V and an on/off current ratio (Ion/off) of 7.6 × 105.

Influence of Deposition Temperature and Source Gas in PE-CVD for SiO2 Passivation on Performance and Reliability of In–Ga–Zn–O Thin-Film Transistors

In this paper, we investigated the influence of both source gas and deposition temperature in plasma-enhanced chemical vapor deposition (PE-CVD) for a SiO2 passivation layer on the electrical properties and reliability of a bottom-gate In–Ga–Zn–O thin-film transistor (IGZO TFT). Two gas chemistries consisting of SiH4–N2O–N2 and tetraethoxysilane (TEOS)–O2 were utilized as the source gases for the PE-CVD SiO2 deposition, and the deposition temperature ( ${T}_{D}$ ) was adjusted from 180 °C to 380 °C. The TFT properties were basically identical for both gas chemistries at ${T}_{D}$ of 180 °C. When ${T}_{D}$ increased to 300 °C or higher, the TFTs with the SiO2 passivation deposited by SiH4–N2O–N2 gas chemistry (SiH4-SiO2) drastically changed from the transistor to the conductor. In contrast, the TFT with TEOS-SiO2 passivation maintained its TFT characteristics even at ${T}_{D}$ of 380 °C, despite the degradation of subthreshold characteristics and a negative shift of turn-on voltage were observed due to an electron injection barrier lowering as ${T}_{D}$ increased to 310 °C or higher. We also revealed that a stacked SiO2 passivation that is deposited at a different ${T}_{D}$ is an effective technique to improve the performance and reliability of the IGZO TFT.

One‐Step Fabrication of Hydrophobic Hybrid Gate Dielectrics for Low‐Voltage Organic Thin‐Film Transistors

We report here on the design, processing, and dielectric properties of low surface energy organic/inorganic hybrid dielectric films for low‐voltage operation of organic thin‐film transistors (OTFTs). The hydrophobic hybrid dielectric films are easily fabricated by one‐step spin coating of a zirconium chloride precursor in an octadecyltrimethoxysilane solution under ambient conditions, followed by thermal curing at low temperatures (approximately 150°C). These novel dielectrics exhibit excellent surface smoothness (root‐mean‐square roughness is <0.5 nm), great insulating property (leakage current densities <10−6 A/cm2), and high capacitance (365 nF/cm2). In addition, the surface nature of the hybrid dielectric is hydrophobic (water contact angle is 105°), without any further surface modifications, which is highly compatible with organic semiconductors. Consequently, the hybrid dielectrics integrated into the pentacene OTFTs function at relatively low voltages (< −2.5 V) with excellent TFT characteristics (mobility: 0.31 cm2/V·s, on/off current ratio: 105, low threshold voltage: down to −0.7 V).

28‐2: A Novel OLED Display Panel with High‐Reliability Integrated Gate Driver Circuit using IGZO TFTs for Large‐Sized UHD TVs

We present a novel OLED display panel with high‐reliability integrated gate driver circuit using IGZO TFTs. Our gate driver circuit can drive a large‐sized OLED display not only for displaying images but also for sensing TFT characteristics for external compensation. It functions correctly even when the threshold voltage of TFTs is negative by reducing leakage currents. We have achieved a life time longer than 60,000 hours in a reliability test and successfully applied it to 55‐inch UHD, 65‐inch UHD and 55‐inch FHD OLED displays, which improves cost‐competitiveness of OLED displays against LCDs.

P‐1.8: External Compensation for TFT Vth&Mobility Using Linear Charge Sense Method in AMOLED Display

A new method for Sense and Calculate TFT characteristics is simulated with 3T1C structure of AMOLED display. By using data programming compensation, it can correct both Vth and Mobility. The proposed method uses Linear Charging Method which has faster charging speed than Source Follower Method. By increasing the Vgs of driving TFT, we can even reduce the charging time to 0.5ms. And fast charging make it possible to achieve real‐time detection in higher and higher resolution display. The principle of the method will be described in detail and giving out the simulation data. The experiments are carried out in a 31‐inch AMOLED panel.

The GIDL Current Characteristics of P-Type Poly-Si TFT Aged by Off-State Stress

The GIDL Current Characteristics of P-Type Poly-Si TFT Aged by Off-State Stress

Electrical Characteristics of Fluorine-Doped Zinc Oxynitride Thin-Film Transistors

In this work, an alternative type of high mobility semiconductor, zinc oxynitride (ZnON), is studied by both theoretical calculations and experimental evaluation of thin films and TFT devices. It is demonstrated that the addition of fluorine, in ZnON, removes the formation of nitrogen vacancies, and significantly improves electrical characteristics of the ZnON TFT.

Flexible, Low-Power Thin-Film Transistors Made of Vapor-Phase Synthesized High-k, Ultrathin Polymer Gate Dielectrics.

