SEMICONDUCTOR DEVICE AND MANUFACTURING METHOD THEREOF, DELAMINATION METHOD, AND TRANSFERRING METHOD
A substrate and a delamination film are separated by a physical means, or a mechanical means in a state where a metal film formed over a substrate, and a delamination layer comprising an oxide film including the metal and a film comprising silicon, which is formed over the metal film, are provided. Specifically, a TFT obtained by forming an oxide layer including the metal over a metal film; crystallizing the oxide layer by heat treatment; and performing delamination in a layer of the oxide layer or at both of the interface of the oxide layer is formed.
The present invention relates to a delamination method of a functional thin film, particularly to a delamination method of a film or a layer each of which is provided with various elements. In addition, the present invention relates to a transferring method for pasting a separated film to a film substrate, and further relates to a semiconductor device comprising a thin film transistor (hereinafter referred to as a TFT), which is formed in accordance with the transferring method, and to a manufacturing method thereof.2. Description of the Related Art
Recently, a technique for forming a TFT by using a semiconductor thin film (with a thickness of about several nanometers to several hundred nanometers) formed over a substrate provided with an insulating surface is attracting attention. A TFT is widely applied to an electronic device such as an IC or an electro-optic device, and is developed especially as a switching element or a driver circuit of a display device.
Such display devices can be mass-produced by performing dicing for obtaining multiple panels. Glass substrates and quartz substrates are mostly used; however, they have disadvantages of fragility and heaviness to be enlarged. Therefore, forming a TFT element on a flexible substrate typified by a flexible plastic film is being tested.
However, when a sophisticated polysilicon film is used for an active layer of a TFT; a process at a high temperature at several hundred degrees centigrade is necessary in a manufacturing process, so that the polysilicon film can not be formed directly on a plastic film.
Therefore, a method of separating a delamination layer from the substrate by using a separation layer in between is proposed. For example, a separation layer comprising such as amorphous silicon, a semiconductor, nitride ceramics, or an organic polymer is provided and exposed to a laser beam through the substrate; the substrate is separated by a delamination or the like in the separation layer (Reference 1: Japanese Patent Laid-open Publication No. 10-125929). In addition, a reference describes an example of completing a liquid crystal display device by pasting a delamination layer (referred to as a layer to be transferred) to a plastic film (Reference 2: Japanese Patent Laid-open Publication No. 10-125930). Techniques of respective companies are introduced in the articles on flexible displays (Reference 3: Nikkei Microdevices, Nikkei Business Publications, pp. 71-72, Jul. 1, 2002).
However, in the method described in the above publications, it is required to use a substrate which is highly transparent to light. Further, a rather high-energy laser beam is necessary for imparting sufficient energy to release hydrogen included in amorphous silicon through a substrate. That causes a problem of damage to a delamination layer. Further, the above publication describes a structure in which a light-resistant layer or a reflective layer is provided to prevent the damage to the delamination layer; however, in that case, it is difficult to fabricate a transmissive liquid crystal display device or a light emitting device which emits light downward. Still further, with the above method, it is difficult to separate a delamination layer having a large area.SUMMARY OF THE INVENTION
The present invention has been made in view of the above problems and it is an object of the present invention to provide a technique for performing separation between a substrate and a delamination layer by a physical means or a mechanical means in a state where a metal film formed over a substrate, and a delamination layer comprising an oxide film including the aforementioned metal and a film comprising silicon, which is formed over the metal film, are provided. Specifically, a TFT obtained by forming an oxide layer including the aforementioned metal over a metal film; crystallizing the aforementioned oxide layer by heat treatment; and performing delamination in a layer of the oxide layer or at the interfaces of both surfaces of the aforementioned oxide layer is formed.
A TFT formed according to the present invention can be applied to any light emitting device of top emission type or bottom emission type; or to any liquid crystal display device of transmissive type, reflective type, or semi-transmissive type; or the like.
Referring to the accompanying drawings, a description is made to explain embodiment modes according to the present invention.Embodiment Mode 1
First, a metal film 11 is formed on a first substrate 10 as shown in
Instead of a metal film, a metal film which is nitrided (metal nitride film) may be used. Nitrogen and oxygen may be added further to the metal film. For example, ion implantation of nitrogen or oxygen to metal film may be performed, or the metal film may be formed by sputtering in a film formation chamber which shall be a nitrogen or oxygen atmosphere. Furthermore, nitride metal may be used as a target.
