Showing papers on "Thin-film transistor published in 1997"

Stacked pentacene layer organic thin-film transistors with improved characteristics

Abstract: Using two layers of pentacene deposited at different substrate temperatures as the active material, we have fabricated photolithographically defined organic thin-film transistors (OTFTs) with improved field-effect mobility and subthreshold slope. These devices use photolithographically defined gold source and drain electrodes and octadecyltrichlorosilane-treated silicon dioxide gate dielectric. The devices have field-effect mobility as large as 1.5 cm/sup 2//V-s, on/off current ratio larger than 10/sup 8/, near zero threshold voltage, and subthreshold slope less than 1.6 V per decade. To our knowledge, this is the largest field-effect mobility and smallest subthreshold slope yet reported for any organic transistor, and the first time both of these important characteristics have been obtained for a single device.

Pentacene organic thin-film transistors-molecular ordering and mobility

Abstract: Pentacene-based organic thin-film transistors (TFT's) with field-effect mobility as large as 0.7 cm/sup 2//V/spl middot/s and on/off current ratio larger than 10/sup 8/ have been fabricated. Pentacene films deposited by evaporation at elevated temperature at low-to-moderate deposition rates have a high degree of molecular ordering with micrometer-sized and larger dendritic grains. Such films yield TFT's with large mobility. Films deposited at low temperature or by flash evaporation have small grains and poor molecular ordering and yield TFT's with low mobility.

Pentacene-based organic thin-film transistors

Abstract: Organic thin-film transistors using the fused-ring polycyclic aromatic hydrocarbon pentacene as the active electronic material have shown mobility as large as 0.7 cm/sup 2//V-s and on/off current ratio larger than 10/sup 8/; both values are comparable to hydrogenated amorphous silicon devices. On the other hand, these and most other organic TFT's have an undesirably large subthreshold slope. We show here that the large subthreshold slope typically observed is not an intrinsic property of the organic semiconducting material and that devices with subthreshold slope similar to amorphous silicon devices are possible.

Organic molecular solids as thin film transistor semiconductors

Abstract: The use of discrete organic compounds as active materials in transistors is described, beginning with α-sexithiophene (α-6T) and progressing to other thiophene oligomers and nonthiophene semiconductors. Device operation, molecular design, synthesis, film morphology and transport of holes and electrons are covered.

Integration of organic LEDs and amorphous Si TFTs onto flexible and lightweight metal foil substrates

Abstract: We report the integration of organic light emitting devices (OLEDs) and amorphous Si (a-Si) thin-film transistors (TFTs) on both glass, and unbreakable and lightweight thin stainless steel foil substrates. The doped-polymer OLEDs were built following fabrication of driver TFTs in a stacked structure. Due to the opacity of the steel substrate, top-emitting OLED structures were developed. It is shown that the a-Si TFTs provide adequate current levels to drive the OLEDs at video brightness (/spl sim/100 cd/m/sup 2/). This work demonstrates that lightweight and rugged TFT backplanes with integrated OLEDs are essential elements for robust and highly portable active-matrix emissive flat-panel displays.

Single-crystal Si films for thin-film transistor devices

Abstract: The fact that single-crystal Si would make an ideal material for thin-film transistor devices has long been recognized. Despite this awareness, a viable method by which such a material could be directly produced on a glass substrate has never been formulated. In this letter, it is shown experimentally that location-controlled single-crystal Si regions on a SiO2 surface can be obtained in a glass-substrate compatible manner, via excimer-laser-based sequential lateral solidification of thin Si films using a beamlet shape that self-selects and extends a single grain over an arbitrarily large area. This is accomplished by controlling the locations, shape, and extent of melting induced by the incident excimer-laser pulses, in such a manner as to induce interface-contour-affected sequential super-lateral growth of crystals, during which the tendency of grain boundaries to align approximately orthogonal to the solidifying interface is systematically exploited.

