bluuebunny/crossref_metadata_2025 huggingface dataset:
Imaging Techniques for the Analysis of Silicon Wafers and Solar Cells
Authors: Bothe Karsten , Ramspeck Klaus , Hinken David , Brendel Rolf
Published: October 2008

For large area devices a spatial analysis of local device and material parameters is essentially important. Imaging techniques allowing a fast and contactless analysis with a high spatial resolution have become a versatile characterization tool during the last decade. We present a comprehensive overview over the existing imaging techniques for the analysis of silicon wafers and solar cells utilizing different spectral ranges of photon emission. Additionally, we report on recent studies of local junction breakdown and the emission of light from solar cells under forward and reverse bias using luminescence imaging and dark lock-in thermography. Finally we present a calibration-free dynamic infrared carrier lifetime mapping (dynamic-ILM) technique, yielding images of the carrier lifetime of multi-crystalline silicon wafers within seconds.
Ab-Initio Modeling of Point Defects, Impurities and Diffusion in Silicon
Authors: Windl Wolfgang
Published: October 2008

We have revisited the first-principles calculation of the diffusion coefficient for nitrogen monomers and dimers, both within the dissociative and the direct pair-diffusion picture, using density-functional theory and harmonic transition-state theory. From our current understanding, it seems that the results for the dissociative mechanism are in better agreement with experiment than those for the direct pair-diffusion mechanism. Based on a monomer diffusion coefficient of D(T) = 7.3e-3 exp[-0.53 eV/(kT)] cm^2/s, we calculate for the dissociation diffusion parameter of the dimer P = 1.6e9 exp[-2.4 eV/(kT)] cm^(1/2)s.
Vacancy-Phosphorous Defect Complex in as-grown, Ultra Pure, Float Zone Single Crystal Silicon
Authors: Viscor Petr , Andersen Ole , Clausen Thomas , Ellsmore Paul A. , Jensen Leif
Published: October 2008

Deep levels in single crystal, Float Zone, High Purity Silicon have been studied using Electrical Impedance Spectroscopy. The Vacancy - Phosphorous defect complex with a density of around 6.0*1011 cm-3 has been identified as the main residual deep level present. Its presence has been confirmed by isochronal anneal experiments that correlated well with an earlier, Electrical Paramagnetic Resonance study. Reversible and well correlated changes in the density of residual shallow Phosphorous and V-P defect complex, observed on fast and slow cooling from higher temperatures, gave yet another strong indication of consistency in Vacancy -Phosphorous identification.
Quantum Properties of Defects in Silicon Films
Authors: Milovzorov Dmitry E.
Published: October 2008

Polycrystalline and nanocrystalline silicon are widely used in thin film transistors production for active matrix organic light emitting devices, photodetectors and memory devices. Silicon thin films are studied by using Raman spectroscopy, electron spin resonance, Fourier-transformed infrared spectroscopy, atomic force microscopy, nonlinear laser spectroscopy and conductivity measurements.
What do We Know About Hydrogen-Induced Thermal Donors?
Authors: Simoen Eddy R. , Huang Yuelong , Ma Yue , Lauwaert Johan , Clauws Paul , Rafi Joan Marc , Ulyashin Alexander , Claeys Cor
Published: October 2008

The hydrogen-plasma-accelerated formation of shallow thermal donors in silicon has been studied for a wide range of doping density and interstitial oxygen content [Oi] by electrical and spectroscopic techniques. The plasma-hydrogenated material has been heat treated for different times in the temperature range of 275 to 500 oC. It is shown that besides Oxygen Thermal Donors (OTDs) also hydrogen related Shallow Thermal Donors (STDHs) play a crucial role in the hydrogen-assisted creation of excess carriers. The impact of different factors on the introduction rate of the shallow donors will be discussed, whereby a strong role is played by the doping density and type, i.e., the Fermi level position during the thermal anneal in air. Generally, shallow donor formation is faster in p- compared with n-type Si, which is associated with the different charge state of H. From combined Deep Level Transient Spectroscopy (DLTS) and Fourier Transform Infrared (FTIR) absorption spectroscopy it is concluded that the additional free carriers are contributed by both STDH and OTD centers, so that H not only plays a catalytic role but actively takes part in the donor formation, depending on the experimental conditions. Finally, from our data some conclusions can be made regarding the nature of the STDHs, which is still a matter of debate.
The Role of Vacancies and Oxygen for Setting up an Efficient Getter for Cu and Ni in Silicon Wafers
Authors: Kot Dawid , Kissinger Gudrun , Haeckl Walter , Sattler Andreas , Von Ammon Wilfried
Published: October 2008

In this work, we present results of investigations on Cu and Ni gettering efficiency for Czochralski silicon wafers containing various concentrations of oxygen and vacancies. In order to achieve suitable gettering sites for these impurities, the samples were subjected to a thermal treatment at temperatures in range between 700 {degree sign}C and 1000 {degree sign}C for different times in range between 0.5 h and 8 h. The gettering efficiency of Cu and Ni was determined by haze tests. Threshold values for efficient gettering of Cu and Ni were obtained.
An Investigation of Material Design for Gettering
Authors: Matsukawa Kazuhito , Shirai Koun , Katayama-Yoshida Hiroshi
Published: October 2008

Aimed at searching efficient gettering centers for Cu impurity, we have theoretically studied the gettering efficiency of various complexes composed of light elements, C, B, O and N. Through evaluation of the binding energy of complexes and Cu by first-principles psedopotential method, it is found that complex BsO2i and BsNiO2i serve as the leading gettering centers for Cu impurity.
Digital SPV Diffusion Length Metrology (E8-Fe) for Ultra-High Purity Silicon Wafers
Authors: Wilson Marshall , Savtchouk Alexandre , Tasarov Igor , D'Amico John , Edelman Piotr , Kochey Nick , Lagowski Jacek
Published: October 2008