Hereupon, when a metal alloy of the aforementioned metal (for example, an alloy of W and Mo:WXMo1-X) is used for the metal film, plural targets such as a first metal (W) and a second metal (Mo), or a target of an alloy of the first metal (W) and the second metal (Mo) is disposed in a film formation chamber, thereby forming the metal film by sputtering.
When the metal film is formed by sputtering, the film thickness of the periphery of the substrate occasionally becomes uneven. Therefore, it is preferable to remove a film of the periphery portion by dry etching; on that occasion, an insulating film such as a SiON film or a SiNO film may be formed into approximately 100 nm between the first substrate 10 and the metal film 11 so that the first substrate is not etched.
By setting the formation of metal film appropriately as above, the delamination process can be controlled, and a range of process is broadened. For example, when a metal alloy is used, use or diuse of heat treatment as well as the temperature of heat treatment can be controlled by controlling composition ratio in each metal of the alloy.
A delamination layer 12 is formed over the metal film 11. The delamination layer has an oxide film for forming an oxide layer including the aforementioned metal over the metal film 11, and a semiconductor film. The semiconductor film of the delamination layer may be in a state where a TFT, an organic TFT, a thin film diode, a photoelectric transducer comprising PIN junctions of Si, a silicon resistor, a sensor element (typically, a pressure-sensitive fingerprint scanner using polysilicon) or the like is formed in a desired manufacturing process.
Silicon oxide, silicon oxynitride or the like can be formed by a sputtering method or a CVD method as the oxide film. Incidentally, a thickness of the oxide film is preferably two times larger than that of the metal film 11. Here, by sputtering using a Si target, a silicon oxide film is formed with a film thickness of 150 nm to 200 nm.
In the present invention, when an oxide film is formed, the oxide layer including the aforementioned metal is formed over the metal film (not illustrated). The oxide layer may be formed into a film thickness of 0.1 nm to 1 μm, preferably 0.1 nm to 100 nm, further preferably 0.1 nm to 5 nm.
Another method for forming the oxide layer aside from the above can use a thin oxide film formed by processing an aqueous solution having sulfuric acid, hydrochloric acid or nitric acid; an aqueous solution in which sulfuric acid, hydrochloric acid or nitric acid and hydrogen peroxide water are mixed; or ozone aqua. As yet another alternative, oxidation may be performed by plasma treatment in an oxygen atmosphere or by generating ozone with ultraviolet irradiation in an oxygen containing atmosphere, or, a thin oxide film may be formed by heating approximately at 200° C. to 350° C. with a clean oven.
In the delamination layer 12, it is preferable that an insulating film comprising a nitride such as SiN, or SiON be provided as a base film particularly under a semiconductor film to prevent immersion of impurities or garbage penetrating the exterior of a metal film or a substrate.
Thereafter, heat treatment is performed at 380° C. to 410° C., 400° C., for example. By the heat treatment, the oxide layer is crystallized, and the hydrogen contained in the delamination layer 12, particularly, hydrogen of a semiconductor film is diffused. Heat treatment in a process for manufacturing a semiconductor device may be performed concurrently with heat treatment for the above step thereby reducing the number of the processes. When an amorphous semiconductor film is formed and a crystalline semiconductor film is formed by using a heating furnace or by laser irradiation, heat treatment at least at 500° C. may be performed for the crystallization, thus diffusing hydrogen as well as forming a crystalline semiconductor film.
A second substrate 13 which fixes the delamination layer 12 is pasted to the delamination layer 12 with a first adhesive material (binding material) 14 as shown in
Next, the first substrate 10 provided with the metal film 11 is separated by using physical means (
As shown in
Subsequently, the first binding material 14 is removed and the second substrate 13 is delaminated (
Plural delamination layers provided with TFTs that suit each usage may be transferred to the third substrate which is to be a transfer body. For example, a delamination layer of a TFT for a pixel area and a TFT for a driver circuit may be formed, and transferred to a predetermined area of the third substrate thereafter.
A TFT and the like which are formed on the film substrate obtained as above can be employed as a semiconductor element of a light emitting device or of a liquid crystal display device.
