Showing papers on "Thin-film transistor published in 1985"

Thin film field effect transistor and method of making same

Abstract: There is disclosed a film field effect transistor which can be operated at fast switching rates for use, for example, in video display applications. The transistor includes a body of silicon semiconductor material having a structure more ordered than amorphous material and less ordered than single crystalline material. The source and drain of the transistor comprise rectifying contacts formed on the body of silicon semiconductor material. Also disclosed are a method of making the transistor and an electronically addressable array system utilizing the transistor to advantage.

Method of fabricating a polysilicon transistor with a high carrier mobility

Abstract: A method for making a TFT comprises forming an amorphous silicon layer having a smooth upper surface. An insulating layer is then formed on the smooth surface at or below the critical temperature for the instantaneous crystallization of amorphous. This slowly converts the amorphous silicon to polycrystalline silicon while retaining the smooth surface. TFTs incorporating the invention have a relatively high field effect (surface) mobility.

Process for producing thin-film transistor

Abstract: A gate insulating film, a high-resistivity semiconductor film, a low-resistivity semiconductor film and if necessary a conducting film are successively deposited in lamination without exposing them to any oxidizing atmosphere including atmospheric air, and then the source and drain electrodes are selectively formed.

Depletion mode thin film semiconductor photodetectors

Abstract: A depletion mode thin film semiconductor photodetector comprises a crystalline silicon thin film on an insulating substrate with a source region, a drain region and a thin film light sensing channel region formed therebetween. A gate oxide formed over the channel region and a gate electrode formed on the gate oxide. A p-n junction located parallel to the surface of the substrate and within the thin film functioning as a space charge separation region in the channel. The lower portion of the channel region is a p region extending to the substrate and the upper portion of the channel region is a n region extending to the gate oxide. The channel region functions as a fully depleted channel when the photodetector is operated in its OFF state providing for high dynamic range and large photocurrent operation. The depletion mode thin film semiconductor photodetector with n+ source and drain regions function as an ohmic contacts to the channel n region forming a thin film transistor. The thin film transistor photodetector has high photoconductive gain at low light intensities when the n channel region is fully pinched off by an applied gate voltage to the gate electrode which is sufficiently negative as compared to the threshold voltage of the photodetector. When the drain region is replaced by a p+ region functioning as an ohmic contact to the channel p region, a depletion mode gated diode is formed. When the channel region is extended to include a plurality of linearly spaced gate electrodes formed on the gate oxide region with an input diode formed adjacent to the first of such gate electrodes and an output diode formed adjacent to the last of such gate electrodes, the photodetector functions as a charge coupled device.

Thin film transistor

Abstract: PURPOSE: To make it possible to obtain low-ON-resistance even if high OFF resistance is provided, by constituting a polycrystalline silicon thin film by two layers of a high resistance layer and a low resistance layer, and forming a channel in the low resistance layer. CONSTITUTION: A high resistance polycrystalline silicon layer 12 and a low resistance polycrystalline silicon layer 13 are laminated on an insulating substrate 11, and a polycrystalline silicon region is formed. The thickness of the high resistance layer is formed, e.g., within a range of 0.1∼1.0μm. The thickness of the low resistance layer 13 is formed, e.g., within a range of 0.01∼0.3μm. Since the substrate 11 is contacted with the high resistance layer 12, a parasitic channel is not formed even if electric charge is accumulated at an interface with the substrate. Therefore, a current is not increased at the OFF state. Thus, the device, whose ON resistance is low and OFF resistance is high, can be obtained. A device, in which P-type or N-type impurities are doped in the low resistance polycrystalline silicon layer 13 and the resistance is made further lower, can be used. Thus, the film thickness can be made thin, without decreasing the electric field mobility of the polycrystalline silicon layers, which form the channel region. COPYRIGHT: (C)1986,JPO&Japio

Color liquid crystal display with light intercepting member

Abstract: A color liquid crystal display panel is provided with a first substrate having thin film transistors arranged in rows and columns, a gate wire connecting commonly the gates for the thin film transistors in the columns, a source wire connecting commonly the sources for the thin film transistors in the rows and display electrodes connected respectively to each of the drains for the thin film transistors, a second substrate having a common electrode opposed to said display electrodes and acolor filter and a liquid crystal interposed between said first substrate and second substrate. The display panel comprises a light intercepting film provided on said second substrate at a position confronting with said thin film transistors.