We discuss a new generation of SPV minority carrier diffusion length metrology with 10-fold improved precision that enables iron detection in silicon wafers in the E8 atom/cm3 range and the extraction of true steady state diffusion length, L0. This improvement is due to full digital control of redesigned hardware and the SPV measuring process. This digital SPV incorporates a novel multi-frequency approach that optimizes Fe detection and extraction of L0. The latter is supported by wafer back surface recombination velocity measurement incorporated in the SPV tool.
Chromium(VI)-free Defect Etching Solutions for Application on Engineered Silicon Substrates
Authors: Maehliss Jochen , Abbadie Alexandra , Brunier Francois , Kolbesen Bernd O.
Published: October 2008

New defect etching solutions for application on engineered silicon substrates are presented which are free of toxic hexavalent chromium. The "FS Cr-free SOI" was developed for revealing crystal defects in silicon-on-insulator (SOI) substrates and proved to be a highly suitable alternative to the Secco etching solution. Another defect etching solution ("thin SOI etch") especially developed for application on very thin SOI films is also characterized in detail. For strained silicon-on-insulator (sSOI) substrates a defect etching solution ("sSOI etch") is introduced which shows an enhanced sensitivity to such low strain fields produced by stacking faults, however, its correlation to the Secco etching solution has to be improved. Besides etching mechanisms and defect delineation processes will be discussed.
New Method for Identifying Yield Impacting Polishing Induced Defects (PID) on Polished Silicon Substrates
Authors: Kim KeunSu , Moon Byeongsam , Suh Hyo Sik , Kim Jiae , Venkat Sivakumar , Lee Sanghyun , Shen William , Shin Yong , Park Jonggeun , An Jeonghoon , Seo Scott , Ku Jachun , Park SungKi , Saito Jason , Douglas Carlotte
Published: October 2008

This paper talks about a new class of yield impacting defect types known as polishing induced defects (PID) on polished silicon substrates. These defects were found to cause significant yield drop associated with a pump bias failure in the sub-60nm flash memory process. Traditional incoming wafer quality analysis methods proved inadequate in detecting these defects. Nor had the problem been detected during outgoing wafer quality analysis at the wafer manufacturing plant. At the fab, SEM and AFM were able to verify the defect issue as PID; however, neither of these techniques is production-worthy for routine inspection of incoming wafers. This called for a new non-destructive methodology that not only enables capturing these defects but also provides an ability to reliably distinguish between these device-killing defects and innocuous particles which can be cleanable. This study utilized KLA-Tencor's Surfscan SP2XP unpatterned wafer inspection system, a tool with unique technology to combine multiple illumination angles and multiple detectors with a Rule Based Binning (RBB) algorithm for effective defect detection and classification. Three different rules were developed to improve the classification of PID vs. particles. All three were based on comparing the ratio of scattering signals between detectors or combinations of detectors
EIS Characterization of Ultra High Purity, Float Zone Single Crystal Silicon
Authors: Viscor Petr , Andersen Ole , Clausen Thomas , Ellsmore Paul A. , Jensen Leif , Schiotz Jakob
Published: October 2008

A comprehensive electrical characterization of a Float Zone High Purity Silicon ingot has been carried out to investigate the fundamental, impurity/defect related aspects of the FZ growth process. Using Electrical Impedance Spectroscopy, a full mapping of deduced electrical characteristics within the ingot was achieved. The spatial density variations of identified impurities and defect complexes throughout the studied ingot have been correlated to the Float Zone molten phase flow pattern and the respective liquid Silicon/solid Silicon and liquid Silicon/gas interfaces.
Estimation of Radiation-Induced Complex Concentration in CZ-Si by IR Absorption Spectroscopy
Authors: Yonezawa Yasuhiro , Inoue Naohisa , Takubo Yoshitaka , Goto Yasunori , Sugiyama Takahide , Kawamura Yuichi , Takeguchi Tohru
Published: October 2008

Radiation induced complexes in low carbon concentration, low electron dose Czochralski silicon crystal are examined by infrared absorption spectroscopy. By using the highly sensitive, highly accurate measurement and arithmetic procedures, carbon-oxygen(-self interstitial)and vacancy-oxygen complexes are detected in samples with carbon concentration about 1x1016 atoms/cm3 and electron dose about 1x1016 atoms/cm2. Also, their concentrations, are estimated by evaluating the relative oscillator strength. Quantitative analysis in high quality samples will provide important information on defect behavior in irradiated crystals.
A Fully Monolithic Wireless Display System
Authors: Zyambo Emmanuel , Lukama Lloyd , Brown Chris , Miyata Kazuhiko , Brownlow Michael
Published: October 2008

We present a fully monolithic wireless interface for mobile displays, fabricated with CG-Silicon thin film transistors. The new interface uses a proprietary technique to wirelessly transfer both the image data and power for the LCD and backlight. Experimental results are presented from a 2.2" QVGA prototype demonstrating 100% wireless operation.
High Performance Short Channel a-Si:H TFT Device with Cu Electrodes
Authors: Yang Joonyoung , Ahn Y. K. , Bang J. H. , Ryu W. S. , Kim J. O. , Kang Y. K. , Yang M. S. , Kang I. B. , Cung I. J.
Published: October 2008

