JP2002164181A - Display device and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology of preventing breakage of EL membrane, by suppressing the thickness of the EL membrane becoming thin locally at the part interposed between the negative electrode and positive electrode, and by preventing the electric field from concentrating locally on the EL membrane. SOLUTION: In the EL element in which an insulating membrane 101 is formed on a positive electrode 100, and an EL membrane 102 and a negative electrode 103 are formed on the insulating membrane 101, the bottom end part and top end part of the insulating membrane 101 are made a curved-shape. And the taper angle at the center of the insulating membrane 101 is made 35o or more and 700 or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electroluminescence (Electroluminescence).
e: a display device including an element (hereinafter, referred to as “EL element”) in which a thin film (hereinafter, referred to as “EL film”) formed of a compound capable of obtaining an EL is sandwiched between electrodes, and a method for manufacturing the same. .

[0002] EL has phosphorescence (phosphporescenc) emitted when a transition from a triplet excited state to a ground state occurs.
e) and fluorescence emitted when transitioning from the singlet excited state to the ground state.

The EL film can be made of an inorganic material or an organic material. The organic EL film uses an organic material as the EL film. An organic EL element is an EL element in which an organic EL film is interposed between electrodes.

In the present specification, the thin film transistor (TF)
T) Element refers to a semiconductor element 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 wirings.

[0005]

2. Description of the Related Art A display device using an organic EL film can be made lighter and thinner than a conventional CRT, and is being applied to various uses. Mobile phones and personal digital assistants (PDAs) for personal use can be connected to the Internet, and the amount of information shown on the video display increases dramatically. The demand for conversion is increasing.

[0006] As a means for increasing the definition of a display device, an active element such as a thin film transistor (TFT) is used.
Means for applying a voltage to the film is employed.

Further, a display device in which a pixel portion is formed by EL elements is a self-luminous type and does not require a light source such as a backlight unlike a liquid crystal display device, so that it is promising as a means for realizing weight reduction and thinning. Have been watched.

[0008]

The EL device generally has a structure in which an EL film is formed on an anode formed for each pixel, and a cathode is formed as a common electrode on the EL film. However, since a thin EL film having a thickness of 30 nm to 150 nm is formed on an anode having a thickness of about 200 nm in order to reduce resistance, disconnection of the EL film occurs on a side surface of the anode. Was. When the EL film is disconnected, the anode and the cathode are short-circuited at the disconnected portion, and the EL film does not emit light, resulting in a black dot defect.

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

However, the cross-sectional structure shown in FIG. 18 has some problems in the actual process. As shown in FIG. 18, when the side surface of the insulating film 1001 on the anode 1000 is linear, disconnection of the EL film is likely to occur at 1004 where the upper surface of the anode and the side surface of the insulating film are in contact. That is, in a place where the inclination of the deposition surface of the EL film changes abruptly,
The L film 1002 is not deposited, leaving a gap. This gap causes a short circuit between the anode and the cathode. Even if the EL film is not disconnected, when the EL film is thin at 1004 where the upper surface of the anode and the side surface of the insulating film are in contact with each other, an electric field concentrates on the thinned portion of the EL film, and the EL film becomes thin. Light emission occurs only in the vicinity.

Further, when the cathode on the insulating film is electrically connected to the wiring under the insulating film through a 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. In some cases, no display is performed.

Further, in the vicinity 1005 of the tangent between the side surface of the insulating film 1001 and the upper surface of the insulating film, disconnection of the EL film and the cathode is likely to occur. Usually, an insulating film (bump) is formed in a stripe shape so as to cover a gap between adjacent pixels. At this time, when the bump is formed around the pixel, disconnection of the cathode occurs, and when the disconnections are continuously connected to form a closed curve, the cathode inside the closed curve has no function as an electrode, No voltage is applied to the EL film. That is, it becomes a point defect.

When the number of pixels is increased in order to increase the definition of a display device using an EL element, a point defect due to a short circuit between an anode and a cathode or a point defect due to a disconnection of a cathode causes a yield and a deterioration in display quality. And urgent action is required. In addition, the concentration of an electric field due to the local thinning of the EL film changes luminance of a defective pixel with respect to luminance of a non-defective pixel, thereby impairing visibility.
Measures are needed.

[0014]

Means for Solving the Problems By optimizing the shape of the bumps, the present inventors gradually change the inclination of the EL film and the cathode deposition surface on the bumps, and the EL film and the cathode are separated. We thought that it would be easier to form a film with a uniform film thickness, and that disconnection of the EL film and the cathode and local change in the film thickness of the EL film could be suppressed. Therefore, the shape of the bump was optimized so that the EL film and the cathode could be formed to a uniform film thickness and excellent display performance could be secured.

The terms used to indicate the shape of the bump in the present invention will be described below with reference to FIG. FIGS. 20A and 20B are examples of sectional views showing the shapes of bumps.

For example, in the case of a bump whose upper surface 107 is flat as shown in the cross-sectional view of FIG. 20A, both ends of the lower portion of the insulating film 101 are lower end portions 104, both ends of the upper portion of the insulating film are upper end portions 106, and A middle portion between the upper surface 107 of the film and the surface in contact with the upper surface of the anode 100 under the insulating film is a central portion 105.
That. The surface of the insulating film has a flat upper surface 107 and side surfaces 108.
It is divided into

For example, in the case of a bump having a curved upper portion as shown in the cross-sectional view of FIG. 20B, both ends of the lower portion of the insulating film 201 are lower end portions 204, and the vicinity of the thickest portion of the insulating film is near. Upper part 206, upper part 206 of the insulating film and anode 2 under the insulating film
The portion having a height in the middle of the surface in contact with the upper surface of 00 is referred to as a central portion 205.

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

In the present invention, the thickness (T) of the insulating film 101 refers to the thickness of the insulating film when used as a device. Further, the thickness (T) of the insulating film refers to a length of a perpendicular line lowered from an upper surface of the insulating film to a lower surface of the insulating film.

In order to prevent disconnection of the EL film 102 and the cathode 103, it is preferable that the thickness of the insulating film is not too large.
It is preferable that the thickness be not more than μm. 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.

(1) The present invention relates to an EL element, which has one electrode of the EL element, for example, an anode 100, and an insulating film 101 selectively formed on the anode, and an insulating film in contact with the upper surface of the anode. The lower end portion 104 is in contact with an ellipse or circle having a center outside the side surface of the insulating film, and the upper end portion 106 is continuous with the upper surface 107 of the insulating film, and has an ellipse or circle having a center inside the side surface 108 of the insulating film. (FIG. 2B). In this manner, when the lower end and the upper end of the insulating film are formed in a smooth shape, the inclination of the film formation surface changes continuously, so that disconnection of the EL film 102 and the cathode 103 can be prevented. In addition, it is possible to prevent the thickness of the EL film from being locally reduced at a portion sandwiched between the cathode and the anode, and to prevent the electric field from being locally concentrated on the EL film.

The center of the ellipse is the intersection of the minor axis and the major axis of the ellipse. The center of the circle refers to an intersection point where at least three or more perpendicular lines to the tangent line of the circle are provided at different positions in the circle.