N+ amorphous silicon thin film transistors for matrix addressed liquid crystal displays

Abstract: A thin film FET switching element, particularly useful in liquid crystal displays (LCDs) employs particular materials and is fabricated via a particular process to ensure chemical compatibility and the formation of good electrical contact to an amorphous silicon layer while also producing FETs with desirable electrical properties for LCDs. These materials include the use of titanium as a gate electrode material and the use of N + amorphous silicon as a material to enhance electrical contact between molybdenum source and drain pads and an underlying layer of amorphous silicon. The process of the present invention provides enhanced fabrication yield and device performance.

Field effect type thin film transistor

Abstract: PURPOSE:To increase the operating speed of the titled transistor by a method wherein a semiconductor layer is formed by the lamination of two layers of the first semiconductor film of 150Angstrom or less in thickness and the second semiconductor film of 1,000Angstrom or more in thickness having a larger band gap than the first film. CONSTITUTION:The gate electrode 6, gate insulation film 7, first semiconductor film 8 of 150Angstrom or less thickness made of microcrystallized Si or the like, source and drain 11 and 12, an amorphous Si film 13 the second semiconductor film of 1,000Angstrom thickness having a larger band gap than the film 8, and a protecting insulation film 14 are provided. When the thin film transistor of such a construction is turned on by impressing a positive voltage on its gate electrode, the electrons in the thickness direction of the layer 3 are quantized, and the electrons on the conduction band of this layer behave as the two dimensional electron gas; accordingly, a large density of free electrons can be obtained. Besides, the electrons flowing through the conduction band in an amorphous substance have a large mobility.

Forming an opaque metal layer in a liquid crystal display

Abstract: A liquid crystal display device is disclosed, which comprises first and second transparent substrates facing each other, a liquid crystal sealed between the transparent substrates, a plurality of display electrodes formed on the inner surface of the first transparent substrate, thin film transistors also formed on the first transparent substrate inner surface and each connected to each display electrode, and a transparent common electrode formed on the inner surface of the second transparent substrate, and in which the thin film transistors are selectively controlled to selectively drive the display electrodes for display. The resistance of semiconductor layers of the thin film transistors is reduced by external light to result in deterioration of the contrast of display. According to the invention, an opaque metal layer is formed between each thin film transistor and the first transparent substrate, and an insulating film is provided between the opaque metal layer and thin film transistor. Source buses of the same material as of and connected to the opaque metal layers are formed on the first transparent substrate.

Method of manufacture thin film transistor

Abstract: A method for manufacturing thin-film transistor comprises steps of sequentially forming in laminar state a gate film, an insulating film and a conductive film having a transparent electrode film and an amorphous silicon film added with an impurity thereto on the top surface of glass substrate or layer; irradiating ultraviolet ray from the bottom surface side of the substrate to expose negative photoresist film on said conductive film and to etch the same; and forming an amorphous semiconductive film on the structure. In this manner, source and drain electrodes are respectively self-aligned with the gate electrode and contacted therewith through a semiconductive film and a low resistive and semiconductor film.

Photosensor suited for image sensor

Abstract: A photosensor for realizing an image sensor which can meet the requirements of high resolution, high operation speed and high signal-to-noise ratio is disclosed. The photosensor comprises a circuit substrate, a thin film transistor formed on the circuit substrate and an amorphous silicon photodiode formed on the substrate integral with the thin transistor between the drain and gate electrodes thereof. Also formed on the circuit substrate adjacent to the thin film transistor and photodiode are a charging switch element for coupling the photodiode to a DC power source to charge an inter-electrode capacitance of the photodiode, a charge storage capacitor charged by a channel current of the thin film transistor controlled by an inter-electrode capacitance voltage of the photodiode which varies in response to incident light after the inter-electrode capacitance has been charged, and a detecting switch element for coupling the capacitor to an output amplifier. The charging and detecting switch elements are each formed of a thin film transistor.

Biasing liquid crystal displays having capacitors and transistors

Abstract: A display apparatus comprises a first substrate provided with a thin film transistor array as a driving switching element and a second substrate provided with another electrode, and produces a display by electro-optical change generated between these substrates. Visibility of the display is improved in such a way that rays of light incident on the display apparatus are converted into diffusion light. Photoconductive material, in particular amorphous silicon, can be used by covering semiconductive portions of the thin film transistor array of the display apparatus with an intercepting member. In a display apparatus using a thin film transistor array as a driving switching element, a conductive surface electrically insulated from gate lines on a substrate on where the gate lines for the thin film transistor array are formed, such conductive surface acts as a counter electrode of capacitors for storing charge. Therefore the counter electrode of capacitors is separately formed from gate lines, and writing driving voltage can be set without taking effects of voltage change of gate lines into consideration. Shading layers comprising a plurality of color filters also cover each of the thin film transistors.

