JP2005164880A - Light emitting device, and method of manufacturing light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting device capable of being manufactured through a more simple manufacturing process reduced in the number of steps and reducing the variation of luminance of a light emitting element caused by the variation of a gate voltage Vgs of a TFT controlling a current supplied to the light emitting element while reducing the area of a capacitive element . <P>SOLUTION: The light emitting device is provided with the light emitting element, a first TFT for determining a current value of a current flowing to the light emitting element, a second TFT for determining light emission and non-emission of the light emitting element, a first power line, and a second power line, and the first and second TFTs are connected in series between the light emitting element and the first power line, and a gate electrode of the first TFT is connected to the second power line, and one of gate electrodes of the fist and second TFTs and the first and second power lines is formed by using a liquid drop discharge method or a printing method. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a light-emitting device having a means for supplying current to a light-emitting element and the light-emitting element in each of a plurality of pixels, and a method for manufacturing the light-emitting device.

  Since the light emitting element emits light by itself, the visibility is high, a backlight necessary for a liquid crystal display (LCD) is not necessary, and it is optimal for thinning, and the viewing angle is not limited. For this reason, a light emitting device using a light emitting element has attracted attention as a display device that replaces a CRT or LCD, and has recently been put into practical use, for example, mounted in an electronic device such as a mobile phone or a digital still camera.

  Light emitting devices can be classified into a passive matrix type and an active matrix type. The active matrix type can maintain the current supply to the light emitting element to some extent even after the video signal is input, and can flexibly cope with the increase in size and definition of the panel, and is becoming the mainstream in the future. Specifically, the configuration of the pixels in the active matrix light-emitting device that has been proposed differs depending on the manufacturer of the light-emitting device, and each has its own technical ideas, but usually at least the light-emitting element, A thin film transistor (TFT) for controlling input of a video signal to the pixel and a TFT for supplying current to the light emitting element are provided in each pixel.

  By the way, if the off current of the TFT that controls the input of the video signal to the pixel is large, the gate electrode of the TFT that controls the current value supplied to the light emitting element in accordance with the change in the potential of the video signal input to the other pixel. The voltage between source regions (hereinafter referred to as gate voltage) Vgs is likely to fluctuate. In order to prevent the fluctuation of the gate voltage Vgs, the capacitance of the capacitive element provided between the gate electrode and the source region of the TFT is increased, or the off-current of the TFT for controlling the input of the video signal to the pixel is kept low. It is necessary to do. However, increasing the area occupied by the capacitive element is not desirable because it increases the probability of leakage between the electrodes due to dust and the like, thereby leading to a decrease in yield. In addition, the TFT fabrication process is optimized to satisfy both the low off-current of the TFT that controls the input of video signals to the pixel and the high on-current to charge a large capacity. It takes a lot of cost and time, and is a difficult task. In addition, the gate voltage Vgs of the TFT that controls the current supplied to the light emitting element fluctuates due to the parasitic capacitance attached to the gate electrode, due to the switching of other TFTs, the fluctuation of the potential of the signal line, the scanning line, and the like. There is also a problem that it is easy.

  In general, an active matrix light-emitting device uses a lithography method for patterning. When the lithography method is used, a series of steps such as formation of a photoresist, exposure, development, etching, and peeling are required, so that the manufacturing process becomes complicated and the cost increases. Further, the lithography method requires an expensive exposure mask (photomask), which is one of the reasons why the cost for manufacturing the light-emitting device cannot be suppressed. Then, after the film formation, a portion that is removed by etching is eventually discarded, and thus the material is useless, which is not preferable from the viewpoint of cost reduction.

  Moreover, since the wiring becomes inevitably longer when the panel is enlarged, there arises a problem that the signal is delayed due to the wiring resistance. In this case, it is considered that if the wiring is thickened and the cross-sectional area is widened, the wiring resistance can be lowered, and thus signal delay can be avoided. However, when the wiring is formed by using the lithography method, the thickness of the wiring is about 200 to 400 μm at most, and if it is thicker than that, it takes time for the etching process, which is not desirable.

  In view of the above-described problems, the present invention can be formed using a simpler manufacturing process in which the number of processes is suppressed, and the gate voltage of the TFT that controls the current supplied to the light emitting element while suppressing the area of the capacitor element. It is an object of the present invention to propose a light emitting device that can suppress variations in luminance of light emitting elements caused by fluctuations in Vgs. Another object of the present invention is to propose a light-emitting device and a method for manufacturing the light-emitting device that can suppress an increase in wiring resistance due to an increase in size while suppressing time spent in a wiring manufacturing process.

  In the present invention, a TFT (current control TFT) functioning as a switching element is connected in series to the driving TFT in addition to a TFT (driving TFT) that determines the value of the current supplied to the light emitting element. At least in a period for displaying an image, a fixed potential is applied to the gate electrode to turn on the driving TFT so that a current can always flow. The current control TFT is operated in a linear region, and the potential of its gate electrode is controlled by a video signal input to the pixel.

  By operating the current control TFT in the linear region, the voltage between the source region and the drain region (drain voltage) Vds becomes very small with respect to the voltage Vel applied to the light emitting element, and a slight variation in the gate voltage Vgs It becomes difficult to influence the current flowing through the light emitting element. The potential of the gate electrode of the driving TFT is fixed without being controlled by the video signal. Therefore, even if the capacitance of the capacitor provided between the gate electrode and the source region of the current control TFT is not increased, or the off current of the TFT that controls the input of the video signal to the pixel is not reduced, The current flowing through the light emitting element is less likely to fluctuate. Further, the current flowing through the light emitting element is not affected by the parasitic capacitance attached to the gate electrode of the current control TFT. The current control TFT only selects whether or not current is supplied to the light emitting element, and the value of the current flowing through the light emitting element is determined by the driving TFT. For this reason, variation factors can be reduced and the image quality can be greatly improved. In addition, since it is not necessary to optimize the process in order to keep the TFT off current that controls the input of video signals to the pixels low, the TFT manufacturing process can be simplified, greatly contributing to cost reduction and yield improvement. can do.

  In the present invention, the driving TFT is desirably operated in the saturation region, but may be operated in the linear region. Compared with the linear region, the drain current is more likely to affect the slight fluctuation of the voltage (gate voltage) Vgs between the gate electrode and the source region in the saturation region. However, in the present invention, even when the driving TFT is operated in the saturation region, the gate voltage Vgs does not vary because the potential of the gate electrode of the driving TFT is fixed. By operating the driving TFT in the saturation region, the drain current is not changed by the drain region-source region voltage (hereinafter referred to as drain voltage) Vds, but is determined only by Vgs. Accordingly, even if Vds decreases instead of Vel increasing, the value of the drain current is kept relatively constant. Therefore, it is possible to suppress a decrease in luminance or luminance unevenness due to deterioration of the electroluminescent material.

  Note that the value of the channel length L with respect to the channel width W in the driving TFT is made larger than the value of the channel length L with respect to the channel width W in the current control TFT. With the above structure, variation in luminance of the light-emitting element between pixels due to a difference in characteristics of the driving TFT can be further suppressed.

  In the present invention, the light-emitting device having the above structure is formed by a screen printing method, a printing method typified by an offset printing method, or a droplet discharge method. The droplet discharge method means a method of forming a predetermined pattern by discharging droplets containing a predetermined composition from the pores, and includes an ink jet method and the like in its category. By using the above printing method and droplet discharge method, various wirings typified by signal lines and scanning lines, TFT gate electrodes, light emitting element electrodes, etc. can be formed without using an exposure mask. become. However, in the light emitting device of the present invention, it is not necessary to use a printing method or a droplet discharge method for all the steps of forming a pattern. Therefore, for example, a printing method or a droplet discharge method is used in at least a part of the process, for example, a printing method or a droplet discharge method is used for forming a wiring and a gate electrode, and a lithography method is used for patterning a semiconductor film. What is necessary is just to use, and the lithography method may be used together. A mask used for patterning may be formed by a printing method or a droplet discharge method.

  Note that the light-emitting device of the present invention includes a panel in which a light-emitting element is sealed, and a module in which an IC or the like including a controller is mounted on the panel. Furthermore, in the process of manufacturing the light emitting device, the present invention may include in its category an element substrate corresponding to one mode before the light emitting element is completed. Specifically, the element substrate has means (TFT) for supplying current to the light emitting element in each of the plurality of pixels. The element substrate may be in a state where only the first electrode of the light-emitting element is formed, or after the conductive film to be the first electrode is formed and patterned to form the first electrode. It may be in the state before being applied, and all forms are applicable.

  In addition, in this specification, the light-emitting element includes, in its category, an element whose luminance is controlled by current or voltage. Specifically, the light-emitting element is used for OLED (Organic Light Emitting Diode) and FED (Field Emission Display). MIM type electron source elements (electron emitting elements) and the like are included.

  In the present invention, it is possible to suppress the luminance variation of the light emitting element caused by the fluctuation of the gate voltage Vgs of the driving TFT that controls the current supplied to the light emitting element while suppressing the area of the capacitor element.

  Further, in the present invention, by forming a pattern using a droplet discharge method or a printing method, a series of steps such as photoresist film formation, exposure, development, etching, and peeling performed by a lithography method can be simplified. it can. Further, unlike the lithography method, the droplet discharge method and the printing method do not waste material that is removed by etching. Further, it is not necessary to use an expensive exposure mask, so that the cost for manufacturing the light-emitting device can be suppressed.

  Further, unlike the lithography method, it is not necessary to perform etching to form the wiring. Therefore, the time spent for the process of forming the wiring can be significantly shortened compared to the case of the lithography method. In particular, when the wiring thickness is 0.5 μm or more, and more desirably 2 μm or more, the wiring resistance can be suppressed. Therefore, the wiring accompanying the increase in the size of the light-emitting device while suppressing the time spent in the wiring manufacturing process. An increase in resistance can be suppressed.

  FIG. 1 illustrates one mode of a pixel included in the light-emitting device of the present invention. The pixel shown in FIG. 1 controls a light emitting element 101, a TFT (switching TFT) 102 used as a switching element for controlling input of a video signal to the pixel, and a current value supplied to the light emitting element 101. A driving TFT 103 and a current control TFT 104 for selecting whether to supply current to the light emitting element 101 are provided. Further, as in this embodiment, a capacitor 105 for holding the potential of the video signal may be provided in the pixel.

  In FIG. 1, the switching TFT 102, the driving TFT 103, and the current control TFT 104 have the same polarity, but the polarity may be either n-type or p-type. However, when a semi-amorphous semiconductor (microcrystalline semiconductor) body or an amorphous semiconductor is used for the TFT, the n-type has higher mobility than the p-type, so that the switching TFT 102, the driving TFT 103, and the current control are obtained. It is desirable to make all the TFTs 104 for use n-type. In this embodiment mode, a case where the switching TFT 102, the driving TFT 103, and the current control TFT 104 are all n-type will be described. A TFT using an amorphous semiconductor or a semi-amorphous semiconductor has an advantage that cost and yield can be increased because the number of manufacturing steps is smaller than that of a TFT using a polycrystalline semiconductor. Further, since it is not necessary to provide a crystallization step after the formation of the semiconductor film, it is relatively easy to enlarge the panel.

A semi-amorphous semiconductor is a film containing a semiconductor having an intermediate structure between amorphous and crystalline structures (including single crystal and polycrystal). This semi-amorphous semiconductor is a semiconductor having a third state which is stable in terms of free energy, and is a crystalline one having a short-range order and having a lattice strain, and having a grain size of 0.5 to 20 nm. It can be dispersed in a single crystal semiconductor. The semi-amorphous semiconductor has its Raman spectrum shifted to a lower wavenumber than 520 cm ⁻¹ , and diffraction peaks of (111) and (220), which are considered to be derived from the Si crystal lattice in X-ray diffraction, are observed. . Further, hydrogen or halogen is contained at least 1 atomic% or more as a neutralizing agent for dangling bonds. Here, for convenience, such a semiconductor is referred to as a semi-amorphous semiconductor (SAS). Further, by adding a rare gas element such as helium, argon, krypton, or neon to further promote lattice distortion, stability is improved and a good semi-amorphous semiconductor can be obtained.

  In this embodiment, an example in which the driving TFT 103 is operated in a saturation region is described; however, the driving TFT 103 may be operated in a linear region. The switching TFT 102 and the current control TFT 104 are operated in a linear region. As the driving TFT 103, an enhancement type TFT or a depletion type TFT may be used.

  The gate electrode of the switching TFT 102 is connected to the scanning line Gj (j = 1 to y). One of the source region and the drain region of the switching TFT 102 is connected to the signal line Si (i = 1 to x), and the other is connected to the gate electrode of the current control TFT 104. The gate electrode of the driving TFT 103 is connected to the second power supply line Wi (i = 1 to x). In the driving TFT 103 and the current control TFT 104, the current supplied from the first power supply line Vi (i = 1 to x) is supplied to the light emitting element 101 as the drain current of the driving TFT 103 and the current control TFT 104. As described above, the light source element 101 is connected to the first power supply line Vi (i = 1 to x). In this embodiment mode, the source region of the current control TFT 104 is connected to the first power supply line Vi (i = 1 to x), and the drain region of the driving TFT 103 is connected to the first electrode of the light emitting element 101. .