(2) In addition to the above configuration (1), the side surface where the center part 105 of the insulating film forms an angle θ between the surface contacting the side surface of the insulating film and the upper surface of the anode is 35 ° or more and 70 ° or less. With this, disconnection of the EL film and the cathode on the side surface 108 of the insulating film can be prevented. In this specification,
The “central portion” refers to a portion of the insulating film 101 having a height that is 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, hereinafter, a surface in contact with a side surface of an insulating film is referred to as an “inclined surface”.
Called. The angle formed between the inclined surface and the upper surface of the anode is referred to as “taper angle of the inclined surface”.

The taper angle of the inclined surface at the center of the insulating film is preferably 35 ° or more and 70 ° or less. If the taper angle of the inclined surface exceeds 70 °, the 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 thickness of the insulating film (bump) tends to be reduced as the tapered angle of the inclined surface decreases. If the thickness of the insulating film is reduced, the parasitic capacitance between the TFT element below the insulating film and the cathode on the insulating film increases, which is not preferable.

(3) The present invention relates to an EL device,
It has one electrode of the 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 a curved side surface determined by a center of curvature (O1) and a first radius of curvature (R1) above a tangent line between the anode and the lower end portion. Then, the upper end portion 106 of the insulating film is continuous with the upper surface of the insulating film,
It has a curved side surface determined by the center of curvature (O2) and the second radius of curvature (R2) below the boundary between the upper end portion 106 and the flat upper surface 107 (FIGS. 2A and 2B). .

Since the lower end of the insulating film has a gentle curved surface shape in which the inclination of the deposition surface of the EL film continuously changes, the coverage of the EL film formed at the lower end of the insulating film is improved. In addition, disconnection of the EL film at the lower end can be prevented. Thereby, the short circuit between the anode and the cathode due to the disconnection of the EL film is reduced. Further, it is possible to prevent the EL film from being partially thinned, and it is possible to prevent local concentration of an electric field in the EL film.

At the upper end 106 of the insulating film, the anode 10
The inclination of the surface in contact with the side surface of the insulating film is continuously changed with respect to the upper surface of the insulating film 0, so that the upper surface 107 and the
Disconnection of the EL film and the cathode near the boundary can be prevented. 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 point defect caused by the continuous disconnection of the cathode and forming a closed curve is prevented. Further, when the insulating film is provided in a stripe shape so as to cover part of the end of the anode, it is possible to prevent an increase in wiring resistance of the cathode due to disconnection of the cathode. Further, disconnection of the cathode at 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 can be suppressed.

(4) In addition to the above configuration (3), the present invention is characterized in that the first radius of curvature is not less than 0.2 μm and not more than 3.0 μm. If the first radius of curvature (R ₁ ) is less than 0.2 μm, the insulating film 1 in contact with the anode 100
01 has a steep side surface, the insulating film 101
In this case, there is a possibility that it is difficult to form the EL film and the cathode with a uniform film thickness. For example, since the inclination of the deposition surface of the EL film changes abruptly, the EL film becomes thinner, and an electric field is locally concentrated on that portion. On the other hand, if the first radius of curvature exceeds 3.0 μm, a portion where the thickness of the insulating film is small exists widely, and it becomes difficult to cover the TFT element with the insulating film.

Regardless of whether etching is performed using an aqueous solution of an acid or a base, or etching using a reactive gas,
When the radius of curvature is 0.2 μm or more and 3.0 μm or less, the shape can be easily controlled.

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

(6) In addition to the above (3), (4) and (5), the second radius of curvature (R ₂ ) is preferably 0.2 μm or more and 3.0 μm or less. If the second radius of curvature (R ₂ ) is too small, the side surface of the insulating film that is in contact with the upper surface of the insulating film 101 will be steep, so that even if the cross-sectional shape of the insulating film 101 is curved at the upper end, The effect of preventing disconnection of the EL film is low. For this reason, the second radius of curvature needs to be at least 0.2 μm or more.

Regardless of whether etching is performed using an aqueous solution of an acid or a base, or etching using a reactive gas, the second radius of curvature is 0.2 as a radius of curvature that can be controlled in an actual process.
It is appropriate that the thickness is not less than μm and not more than 3.0 μm.

By providing the radius of curvature or the inclination of the side surfaces of the lower end portion, the center portion and the upper end portion of the insulating film within the above numerical ranges, the side surface shape becomes gentle as a whole of the insulating film, and the EL film and the cathode are formed. It becomes easier to prevent disconnection. Further, concentration of an electric field due to local thinning of the EL film can be prevented on the side surface of the lower end portion of the insulating film.

FIG. 1B shows a structure capable of more effectively preventing disconnection of the cathode as compared with FIG. 1A. FIG. 1B shows that an insulating film 201 is selectively provided on an electrode, for example, an anode 200, and an insulating film 201 is formed on the insulating film 201.
A cathode 203 is formed on the L film 202 and the EL film.
FIG. 1B is characterized in that the side surfaces of the insulating film including the upper portion of the insulating film are curved.

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

The thickness (T) of the insulating film in FIG.
The term “length” 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 refers to a portion of 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 is preferably 3.0 μm or less.

(7) The present invention relates to an EL element, which comprises one electrode of the EL element, for example, an anode 200, and an insulating film 201 selectively formed on the anode, wherein the insulating film is in contact with the upper surface of the anode. The lower end portion 204 has a side surface in contact with an ellipse or circle having a center outside the side surface of the insulating film, and the upper end portion 206 has a side surface in contact with an ellipse or circle having a center inside the side surface of the insulating film. (FIG. 3B).

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

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

(10) In addition to the above configuration (9), the first radius of curvature (R ₁ ) of the lower end portion 204 is preferably 0.2 μm or more and 3.0 μm or less. If the first radius of curvature (R ₁ ) is too small, the side surface of the insulating film 201 that is in contact with the anode 200 becomes steep. Disconnection of membrane, E
The effect of preventing the L film from being locally thinned is low. For this reason, 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,
Since the region where the thickness of the insulating film is small exists widely, T
It becomes difficult to cover the FT element with the insulating film. Therefore, in the EL display device, there is a problem even if the first radius of curvature of the insulating film is too large. Therefore, the radius of curvature of the first insulating film is preferably set to 3.0 μm or less. In terms of process, the first radius of curvature (R ₁ ) is 0.2 μm or more.
If it is 0 μm or less, it can be sufficiently controlled in an actual process.

(11) The above (8), (9), (10)
In the present invention, in addition to the configuration of
The upper portion 206 of the insulating film is located at the center of curvature below the upper portion.
(O _Two) And a second center of curvature (R_TwoSurface shape determined by)
It is. Thus, the surface on which the EL film and the cathode are formed is
By making the change gently, the cathode
It is possible to prevent disconnection of the cathode due to thin film thickness.
it can. The second radius of curvature (R_Two) Are each other
The distance may be determined in consideration of the distance between the adjacent anodes. Figure
1 (B) and FIG. 3, the upper end portion 206 of the insulating film is bent.
Disconnection of the cathode layer due to sudden angle change by making it planar
Can be effectively prevented.

In FIGS. 2 to 3, the taper angle θ of the inclined surface from the lower end to the upper end (or upper part) of the side surface of the insulating film is 0 ° at the end of the insulating film where the electrode and the insulating film are in contact. 0 ° or more and 70 ° along the side surface of the insulating film
A shape that changes continuously in the following range is preferable because it can prevent disconnection of the EL film and the cathode and can prevent concentration of an electric field due to local thinning of the EL film.