A light emitting device is formed by forming a light emitting element on the delamination layer 12 and forming a protective film which is to be an encapsulant thereafter. When a light emitting element is formed on the delamination layer 12, since the film substrate provided with a TFT is flexible, the delamination layer may be fixed to another glass substrate using a binding material such as a tape thereby forming each light emitting layer by vacuum deposition. Note that, it is preferable that a light emitting layer, an electrode and a protective film are sequentially formed without being exposed to the atmosphere.
The order for making a light emitting device is not limited particularly, and the following order may be adopted: a light emitting element is formed over a delamination layer; the second substrate is adhered; the delamination layer having light emitting element is separated, and it is pasted to the film substrate which serves as the third substrate. Further, after the formation of the light emitting element, the whole device may be wrapped in a film substrate designed larger, which serves as the third substrate.
When a liquid crystal display device is manufactured, a counter substrate is adhered with a sealing material after the separation of the second substrate, and a liquid crystal material may be injected in between. The order for making a liquid crystal display device is not limited particularly, and the following order may also be employed: the second substrate is adhered as a counter substrate; the third substrate is adhered; and a liquid crystal is injected in between, may be employed.
When a liquid crystal display device is manufactured, generally, spacers are formed or sprinkled to maintain a substrate gap; however, spacers with around 3 times the amount may be formed or sprinkled to maintain a gap between a flexible substrate and the counter substrate. Further, the spacers are preferably formed more softly than that are applied to a general glass substrate. Still further, it is necessary to fix the pacers so as not to move since a film substrate is flexible.
By applying such a delamination method, a TFT and the like can be formed on a flexible film substrate achieving delamination in the whole surface and high yield. In addition, a burden caused by a laser or the like are not placed on a TFT in the present invention. Thus, a light emitting device, a liquid crystal display device, or other display devices, which have the TFT and the like becomes thin, hard to be broken even if it drops, and lightweight. Further, display on a curved surface or in odd-shape becomes possible. A TFT provided on a film substrate, which is formed according the present invention can achieve the enlargement of display units as well as mass production. The present invention enables the recycling of the first substrate and achieves reducing costs of a display unit by employing a low-cost film substrate.EMBODIMENTS
A experimental result of the present invention, a light emitting device manufactured according to the present invention, a liquid crystal display device, and other electronic devices will be described below.Embodiment 1
In this embodiment, a result of a delamination experiment and an audit observation of a transmission electron microscope (TEM) will be described.
First, as to a sample shown in
Among the above samples, one to which heat treatment is not performed shall be A, another to which heat treatment at 220° C. for one hour is performed shall be B, and the other to which heat treatment at 500° C. for one hour and heat treatment at 550° C. for four hours thereafter are performed shall be C. Each of the samples is observed with a TEM. The results are shown in
It is found that a layer is formed at an interface between W film serving as a metal film 202 and a protective film 203. Note that, the layer is not always a complete layer, and is scattered in some cases.
An EDX measurement is performed to specify the composition of the layer. The spectrum and the quantitative result of the EDX measurement on samples A to C are shown in
In comparing TEM pictures in
Such results of the delamination experiment on samples A to C reveal that only sample C in which the oxide layer has a crystalline lattice can be separated.
As a result of the lamination experiments of the above samples D and E, only sample E is found to be separated.
The results of the above delamination experiment and TEM pictures reveal that an oxide layer is formed at the interface between a metal film and a protective film, and that the crystallization of the oxide film begins to occur approximately at 400° C. When the oxide layer has crystallinity, it is considered to be a state where separation may occur. Namely, it is found that an oxide film over a metal film, specifically, an oxide layer comprising W provided over a W film, needs to be formed.
Accordingly, since separation is possible in a sample wherein an oxide layer is crystallized, when the oxide film is crystallized by heat treatment, a crystal distortion, a lattice defect (point defect, line defect, plane defect (for example, plane defect due to crystallographic shear plane which is formed with congeries of oxygen vacancy), an expansion defect) generate, and separation is considered to occur form the interfaces thereof.Embodiment 2
Next, a delamination experiment is carried out under a different condition for manufacturing the protective film, or as the absence or presence of the protective film on a W film is varied.
As shown in
As illustrated in
The oxide layer is considered to be formed over the W film due to the oxygen gas employed when the sample 3 is formed. On the other hand, when the protective film is formed in sample 2, it is considered that only argon gas is used, so that an oxide layer is not formed on the W film. When the film thickness is considered, the oxide layer formed in sample 3 is thought to be different from the natural oxide film formed in sample 1. It is conceivable that the oxide layer is formed when the protective film begins to be formed.