  Note that the source region of the driving TFT 103 may be connected to the first power supply line Vi (i = 1 to x), and the drain region of the current control TFT 104 may be connected to the first electrode of the light emitting element 101.

  The light-emitting element 101 includes a first electrode, a second electrode, and an electroluminescent layer formed between the first electrode and the second electrode. One of the first electrode and the second electrode corresponds to an anode, and the other corresponds to a cathode. In the case where the driving TFT 103 is n-type, it is preferable that the first electrode is a cathode and the second electrode is an anode. On the other hand, when the driving TFT 103 is a p-type, it is desirable that the first electrode is an anode and the second electrode is a cathode. In this embodiment mode, since the driving TFT 103 is an n-type, the case where the first electrode is a cathode and the second electrode is an anode will be described.

  One of the two electrodes of the capacitor 105 is connected to the first power supply line Vi (i = 1 to x), and the other is connected to the gate electrode of the current control TFT 104. The capacitive element 105 is provided to hold the gate voltage of the current control TFT 104. Note that FIG. 1 illustrates a structure in which the capacitor 105 is provided; however, the present invention is not limited to this structure, and the gate voltage of the current control TFT 104 can be obtained using the gate capacitance of the current control TFT 104 without providing the capacitor 105. May be held.

  Next, a method for driving the pixel shown in FIG. 1 will be described. The operation of the pixel illustrated in FIG. 1 can be described by being divided into a writing period and a holding period. FIG. 2A shows an operation when the current control TFT 104 is on in the writing period, and FIG. 2B shows an operation when the current control TFT 104 is off in the writing period. FIG. 2C shows an operation when the current control TFT 104 is on in the holding period, and FIG. 2D shows an operation when the current control TFT 104 is off in the holding period. 2A to 2D, the switching TFT 102 and the current control TFT 104 are simply shown as switches for easy understanding of the operation.

  First, in the writing period, when the scanning line Gj (j = 1 to y) is selected, the switching TFT 102 whose gate electrode is connected to the scanning line Gj (j = 1 to y) is turned on. The video signal input to the signal line Si (i = 1 to x) is input to the gate electrode of the current control TFT 104 via the switching TFT 102. Switching of the current control TFT 104 is controlled by the potential of the input video signal. On the other hand, the gate electrode of the driving TFT 103 always has a potential high enough to turn on the driving TFT 103 when the current control TFT is on from the second power supply line Wi (i = 1 to x). Is given.

  Note that in this embodiment mode, potentials having different heights are applied to the first power supply line Vi (i = 1 to x) and the second electrode of the light-emitting element 101 in the writing period and the holding period, respectively. The two potentials are set to such a height that a forward bias current is supplied to the light emitting element 101 when the driving TFT 103 and the current control TFT 104 are on. Therefore, as illustrated in FIG. 2A, when the current control TFT 104 is turned on, a current is supplied to the light-emitting element 101, and the light-emitting element 101 emits light. As shown in FIG. 2B, when the current control TFT 104 is turned off, the supply of current to the light-emitting element 101 is stopped, and the light-emitting element 101 is in a non-light-emitting state.

  In the present invention, as described above, when the current control TFT 104 is on during the writing period, it is not always necessary to cause the light emitting element to emit light in accordance with the video signal. For example, in the writing period, the supply of current to the light emitting element 101 may be stopped regardless of the switching of the current control TFT 104. Specifically, a potential difference between the second electrode of the light-emitting element 101 and the first power supply line Vi may be filled. Alternatively, when the light-emitting element 101 is regarded as a diode, the second electrode and the first power supply line Vi (i = 1 to 1) are applied so that a reverse bias voltage is applied between the pair of electrodes included in the light-emitting element 101. The potential difference between x) may be set. Alternatively, the path of the current flowing through the light emitting element 101 may be blocked by a switch or the like. In this case, the current supply to the light emitting element 101 is stopped in the writing period regardless of whether the current control TFT 104 is on or off. Therefore, in the writing period, all the light-emitting elements 101 are in a non-light-emitting state.

  Next, the potential of the video signal written in the writing period is held by turning off the switching TFT 102 by controlling the potential of the scanning line Gj (j = 1 to y), and the holding period is started. .

  In the holding period, if the current control TFT 104 is on between the second electrode of the light emitting element 101 and the first power supply line Vi (i = 1 to x), a forward bias current is applied to the light emitting element 101. A potential difference is provided so that is supplied. Furthermore, if the current control TFT is on, a path for the current flowing through the light emitting element is secured.

  Therefore, when the current control TFT 104 is turned on by a video signal, current is supplied to the light-emitting element 101 as illustrated in FIG. The current flowing through the light emitting element 101 is determined by the drain current of the driving TFT 103 and the voltage-current characteristics of the light emitting element 101. Then, the light emitting element 101 emits light with a luminance with a height corresponding to the supplied current. On the other hand, when the current control TFT 104 is turned off in the writing period, the potential of the video signal is held by the capacitor 105 as shown in FIG. The light emitting element 101 is in a non-light emitting state.

  Note that in the pixel illustrated in FIG. 1, supply of current to the light emitting element 101 is stopped by filling a potential difference between the second electrode of the light emitting element 101 and the first power supply line Vi (i = 1 to x). An example of the structure of the switch is illustrated in FIG. Note that FIG. 3A illustrates the case where the first electrode is a cathode and the second electrode is an anode. As shown in FIG. 3A, by switching the switch 110, the potential Vss is applied to the first power supply line Vi and the second electrode of the light-emitting element 101 in the writing period, and the light-emitting element in the holding period. The potential Vdd can be applied to the second electrode of the light-emitting element 101 and the potential Vss can be applied to the first power supply line Vi so that a forward bias current is supplied to the light-emitting element 101. However, Vdd> Vss. Note that in the case where the first electrode is an anode and the second electrode is a cathode, the potential Vdd is applied to the first power supply line Vi and the second electrode of the light-emitting element 101 in the writing period, and the light-emitting element 101 in the holding period. The potential Vss is applied to the second electrode of the light emitting element 101 and the potential Vdd is applied to the first power supply line Vi so that a forward bias current is supplied to the first power supply line Vi.

  In addition, FIG. 3B illustrates a structure of a switch in the pixel illustrated in FIG. 1 in the case where supply of current to the light-emitting element 101 is stopped by blocking a path of current flowing through the light-emitting element 101. Note that FIG. 3B illustrates the case where the first electrode is a cathode and the second electrode is an anode. As shown in FIG. 3B, by turning off the switch 111 in the writing period, the path of the current flowing through the light-emitting element 101 is cut off and the second electrode is floated, and the switch 111 is turned on in the holding period. Thus, a path for a current flowing through the light emitting element 101 can be secured, and a forward bias current can be supplied to the light emitting element 101.

  Note that in the case where the video signal is digital, gradation may be displayed by controlling the time during which the light-emitting element emits light (time gradation method), or gradation may be displayed by the area where the light-emitting element emits light. Good (area gradation method). For example, when the time gray scale method is used in this embodiment, a writing period and a holding period corresponding to each bit of the video signal are provided in one frame period. In addition, within one frame period, gradation can be displayed by controlling the total length of the writing period and the holding period during which the light emitting element emits light with a video signal. Note that in the case of a driving method in which all light-emitting elements are in a non-light-emitting state in the writing period regardless of the potential of the video signal, the video signal indicates the total length of the holding period in which the light-emitting element emits light within one frame period. By controlling, gradation can be displayed.

  Next, a more specific structure and a manufacturing method of the light-emitting device of the present invention will be described with reference to FIGS.

  First, as shown in FIG. 4A, a substrate 200 on which TFTs and light emitting elements are formed is prepared. Specifically, for example, a glass substrate such as barium borosilicate glass or alumino borosilicate glass, a quartz substrate, a ceramic substrate, or the like can be used as the substrate 200. Alternatively, a metal substrate including a SUS substrate or a semiconductor substrate with an insulating film formed on the surface thereof may be used. A substrate made of a synthetic resin having flexibility such as plastic generally tends to have a lower heat resistant temperature than the above substrate, but can be used as long as it can withstand the processing temperature in the manufacturing process. . The surface of the substrate 200 may be planarized by polishing such as a CMP method.

  Pretreatment for improving the adhesion of the conductive film or the insulating film formed by using the droplet discharge method or the printing method is performed on the surface of the substrate 200 described above. Specifically, as a method for improving the adhesion, for example, a method of attaching a metal or a metal compound capable of improving the adhesion of a conductive film or an insulating film to the surface of the substrate 200 by a catalytic action, a formed conductive A method of adhering an organic insulating film, metal, or metal compound having high adhesion to a film or an insulating film to the surface of the substrate 200, surface treatment by performing plasma treatment on the surface of the substrate 200 under atmospheric pressure or reduced pressure The method of performing is mentioned. Examples of the metal having high adhesion to the conductive film or insulating film include titanium, titanium oxide, 3d transition elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn. Is mentioned. Examples of the metal compound include the above-described metal oxides, nitrides, and oxynitrides. Examples of the organic insulating film include an insulating film including a Si—O—Si bond (hereinafter, referred to as a siloxane insulating film) formed using polyimide or a siloxane material as a starting material. The siloxane insulating film may have at least one of fluorine, an alkyl group, and aromatic hydrocarbon in addition to hydrogen as a substituent.

  Note that when the metal or the metal compound attached to the substrate 200 has conductivity, the sheet resistance is controlled so that the normal operation of the semiconductor element is not hindered. Specifically, the average thickness of the conductive metal or metal compound is controlled to be, for example, 1 to 10 nm, or the metal or metal compound is partially or entirely insulated by oxidation. You can do it. Alternatively, the deposited metal or metal compound may be selectively removed by etching except for the region where the adhesion is desired to be improved. Alternatively, the metal or the metal compound may be selectively attached only to a specific region by using a droplet discharge method, a printing method, a sol-gel method, or the like, instead of attaching the metal or the metal compound to the entire surface of the substrate in advance. The metal or metal compound does not need to be a completely continuous film on the surface of the substrate 200, and may be dispersed to some extent.

In this embodiment mode, a photocatalyst such as ZnO or TiO ₂ that can improve adhesion by a photocatalytic reaction is attached to the surface of the substrate 200. Specifically, ZnO or TiO ₂ is dispersed in a solvent and distributed on the surface of the substrate 200, or a Zn compound or Ti compound is attached to the surface of the substrate 200 and then oxidized, or a sol-gel method. As a result, ZnO or TiO ₂ can be attached to the surface of the substrate 200 as a result.

  Next, gate electrodes 201 to 203 are formed on the surface of the substrate 200 that has been subjected to pretreatment for improving adhesion, using a droplet discharge method or various printing methods. Specifically, for the gate electrodes 201 to 203, a conductive material including one or more metals such as Ag, Au, Cu, and Pd and a metal compound is used. Note that a conductive material having one or more metals, such as Cr, Mo, Ti, Ta, W, and Al, or a metal compound, can be used as long as aggregation can be suppressed by the dispersant. is there. A gate electrode in which a plurality of conductive films are stacked can be formed by performing film formation of a conductive material a plurality of times by a droplet discharge method or various printing methods. Also, for example, conductive particles coated with Cu with Ag can be used.

  In the case of using a droplet discharge method, a conductive material dispersed in an organic or inorganic solvent is dropped from a nozzle and then dried or baked at room temperature. Specifically, in this embodiment, a solution in which Ag is dispersed in tetradecane is dropped, and the solvent is removed by baking at 200 ° C. to 300 ° C. for 1 min to 50 hr, whereby the gate electrodes 201 to 203 are formed. When an organic solvent is used, the baking can be performed in an oxygen atmosphere, whereby the solvent can be efficiently removed and the resistance of the gate electrodes 201 to 203 can be further reduced. Although not shown, a scanning line connected to the gate electrode 201 in this step can also be formed at the same time.

  When the droplet discharge method is used, the accuracy of the pattern depends on the discharge amount per dot of the droplet, the surface tension of the solution, the water repellency of the surface of the substrate 200 onto which the droplet is dropped. Therefore, it is desirable to optimize these conditions according to the accuracy of the desired pattern.

Here, the evaluation of the adhesiveness of Ag when titanium oxide is adhered to the surface of the substrate before Ag is ejected by the droplet ejection method will be described. First, a titanium film having a thickness of 1 to 5 nm was formed on a glass substrate by sputtering. The titanium film formed by baking at 230 ° C. was oxidized to form titanium oxide. At this time, when the sheet resistance of the film formed of titanium oxide was measured, it became lower than the lower limit of 1 × 10 ⁻⁶ Ω / □ that can be measured by the apparatus, so that it was confirmed that the insulation was sufficiently high. .