High voltage thin film transistor

Abstract: A high voltage amorphous silicon thin film transistor (10) including a gate electrode (14) which controls the injection of charge carriers from a superimposed n + doped amorphous silicon source electrode (24) into an amorphous silicon charge carrier transport layer (18) spaced from the gate electrode by a dielectric layer (16) for causing current conduction through the transport layer to a laterally-offset drain electrode (26). The source electrode is in charge- injecting contact with the transport layer, and the drain electrode is in collecting contact with the transport layer.

Thin film transistor

Abstract: PURPOSE:To check an increase of parasitic capacitance, and moreover to check deterioration of the characteristic of a thin film transistor by a method wherein multilayer reflecting films containing respectively a film consisting of amorphous silicon of at least one layer or more are provided as high screening films. CONSTITUTION:A thin film transistor is furnished with a glass substrate 27, a gate 28, and a source and a drain 29, 30, and the amorphous silicon films and an SiNx film 31, an amorphous silicon film 32, an insulating multilayer reflecting film 33 constructed by superposing eight layers in the order of an amorphous silicon film, an SiNx film, an amorphous silicon film... from the glass surface, and an insulating multilayer reflecting film 34 constructed by laminating in the order of an amorphous silicon film, an SiNx film, an amorphous silicon film... from the surface toward the amorphous silicon film 32 are formed according to the glow discharge method. Because the multilayer reflecting films 33, 34 having high screening faculties are insulators, parasitic capacitance is not generated, and moreover because film thicknesses thereof are thin, the change of the characteristic of the amorphous silicon semiconductor film according to heat generated at formation time of the multilayer reflecting films is also hardly generated.

On the quality of contacts in a-Si:H staggered electrode thin-film transistors

Abstract: Amorphous silicon thin-film field-effect transistors have been made with a staggered electrode structure. In this structure we distinguish two separate contributions to the total contact resistance, namely, the Al/a-Si:H barrier itself and the bulk resistance of the underlying a-Si:H layer. Concerning the first contribution it was found that a P-implantation forming n+regions followed by post-metallization annealing (PMA) at a moderate temperature of 200°C is very efficient in reducing the resistance of the Al contacts to negligibly small values. The second contribution, i.e., the bulk resistance, implies a variable series resistance in field-effect (FE) measurements. Thin-film transistors (TFT's) with different gate lengths were used for the first time to determine this residual series resistance R res .

Complementary thin-film transistor

Abstract: PURPOSE:To simply obtain a complementary device having uniform characteristics which is individually excellent by a method wherein a channel is formed using an Si film containing no impurities, the Si thin film of source and drain is formed in P or N type, and a P-channel or N-channel thin film FET is provided CONSTITUTION:Si thin films 302 and 303 containing no impurities are provided on an insulated substrate 301 in an isolated manner, a gate insulating film 304 is coated thereon, and a gate electrode 305 is attached P-thin films 308 and 309 are formed by performing B-ion implantation using the resist 304 as a mask, and N type thin films 312 and 315 are formed by implanting As ions using a resist 305 as a mask Lastly, an insulating film 314 is coated, an aperture is provided, electrodes 315-318 are attached and the titled transistor is formed According to this constitution, as a channel consists of an Si thin film containing no impurities, OFF current is low, and P- and N-channel elements with a conductive type source and drain can be obtained in a simple manner Also, as the thin film is thinner than the maximum width of a depletion layer, Vth is reduced, ON current is increased, a high speed operation can be performed, the characteristics of both FETs are markedly improved, and the difference in characteristics can be reduced

Thin film transistor

Abstract: PURPOSE:To obtain a TFT occupying a small area by a method wherein the three layers of a seimconductor layer, a source electrode and a drain electrode are deposited vertically putting the semiconductor layer at the middle layer, gate insulating layers are provided on the sides in regard to the semiconductor layer thereof, and gate electrodes are formed moreover. CONSTITUTION:The three layers of a drain electrode 7, a semiconductor layer 8 and a source electrode 9 are deposited vertically on an insulating substrate 1 of glass, quartz, etc. putting the semiconductor layer 8 at the middle layer, gate insulating layer 10 are provided vertically on the sides of the semiconductor layer 8, and moreover gate electrodes 11 are formed. For example, the drain electrode 7 is formed on the insulating substrated 1, and transparent, insulator layers 12 of the same thickness with the drain electrode are formed in a shape exposing the electrode 7 thereof. The semiconductor layer 8 is formed on the drain electrode 7, and after pattering is performed, an oxide film layer is formed on the surface of the semiconductor layer 8 according to an oxygen plasma process, or after the surface is cleaned according to sputter etching, etc., an oxide film or a nitride film is adhered, and the gate insulating films 10 are formed. After then, after the gate electrodes 11 are formed by patterning, insulating layers 13 are formed, and the source electrode 9 is formed finally.