A series of high-k, ultrathin copolymer gate dielectrics were synthesized from 2-cyanoethyl acrylate (CEA) and di(ethylene glycol) divinyl ether (DEGDVE) monomers by a free radical polymerization via a one-step, vapor-phase, initiated chemical vapor deposition (iCVD) method. The chemical composition of the copolymers was systematically optimized by tuning the input ratio of the vaporized CEA and DEGDVE monomers to achieve a high dielectric constant (k) as well as excellent dielectric strength. Interestingly, DEGDVE was nonhomopolymerizable but it was able to form a copolymer with other kinds of monomers. Utilizing this interesting property of the DEGDVE cross-linker, the dielectric constant of the copolymer film could be maximized with minimum incorporation of the cross-linker moiety. To our knowledge, this is the first report on the synthesis of a cyanide-containing polymer in the vapor phase, where a high-purity polymer film with a maximized dielectric constant was achieved. The dielectric film with the optimized composition showed a dielectric constant greater than 6 and extremely low leakage current densities (<3 × 10-8 A/cm2 in the range of ±2 MV/cm), with a thickness of only 20 nm, which is an outstanding thickness for down-scalable cyanide polymer dielectrics. With this high-k dielectric layer, organic thin-film transistors (OTFTs) and oxide TFTs were fabricated, which showed hysteresis-free transfer characteristics with an operating voltage of less than 3 V. Furthermore, the flexible OTFTs retained their low gate leakage current and ideal TFT characteristics even under 2% applied tensile strain, which makes them some of the most flexible OTFTs reported to date. We believe that these ultrathin, high-k organic dielectric films with excellent mechanical flexibility will play a crucial role in future soft electronics.

Improvement of Electrical Characteristics of a-InSnZnO TFT Using Hydrogenated Gate Dielectric

Improvement of Electrical Characteristics of a-InSnZnO TFT Using Hydrogenated Gate Dielectric

15-2 酸化物半導体TFT特性の半導体膜厚依存性(第15部門情報ディスプレイ)

15-2 酸化物半導体TFT特性の半導体膜厚依存性(第15部門情報ディスプレイ)

3B11 分子配向性有機絶縁膜上への有機半導体薄膜の作製とその有機TFT特性への影響(分子配向エレクトロニクス,口頭発表,2015年日本液晶学会討論会)

3B11 分子配向性有機絶縁膜上への有機半導体薄膜の作製とその有機TFT特性への影響(分子配向エレクトロニクス,口頭発表,2015年日本液晶学会討論会)

The Oxide TFT By Anodic Oxidation

Oxide-TFTs (thin film transistors) have been studied and are being applied to the AMLCD and AMOLED. One advantage of the oxide TFT is higher mobility than amorphous silicon TFT. The oxide material such as IGZO (indium gallium zinc oxide) is sputtered for the active layer. In this experiment, we used anodic oxide instead of sputtered oxide layer. Anodizing is to oxidize the metal by applying the positive voltage to the metal in the electrolyte. Al and Ti metals were anodized and the anodization is possible even at room temperature. There are two ways of the anodization, one is the barrier type and the other is the porous type. For the electrical device application, a barrier type anodic oxidation is necessary. In the case of Al, thickness of the barrier type anodic oxide is proportional to the anodizing voltage in the electrolyte of citric acid. The oxidation starts at a constant current mode and changes to the constant voltage mode. The anodic oxide of Al was used for the gate insulator of the oxide TFTs. On a glass substrate, gate electrode was patterned after deposition of Al by DC-Sputtering. The Al was anodized to form an Aluminum oxide for the gate insulator. After deposition of Ti, it was patterned for the source/drain electrodes and an active region. After coating photoresist, it was opened on the region where the metal should be anodized to be an active region. The oxidized region of the Ti becomes the active region of the TFT. After removing the photoresist, it was annealed under the oxygen ambient to improve the TFT characteristics. During the anodization, the adhesion of the photoresist to the metal was deteriorated and the anodic oxidation occurred under the photoresist. To solve the problem, we deposited silicon oxide before coating the photoresist. After developing photoresist for the opening of the photoresist, the wet etching of the silicon oxide was performed, which made it possible to accomplish the anodic oxidation without the adhesion problem.

Improvement of Stress Stability in Back Channel Etch-Type Thin Film Transistors with Post Process Annealing

The chemical states and electronic structures near the back channel surfaces of amorphous In-Ga-Zn-O (a-IGZO) thin films were investigated by means of x-ray photoelectron spectroscopy (XPS) and photoinduced transient spectroscopy (PITS). The XPS analysis revealed that, due to source/drain (S/D) wet-etching, sub-gap states formed continuously near the valence band, which induced the degradation of the TFT characteristics. According to the PITS analysis, an increase in the hydrogen-related traps in a-IGZO thin films was clearly observed after the S/D wet-etching. The XPS spectra suggested that an increase in OH bonds at the back channel surface resulted in an improvement of stress stabilities such as negative bias, thermal and illumination stress environment.