Semiconductor device method for producing the same and liquid crystal display including the same

Abstract: A liquid crystal display device including: a display section including a liquid crystal layer; a pair of substrates interposing the liquid crystal layer; a plurality of pixel electrodes located in a matrix on one of the pair of substrates; a plurality of first thin film transistors respectively connected to the plurality of pixel electrodes; and a peripheral driving circuit located for driving the display section, the peripheral driving circuit being located on the substrate on which the first thin film transistors are located and having a second thin film transistor. Each of the first thin film transistors includes a first channel layer formed of a first crystalline silicon layer, and the second thin film transistor includes a second channel layer formed of a second crystalline silicon layer having a higher mobility than the mobility of the first crystalline silicon layer. The second crystalline silicon layer includes a catalytic element for promoting crystallization.

Novel fingerprint scanning arrays using polysilicon TFT's on glass and polymer substrates

Abstract: Novel fingerprint scanning arrays based upon capacitance sensing have been made Each sensor element consists of a capacitor electrode and two poly-Si thin film transistors for addressing and read out The devices were fabricated on glass, polyimide and polyethersulphone substrates using a low temperature (<250/spl deg/C) process

Excimer laser crystallization and doping of silicon films on plastic substrates

Abstract: We report the pulsed laser recrystallization and doping of thin film amorphous silicon deposited on oxide-coated polyester substrates. Although our heat-flow simulation of the laser recrystallization process indicates that the plastic is briefly subjected to temperatures above its softening point, we see no evidence of damage to the plastic or film delamination from the substrate. Film grain size is found to vary up to ∼0.1 μm. Electrical characteristics obtained from simple strip line resistors and thin film transistors indicate that device-quality silicon films have been produced on an inexpensive flexible plastic substrate.

Semiconductor device including active matrix circuit

Abstract: There is provided a combination of doping process and use of side walls which allows the source and drain of a thin film transistor of an active matrix circuit to be doped with only one of N-type and P-type impurities and which allows the source and drain of a thin film transistor used in a peripheral circuit of the same conductivity type as that of the thin film transistor of the active matrix circuit to include both of N-type and P-type impurities. Also, a thin film transistor in an active matrix circuit has offset regions by using side walls, and another thin film transistor in a peripheral circuit has a lightly doped region by using side walls.

SPICE Models for Amorphous Silicon and Polysilicon Thin Film Transistors

Abstract: We describe physically based analytical models for n‐channel amorphous silicon thin film transistors and for n‐ and p‐channel polysilicon thin film transistors. The models cover all regimes of transistor operation: leakage, subthreshold, above‐threshold conduction, and the kink regime in polysilicon thin film transistors. The models contain a minimum number of parameters which are easily extracted and can be readily related to the structural and material properties of the thin film transistors. The models have been verified for a large number of devices to scale properly with device geometry.

Formation of display transistor array panel

Abstract: PROBLEM TO BE SOLVED: To sharply reduce a manufacturing cost. SOLUTION: Plural TFT elements 43 are formed on a 1st substrate consisting of a Si substrate at pitches dx/m, dy/n with respective element separation grooves 44 intervened. The dx and dy are array pitches of pixels and each of (m) and (n) is a natural number of >=2. A 2nd substrate 45 is stuck to the 1st substrate with UV peeling resin 46, and after removing the 1st substrate by etching, respective TFT elements 43 are separated. Only TFT elements 43 to be transferred are selectively stuck with adhesive resin 51, and selectively irradiated with ultraviolet rays 62 from the side of the 2nd substrate 45 to selectively be transferred to a 3rd substrate 47. Thus, the same selected TFT element 43 can be transferred to (m×n) pieces of panel substrates 47 while forming (m×n) times as many as a necessary number of TFT elements 43 on one piece of 2nd substrate 45, so that cost required for forming TFT elements 43 on the 1st substrate can be reduced approximately to become 1/(m×n).

Floating body effects in polysilicon thin-film transistors

Abstract: Floating body effects in polycrystalline silicon thin film transistors (poly-TFTs) are investigated by means of numerical simulations. The current increase in the output characteristics at large V/sub DS/, usually referred to as the "kink effect" is explained by impact ionization occurring in the high-field region at the drain end of the channel. Its effect is enhanced by the action of a parasitic bipolar transistor in the back-channel region, whose base current arises from the impact generated holes. The dependence of the kink on the recombination kinetics is also investigated.

