Display device and its manufacturing method

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention provides an element (hereinafter referred to as "EL element") in which a thin film (hereinafter referred to as "EL film") made of a compound capable of obtaining electroluminescence (hereinafter referred to as EL) is sandwiched between electrodes. The present invention relates to a display device including the display device and a method for manufacturing the same.

【0002】

The EL includes phosphorescence that is emitted when transitioning from the triplet excited state to the ground state, and fluorescence that is emitted when transitioning from the singlet excited state to the ground state.

【0003】

An inorganic material or an organic material can be used for the EL film. The organic EL film uses an organic material as the EL film. The organic EL element is an EL element in which an organic EL film is sandwiched between electrodes.

【0004】

As used herein, a thin film transistor (TFT) device is a semiconductor device having at least three electrodes. These electrodes are a gate electrode, a source electrode, and a drain electrode, and the source electrode and the gate electrode may also function as wiring.

【0005】

[Conventional technology]

Display devices using organic EL films can be made lighter and thinner than conventional CRTs, and are being applied to various applications. Mobile phones and personal digital assistants (PDAs) can be connected to the Internet, dramatically increasing the amount of information displayed on video displays, and colorizing and high-definition display devices. The demand for conversion is increasing.

【0006】

As a means for improving the definition of the display device, a means for applying a voltage to the EL film by an active element such as a thin film transistor (TFT) is adopted.

【0007】

In addition, since the display device in which the pixel portion is formed by the EL element is a self-luminous type and does not require a light source such as a backlight unlike the liquid crystal display device, it is regarded as a promising means for realizing weight reduction and thinning. There is.

【0008】

[Problems to be Solved by the Invention]

In general, an EL element has an EL film formed on an anode formed for each pixel and a cathode formed as a common electrode on the EL film. However, in order to reduce the resistance, an EL film with a film thickness of 30 nm to 150 nm is formed on the anode with a film thickness of about 200 nm, so that the EL film is broken on the side surface of the anode. It was. When the EL film is broken, the anode and cathode are short-circuited at the broken part, and the EL film does not emit light, resulting in a black spot defect.

【0009】

Therefore, a cross-sectional structure as shown in FIG. 18 has been proposed. FIG. 18 is a cross section of a conventional EL element. In order to prevent disconnection of the EL film 1002, the purpose is to prevent a short circuit between the anode and the cathode 1003 at the end of the anode by covering the end of the anode 1000 with the insulating film 1001. The insulating film provided at the end of the anode is generally called a bump.

【0010】

However, even in the cross-sectional structure of FIG. 18, some problems can be seen in the actual process. As shown in FIG. 18, when the side surface of the insulating film 1001 on the anode 1000 is linear, the EL film is likely to be disconnected at 1004 where the upper surface of the anode and the side surface of the insulating film meet. That is, in a place where the inclination of the film-forming surface of the EL film changes abruptly, the EL film 1002 is not deposited and a gap is formed. This gap causes a short circuit between the anode and the cathode. Even if the EL film is not broken, at 1004 where the upper surface of the anode and the side surface of the insulating film meet, when the EL film becomes thin, the electric field concentrates on the thinned part of the EL film, and the EL film becomes thin. Light emission occurs only in the place.

【0011】

Furthermore, when the cathode on the insulating film conducts with the wiring under the insulating film through the contact hole penetrating the insulating film, if the cathode is disconnected on the side surface of the insulating film, no potential is applied to the cathode and the display is performed. In some cases, it will not be broken.

【0012】

In addition, disconnection of the EL film and the cathode is likely to occur in the vicinity of the tangent line 1005 between the side surface of the insulating film 1001 and the upper surface of the insulating film. Usually, the insulating film (bump) covers the gap between adjacent pixels and is formed in a striped shape. At this time, when a bump is formed around the pixel, a disconnection of the cathode occurs, and when the disconnection is continuously connected to form a closed curve, the cathode inside the closed curve does not function as an electrode. No voltage is applied to the EL film. That is, it becomes a point defect.

【0013】

When the number of pixels is increased in order to improve the definition of a display device using an EL element, a point defect due to a short circuit between the anode and the cathode or a point defect due to a disconnection of the cathode causes a yield and a factor of deteriorating the display quality. Is required. Further, the concentration of the electric field due to the local thinning of the EL film causes the brightness of the defective pixel to change with respect to the brightness of the non-defective pixel, which impairs the visibility, so countermeasures are required.

【0014】

[Means for solving problems]

By optimizing the shape of the bump, the present inventors gently change the inclination of the film formation surface of the EL film and the cathode on the bump, so that the EL film and the cathode are easily formed into a uniform film thickness. Therefore, it was thought that the disconnection of the EL film and the cathode and the local change in the film thickness of the EL film could be suppressed. Therefore, the shape of the bumps was optimized so that the EL film and cathode could be formed with a uniform film thickness and excellent display performance could be ensured.

【0015】

The terms used to indicate the shape of the bump in the present invention will be described below with reference to FIG. 20 (A) to 20 (B) are examples of cross-sectional views showing the shape of the bump.

【0016】

For example, in the case where the upper surface 107 shown in the cross-sectional view of FIG. 20A is a flat bump, both ends of the lower portion of the insulating film 101 are lower ends 104, both ends of the upper portion of the insulating film are upper ends 106, and the upper surface of the insulating film. The portion at a height between 107 and the surface in contact with the upper surface of the anode 100 under the insulating film is called the central portion 105. The surface of the insulating film is divided into a flat upper surface 107 and a side surface 108.

【0017】

For example, in the case of a bump having a curved upper portion shown in the cross-sectional view of FIG. 20 (B), both ends of the lower portion of the insulating film 201 are the lower end portions 204, and the vicinity of the thickest portion of the insulating film is the upper portion 206. The portion having a height between the upper portion 206 of the insulating film and the surface in contact with the upper surface of the anode 200 under the insulating film is called the central portion 205.

【0018】

An example of the configuration of the present invention is shown in FIG. 1 (A). FIG. 1 (A) shows an example of a cross section of the EL element. There is one electrode of the EL element, for example, the anode 100, and an insulating film (bump) 101 selectively formed on the anode 100. Further, the EL film 102 is formed on the insulating film and the anode, and the cathode 103 is formed on the EL film. The present invention is characterized by the shape of the insulating film. The shape of the insulating film will be described below with reference to FIG. FIG. 2 is a cross-sectional view illustrating the cross-sectional shape of the bump.

【0019】

In the present invention, the thickness (T) of the insulating film 101 means the film thickness of the insulating film when it is used as a device. The thickness (T) of the insulating film means the length of a perpendicular line drawn from the upper surface of the insulating film to the lower surface of the insulating film.

【0020】

In order to prevent disconnection of the EL film 102 and the cathode 103, the thickness of the insulating film should not be too thick, preferably 3.0 μm or less. Further, the thickness of the insulating film is preferably at least 1.0 μm or more in order to reduce the parasitic capacitance between the cathode 103 formed on the insulating film and the TFT element below the insulating film 101. That is, the thickness of the insulating film is preferably 1.0 μm or more and 3.0 μm or less.

【0021】

(1) In the EL element, the EL element has one electrode of the EL element, for example, an anode 100, and an insulating film 101 selectively formed on the anode, and the lower end portion of the insulating film in contact with the upper surface of the anode. 104 is in contact with an ellipse or circle centered on the outside of the side surface of the insulating film, and the upper end 106 is continuous with the upper surface 107 of the insulating film and is in contact with the ellipse or circle centered on the inside of the side surface 108 of the insulating film. It is a feature (Fig. 2 (B)). As described above, when the lower end portion and the upper end portion of the insulating film are formed into a smooth shape, the inclination of the film-forming surface is continuously changed to prevent disconnection of the EL film 102 and the cathode 103. Further, it is possible to prevent the film thickness of the EL film from being locally thinned at the portion sandwiched between the cathode and the anode, and it is possible to prevent the electric field from being locally concentrated on the EL film.