Further as to sample 4, the SiO2 film is formed on a W film by CVD, by which an oxide layer may be formed; however, an oxide layer is not observed as shown in
Sample 3 and sample 4 in which oxide layers are formed are considered here. The silane gas employed by CVD, by which the SiO2 film of sample 4 is formed contains hydrogen compared with the source gas used in a manufacturing process of the SiO2 film in sample 3. Namely, an oxide layer is projected not to be formed in sample 4 due to the presence of hydrogen. Accordingly, a state in sample 4 can be thought to be varied due to the hydrogen although an oxide layer is formed on the W film.
As a result of the above, it is conceivable that an oxide layer which is different from a natural oxide film is formed when a protective film is formed on a metal film. Note that, it is regarded that the oxide layer is preferably about 3 nm thick when a W film is used. Further, it is preferable to form the protective film without containing hydrogen thereby forming the oxide film faultlessly.
In accordance with the above-mentioned result, it is considered necessary to form an oxide layer including the aforementioned metal (a metal oxide layer) on a metal layer for performing delamination. Particularly, when W is used for the metal film, it is found necessary to perform heat treatment at least at 400° C. thereby crystallize an oxide layer with a thickness of about 3 nm. Further according to the experimental result, it is found preferable to perform heat treatment at least at 430° C. since the crystallization of the oxide layer spreads all over.
Still further, it is found desirable that the aforementioned metal oxide layer on the metal layer is formed when the protective film is formed, and the protective film is formed in a state where hydrogen is not included or where the hydrogen concentration is low. When a W film is given as a concrete example, it is found preferable to form the protective film by sputtering using a source gas containing oxygen gas.Embodiment 3
In this embodiment, a result of the observation of an oxide layer on the side of a substrate and the side of an amorphous semiconductor film after the separation using TEM will be shown.
A W film with a thickness of 50 nm is formed over a glass substrate by sputtering; a silicon oxide film with a thickness of 200 nm is formed thereafter by sputtering; subsequently, an silicon oxynitride film with a thickness of 100 nm is formed as a base film by plasma CVD; and an amorphous film with a thickness of 50 nm is formed as a semiconductor film likewise by plasma CVD. Then, heat treatment is performed at 500° C. for 1 hour and at 550° C. for 4 hours; a quartz substrate is adhered by using epoxy resin as a bond; and separation is performed by a physical means. The TEM picture of the W film and the oxide layer on the substrate side at this point is shown in
The result of the examining the composition of the oxide layer by using XPS (X-ray photoelectron spectroscopy) is shown in this embodiment.
Chart 1 shows the area ratios of the respective states W1 to W4 of samples A to C obtained from
Sample C has a high composition ratio of W2 (WO2), and it is considered that the composition of the oxide layer is changed due to heat treatment. Accordingly, the composition of W4 (WO3) is changed to W2 (WO2) or W3 (WOx) and it is conceivable that separation occurs between different crystal structures due to such differences of the crystal structures.
Next, the side of the substrate after the separation and the side of the semiconductor film after the separation are measured with XPS. The measurements of the spectrum and the waveform analysis of the spectrum are shown in
Chart 2 shows the detected elements and a quantitative result obtained from
Subsequently, the waveform analysis of the spectrum on the side of the semiconductor film is shown in
The spectrum of sample 1 in which a natural oxide film is formed is shown in the XPS measurement in
The occupied bond ratio of the side of the semiconductor film after the separation are as follows: W1 and W2 are 0%, W3 is 16%, and W4 is 84%; meanwhile on the substrate side, W1 is 44%, W2 is 5%, W3 is 10%, and W4 is 46%. The occupied bond ratio of the natural oxide film in sample 1 is found to be as follows: W1 is 70; W2 is 6; W3 is 1; and W4 is 23.
In addition, the proportion of W1 (tungsten) is found to be higher in sample 1 compared with other samples. It is also found that the proportions of W2 to W4 (oxides) are low, and the proportion of W3 is considerably low.
The total amount of WO2 on the sides of the semiconductor film and the substrate after the separation is found to be lower compared with WO2 in sample C. Hence, it can be considered that the state of the oxide layer before separation is energetically active (unstable), and W4 (WO3) as well as the natural oxide film become the main constituent thereby stabilizing the state after the separation.