Short channel a-Si:H TFT devices with Cu electrodes have investigated. The short channels are defined by our unique mask pattern and new plasma etch process. When channel length becomes shorter, the TFT characteristics (threshold voltage, off current, sub threshold voltage, etc.,) are degraded. These degraded characteristics are recovered and improved through the hydrogen plasma treatment(off current) and new gate insulator structure(threshold voltage).
Status and Issues of Organic TFT for Display Applications
Authors: Kim C.-D. , Kang I. B. , Chung In-Jae
Published: October 2008

The development status and the technical issues of OTFTs for the future display applications are described and our recent results of the world's first and the highest-resolution OTFT-LCD using the solution process are briefly introduced. To realize the low-cost and large-area display fabrication with OTFT, it is required that the alternative metals to the conventional Au electrode and the printing technology for the organic semiconducting active layer formation are developed.
Direct Fabrication of a-Si:H Thin Film Transistor Arrays on Flexible Plastic Film and Metal Foil Substrates: Critical Challenges and Enabling Solutions
Authors: O'Rourke Shawn , Loy Douglas , Moyer Curt , Bawolek Edward , Ageno Scott , O'Brien Barry , Marrs Michael , Bottesch Dirk , Dailey Jeff , Naujokaitas Rob , Kaminski Jann , Allee David , Venugopal Sameer , Haq Jesmin , Raupp Gregory B.
Published: October 2008

In this paper we describe solutions to effectively address critical challenges in direct fabrication of amorphous silicon thin film transistor (TFTs) arrays for active matrix flexible displays. For both metal foil and plastic flexible substrates a manufacturable handling protocol in automated display-scale equipment is required. We have successfully demonstrated a temporary bonding protocol that required development of new enabling materials, tools and processes. For metal foil substrates, the principal challenges are planarization and electrical isolation, and management of stress (CTE mismatch) during TFT fabrication. For plastic substrates, the principal challenges are dimensional instability management in conjunction with manufacturing-ready temporary adhesives. Solutions required a systems-level approach to address the challenges of the substrates and their handling simultaneously.
Issues in Microcrystalline Silicon TFTs Processed at T<200oC
Authors: Mohammed-Brahim Tayeb , Kandoussi Khalid , Coulon Nathalie , Simon Claude
Published: October 2008

Review of results on microcrystalline silicon thin film transistors is given with emphasis on main issues to get both higher stability and mobility TFTs than that of amorphous silicon transistors. High crystalline fraction with columnar structure is shown to lead to high mobility without stability when using silicon dioxide as gate insulator, or stable TFTs with low mobility when using silicon nitride as gate insulator. Un-stability originates from oxygen that diffuses in defected column boundaries. Using denser structure as crystalline grains embedded in amorphous matrix can lead to TFTs with enough stability and mobility.
Extraction of the Density of Interface Trap States in Thin-Film Transistors
Authors: Tsuji Hiroshi , Kamakura Yoshinari , Taniguchi Kenji
Published: October 2008

In the present study, we propose a new extraction method for the density of interface trap states at the Si/SiO2 interface from thin-film transistors with doped active layers. In developing the proposed method, we derive an equation that describes the interface trap charge density as functions of the surface potentials. Whereas the front surface potential is obtained from the low-frequency CV characteristic, the back surface potential is calculated using the depletion approximation. We confirm the validity of the extraction method using a two-dimensional device simulator.
A DLTS Study of Band Gap States in SLS Poly-Si TFTs
Authors: Michalas Loukas , Papaioannou George , Voutsas Apostolos
Published: October 2008

The experimental knowledge of band gap states density (DOS) is of major importance for the understanding of the electrical properties of poly-Si TFTs. For this reason several methods have been employed over the last three decades. Aim of the present work is to present a new approach for direct experimental determination of DOS based on the Deep Level Transient Spectroscopy (DLTS). The investigation is performed on TFTs fabricated on sequential lateral solidified (SLS) poly-Si films. The results suggest a U-shape continuous distribution of states in the band gap as expected from theoretical predictions and other experimental observations.
Visible Light Source Disturbing the Source/Drain Current of CLC Poly-Si n-TFT Device
Authors: Wang Mu-Chun , Hsieh Zhen-Ying , Chen Chih , Shieh Jia-Min , Lin Yu-Ting , Lee Shio-Chao , Chen S. Y. , Huang H. S.
Published: October 2008

The TFT device is directly exposed by light from backside light source and outside light source beyond the display screen. Therefore, if the impact of extra light intensity possibly produces the instable operation of this device with continuous-wave (cw) laser crystallization (CLC) poly-Si channel, these device characteristics should be examined. For CLC poly-Si n-TFT device, it was fabricated successfully by C. Chen's team (1). This TFT device demonstrates excellent electron mobility, up to 530 cm2/V-s, is greater than that with low-temperature poly-silicon (LTPS) fabrication technology. In this study, the species of the tested light sources with light emitting diodes (LEDs) contained green and blue wavelengths. From the experimental data, we observed while the TFT glass substrate was exposed by a specified LED, some current-voltage (I-V) characteristic curve of this TFT device was slightly shifted or demonstrated a wavelet phenomenon.
Enhanced Drain Current Ripple Variation with Vertical and Horizontal Electrical Fields under Optical Illumination
Authors: Wang Mu-Chun , Hsieh Zhen-Ying , Chu Yin-Chin , Chen Chih , Shieh Jia-Min , Lin Yu-Ting , Lee Shio-Chao , Huang H. S.
Published: October 2008