【0022】

The center of the ellipse is the intersection of the minor axis and the major axis of the ellipse. The center of a circle is an intersection when at least three perpendicular lines to the tangents of the circle are provided at different positions in the circle.

【0023】

(2) In addition to the configuration of (1) above, the central portion 105 of the insulating film has a side surface in which the angle θ between the surface in contact with the side surface of the insulating film and the upper surface of the anode is 35 ° or more and 70 ° or less. , It is possible to prevent disconnection of the EL film and the cathode on the side surface 108 of the insulating film. In the present specification, the "central portion" refers to a portion of the insulating film 101 having a height intermediate between the upper surface of the insulating film and the surface in contact with the upper surface of the anode. In the present specification, the surface in contact with the side surface of the insulating film is hereinafter referred to as an "inclined surface". The angle formed by the inclined surface and the upper surface of the anode is referred to as a "tapered angle of the inclined surface".

【0024】

The taper angle of the inclined surface at the central portion of the insulating film is preferably 35 ° or more and 70 ° or less. If the taper angle of the inclined surface exceeds 70 °, the film thickness of the cathode becomes thin on the side surface of the insulating film, and the possibility of disconnection of the cathode increases. When the taper angle of the inclined surface is less than 35 °, the film thickness of the insulating film (bump) tends to decrease as the taper angle of the inclined surface decreases. If the film thickness of the insulating film becomes thin, the parasitic capacitance between the TFT element below the insulating film and the cathode on the insulating film increases, which is not preferable.

【0025】

(3) In the EL element, the present invention has one electrode of the EL element, for example, an anode 100 and an insulating film 101 selectively formed on the anode. The lower end portion 104 of the insulating film is in contact with the upper surface of the anode 100 and is in contact with the curved side surface determined by the center of curvature (O1) and the first radius of curvature (R1) above the tangent line between the anode and the lower end portion. The upper end 106 of the insulating film is a curved surface that is continuous with the upper surface of the insulating film and is determined by the center of curvature (O2) below the boundary line between the upper end 106 and the flat upper surface 107 and the second radius of curvature (R2). It has a shaped side surface (Fig. 2 (A), Fig. 2 (B)).

【0026】

Since the lower end of the insulating film has a gentle curved surface shape in which the inclination of the film-forming surface of the EL film changes continuously, the coverage of the EL film formed at the lower end of the insulating film is improved, and the lower end portion. It is possible to prevent the EL film from being broken. As a result, the short circuit between the anode and the cathode due to the disconnection of the EL film is reduced. In addition, it is possible to prevent the EL film from being partially thinned, and it is possible to prevent local electric field concentration in the EL film.

【0027】

At the upper end 106 of the insulating film, the inclination of the surface in contact with the side surface of the insulating film changes continuously with respect to the upper surface of the anode 100, so that the EL film and the cathode in the vicinity of the boundary between the upper surface 107 and the side surface 108 of the insulating film It is possible to prevent disconnection. In particular, since the disconnection of the cathode can be prevented, when the insulating film is provided so as to cover the entire end portion of the anode, the disconnection portion of the cathode is continuously formed into a closed curve, which prevents a point defect. Further, when the insulating film is provided in a stripe shape so as to cover a part of the end portion of the anode, it is possible to prevent the wiring resistance of the cathode from increasing due to the disconnection of the cathode. Further, it is possible to prevent the cathode from being disconnected on the side surface of the contact hole when the cathode comes into contact with the wiring under the insulating film through the contact hole penetrating the insulating film.

【0028】

(4) In addition to the configuration of (3) above, the present invention is characterized in that the first radius of curvature is 0.2 μm or more and 3.0 μm or less. First radius of curvature (R₁) Is less than 0.2 μm, the side surface of the insulating film 101 in contact with the anode 100 has a sharp shape, and it becomes difficult to form the EL film and the cathode with a uniform film thickness on the side surface of the insulating film 101. There is a fear. For example, since the inclination of the film-forming surface of the EL film changes abruptly, the EL film becomes thin and the electric field is locally concentrated on that portion. Further, when the first radius of curvature exceeds 3.0 μm, a thin portion of the insulating film is widely present, and it tends to be difficult to cover the TFT element with the insulating film.

【0029】

Whether etching with an aqueous solution of an acid or base or etching with a reactive gas, the shape can be easily controlled if the first radius of curvature is 0.2 μm or more and 3.0 μm or less.

【0030】

(5) In addition to the configurations of (3) and (4) above, it is preferable that the taper angle θ of the inclined surface of the central portion 105 of the insulating film is 35 ° or more and 70 ° or less.

【0031】

(6) In addition to the configurations of (3), (4) and (5) above, the second radius of curvature (R)₂) Is preferably 0.2 μm or more and 3.0 μm or less. Second radius of curvature (R₂) Is too small, the side surface of the insulating film in contact with the upper surface of the insulating film 101 becomes a steep shape. Therefore, in the cross-sectional shape of the insulating film 101, even if the upper end is curved, the EL film is prevented from being broken. The effect is low. Therefore, the second radius of curvature needs to be at least 0.2 μm or more.

【0032】

Whether etching with an aqueous solution of an acid or base or etching with a reactive gas, the second radius of curvature is appropriately 0.2 μm or more and 3.0 μm or less as the radius of curvature that can be controlled in the actual process. ..

【0033】

By providing the radius of curvature or inclination of the side surfaces of the lower end, center and upper end of the insulating film within the above numerical range, the side shape of the insulating film as a whole becomes gentle and the EL film and cathode are prevented from being disconnected. It will be easier. Further, it is possible to prevent the concentration of the electric field due to the local thinning of the EL film on the side surface of the lower end portion of the insulating film.

【0034】

By the way, FIG. 1 (B) shows a structure capable of more effectively preventing the disconnection of the cathode with respect to FIG. 1 (A). In FIG. 1B, an insulating film 201 is selectively provided on an electrode, for example, an anode 200, and an EL film 202 is formed on the insulating film 201 and a cathode 203 is formed on the EL film. The feature of Fig. 1 (B) is that the side surface of the insulating film is curved, including the upper part of the insulating film.

【0035】

The cross-sectional shape of the insulating film shown in FIG. 1 (B) will be described in detail with reference to FIG.

【0036】

The thickness (T) of the insulating film in FIG. 3 refers to the length of a perpendicular line drawn from the upper end of the insulating film to the lower surface of the insulating film. The upper end portion refers to a portion on the surface of the insulating film where the distance from the plane on which the insulating film is formed is maximum. The thickness of the insulating film should be 3.0 μm or less.

【0037】

(7) In the EL element, the EL element has one electrode of the EL element, for example, an anode 200, and an insulating film 201 selectively formed on the anode, and the lower end portion of the insulating film in contact with the upper surface of the anode. 204 has a side surface tangent to an ellipse or a circle having a center on the outside of the side surface of the insulating film, and the upper end 206 has a side surface tangent to an ellipse or a circle having a center inside the side surface of the insulating film. (Fig. 3 (B)).

【0038】

(8) In addition to the configuration of (7) above, the present invention is characterized in that the taper angle θ of the inclined surface at the central portion 205 of the insulating film is 35 ° or more and 70 ° or less.

【0039】

(9) In the EL element, the present invention has one electrode of the EL element, for example, an anode 200 and an insulating film 201 selectively formed on the anode. The lower end 204 of the insulating film is in contact with the upper surface of the anode 200 and is the center of curvature (O) above the contact point between the anode and the lower end.₁) And the first radius of curvature (R)₁) Has a curved side surface. The upper end 206 of the insulating film has a center of curvature (O) below the upper end.₂) And the second radius of curvature (R)₂) Has a curved side surface. It is preferable not only to make the lower end and upper side surfaces of the insulating film curved, but also to set the taper angle of the inclined surface at the central portion 205 of the insulating film to 35 ° or more and 70 ° or less (Fig. 3 (A)). , Figure 3 (B)).