When the above-mentioned EL film is an organic EL film formed of an organic material, DC driving and low voltage driving become possible, and a display device with low power consumption can be manufactured.

Although the description has been made mainly on the active matrix type display device, the present invention can be applied to either a passive matrix type or an active matrix type. Depending on the shape of the insulating film, disconnection of the cathode and EL film, E
This is because it is possible to effectively prevent the thickness of the L film from being locally reduced.

Further, the electrode under the insulating film has been described as an anode, but the electrode under the insulating film can be used as a cathode.

[0046]

Embodiments of the present invention will be described below.

First, a process using a non-photosensitive polyimide resin film and a non-photosensitive acrylic film as an organic material will be described. When etching the insulating film using a reactive gas, by gradually changing the flow ratio of the reactive gas,
The cross-sectional shape of the insulating film in FIG. 1A can be manufactured. One example of a manufacturing method is described below with reference to FIGS.

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

As a first step, an insulating film 301 is formed on these electrodes. Acrylic resin film,
It is possible to form a polyimide resin film. First,
An insulating film is applied on the substrate. Thereafter, 50 ° C to 150 ° C
At a temperature of 1 to 5 minutes to remove the solvent contained in the polyimide resin film. Further, the polyimide resin film is subjected to heat treatment at 200 ° C. to 250 ° C. in an oven to imidize the polyimide resin film. It is preferable that the thickness of the polyimide resin film after imidization be 1.0 μm or more and 3.0 μm or less.

As a second step, a resist film 300 is patterned on the insulating film 301. Photosensitive photoresist film on polyimide resin film (hereinafter referred to as resist film)
To form After patterning, the resist film 300 has a side surface of the resist film and a lower surface of the resist film of 50 ° to 80 °.
(FIG. 4A).

In a third step, the insulating film is etched using at least the first reactive gas and the second reactive gas. At this time, the flow ratio of the first reactive gas and the second reactive gas is changed with time. The first reactive gas CF ₄ , the second reactive gas O _2, and the inert gas H are used as etching gases.
A method for etching a polyimide resin film using e and e will be described. The larger the gas flow ratio of the first reactive gas CF ₄ , the more the polyimide resin film 3 compared to the resist film 302.
03 is easily etched. 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 of the resist film 302 recedes inside the resist film, and Y / X The taper angle of the inclined surface of the insulating film, which is determined depending on the temperature, increases. That is, if the gas flow ratio of the first reactive gas CF ₄ is large, the taper angle of the inclined surface is large, and the shape becomes sharp.

Conversely, when the gas flow ratio of the first reactive gas CF ₄ is small, the tapered angle of the inclined surface is small, and the shape becomes gently inclined.

Therefore, by gradually changing the flow ratio between the first reactive gas CF ₄ and the second reactive gas O ₂ , the taper angle of the inclined surface of the insulating film can be smoothly changed.

As a first etching step, RIE (R
The first reactive gas CF ₄ , the second reactive gas O ₂ , and the inert gas He are used as an etching gas by using an active ion etching method. When starting the etching, the gas flow ratio of CF ₄ , O ₂ and He is set to 1.
5 / 98.5 / 40 (sccm). Then, as the etching time advances, the gas flow ratio of the first reactive gas CF ₄ to the _second reactive gas O ₂ is increased with time, and finally the ratio of CF ₄ , O _2, and He is increased. The gas flow ratio is set to be 7/93/40 (sccm). First
By increasing the flow ratio of the reactive gas CF _4, the taper angle of the inclined surface of the insulating film is increased. 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 referred to as a first radius of curvature. The first radius of curvature is 0.2μ
It is preferable that the thickness be not less than m and not more than 3.0 μm. Thus, a first region 318 is formed on the side surface of the insulating film (FIG. 4B).

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

Note that, under the first etching condition, if the time change of the gas flow ratio of the first reactive gas CF ₄ is moderated, the inclination of the side surface of the insulating film gradually changes. growing. Conversely, in the first etching, the time variation of the gas flow ratio of the first reactive gas CF ₄ is sharpened, so that the first radius of curvature is reduced.

Thereafter, etching is performed without removing the resist film. In the second etching step, as it is using CF _4, O ₂ and He as an etching gas, a first reactive gas CF _4, the second reactive gas O _2, inert gases H
The etching is continued while the gas flow ratio of e is kept constant at 7/93/40 (sccm). Thereby, the insulating film 303
, A region where the taper angle of the inclined surface is constant is formed. Thereby, on the side surface of the insulating film, the second region 3
19 are formed. The taper angle of the inclined surface of the insulating film formed in the second etching step is determined by the final gas flow ratio in the first etching step. As the ratio of the first reactive gas CF ₄ to the _second reactive gas O ₂ increases, the taper angle of the inclined surface of the insulating film increases. In the second region 319, the taper angle of the side surface of the insulating film is 35.
It is preferable that it is not less than 70 ° and not more than 70 °.

In the etching under the second etching condition, since the anisotropic etching is performed by the reactive gas, the first side surface of the insulating film formed in FIG.
The region 318 is transferred to the lower side of the polyimide resin film while maintaining its shape.

The top and side surfaces of the resist film 304 are etched, the film thickness decreases, and the side surfaces recede inside the resist film (FIG. 4C).

Next, a third etching step is performed. The third etching condition was changed without removing the resist film, and CF ₄ , O _2, and He were used as etching gases as they were,
The ratio of the first reactive gas CF ₄ to the _second reactive gas O ₂ is reduced with time. For example, CF ₄ , O ₂ and H
e from 7/93/40 (sccm)
The time is changed to 1.5 / 98.5 / 40 (sccm). Thereby, the taper angle of the inclined surface of the insulating film is gradually reduced to be a curved surface. The radius of curvature of this surface is
Radius of curvature. The third region 320 of the insulating film 307 is formed under the third etching condition.

The top and side surfaces of the resist film 306 are etched, the film thickness decreases, and the side surfaces recede inside the resist film (FIG. 5A).

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

As described above, 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. Second
Region includes the central portion of the insulating film. The third region includes the upper end of the insulating film.

Thereafter, as a fourth step, a resist film 306 is formed.
Is removed, and as a fifth step, an EL film 4 is formed on the insulating film and the electrode.
23 are formed. Further, an EL element is formed by forming the cathode 424 on the EL film (FIG. 5B).

The cross section indicated by the dashed line BB ′ in FIG. 5B corresponds to the cross section of the top view of FIG. 9 cut along the dashed line BB ′. The same parts as those in FIG. 9 are denoted by the same reference numerals.

The etching using a reactive gas has an advantage that fine processing is possible. FIG. 4 shows an example in which an organic material is used for the insulating film; however, an inorganic material can be used for the insulating film. For example, when an SiO ₂ film is used as the insulating film, it is preferable to use CHF ₃ as the first reactive gas and O ₂ as the second reactive gas as the reactive gas. Then, as described above, in the first etching step, the second etching step, and the third etching step, the flow ratio of the first reactive gas and the second reactive gas is changed. As the gas flow ratio of the first reactive gas CHF ₃ increases, the etching in the thickness direction of the insulating film proceeds more easily, and the taper angle of the inclined surface increases. In this manner, even if the material in the above-described step is replaced, the first region 318 and the third region 320 of the insulating film are formed into a curved surface as in FIG. Can have a constant slope.