When sample C which can be separated and sample 1 in which the natural oxide film is formed are compared using
Accordingly, when the separation is performed at the interface between the oxide layer and the metal film, at the interface between an oxide layer and the silicon oxide film, or in a layer of the oxide layer, it is found that all of W1 (metal W) and W2 (WOX, X is nearly 2) remain on the substrate side; ⅔ of W4 (WO3 and the like) remains on the semiconductor film side; and ⅓ thereof remains on the side of the substrate. Further, the composition ratios of the oxide layer and the natural oxide film are found to be different from each other. Thus, it is considered that the separation can easily be performed in a layer of the oxide layer, especially, at the interfaces between WO2 and WOX or between WO2 and WO3. Therefore, WO2 does not remain on the side of the semiconductor film and WO2 adheres to the side of the substrate in the experiment; however, it can be possible that WO2 adheres to the side of the semiconductor film and no WO2 exists on the side of the substrate.Embodiment 5
In this embodiment, the result of secondary ion composition analysis method (SIMS) performed against samples A to C will be described using
When the profile of hydrogen in an amorphous silicon film is noted, the hydrogen concentration is approximately 1.0×10 (atoms/cm) in sample A and B, whereas the hydrogen concentration is approximately 1.0×1020 (atoms/cm3) in sample C, almost twice as large as sample A and B. When the profiles of hydrogen in silicon oxynitride film (SiON) and a silicon oxide film (SiO2) are observed, it shows the nonuniform concentration distribution, such as a tendency to decrease in the vicinity of a depth at 0.2 μm in sample A and B. On the other hand, sample C shows the uniform concentration distribution in the direction of depth without a tendency to decrease. Thus, more hydrogen exists in sample C than in samples A and B. According to the above result, it is considered that the ionization efficiency of hydrogen is different, and sample C has a composition ratio of surface different from samples A and B.
Next, when the nitrogen concentration at the interface between the silicon oxide film (SiO2) and W film is noted, the nitrogen concentration is approximately 1.0×1021 (atoms/cm) in sample A and B, whereas the nitrogen concentration is approximately 6.5×1021 (atoms/cm) in sample C, which is about 1 order of magnitude more than the concentration in sample A and B. Accordingly, Sample C has a different composition of the oxide layer at the interface between the silicon oxide film (SiO2) and the W film compared with samples A and B.Embodiment 6
In this embodiment, a light emitting device which is provided with a TFF manufactured over a film substrate according to a delamination method of the present invention with reference to
A signal line driver circuit 1201 provided with a CMOS circuit comprising an n-channel TFT 1223 and a p-channel TFT 1224, which is formed over the film substrate is shown. A TFT forming a signal line driver circuit or the scanning line driver circuit may be formed from a CMOS circuit, a PMOS circuit, or an NMOS circuit. Further in this embodiment, a built-in driver type wherein a signal line driver circuit and a scanning line drive circuit are formed over a substrate is shown; however, the circuits may be formed outside the substrate instead.
Further, an insulating film 1214 comprising 1212 a switching TFT 1221 and a current controlling TFT, and further comprising an opening in a predetermined position, which covers the TFT; a first electrode 1213 connected to one of wirings of the current controlling TFT 1212; an organic compound layer 1215 which is provided over a first electrode; a light emitting element 1218 comprising a second electrode 1216 which is provided opposite to the first electrode; and a pixel area 1220 comprising a protective layer 1217 which is provided to prevent deterioration of a light emitting element caused by water or oxygen, are shown.
Owing to the structure wherein the first electrode 1213 contacts a drain of the current controlling TFT 1212, it is desirable that at least the bottom of the first electrode 1213 shall be formed from a material that can form an ohmic contact with a drain region of the semiconductor film, or a material having a high work function in the surface comprising an organic compound. For example, when a three-layer structure of a titanium nitride film/a film comprising aluminum in major proportions/a titanium nitride film, is employed, the resistance as a wiring is low and the performance of making a good ohmic contact can be obtained. Further, the first electrode 1213 may be a single layer of a titanium nitride film, or a lamination having more than three layers. Furthermore, a light emitting device of a double side emission type can be manufactured by employing a transparent conductive film as the first electrode 1213.
The insulating film 1214 may be formed from an organic resin film or an insulating film comprising silicon. A positive photosensitive acrylic film is used here for the insulating film 1214.