【0040】

(10) In addition to the configuration of (9) above, the first radius of curvature (R) of the lower end 204₁) Is preferably 0.2 μm or more and 3.0 μm or less. First radius of curvature (R₁) Is too small, the side surface of the insulating film 201 in contact with the anode 200 becomes a steep shape. Therefore, in the cross-sectional shape of the insulating film 201, even if the lower end is curved, the EL film is broken and the EL film is locally formed. The effect of preventing thinning is low. Therefore, the first radius of curvature needs to be at least 0.2 μm or more. However, if the first radius of curvature is too large, a region where the film thickness of the insulating film is thin exists widely, and it becomes difficult for the insulating film to cover the TFT element. Therefore, there is a problem even if the first radius of curvature of the insulating film is too large in the EL display device. Therefore, the radius of curvature of the first insulating film is preferably 3.0 μm or less. In terms of process, the first radius of curvature (R)₁) Is 0.2 μm or more and 3.0 μm or less, it can be sufficiently controlled in the actual process.

【0041】

(11) In addition to the above configurations (8), (9), and (10), in the present invention, in the cross-sectional shape of the insulating film, the upper 206 of the insulating film is the lower center of curvature (O) of the upper part.₂) And the second center of curvature (R)₂) Is the curved surface shape. By gently changing the surfaces forming the EL film and the cathode in this way, it is possible to prevent the cathode from being disconnected due to the thinning of the film thickness of the cathode on the surface of the insulating film. Second radius of curvature of top 206 (R₂) Should be determined in consideration of the distance between the anodes adjacent to each other. In FIGS. 1B and 3B, by forming the upper end 206 of the insulating film into a curved surface, it is possible to prevent disconnection of the cathode layer due to a sudden change in angle, which is effective.

【0042】

In FIGS. 2 to 3, from the lower end to the upper end (or upper part) of the side surface of the insulating film, the taper angle θ of the inclined surface becomes 0 ° at the end of the insulating film in which the electrode and the insulating film are in contact with each other, and the insulating film is insulated. The shape that continuously changes in the range of 0 ° to 70 ° along the side surface of the film prevents disconnection of the EL film and cathode, and prevents concentration of the electric field due to the local thinning of the EL film. preferable.

【0043】

By using the above-mentioned EL film as an organic EL film formed from an organic material, DC drive and low voltage drive are possible, and a low power consumption display device can be manufactured.

【0044】

Although the description has focused on the active matrix type display device, the present invention can be applied to either the passive matrix type or the active matrix type. This is because the shape of the insulating film can effectively prevent the cathode and the EL film from being broken and the EL film from being locally thinned.

【0045】

Further, although the electrode under the insulating film has been described by taking the anode as an example, the electrode under the insulating film can also be used as the cathode.

【0046】

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described below.

【0047】

First, a process using a non-photosensitive polyimide resin film and a non-photosensitive acrylic film as organic materials will be shown. When the insulating film is etched with the reactive gas, the cross-sectional shape of the insulating film shown in FIG. 1 (A) can be produced by gradually changing the flow rate ratio of the reactive gas. An example of the manufacturing method is shown below with reference to FIG.

【0048】

A TFT element is formed on the substrate as a switching element for the organic EL element. In the TFT element, a drain side electrode 416 and a source side electrode 417 are connected to the semiconductor layer, and a gate electrode 411 is provided above the semiconductor layer. An anode 422 of an electrically connected organic EL element is formed under the electrode 416 on the drain side of the TFT element. As the anode, a transparent conductive film such as ITO (indium tin oxide) can be used.

【0049】

As the first step, an insulating film 301 is formed on these electrodes. As the insulating film, an acrylic resin film or a polyimide resin film can be formed. First, an insulating film is applied onto the substrate. Then, heat treatment is performed at a temperature of 50 ° C to 150 ° C for 1 to 5 minutes to remove the solvent contained in the polyimide resin film. Further, the polyimide resin film is imidized by heat treatment at 200 ° C to 250 ° C in an oven. The film thickness of the polyimide resin film after imidization is preferably 1.0 μm or more and 3.0 μm or less.

【0050】

As the second step, the resist film 300 is patterned on the insulating film 301. A photosensitive photoresist film (hereinafter referred to as a resist film) is formed on the polyimide resin film. The resist film 300 preferably has a taper such that the side surface of the resist film and the lower surface of the resist film form an angle of 50 ° to 80 ° after patterning (FIG. 4 (A)).

【0051】

As a third step, the insulating film is etched with at least the first reactive gas and the second reactive gas. At this time, the flow rate ratio of the first reactive gas and the second reactive gas is changed with time. First reactive gas CF for etching gas₄And the second reactive gas O₂And the inert gas He will be used to illustrate a method of etching a polyimide resin film. First reactive gas CF₄The larger the gas flow rate ratio of, the easier it is for the polyimide resin film 303 to be etched as compared with the resist film 302. That is, the depth (Y) at which the polyimide resin film 303 is etched in the film thickness direction is larger than the width (X) at which the side surface portion of the resist film 302 recedes toward the inside of the resist film, and Y / X. The taper angle of the inclined surface of the insulating film, which is determined depending on the above, increases. That is, the first reactive gas CF₄When the gas flow rate ratio of is large, the taper angle of the inclined surface is large and the shape becomes sharp.

【0052】

Conversely, the first reactive gas CF₄When the gas flow rate ratio of is small, the taper angle of the inclined surface is small, and the shape is gently inclined.

【0053】

Therefore, the first reactive gas CF₄And the second reactive gas O₂By gradually changing the flow rate ratio with, the taper angle of the inclined surface of the insulating film can be gently changed.

【0054】

As the first etching step, the RIE (Reactive Ion Etching) method is used, and the first reactive gas CF is used as the etching gas.₄, Second reactive gas O₂, The inert gas He is used. CF when starting etching₄And O₂The gas flow rate ratio of and He is 1.5 / 98.5 / 40 (sccm). Then, as the etching time progresses, the second reactive gas O₂First reactive gas CF against₄The gas flow rate ratio of is increased every hour, and finally CF₄And O₂The gas flow rate ratio between He and He should be 7/93/40 (sccm). First reactive gas CF₄By increasing the flow rate ratio of, the taper angle of the inclined surface of the insulating film becomes large. Therefore, by continuously changing the taper angle of the inclined surface in small steps, the side surface of the insulating film becomes curved. The radius of curvature of this curved surface is called the first radius of curvature. The first radius of curvature is preferably 0.2 μm or more and 3.0 μm or less. In this way, the first region 318 is formed on the side surface of the insulating film (FIG. 4 (B)).

【0055】

The etching conditions performed in the first etching step are called the first etching conditions.

【0056】

In addition, in the first etching condition, the first reactive gas CF₄When the time change of the gas flow rate ratio of is made gentle, the inclination of the side surface of the insulating film gradually changes, so that the first radius of curvature becomes large. Conversely, in the first etching, the first reactive gas CF₄The first radius of curvature becomes smaller by making the time change of the gas flow rate ratio steep.

【0057】

After that, etching is performed without removing the resist film. In the second etching process, CF is used as it is in the etching gas.₄And O₂And He, the first reactive gas CF₄, Second reactive gas O₂, Keep the gas flow rate ratio of the inert gas He constant at 7/93/40 (sccm) and continue etching. As a result, on the side surface of the insulating film 303, a region where the taper angle of the inclined surface is constant is formed. As a result, a second region 319 is formed on the side surface of the insulating film. The final gas flow ratio in the first etching step determines the taper angle of the inclined surface of the insulating film formed in the second etching step. Second reactive gas O₂First reactive gas CF against₄The larger the ratio of, the larger the taper angle of the inclined surface of the insulating film. In the second region 319, the taper angle of the side surface of the insulating film is preferably 35 ° or more and 70 ° or less.

【0058】

In the etching under the second etching condition, the anisotropic etching with the reactive gas is performed, so that the first region 318 on the side surface of the insulating film formed in FIG. 4 (B) retains its shape. , Transferred to the underside of the polyimide resin film.

【0059】

The upper surface and the side surface of the resist film 304 are etched to reduce the film thickness, and the side surface recedes inside the resist film (FIG. 4 (C)).

