JP2006119669A - Display apparatus and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display apparatus and a method for manufacturing the apparatus by which uniformity in the film thickness of an EL (electroluminescence) film and a cathode formed on a curved side face of a bump on an electrode can be improved, occurrence of discontinuity in the EL film and the cathode can be prevented, the yield of an EL element can be increased and the display quality can be improved. <P>SOLUTION: The EL element has an insulating film 101 formed on an anode 100 and further an EL film 102 and a cathode 103 formed on the insulating film 101, wherein each of a bottom end portion and a top end portion of the insulating film 101 is formed in a curved surface. The taper angle in the center of the insulating film 101 is controlled within a range of 35° to 70°. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an element (hereinafter referred to as “EL element”) in which a thin film (hereinafter referred to as “EL film”) made of a compound from which electroluminescence (hereinafter referred to as EL) is obtained is sandwiched between electrodes. The present invention relates to a display device including the same and a manufacturing method thereof.

EL includes phosphorescence emitted when transitioning from a triplet excited state to a ground state, and fluorescence emitted when transitioning from a singlet excited state to a ground state.

  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. An organic EL element is an EL element in which an organic EL film is sandwiched between electrodes.

  A thin film transistor (TFT) element in this specification 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 a wiring.

  A display device using an organic EL film can be reduced in weight and thickness as compared with a conventional CRT, and is being applied to various applications. Mobile phones and personal digital assistants (PDAs) can be connected to the Internet, and the amount of information displayed on the video display increases dramatically. There is a growing demand for aging.

  A means for applying a voltage to the EL film by an active element such as a thin film transistor (TFT) is employed as a means for increasing the definition of the display device.

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

  An EL element generally has a configuration 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, in order to reduce the resistance, a thin EL film having a thickness of 30 nm to 150 nm is formed on the anode having a 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 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 spot defect.

  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 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, even in the cross-sectional structure of FIG. 18, there are 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, the EL film is likely to break at the point 1004 where the upper surface of the anode and the side surface of the insulating film are in contact with each other. That is, the EL film 1002 is not deposited and a gap is formed at a place where the inclination of the deposition surface of the EL film changes abruptly. 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 thinned at 1004 where the upper surface of the anode and the side surface of the insulating film are in contact with each other, the electric field concentrates on the thinned portion of the EL film, and the EL film becomes thin. Luminescence occurs only in places.

  In addition, when the cathode on the insulating film is electrically connected to the wiring under the insulating film through a contact hole that penetrates the insulating film, if the cathode is disconnected on the side surface of the insulating film, no potential is applied to the cathode and display is performed. There is a case where it is not broken.

  Further, disconnection of the EL film and the cathode is likely to occur near 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) is formed in a stripe shape so as to cover the gap between adjacent pixels. At this time, when the 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 have a 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 to increase 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 the disconnection of the cathode causes a yield and a deterioration in display quality. Response is required. Further, the concentration of the electric field due to the local thinning of the EL film needs to be countered because the luminance of the defective pixel is changed with respect to the luminance of the pixel having no defect, thereby impairing the visibility.

  By optimizing the shape of the bumps, the inventors of the present invention gently change the inclination of the EL film and cathode film formation surfaces on the bumps, so that the EL film and the cathode are easily formed in a uniform film thickness. Thus, 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 bump was optimized so that the EL film and the cathode could be formed with a uniform film thickness and excellent display performance was ensured.

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

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

  For example, in the case where the upper portion shown in the cross-sectional view of FIG. 20B is a bump having a curved surface, both ends of the lower portion of the insulating film 201 are the lower end portion 204, the vicinity of the thickest portion of the insulating film is the upper portion 206, A portion having a height in the middle between the upper surface 206 of the insulating film and the surface in contact with the upper surface of the anode 200 below the insulating film is referred to as a central portion 205.

  An example of the structure of the present invention is shown in FIG. 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. The shape of the insulating film will be described below with reference to FIG. FIG. 2 is a sectional view for explaining the 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 the length of a perpendicular line extending from the upper surface of the insulating film to the lower surface of the insulating film.

  In order to prevent disconnection of the EL film 102 and the cathode 103, the thickness of the insulating film is preferably not too thick, and is 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.