Thin-film field-effect transistor with organic semiconductor requiring low operating voltages

Abstract: A thin film transistor (TFT) device structure based on an organic semiconductor material, that exhibits a high field effect mobility, high current modulation and a low sub-threshold slope at lower operating voltages than the current state of the art organic TFT devices. The structure comprises a suitable substrate disposed with he following sequence of features: a set of conducting gate electrodes covered with a high dielectric constant insulator, a layer of the organic semiconductor, sets of electrically conducting source and drain electrodes corresponding to each of the gate lines, and an optional passivation layer that can overcoat and protect the device structure. Use of high dielectric constant gate insulators exploits the unexpected gate voltage dependence of the organic semiconductor to achieve high field effect mobility levels at very low operating voltages. Judicious combinations of the choice of this insulator material and the means to integrate it into the TFT structure are taught that would enable easy fabrication on glass or plastic substrates and the use of such devices in flat panel display applications.

Oligophenyl-based organic thin film transistors

Abstract: Organic thin film transistors (TFTs) have been fabricated using thermally evaporated films of the oligophenyls p-quaterphenyl (p-4P), p-quinquephenyl (p-5P), and p-sexiphenyl (p-6P). The field-effect mobility of these TFTs ranges from 10−2 cm2/V s for p-4P to 10−1 cm2/V s for p-6P with on/off current ratio from 105 to 106. These values are comparable to those achieved using the more widely studied organic semiconductors alpha-sexithienyl (α-6T) and pentacene. X-ray diffraction reveals a high degree of molecular ordering, believed to be important for obtaining high field-effect mobility in organic TFTs.

Fabrication of thin film effect transistor comprising an organic semiconductor and chemical solution deposited metal oxide gate dielectric

Abstract: A thin film transistor (TFT) device structure based on an organic semiconductor material, that exhibits a high field effect mobility, high current modulation and a low sub-threshold slope at lower operating voltages than the current state of the art organic TFT devices. A fabrication process for the same, especially a process for deposition of the gate insulator using chemical solutions. The structure comprises a suitable substrate disposed with the following sequence of features: a set of conducting gate electrodes covered with a high dielectric constant insulator, a layer of the organic semiconductor, sets of electrically conducting source and drain electrodes corresponding to each of the gate lines, and an optional passivation layer that can overcoat and protect the device structure. Use of high dielectric constant gate insulators exploits the unexpected gate voltage dependence of the organic semiconductor to achieve high field effect mobility levels at very low operating voltages. Judicious combinations of the choice of this insulator material and the means to integrate it into the TFT structure are taught that would enable easy fabrication on glass or plastic substrates and the use of such devices in flat panel display applications.

Thin film device provided with coating film, liquid crystal panel and electronic device, and method for making the thin film device

Abstract: Any one of an insulating film forming a TFT, a silicon film and a conductive film is formed by applying a solution and annealing it. In a spin coater (102), a coating solution containing a thin film component which is supplied from a solution storage section (105) is spin-coated onto a substrate. The substrate after coating the coating solution is annealed in an annealing section (103) to form a coating film on the substrate. Additional laser annealing improves one of film characteristics, i.e., crystallinity, density and adhesiveness. Application of the coating solution or a resist by an ink jet process increases utilization of the solution and permits forming a patterned coating film. Because a thin film device in accordance with the present invention is inexpensive and has a high throughput, TFT production by a production system having high utilization of the coating solution drastically reduces initial investment and production cost of a liquid crystal display device.

Organic thin film transistor with enhanced carrier mobility

Abstract: An organic thin film transistor including a gate (21, 31, 41, 51, 61, 71) on a layer of gate insulator material (22, 32, 42, 52, 62, 72), a source (25, 35, 45, 55, 65, 75) and a drain (26, 36, 46, 56, 66, 76) positioned in spaced apart relationship on a film (24, 34, 44, 54, 64, 74) of organic semiconductor material with uniaxially aligned molecules, the film (24, 34, 44, 54, 64, 74) of organic semiconductor material being positioned so that the molecules are aligned between the source (25, 35, 45, 55, 65, 75) and drain (26, 36, 46, 56, 66, 76) in a direction from the source (25, 35, 45, 55, 65, 75) to the drain (26, 36, 46, 56, 66, 76), and an orientation film (23, 32, 43, 52, 63, 73) positioned adjacent the film (24, 34, 44, 54, 64, 74) of organic semiconductor material so that molecular uniaxial alignment of the film (24, 34, 44, 54, 64, 74) of organic semiconductor material is achieved by the orientation film (23, 32, 43, 52, 63, 73).