【0060】

Next, a third etching step is performed. Change to the third etching condition without removing the resist film, and use CF as it is for etching gas.₄And O₂And He, the second reactive gas O₂First reactive gas CF against₄The ratio of is decreased every hour. For example, CF₄And O₂The gas flow rate ratio between He and He is changed over time from 7/93/40 (sccm) to 1.5 / 98.5 / 40 (sccm). As a result, the taper angle of the inclined surface of the insulating film is gradually reduced to form a curved surface. The radius of curvature of this curved surface is called the second radius of curvature. A third region 320 of the insulating film 307 is formed by the third etching condition.

【0061】

The upper surface and the side surface of the resist film 306 are etched to reduce the film thickness, and the side surface recedes inside the resist film (FIG. 5 (A)).

【0062】

Under the first etching condition, the second etching condition, and the third etching condition, 500 W RF (13.56 MHz) power is applied at a pressure of 65 Pa to generate plasma and perform etching.

【0063】

As a result, the first region 318, the second region 319, and the third region 320 are formed on the side surface of the insulating film. The first region includes the lower end of the insulating film. The second region includes the central part of the insulating film. The third region includes the upper end of the insulating film.

【0064】

Then, as the fourth step, the resist film 306 is removed, and as the fifth step, the EL film 423 is formed on the insulating film and the electrode. Further, the EL element is formed by forming the cathode 424 on the EL film (Fig. 5 (B)).

【0065】

The cross section shown by the chain line B-B'in FIG. 5 (B) corresponds to the cross section obtained by cutting the top view of FIG. 9 along the chain line B-B'. The same parts as in FIG. 9 are designated by the same reference numerals.

【0066】

Etching with a reactive gas has the advantage that microfabrication is possible. Although FIG. 4 shows an example in which an organic material is used as the insulating film, it is also possible to use an inorganic material as the insulating film. For example, SiO as an insulating film₂When a membrane is used, CHF is used as the first reactive gas as the reactive gas.₃To the second reactive gas using O₂It is good to use. Then, as described above, in the first etching step, the second etching step, and the third etching step, the flow ratios of the first reactive gas and the second reactive gas are changed. First reactive gas CHF₃The higher the gas flow rate ratio of, the easier the etching of the insulating film in the film thickness direction proceeds, and the higher the taper angle of the inclined surface. In this way, even if the material of the above-mentioned step is replaced, the first region 318 and the third region 320 of the insulating film are formed in a curved surface shape as in FIG. 5 (A), and the second region 319. It is possible to make the inclined surface of the above constant.

【0067】

However, since the inorganic insulating film reflects the unevenness below, the surface of the inorganic insulating film may have irregularities due to the wiring of the TFT element or the like. In this case, the surface of the inorganic insulating film may be polished in advance by CMP (Chemical Mechanical Polishing), then a resist film may be formed, and the inorganic insulating film may be etched to form bumps.

【0068】

Further, a method of producing the shape of FIG. 1 (B) using the polyimide resin film will be described with reference to FIG.

【0069】

Before thermosetting, the polyimide resin film is an organic film containing a polyamic acid as a main component, and is dehydrated and condensed by thermosetting to become a polyimide film. In the embodiments described with reference to FIGS. 4 to 5, since it is not necessary to distinguish them, the resin films before and after thermosetting are also described as polyimide resin films. However, since the difference in chemical properties between polyamic acid and polyimide is used in the process shown in FIG. 6, the difference will be clearly described.

【0070】

First, in the first step, an organic film 309 containing a polyamic acid as a main component is applied onto the electrode.

【0071】

Then, as the second step, heat treatment is performed at a temperature of 50 ° C to 150 ° C for 1 to 5 minutes to remove the solvent in the organic film. Next, as a third step, a resist film 308 is formed on the organic film 309. The film thickness of the resist film is preferably about 0.5 μm to 3.0 μm. Then, as the fourth step, the resist film is exposed by irradiating ultraviolet rays through a photomask (Fig. 6 (A)).

【0072】

Then, as a fifth step, the resist film and the organic film on the substrate are immersed in a developing solution having basicity for development. As the developer, for example, a tetramethylammonium hydroxide (TMAH) developer having a concentration of 2.0 to 6.0% can be used. First, of the resist film, the portion exposed to ultraviolet rays is dissolved in the developing solution. After that, the organic film 311 containing a polyamic acid as a main component is isotropically etched with a resist film as a mask by a developing solution showing basicity. The polyimide resin film 311 under the resist film 310 remains largely protected by the resist film, but the polyimide resin film below the edge of the resist film still has a curved cross section on the side surface due to isotropic etching (isotropic etching). Figure 6 (B)).

【0073】

Then, as a sixth step, the resist film is immersed in the solvent of the resist film to dissolve and remove the resist film. An example of a solvent for a resist membrane is NMP (N-methyl-2-pyrrolidone).

【0074】

Then, as the seventh step, the organic film is dehydrated and condensed to be imidized at a temperature of 180 ° C. or higher and 350 ° C. or lower for 1 hour to 3 hours. As a result, the organic film containing polyamic acid as a main component is chemically transformed into a polyimide resin film. The polyimide resin film shrinks inward with imidization, and the surface of the polyimide resin film 312 becomes rounded (Fig. 6 (C)).

【0075】

In this way, the first region 321, the second region 322, and the third region 323 are formed on the surface of the insulating film. The first region 321 is a curved surface shape including the lower end portion of the insulating film. The second region 322 includes the central portion of the side surface of the insulating film. The third region 323 includes the upper end of the insulating film.

【0076】

The second region 322 is slightly rounded due to heat shrinkage of the polyimide film. At this time, it is preferable that the angle formed by the surface in contact with the side surface and the upper surface of the anode 422 in the central portion of the insulating film is in the range of 35 ° to 70 °.

【0077】

The third region 323 is rounded due to heat shrinkage, and the surface of the insulating film has a curved surface shape in a range including the side surface and the upper end portion of the insulating film.

【0078】

Next, as the eighth step, the EL film 423 is formed on the polyimide resin film, and the cathode 424 is formed on the EL film (FIG. 6 (D)).

【0079】

Another example of the method for producing the cross-sectional shape of FIG. 1 (A) is shown.

【0080】

For example, the resist film is patterned on the insulating film, the insulating film is isotropically etched, and then the resist film is removed. After that, when the insulating film is etched by RIE (Reactive Ion Etching), the reactive gas easily hits the portion where the side surface and the upper surface of the insulating film are in contact, so that the vicinity of the tangent line between the side surface and the upper surface of the insulating film is curved. be able to.

【0081】

This process will be described with reference to FIG. FIG. 19 is a cross-sectional view illustrating a process of forming a bump.

【0082】

First, an insulating film 324 is formed on the electrodes, and a resist film 325 is formed on the insulating film 324. The thickness of the insulating film shall be 1 to 3 μm, and the thickness of the resist film shall be 0.5 to 5 μm. The insulating film is formed by applying a polyimide resin film or an acrylic resin film and thermosetting it (Fig. 19 (A)).

【0083】

Next, the resist film is exposed and developed. The resist film 327 is formed so as to overlap the end portion of the pixel electrode and the gap between the adjacent pixel electrodes. The insulating film is then isotropically etched. A known method may be used as the isotropic etching process. For example, when etching is performed by generating plasma, it is known that etching proceeds isotropically when the atmospheric pressure for etching is increased (practical dry etching technology REALIZE INC. P.40). The insulating film below the edge of the resist film is scraped by etching, leaving the insulating film 326 with a curved side surface (Fig. 19 (B)).

【0084】

Then, the resist film is removed (Fig. 19 (C)).

【0085】

Next, the insulating film is etched by the RIE (Reactive Ion Etching) method. A plasma with an ionization degree of 0.1 to 1% is formed at an atmospheric pressure of 0.1 to 1 Torr. In the etching using the RIE method, the reactive gas and the insulating film chemically react with each other to proceed with the etching. Since the reactive gas easily hits the portion where the side surface and the upper surface of the insulating film are in contact (the upper end portion 329 of the insulating film), the upper end portion of the insulating film 328 has a rounded shape (FIG. 19 (D)).