  Next, Ag was dropped onto 16 areas using a droplet discharge method, and then fired at 230 ° C. In addition, after baking, the dimension of the strip-shaped Ag film | membrane formed in each area of 16 places became length 1cm, width 200-300 micrometers, and thickness 400-500 nm.

  After a Kapton (R) tape was applied to the substrate on which the Ag film was formed, the tape was peeled off to confirm the adhesion of the Ag film. As a result, no peeling of the Ag film was observed even after the tape was removed. . The substrate on which the Ag film was formed was immersed in a 0.5 wt% HF aqueous solution for 1 minute and then washed with running water to confirm the adhesion of the film. As a result, all the Ag film was not peeled off and was deposited on the substrate. It remained. The same result was obtained when titanium oxide was adhered to the surface of the substrate by spreading a solution in which the titanium oxide film was dispersed in the solvent on the surface of the substrate. By the way, when using a bare glass substrate, a glass substrate with a CMP polished surface, a glass substrate on which an amorphous silicon film, a silicon nitride film or a silicon oxide film is formed, there are some differences, but there are Only about this amount of Ag film remained. Therefore, it is considered that high adhesion is obtained by titanium oxide.

  Next, a gate insulating film 205 is formed so as to cover the gate electrodes 201 to 203. As the gate insulating film 205, for example, an insulating film such as silicon oxide, silicon nitride, or silicon nitride oxide can be used. As the gate insulating film 205, a single-layer insulating film may be used, or a plurality of insulating films may be stacked. In this embodiment, an insulating film in which silicon nitride, silicon oxide, and silicon nitride are sequentially stacked is used as the gate insulating film 205. As a film formation method, a plasma CVD method, a sputtering method, or the like can be used. In order to form a dense insulating film capable of suppressing gate leakage current at a low deposition temperature, a rare gas element such as argon is preferably contained in the reaction gas and mixed into the formed insulating film. Aluminum nitride can be used for the gate insulating film 205. Aluminum nitride has a relatively high thermal conductivity and can efficiently dissipate heat generated in the TFT.

  Next, as illustrated in FIG. 4B, the first electrode 206 included in the light-emitting element is formed over the gate insulating film 205. Note that in this embodiment mode, the first electrode 206 corresponds to a cathode and the second electrode 236 formed later corresponds to an anode; however, the present invention is not limited to this structure. The first electrode 206 may correspond to an anode, and the second electrode 236 may correspond to a cathode.

As the cathode, a metal, an alloy, an electrically conductive compound, a mixture thereof, or the like having a low work function can be used. Specifically, alkali metals such as Li and Cs, and alkaline earth metals such as Mg, Ca, and Sr, alloys containing these (Mg: Ag, Al: Li, Mg: In, etc.), and compounds thereof ( In addition to CaF ₂ and CaN, rare earth metals such as Yb and Er can be used. When an electron injection layer is provided, other conductive layers such as Al can be used. When light is extracted from the cathode side, other light-transmitting oxide conductive materials such as indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO), and gallium-added zinc oxide (GZO) are used. It is possible to use. Indium tin oxide containing ITO and silicon oxide (hereinafter referred to as ITSO) or indium oxide containing silicon oxide mixed with 2 to 20% zinc oxide (ZnO) may be used. In the case of using a light-transmitting oxide conductive material, it is desirable to provide an electron injection layer in the electroluminescent layer 235 to be formed later. In addition, without using a light-transmitting oxide conductive material, light can be extracted from the cathode side by forming the cathode with a film thickness that allows light to pass therethrough (preferably, about 5 nm to 30 nm). In this case, a light-transmitting conductive layer may be formed using a light-transmitting oxide conductive material so as to be in contact with or under the cathode so as to suppress the sheet resistance of the cathode.

  In this embodiment, Mg: Ag is used as the first electrode 206 corresponding to the anode. Note that the first electrode 206 can be formed by a sputtering method, a droplet discharge method, or a printing method. In the case of using a droplet discharge method or a printing method, the first electrode 206 can be formed without using a mask. Even when the sputtering method is used, by forming the resist used in the lithography method by a droplet discharge method or a printing method, it is not necessary to separately prepare an exposure mask, which leads to cost reduction.

  Note that the first electrode 206 may be polished and polished by a CMP method or a polyvinyl alcohol-based porous body so that the surface thereof is planarized. Further, after polishing using the CMP method, the surface of the cathode may be irradiated with ultraviolet rays, oxygen plasma treatment, or the like.

  Next, as shown in FIG. 4C, a first semiconductor film 207 is formed. The first semiconductor film 207 can be formed using an amorphous semiconductor or a semi-amorphous semiconductor (SAS). A polycrystalline semiconductor film may also be used. In this embodiment, a semi-amorphous semiconductor is used for the first semiconductor film 207. A semi-amorphous semiconductor has higher crystallinity and higher mobility than an amorphous semiconductor and can be formed without increasing the number of steps for crystallization unlike a polycrystalline semiconductor.

An amorphous semiconductor can be obtained by glow discharge decomposition of a silicide gas. Typical silicide gases include SiH ₄ and Si ₂ H ₆ . This silicide gas may be diluted with hydrogen, hydrogen and helium.

SAS can also be obtained by glow discharge decomposition of silicide gas. A typical silicide gas is SiH ₄ , and in addition, Si ₂ H ₆ , SiH ₂ Cl ₂ , SiHCl ₃ , SiCl ₄ , SiF _{4 and the} like can be used. In addition, it is easy to form a SAS by diluting and using this silicide gas with hydrogen or a gas obtained by adding one or more kinds of rare gas elements selected from helium, argon, krypton, and neon to hydrogen. It can be. It is preferable to dilute the silicide gas at a dilution rate in the range of 2 to 1000 times. Furthermore, a carbide gas such as CH ₄ or C ₂ H ₆ , a germanium gas such as GeH ₄ or GeF ₄ , F ₂ or the like is mixed in the silicide gas, so that the energy bandwidth is 1.5-2. You may adjust to 4 eV or 0.9-1.1 eV. A TFT using SAS as the first semiconductor film can obtain a mobility of 1 to 10 cm ² / Vsec or more.

  Alternatively, the first semiconductor film may be formed by stacking a plurality of SAS formed of different gases. For example, among the various gases described above, a first semiconductor film is formed by stacking a SAS formed using a gas containing a fluorine atom and a SAS formed using a gas containing a hydrogen atom. Can do.

The reaction production of the coating by glow discharge decomposition can be performed under reduced pressure or atmospheric pressure. When performed under reduced pressure, the pressure may be approximately in the range of 0.1 Pa to 133 Pa. The power for forming the glow discharge may be high frequency power of 1 MHz to 120 MHz, preferably 13 MHz to 60 MHz. The pressure is in the range of approximately 0.1 Pa to 133 Pa, and the power supply frequency is 1 MHz to 120 MHz, preferably 13 MHz to 60 MHz. The substrate heating temperature may be 300 ° C. or less, preferably 100 to 250 ° C. As an impurity element in the film, impurities of atmospheric components such as oxygen, nitrogen, and carbon are desirably 1 × 10 ²⁰ atoms / cm ³ or less, and in particular, the oxygen concentration is preferably 5 × 10 ¹⁹ atoms / cm ³ or less. Is 1 × 10 ¹⁹ atoms / cm ³ or less.

Note that in the case where a semiconductor film is formed using Si ₂ H ₆ and GeF ₄ or F ₂ , crystals grow from a side closer to the substrate of the semiconductor film, so that the crystallinity of the semiconductor film becomes closer to the side closer to the substrate. high. Therefore, in the case of a bottom-gate TFT whose gate electrode is closer to the substrate than the first semiconductor film, a region having high crystallinity on the side close to the substrate in the first semiconductor film can be used as a channel formation region. Suitable for, can increase the mobility more.

Further, when a semiconductor film is formed using SiH ₄ and H ₂ , larger crystal grains can be obtained on the side closer to the surface of the semiconductor film. Therefore, in the case of a top-gate TFT in which the first semiconductor film is closer to the substrate than the gate electrode, a region having high crystallinity on the side far from the substrate in the first semiconductor film can be used as a channel formation region. Suitable for, can increase the mobility more.

In addition, SAS shows a weak n-type conductivity when impurities intended for valence electron control are not intentionally added. This is because oxygen is easily mixed into the semiconductor film because glow discharge with higher power is performed than when an amorphous semiconductor is formed. Therefore, the threshold value can be controlled by adding an impurity imparting p-type to the first semiconductor film provided with the channel formation region of the TFT at the same time as or after the film formation. It becomes possible. The impurity imparting p-type is typically boron, and an impurity gas such as B ₂ H ₆ or BF ₃ may be mixed in the silicide gas at a rate of 1 ppm to 1000 ppm. For example, when boron is used as an impurity imparting p-type conductivity, the boron concentration is preferably 1 × 10 ^{14 to} 6 × 10 ¹⁶ atoms / cm ³ .

  Next, protective films 208 to 210 are formed over the first semiconductor film 207 so as to overlap with a portion of the first semiconductor film 207 which becomes a channel formation region. The protective films 208 to 210 may be formed using a droplet discharge method or a printing method, or may be formed using a CVD method, a sputtering method, or the like. As the protective films 208 to 210, an inorganic insulating film such as silicon oxide, silicon nitride, or silicon nitride oxide, a siloxane-based insulating film, or the like can be used. Alternatively, these films may be stacked and used as the protective films 208 to 210. In this embodiment mode, silicon nitride formed by a plasma CVD method and a siloxane insulating film formed by a droplet discharge method are stacked and used as the protective films 208 to 210. In this case, patterning of silicon nitride can be performed using a siloxane insulating film formed by a droplet discharge method as a mask.

  Next, as shown in FIG. 5A, the first semiconductor film 207 is patterned. For patterning the first semiconductor film 207, a lithography method may be used, or a resist formed by a droplet discharge method or a printing method may be used as a mask. In the latter case, it is not necessary to prepare a mask for exposure separately, which leads to cost reduction. In this embodiment mode, an example of patterning using a resist 211 formed by a droplet discharge method is shown. Note that the resist 211 can be formed using an organic resin such as polyimide or acrylic. Then, patterned first semiconductor films 212 and 213 are formed by dry etching using the resist 211.

  Next, as shown in FIG. 5B, part of the gate insulating film 205 is selectively removed by etching, so that part of the gate electrode 203 is exposed. For the etching of the gate insulating film 205, a lithography method may be used, or a resist formed by a droplet discharge method or a printing method may be used as a mask. In the latter case, it is not necessary to prepare a mask for exposure separately, which leads to cost reduction.

Next, as shown in FIG. 5C, a second semiconductor film 214 is formed so as to cover the first semiconductor films 212 and 213 after patterning. An impurity imparting one conductivity type is added to the second semiconductor film 214 in advance. In the case of forming an n-channel TFT, an impurity imparting n-type conductivity, for example, phosphorus may be added to the second semiconductor film 214. Specifically, an impurity gas such as PH ₃ may be added to a silicide gas to form the second semiconductor film 214. The second semiconductor film 214 having one conductivity type can be formed using a semi-amorphous semiconductor or an amorphous semiconductor in the same manner as the first semiconductor films 212 and 213.

  Note that in this embodiment mode, the second semiconductor film 214 is formed in contact with the first semiconductor films 212 and 213; however, the present invention is not limited to this structure. A third semiconductor film functioning as an LDD region may be formed between the first semiconductor films 212 and 213 and the second semiconductor film 214. In this case, the third semiconductor film is formed using a semi-amorphous semiconductor or an amorphous semiconductor. The third semiconductor film originally exhibits a weak n-type conductivity type without intentionally adding an impurity for imparting the conductivity type. Therefore, the third semiconductor film can be used as an LDD region with or without an impurity for imparting conductivity type.

  Next, as illustrated in FIG. 6A, wirings 215 to 219 are formed by a droplet discharge method or a printing method, and the second semiconductor film 214 is etched using the wirings 215 to 219 as a mask. Etching of the second semiconductor film 214 can be performed by dry etching in a vacuum atmosphere or an atmospheric pressure atmosphere. Through the etching, second semiconductors 220 to 225 functioning as a source region or a drain region are formed from the second semiconductor film 214, and a part of the first electrode 206 is exposed. When the second semiconductor film 214 is etched, the protective films 208 to 210 can prevent the first semiconductor films 212 and 213 from being over-etched.

  The wirings 215 to 219 can be formed in a manner similar to that of the gate electrodes 201 to 203. Specifically, a conductive material including one or more metals such as Ag, Au, Cu, and Pd and a metal compound is used. In the case of using a droplet discharge method, a conductive material dispersed in an organic or inorganic solvent is dropped from a nozzle and then dried or baked at room temperature. A conductive material having one or more metals such as Cr, Mo, Ti, Ta, W, Al, or a metal compound can be used as long as aggregation can be suppressed by the dispersant and the dispersion can be dispersed in the solution. Baking may be performed in an oxygen atmosphere to reduce the resistance of the wirings 215 to 219. Further, the wirings 215 to 219 in which a plurality of conductive films are stacked can be formed by performing film formation of a conductive material a plurality of times by a droplet discharge method or various printing methods.