A continuous-wave (CW) laser-crystallized (CLC) single-grainlike polycrystalline silicon (polysilicon) thin-film transistor (poly-Si TFT) also represents the similar electric characteristics with the mentioned device. Recently, poly-Si n-TFTs had been researched and successfully fabricated by C. Chen's team [1]. This TFT device demonstrates the excellent electron mobility, up to 530 cm2/V-s greater than that with low-temperature poly-silicon (LTPS) fabrication technology. In general, the TFT device is directly exposed by light from backside light source and outside light source beyond the display screen. Using some illuminants shining on the CLC poly-Si TFT, such as light emitting diode (LED), the current-voltage (I-V) characteristic of the TFT shows a current-ripple phenomenon. These interesting ripples actually may be magnified by the supplied drain and gate voltages. In this work, the red color LED was employed and the supplied drain and gate voltages were 0 ~ 7 V and 1 ~ 5 V, respectively.
Instability Behavior of Oxide-based Top-gate TFTs under Electrical and Optical Stress Test
Authors: Cho Junhee , Jeong Jaewook , Lee Ho-Nyun , Kim Hong-Gyu , Kim Sung-tae , Hong Yongtaek
Published: October 2008

We report instability behavior of oxide-based top-gate thin-film transistors under electrical and optical stresses. For electrical stress, transfer curve shifts to the right and left for positive and negative gate stress voltages, respectively, while sub-threshold slope (SS) barely changed for both cases. Although this behavior is consistent with the previously reported oxide-based TFT instability behavior explained by charge trapping mechanism, threshold voltage shift seemed to have power-law-time dependency unlike the previous results. We also tested optical stress behavior of the oxide-based TFTs with a blue power-LED. Under prolonged exposure of 3.5mW/cm2 blue light, both transfer curves under dark and illumination conditions shift to the left, but with significant change in sub-threshold slope for illumination condition. After the electrical and optical stress tests, stress effect was relaxed without any annealing process.
Stability of Microcrystalline Silicon TFTs
Authors: Belarbi Khaled , Kandoussi Khalid , Coulon Nathalie , Simon Claude , Cherfi Rabah , Fedala Abdelkrim , Mohammed-Brahim Tayeb
Published: October 2008

Stability of microcrystalline silicon (µc-Si:H) Top-Gate TFTs processed at T<200oC and using silicon dioxide or silicon nitride as gate insulator is studied. Excellent stability with silicon nitride as gate insulator is shown. The stability of TFTs with silicon dioxide is shown to depend on the thickness and then on the structure of undoped µc-Si:H active layer. TFTs with thick active layer present high mobility but are non stable. When using thin active layer, TFTs become very stable but with lower mobility. This mobility is however much higher than its value for TFTs with silicon nitride. Results show the possibility to increase the present usual low mobility of stable µc-Si:H TFTs, saving in the same time the stability.
Mechanisms of Polycrystalline Growth of SiGe in Thermal CVD Processes using Si2H6 and GeF4
Authors: Kagatsume Akiko , Suzumura Isao , Wakagi Masatoshi , Hanna Jun-ichi
Published: October 2008

The mechanism of SiGe film growth from Si2H6 and GeF4 was examined by ab initio B3LYP/6-31G** calculations using three cluster surface models. Energies of reaction and activation were calculated, and the process of SiGe film growth was analyzed. It was found that the reaction of GeF4 with Si2H6 formed GeF2 by much lower activation energy than decomposition of GeF4. In addition, GeF2 made activation energy of surface reactions lower than using only Si2H6.
Recent Progresses in Ultrahigh-Performance TFT Technologies- Advanced PMELA Method and its TFT Application
Authors: Endo Takahiko
Published: October 2008

Advanced phase-modulated excimer-laser-annealing (PMELA) technology has been reviewed for growing both position-controlled large and shape-controlled long grains. Attractive characteristics of TFTs and their circuits, which were fabricated on PMELA-grown films, were also reviewed.
Crystallinity and Internal Strain of One-Dimensionally Long Si Grains by CW Laser Lateral Crystallization
Authors: Fujii Shuntaro , Kuroki Shin-Ichiro , Zhu Xiaoli , Numata Masayuki , Kotani Koji , Ito Takashi
Published: October 2008

Continuous-wave (CW) laser lateral crystallized silicon (Si) thin films were investigated. CW laser with a wavelength λ of 532 nm was applied to crystallization. In the CW laser lateral crystallization (CLC), a gradual temperature slope in Si thin films was formed and one-dimensionally long grains with a typical length of 20 µm were achieved. The most dominant grain growth direction was <110> direction. ∑3, 9, and 11 boundaries were mainly observed between adjacent grains. It was found that crystallization was performed to form stable grain boundaries. It was also clarified that CLC poly-Si thin films have large tensile strain corresponding to 0.6% of single crystalline Si lattice in in-plane direction. This strain was induced by the difference in thermal expansion coefficients between Si thin films and the buffer SiO2 films.
Formation of Location-Controlled Germanium Grains by Excimer Laser
Authors: Baiano Alessandro , Ishihara Ryoichi , Van der Cingel Johan , Beenakker Kees
Published: October 2008

2D location control of germanium (Ge) grains at different process temperature is obtained using the µ-Czochralski technology. Single Ge grains can reach diameter of 5 or even 8 µm at sputtering temperatures of 100 or 550 {degree sign}C, respectively. Crystalline structure of single Ge grain is confirmed by electron backscattering diffraction.
The AMOSFET - A Simple, High Performance FET for Thin Films, Nanowires, and Nanoribbons
Authors: Garg Pranav , Hong Yi , Iqbal Md Mash-hud , Migliorato Piero , Fonash S. J.
Published: October 2008

The AMOSFET is an extremely simple device configuration yet it is capable of high-performance thereby offering the potential of a significant impact on transistor cost and manufacturability. Initial exploration of S/D contact variations and of the impact of thermal process history are presented.
Highly Stable Bottom-Gate Nanocrystalline Silicon Thin Film Transistor Fabricated Employing ICP-CVD
Authors: Kim Sun-Jae , Han Sang-Myeon , Kwon Jang-Yeon , Jung Ji-Sim , Han M. -K.
Published: October 2008