However, since the inorganic insulating film reflects the lower unevenness, unevenness due to the wiring of the TFT element or the like may occur on the surface of the inorganic insulating film. In this case, the surface of the inorganic insulating film is preliminarily CMP (Chemical Mechanical).
After polishing with cal polishing (chemical mechanical polishing), a resist film is formed, and the inorganic insulating film is etched to form bumps.

Further, FIG.
A method for manufacturing the shape of FIG. 6B will be described with reference to FIGS.

Before the thermosetting, the polyimide resin film is an organic film containing a polyamic acid as a main component, and is dehydrated and condensed by the thermosetting to form a polyimide film. In the embodiment described with reference to FIGS. 4 and 5, the resin film before and after thermosetting is described as a polyimide resin film because there is no particular need to distinguish between them. However, in the process shown in FIG. 6, since the difference in chemical characteristics between polyamic acid and polyimide is used, the difference will be clearly described.

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

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

Then, as a fifth step, the resist film and the organic film on the substrate are immersed in a developing solution having basicity to perform development. The developer is, for example, tetramethylammonium hydroxide (TMA) having a concentration of 2.0 to 6.0%.
H) A developer can be used. First, a portion of the resist film exposed to ultraviolet light is dissolved in the developing solution. Thereafter, the organic film 311 containing polyamic acid as a main component is isotropically etched with a basic developer using the resist film as a mask. Although the polyimide resin film 311 under the resist film 310 remains largely protected by the resist film, the polyimide resin film below the edge of the resist film still has a curved cross section due to isotropic etching ( FIG. 6 (B).

Thereafter, as a sixth step, the resist film is immersed in a solvent for the resist film to dissolve and remove the resist film. Examples of the solvent for the resist film include NMP (N-methyl-2-pyrrolidone).

Thereafter, as a seventh step, a temperature of 180 ° C. or more
The organic film is dehydrated and condensed and imidized at a temperature of 50 ° C. or less for 1 hour to 3 hours. Thereby, the organic film containing polyamic acid as a main component is chemically changed to a polyimide resin film. The polyimide resin film contracts inward with imidization, and the surface of the polyimide resin film 312 becomes rounded (FIG. 6C).

As described above, 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 has a curved shape including the lower end of the insulating film. The second region 322 includes the center of the side surface of the insulating film. The third region 323 includes the upper end of the insulating film.

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

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

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

Another example of a method for manufacturing the cross-sectional shape shown in FIG.

For example, a resist film is patterned on an insulating film, the insulating film is isotropically etched, and then the resist film is removed. After that, RIE (Reactive Ion Etc
When the insulating film is etched by hing), a reactive gas is easily applied to a portion where the side surface and the upper surface of the insulating film are in contact with each other, so that the vicinity of a tangent between the side surface and the upper surface of the insulating film can be curved.

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

First, an insulating film 324 is formed on the electrode, and a resist film 325 is formed on the insulating film 324. The thickness of the insulating film is 1 to 3 μm, and the thickness of the resist film is 0.5 to 5 μm.
μm. The insulating film is formed by applying a polyimide resin film or an acrylic resin film and thermally curing the film (FIG. 19A).

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

Next, the resist film is removed (FIG. 19).
(C)).

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

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

Another example of a method for manufacturing the cross-sectional shape of FIG. 1A or FIG.

FIG. 7A shows a manufacturing method in which a photosensitive organic material is used as the insulating film. By exposing a photosensitive material and etching with a developing solution, the cross-sectional shape can be made gentle. As the organic material, a photosensitive polyimide resin film or a photosensitive acrylic film can be used. It is preferable to use a positive type photosensitive organic material.

For example, the photosensitive polyimide resin film 316
Is applied at a thickness of 1.0 to 3.0 μm, and 50 ° C. to 1
Heat treatment is performed at a temperature of 50 ° C. for 1 to 5 minutes to remove the solvent contained in the photosensitive polyimide resin film. After that, ultraviolet light 313 is applied to the quartz glass 314 through a photomask in which the chromium film 315 is formed, so that the photosensitive polyimide resin film is exposed (FIG. 7A).

In the present invention, the ultraviolet rays that have passed through the photomask are diffracted during exposure. In a normal exposure apparatus, light that has passed through a photomask spreads by diffraction, so the light spread by diffraction is incident on the lens, and the substrate is placed at the focal point of the lens. The pattern of the photomask is accurately transferred to the film. However, in the present invention, when exposing the photosensitive polyimide resin film, the substrate is intentionally placed about 0.05 to 30 μm below the focal point of the lens. Then, light that has passed through the photomask and spread by diffraction is applied to the photosensitive polyimide resin film. Light (ultraviolet rays 313) applied to the photosensitive resin enters the inside of the chromium film 315 formed on the photomask by diffraction.

When a photosensitive polyimide resin film is exposed, diffraction can be positively utilized to form a cross-sectional shape having a gentle curved surface. The cross section of the insulating film 317 after development has a shape reflecting 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 smooth. After the development, the insulating film 317 is baked and thermally cured. (FIG. 7
(B)). In addition, when the photosensitive resin film is exposed, diffracted light is incident on the surface of the photosensitive resin that is shielded by the photomask, so that not only the cross-sectional shape of FIG. A cross-sectional shape of 1 (B) can also be manufactured.

Thereafter, the EL film 423 and the cathode 4 are formed on the insulating film.
24 are formed by vapor deposition (FIG. 7C).

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

The cross section of the bump fabricated according to the above-described embodiment was formed by cutting the substrate on which the bump was formed, and cutting the cross section by a field emission scanning electron microscope (Scanning Electron Microscope).
It can be easily confirmed by observing with a croscope (SEM).

Hereinafter, the EL according to the present invention will be described by way of examples.
The display device will be specifically described.

[0096]

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

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

As the substrate 401, a substrate made of glass such as barium borosilicate glass represented by Corning # 7059 glass or # 1737 glass, or aluminoborosilicate glass is used. Note that 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 enough to withstand the processing temperature of this embodiment 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 oxynitride film can be used. Although a two-layer structure is used as the base film 402 in this embodiment, a single-layer film of the insulating film or a structure in which two or more layers are stacked may be used.

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

The circuit configuration of the drive circuit section 450 differs between the gate signal side drive circuit and the data signal side drive circuit, but is omitted here. A wiring 412 and a wiring 413 are connected to the n-channel TFT 452 and the p-channel TFT 453, and a shift register, a latch circuit, a buffer circuit, and the like are formed using these TFTs.

In the pixel portion 451, the data line 414 is connected to the source side of the switching TFT 454, and the drain side line 415 is connected to the gate electrode 411 of the current control TFT 455. In addition, the current control TFT 45
The source side of No. 5 is connected to the power supply wiring 417, and the drain side electrode 416 is connected to the cathode of the EL element. FIG. 9A shows a top view of such a pixel, which is denoted by the same reference numerals as FIG. 8 for convenience. 9A, a cross section corresponding to line AA 'is shown in FIG.

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

The bump is formed 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. The surface of the photosensitive resin film is made to have a gentle curved shape by positively utilizing the diffraction when exposing the photosensitive polyimide resin film. The diffraction is caused by adjusting the optical system of the exposure apparatus.

The material for forming the EL film may be either a low molecular material or a high molecular material. When a low molecular material is used, an evaporation method is used. When a high molecular material is used, a spin coating method, a printing method, an inkjet method, or the like is used.