  Through the above process, the switching TFT 230, the driving TFT 231 and the current control TFT 232 are formed.

  Next, as illustrated in FIG. 6B, a partition wall 233 is formed so as to cover the switching TFT 230, the driving TFT 231, the current control TFT 232, and the end portion of the first electrode 206. The partition wall 233 can be formed using an organic resin film, an inorganic insulating film, or a siloxane-based insulating film. For example, acrylic resin, polyimide, polyamide, or the like can be used for the organic resin film, and silicon oxide, silicon nitride oxide, or the like can be used for the inorganic insulating film. In particular, a photosensitive organic resin film is used for the partition wall 233, an opening 234 is formed on the first electrode 206, and the side wall of the opening 234 is formed to be an inclined surface formed with a continuous curvature. By doing so, it is possible to prevent the first electrode 206 and the second electrode 236 formed later from being connected. At this time, the mask can be formed by a droplet discharge method or a printing method. The partition wall 233 itself can also be formed by a droplet discharge method or a printing method. Note that the partition wall 233 has an opening 234.

Next, before the electroluminescent layer 235 is formed, in order to remove moisture, oxygen, and the like adsorbed on the partition wall 233 and the first electrode 206, heat treatment is performed in an air atmosphere or heat treatment (vacuum baking) in a vacuum atmosphere. May be performed. Specifically, heat treatment is performed in a vacuum atmosphere at a substrate temperature of 200 ° C. to 450 ° C., preferably 250 to 300 ° C., for about 0.5 to 20 hours. It is desirably 3 × 10 ⁻⁷ Torr or less, and if possible, 3 × 10 ⁻⁸ Torr or less is most desirable. In the case where an electroluminescent layer is formed after heat treatment in a vacuum atmosphere, reliability can be further improved by placing the substrate in a vacuum atmosphere until just before the electroluminescent layer is formed. it can. Further, before or after vacuum baking, the first electrode 206 may be irradiated with ultraviolet rays.

  Note that in this embodiment mode, a passivation film 237 to be formed later is formed of silicon nitride, and the passivation film 237 is in contact with the second electrode 206 formed of ITSO. As described above, the first electrode or the second electrode of the light-emitting element is formed using the light-transmitting oxide conductive material such as ITSO and the conductive film including silicon oxide so as to be in contact with the insulating film including silicon nitride or silicon nitride oxide. By forming this electrode, the luminance of the light-emitting element can be increased as compared with any combination of the materials described above. Note that in the case where ITSO is used for the first electrode 206, the above-described vacuum baking is particularly effective because moisture easily adheres to silicon oxide contained therein.

  Then, an electroluminescent layer 235 is formed so as to be in contact with the first electrode 206 in the opening 234 of the partition wall 233. The electroluminescent layer 235 may be composed of a single layer or a plurality of layers stacked. In the case of a plurality of layers, an electron injection layer, an electron transport layer, a light emitting layer, a hole transport layer, and a hole injection layer are stacked in this order on the first electrode 206 corresponding to the cathode. Note that in the case where the first electrode 206 corresponds to an anode, the electroluminescent layer 235 is formed by sequentially stacking a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer.

  Note that when a monochrome image is displayed or when a color image is displayed using a white light emitting element and a color filter, the structure of the electroluminescent layer 235 is the same in all pixels. In the case of displaying a color image using three light emitting elements that emit light of three primary colors, the electroluminescent layer 235 may be applied separately by changing the material, the layer to be stacked, or the film thickness for each corresponding color. When the electroluminescent layer is separately applied, the droplet discharge method is very effective because there is no waste of material and the process can be simplified. Note that the color may be a full color using a mixed color or an area color in which a plurality of pixels having a single hue are arranged for each specific area.

  Note that the color filter may include a colored layer that can transmit light in a specific wavelength region and, in some cases, a shielding film that can shield visible light in addition to the colored layer. The color filter may be formed on a cover material for sealing the light emitting element or may be formed on an element substrate. In any case, the colored layer or the shielding film can be formed using a printing method or a droplet discharge method.

  The electroluminescent layer 235 can be formed by a droplet discharge method using any of a high molecular weight organic compound, a medium molecular weight organic compound, a low molecular weight organic compound, and an inorganic compound. Medium molecular organic compounds, low molecular organic compounds, and inorganic compounds may be formed by vapor deposition.

  Then, a second electrode 236 is formed so as to cover the electroluminescent layer 235. In this embodiment mode, the second electrode 236 corresponds to an anode. As a method for manufacturing the second electrode 236, an evaporation method, a sputtering method, a droplet discharge method, or the like is preferably used depending on the material.

  For the anode, other light-transmitting oxide conductive materials such as indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO), and gallium-added zinc oxide (GZO) can be used. . Indium tin oxide containing ITO and silicon oxide (hereinafter referred to as ITSO) or indium oxide containing silicon oxide mixed with 2 to 20% zinc oxide (ZnO) may be used. In addition to the light-transmitting oxide conductive material as an anode, in addition to a single layer film made of, for example, one or more of TiN, ZrN, Ti, W, Ni, Pt, Cr, Ag, Al, etc., titanium nitride and A stack of a film containing aluminum as its main component, a three-layer structure of a titanium nitride film, a film containing aluminum as its main component, and a titanium nitride film can be used. However, when light is extracted from the anode side with a material other than the light-transmitting oxide conductive material, the light-transmitting oxide film is formed to have a film thickness that allows light to pass (preferably about 5 nm to 30 nm).

  In the opening 234 of the partition wall 233, the first electrode 206, the electroluminescent layer 235, and the second electrode 236 overlap with each other, so that the light-emitting element 238 is formed.

  Note that light extraction from the light-emitting element 238 may be performed from the first electrode 206 side, the second electrode 236 side, or both. Among the above three configurations, the material and film thickness of each of the anode and the cathode are selected in accordance with the target configuration. When light is extracted from the second electrode 236 side as in this embodiment mode, higher luminance can be obtained with lower power consumption than in the case of extracting light from the first electrode 206 side.

  Note that a passivation film 237 may be formed so as to cover the light-emitting element 238. As the passivation film 237, a film that hardly transmits a substance that causes deterioration of the light-emitting element such as moisture or oxygen compared to other insulating films is used. Typically, it is desirable to use, for example, a silicon nitride film formed by a DLC film, a carbon nitride film, an RF sputtering method, a CVD method, or the like. Further, for example, a film in which a carbon nitride film and silicon nitride are stacked, a film in which polystyrene is stacked, or the like may be used as the passivation film 237. In addition, the above-described film that hardly transmits a substance such as moisture or oxygen and a film that easily allows a substance such as moisture or oxygen to pass therethrough but has low internal stress may be stacked to be used as the passivation film 237. Is possible. In this embodiment mode, silicon nitride is used. In the case where silicon nitride is used for the passivation film 237, a rare gas element such as argon is preferably included in the reaction gas and mixed into the passivation film 237 in order to form a dense passivation film 237 at a low film formation temperature.

  FIG. 7 is a top view of the light-emitting device illustrated in FIG. FIG. 7 corresponds to a cross-sectional view taken along the line A-A ′ of FIG. Note that in FIG. 7, the electroluminescent layer 235, the second electrode 236, and the passivation film 237 are omitted in order to make the structure easier to understand. The wiring 215 functions as a signal line. The wiring 216 is connected to the gate electrode 203. The gate electrode 201 is electrically connected to the scanning line 240. The wiring 219 functions as a first power supply line. The second power supply line 241 is formed of the same conductive film as the wirings 215 to 219 and is connected to the gate electrode 203. A part of the first electrode 206 is exposed in the opening 234.

  Actually, when the state shown in FIG. 6B is completed, the protective film (laminate film, ultraviolet curable resin film, etc.) or cover material with high air tightness and less outgassing is used so as not to be exposed to the outside air. It is preferable to enclose (enclose).

  Note that although a process for forming a pixel portion is described in this embodiment mode, a scan line driver circuit can be formed over the same substrate as the pixel portion when a semi-amorphous semiconductor is used as the first semiconductor film. . Alternatively, a pixel portion may be formed using a TFT using an amorphous semiconductor, and a separately formed driver circuit may be attached to the substrate on which the pixel portion is formed.

  4 to 7, a lithography method is used for etching the gate insulating film 205 to expose a part of the gate electrode 203, or a resist formed by a droplet discharge method or a printing method is used as a mask. However, the present invention is not limited to this configuration. For example, the gate insulating film 205 may be etched using a wiring in contact with the second semiconductor film as a mask so that part of the gate electrode 203 is exposed. In this case, after the gate insulating film is etched, a conductive film that connects the exposed portion of the gate electrode 203 and the wiring used as a mask may be formed by a droplet discharge method. Further, for example, a pillar may be formed so as to overlap with a part of the gate electrode 203 before the gate insulating film 205 is formed. The pillar can be formed by dropping a solution containing a conductive material into a region where the pillar is to be formed, a plurality of times so that the droplets overlap. Since the thickness of the gate insulating film 205 is extremely thin at a portion overlapping the pillar, the wiring formed over the gate insulating film 205 and the pillar can be electrically connected.

  4A to 7B, the first semiconductor film and the second semiconductor film are patterned in separate steps; however, the light-emitting device of the present invention is not limited to this manufacturing method. Next, an example in which the first semiconductor film and the second semiconductor film are patterned using the same mask will be described with reference to FIGS.

  First, according to the manufacturing method described above, the manufacturing process is similarly performed up to the state shown in FIG. Next, as shown in FIG. 8A, before the first semiconductor film 207 is patterned, a second semiconductor film 250 is formed. In the case of forming the third semiconductor film used as the LDD region, the first semiconductor film 207 is formed, then the third semiconductor film is formed, and then the second semiconductor film 250 is formed. Next, as shown in FIG. 8B, the first semiconductor film 207 and the second semiconductor film 250 are patterned using a resist 251 formed by a droplet discharge method or a printing method as a mask. In FIG. 8B, 252 and 253 correspond to the first semiconductor film after patterning, and 254 and 255 correspond to the second semiconductor film after patterning.

  Next, as shown in FIG. 8C, wirings 256 to 260 are formed by a droplet discharge method or a printing method. Then, by using the wirings 256 to 260 as a mask and further patterning the second semiconductor films 254 and 255, second semiconductor films 261 to 265 functioning as a source region or a drain region are formed. After that, in the same manner as the manufacturing method shown in FIGS. 4 to 7, the partition, the electroluminescent layer, and the second electrode can be formed.

  When the manufacturing method illustrated in FIGS. 8A to 8C is used, the first electrode 206 and the wiring 258 are in direct contact with each other, so that the contact resistance in the connection portion can be reduced.

  In the manufacturing method illustrated in FIGS. 4 to 7 and the manufacturing method illustrated in FIG. 8, the first electrode is formed before the second semiconductor film and the wiring in contact with the second semiconductor film are formed. However, the present invention is not limited to this configuration. 9A, in the manufacturing method illustrated in FIGS. 4 to 7, the first electrode is formed after the second semiconductor film and the wiring in contact with the second semiconductor film are formed. FIG. 3 shows a cross-sectional view of a pixel. However, FIG. 9A shows a driving TFT 630 and a current control TFT 631.

  In FIG. 9A, reference numerals 601 to 603 correspond to a second semiconductor film functioning as a source region or a drain region. A wiring 604 is in contact with the second semiconductor film 601 so as to be in contact with the second semiconductor film 602. A wiring 605 is formed so as to be in contact with the top, and a wiring 606 is formed so as to be in contact with the second semiconductor film 603. In FIG. 9A, the first semiconductor film 607 and the second semiconductor films 601 to 603 are formed by patterning using different masks as in the case shown in FIGS. However, the present invention is not limited to this configuration, and patterning may be performed using the same mask as in the case of FIG. In FIG. 9A, a first electrode 608 is formed so as to be in contact with the wiring 604. As shown in FIG. 9A, after the second semiconductor films 601 to 603 and the wirings 604 to 606 in contact with the second semiconductor films 601 to 603 are formed, the first electrode 608 is formed. Accordingly, even when dry etching is used for patterning the second semiconductor films 601 to 603, the surface of the first electrode 608 can be prevented from being roughened.

  In FIGS. 4 to 7, 8 and 9A, the first electrode is formed on the gate insulating film, but the present invention is not limited to this structure. FIG. 9B is a cross-sectional view of a pixel in the case where an interlayer insulating film is formed so as to cover the TFT and the first electrode is formed over the interlayer insulating film. Note that FIG. 9B illustrates a driving TFT 640 and a current control TFT 641. In FIG. 9B, the driving TFT 640, the current control TFT 641, and the wirings 642 to 644 connected to the source region or the drain region of the driving TFT 640 and the current control TFT 641 are covered with an interlayer insulating film 645. A first electrode 646 is formed on the interlayer insulating film 645. The interlayer insulating film 645 can be formed using an organic resin film, an inorganic insulating film, or a siloxane-based insulating film. A material called a low dielectric constant material (low-k material) may be used for the interlayer insulating film 645. The first electrode 646 and the wiring 611 are electrically connected through a pillar 647 formed in the contact hole of the interlayer insulating film 645.