ITO像素电极工序对于HADS 产品TFT特性的影响

ITO像素电极工序对于HADS 产品TFT特性的影响

Ambient Constancy of Passivation-Free Ultra-Thin Zinc Tin Oxide Thin Film Transistor

An ultra-thin (5 nm-thick), unpassivated zinc tin oxide (ZTO) thin-film transistor TFT, fabricated with solution process, exhibits a good field-effect mobility (13 ∼ 14 cm2/Vs), small subthreshold swing (∼0.30 V/dec.) and high on/off current ratio (∼108). The field-effect mobility can be further enhanced by increasing the ZTO thickness to 12 nm and 22 nm. Furthermore, ID-VG characteristics of the 5 nm-thick ZTO TFT remain unaffected, regardless of working in air (60% relative humidity), vacuum or dry O2 atmosphere. The dissimilar TFT characteristics are discussed in terms of oxygen deficiency content, as well as the Fermi level position (EF to EC) for ZTO of various thicknesses to explain the moisture immunity of the 5 nm-thick solution-processed ZTO TFT. © The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. [DOI: 10.1149/2.0051512ssl] All rights reserved.

Analyses of Surface and Interfacial Layers in Polycrystalline &lt;formula formulatype="inline"&gt;&lt;tex Notation="TeX"&gt;$\hbox{Cu}_{2}\hbox{O}$&lt;/tex&gt;&lt;/formula&gt; Thin-Film Transistors

Effects of low temperature $({\hbox{300}}^{\circ}\hbox{C})$ annealing on $\hbox{Cu}_{2}\hbox{O}$ films were investigated by analyzing the film stacking structures with photoemission spectroscopy, X-ray reflectivity spectroscopy and spectroscopic ellipsometory in relation to $p$ -channel TFT characteristics and possible origins of trap states. The Hall mobility of optimum $\hbox{Cu}_{2}\hbox{O}$ films was ${\hbox{2.1}}~\hbox{cm}^{2}/(\hbox{V}{\cdot}\hbox{s})$ ; however, the bottom-gate $\hbox{Cu}_{2}\hbox{O}$ TFT exhibited a much lower field effect mobility of the order of 10 $^{-4}~\hbox{cm}^{2}/(\hbox{V}{\cdot}\hbox{s})$ and an on/off drain current ratio of 10 $^{3}$ . This work detected a surface layer and an interface layer in the $\hbox{Cu}_{2}\hbox{O}/~\hbox{SiO}_{2}$ samples, i.e., the surface layer included the $2+$ state of Cu ions that would form subgap hole trap states at the back channel region. In addition, the low-density layer at the $\hbox{Cu}_{2}\hbox{O}{\hbox{--}}\hbox{SiO}_{2}$ interface would produce extra interfacial trap states.

P‐6: Impact of Buffer Layers on the Self‐Aligned Top‐Gate a‐IGZO TFT Characteristics

In this work we present the impact of buffer layers deposited by various techniques such as plasma enhanced chemical deposition (PECVD), physical vapor deposition (PVD) and atomic layer deposition (ALD) techniques on self‐aligned (SA) top gate amorphous‐Indium‐Gallium‐Zinc‐Oxide (a‐IGZO) TFT characteristics. Finally an optimized layer was integrated in TFT backplane on polyimide (PI) foil and a QQVGA AMOLED display is demonstrated.

29.2: Silicon Ink‐Based Poly Si CMOS TFT Fabricated on 300mm Stainless Steel Foil Substrates

Laser crystallized CMOS TFTs were fabricated on thin 300 mm stainless steel substrates using novel coated silicon in a Printed Dopant PolySilicon (PDPS) process‐flow [1]. Silicon ink will be a key building block for low‐cost, continuous large‐area coating or printing in very high‐volume roll‐to‐roll manufacturing. RF devices with PECVD‐equivalent TFT characteristics using semiconductor‐grade inks are routinely fabricated using this process. This technology is foundational to low‐cost, high‐volume, RF (13.56MHz), display and integrated sensor system circuits on thin, large‐area flexible and durable substrates.

P‐3: A New LTPS Pixel Circuit for Compensating the Variation of TFT Characteristics and Alleviating OLED Degradation

In this paper, we have developed a pixel compensation circuit that utilizes six LTPS TFTs and one capacitor for AMOLED displays by voltage‐programmed method. The proposed pixel circuit can compensate the threshold voltage variation of TFT and extend OLED lifetime, which is able to show better compensation performances.

Pixel Circuit with Threshold Voltage Compensation using a-IGZO TFT for AMOLED

A threshold voltage compensation pixel circuit was developed for active-matrix organic light emitting diodes (AMOLEDs) using amorphous indium-gallium-zinc-oxide thin-film transistors (a-IGZO-TFTs). Oxide TFTs are n-channel TFTs; therefore, we developed a circuit for the n-channel TFT characteristics. The proposed pixel circuit was verified and proved by circuit analysis and circuit simulations. The proposed circuit was able to compensate for the threshold voltage variations of the drive TFT in AMOLEDs. The error rate of the OLED current for a threshold voltage change of 3 V was as low as 1.5%.