As the polymer material, a π-conjugated polymer material and the like are known. Typical examples include a crystalline semiconductor film such as paraphenylene vinylene (PPV), polyvinyl carbazole (PVK), and polyfluorene.
An EL film formed using such a material is used in a single-layer structure or a stacked structure; however, the use of a stacked structure provides higher luminous efficiency. In general, a hole injection layer / a hole transport layer / a light emitting layer / an electron transport layer are formed in this order on the anode, but a hole transport layer / a light emitting layer / an electron transport layer, or a hole injection layer / a hole A structure such as a transport layer / light-emitting layer / electron transport layer / electron injection layer may be used. In the present invention, any known structure may be used,
The EL film may be doped with a fluorescent dye or the like.

As the organic EL material, for example, the materials disclosed in the following US patents or publications can be used. U.S. Pat. No. 4,356,429; U.S. Pat. No. 4,539,507; U.S. Pat. No. 4,720,432
No. 4,769,292; U.S. Pat.
No. 885,211; U.S. Pat. No. 4,950,950;
U.S. Pat. No. 5,059,861, U.S. Pat.
No. 7,687, U.S. Pat. No. 5,073,446, U.S. Pat. No. 5,059,862, U.S. Pat.
No. 617, U.S. Pat. No. 5,151,629, U.S. Pat. No. 5,294,869, U.S. Pat. No. 5,294,87.
0, JP-A-10-189525, JP-A-8-2
No. 41048, JP-A-8-78159.

The color display is roughly classified into four types: a method of forming three kinds of EL elements corresponding to R (red), G (green), and B (blue); a white light emitting EL element and a color filter. , A blue or blue-green emission E
There are a method in which an L element and a phosphor (fluorescent color conversion layer: CCM) are combined, and a method in which an EL element corresponding to RGB is stacked using a transparent electrode as a cathode (counter electrode).

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

The above example is an example of an organic EL material that can be used as a light emitting layer, and the present invention is not limited to this. Materials for forming the light emitting layer, the charge transport layer, and the charge injection layer can be freely selected in possible combinations thereof. The EL film shown in this embodiment is composed of a light emitting layer and PE
A structure in which a hole injection layer made of DOT (polythiophene) or PAni (polyaniline) is provided.

On the EL film 423, the cathode 42 of the EL element is provided.
4 are provided. As the cathode 424, a material containing magnesium (Mg), lithium (Li), or calcium (Ca) having a small work function is used. Preferably Mg
An electrode made of Ag (a material obtained by mixing Mg and Ag at a ratio of Mg: Ag = 20: 1) may be used. Other examples include a MgAgAl electrode, a LiAl electrode, and a LiFAl electrode.

After forming the EL film 423, the cathode 424
It is preferable to form continuously without opening to the atmosphere. This is because the state of the interface between the cathode 424 and the EL film 423 greatly affects the luminous efficiency of the EL element. Note that in this specification, a light-emitting element formed by an anode (pixel electrode), an EL film, and a cathode is referred to as an EL element.

The laminate composed of the EL film 423 and the cathode 424 needs to be formed individually for each pixel.
Since No. 3 is extremely weak against moisture, ordinary photolithography cannot be used. In addition, the cathode 424 manufactured using an alkali metal is easily oxidized.
Therefore, it is preferable to selectively form the film by a vapor phase method such as a vacuum evaporation method, a sputtering method, and a plasma CVD method using a physical mask material such as a metal mask. In addition, as a method for selectively forming an EL film, an ink-jet method, a screen printing method, or the like can be used. However, at present, it is not possible to form a cathode continuously.

Further, a protective electrode for protecting from external moisture and the like may be laminated on the cathode 424. As the protective electrode, a low-resistance material including aluminum (Al), copper (Cu), or silver (Ag) is preferably used.
Alternatively, light can be emitted in a direction indicated by an arrow in FIG. 8 by using a transparent electrode (this is referred to as top emission for convenience). In that case, when a black pigment is mixed in the organic resin interlayer insulating film 419, a black screen can be formed without light emission without using a polarizing plate. This protective electrode can also be expected to have a heat radiation effect of reducing heat generation of the EL film. After the EL film 423 and the cathode 424 are formed, it is also effective to continuously form the protective electrode without opening to the atmosphere.

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 a bump 1102 made of an insulating film is formed.
An EL film 1103 is formed. Furthermore, as the cathode 1104, LiFAl and MgAg are formed in a thickness of 10 to 50 nm to have light transmittance. In order to further reduce the wiring resistance, a transparent conductive film 1105 is formed on the cathode. Thus, light can be emitted in the direction indicated by the arrow in FIG. At this time, since the cathode has light transmittance, it is possible to suppress glare on the display screen when light is not emitted.

In FIG. 8, the switching TFT 454 has a multi-gate structure, and the current control TFT 455 is provided with an LDD overlapping the gate electrode. Since a TFT using polysilicon has a high operation speed, deterioration such as hot carrier injection is likely to occur. Therefore, a TFT having a different structure according to the function in a pixel
Forming (a switching TFT having sufficiently low off-current and a current control TFT which is strong against hot carrier injection) has high reliability and enables good image display (high operation performance). This is very effective in manufacturing a display device.

FIG. 9B is a circuit diagram of the pixel shown in FIGS. 8 and 9A. A pixel is arranged near the intersection of the gate line and the data line.
54, a current controlling TFT 455, and an EL element 456 are provided.

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 the gate electrode of the current control TFT 455 and one electrode of the capacitor 458. The other electrode of the capacitor is connected to the power supply line 417. The current control TFT is connected to the power supply line 417.
Are connected to each other, and the drain side of the current controlling TFT is connected to the EL element 456.

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

FIG. 12 is a diagram showing the appearance of such a display device. The direction in which an image is displayed depends on the configuration of the EL element, but here, light is emitted upward to perform display. The configuration shown in FIG.
04, an element substrate 601 on which a driver circuit portion 605 and a pixel portion 603 are formed and a sealing substrate 602 are attached to each other with a sealant 610. An input terminal 608 is provided at an end of the element substrate 601 and an FPC (Flexible Print
t Circuit) is connected. Input terminals 608 are provided with terminals for inputting image data signals, various timing signals, and power from an external circuit at a pitch of 500 μm. The wiring 609 is connected to the driving circuit portion. Also,
If necessary, an IC chip 607 on which a CPU, a memory, and the like are formed may be mounted on the element substrate 601 by a COG (Chip on Glass) method or the like.

As shown in FIG. 11, an input terminal is a wiring 705 made of titanium (Ti) and aluminum (Al).
And an ITO 706 formed as an anode. FIG. 11 is a cross-sectional view corresponding to line CC ′ in the input terminal portion. The element substrate 701 and the sealing substrate 702 are attached to each other with a sealant 703. In the drive circuit portion, the EL film 707 and the cathode 708 are
9, a contact portion 720 as shown is provided for bringing the cathode 708 into contact with the wiring. Also in the contact portion 720, since the side surface of the bump has a gentle curved surface, disconnection of the cathode layer can be prevented.

In a display device using such an EL element, the side surface of the bump has a gentle curved surface,
Disconnection of the EL film and the cathode can be prevented, and the yield of the display device can be increased.

Embodiment 2 FIG. 13 shows an example of a display device using an inversely staggered TFT. The substrate 501 or E to be used
The L element 556 has the same configuration as in the first embodiment, and a description thereof will be omitted.