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

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

  (2) In addition to the configuration of (1) above, the central portion 105 of the insulating film has a side surface where the angle θ formed by 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. Further, disconnection of the EL film and the cathode on the side surface 108 of the insulating film can be prevented. In this specification, the “center portion” refers to a portion of the insulating film 101 having a height in the middle between the upper surface of the insulating film and the surface in contact with the upper surface of the anode. In the present specification, a surface in contact with the side surface of the insulating film is hereinafter referred to as an “inclined surface”. An angle formed between the inclined surface and the upper surface of the anode is referred to as “tapered taper angle”.

  The taper angle of the inclined surface in the central portion of the insulating film is preferably 35 ° or more and 70 ° or less. When 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 that the cathode is disconnected is increased. When the taper angle of the inclined surface is less than 35 °, the film thickness of the insulating film (bump) tends to decrease with a decrease in the taper angle of the inclined surface. 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 includes an EL element having 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 portion 106 of the insulating film is continuous with the upper surface of the insulating film, and is a curved surface determined by the center of curvature (O2) below the boundary line between the upper end portion 106 and the flat upper surface 107 and the second radius of curvature (R2). (FIGS. 2A and 2B).

  Since the lower end portion 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 on the lower end portion of the insulating film is improved, and the lower end portion The disconnection of the EL film can be prevented. Thereby, the short circuit of the anode and the cathode due to the disconnection of the EL film is reduced. In addition, the EL film can be prevented from being partially thinned, and local electric field concentration in the EL film can be prevented.

  In the upper end portion 106 of the insulating film, the inclination of the surface in contact with the side surface of the insulating film with respect to the upper surface of the anode 100 continuously changes, 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. Disconnection 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, point defects due to the continuous disconnection of the cathode becoming a closed curve shape can be prevented. 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 cathode wiring resistance from increasing due to the disconnection of the cathode. Furthermore, it is possible to suppress disconnection of the cathode on the side surface of the contact hole when the cathode contacts the wiring under the insulating film through the contact hole penetrating the insulating film.

(4) In addition to the configuration of (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. When the first radius of curvature (R ₁ ) is less than 0.2 μm, the side surface of the insulating film 101 in contact with the anode 100 has a sharp shape. Therefore, the EL film and the cathode are uniformly formed on the side surface of the insulating film 101. There is a risk that it may be difficult to form with a large thickness. For example, since the inclination of the deposition surface of the EL film changes abruptly, the EL film becomes thin and the electric field concentrates locally 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.

  Regardless of etching using an aqueous solution of acid, base, or the like, or etching using 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.

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

(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. If the second radius of curvature (R ₂ ) is too small, the side surface of the insulating film in contact with the upper surface of the insulating film 101 is cut off, so that the upper end portion of the insulating film 101 has a curved surface. The effect of preventing disconnection of the EL film is low. For this reason, the second curvature radius must be at least 0.2 μm or more.

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

  By providing the curvature radius 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 disconnection of the EL film and the cathode is prevented. It becomes easy. 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.

  By the way, FIG. 1B shows a structure that can more effectively prevent the disconnection of the cathode from FIG. In FIG. 1B, an insulating film 201 is selectively provided over an electrode, for example, an anode 200, and an EL film 202 is formed over the insulating film 201 and a cathode 203 is formed over the EL film. The feature of FIG. 1B is that the side surface of the insulating film is curved, including the upper part of the insulating film.

  A cross-sectional shape of the insulating film illustrated in FIG. 1B will be described in detail with reference to FIG.

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

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

  (8) In addition to the configuration of (7), the present invention is characterized in that the taper angle θ of the inclined surface is not less than 35 ° and not more than 70 ° in the central portion 205 of the insulating film.

(9) The present invention includes an EL element having one electrode of the EL 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 the center of curvature (O ₁ ) and the first radius of curvature (R ₁ ) above the 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 the center of curvature (O ₂ ) and the second radius of curvature (R ₂ ) below the upper end portion. In addition to making the lower end portion and upper side surface of the insulating film curved, it is preferable that the taper angle of the inclined surface at the central portion 205 of the insulating film is 35 ° to 70 ° (FIG. 3A). FIG. 3 (B)).