Bottom-gate nanocrystalline silicon (nc-Si) thin film transistors (TFTs) were fabricated and evaluated their characteristics and electrical stability under various stress condition. nc-Si with high crystallinity was deposited employing Inductively coupled plasma chemical vapor deposition(ICP-CVD) system. We employed helium gas diluted deposition and all the process temperature was kept under 350oC. We fabricated conventional inverted-staggered nc-Si TFTs. Fabricated nc-Si TFTs showed fine electrical characteristics, such as electrical mobility of 0.64~0.77 cm2/V⋅sec. We investigated its stability through constant-voltage stress and constant-current stress. The threshold voltage shift after 30,000 seconds gate bias (10V) stress was only 0.098V, which is considerably less compared to a-Si:H TFT. Under the static current stress condition, the threshold voltage of the nc-Si TFT was shifted less than that of a-Si:H TFT. It demonstrates that nc-Si TFT exhibit better stability than conventional a-Si:H TFT.
Using Chemical Oxide Layer to Getter Nickel inside Nickel-Metal-Induced Lateral Crystallization Polycrystalline Silicon
Authors: Wang Bau Ming , Yang Tzu-Ming , Tseng Ching-Chieh , Wu YewChung Sermon
Published: October 2008

Nickel contamination inside nickel-metal-induced lateral crystallization (NILC) polycrystalline silicon (poly-Si) is an issue to fabricate high performance thin film transistors (TFTs). A simple and effective method for gettering Ni was proposed with ~5-nm-thick chemical oxide (chem-SiO2) as the etching stop layer, and 100-nm-thick amorphous Si as the gettering layer. Ni-gettering process was annealed at 550oC in N2 ambient for only 12 h to considerably reduce Ni-metal impurity within the NILC poly-Si film.
Improving the Electrical Properties of NILC poly-Si Films using Gettering α-Si Film Through Contact Holes
Authors: Hu Chen-Ming , Chao Yu-Cheng , Wu YewChung S.
Published: October 2008

Ni-metal-induced lateral crystallization (NILC) of amorphous Si (α-Si) has been used to fabricate polycrystalline silicon (poly-Si) thin-film transistors (TFTs). However, often leads to trap Ni and NiSi2 precipitates, which degrade the device performance. In this study, α-Si film was coated on the top of contact holes as Ni-gettering layer. It was found that the GETR-TFT exhibited an enhanced field-effect mobility, steeper subthreshold swing, lower minimum leakage current. These improvements are consistent with a measured reduction in the trap state density in the channel.
Effect of Heat-treatment on Reliability of a-Si:H TFTs for Integrated Gate Driver Circuits
Authors: Nam Dae-Hyun , Jeong Seong-Hun , Lee Young-Jang , Jo Sung-Hak , Kim Do-Sung , Moon Hong-Man , Shin Hyun-Ho , Chung In-Jae
Published: October 2008

Reliability of transistors is important to a-Si:H TFTs for integrated gate drivers. Because the life time of a-Si:H TFTs indicates the life time of LCD which adopts a-Si:H TFTs for integrated gate drivers on panel. With bias temperature stress, we could estimate the reliability of a-Si:H TFTs. Threshold voltage shift and decrease of on-current occurred by applying bias temperature stress. In this study, we investigated the effect of heat-treatment on reliability of a-Si:H TFTs for integrated gate drivers. With heat-treatment, the reliability of a-Si:H TFTs was improved and output signal of integrated gate dirivers was fine. This can be explained by that heat-treatment makes number of defect sites in channel reduce and cures the interface of active and gate insulator.
Top-Contact Organic Thin-Film Transistors Fabricated by Picoliter and Sub-Femtoliter Inkjets
Authors: Sekitani Tsuyoshi , Noguchi Yoshiaki , Klauk Hagen , Zschieschang Ute , Someya Takao
Published: October 2008

Employing inkjet technologies with picoliter and sub-femtoliter droplet volumes, we have successfully manufactured high-quality top-contact organic thin-film transistors. Silver fine lines were directly patterned by two inkjet systems on the pentacene channel layer without the need for any photolithographic pre patterning or any surface pretreatment. The lines were calcinated at 130 {degree sign}C to form source and drain electrodes. The minimum width of silver lines was 25 µm with the picoliter inkjet system, while that was 2µm with the sub-femtoliter inkjet system. We have manufactured p-type channel and n-type channel organic transistors with source/drain contacts prepared by the sub-femtoliter inkjet to fabricate complimentary inverter circuits.
Low-Voltage Organic Thin-Film Transistor With High-κ LaYOx Gate Insulator
Authors: Deng Chih-Kang , Cheng Chun-Hu , Chiou Bi-Shiou
Published: October 2008

In this paper, we demonstrated a high-κ LaYOx dielectric into pentacene-based organic thin-film transistor (OTFT). The 30-nm LaYOx film as gate insulator exhibited a high capacitance density of about 410 nF/cm2 and a low gate leakage below 200 nA to induce more accumulated charges in organic channel layer. Therefore, the good device performance could be obtained, such as a low threshold voltage of -1.25V, a low subthreshold swing of 265 mV/dec., and a field-effect mobility of 0.21 cm2/V-s, under 2-V low-voltage operation.
Organic Photo Transistors with Drain Bias Modulation Effect
Authors: Zan Hsiao-Wen , Kao Shih Chin
Published: October 2008