In the inverted stagger type TFT, gate electrodes 508 to 511, a gate insulating film 507, and semiconductor films 503 to 506 are formed in this order from the substrate 501 side. 13, an n-channel TFT 552 and a p-channel TFT 553 are formed in a driving circuit portion 550, and a switching TFT 554 and a current control TFT 55 are formed in a pixel portion 551.
5. An EL element 556 is formed. The interlayer insulating film includes an inorganic insulating film 518 formed of silicon nitride, silicon oxynitride, or the like, and an organic resin film 519 formed of acrylic, polyimide, or the like.

The circuit configuration of the drive circuit section 550 differs between the gate signal side drive circuit and the data signal side drive circuit, but is omitted here. A wiring 512 and a wiring 513 are connected to the n-channel TFT 552 and the p-channel TFT 553, and a shift register, a latch circuit, a buffer circuit, and the like are formed using these TFTs.

In the pixel portion 551, the data line 514 is connected to the source side of the switching TFT 554, and the drain side line 515 is connected to the gate electrode 511 of the current control TFT 555. The current control TFT 55
5 is connected so that the source side is connected to the power supply wiring 517 and the drain side electrode 516 is connected to the anode of the EL element.

Then, bumps 520 and 521 are formed 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 the photosensitive resin, the bumps can be formed into a curved surface with gentle side surfaces. The EL element 556 includes an anode 522 formed of ITO (indium tin oxide), an EL film 523 formed using an organic EL material, and a cathode 524 formed using a material such as MgAg or LiF. I have. The bumps 520 and 521 are formed so as to cover the end of the anode 522, and prevent a short circuit between the cathode and the anode.

An anode 522 was formed using a transparent electrode, and a cathode 524 was formed of magnesium (Mg) having a small work function.
By using a metal material containing lithium (Li) or calcium (Ca), light is emitted in a direction indicated by an arrow in FIG. The direction of light emission can be arbitrarily determined depending on whether or not the cathode has light reflectivity.

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. An inverted staggered TFT using polysilicon has an advantage that it can be manufactured by diverting a production line of an amorphous silicon TFT (usually formed by an 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.

[Embodiment 3] An example of an electronic device using the display device shown in Embodiment 1 will be described with reference to FIG. In the display device of FIG. 14, the pixel 9 is formed by TFTs formed on the substrate.
20, a data signal side driving circuit 915 used for driving the pixel portion, and a gate signal side driving circuit 914.
Are formed. Although the data signal side driver circuit 915 shows an example of digital driving, a shift register 916,
It comprises latch circuits 917 and 918 and a buffer circuit 919. The gate signal side driver circuit 914 includes a shift register, a buffer, and the like (neither is shown).

The pixel portion 921 is 640 in the case of VGA.
Each pixel has a × 480 (horizontal × vertical) pixel, and as described with reference to FIG. 8 or FIG. 9, a switching TFT and a current controlling TFT are arranged in each pixel. In 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 stored in the capacitor, and the gate of the current controlling TFT opens. That is,
A current flows through the current control TFT by a data signal input from the source wiring, and the EL element emits light.

The system block diagram shown in FIG.
A shows a form of a portable information terminal such as A. The display device described in Embodiment 1 includes a pixel portion 921, a gate signal side driver circuit 914, and a data signal side driver circuit 915.

An external circuit connected to this display device includes a power supply circuit 901 including a stabilized power supply and a high-speed and high-precision operational amplifier, an external interface port 902 having a USB terminal, a CPU 903, and a pen input tablet used as input means. 910, a detection circuit 911, a clock signal oscillator 912, a control circuit 913, and the like.

The CPU 903 includes a video signal processing circuit 904, a tablet interface 905 for inputting a signal from the pen input tablet 910, and the like. Also, a VRAM 906, a DRAM 907, a flash memory 908, and a 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 a video signal and a clock into respective timing specifications of the data signal side drive circuit 915 and the gate signal side drive circuit 914.

More specifically, a function of distributing a video signal to data corresponding to each pixel of the display device and a function of transmitting a horizontal synchronizing signal and a vertical synchronizing signal input from the outside to a start signal of a driving circuit and an AC power of a built-in power supply circuit. It has a function to convert it into a timing control signal.

It is desired that a portable information terminal such as a PDA can be used for a long time outdoors or in a train by using a rechargeable battery as a power source without being connected to an AC outlet. In addition, such electronic devices are required to be lightweight and compact at the same time with an emphasis on portability. Batteries, which account for the majority of the weight of electronic devices, increase in weight as capacity increases. 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 a standby mode.

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

To display a still image, the CPU 90
The functions of the third video signal processing circuit 904, VRAM 906, and the like can be stopped to reduce power consumption.
In FIG. 14, the portion where the operation is performed is indicated by a dotted line.
Further, as shown in FIG.
It may be mounted on the element substrate by a COG method using a C chip, or may be integrally formed inside the display device.

Example 4 In this example, an organic compound (hereinafter, referred to as a singlet compound) emitting light by a singlet exciton (singlet) and an organic compound emitting light by a triplet exciton (triplet) are used as EL films. ,
An example in which a triplet compound is used together will be described. Note that a singlet compound refers to a compound that emits light only via singlet excitation, and a triplet compound refers to a compound that emits light via triplet excitation.

As the triplet compound, organic compounds described in the following articles can be mentioned as typical materials.
(1) T.Tsutsui, C.Adachi, S.Saito, Photochemical
Processes in Organized Molecular Systems, ed.K. Hon
da, (Elsevier Sci. Pub., Tokyo, 1991) p. 437. (2) M.
A. Baldo, DFO'Brien, Y. You, A. Shoustikov, S. Sible
y, METhompson, SRForrest, Nature 395 (1998) p.
151. This article discloses an organic compound represented by the following formula. (3) MABaldo, S.Lamansky, PEBurrrow
s, 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.Wakim
oto, S. Mayaguchi, Jpn.Appl.Phys., 38 (12B) (1999)
L1502.

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

[0142]

Embedded image

[0143]

Embedded image

In the above molecular formula, M is 8 to 1 in the periodic table.
It is an element belonging to Group 0. Et is an ethyl group. In the above paper, platinum and iridium are used. Also,
The inventor has reported that nickel, cobalt or palladium
Since it is cheaper than platinum and iridium, it is considered to be preferable in reducing the manufacturing cost of the light-emitting device. In particular, nickel is considered to be preferable because of its high productivity because it easily forms a complex.

The triplet compound has a higher luminous efficiency than the singlet compound, and the operating voltage (the voltage required for the EL element to emit light) can be lowered to obtain the same emission luminance. This embodiment utilizes this feature.

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 other colors. This is because the luminous efficiency is inferior to the other colors, so that the operating voltage must be set high to obtain the same luminous brightness as the other colors, and the deterioration proceeds accordingly.

However, in this embodiment, since the triplet compound having high luminous efficiency is used as the light emitting layer emitting red light, the light emitting layer emitting green light and the light emitting layer emitting blue light can be operated while obtaining the same light emission luminance. It is possible to make the voltages uniform. Therefore, deterioration of the light emitting layer that emits red light is not extremely accelerated, and color display can be performed without causing a problem such as color misregistration. The fact that the operating voltage can be kept low is also preferable from the viewpoint that the margin of the withstand voltage of the transistor can be set low.