【0086】

Next, the EL film 423 and the cathode 424 are formed (FIG. 19 (E)).

【0087】

Other examples of the method for producing the cross-sectional shape of FIG. 1 (A) or FIG. 1 (B) are shown.

【0088】

Figure 7 (A) shows the manufacturing method when a photosensitive organic material is used as the insulating film. By exposing the photosensitive material and etching it with a developing solution, the cross-sectional shape can be made smooth. As the organic material, a photosensitive polyimide resin film and a photosensitive acrylic film can be used. It is preferable to use a positive type as the photosensitive organic material.

【0089】

For example, a photosensitive polyimide resin film 316 is applied to a thickness of 1.0 to 3.0 μm and heat-treated at a temperature of 50 ° C to 150 ° C for 1 to 5 minutes to obtain a photosensitive polyimide resin. Remove the solvent contained in the membrane. Then, the photosensitive polyimide resin film is exposed by irradiating the quartz glass 314 with ultraviolet rays 313 through a photomask in which the chromium film 315 is formed (FIG. 7 (A)).

【0090】

In the present invention, the ultraviolet rays that have passed through the photomask are diffracted on purpose during exposure. In a normal exposure device, the light that has passed through the photomask spreads due to diffraction. Therefore, by incident the light spread by diffraction into the lens and arranging the substrate at the focal point of the lens, a photosensitive polyimide resin on the substrate is used. The photomask pattern is accurately transferred to the film. However, in the present invention, when the photosensitive polyimide resin film is exposed, the substrate is intentionally placed about 0.05 to 30 μm below the focal position of the lens. Then, the light that has passed through the photomask and spread by diffraction is irradiated to the photosensitive polyimide resin film. The light (ultraviolet rays 313) irradiated to the photosensitive resin penetrates into the inside of the chromium film 315 formed on the photomask by diffraction.

【0091】

When the photosensitive polyimide resin film is exposed, it is possible to obtain a cross-sectional shape having a gentle curved surface by positively utilizing diffraction. The cross section of the insulating film 317 after development has a shape that reflects the intensity distribution of the diffracted light at the time of exposure. By adjusting the exposure and development conditions, the surface of the insulating film can be made into a gentle shape. After development, the insulating film 317 is baked and thermoset. (Fig. 7 (B)). Further, when the photosensitive resin film is exposed, the diffracted light is incident on the surface of the photosensitive resin in the portion shielded by the photomask, so that not only the cross-sectional shape shown in FIG. 1 (A) but also the cross-sectional shape shown in FIG. The cross-sectional shape of 1 (B) can also be produced.

【0092】

After that, an EL film 423 and a cathode 424 are formed on the insulating film by vapor deposition (Fig. 7 (C)).

【0093】

The above-mentioned etching method can also be used when forming a contact hole in an insulating film in a display device such as an EL display device or a liquid crystal display device.

【0094】

The shape of the cross section of the bump produced by the above embodiment can be easily confirmed by cutting the substrate on which the bump is formed and observing the cross section with a field emission scanning electron microscope (SEM). it can.

【0095】

Hereinafter, the EL display device using the present invention will be specifically described with reference to Examples.

【0096】

[Example]

[Example 1] The present invention can be applied to any display device using an EL element. FIG. 8 shows an example of this, and shows an example of an active matrix type display device manufactured using a TFT. TFTs may be distinguished from amorphous silicon TFTs and polysilicon TFTs depending on the material of the semiconductor film forming the channel formation region, and the present invention can be applied to either of them.

【0097】

FIG. 8 shows a state in which an n-channel type TFT 452 and a p-channel type TFT 453 are formed in the drive circuit unit 450, and a switching TFT 454 and a current control TFT 455 are formed in the pixel unit 451. These TFTs are formed by using island-shaped semiconductor layers 403 to 406, a gate insulating film 407, gate electrodes 408 to 411, and the like.

【0098】

As the substrate 401, a substrate made of barium borosilicate glass typified by Corning's # 7059 glass or # 1737 glass, or glass such as aluminoborosilicate glass is used. As the substrate 401, a quartz substrate, a silicon substrate, a metal substrate, or a stainless steel substrate on which an insulating film is formed may be used. Further, a plastic substrate having heat resistance that can withstand the processing temperature of this example may be used.

【0099】

As the base film 402, an insulating film such as a silicon oxide film, a silicon nitride film, or a silicon nitride film can be used. In this embodiment, a two-layer structure is used as the base film 402, but a single-layer film of the insulating film or a structure in which two or more layers are laminated may be used.

【0100】

The interlayer insulating film is composed of an inorganic insulating film 418 formed of silicon nitride, silicon oxide or the like, and an organic insulating film 419 formed of an acrylic resin film or a polyimide resin film.

【0101】

The circuit configuration of the drive circuit unit 450 differs between the gate signal side drive circuit and the data signal side drive circuit, but will be omitted here. Wiring 412 and wiring 413 are connected to the n-channel type TFT 452 and the p-channel type TFT 453, and a shift register, a latch circuit, a buffer circuit, etc. are formed by using these TFTs.

【0102】

In the pixel section 451 the data wiring 414 is connected to the source side of the switching TFT 454, and the wiring 415 on the drain side is connected to the gate electrode 411 of the current control TFT 455. Further, the source side of the current control TFT 455 is connected to the power supply wiring 417, and the electrode 416 on the drain side is wired so as to be connected to the cathode of the EL element. FIG. 9A shows a top view of such pixels, and for convenience, the reference numerals common to those in FIG. 8 are used. Further, in FIG. 9A, a cross section corresponding to the line AA'is shown in FIG.

【0103】

The EL element 456 is composed of a cathode 424 formed of a material such as MgAg or LiF, an EL film 423 made of an organic EL material, and an anode 422 formed of ITO (indium tin oxide). ing. The bumps 420 and 421 are formed so as to cover the end of the anode 422. The bump prevents a short circuit between the cathode and the anode and disconnection of the cathode 424.

【0104】

The bump is formed by using an insulating film such as an acrylic resin film or a polyimide resin film so as to cover the wiring of the TFT element. In this embodiment, a photosensitive polyimide resin film is used as the bump. Diffraction when exposing a photosensitive polyimide resin film is positively utilized to form a gentle curved surface on the surface of the photosensitive resin film. Diffraction is caused by adjusting the optical system of the exposure device.

【0105】

The material forming the EL film may be either a low molecular weight material or a high molecular weight material. When a low molecular weight material is used, a vapor deposition method is used, but when a polymer material is used, a spin coating method, a printing method, an inkjet method, or the like is used.

【0106】

As the polymer-based material, a π-conjugated polymer material and the like are known. Typical examples thereof include crystalline semiconductor film paraphenylene vinylene (PPV) type, polyvinylcarbazole (PVK) type, and polyfluorene type. The EL film formed by using such a material is used in a single layer or a laminated structure, but the luminous efficiency is better when used in a laminated structure. Generally, a hole injection layer / a hole transport layer / a light emitting layer / an electron transport layer are formed on the anode in this order, but a hole transport layer / a light emitting layer / an electron transport layer or a hole injection layer / a hole. The structure may be such as a transport layer / light emitting layer / electron transport layer / electron injection layer. In the present invention, any known structure may be used, or the EL film may be doped with a fluorescent dye or the like.

【0107】

As the organic EL material, for example, the materials disclosed in the following US patents or publications can be used. US patent 4,356,429, US patent 4,539,507, US patent 4,720,432, US patent 4,769,292, US patent 4,885,211, US patent 4,950,950, US patent 5,059,861, US patent 5,047,687, US patent No. 5,073,446, U.S. Patent No. 5,059,862, U.S. Patent No. 5,061,617, U.S. Patent No. 5,151,629, U.S. Patent No. 5,294,869, U.S. Patent No. 5,294,870, Japanese Patent Application Laid-Open No. 10-189525, Japanese Patent Application Laid-Open No. 8-241048, Japanese Patent Application Laid-Open No. 8-78159.