(10) In addition to the configuration of (9) above, the first curvature radius (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 in contact with the anode 200 is cut off. Therefore, even if the lower end of the insulating film 201 is curved, the EL The effect of preventing disconnection of the film and local thinning of the EL film is low. For this reason, the first curvature radius needs to be at least 0.2 μm or more. However, if the first radius of curvature is too large, there will be a wide area where the thickness of the insulating film is thin, and it will be difficult to cover the TFT element with the insulating film. 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. Also in terms of process, if 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.

(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 portion 206 of the insulating film has a lower center of curvature (O ₂ ) The curved surface shape is determined by the _second center of curvature (R ₂ ). In this way, by gently changing the surfaces on which the EL film and the cathode are formed, disconnection of the cathode due to a reduction in the thickness of the cathode on the surface of the insulating film can be prevented. The second radius of curvature (R ₂ ) of the upper portion 206 may be determined in consideration of the distance between adjacent anodes. In FIG. 1B and FIG. 3, the upper end portion 206 of the insulating film has a curved surface, which is effective in preventing disconnection of the cathode layer due to a sudden change in angle.

  2 to 3, the taper angle θ of the inclined surface from the lower end to the upper end (or upper portion) 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 with each other. 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 the cathode, and prevents concentration of the electric field due to locally thinning of the EL film. preferable.

Note that when the above EL film is an organic EL film formed of an organic material, direct current driving and low voltage driving are possible, and a display device with low power consumption can be manufactured.

  Although the description has focused on an active matrix display device, the present invention can be applied to either a passive matrix type or an active matrix type. This is because, depending on the shape of the insulating film, disconnection of the cathode and the EL film, and local reduction in the film thickness of the EL film can be effectively prevented.

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

  As described above, by using the present invention as described above, in a display device using an EL element, the uniformity of the film thickness of the EL film and the cathode which are formed with the side surfaces of the bumps on the electrodes being curved is improved. Thus, disconnection of the EL film and the cathode can be prevented, the yield of EL elements can be increased, and display quality can be improved.

  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 the insulating film is etched using a reactive gas, the cross-sectional shape of the insulating film in FIG. 1A can be manufactured by gradually changing the flow rate ratio of the reactive gas. An 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. An anode 422 of an organic EL element that is electrically connected 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.

  As a 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 on the substrate. Thereafter, 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. Furthermore, 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.

  As a 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. 4A).

As 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 rate ratio of the first reactive gas and the second reactive gas is changed over time. A method of etching a polyimide resin film using the first reactive gas CF ₄ , the second reactive gas O _2, and an inert gas He as an etching gas will be exemplified. As the gas flow ratio of the first reactive gas CF ₄ is larger, the polyimide resin film 303 is more easily etched than the resist film 302. That is, the depth (Y) at which the polyimide resin film 303 is etched in the film thickness direction becomes larger than the width (X) in which the side surface portion of the resist film 302 recedes to the inside of the resist film. The taper angle of the inclined surface of the insulating film determined depending on the value increases. That is, when 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 is sharp.

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

Therefore, by gradually changing the flow rate 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 changed gently.

As the first etching process, RIE (Reactive Ion Etching) is used, and the first reactive gas CF ₄ , the second reactive gas O ₂ , and the inert gas He are used as the etching gas. When etching is started, 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 increases with time, and finally the CF ₄ , O _2, and He The gas flow rate ratio is set to 7/93/40 (sccm). Increasing the flow rate ratio of the first reactive gas CF ₄ increases the taper angle of the inclined surface of the insulating film. Therefore, by continuously changing the taper angle of the inclined surface in fine steps, the side surface of the insulating film becomes curved. The curvature radius of this curved surface is referred to as a first curvature radius. The first radius of curvature is preferably 0.2 μm or more and 3.0 μm or less. In this manner, the first region 318 is formed on the side surface of the insulating film (FIG. 4B).

  Etching conditions performed in the first etching step are referred to as first etching conditions.

Note that, when the time change of the gas flow rate ratio of the first reactive gas CF ₄ is moderated under the first etching condition, the slope of the side surface of the insulating film gradually changes, so that the first radius of curvature increases. Conversely, in the first etching, the first curvature radius is reduced by making the time change of the gas flow rate ratio of the first reactive gas CF ₄ abrupt.