It is preferable that the top edge and bottom edge of the insulating film 1214 is formed so as to have a curved surface with a curvature, thereby improving the coverage of a light emitting layer comprising an organic compound and the second electrode. For example, when a positive photosensitive acrylic film is employed for the insulating film 1214, it is preferable that the top edge of the insulating film 1214 solely has a curved surface with a curvature (0.2 μm to 3 μm). Further, whichever of a negative type that becomes insoluble in an etchant with light or a positive type that becomes soluble in an etchant with light can be used.
Further, the insulating film 1214 may be covered with a protective film. The protective film may be an aluminum nitride film obtained by a film formation system using sputtering (DC system or RF system) or remote plasma; an aluminum oxynitride film; an insulating film such as a silicon nitride film comprising silicon nitride or silicon oxynitride in major proportions; or a thin film comprising carbon in major proportions. It is desirable that the film thickness of the protective may be thin as possible so that light can transmit through the protective film.
A layer including an organic compound in which the luminescence of R, G, and B are obtained by applying an evaporation method with the use of a evaporation mask or ink-jetting is selectively formed over the first electrode 1213. Further the second electrode is formed over the layer including an organic compound 1215.
When the light emitting element 1218 shall emit white light, a color filter formed of a colored layer and a black mask needs to be formed.
The second electrode 1216 is connected to a connection wiring 1208 through an opening (a contact) provided over the insulating film 1214 in a connection area. The connection wiring 1208 is connected to a flexible printed circuit (FPC) 1209 by an anisotropic conductive resin (ACF). A video signal and a clock signal are received from an FPC 1209 which is to be an external input port. Only the FPC is illustrated here; however, a printed wiring board (PWB) may be attached to the FPC.
When the FPC is connected by applying pressure or heat with the use of an ACF, it is noted that a crack due to the flexibility of a substrate or softening caused by heat should be prevented from generating. For example, a substrate with high hardness may be disposed as an assistance on a part of the film substrate 1210, opposite to the part where the FPC is adhered.
The marginal portion of a substrate is provided with a scaling material 1205, and the substrate is pasted to a second film substrate 1204, and encapsulated. An epoxy resin is preferably used as the sealing material 1205.
In this embodiment, a substrate formed of FRP (Fiber-Reinforced Plastics), PVF (polyvinyl fluoride), mylar, polyester, acryl, or the like besides a glass substrate and a quartz substrate may be employed as a material for forming the second film substrate 1204.
Although it is not illustrated, the film substrate may be covered with a barrier film comprising an organic material such as polyvinyl alcohol or ethylene vinyl alcohol copolymer, an inorganic material such as polysilazane, aluminum oxide, silicon oxide, or silicon nitride; or a lamination of those, for preventing water or oxygen from penetrating through the film substrate.
A protective layer may be provided over the film substrate to protect from a medicine in a manufacturing process. An ultraviolet curable resin or a thermosetting resin can be used for the protective layer.
As described above, a light emitting device comprising a TFT provided over a film substrate is completed. The light emitting device comprising a TFT according to the present invention is hard to be broken even if it drops, and lightweight. A film substrate enables the enlargement of a light emitting device as well as mass production.Embodiment 7
A liquid crystal display device comprising a TFT formed over a film substrate by a delamination method according to the present invention will be described with reference to
A signal line driver circuit 1301 provided with a CMOS circuit comprising an n-channel TFT 1323 and a p-channel TFT 1324 is formed over the film substrate. A TFT forming a signal line driver circuit or a scanning line driver circuit may be formed from a CMOS circuit, a PMOS circuit, or a NMOS circuit. Further in this embodiment, a built-in driver type wherein a signal line driver circuit and a scanning line drive circuit are formed over a substrate is shown; however, the circuits may be formed outside the substrate.
Further, a pixel area provided with an interlayer insulating film 1314 comprising a switching TFT 1321 and a retention volume 1312, and further comprising an opening in a predetermined position, which covers the TFTs is shown.
An oriented film 1317 is provided over the interlayer insulating film 1314, and is treated with rubbing.
A second film substrate 1304 is prepared as a counter substrate. The second film substrate 1304 is provided with a color filter of RGB 1330, a counter electrode 1316, and an oriented film 1317 that is treated with rubbing, in an area partitioned into matrix form with resin or the like.