【0108】

There are roughly four methods for color display. A method for forming three types of EL elements corresponding to R (red), G (green), and B (blue), and a combination of a white light emitting EL element and a color filter. Method, a method that combines an EL element that emits blue or blue-green light and a phosphor (fluorescent color conversion layer: CCM), a method that uses a transparent electrode on the cathode (opposite electrode) and superimposes an EL element that supports RGB. There is.

【0109】

As a specific EL film, cyanopolyphenylene may be used for the EL film that emits red light, polyphenylene vinylene may be used for the EL film that emits green light, and polyphenylene vinylene or polyalkylphenylene may be used for the EL film that emits blue light. The thickness of the EL film may be 30 to 150 nm.

【0110】

The above example is an example of an organic EL material that can be used as a light emitting layer, and is not limited thereto. The materials for forming the light emitting layer, the charge transport layer, and the charge injection layer can be freely selected in the possible combinations. The EL film shown in this example has a structure in which a light emitting layer and a hole injection layer composed of PEDOT (polythiophene) or PAni (polyaniline) are provided.

【0111】

A cathode 424 of the EL element is provided on the EL film 423. As the cathode 424, a material containing magnesium (Mg), lithium (Li) or calcium (Ca) having a small work function is used. Preferably, an electrode made of MgAg (a material obtained by mixing Mg and Ag at Mg: Ag = 20: 1) may be used. Other examples include MgAgAl electrode, LiAl electrode, and LiFAl electrode.

【0112】

After forming the EL film 423, the cathode 424 is preferably formed continuously without being released to the atmosphere. This is because the interface state between the cathode 424 and the EL film 423 greatly affects the luminous efficiency of the EL element. In the present specification, a light emitting element formed of an anode (pixel electrode), an EL film, and a cathode is referred to as an EL element.

【0113】

The laminate consisting of the EL film 423 and the cathode 424 needs to be formed individually for each pixel, but since the EL film 423 is extremely sensitive to moisture, ordinary photolithography technology cannot be used. In addition, the cathode 424 made of alkali metal is easily oxidized. Therefore, it is preferable to use a physical mask material such as a metal mask and selectively form it by a vapor phase method such as a vacuum vapor deposition method, a sputtering method, or a plasma CVD method. Although it is possible to use an inkjet method, a screen printing method, or the like as a method for selectively forming the EL film, it can be said that the above-mentioned method is preferable because continuous formation of cathodes is not possible at present.

【0114】

Further, a protective electrode for protecting from external moisture or the like may be laminated on the cathode 424. As the protective electrode, it is preferable to use a low resistance material containing aluminum (Al), copper (Cu) or silver (Ag). Alternatively, by using a transparent electrode, light can be emitted in the direction indicated by the arrow in FIG. 8 (this is referred to as top emission for convenience). In that case, if a black pigment is mixed with the organic resin interlayer insulating film 419, a black screen can be formed when no light is emitted without using a polarizing plate. This protective electrode can also be expected to have a heat dissipation effect that alleviates the heat generated by the EL film. It is also effective to form the EL film 423 and the cathode 424, and then continuously form the protective electrodes without releasing them to the atmosphere.

【0115】

As shown in FIG. 17, a transparent conductive film is formed as an anode 1101 on an organic resin interlayer insulating film 1100 mixed with a black pigment, and bumps 1102 and EL film 1103 made of an insulating film are formed. Furthermore, LiFAl and MgAg are formed as the cathode 1104 with a thickness of 10 to 50 nm to provide light transmission. A transparent conductive film 1105 is formed on the cathode for the purpose of further reducing the wiring resistance. As a result, in FIG. 17, light can be emitted in the direction indicated by the arrow. At this time, since the cathode has light transmission property, it is possible to suppress glare of the display screen when the light is not emitted.

【0116】

In FIG. 8, the switching TFT 454 has a multi-gate structure, and the current control TFT 455 is provided with an LDD that overlaps with the gate electrode. Since TFTs using polysilicon show high operating speed, deterioration such as hot carrier injection is likely to occur. Therefore, it is highly reliable and reliable to form TFTs (switching TFTs with sufficiently low off-current and current control TFTs that are strong against hot carrier injection) having different structures depending on the function in the pixel. It is very effective in producing a display device capable of displaying a good image (high operating performance).

【0117】

FIG. 9B is a circuit diagram of the pixels shown in FIGS. 8 and 9 (A). Pixels are arranged near the intersection of the gate wiring and the data wiring, and the pixels are provided with a switching TFT 454, a current control TFT 455, and an EL element 456.

【0118】

The gate electrode of the switching TFT 454 is connected to the gate wiring 410. The source side of the switching TFT is connected to the data wiring 414, and the drain side is connected to one of the gate electrode of the current control TFT 455 and the capacitor 458. The other electrode of the capacitor is connected to power supply line 417. The source side of the current control TFT is connected to the power supply line 417, and the drain side of the current control TFT is connected to the EL element 456.

【0119】

Reference numeral 457 is a TFT for controlling the current of adjacent pixels. The source side of the current control TFT 457 is connected to the power supply line 417. Since a common power supply line 417 can be used for adjacent pixels, the aperture ratio can be increased.

【0120】

FIG. 12 is a diagram showing the appearance of such a display device. The direction in which the image is displayed differs depending on the configuration of the EL element, but here, light is emitted upward to display the image. In the configuration shown in FIG. 12, the element substrate 601 and the sealing substrate 602 on which the drive circuit unit 604, the drive circuit unit 605, and the pixel unit 603 are formed by using the TFT are bonded to each other by the sealing material 610. An input terminal 608 is provided at the end of the element board 601 and an FPC (Flexible Print Circuit) is connected to this portion. The input terminal 608 is provided with terminals for inputting image data signals, various timing signals, and a power source from an external circuit at a pitch of 500 μm. Then, it is connected to the drive circuit unit by wiring 609. Further, if necessary, the IC chip 607 in which the CPU, memory, etc. are formed may be mounted on the element substrate 601 by the COG (Chip on Glass) method or the like.

【0121】

As shown in FIG. 11, the input terminal is formed by laminating a wiring 705 made of titanium (Ti) and aluminum (Al) and an ITO 706 formed as an anode. FIG. 11 shows a cross-sectional view corresponding to the C-C'line at the input terminal portion. The element substrate 701 and the sealing substrate 702 are bonded together with a sealing material 703. In the drive circuit section, the EL film 707 and the cathode 708 are formed on the bump 709, and a contact section 720 as shown in the figure is provided to contact the cathode 708 with the wiring. Since the side surface of the bump also has a gentle curved surface in the contact portion 720, it is possible to prevent disconnection of the cathode layer.

【0122】

In a display device using such an EL element, since the side surface of the bump has a gentle curved surface, it is possible to prevent disconnection of the EL film and the cathode and increase the yield of the display device.

【0123】

[Example 2] FIG. 13 shows an example of a display device using an inverted staggered TFT. The substrate 501 and the EL element 556 to be used have the same configuration as that of the first embodiment, and the description thereof will be omitted here.

【0124】

The inverted staggered TFT is formed in the order of the gate electrodes 508 to 511, the gate insulating film 507, and the semiconductor films 503 to 506 from the substrate 501 side. In FIG. 13, an n-channel type TFT 552 and a p-channel type TFT 553 are formed in the drive circuit unit 550, and a switching TFT 554, a current control TFT 555, and an EL element 556 are formed in the pixel unit 551. The interlayer insulating film is composed of an inorganic insulating film 518 formed of silicon nitride, silicon oxide or the like, and an organic resin film 519 formed of acrylic or polyimide.

【0125】

The circuit configuration of the drive circuit unit 550 differs between the gate signal side drive circuit and the data signal side drive circuit, but will be omitted here. Wiring 512 and wiring 513 are connected to the n-channel type TFT552 and the p-channel type TFT553, and a shift register, a latch circuit, a buffer circuit, etc. are formed by using these TFTs.