In this paper, the influence of light induced electrons on the threshold voltage shift of organic thin film transistors (OTFTs) was studied. The light induced electrons are formed and accumulated in the channel near the interface of gate dielectric. The light source can be used as second source. Therefore, the study demonstrates the light induced electrons in channel can be affected by drain bias like bias stress. The decreasing accumulated electrons with increasing positive drain bias lower the threshold voltage shift rate during illumination time. The opposite trend can be observed when using negative drain increases accumulated electrons. This result is helpful to adjust the photosensivity of organic photo transistors.
Improved Air-stability of n-Channel Organic Thin Film Transistors via Surface Modification on Gate Dielectrics
Authors: Chen Fang-Chung , Liao Cheng-Hsiang , Huang Wei-Pang , Huang Tom
Published: October 2008

The air-stability of n-channel organic thin film transistors (OTFTs) has been improved by modifying the dielectric surfaces with polymer insulators. The OTFTs were fabricated using N,N'-dioctyl-3,4,9,10-perylene tetracarboxylic diimide (PTCDI-C8) as the active material and SiO2 modified with different polymers as the gate dielectric. Among the polymer insulators, the device modified with hydroxyl-free polymers exhibited the best performance. For example, the electron mobility, 0.11 cm2/Vs, in the saturation region, was obtained in the ambient condition for the device with the SiO2 surface modified with the polymers. The on-off ratio was also as high as 105. More importantly, the devices modified with hydroxyl-free polymers had better air-stability. The improved stability could be attributed to the passivation of the hydroxyl groups (electron trapping sites) on the SiO2 surface.
All-Organic Thin Film Transistor Circuits with Ink-Jet Printed Electrodes
Authors: Kim Jung-Min , Kim Jae-Kyoung , Yoon Tae-Sik , Kim Yong-Sang
Published: October 2008

We have developed a process for fabrication of all-organic thin film transistors (OTFTs) and integrated circuits with ink-jet printed electrodes on PES substrates. OTFTs have a field-effect mobility of μFET= 0.068 cm2/Vs, a sub-threshold voltage of 1.16 V/decade, a threshold voltage Vth= -15 V and on/off current ratio of >104. It is demonstrated that the proposed inverter shows a full-swing characteristic, large inverting gain of around 3.1 and high noise margin with only two OTFTs.
Ink-Jet Printed 6,13-bis(triisopropylsilylethynyl) Pentacene Organic Thin-Film Transistors for Particle Based Electronic Papers
Authors: Kim Yong-Hoon , Park Sung Kyu , Park Sang-Geun , Han M. -K. , Han Jeong-In
Published: October 2008

Ink-jet printed 6,13-bis(triisopropylsilylethynyl) (TIPS) pentacene organic thin-film transistors (OTFTs) were fabricated for particle-based electronic papers. As source and drain electrode, a transparent conductive oxide, indium-tin-oxide (ITO) has been employed instead of using Au electrode. Using the ITO electrode, field-effect mobility of 0.06 cm2/Vs has achieved by improving the contact between the ITO electrode and the organic semiconductor layer. For contact treatment, a combination of O2 plasma treatment and 4-chlorophenyl dichlorophosphate treatment have been used. With the OTFTs employing ITO source/drain electrode, a particle-based electronic paper array was fabricated.
High Performance Organic Thin Film Transistors Made Simple Through Molecular Design and Processing
Authors: Jurchescu Oana D. , Feric Marina , Hamadani Behrang , Mourey Devin , Subramanian Sankar , Purushothaman Balaji , Anthony John , Jackson Thomas , Gundlach David
Published: October 2008

We report on a simple a method of inducing self-isolation of the thin film transistors via manipulation of the chemical interactions between the organic molecules and the surfaces where they are deposited. We use pentafluorobenzenethiol (PFBT) treatment of the contacts and investigate the thin film formation of different types of chemical compounds. In particular, three similar organic molecules: triisopropyl-silylethynyl pentacene (TIPS pentacene), triisopropyl-silylethynyl peri-fluoro-pentacene (TIPS PFP) and triisopropyl-silylethynyl cata-fluoro-pentacene (TIPS CFP), were studied and compared to better understand how the molecular, crystal structure and thin film formation influence the electrical behavior of devices fabricated with them. The molecules exhibit significantly different interactions with the chemically treated substrates. The field-effect mobilities of these devices are directly related to their thin film microstructure.
Ba0.6Sr0.4TiO3 Thin Films used as Gate Dielectric in Pentacene Transistors
Authors: Dong Guifang , Lu Yuexiang , Wang Xiao Yan , Qiu Yong
Published: October 2008

Ba0.6Sr0.4TiO3 thin films have been prepared via sol-gel process and the effect of process temperature on the characteristics of the thin film has also been investigated. It was found that when the pre-treatment and the annealing temperatures were at 350 Celsius degree, a dielectric constant of more than 10 and the leakage current density of 3.5×10^(-8) A/cm^2 at an electric field of 0.3 MV/cm were observed. Using the Ba0.6Sr0.4TiO3 thin film as the gate dielectric, pentacene thin-film transistors were prepared with the current on/off ratio of 1.4x10^4 and the mobility of 0.18 cm^2/V s.
Highly Stable ZnO TFT: Effect of Substrate Buffer Layer
Authors: Park Sang-Hee K. , Hwang Chi-Sun , Ryu Min Ki , Shin Jaeheon , Yang Shinhyuk , Yoon Sung Min , Chu Hye Yong
Published: October 2008