  In FIG. 9B, the pillar 647 is formed by a droplet discharge method before the interlayer insulating film 645 is formed. Specifically, a pillar 647 is formed by dropping a solution containing a conductive material at the same point and overlapping the droplets. As a conductive material used for the pillar 647, a light-transmitting oxide conductive material typified by ITO or ITSO can be used. Then, after the pillar 647 is formed, an interlayer insulating film 645 is formed by a coating method such as a spin coat method, and then the surface of the interlayer insulating film 645 is etched to expose the pillar 647. Then, a first electrode 646 is formed over the interlayer insulating film 645 so as to be in contact with the pillar 647. Note that the surface of the interlayer insulating film 645 is preferably planarized so that unevenness is not formed on the surface of the first electrode 646. Therefore, in the case of forming the interlayer insulating film 645 by using a droplet discharge method, after the droplet is discharged, the surface may be flattened by blowing a gas and then fired.

In FIG. 9B, the pillar 647 is formed before the interlayer insulating film 645 is formed; however, the pillar 647 may be formed after the interlayer insulating film 645 is formed. In this case, a contact hole is formed in the interlayer insulating film 645, and a pillar 647 is formed by dropping a solution containing a conductive material into the contact hole by a droplet discharge method. The contact hole can be formed by either dry etching or wet etching. Further, before forming the interlayer insulating film, an organic material having liquid repellency may be applied to a region where the contact hole is formed by a droplet discharge method or a printing method. In this case, the contact hole can be formed without etching by removing the liquid-repellent organic material after forming the interlayer insulating film. As an organic material having liquid repellency, polyvinyl alcohol (PVA), fluoroalkylsilane (FAS), or the like can be used. The organic material having liquid repellency can be removed by washing with water or dry etching using CF ₄ , O ₂ or the like.

  The interlayer insulating film may be formed using a droplet discharge method. FIG. 9C is a cross-sectional view of a pixel in the case where an interlayer insulating film is formed using a droplet discharge method. Note that FIG. 9C illustrates a driving TFT 650 and a current control TFT 651. In FIG. 9C, a driving TFT 650 and a current control TFT 651 are covered with a first interlayer insulating film 653, and the first interlayer insulating film 653 is formed by a droplet discharge method. A wiring 652 connected to either the source region or the drain region of the driving TFT 650 does not completely overlap with the first interlayer insulating film 653 but is partly exposed. The first interlayer insulating film 655 is formed using a droplet discharge method in the same manner as the first interlayer insulating film 653, and the first electrode 654 is formed so as to cover the first interlayer insulating film 653. Is formed. A part of the wiring 652 that is exposed is in contact with the first electrode 654, and a second interlayer insulating film 656 is further formed so as to cover the contacted part.

  The second interlayer insulating film 656 has an opening in a region overlapping with the first interlayer insulating film 655, and is formed over the first electrode 654 and the second interlayer insulating film 656 in the opening. The electroluminescent layer 657 and the second electrode 658 overlap with each other to form a light emitting element.

4 to 9, the protective film is formed between the first semiconductor film and the second semiconductor film of the TFT; however, the present invention is not limited to this structure, and FIG. In the case of FIG. 9, the protective film is not necessarily formed. FIG. 10A shows a cross-sectional view of a pixel in the case where a protective film is not formed. However, FIG. 10A shows a driving TFT 701 and a current control TFT 702. A driving TFT 701 and a current control TFT 702 illustrated in FIG. 10A include gate electrodes 703 and 704 formed over a substrate 700, a gate insulating film 705 formed so as to cover the gate electrodes 703 and 704, A first semiconductor film 706 formed over the gate insulating film 705 so as to overlap with the gate electrodes 703 and 704 and second semiconductor films 707 to 709 in contact with the first semiconductor film 706 are provided. When the second semiconductor films 707 to 709 are formed by etching, a fluoride gas such as SF ₆ , NF ₃ , or CF ₄ is used as an etching gas. In this etching, since the etching selectivity with respect to the first semiconductor film 706 cannot be obtained, the processing time is appropriately adjusted. By this etching, the first semiconductor film 706 is partially exposed.

  In the case where the first semiconductor film 706 and the second semiconductor films 707 to 709 are patterned using the same mask without forming a protective film as in FIG. 10A, the gate insulating film 705, The semiconductor film 706 and the second semiconductor films 707 to 709 can be formed successively without being exposed to the air. In other words, each stacked interface can be formed without being contaminated by atmospheric components or contaminants floating in the atmosphere, so that variations in TFT characteristics can be reduced.

  In FIGS. 4 to 9 and 10A, the gate electrode is formed on the substrate side of the first semiconductor film; however, the present invention is not limited to this structure. FIG. 10B is a cross-sectional view of the pixel in the case where the first semiconductor film is formed on the substrate side with respect to the gate electrode. However, FIG. 10B shows a driving TFT 711 and a current control TFT 712. 10B, wirings 712 to 714 are formed over a substrate 710, and second semiconductor films 715 to 717 are formed so as to be in contact with the wirings 712 to 714, whereby the second semiconductor A first semiconductor film 718 is formed so as to be in contact with the films 715 to 717. A gate insulating film 719 is formed over the first semiconductor film 718, and gate electrodes 720 and 721 are formed over the gate insulating film 719 so as to overlap with the first semiconductor film 718.

  Note that each of the TFTs shown in FIGS. 4 to 7, 8, 6, and 10 uses a second semiconductor film that functions as a source region or a drain region. It does not necessarily have to be formed. In this case, the wiring is directly connected to the first semiconductor film, and the wiring functions as a source region or a drain region. In particular, in the TFT illustrated in FIG. 10B, when the second semiconductor film is not used, a mask used for patterning for forming the second semiconductor films 715 to 717 is not necessary. Can be reduced.

  Further, in the light emitting devices shown in FIGS. 4 to 7, 8, 6, and 10, an example in which one first semiconductor film is shared by the driving TFT and the current control transistor is shown. However, the present invention is not limited to this configuration. The driving TFT and the current control transistor may use independent first semiconductor films.

  Note that in the light-emitting devices shown in FIGS. 4 to 7, 8, 6, and 10, the driving TFT, the current control TFT, and the switching TFT may have a multi-gate structure. The multi-gate structure means a configuration in which a plurality of TFTs connected in series and connected to gate electrodes share a first semiconductor film. With the multi-gate structure, the off-current of the TFT can be reduced.

  In this embodiment, a structure of a TFT formed in a pixel in the light emitting device of the present invention will be described.

  FIG. 11 is a cross-sectional view of the pixel of this example. In FIG. 11, 1400 corresponds to a driving TFT, 1401 corresponds to a current control TFT, 1402 corresponds to a switching TFT, and 1403 corresponds to a light emitting element. The driving TFT 1400, the current control TFT 1401, the switching TFT 1402, and the light emitting element 1404 are sealed together with the filler 1408 between the substrate 1406 and the cover material 1407 by a sealant 1405.

  The driving TFT 1400 is formed over the gate electrode 1409, the gate insulating film 1410 formed over the gate electrode 1409, the first semiconductor film 1411 formed over the gate insulating film 1410, and the first semiconductor film 1411. The second semiconductor films 1412 and 1413 are formed. The current control TFT 1401 includes a gate electrode 1420, a gate insulating film 1410 formed over the gate electrode 1420, a first semiconductor film 1421 formed over the gate insulating film 1410, and a first semiconductor film 1421. The second semiconductor films 1413 and 1422 are formed. Reference numerals 1414, 1415, and 1423 correspond to wirings connected to the second semiconductor films 1412, 1413, and 1422, respectively. The wiring 1414 is connected to the first electrode 1424 of the light emitting element 1404.

  Note that FIG. 14 shows a structure in which the driving TFT and the current control TFT each have the independent first semiconductor film in the light-emitting device shown in FIG. 6B. It is not limited to. For example, in the light-emitting device illustrated in FIGS. 8 to 10, the driving TFT and the current control TFT may each have a separate first semiconductor film.

  In this example, a mode different from that in FIG. 1 of a pixel included in the light-emitting device of the present invention will be described.

  A pixel illustrated in FIG. 12A includes a light-emitting element 801, a switching TFT 802, a driving TFT 803, a current control TFT 804, and a TFT (erasing TFT) 805 for erasing the potential of a written video signal. And have. In addition to the above elements, a capacitor 806 may be provided in the pixel. Further, an enhancement type TFT or a depletion type TFT may be used as the driving TFT 803.

  The gate electrode of the switching TFT 802 is connected to the first scanning line Gaj (j = 1 to y). One of the source region and the drain region of the switching TFT 802 is connected to the signal line Si (i = 1 to x), and the other is connected to the gate electrode of the current control TFT 804. The gate electrode of the erasing TFT 805 is connected to the second scanning line Gbj (j = 1 to y), and one of the source region and the drain region is the first power supply line Vi (i = 1 to x). The other is connected to the gate electrode of the current control TFT 804. The gate electrode of the driving TFT 803 is connected to the second power supply line Wi (i = 1 to x). In the driving TFT 803 and the current control TFT 804, the current supplied to the light emitting element 801 is supplied to the first power supply line Vi (i = 1 to x) as the drain current of the driving TFT 803 and the current control TFT 804. Thus, the first power supply line Vi (i = 1 to x) and the light emitting element 801 are connected. In this embodiment, the source region of the current control TFT 804 is connected to the first power supply line Vi (i = 1 to x), and the drain region of the driving TFT 803 is connected to the first electrode of the light emitting element 801. Note that the source region of the driving TFT 803 may be connected to the first power supply line Vi (i = 1 to x), and the drain region of the current control TFT 804 may be connected to the first electrode of the light emitting element 801. One of two electrodes of the capacitor 806 is connected to the first power supply line Vi (i = 1 to x), and the other is connected to the gate electrode of the current control TFT 804.

  The light-emitting element 801 includes an anode, a cathode, and an electroluminescent layer provided between the anode and the cathode. In the case where the driving TFT 803 and the current control TFT 804 are n-type as shown in FIG. 12A, it is preferable that the first electrode be a cathode and the second electrode be an anode.

  The operation of the pixel illustrated in FIG. 12A can be described by being divided into a writing period, a holding period, and an erasing period. The operations of the switching TFT 802, the driving TFT 803, and the current control TFT 804 in the writing period and the holding period are the same as those in FIG.

  In the erasing period, the second scanning line Gbj (j = 1 to y) is selected and the erasing TFT 805 is turned on, and the potentials of the power supply lines V1 to Vx pass through the erasing TFT 805 and the gate electrode of the current control TFT 804. Given to. Accordingly, since the current control TFT 804 is turned off, a state where no current is forcibly supplied to the light emitting element 801 can be created.

  FIG. 12B shows another structure of the pixel in this embodiment. A pixel illustrated in FIG. 12B includes a light-emitting element 811, a switching TFT 812, a driving TFT 813, and a current control TFT 814. Further, as in this embodiment, a capacitor 814 for holding the potential of the video signal may be provided in the pixel. An enhancement type TFT or a depletion type TFT may be used as the driving TFT 813. The current control TFT 814 is operated in a linear region.

  The gate electrode of the switching TFT 812 is connected to the scanning line Gj (j = 1 to y). One of the source region and the drain region of the switching TFT 812 is connected to the signal line Si (i = 1 to x), and the other is connected to the gate electrode of the current control TFT 814. The gate electrode of the driving TFT 813 is connected to the power supply line Vi (i = 1 to y). The driving TFT 813 and the current control TFT 814 are supplied so that the current supplied to the light emitting element 811 is supplied to the power supply line Vi (i = 1 to x) as the drain current of the driving TFT 813 and the current control TFT 814. The power source line Vi (i = 1 to x) and the light emitting element 811 are connected. In this embodiment, the source region of the current control TFT 814 is connected to the power supply line Vi (i = 1 to x), and the drain region of the driving TFT 813 is connected to the first electrode of the light emitting element 811. In this embodiment, the source region of the driving TFT 813 may be connected to the power supply line Vi (i = 1 to x), and the drain region of the current control TFT 814 may be connected to the first electrode of the light emitting element 811. . One of the two electrodes of the capacitor 814 is connected to the power supply line Vi (i = 1 to x), and the other is connected to the gate electrode of the current control TFT 814.

  The light-emitting element 811 includes an anode, a cathode, and an electroluminescent layer provided between the anode and the cathode. In the case where the driving TFT 813 and the current control TFT 814 are n-type as shown in FIG. 12B, it is preferable that the first electrode be a cathode and the second electrode be an anode.