In this embodiment, an example in which a triplet compound is used as a light emitting layer emitting red light is shown. However, a triplet compound may be used in a light emitting layer emitting green light or a light emitting layer emitting blue light. It is possible.

In the case of performing RGB color display, an EL element that emits red light, an EL element that emits green light,
It is necessary to provide an EL element which emits blue light. In this case, a triplet compound can be used for an EL element that emits red light, and the others can be formed using a singlet compound.

By selectively using the triplet compound and the singlet compound in this manner, the operating voltages of the respective EL elements are all the same (20 V or less, preferably 3 to 20 V).
V). Therefore, the power supply required for the display device can be unified at, for example, 3 V or 5 V, and thus there is an advantage that circuit design becomes easy. The configuration of the present embodiment can be implemented in combination with any of the configurations of the first to third embodiments.

[Embodiment 5] A display device formed by implementing the present invention is incorporated in various electric appliances, and a pixel portion is used as a video display portion. As the electronic device of the present invention, a mobile phone, a PDA, an electronic book, a video camera, a notebook personal computer, an image reproducing device equipped with a recording medium,
For example, DVD (Digital Versatile Disc) player,
Digital camera, and the like. Specific examples of these electronic devices are shown in FIGS.

FIG. 15A shows a cellular phone, which includes a display panel 9001, an operation panel 9002, and a connection portion 9003.
The display panel 9001 includes a display device 900.
4, an audio output unit 9005, an antenna 9009, and the like. An operation key 900 is provided on the operation panel 9002.
6, a power switch 9007, a voice input unit 9008, and the like. The invention can be applied to the display device 9004.

FIG. 15B also shows a mobile phone, which includes a main body or a housing 9101, a display device 9102, and a sound output portion 910.
3, an audio input unit 9104 and an antenna 9105 are provided. The display device 9102 may incorporate a touch-type sensor so that buttons can be operated on a 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, the substrate can be curved after the display device is completed. Taking advantage of such characteristics, it can be incorporated into a case having a three-dimensional curved surface designed based on ergonomics without any uncomfortable feeling.

FIG. 15C shows a mobile computer or a portable information terminal.
02, an image receiving section 9203, operation switches 9204, and a display device 9205. The present invention provides a display device 920.
5 can be applied. Such electronic devices include:
Although a display device of a 3 inch to 5 inch class is used, the weight of the portable information terminal can be reduced by using the display device of the present invention.

FIG. 15D shows a portable book, and the main body 93 is shown.
01, a display device 9303, a storage medium 9304, operation switches 9305, and an antenna 9306,
Data stored on a mini disk (MD) or DVD,
This is for displaying the data received by the antenna. The present invention can be used for the display device 9303. As the portable book, a display device of a class of 4 inches to 12 inches is used. By using the display device of the present invention, the weight and thickness of the portable book can be reduced.

FIG. 15E shows a video camera, which includes a main body 9401, a display device 9402, an audio input portion 9403, operation switches 9404, a battery 9405, and the like. The present invention can be applied to the display device 9402.

FIG. 16A shows a personal computer, which includes a main body 9601, an image input section 9602, and a display device 9.
603 and a keyboard 9604. The present invention can be applied to the display device 9603.

FIG. 16B shows a player using a recording medium (hereinafter, referred to as a recording medium) on which a program is recorded, and includes a main body 9701, a display device 9702, and a speaker 97.
03, a recording medium 9704, and operation switches 9705. This device uses a DVD (Digi
(tal Versatile Disc), CDs, etc., to enjoy music, movies, games and the Internet. The present invention can be applied to the display device 9702.

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

FIG. 16D also shows a digital camera, which includes a main body 9901, a display device 9902, an image receiving portion 9903, operation switches 9904, a battery 9905, and the like. The present invention can be applied to the display device 9902. When the organic resin substrate of the present invention is used, the substrate can be curved after the display device is completed. Taking advantage of such characteristics, it can be incorporated into a case having a three-dimensional curved surface designed based on ergonomics without any uncomfortable feeling.

In the operation of the mobile phone shown in FIGS. 15A and 15B, the power consumption is reduced by increasing the luminance when using the operation keys and decreasing the luminance after using the operation switches. be able to. The power consumption can also be reduced by increasing the brightness of the display device when an incoming call is received and decreasing the brightness during a call. In addition, when the device is continuously used, the power can be reduced by providing a function of turning off the display by time control unless resetting is performed. Note that these may be manually controlled.

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 applicable range of the present invention is extremely wide, and can be applied to various products.

[0163]

As described above, by using the present invention as described above, in a display device using an EL element, the thickness of the EL film and the cathode formed by making the side surfaces of the bumps on the electrodes curved are formed. By improving the uniformity, 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.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a cross section of an EL element of the present invention.

FIG. 2 is a cross-sectional view illustrating a cross section of a bump according to the present invention.

FIG. 3 is a cross-sectional view illustrating a cross section of a bump according to the present invention.

FIG. 4 is a cross-sectional view (an embodiment) illustrating a bump manufacturing process of the present invention.

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

FIG. 6 is a cross-sectional view (an embodiment) illustrating a bump manufacturing process of the present invention.

FIG. 7 is a cross-sectional view (an embodiment) for explaining a bump manufacturing process of the present invention.

FIG. 8 is a cross-sectional view illustrating a configuration of a driving circuit and a pixel portion of a display device (Example 1).

9A and 9B are a top view and an equivalent circuit diagram illustrating a configuration of a pixel portion of a display device (Example 1).

FIG. 10 illustrates a configuration of an input terminal portion of a display device (Example 1).

FIG. 11 illustrates a configuration of an input terminal portion of a display device (Example 1).

FIG. 12 is a perspective view showing an appearance of an EL display device of the present invention (Example 1).

FIG. 13 is a cross-sectional view illustrating a configuration of a driver circuit and a pixel portion of a display device (Example 2).

FIG. 14 is a system block diagram of an electronic device including a display device (third embodiment).

FIG. 15 illustrates an example of an electronic device (Example 5).

FIG. 16 illustrates an example of an electronic device (Example 5).

FIG. 17 is a diagram showing a light emission direction of an EL element (Example 1).

FIG. 18 is a diagram illustrating the shape of a bump in a conventional example.

FIG. 19 is a cross-sectional view (embodiment) illustrating a bump manufacturing step of the present invention.