【0126】

In the pixel portion 551, the data wiring 514 is connected to the source side of the switching TFT 554, and the wiring 515 on the drain side is connected to the gate electrode 511 of the current control TFT 555. Further, the source side of the current control TFT 555 is connected to the power supply wiring 517, and the electrode 516 on the drain side is wired so as to be connected to the anode of the EL element.

【0127】

Then, bumps 520 and 521 are formed by using an organic resin such as acrylic or polyimide, preferably a photosensitive organic resin so as to cover these wirings. By positively utilizing diffraction when exposing a photosensitive resin, the bump can have a curved surface shape with a gentle side surface. The EL element 556 is composed of an anode 522 formed of ITO (indium tin oxide), an EL film 523 made of an organic EL material, and a cathode 524 formed of a material such as MgAg or LiF. There is. The bumps 520 and 521 are formed so as to cover the end portion of the anode 522 and prevent the cathode and the anode from being short-circuited.

【0128】

The anode 522 is made of a transparent electrode, and the cathode 524 is made of a metal material containing magnesium (Mg), lithium (Li) or calcium (Ca), which has a small work function. Light is emitted in the indicated direction. The direction of light emission can be arbitrarily determined depending on whether or not the cathode has light reflectivity.

【0129】

In addition, if the structure of the TFT is omitted, the configuration of the pixel portion and the configuration of the display device are the same as those in the first embodiment. The inverted staggered TFT using polysilicon has an advantage that it can be manufactured by diverting the production line of the amorphous silicon TFT (usually formed by the inverted staggered TFT). Of course, if a laser annealing technique using an excimer laser is used, a polysilicon TFT can be manufactured even at a process temperature of 300 ° C or less.

【0130】

[Example 3] An example of an electronic device using the display device shown in the first embodiment will be described with reference to FIG. In the display device of FIG. 14, a pixel portion 921 composed of pixels 920, a data signal side drive circuit 915 used for driving the pixel portions, and a gate signal side drive circuit 914 are formed by a TFT formed on a substrate. The data signal side drive circuit 915 shows an example of digital drive, and is composed of a shift register 916, a latch circuit 917, 918, and a buffer circuit 919. Further, the gate signal side drive circuit 914 has a shift register, a buffer and the like (none of which are shown).

【0131】

In the case of VGA, the pixel unit 921 has 640 × 480 (horizontal × vertical) pixels, and as described with reference to FIG. 8 or 9, a switching TFT and a current control TFT are arranged in each pixel. ing. As for the operation of the EL element, when the gate wiring is selected, the gate of the switching TFT opens, the data signal of the source wiring is accumulated in the capacitor, and the gate of the current control TFT opens. That is, a current flows through the current control TFT by the data signal input from the source wiring, and the EL element emits light.

【0132】

The system block diagram shown in FIG. 14 shows the form of a portable information terminal such as a PDA. The display device shown in the first embodiment is formed with a pixel unit 921, a gate signal side drive circuit 914, and a data signal side drive circuit 915.

【0133】

The configuration of the external circuit connected to this display device is a power supply circuit 901 consisting of a regulated power supply and a high-speed, high-precision operational amplifier, an external interface port 902 equipped with a USB terminal, a CPU 903, a pen input tablet 910 used as an input means, and detection. It consists of circuit 911, clock signal oscillator 912, control circuit 913, and so on.

【0134】

The CPU 903 has a built-in video signal processing circuit 904 and a tablet interface 905 that inputs signals from the pen input tablet 910. Further, VRAM906, DRAM907, flash memory 908 and memory card 909 are connected. The information processed by the CPU 903 is output from the video signal processing circuit 904 to the control circuit 913 as a video signal (data signal). The control circuit 913 has a function of converting the video signal and the clock into the timing specifications of the data signal side drive circuit 915 and the gate signal side drive circuit 914, respectively.

【0135】

Specifically, the function of distributing the video signal to the data corresponding to each pixel of the display device, and the timing of converting the horizontal synchronization signal and the vertical synchronization signal input from the outside into the start signal of the drive circuit and the AC of the built-in power supply circuit. It has a function to convert it into a control signal.

【0136】

It is desired that portable information terminals such as PDAs can be used outdoors or in trains for a long time by using a rechargeable battery as a power source without connecting to an AC outlet. Further, such an electronic device is required to be lightweight and miniaturized at the same time with an emphasis on portability. Batteries, which account for most of the weight of electronic devices, increase in weight as the capacity is increased. Therefore, in order to reduce the power consumption of such an electronic device, it is necessary to take measures from the software side such as controlling the lighting time of the backlight and setting the standby mode.

【0137】

For example, when the input signal from the pen input tablet 910 does not enter the tablet interface 905 for a certain period of time with respect to the CPU 903, the standby mode is set and the operation of the portion surrounded by the dotted line in FIG. 14 is synchronized and stopped. In the display device, the emission intensity of the EL element is attenuated, or the image display itself is stopped. Alternatively, a memory is provided for each pixel, and measures such as switching to a still image display mode are taken. In this way, the power consumption of the electronic device is reduced.

【0138】

Further, in order to display a still image, functions such as the video signal processing circuit 904 and VRAM906 of the CPU 903 can be stopped to reduce power consumption. In FIG. 14, the part where the operation is performed is indicated by a dotted line. Further, as shown in FIG. 12, the controller 913 may be mounted on the element substrate by the COG method using an IC chip, or may be integrally formed inside the display device.

【0139】

[Example 4] In this example, an organic compound that emits light by a singlet exciter (singlet) as an EL film (hereinafter referred to as a singlet compound) and an organic compound that emits light by a triplet excitator (triplet) (hereinafter, triplet compound). An example of using together with) will be described. The singlet compound refers to a compound that emits light only via singlet excitation, and the triplet compound refers to a compound that emits light via triplet excitation.

【0140】

As the triplet compound, the organic compounds described in the following papers can be mentioned as typical materials. (1) T.Tsutsui, C.Adachi, S.Saito, Photochemical Processes in Organized Molecular Systems, ed.K.Honda, (Elsevier Sci.Pub., Tokyo, 1991) p.437. (2) MABaldo, DFO' Brien, Y.You, A.Shoustikov, S.Sibley, METhompson, SRForrest, Nature 395 (1998) p.151. This paper discloses an organic compound represented by the following formula. (3) MABaldo, S.Lamansky, PEBurrrows, METhompson, SRForrest, Appl.Phys.Lett., 75 (1999) p.4. (4) T.Tsutsui, M.-J.Yang, M.Yahiro, K. Nakamura, T.Watanabe, T.tsuji, Y.Fukuda, T.Wakimoto, S.Mayaguchi, Jpn.Appl.Phys., 38 (12B) (1999) L1502. [0141]

Further, it is considered that not only the luminescent material described in the above paper but also the luminescent material represented by the following molecular formula (specifically, a metal complex or an organic compound) can be used.

【0142】

[Chemical 1]

<img file="JP2002164181A_D0001.tif" />【0143】

[Chemical 2]

<img file="JP2002164181A_D0002.tif" />【0144】

In the above molecular formula, M is an element belonging to groups 8 to 10 of the periodic table. Et is an ethyl group. In the above paper, platinum and iridium are used. Further, the present inventor considers that nickel, cobalt or palladium is preferable in reducing the manufacturing cost of the light emitting device because it is cheaper than platinum or iridium. In particular, nickel is considered to be preferable because it easily forms a complex and therefore has high productivity.

【0145】

The triplet compound has higher luminous efficiency than the singlet compound, and the operating voltage (voltage required to cause the EL element to emit light) can be lowered to obtain the same luminous brightness. This feature is used in this embodiment.

【0146】

When a low-molecular-weight organic compound is used as the light-emitting layer, the life of the light-emitting layer that emits red light is currently shorter than that of the light-emitting layer that emits light in other colors. This is because the luminous efficiency is inferior to that of other colors, so that the operating voltage must be set high in order to obtain the same luminous brightness as other colors, and the deterioration progresses faster accordingly.