  Next, FIG. 12C shows a circuit diagram of a pixel provided with a TFT (erase TFT) 816 for forcibly turning off the current control TFT 814 in the pixel shown in FIG. 12B. Note that in FIG. 12C, elements that have already been described with reference to FIG. The erasing TFT 816 has a gate electrode connected to the second scanning line Gb, and one of the source region and the drain region is connected to the gate electrode of the current control TFT 814 and the other is connected to the power supply line Vi. The erasing TFT 816 may be either n-type or p-type.

  FIG. 12D illustrates another structure of the pixel in this embodiment. The pixel illustrated in FIG. 12D includes a light-emitting element 821, a switching TFT 822, a driving TFT 823, and a current control TFT 824. Further, as in this embodiment, a capacitor 825 for holding the potential of the video signal may be provided in the pixel. The driving TFT 823 may be operated in a saturation region or may be operated in a linear region. The switching TFT 822 and the current control TFT 824 are operated in a linear region. As the driving TFT 823, an enhancement type TFT or a depletion type TFT may be used.

  A gate electrode of the switching TFT 822 is connected to the first scanning line Gaj (j = 1 to y). One of the source region and the drain region of the switching TFT 822 is connected to the signal line Si (i = 1 to x), and the other is connected to the gate electrode of the current control TFT 824. The gate electrode of the driving TFT 823 is connected to the second scanning line Gbj (j = 1 to y). The driving TFT 823 and the current control TFT 824 are supplied so that the current supplied from the power supply line Vi (i = 1 to x) is supplied to the light emitting element 821 as the drain current of the driving TFT 823 and the current control TFT 824. The power source line Vi (i = 1 to x) and the light emitting element 821 are connected. In this embodiment, the source region of the current control TFT 824 is connected to the power supply line Vi (i = 1 to x), and the drain region of the driving TFT 823 is connected to the first electrode of the light emitting element 821. In this embodiment, the source region of the driving TFT 823 may be connected to the power supply line Vi (i = 1 to x), and the drain region of the current control TFT 824 may be connected to the first electrode of the light emitting element 821. . One of the two electrodes of the capacitor 825 is connected to the power supply line Vi (i = 1 to x), and the other is connected to the gate electrode of the current control TFT 824.

  The light-emitting element 821 includes an anode, a cathode, and an electroluminescent layer provided between the anode and the cathode. When the driving TFT 823 and the current control TFT 824 are n-type as shown in FIG. 12D, it is preferable that the first electrode be a cathode and the second electrode be an anode.

  Next, FIG. 12E shows a circuit diagram of a pixel provided with a TFT (erase TFT) 826 for forcibly turning off the current control TFT 824 in the pixel shown in FIG. Note that in FIG. 12E, elements already described in FIG. 12D are denoted by the same reference numerals. The erasing TFT 826 has a gate electrode connected to the second scanning line Gbj, and one of the source region and the drain region is connected to the gate electrode of the current control TFT 824 and the other is connected to the power supply line Vi. The erasing TFT 826 may be either n-type or p-type.

  Note that the layout of the first power supply line Vi is not limited to the configuration shown in FIG. For example, as shown in FIG. 13A, the gate electrode of the driving TFT 103 is electrically connected by a plurality of wirings between pixels sharing the signal line Si, and the plurality of wirings and the driving TFT 103 are connected. The gate electrode may function as the first power supply line Vi. Note that in FIG. 13A, the elements already described in FIG. 1 are denoted by the same reference numerals. The circuit symbol indicating the driving TFT 103 in FIG. 13A represents a TFT in which contact regions are provided at two different points of the gate electrode, and the connection relationship is different from a normal one, and thus is particularly illustrated in this manner.

  Similarly, the layout of the first power supply line Vi is not limited to the structure illustrated in FIG. For example, as shown in FIG. 13B, the gate electrode of the driving TFT 803 is electrically connected by a plurality of wirings between pixels sharing the signal line Si, and the plurality of wirings and the driving TFT 803 are connected. The gate electrode may function as the first power supply line Vi. Note that in FIG. 13B, elements already described in FIG. 12A are denoted by the same reference numerals. The circuit symbol indicating the driving TFT 803 in FIG. 13B represents a TFT in which contact regions are provided at two different points of the gate electrode, and the connection relationship is different from a normal one, and thus is particularly illustrated in this manner.

  Next, FIG. 12F is a circuit diagram of a pixel in which a TFT (reverse bias TFT) 106 for applying a reverse bias voltage to the light emitting element 101 is provided in the pixel shown in FIG. Note that in FIG. 12F, the elements already described in FIG. 1 are denoted by the same reference numerals. In the reverse bias TFT 106, either the source region or the drain region is connected to the first electrode of the light emitting element 101 and the other is connected to the first power supply line Vi. Note that in FIG. 12F, either the source region or the drain region is connected to the first power supply line Vi; however, the present invention is not limited to this structure. Either one of them may be connected to the second power supply line Wi or may be connected to another wiring prepared separately. The reverse bias TFT 106 has a gate electrode connected to the first power supply line Vi. In FIG. 12F, the gate electrode of the reverse bias TFT 106 is connected to the first power supply line Vi, but the present invention is not limited to this structure. The gate electrode of the reverse bias TFT 106 may be connected to the second power supply line Wi, or may be connected to another wiring prepared separately. However, the reverse bias TFT 106 is configured such that the potential of the gate electrode is the same as or lower than the potential of the source region when a forward bias voltage is applied. The reverse bias TFT 106 may be either n-type or p-type.

  By providing the reverse bias TFT 106, a reverse bias voltage can be reliably applied to the light emitting element 101 regardless of the operation of the driving TFT 103 and the current control TFT 104. Further, by applying a reverse bias voltage to the light-emitting element 101, the reliability of the light-emitting element 101 can be improved. In addition, since dust or the like that causes a short circuit can be burned out between the first electrode and the second electrode, the yield can be increased.

  Next, the structure of the light-emitting element will be described with reference to FIG. The element structure of the light emitting element in the present invention is schematically shown in FIG.

  14 includes a first electrode 501 formed over a substrate 500, an electroluminescent layer 502 formed over the first electrode 501, and a second electrode formed over the electroluminescent layer 502. The light-emitting element illustrated in FIG. An electrode 503. Note that actually, various layers, semiconductor elements, and the like are provided between the substrate 500 and the first electrode 501.

  In this embodiment, the case where the first electrode 501 is a cathode and the second electrode is an anode will be described. However, the first electrode 501 may be an anode and the second electrode may be a cathode. Since specific materials used for the anode and the cathode have already been described, a specific structure of the electroluminescent layer 502 will be described here.

  The electroluminescent layer 502 is composed of one or more layers. When composed of a plurality of layers, these layers can be classified into a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and the like from the viewpoint of carrier transport characteristics. Note that the boundaries between the layers are not necessarily clear, and there are cases where the materials constituting the layers are partially mixed and the interface is unclear. For each layer, an organic material or an inorganic material can be used. As the organic material, any of a high molecular weight material, a medium molecular weight material, and a low molecular weight material can be used. The medium molecular weight material corresponds to a low polymer having a number of repeating structural units (degree of polymerization) of about 2 to 20.

  The distinction between a hole injection layer and a hole transport layer is not necessarily strict, and these are the same in the sense that hole transportability (hole mobility) is a particularly important characteristic. For convenience, the hole injection layer is a layer in contact with the anode, and the layer in contact with the hole injection layer is referred to as a hole transport layer to be distinguished. The same applies to the electron transport layer and the electron injection layer. The layer in contact with the cathode is called an electron injection layer, and the layer in contact with the electron injection layer is called an electron transport layer. The light emitting layer may also serve as an electron transport layer, and is also referred to as a light emitting electron transport layer. FIG. 14 illustrates the case where the electroluminescent layer 502 includes the first to fifth layers 504 to 508. The first to fifth layers 504 to 508 are sequentially stacked from the first electrode 501 toward the second electrode 503.

Since the first layer 504 functions as an electron injection layer, it is preferable to use a material having a high electron injection property. Specifically, an ultra-thin film of an insulator such as an alkali metal halide such as LiF or CsF, an alkaline earth halide such as CaF ₂ , or an alkali metal oxide such as Li ₂ O is often used. In addition, alkali metal complexes such as lithium acetylacetonate (abbreviation: Li (acac) and 8-quinolinolato-lithium (abbreviation: Liq) are also effective. Molybdenum oxide (MoOx), vanadium oxide (VOx), A metal oxide such as ruthenium oxide (RuOx) or tungsten oxide (WOx) or a benzoxazole derivative, and one or more materials of alkali metal, alkaline earth metal, or transition metal may be included. Further, titanium oxide may be used.

Since the second layer 505 functions as an electron transporting layer, it is preferable to use a material having a high electron transporting property. Specifically, a metal complex having a quinoline skeleton or a benzoquinoline skeleton represented by Alq ₃ or a mixed ligand complex thereof can be used. Specifically, metal complexes such as Alq ₃ , Almq ₃ , BeBq ₂ , BAlq, Zn (BOX) ₂ , and Zn (BTZ) ₂ can be given. In addition to metal complexes, 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (PBD), 1,3-bis [5- (p Oxadiazole derivatives such as -tert-butylphenyl) -1,3,4-oxadiazol-2-yl] benzene (OXD-7), 3- (4-tert-butylphenyl) -4-phenyl-5 -(4-biphenylyl) -1,2,4-triazole (TAZ), 3- (4-tert-butylphenyl) -4- (4-ethylphenyl) -5- (4-biphenylyl) -1,2, Triazole derivatives such as 4-triazole (p-EtTAZ), imidazole derivatives such as TPBI, phenanthroyl such as bathophenanthroline (BPhen) and bathocuproin (BCP) It can be used derivatives.

Since the third layer 506 functions as a light emitting layer, it is preferable to use a material having a large ionization potential and a large band gap. Specifically, for example, tris (8-quinolinolato) aluminum (Alq ₃ ), tris (4-methyl-8-quinolinolato) aluminum (Almq ₃ ), bis (10-hydroxybenzo [η] -quinolinato) beryllium (BeBq) ₂ ), bis (2-methyl-8-quinolinolato)-(4-hydroxy-biphenylyl) -aluminum (BAlq), bis [2- (2-hydroxyphenyl) -benzoxazolate] zinc (Zn (BOX) ₂ ), Bis [2- (2-hydroxyphenyl) -benzothiazolate] zinc (Zn (BTZ) ₂ ), and the like. Various fluorescent dyes (coumarin derivatives, quinacridone derivatives, rubrene, 4,4-dicyanomethylene, 1-pyrone derivatives, stilbene derivatives, various condensed aromatic compounds, etc.) can also be used. Phosphorescent materials such as platinum octaethylporphyrin complex, tris (phenylpyridine) iridium complex, tris (benzylideneacetonato) phenanthrene europium complex can also be used.

  As the host material used for the third layer 506, a hole transport material or an electron transport material typified by the above example can be used. Alternatively, a bipolar material such as 4,4′-N, N′-dicarbazolylbiphenyl (abbreviation: CBP) can be used.

  Since the fourth layer 507 functions as a hole transport layer, it is preferable to use a known material having high hole transportability and low crystallinity. Specifically, an aromatic amine-based compound (that is, a compound having a benzene ring-nitrogen bond) is suitable, for example, 4,4-bis [N- (3-methylphenyl) -N-phenylamino]. Biphenyl (TPD) and its derivative 4,4′-bis [N- (1-naphthyl) -N-phenyl-amino] biphenyl (α-NPD) are examples. Starburst type aromatic amine compounds such as 4,4 ′, 4 ″ -tris (N, N-diphenylamino) triphenylamine (TDATA) and MTDATA can also be used. Alternatively, 4,4 ′, 4 ″ -tris (N-carbazolyl) triphenylamine (abbreviation: TCTA) may be used. As the polymer material, poly (vinyl carbazole) or the like exhibiting good hole transportability can be used.

Since the fifth layer 508 functions as a hole injection layer, it is desirable to use a material having a hole transporting property, a relatively low ionization potential, and a high hole injecting property. Broadly divided into metal oxides, low-molecular organic compounds, and high-molecular organic compounds. As the metal oxide, for example, vanadium oxide, molybdenum oxide, ruthenium oxide, aluminum oxide, or the like can be used. If low molecular weight organic compound, for example, starburst amine typified by m-MTDATA, copper phthalocyanine (abbreviation: Cu-Pc) in the metal phthalocyanine represented, phthalocyanine (abbreviation: H ₂ -Pc), _2, A 3-dioxyethylenethiophene derivative or the like can be used. A film in which a low molecular organic compound and the metal oxide are co-evaporated may be used. As a high molecular organic compound, for example, a polymer such as polyaniline (abbreviation: PAni), polyvinyl carbazole (abbreviation: PVK), or a polythiophene derivative can be used. Polyethylene dioxythiophene (abbreviation: PEDOT), which is one of polythiophene derivatives, doped with polystyrene sulfonic acid (abbreviation: PSS) may be used. Further, a benzoxazole derivative and any one or more materials of TCQn, FeCl ₃ , C _60, or F ₄ TCNQ may be used in combination.