FIG. 20 is a diagram illustrating the shape of a bump according to the present invention.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05B 33/12 H05B 33/12 B 33/14 33/14 A F term (Reference) 3K007 AB11 AB17 AB18 BA06 BB07 CA01 CB01 DA01 DB03 EA00 EB00 FA01 5C094 AA07 AA08 AA32. LL07 LL14

Claims (25)

[Claims] 1. A display device using an EL element including one electrode, an EL film over the one electrode, and the other electrode over the EL film, wherein an end of the one electrode is covered. The bump has a selectively formed bump, the side surface of the bump has a lower end portion in contact with the upper surface of the one electrode, and an upper end portion continuous with the flat upper surface of the bump. The display device according to claim 1, wherein the upper end portion is in contact with an ellipse or circle having a center inside the bump, and the side surface of the upper end portion is in contact with an ellipse or circle having a center inside the bump. 2. A display device using an EL element including one electrode, an EL film on the one electrode, and the other electrode on the EL film, wherein an end of the one electrode is covered. A bump formed selectively; a side surface of the bump having a lower end portion in contact with an upper surface of the one electrode, an upper end portion continuous with a flat upper surface of the bump, and a portion between the lower end portion and the upper end portion; And the lower end portion is in contact with an ellipse or a circle having a center above the one electrode, and a surface contacting the central portion has an angle with respect to the upper surface of the one electrode of 35 ° or more and 70 °. The display device according to claim 1, wherein the upper end portion is in contact with an ellipse or a circle having a center inside the bump. 3. A display device using an EL element including one electrode, an EL film on the one electrode, and the other electrode on the EL film, wherein an end of the one electrode is covered. Having a selectively formed bump, the lower end of the bump in contact with the upper surface of the one electrode,
A curved side surface that is in contact with a circle having a center of curvature above a tangent line between the one electrode and the lower end portion and a circle having a first radius of curvature, and an upper end portion of the bump is continuous with a flat upper surface of the bump. A display device, wherein an upper end portion of the bump has a curved side surface that is in contact with a circle having a center of curvature below a boundary between the upper end portion and the upper surface and a circle having a second radius of curvature. 4. In a display device using an EL element including one electrode, an EL film on said one electrode, and another electrode on said EL film, an end of said one electrode is covered. Having a selectively formed bump, the lower end of the bump in contact with the upper surface of the one electrode,
A surface having a curved surface that is in contact with a circle having a curvature center and a first radius of curvature above a tangent line between the one electrode and the lower end portion, and a surface that is in contact with a side surface of a center portion of the bump is the one side. An angle with respect to an upper surface of the electrode is 35 ° or more and 70 ° or less, an upper end portion of the bump is continuous with a flat upper surface of the bump, and an upper end portion of the bump is below a boundary between the upper end portion and the upper surface. A display device having a curved side surface that is in contact with a circle having a center of curvature and a second radius of curvature. 5. The bump according to claim 1, wherein an angle of a surface contacting the side surface of the bump with respect to the upper surface of the one electrode is continuous from the lower end portion to the upper end portion of the side surface of the bump. Wherein the angle is in the range of 0 ° to 70 °. 6. The method according to claim 3, wherein the first radius of curvature and the second radius of curvature are 0.2 μm.
a display device having a length of at least m and at most 3.0 μm. 7. The display device according to claim 4, wherein the bump has a thickness of 1.0 μm or more and 3.0 μm or less. 8. A display device using an EL element including one electrode, an EL film on the one electrode, and the other electrode on the EL film, wherein an end of the one electrode is covered. A side surface of the bump having a lower end portion in contact with an upper surface of the one electrode and an upper end portion continuous with a flat upper surface of the bump; The display device, wherein an angle of a surface in contact with a side surface of the bump with respect to a top surface of the one electrode continuously changes, and the angle is in a range of 0 ° or more and 70 ° or less. 9. The method according to claim 1, wherein the other electrode is formed so as to overlap an upper end and a lower end of the bump. Characteristic display device. 10. The method according to claim 2, wherein the other electrode is formed so as to overlap with an upper end, a center, and a lower end of the bump. Characteristic display device. 11. One electrode and an EL on said one electrode
In a display device using an EL element including a film and the other electrode on the EL film, the display device has a bump selectively formed to cover an end of the one electrode, and the surface of the bump is The bump has a lower end portion in contact with the upper surface of one electrode and an upper end portion, and the lower end portion of the bump in contact with the upper surface of the one electrode has an elliptical or circular surface centered on the one electrode. The upper end of the bump has an elliptical or circular surface having a center inside the surface of the bump. 12. One electrode and an EL on said one electrode
A display device using an EL element including a film and the other electrode on the EL film, comprising: a bump selectively formed to cover an end of the one electrode; and an upper surface of the one electrode The lower end of the bump in contact with
A center of curvature above a tangent line between the one electrode and the lower end portion, and a curved side surface tangent to a circle having a first radius of curvature; and an upper end portion of the bump has a lower center of curvature of the upper end portion. And a curved surface determined by the second radius of curvature. 13. An electrode and an EL on said one electrode.
In a display device using an EL element including a film and the other electrode on the EL film, a display device includes a bump selectively formed over an end of the one electrode, and an upper surface of the one electrode. The lower end of the bump in contact with
A surface having a curved surface that is in contact with a circle having a center of curvature above a tangent line between the one electrode and the lower end and a circle having a first radius of curvature, and a surface that is in contact with a side surface of a central portion of the bump is one of An angle with respect to the upper surface of the electrode is 35 ° or more and 70 ° or less, and the upper end of the bump has a curved surface determined by a center of curvature below the upper end and a second radius of curvature. Display device. 14. The bump according to claim 11, wherein an angle of a surface contacting the surface of the bump with respect to an upper surface of the electrode continuously changes from the lower end to the upper end of the surface of the bump. And the angle is 0 ° or more and 70 ° or more.
A display device having the following range. 15. The device according to claim 12, wherein the first radius of curvature and the second radius of curvature are 0.2 μm.
a display device having a length of at least m and at most 3.0 μm. 16. The display device according to claim 11, wherein the bump has a thickness of 3.0 μm or less. 17. The method of claim 11, claim 12, claim 14,
17. The display device according to claim 15, wherein the other electrode is formed so as to overlap a lower end and an upper end of the bump. 18. The method according to claim 13, 14 or 16.
3. The display device according to claim 1, wherein the other electrode is formed so as to overlap an upper end, a center, and a lower end of the bump. 19. The display device according to claim 1, wherein the electrode is an anode or a cathode. 20. The display device according to claim 1, wherein the EL element has an EL film made of an organic material on the electrodes and the bumps. 21. A personal computer, a video camera, a portable information terminal, a digital camera, a DVD player, and an electronic game machine using the display device according to any one of claims 1 to 20. 22. A first step of forming an electrode; a second step of forming an insulating film on the electrode; a third step of patterning a resist film on the insulating film; A fourth step of forming an insulating film by etching using the first reactive gas and the second reactive gas, a fifth step of removing the resist film, and a sixth step of forming an EL film on the insulating film A first etching step in which the flow rate ratio of the first reactive gas to the second reactive gas increases with time, wherein the first reactive gas and the second reactive gas A second etching step in which the flow ratio of the reactive gas is constant, and a third etching step in which the flow ratio of the first reactive gas decreases with time with respect to the second reactive gas. A method for manufacturing a display device, comprising: 23. The method according to claim 21, wherein the first reactive gas is CF ₄ , the second reactive gas is O ₂ , and the insulating film is an acrylic resin film or a polyimide resin film. A method for manufacturing a display device, comprising: 24. A first step of applying an organic film containing a polyamic acid as a main component on the electrode; a second step of heat-treating the organic film at a temperature of 50 ° C. or more and 150 ° C. or less; A third step of forming a resist film, a fourth step of exposing the resist film, a fifth step of selectively dissolving a part of the resist film and the organic film in a developer exhibiting basicity, A sixth step of removing the resist film, a seventh step of heat treating the organic film at a temperature of 180 ° C. or more and 350 ° C. or less to form a polyimide resin film, and a step of forming an EL film on the polyimide resin film. A method for manufacturing a display device, comprising eight steps. 25. A personal computer, a video camera, a portable information terminal, a digital camera, a personal computer, a video camera using the method for manufacturing a display device according to claim 22.
A method for producing digital video disc players and electronic game machines.