The photosensitivity of amorphous silicon thin film transistors

Abstract: Amorphous silicon thin film transistors show a marked photoresponse. We describe results of a complete theory of the photofield effect, which includes the steady state flux of electrons and holes perpendicular to the source-drain current path. We indicate the nature of recombination centres required to reduce the photosensitivity and still maintain a good field effect.

Process for forming isolated silicon regions and field-effect devices on a silicon substrate

Abstract: Improved processing for MOS and CMOS transistors formed in an epitaxial-like layer. Field oxide regions are formed followed by the deposition of a polycrystalline or amorphous silicon layer which contacts the substrate at "seed windows" formed between the field oxide regions. The silicon layer is recrystallized from the substrate through the seed windows. The transistors are fabricated within the recrystallized silicon layer.

Thin film transistor

Abstract: PURPOSE:To avoid the deterioration of light shielding characteristics and simplify the process by forming a light shielding film with an amorphous carbon thin film CONSTITUTION:After an activation layer 74, a source electrode 76, a drain electrode 77 and a passivation layer 79 are formed, a light shielding layer 12 is formed out of an amorphous carbon film In this case, the passivation layer 79 and the light shielding layer 12 can be made to grow in one process only by changing material gas in the same plasma CVD apparatus For instance, when the passivation layer 79 is made of a-SiOx, the light shielding layer 12 can be formed on the passivation layer 79 continuously in one process by changing the material gas from SiHx+N2O to C2H2+H2 After these layers are formed, the unnecessary parts of those layers above a display electrode 81 are removed by plasma etching With this constitution, processes such as deposition of a metal layer for the light shielding layer, photolithography and reformation of the passivation layer are unnecessitated and the process can be quite simplified

High stability, plasma deposited, amorphous silicon nitride for thin film transistors

Abstract: Silicon nitride films deposited by plasma enhanced chemical vapour deposition have been made using ammonia rich mixtures of SiH4 and NH3. The electronic properties, in particular flatband voltage stability under charge injection, of this material have been measured using MIS structures fabricated on single crystal n+ silicon. The grown films are found to be nitrogen rich with a high proportion of NH groupings. Using a low deposition rate A /sec it is possible to produce a ‘short free’ stable free' stable insulator for TFTs that is only 1200 A.

Liquid crystal image display device

Abstract: PURPOSE:To form an image having a high contrast ratio without spoiling its brightness by forming microlenses in a matrix on a substrate facing a substrate where active switching elements are formed in a matrix. CONSTITUTION:Polysilicon thin-film transistors TFT are formed as switching elements on a transparent quartz substrate 5 in a matrix. Then, a color filter layer 2 is formed on the opposite substrate 1 by a photoengraving, a printing, and a pigment vapor-depositing method, etc. Transparent methacrylate negative resist is applied over the layer 2 by spin coating and photoengraving is carried out for exposure and development to overetch the negative resist, forming microlenses 3 in a matrix. Further, a transparent common electrode 4 is formed on the lenses 3. Then, liquid crystal cells are incorporated between the couple of substrates by using spacers and gap agents and liquid crystal is charged to form a liquid crystal image display device.

Contact type image sensor

Abstract: PURPOSE:To obtain a contact type image sensor having high performance by directly forming an amorphous silicon photodiode onto a high-concentration impurity addition region in a source (or a drain) for a polycrystalline silicon TFT for a switch circuit. CONSTITUTION:The side 15 of a drain electrode 14 is used for the ohmic contact of a metallic electrode 2, and the source side 16 is employed as one part of a photodiode. Impurities are added previously to an N shape on an N channel TFT and to a P type on a P channel TFT. Amorphous silicon layers 17, 18 are isolated and shaped so as to be protruded from polycrystalline silicon. A transparent electrode 19 consisting of ITO and SnO2 is extended up to a substrate as a wiring, and covers the side wall of the amorphous silicon photodiode, but an N layer and a P layer are not short-circuited by the transparent electrode, thus eliminating the need for the deposition of an insulator and the information of a window for a contactor.

High voltage thin film transistor on PLZT and method of manufacture thereof

Abstract: A high voltage thin film transistor structure and method are disclosed which make it possible to fabricate matrix displays with integrated pixel switches on PLZT substrates. A polysilicon transistor capable of withstanding more than 60 V across the source and drain and with a ratio of on to off current in excess of 10 3 is disclosed. The fabrication method disclosed is suitable for use with brittle and readily oxidizable PLZT substrates.