  In the light-emitting element having the above structure, light is applied from the third layer 506 by applying a voltage between the first electrode 501 and the second electrode 503 and supplying a forward bias current to the electroluminescent layer 502. And the light can be extracted from the first electrode 501 side or the second electrode 503 side. Note that the electroluminescent layer 502 is not necessarily required to have all of the first to fifth layers. In the present invention, it is only necessary to include at least the third layer 506 functioning as a light emitting layer. Further, light emission is not necessarily obtained only from the third layer 506, and light emission may be obtained from layers other than the third layer 506 depending on the combination of materials used for the first to fifth layers. Further, a hole blocking layer may be provided between the third layer 506 and the fourth layer 507.

  Note that depending on the color, the phosphorescent material can have a lower driving voltage and higher reliability than the fluorescent material. Therefore, when full-color display is performed using light-emitting elements corresponding to the three primary colors, a combination of a light-emitting element using a fluorescent material and a light-emitting element using a phosphorescent material can reduce the deterioration of the light-emitting element of each color. You may make it arrange | equalize a degree.

  FIG. 14 shows the case where the first electrode 501 is a cathode and the second electrode 503 is an anode. However, when the first electrode 501 is an anode and the second electrode 503 is a cathode, The fifth layers 504 to 508 are stacked in reverse. Specifically, a fifth layer 508, a fourth layer 507, a third layer 506, a second layer 505, and a first layer 504 are sequentially stacked over the first electrode 501.

  Note that a material that is difficult to be etched is used for the layer closest to the second electrode 503 in the electroluminescent layer 502 (the fifth layer 508 in this embodiment), whereby the second electrode 503 is formed over the electroluminescent layer 502. When sputtering is performed by sputtering, sputtering damage given to the layer closest to the second electrode 503 can be reduced. As the material that is difficult to etch, for example, a metal oxide such as molybdenum oxide (MoOx), vanadium oxide (VOx), ruthenium oxide (RuOx), or tungsten oxide (WOx), or a benzoxazole derivative can be used. . These are preferably formed by vapor deposition.

For example, in the case where the first electrode is a cathode and the second electrode is an anode, the above-described material that is not easily etched is used as the layer having hole injecting property or hole transporting property that is closest to the anode among the electroluminescent layers. Specifically, when a benzoxazole derivative is used, a layer including the benzoxazole derivative and any one or more materials of TCQn, FeCl ₃ , C _60, or F ₄ TCNQ is set closest to the anode. Form.

  In addition, for example, when the first electrode is an anode and the second electrode is a cathode, the above-described material that is not etched easily is used as the layer having the electron injecting property or the electron transporting property closest to the cathode among the electroluminescent layers. . Specifically, in the case of using molybdenum oxide, a layer containing the molybdenum oxide and one or more materials of alkali metal, alkaline earth metal, or transition metal is closest to the cathode. Form. In the case of using a benzoxazole derivative, a layer including the benzoxazole derivative and one or more materials of an alkali metal, an alkaline earth metal, or a transition metal is formed so as to be closest to the cathode. Note that a metal oxide and a benzoxazole derivative may be used together.

  With the above structure, a transparent conductive film formed by sputtering as the second electrode, for example, indium tin oxide (ITO), indium tin oxide containing silicon (ITSO), or 2-20% zinc oxide in indium oxide. Even when IZO (Indium Zinc Oxide) mixed with (ZnO) or the like is used, sputter damage to a layer containing an organic substance included in the electroluminescent layer can be suppressed, and selection of a material for forming the second electrode Sex spreads.

  In this embodiment, an embodiment of a method for connecting a light emitting device and an IC will be described.

  FIGS. 15A and 15B show how a chip-like IC (IC chip) is mounted on an element substrate over which a pixel portion is formed. In FIG. 15A, a pixel portion 6002 and a scan line driver circuit 6003 are formed over a substrate 6001. A signal line driver circuit formed in the IC chip 6004 is mounted on the substrate 6001. Specifically, a signal line driver circuit formed in the IC chip 6004 is attached to the substrate 6001 and electrically connected to the pixel portion 6002. Reference numeral 6005 denotes an FPC, and a power supply potential, various signals, and the like are supplied to the pixel portion 6002, the scan line driver circuit 6003, and the signal line driver circuit formed in the IC chip 6004 through the FPC 6005, respectively.

  In FIG. 15B, a pixel portion 6102 and a scan line driver circuit 6103 are formed over a substrate 6101. The signal line driver circuit formed on the IC chip 6104 is further mounted on the FPC 6105 mounted on the substrate 6101. A power supply potential, various signals, and the like are supplied to the pixel portion 6102, the scan line driver circuit 6103, and the signal line driver circuit formed in the IC chip 6104 through the FPC 6105.

  The IC chip mounting method is not particularly limited, and a known COG method, wire bonding method, TAB method, or the like can be used. Further, the position where the IC chip is mounted is not limited to the position shown in FIG. 15 as long as electrical connection is possible. FIG. 15 shows an example in which only the signal line driver circuit is formed with an IC chip. However, the scanning line driver circuit may be formed with an IC chip, and a controller, a CPU, a memory, and the like are formed with an IC chip. You may make it implement. Further, instead of forming the entire signal line driver circuit and the scanning line driver circuit with an IC chip, only a part of the circuits constituting each driver circuit may be formed with an IC chip.

  Note that by separately forming and mounting an integrated circuit such as a driver circuit using an IC chip, the yield can be increased as compared with the case where all the circuits are formed over the same substrate as the pixel portion. The process can be easily optimized according to the characteristics.

  Although not shown in FIG. 15, a protective circuit may be provided over the substrate over which the pixel portion is formed. Since the discharge path can be secured by the protection circuit, the semiconductor element formed on the substrate is deteriorated or broken down due to noise of the signal and the power supply voltage or charge charged to the insulating film for some reason. Can be prevented. Specifically, in the case of FIG. 15A, a protective circuit can be connected to a wiring that electrically connects the FPC 6005 and the pixel portion 6002. Further, wiring that electrically connects the FPC 6005 and the signal line driver circuit 6004, wiring that electrically connects the FPC 6005 and the scanning line driver circuit 6003, and the signal line driver circuit 6004 and the pixel portion 6002 are provided. A protection circuit can be connected to each of the wiring (signal line) electrically connected and the wiring (scanning line) electrically connecting the scan line driver circuit 6003 and the pixel portion 6002.

  Next, the structure of the drive circuit used for the light emitting device of the present invention will be described. FIG. 16 shows a block diagram of a light emitting device of the present invention. In FIG. 16, the signal line driver circuit 901 includes a shift register 902, a latch A 903, and a latch B 904. The scan line driver circuit 910 includes a shift register 911 and a buffer 912. 900 corresponds to a pixel portion. Note that in the case of a light-emitting device having two scanning lines (a first scanning line and a second scanning line), two scanning line driver circuits may be provided.

  A clock signal (CLK) and a start pulse signal (SP) are input to the shift register 902. When the clock signal (CLK) and the start pulse signal (SP) are input, a timing signal is generated in the shift register 902 and sequentially input to the first-stage latch A 903. When a timing signal is input to the latch A903, video signals are sequentially written and held in the latch A903 in synchronization with the timing signal. In FIG. 16, it is assumed that video signals are sequentially written in the latch A 903, but the present invention is not limited to this configuration. A plurality of stages of latches A903 may be divided into several groups, and so-called divided driving may be performed in which video signals are input in parallel for each group. Note that the number of groups at this time is called the number of divisions. For example, when the latches are divided into groups for every four stages, it is said that the driving is divided into four.

  The time until video signal writing to all the latches included in the latch A 903 is completed is called a line period. Actually, the line period may include a period in which a horizontal blanking period is added to the line period.

  When one line period ends, a latch signal (Latch Signal) is supplied to the second-stage latch B904, and the video signals held in the latch A903 are simultaneously written to the latch B904 in synchronization with the latch signal. Retained. In the latch A 903 that has finished sending the video signal to the latch B 904, the next video signal is sequentially written in synchronization with the timing signal from the shift register 902 again. During the second line of one line, the video signal written and held in the latch B 904 is input to the signal line.

  Next, the configuration of the scan line driver circuit 910 will be described. The scan line driver circuit 910 includes a shift register 911 and a buffer 912. In some cases, a level shifter may be provided. In the scan line driver circuit 910, a clock signal (CLK) and a start pulse signal (SP) are input to the shift register 911, whereby a selection signal is generated. The generated selection signal is buffered and amplified in the buffer 912 and supplied to the corresponding scanning line. A gate of a switching TFT or an erasing TFT of pixels for one line is connected to the scanning line. Since the TFTs of pixels for one line must be turned on all at once, a buffer 912 that can flow a large current is used.

  Note that the structure illustrated in FIG. 16 is merely an embodiment of the light-emitting device of the present invention, and the structures of the signal line driver circuit and the scan line driver circuit are not limited thereto. For example, the signal line driver circuit and the scan line driver circuit used in the present invention may use another circuit capable of selecting a signal line such as a decoder circuit instead of the shift register.

  In this example, the appearance of a panel corresponding to one embodiment of the light-emitting device of the present invention will be described with reference to FIG. FIG. 17 is a top view of a panel in which a TFT and a light-emitting element formed over an element substrate are sealed with a sealing material between a cover material, and FIG. 17B is a plan view of FIG. This corresponds to a cross-sectional view taken along the line AA ′.

  A sealant 4005 is provided so as to surround the pixel portion 4002 provided over the element substrate 4001 and the scan line driver circuit 4004. A cover member 4006 is provided over the pixel portion 4002 and the scan line driver circuit 4004. Therefore, the pixel portion 4002 and the scan line driver circuit 4004 are sealed together with the filler 4007 by the element substrate 4001, the sealant 4005, and the cover member 4006. In addition, an IC in which the signal line driver circuit 4003 is formed is mounted in a region different from the region surrounded by the sealant 4005 over the element substrate 4001.

  In addition, the pixel portion 4002 provided over the element substrate 4001 and the scan line driver circuit 4004 each include a plurality of TFTs. FIG. 17B illustrates the TFT 4010 included in the pixel portion 4002. Reference numeral 4011 corresponds to a light emitting element, and is electrically connected to the source region or the drain region of the TFT 4010.

  In addition, a variety of signals and potentials are supplied to the signal line driver circuit 4003 which is formed separately, the scan line driver circuit 4004, or the pixel portion 4002, although they are not shown in the cross-sectional view in FIG. And 4015 through a connection terminal 4016. Each of the connection terminal 4016 and the lead wirings 4014 and 4015 can be formed by a droplet discharge method or a printing method.

  The connection terminal 4016 is electrically connected to a terminal included in the FPC 4018 through an anisotropic conductive film 4019.

  Note that as the element substrate 4001 and the cover material 4006, glass, metal (typically stainless steel), ceramics, or plastic can be used. As the plastic, an FRP (Fiberglass-Reinforced Plastics) plate, a PVF (polyvinyl fluoride) film, a mylar film, a polyester film, or an acrylic resin film can be used. A sheet having a structure in which an aluminum foil is sandwiched between PVF films or mylar films can also be used.

  However, the cover material must be transparent on the substrate located in the light extraction direction from the light emitting element 4011. In that case, a light-transmitting material such as a glass plate, a plastic plate, a polyester film, or an acrylic film is used.

  As the filler 4007, in addition to an inert gas such as nitrogen or argon, an ultraviolet curable resin or a thermosetting resin can be used. PVC (polyvinyl chloride), acrylic, polyimide, epoxy resin, silicon resin, PVB (Polyvinyl butyral) or EVA (ethylene vinyl acetate) can be used. In this example, nitrogen was used as the filler.

  Further, in order to expose the filler 4007 to a hygroscopic substance (preferably barium oxide) or a substance capable of adsorbing oxygen, a hygroscopic substance or oxygen is added between the cover material 4006 and the element substrate 4001 together with the filler 4007. A substance capable of adsorbing may be provided. By providing a hygroscopic substance or a substance that can adsorb oxygen, deterioration of the light-emitting element 4011 can be suppressed.

  Note that FIG. 17 illustrates an example in which the signal line driver circuit 4003 is separately formed and mounted on the element substrate 4001; however, this embodiment is not limited to this structure. The scan line driver circuit may be separately formed and then mounted, or only part of the signal line driver circuit or part of the scan line driver circuit may be separately formed and then mounted.

  This embodiment can be implemented in combination with the structure described in other embodiments.