We presented effect of substrate buffer layer on the staggered ZnO TFT performance. Thermal oxide with smooth surface and negligible hydrogen amount forms good back channel with the ZnO active layer deposited by PEALD to result in high performance of ZnO TFT. On the other hand, PECVD SiO2 buffer layer generates some defects in the back channel and make PEALD ZnO have higher carrier density to result in much negatively shifted Von and reduced mobility of TFT. ZnO TFT having sputtered SiO2 as a buffer layer showed similar performance to that with thermal oxide.
High Performacne InGaZnO4-based Thin film Transistors Fabricated at Low Temperature
Authors: Lim Wantae , Wang Yu-lin , Lee Jewon , Norton David P. , Ren F. , Pearton Stephen J.
Published: October 2008

Thin Film Transistors (TFTs) based on amorphous indium gallium zinc oxide (α-IGZO) were fabricated by RF magnetron sputtering on glass substrates. The TFT device structure was a bottom-gate type, consisting of InZnO as electrodes (gate, source and drain) and two different gate dielectrics (HfO2 and SiNx). The resistivities of the α-IGZO films were controlled from 10-1 to 103 Ω-cm by varying the deposition power, 75W to 300W. TFTs with HfO2 displayed saturation mobility of ~ 7.2 cm2.V-1.s-1, threshold voltage of 0.44V, drain current on-to-off ratio of ~ 105, and subthreshold gate-voltage swing of ~ 0.25 V.decade-1. After 500 hours aging time at room temperature, the threshold voltage for HfO2-IGZO TFTs shifted in the positive direction, while SiNx-IGZO TFTs showed almost constant threshold voltage. The IGZO TFTs based on HfO2 and SiNx gate dielectrics sputtered near room temperature were found to be good candidates for applications on organic flexible substrates.
Fabrication of Poly-Si TFTs on Flexible Quartz Fibers
Authors: Mimura Akio , Nakamura Toshihiro , Sugawara Yuta , Uraoka Yukiharu , Shuu Imei , Ikehara Tsuyoshi , Itoh Toshihiro , Maeda Ryutaro , Suzuki Kenkichi , Nakajima Akifumi , Koaizawa Hisashi
Published: October 2008

Flexible quartz fibers (cross-section: 1 mm x 0.1 mm) were developed as one-dimensional substrates for fiber-electronic devices such as OLEDs. Fine and uniform poly-Si films were deposited on moving fibers in an open-tube CVD system. Si films (thicknesses: 50 nm and 100 nm) were directly re-crystallized by green laser annealing without ablation. Top-gate type TFTs were fabricated and proper operation was confirmed with the electron field effect mobility of 177 cm2/Vs.
The Strain Effects on Flexible a-Si:H TFTs
Authors: Teng Li-feng , Liu Po-Tsun , Tsai Shang-Yao , Peng I-Hsuan , Chou Yi-Teh
Published: October 2008

The effects of the uniaxial mechanical strain stress on hydrogenated amorphous silicon (a-Si:H) thin film transistors (TFTs) were studied in this work. The proposed a-Si TFTs were fabricated on thin steel foil, and all process temperature was well-controlled below 200°. The threshold voltage (Vth) metastability was discussed by applying DC bias stress on gate electrode. The tensile strain was imposed on the device parallel to the source-drain current path, and all electrical parameters were extracted from saturation region. Our results indicated both outward and inward strain stress can lead to an un-recoverable destruction on a-Si:H TFTs at the first time. Even if the TFTs devices were re-flattened to plane, the transfer characteristic didn't recover and had larger Vth variation than the consequent bending performance. This phenomenon was related to the disorder of amorphous silicon structure. We provide a model and used activation energy to explain this effect.
Reliability of a-Si:H TFTs and Copper Interconnect Lines for Flexible Electronics
Authors: Kuo Yue , Coan Mary R. , Liu Guojun
Published: October 2008

Mechanical bending effects on two important components, i.e., amorphous silicon thin film transistors and copper interconnect lines, for the flexible electronics were studied. The deterioration of the thin film transistor's performance was dependent on the bending direction, i.e., more serious along the drain current flow direction than perpendicular to the drain current flow direction. The copper line's lifetime was drastically reduced, e.g., from 30 years without bending to 7.7 years with bending. The thin film transistor damage can be reduced with the proper layout design. Therefore, the interconnect line will be a critical factor affecting the product's reliability.
Sensors Based on Organic Thin Film Transistors
Authors: Yan Feng , Mok Sheung Man , Lin Peng , Chan Helen
Published: October 2008

Organic thin-film transistors (OTFT) are excellent candidates for the application on disposable sensors due to their potentially low-cost and easy fabrication process. Two types of OTFT-based sensors have been studied. One is light sensitive phototransistor based on the composite of poly(3-hexylthiophene) and TiO2 nanoparticles. The device shows a quick change of channel current under light exposure, which can be attributed to a positive shift of the threshold voltage induced by accumulated electrons trapped by the TiO2 nanoparticles in the channel. Another one is for sensing DNA hybridization. Both single and double strand DNA molecules are immobilized on the surface of the Au source/drain electrodes of different devices, inducing a dramatic change in the performance of the OTFTs. Single strand DNA and double strand DNA are differentiated successfully in the experiments indicating that this is a promising technique for sensing DNA hybridization without labeling.
An Image Sensor using Photoleakage Current and Feedthrough Voltage of Amorphous Si Thin-film Transistors
Authors: Hara Yujiro , Kinno Akira , Uchikoga S.
Published: October 2008

A flat panel image sensor with a simple structure, which contains only one a-Si:H TFT and a storage capacitor in each pixel, has been proposed. Instead of utilizing external voltage supply, a feedthrough voltage caused by parasitic capacitance of TFT was applied to extract the photogenerated charges in a-Si:H thin film. Decrease of feedthrough voltage owing to the photoleakage current during the transient time caused by gate pulse distortion was estimated to be less than 10%. A 3.8-inch prototype image sensor was fabricated, and sensor operation with 3-4bit still and motion image was successfully obtained. The possibility of high-aperture-ratio LCD with embedded image sensor has been shown.
Stable Pixel Circuit for Small-Area High-Resolution a-Si:H AMOLED Displays
Authors: Chaji G. Reza , Nathan A.
Published: October 2008