【0147】

However, in this embodiment, since a triplet compound having high luminous efficiency is used as the light emitting layer that emits red light, the operating voltage is made uniform while obtaining the same emission brightness as that of the light emitting layer that emits green light or the light emitting layer that emits blue light. It is possible. Therefore, the deterioration of the light emitting layer that emits red light does not become extremely accelerated, and color display can be performed without causing problems such as color shift. Further, it is preferable that the operating voltage can be suppressed low from the viewpoint that the margin of withstand voltage of the transistor can be set low.

【0148】

In the present embodiment, although an example of using a triplet compound as a light-emitting layer that emits red light, further outgoing green it is also possible to use a light-emitting layer to light or triplet compound in the light emitting layer that emits blue light is there.

【0149】

In the case of RGB color display, it is necessary to provide an EL element that emits red light, an EL element that emits green light, and an EL element that emits blue light in the pixel portion. In this case, it is also possible to use a triplet compound for the EL element that emits red light, and use a singlet compound for the others.

【0150】

By properly using the triplet compound and the singlet compound in this way, it is possible to make the operating voltage of each EL element the same (20 V or less, preferably 3 to 20 V). Therefore, since the power supply required for the display device can be unified to, for example, 3V or 5V, there is an advantage that the circuit design becomes easy. The configuration of this embodiment can be implemented in combination with any of the configurations of Examples 1 to 3.

【0151】

[Example 5] The display device formed by carrying out the present invention is built in various electric appliances, and the pixel unit is used as an image display unit. Examples of the electronic device of the present invention include a mobile phone, a PDA, an electronic book, a video camera, a notebook personal computer, an image playback device including a recording medium, for example, a DVD (Digital Versatile Disc) player, a digital camera, and the like. Specific examples of these electronic devices are shown in FIGS. 15 and 16.

【0152】

Fig. 15 (A) shows a mobile phone, which consists of a display panel 9001, an operation panel 9002, and a connection unit 9003. The display panel 9001 is provided with a display device 9004, an audio output unit 9005, an antenna 9009, and the like. .. The operation panel 9002 is provided with an operation key 9006, a power switch 9007, a voice input unit 9008, and the like. The present invention can be applied to the display device 9004.

【0153】

FIG. 15B is also a mobile phone, which includes a main body or a housing 9101, a display device 9102, a voice output unit 9103, a voice input unit 9104, and an antenna 9105. The display device 9102 may incorporate a touch-type sensor so that buttons can be operated on the screen. In the present invention, when a display device in which a TFT element and an EL element are formed on a plastic substrate is used, it is possible to bend the substrate after the display device is completed. Taking advantage of these characteristics, it can be incorporated into a housing having a three-dimensional curved surface designed based on ergonomics without any discomfort.

【0154】

FIG. 15C shows a mobile computer or a portable information terminal, which is composed of a main body 9201, a camera unit 9202, an image receiving unit 9203, an operation switch 9204, and a display device 9205. The present invention can be applied to the display device 9205. A 3-inch to 5-inch class display device is used for such an electronic device, and the weight of the portable information terminal can be reduced by using the display device of the present invention.

【0155】

Figure 15 (D) is a portable book, which consists of a main unit 9301, a display device 9303, a storage medium 9304, an operation switch 9305, and an antenna 9306. It displays the received data. The present invention can be used in the display device 9303. A 4-inch to 12-inch class display device is used for a portable book, and by using the display device of the present invention, it is possible to reduce the weight and thickness of the portable book.

【0156】

FIG. 15 (E) shows a video camera, which is composed of a main body 9401, a display device 9402, an audio input unit 9403, an operation switch 9404, a battery 9405, and the like. The present invention can be applied to the display device 9402.

【0157】

FIG. 16A shows a personal computer, which is composed of a main body 9601, an image input unit 9602, a display device 9603, and a keyboard 9604. The present invention can be applied to the display device 9603.

【0158】

FIG. 16B is a player that uses a recording medium (hereinafter referred to as a recording medium) on which a program is recorded, and is composed of a main body 9701, a display device 9702, a speaker unit 9703, a recording medium 9704, and an operation switch 9705. This device uses a DVD (Digital Versatile Disc), a CD, or the like as a recording medium, and can perform music listening, movie viewing, games, and the Internet. The present invention can be applied to the display device 9702.

【0159】

FIG. 16C shows a digital camera, which is composed of a main body 9801, a display device 9802, an eyepiece 9803, an operation switch 9804, and an image receiving unit (not shown). The present invention can be applied to the display device 9802.

【0160】

Fig. 16 (D) is also a digital camera, which consists of a main body 9901, a display device 9902, an image receiving unit 9903, an operation switch 9904, a battery 9905, and the like. The present invention can be applied to the display device 9902. By using the organic resin substrate of the present invention, it is possible to bend the substrate after the display device is completed. Taking advantage of these characteristics, it can be incorporated into a housing having a three-dimensional curved surface designed based on ergonomics without any discomfort.

【0161】

Further, in the mobile phone operation shown in FIGS. 15A and 15B, the power consumption can be reduced by increasing the brightness when using the operation keys and decreasing the brightness when the operation switch is used up. .. Further, the power consumption can be reduced by increasing the brightness of the display device when receiving an incoming call and decreasing the brightness during a call. In addition, when it is used continuously, it is possible to reduce power consumption by providing a function that turns off the display by time control unless it is reset. Note that these may be manually controlled.

【0162】

Although not shown here, the present invention can also be applied as a display device incorporated in a navigation system, a refrigerator, a washing machine, a microwave oven, a fixed telephone, a facsimile, and the like. As described above, the scope of application of the present invention is extremely wide, and it can be applied to various products.

【0163】

[Effect of the invention]

As described above, by using the present invention, in a display device using an EL element, the uniformity of the film thickness of the EL film and the cathode formed by forming the side surface of the bump on the electrode into a curved shape is improved. As a result, disconnection of the EL film and the cathode can be prevented, the yield of the EL element can be increased, and the display quality can be improved.

[Simple explanation of drawings]

[Figure 1]

The cross-sectional view explaining the cross section of the EL element in this invention.

[Figure 2]

The cross-sectional view explaining the cross section of the bump in this invention.

[Fig. 3]

The cross-sectional view explaining the cross section of the bump in this invention.

[Fig. 4]

FIG. 5 is a cross-sectional view (embodiment) for explaining the bump manufacturing process of the present invention.

[Fig. 5]

FIG. 5 is a cross-sectional view (embodiment) for explaining the bump manufacturing process of the present invention.

[Fig. 6]

FIG. 5 is a cross-sectional view (embodiment) for explaining the bump manufacturing process of the present invention.

[Fig. 7]

FIG. 5 is a cross-sectional view (embodiment) for explaining the bump manufacturing process of the present invention.

[Fig. 8]

FIG. 5 is a cross-sectional view for explaining the configuration of a drive circuit and a pixel portion of a display device (Example 1).

[Fig. 9]

A top view and an equivalent circuit diagram for explaining the configuration of the pixel portion of the display device (Example 1).

[Fig. 10]

The figure explaining the structure of the input terminal part of a display device (Example 1).

[Fig. 11]

The figure explaining the structure of the input terminal part of a display device (Example 1).

[Fig. 12]

The perspective view which shows the appearance of the EL display device of this invention (Example 1).

[Fig. 13]

FIG. 2 is a cross-sectional view for explaining the configuration of a drive circuit and a pixel portion of a display device (Example 2).

[Fig. 14]

A system block diagram of an electronic device having a built-in display device (Example 3).

[Fig. 15]

The figure explaining an example of an electronic device (Example 5).

[Fig. 16]

The figure explaining an example of an electronic device (Example 5).

[Fig. 17]

The figure which shows the radiation direction of the light of an EL element (Example 1).

[Fig. 18]

The figure explaining the shape of the bump of the conventional example.

[Fig. 19]

FIG. 5 is a cross-sectional view (embodiment) for explaining the bump manufacturing process of the present invention.

[Fig. 20]

The figure explaining the shape of the bump of this invention.