  Electronic devices that can use the light emitting device of the present invention include a video camera, a digital camera, a goggle type display (head mounted display), a navigation system, a sound reproduction device (car audio, audio component, etc.), a notebook type personal computer, a game A device, a portable information terminal (mobile computer, mobile phone, portable game machine, electronic book or the like), and an image playback device (typically a DVD: Digital Versatile Disc) or the like provided with a recording medium. And the like). In particular, the light-emitting device of the present invention can suppress an increase in charging time and a cost per area even when the number of pixels is increased. Therefore, the light-emitting device of the present invention is particularly suitable for an electronic device in which a relatively large panel is used. Specific examples of these electronic devices are shown in FIGS.

  FIG. 18A illustrates a display device, which includes a housing 2001, a display portion 2002, a speaker portion 2003, and the like. The light emitting device of the present invention can be used for the display portion 2002. Since the light-emitting device is a self-luminous type, a backlight is not necessary and a display portion thinner than a liquid crystal display can be obtained. The display devices include all information display devices for personal computers, TV broadcast reception, advertisement display, and the like. Note that in the case where a light-emitting device is used for the display device, a polarizing plate is provided in order to prevent external light from being reflected by the first electrode or the second electrode included in the light-emitting element to cause an image to be projected like a mirror surface. You can keep it.

  FIG. 18B illustrates a laptop personal computer, which includes a main body 2201, a housing 2202, a display portion 2203, a keyboard 2204, a mouse 2205, and the like. The light emitting device of the present invention can be used for the display portion 2203.

  FIG. 18C illustrates a portable image reproducing device (specifically, a DVD reproducing device) provided with a recording medium, which includes a main body 2401, a housing 2402, a display portion 2403, a recording medium (DVD or the like) reading portion 2404, An operation key 2405, a speaker portion 2406, and the like are included. The image reproducing device provided with the recording medium includes a home game machine and the like. The light emitting device of the present invention can be used for the display portion 2403.

  As described above, the applicable range of the present invention is so wide that it can be used for electronic devices in various fields. In addition, the electronic device of this embodiment may use the light emitting device having any structure shown in Embodiments 1 to 6.

  In this embodiment, an embodiment of wiring and electrodes formed using a droplet discharge method will be described.

  FIG. 19A shows a top view of a gate electrode 1901 and a scan line 1902 connected to the gate electrode. FIG. 19B is a cross-sectional view taken along A-A ′ in FIG. In FIG. 19A, it is desirable to suppress the wiring resistance and increase the throughput as compared with the gate electrode 1901, and a scanning line 1902 which requires less layout precision than the gate electrode 1901 has a wider line width than the gate electrode 1901. Form with. On the other hand, the gate electrode 1901 whose layout distance is shorter than that of the scanning line 1902 and whose layout precision is required is formed with a line width narrower than that of the scanning line 1902. The line width can be controlled by optimizing the ejection amount per droplet, the surface tension of the solution, the water repellency of the surface on which the droplet is dropped, and the like.

  As shown in FIG. 19A, by switching nozzles in accordance with wirings or electrodes to be formed, throughput can be improved and characteristics of a semiconductor element to be formed can be improved. Note that although FIG. 19A illustrates an example in which the nozzles are switched in order to change the line width between the scanning line and the gate electrode, this embodiment is not limited to this configuration. By switching nozzles between wirings or electrodes that require precise layout and wirings or electrodes where reduction of wiring resistance or improvement in throughput is important, the throughput is improved and the characteristics of the formed semiconductor element Can be increased.

  As shown in FIG. 19A, when the scanning direction is switched or the nozzle is switched when forming a wiring or an electrode, the wiring or electrode previously formed is irradiated with ultraviolet rays and then the next wiring is formed. Alternatively, an electrode may be formed. With the above structure, the adhesion of the surface of the previously formed wiring or electrode is improved, and the gate electrode 1901 and the scan line 1902 are hardly separated. In this case, firing may be performed every time a wiring or electrode is formed, or may be performed after all the wirings or electrodes that are in contact with each other are formed.

  Note that FIG. 19A illustrates an example in which the gate electrode 1901 and the scan line 1902 are formed over a flat surface; however, the present invention is not limited to this structure. For example, as illustrated in FIG. 19C, the scan line 1911 may be formed in the opening of the interlayer insulating film 1910, and the gate electrode 1912 in contact with the scan line 1911 may be formed over the interlayer insulating film 1910. In the case of FIG. 19C, an interlayer insulating film 1910 having an opening may be formed by a droplet discharge method, and then a scanning line 1911 may be formed in the opening by a droplet discharge method. And the scanning line 1911 may be formed in parallel by a droplet discharge method.

  Note that the wiring may be formed of two conductive layers. As shown in FIG. 19D, after a conductive layer 1920 is formed over a flat surface by a droplet discharge method, an interlayer insulating film 1921 is formed by a droplet discharge method so that the conductive layer 1920 is exposed in the opening. . Then, a conductive layer 1922 is formed by a droplet discharge method so as to be in contact with the conductive layer 1920 in the opening. The conductive layer 1920 and the conductive layer 1922 can be combined and used as one wiring such as a scan line or a signal line.

FIG. 6 is a circuit diagram of a pixel included in the light-emitting device of the present invention. FIG. 6 is a diagram schematically illustrating the operation of a pixel included in a light emitting device of the present invention. FIG. 6 is a circuit diagram of a pixel included in the light-emitting device of the present invention. 4A and 4B illustrate a method for manufacturing a light-emitting device of the present invention. 4A and 4B illustrate a method for manufacturing a light-emitting device of the present invention. 4A and 4B illustrate a method for manufacturing a light-emitting device of the present invention. 4 is a top view of a pixel included in a light-emitting device of the present invention. FIG. 4A and 4B illustrate a method for manufacturing a light-emitting device of the present invention. 4 is a cross-sectional view of a pixel included in a light-emitting device of the present invention. FIG. 4 is a cross-sectional view of a pixel included in a light-emitting device of the present invention. FIG. 4 is a cross-sectional view of a pixel included in a light-emitting device of the present invention. FIG. FIG. 6 is a circuit diagram of a pixel included in the light-emitting device of the present invention. FIG. 6 is a circuit diagram of a pixel included in the light-emitting device of the present invention. FIG. 6 illustrates a structure of a light-emitting element included in a light-emitting device of the present invention. The perspective view of the element substrate which the light emitting device of the present invention has. 1 is a block diagram illustrating a configuration of a light emitting device of the present invention. 2A and 2B are a top view and a cross-sectional view of a light-emitting device of the present invention. FIG. 14 is a diagram of an electronic device using the light-emitting device of the present invention. 4A and 4B illustrate a method for manufacturing a light-emitting device of the present invention.

Claims (20)

A light emitting element; a first TFT for determining a current value flowing through the light emitting element; a second TFT for determining light emission or non-light emission of the light emitting element according to a video signal; a first power supply line; Power line and
The first TFT and the second TFT are connected in series between the light emitting element and the first power supply line,
A gate electrode of the first TFT is connected to the second power supply line;
Any of the gate electrode of the first TFT, the gate electrode of the second TFT, the first power supply line, or the second power supply line is formed using a droplet discharge method or a printing method. A light emitting device characterized by that. A light emitting element; a first TFT for determining a current value flowing through the light emitting element; a second TFT for determining light emission or non-light emission of the light emitting element by a video signal; a third TFT; A power line, a second power line, and a signal line;
The first TFT and the second TFT are connected in series between the light emitting element and the first power supply line,
A gate electrode of the first TFT is connected to the second power supply line;
The third TFT controls the potential of the video signal input to the signal line to be applied to the gate electrode of the second TFT,
Any of the gate electrode of the first TFT, the gate electrode of the second TFT, the gate electrode of the third TFT, the signal line, the first power supply line, or the second power supply line is a liquid. A light-emitting device formed using a droplet discharge method or a printing method. A light emitting element; a first TFT for determining a current value flowing through the light emitting element; a second TFT for determining light emission or non-light emission of the light emitting element by a video signal; a third TFT; A TFT, a first power line, a second power line, and a signal line;
The first TFT and the second TFT are connected in series between the light emitting element and the first power supply line,
A gate electrode of the first TFT is connected to the second power supply line;
The third TFT controls the potential of the video signal input to the signal line to be applied to the gate electrode of the second TFT,
The fourth TFT controls the connection between the gate electrode and the source region of the second TFT and the first power supply line regardless of the potential of the video signal.
The gate electrode of the first TFT, the gate electrode of the second TFT, the gate electrode of the third TFT, the gate electrode of the fourth TFT, the signal line, the first power supply line, or the second One of the power lines is formed using a droplet discharge method or a printing method.   4. The light-emitting device according to claim 3, wherein the fourth TFT includes a semiconductor film including a channel formation region, and the semiconductor film uses a semi-amorphous semiconductor or an amorphous semiconductor.   5. The third TFT according to claim 2, wherein the third TFT includes a semiconductor film including a channel formation region, and the semiconductor film uses a semi-amorphous semiconductor or an amorphous semiconductor. A light emitting device characterized by the above. In any one of Claims 1 thru | or 5,
A light-emitting device, wherein the first TFT and the second TFT have n-type polarity.   7. The semiconductor device according to claim 1, wherein the first TFT and the second TFT each include a semiconductor film including a channel formation region, and the semiconductor film is a semi-amorphous semiconductor or an amorphous semiconductor. A light-emitting device using a semiconductor. In any one of Claims 1 thru | or 7,
The ratio of the channel length to the channel width in the first TFT is larger than the ratio of the channel length to the channel width in the second TFT. In any one of Claims 1 thru | or 8,
The light-emitting element includes a first electrode, a second electrode, and an electroluminescent layer formed between the first electrode and the second electrode,
Any one of the first electrode, the second electrode, and the electroluminescent layer is formed using a droplet discharge method.   10. The light emitting device according to claim 1, wherein the printing method is an offset printing method or a screen printing method. Either the gate electrode of the first TFT, the gate electrode of the second TFT, the first power supply line, or the second power supply line is formed using a droplet discharge method or a printing method,
The first TFT determines a light emitting element and a current value flowing through the light emitting element,
The second TFT determines light emission or non-light emission of the light emitting element according to a video signal,
The first TFT and the second TFT are connected in series between the light emitting element and the first power supply line,
A method for manufacturing a light-emitting device, wherein the gate electrode of the first TFT is connected to the second power supply line. One of the gate electrode of the first TFT, the gate electrode of the second TFT, the gate electrode of the third TFT, the signal line, the first power supply line, or the second power supply line is a droplet discharge method or a printing method. Formed using
The first TFT determines a light emitting element and a current value flowing through the light emitting element,
The second TFT determines light emission or non-light emission of the light emitting element according to a video signal,
The third TFT controls the potential of the video signal input to the signal line to be applied to the gate electrode of the second TFT,
The first TFT and the second TFT are connected in series between the light emitting element and the first power supply line,
A method for manufacturing a light-emitting device, wherein the gate electrode of the first TFT is connected to the second power supply line. Any one of the gate electrode of the first TFT, the gate electrode of the second TFT, the gate electrode of the third TFT, the gate electrode of the fourth TFT, the signal line, the first power supply line or the second power supply line is , Formed using droplet discharge method or printing method,
The first TFT determines a light emitting element and a current value flowing through the light emitting element,
The second TFT determines light emission or non-light emission of the light emitting element according to a video signal,
The third TFT controls the potential of the video signal input to the signal line to be applied to the gate electrode of the second TFT,
The fourth TFT controls the connection between the gate electrode and source region of the second TFT and the first power supply line regardless of the potential of the video signal,
The first TFT and the second TFT are connected in series between the light emitting element and the first power supply line,
A method for manufacturing a light-emitting device, wherein the gate electrode of the first TFT is connected to the second power supply line.   4. The method for manufacturing a light-emitting device according to claim 3, wherein the fourth TFT includes a semiconductor film including a channel formation region, and the semiconductor film uses a semi-amorphous semiconductor or an amorphous semiconductor. .   15. The semiconductor device according to claim 12, wherein the third TFT includes a semiconductor film including a channel formation region, and the semiconductor film uses a semi-amorphous semiconductor or an amorphous semiconductor. A method for manufacturing a light-emitting device. In any one of Claims 11 thru | or 15,
A method for manufacturing a light-emitting device, wherein the first TFT and the second TFT have n-type polarity.   17. The semiconductor device according to claim 11, wherein the first TFT and the second TFT include a semiconductor film including a channel formation region, and the semiconductor film is a semi-amorphous semiconductor or an amorphous semiconductor. A manufacturing method of a light-emitting device using a semiconductor. In any one of Claims 11 thru | or 17,
A method for manufacturing a light-emitting device, wherein a ratio of a channel length to a channel width in the first TFT is larger than a ratio of a channel length to a channel width in the second TFT. In any one of Claims 11 thru | or 18,
The light-emitting element includes a first electrode, a second electrode, and an electroluminescent layer formed between the first electrode and the second electrode,
Any one of the first electrode, the second electrode, and the electroluminescent layer is formed using a droplet discharge method. 20. The method for manufacturing a light-emitting device according to claim 11, wherein the printing method is an offset printing method or a screen printing method.

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