This paper reviews the challenges associated with development of stable and uniform active matrix organic light emitting diode (AMOLED) displays. The major issues considered are temporal and spatial non-uniformities, settling time and frame rate, aperture ratio, power consumption, and thermal run-away. We present a charge based driving scheme is introduced along with measurement results. This driving scheme can provide for over 20,000 hours of lifetime, and large aperture ratio.
Analog Circuits Design using Polycrystalline Silicon TFTs
Authors: Jacques Emmanuel , Le Bihan France , Crand Samuel , Brahim Tayeb Mohammed
Published: October 2008

In this paper, we present polycrystalline silicon thin film technology used to design analog devices. The goal of theses circuits is to develop low cost microsystems integrating sensors with their control and conditioning electronics. For this, differential amplifiers are designed, fabricated and characterized based on complementary Si-poly TFT. These amplifiers show high performances (maximum gain of 42 dB) and allow the detection of very low level signals (0.4 mV).
Applications of Thick Film Screen Printing and Ink Jet Printing for the Manufacturing of Single Use, Disposable Biosensors
Authors: Liu Chung-Chiun
Published: October 2008

Thick film screen printing and ink jet printing are mature, cost-effective manufacturing processes in micro-electronic industries. However, the applications of these processes to the production of chemical and biological sensors remain limited. The potential for using these technologies in producing cost-effective chemical and biological sensors, particularly for single use, disposable sensors has not been fully explored. Nano particle metallic catalysts have unique properties in many electrochemical reactions. Thus, the incorporation of nanoparticle catalysts into the thick film printing processing in the manufacturing of electrochemical based chemical and biological sensors can be attractive in the advance of the single use, disposable biosensor. Thus, the combined thick film printing and nano metallic catalysts approach is used to manufacturing of cost effective, single use, disposable biosensors. This platform technology will be based on the enzymatic reactions which will yield an electrochemically active product such as H2O2, NADH, and NAD+.
Inkjet Printing Glucose Oxidase for Biosensor Applications
Authors: Wang Tianming , Cook Chris , Derby Brian
Published: October 2008

Glucose oxidase (GOx) is used as an immobilized enzyme in blood glucose level sensors. Conventional sensors are fabricated by pipetting or biodotting enzyme suspensions onto carbon black electrodes. There is considerable interest in producing sensor structures of smaller dimensions than are readily achievable through these techniques. One technology that may be able to deliver enzyme-based sensors with smaller length scales is inkjet printing. Inkjet printing is capable of accurately placing picolitre volumes of liquids onto a substrate, making it an ideal technology that could be used within the medical sensor field. Here we present preliminary results showing the activity of GOx after printing and printing onto prototype device structures.
Development of a High-Sensitive Immunosensor Based on Monitoring Redox Signal of Gold Nanoparticle
Authors: Idegami Koutarou , Chikae Miyuki , Kerman Kagan , Takamura Yuzuru
Published: October 2008

A high-sensitive immunosensor was developed monitoring the redox signals of Au nanoparticles in connection with disposable screen-printed carbon strips (SPCSs). All the procedures could be performed on only one strip in a volume of 2 μL solution. Additionally, the direct observation of the Au nanoparticle-labeled antigen-antibody complex on the electrode surface was performed by SEM imaging.The changes in the structure of Au nanoparticles during the redox process could be monitored using the high-resolution SEM images. Our immunosensor system, a combination of the screen-printing technology, direct electrical detection of Au nanoparticles with redox enhancement, provides a promising biosensor for various applications in life sciences.
A Fiber-Optic Fluorometric Immunoassay for Determination of Dermatophagoides Farinae Allergen (Der f1)
Authors: Miyajima Kumiko , Koshida Tomoyuki , Saito Hirokazu , Kudo Hiroyuki , Yano Kazuyoshi , Mitsubayashi Kohji
Published: October 2008

Immunoassay methods are generally used for measuring of allergenic substances. However, they need special facilities, cumbersome manipulation and taking a lot of time to get results. In this work, rapid and easy immunoassay using optical fiber system was established, which detected fluorescence of an immune complex formed by allergen and fluorescently labeled antibody. The immune complex was bound at the optical fiber probe surface, and excitation light was transmitted into the probe. Then evanescent wave was generated and excited fluorescent molecules, finally, fluorescent light was detected by a photo diode. Dermatophagoides farinae allergen (Der f1) was measured and cyanine 5 (Cy5) was used as fluorescent molecule. The fiber-optic immunoassay could detect and quantify Der f1. The measurement range was from 1.95ng/ml to 250 ng/ml, and the result was the equivalent of ELISA. The measurement time was 15min/sample.
Artificial Siderophore-Modified Au electrode for Adsorption and Sensing Microbe
Authors: Tanabashi Hirohito , Inomata Tomohiko , Eguchi Hiroshi , Funahashi Yasuhiro , Ozawa Tomohiro , Masuda Hideki
Published: October 2008

Siderophores, which are secreted by microorganism for iron uptake, strongly bind Fe(III) ions and permeate the cell membrane through the receptor and/or binding protein. Our aim is the development devices based on the substrates modifying Fe(III)-artificial siderophore complexes for adsorbing and sensing microorganisms. The key point of our strategy is the interaction between the artificial siderophore complexes on the substrates and the siderophore receptor proteins at the cell membrane. We report the construction of the Au films modified by the artificial siderophore complexes and their adsorption ability for microbes.