Patterned organic layers in a full-color organic electroluminescent display array on a thin film transistor array substrate

Abstract: A method of forming high definition patterned organic layers in a full-color electroluminescent (EL) display array on a two-dimensional thin film transistor (TFT) array substrate is described. The substrate has subpixels with each subpixel having raised surface portions and one recessed surface portion which reveals a bottom electrode. Red, green, and blue color forming organic EL layers are formed in the designated subpixels in accordance with a selected color pattern. The method uses a donor support which is coated with a transferable coating of an organic EL material. The donor support is heated to cause the transfer of the organic EL material onto the designated recessed surface portions of the substrate forming the colored EL medium in the designated subpixels. Optical masks and, alternatively, an aperture mask are used to selectively vapor deposit respective red, green, and blue organic EL media into the designated color EL subpixels.

Liquid crystal display with planarizing organic gate insulator and organic planarization layer and method for manufacturing

Abstract: A thin film transistor substrate for a liquid crystal display includes a substrate; a thin film transistor over the substrate, the thin film transistor having a gate, a source, a drain, a semiconductor layer, and a gate insulation layer; and a protection film over the thin film transistor, the protection film including at least one of fluorinated polyimide, Teflon, cytop, fluoropolyarylether, Fluorinated parylene, PFCB, and BCB.

Bis(dithienothiophene) organic field-effect transistors with a high ON/OFF ratio

Abstract: A conjugated, fused-thiophene oligomer, bis(dithienothiophene) (BDT), has been synthesized and deposited by vacuum sublimation as the active layer in organic thin film transistors (TFTs). The TFTs show exceptionally high ON/OFF ratios up to 108 between accumulation and depletion with sharp turn-on characteristics comparable to that of amorphous silicon TFTs (subthreshold slope S=0.6 V/decade). Field-effect mobilities are 0.02–0.05 cm2/V s. The good performance is explained by the relatively high π-π* gap of the short-chain BDT molecule and the favorable coplanar π-π stacking in BDT, differing from the herringbone stacking in the oligothiophenes.

Electroluminescent element and device and their production

Abstract: PROBLEM TO BE SOLVED: To realize the continuous light emission for long time by disposing oppositely a thin film transistor substrate and an electroluminescent substrate and connecting electrode pads and electrodes of one side of one pair of electrodes through adhesive electric connecting bodies. SOLUTION: Relating to an electroluminescent body (EL) element a thin film transistor(TFT) substrate 3 and an EL substrate 6 are faced each other and the EL electrode pad 62 of the EL substrate 6 side and the drain electrode pad 22 of the TFT substrate side are oppositely disposed and electrical connection between both electrodes is performed with an adhesive electric connecting body 71. This adhesive electric connecting body 71 is obtained by using conductive adhesive in which conductive particles such as carbon particles, silver particles, cupper particles and so forth are dispersedly incorporated in epoxy or phenolic thermal hardening adhesive and by coating it on the EL substrate 6 or the TFT substrate or on prescribed positions of both substrates and by drying it. Moreover, adhesive electric insulator 72 is provided at the outside part of the adhesive electric connecting body 71.

Process for fabricating semiconductor and process for fabricating semiconductor device

Abstract: A process for fabricating a semiconductor at a lower crystallization temperature and yet at a shorter period of time, which comprises forming an insulator coating on a substrate; exposing said insulator coating to a plasma; forming an amorphous silicon film on said insulator coating after its exposure to said plasma; and heat treating said silicon film in the temperature range of from 400 to 650° C. or at a temperature not higher than the glass transition temperature of the substrate. The nucleation sites are controlled by selectively exposing the amorphous silicon film to a plasma or by selectively applying a substance containing elements having a catalytic effect thereto. A process for fabricating a thin film transistor using the same is also disclosed.