A polarizer 1331 is provided over the first and second film substrates, and is adhered with a sealing material 1305. And a liquid crystal material 1318 is injected between the first and second film substrates. It is not illustrated; however, a spacer is provided appropriately to maintain a gap between the first and the second film substrates.
Although it is not illustrated, the film substrate may be covered with a barrier film comprising an organic material such as polyvinyl alcohol or ethylene vinyl alcohol copolymer; or an inorganic material such as polysilazane, or silicon oxide; or a lamination of those, for preventing water or oxygen from penetrating through the film substrate.
A protective layer may be provided to protect from a medicine in a manufacturing process. An ultraviolet curable resin or a thermosetting resin can be used for the protective layer.
As described above, a liquid crystal display device comprising a TFT provided over a film substrate is completed. The liquid crystal display device comprising a TFT according to the present invention is hard to be broken even if it drops, and lightweight. A film substrate enables the enlargement of a liquid crystal display device as well as mass production.Embodiment 8
An embodiment according to the present invention will be described with reference to
The counter substrate may be provided only over the pixel area 3000 and the driver circuits 3001 and 3002, or may be provided over the entire surface alternatively. Note that, it is preferable that the CPU 3008 that may generate heat be provided with a heat sink contiguously.
Further, the panel also has a VRAM 3003 (video random access memory) for controlling the driver circuits 3001 and 3002, and decoders 3004 and 3005 at the periphery of the VRAM 3000. In addition, the panel has a RAM (random access memory) 3006, a decoder 3007 at the periphery of the RAM 3006, and the CPU 3008.
All elements forming a circuit over the substrate 3009 are formed of a polycrystalline semiconductor (polysilicon) that has higher field-effect mobility and higher ON current than that of an amorphous semiconductor. Therefore, a plurality of circuits can be formed into an integrated circuit over one insulating surface. A pixel area 3001, driver circuits 3001 and 3002, and another circuit are formed over a support substrate first, and separated by the delamination method according to the present invention, then, pasted with each other thereby achieving an integrated structure over there flexible substrate 3009. The structure of the plural pixels in the pixel area is, but not exclusively, formed by providing SRAM to each of the plural pixels. Thus, VRAM 3003 and RAM 3006 may be omitted.Embodiment 9
The present invention can be applied to various electronic devices. Given as examples as the electronic devices: a personal digital assistance (a cellular phone, a mobile computer, a portable game machine, an electronic book, or the like), a video camera, a digital camera, a goggle type display, a display, a navigation system, and the like.
Since the application range of the present invention is extremely large, the present invention can be applied to various electronic devices in all fields. Especially, the present invention that enables devices to be thinner and/or lighter is remarkably effective for the electronic devices illustrated in
By employing a delamination method according to the present invention, a TFT or the like can be formed over a flexible film substrate achieving high yield since separation can be performed in the whole surface. Further, a burden caused by a laser or the like are not placed on a TFT in the present invention. Thus, a light emitting device, a display unit of a liquid crystal display device, or the like, which has the TFT and the like can be made thin, hard to be broken even if it drops, and lightweight. Further, display on a curved surface or in odd-shape is enabled.
A TFT on a film substrate, which is formed according the present invention can achieve the enlargement of display units as well as mass production. The present invention enables the recycling of a first substrate on which a TFT or the like to be formed before transferring, and achieves reducing costs of a semiconductor film by employing a low-cost film substrate.
1. A light emitting device comprising:
- a plastic substrate;
- a metal oxide which is scattered over a surface of the plastic substrate;
- a transistor over the metal oxide; and
- a light emitting element which is over and electrically connected to the transistor.
2. The light emitting device according to claim 1, further comprising a barrier film over the plastic substrate, the barrier film comprising at least one of silicon nitride, silicon oxide, and aluminum oxide.
3. The light emitting device according to claim 1, further comprising a barrier film over the plastic substrate, the barrier film comprising a lamination of silicon nitride and silicon oxide.
4. The light emitting device according to claim 1, wherein the metal oxide has crystallinity.
5. The light emitting device according to claim 1, wherein the light emitting device includes a curved surface.
6. The light emitting device according to claim 1, wherein the metal oxide comprises tungsten.
7. The light emitting device according to claim 1, wherein the metal oxide comprises at least one material selected from Ti, Ta, Mo, Nd, Ni, Co, Zr, Zn, Ru, Rh, Pd, Os, and Ir.