Infrared detecting element

Abstract: PURPOSE:To provide an IR detecting element having a small size and high sensitivity and to easily manufacture said element by forming an IR sensor and thin film transistor on the same substrate and using a pyroelectric material film as a gate oxide of the thin film transistor. CONSTITUTION:A lower electrode 2 consisting of Pt is formed by a sputtering method on the substrate 1 consisting of an MgO single crystal obtained to a specular surface and the thin pyroelectric material film 3 is formed thereon. The upper electrode 4 consisting of NiCr is deposited by evaporation thereon. A thin CdSe film doped with In or the like to be made into an n-type is then deposited by evaporation as a semiconductor layer 6 thereon. A source electrode 5 and a drain electrode 7 are finally deposited by evaporation on said layer to form the IR detecting element. An aperture 8 is provided to the substrate 1 in the part corresponding to the electrode 4, i.e., the part operating as the pyroelectric type IR detecting part.

Composite semiconductor device

Abstract: PURPOSE: To obtain stable operation with a power MOSFET which has a built-in excessive current limiting circuit by taking a structure which prevents the occurrence of parasitic effect. CONSTITUTION: A power MOSFET Q1 and a current detector transistor Q2 are formed on the same semiconductor substrate with drain and gate terminals shared, and a control circuit to limit a current consists of a thin film resistors R1 and R2 and a thin film transistor Q3 electrically insulated from a semiconductor substrate 1. Since the control circuit to limit an excessive current is electrically isolated from the MOSFET which is a main body element, there is no electrical interference between the MOSFET which handles main current and the control circuit, as a result, excessive current can be limited very stably. COPYRIGHT: (C)1993,JPO&Japio

Full color liquid crystal television addressed by amorphous silicon TFTs

Abstract: A five inch color LCD panel addressed by amorphous silicon thin film transistors (TFTs) has been developed for TV receivers. To increase productivity of the panel, optimum design parameters of the display such as number of pixels, TFT structure, etc were studied.

Manufcture of thin film transistor

Abstract: PURPOSE:To obtain a TFT characterized by small fluctuation width of a thresh old voltage and excellent reliability, by performing plasma treatment of a sillicon nitride film constituting a gate insulating film by using mixed gas of nitrogen and hydrogen and the like, and laminating semiconductor layers. CONSTITUTION:On a conductor film 12, which functions as a gate electrode, a silicon nitride film 13 comprising silicon and nitrogen as main component is formed as a gate insulating film. A silicon thin film 14, whose main component is silicon, is laminated as a semiconductor layer, and a thin film transistor is manufactured. At this time, plasma treatment of said silicon nitride film is performed by using any one kind of mixed gas among a mixed gas comprising hydrogen gas and nitrogen gas, a mixed gas comprising hydrogen gas, inactive gas and ammonia and a mixed gas comprising inactive gas and ammonia. By the plasma treatment, the quality of the surface of the silicon nitride film becomes excellent as an insulator. The fluctuation in threshold voltage with respect to the applied voltage of on the TFT can be suppressed. Therefore, the stable TFT is obtained.

Process for fabricating electronic circuits based on thin-film transistors and capacitors

Abstract: Process of fabricating an active matrix display screen in which there are left after the second photo-etching segments (S) forming conductive bridges (120, 110, 112, 114) over breaks (103) in the conductive layer (102) forming the columns.

Thin film transistor and manufacture thereof

Abstract: PURPOSE:To enable to easily make shorter the channel length of a thin film transistor without needing a microscopic working technique by a method wherein the channel length is decided by only the thickness of a semiconductor thin film CONSTITUTION:A gate electrode 5 and a gate insulating film 4 are formed on an insulating substrate 10 A first main electrode region 1 including a first conductive film, which is used as a source or a drain, is insularly formed One end part of the first main electrode region 1 is provided on one end part of the gate electrode 4 or on the gate electrode 4 An a-Si film 3 and a second conductive film 2 are continuously deposited, a patterning is performed on the films 3 and 2 in the same form and a channel region and a second main electrode region are formed The a-Si film 3 and the second conductive film 2 are partially superposed with the first main electrode region 1 and are extendedly provided on both of one side surface of the first main electrode region 1 and the surface of the gate insulating film 4 (gate electrode 5) The thickness of the a-Si film 3 is selected thinner than the insular height of the first main electrode region 1 This thickness selected in such a way simultaneously results in deciding the channel length of this thin film transistor At need, an insulating film 6 is deposited on the whole surface and after a contact hole was opened on each region, this transistor is completed by performing a source wiring 21, a drain wiring 22 and a gate wiring