Method and apparatus for driving an active matrix display panel

Abstract: An array substrate 12 is formed with pixel electrodes 14 in the form of a matrix. The pixel electrode 14 is connected to a thin film transistor 155. The thin film transistor 155 is formed with a light shielding film 152 consisting of resin for preventing an entry of light into the thin film transistor 155. A polymer dispersion liquid crystal layer 21 is interposed between a counter electrode 25 and the pixel electrode 14. A substrate 11 is formed with a color filter 151 having red (R), green (G), and blue (B). The color filter 151 is formed from dielectric multilayer film or organic material. The counter electrode 25 is formed above the color filter 155, and the counter electrode 25 and the liquid crystal layer 21 are bonded together by an adhesive layer 371.

Thin film transistors fabricated on plastic substrates

Abstract: A thin film transistor is described incorporating a gate electrode, a gate insulating layer, a semiconducting channel layer deposited on top of the gate insulating layer, an insulating encapsulation layer positioned on the channel layer, a source electrode, a drain electrode and a contact layer beneath each of the source and drain electrodes and in contact with at least the channel layer, all of which are situated on a plastic substrate. By enabling the use of plastics having low glass transition temperatures as substrates, the thin film transistors may be used in large area electronics such as information displays and light sensitive arrays for imaging which are flexible, lighter in weight and more impact resistant than displays fabricated on traditional glass substrates. The thin film transistors are useful in active matrix liquid crystal displays where the plastic substrates are transparent in the visible spectrum. Enablement of the use of such plastics is by way of the use of polymeric encapsulation films to coat the surfaces of the plastic substrates prior to subsequent processing and the use of novel low temperature processes for the deposition of thin film transistor structures.

Electro-optical device incorporating a peripheral dual gate electrode TFT driver circuit

Abstract: A thin file transistor (TPT) has first (lower) and second (upper) gate electrodes which are provide respectively above and under a semiconductor active layer and first and second insulating films (which serve as gate insulating films) provided respectively between the first gate electrode and a semiconductor layer and between a second gate electrode and the semiconductor layer. The second gate electrode has an anodic oxide film made of a material constituting the gate electrode on the upper and side surfaces thereof formed by anodization. Also, a silicide region is provided by covering the source/drain regions of the TFT with a silicide and changing a part of the region into a silicide.

TFT-array and manufacturing method therefor

Abstract: A TFT-array including a substrate, a gate electrode, a first and second electrode provided on the substrate simultaneously with the gate electrode, an insulating film formed on the gate electrode, the first and the second electrode, a semiconductor layer formed on the gate electrode in such a manner that the insulating film is interposed between the semiconductor layer and the gate electrode, a pair of electrodes, either of which is connected with the first electrode or the second electrode, said pair of electrodes defining a semiconductor element together with the semiconductor layer.

Depletion-type thin-film transistors with a ferroelectric insulator

Abstract: We present a study of electrical characteristics of ferroelectric field-effect transistors made of PbZr0.2Ti0.8O3 and SnO2:Sb thin films. Due to properly chosen semiconductor parameters, the transistor channel can be totally depleted by the ferroelectric charge displacement. The observed remnant on/off ratio of the channel current amounts to 7×103. Pulse response measurements give information on data retention, device speed, and the occurrence of charge injection. The results lead to important design considerations for ferroelectric transistors.

Liquid crystal displays using organic insulating material for a passivation layer and/or a gate insulating layer and manufacturing methods thereof

Abstract: A passivation layer is formed by coating a flowable insulating material on the substrate where a thin film transistor and a storage capacitor electrode, and a pixel electrode is formed on the passivation layer. A portion of the passivation layer is etched using the pixel electrode as a mask to make a groove on the thin film transistor, and then a black matrix is formed by filling an organic black photoresist in the groove. To increase the storage capacitance, a portion of the passivation layer is removed or to form a metal pattern on the storage capacitor electrode. A flowable insulating material is used as a gate insulating layer to planarize the substrate. In the case of the etch stopper type thin film transistor, a photo definable material is used as the etch stopper layer to reduce the parasitic capacitance between the gate electrode and the drain electrode.