Thereafter, etching is performed without removing the resist film. In the second etching step, CF ₄ , O _2, and He are used as they are for the etching gas, and the gas flow ratio of the first reactive gas CF ₄ , the second reactive gas O ₂ , and the inert gas He. Is kept constant at 7/93/40 (sccm) and etching is continued. Thereby, a region where the taper angle of the inclined surface is constant is formed on the side surface of the insulating film 303. Thus, a second region 319 is formed on the side surface of the insulating film. The taper angle of the inclined surface of the insulating film formed in the second etching process is determined by the final gas flow rate ratio in the first etching process. The taper angle of the inclined surface of the insulating film increases as the ratio of the first reactive gas CF ₄ to the _second reactive gas O ₂ increases. In the second region 319, the taper angle of the side surface of the insulating film is preferably 35 ° to 70 °.

  In the etching under the second etching condition, since anisotropic etching is performed with a reactive gas, the shape of the first region 318 on the side surface of the insulating film formed in FIG. 4B is maintained. And transferred to the lower side of the polyimide resin film.

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

Next, a third etching process is performed. The third etching condition is changed without removing the resist film, and CF ₄ , O _2, and He are used as etching gases as they are, and the ratio of the first reactive gas CF ₄ to the _second reactive gas O _{2 is changed} . Will be reduced every hour. For example, the gas flow ratio of CF ₄ , O _2, and He is changed over time from 7/93/40 (sccm) to 1.5 / 98.5 / 40 (sccm). Thereby, the taper angle of the inclined surface of the insulating film is gradually reduced to form a curved surface. The curvature radius of this curved surface is referred to as a second curvature radius. A third region 320 of the insulating film 307 is formed under the third etching condition.

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

  Etching is performed by generating plasma by applying 500 W of RF (13.56 MHz) power at a pressure of 65 Pa in common in the first etching condition, the second etching condition, and the third etching condition.

  Thus, 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 portion of the insulating film. The second region includes the central portion of the insulating film. The third region includes the upper end portion of the insulating film.

  Thereafter, the resist film 306 is removed as a fourth step, and an EL film 423 is formed over the insulating film and the electrode as a fifth step. Further, an EL element is formed by forming the cathode 424 over the EL film (FIG. 5B).

  Note that a cross section indicated by a chain line B-B ′ in FIG. 5B corresponds to a cross section obtained by cutting the top view of FIG. 9 along the chain line B-B ′. The same parts as those in FIG. 9 are given the same reference numerals.

Etching using 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, an inorganic material can also be used as the insulating film. For example, when a SiO ₂ film is used as the insulating film, CHF ₃ may be used as the first reactive gas and O ₂ may be used as the second reactive gas. Then, as described above, in the first etching process, the second etching process, and the third etching process, 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 is increased, etching in the film thickness direction of the insulating film proceeds more easily, and the taper angle of the inclined surface becomes higher. In this manner, even when the material in the above step is replaced, the first region 318 and the third region 320 of the insulating film are formed in a curved shape, and the second region 319 is formed as in FIG. It is possible to make the inclined surface of the constant inclination.

  However, since the inorganic insulating film reflects the unevenness on the lower side, 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 may be previously polished by CMP (Chemical Mechanical Polish), and then a resist film is formed, and the inorganic insulating film is etched to form bumps.

  A method for manufacturing the shape of FIG. 1B using a polyimide resin film will be described with reference to FIGS.

  The polyimide resin film is an organic film containing polyamic acid as a main component before thermosetting, and is dehydrated and condensed into a polyimide film by thermosetting. In the embodiment described with reference to FIGS. 4 to 5, the resin film before and after thermosetting is described as a polyimide resin film because it is not necessary to distinguish between them. However, in the process shown by FIG. 6, since the difference in the chemical characteristics of a polyamic acid and a polyimide is utilized, the difference is specified and demonstrated.

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

  Thereafter, as a 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, a resist film 308 is formed on the organic film 309 as a third step. The thickness of the resist film is preferably about 0.5 μm to 3.0 μm. Then, as a fourth step, the resist film is exposed by irradiating ultraviolet rays through a photomask (FIG. 6A).

  And as a 5th process, it develops by immersing the resist film and organic film on a board | substrate in the developing solution which has basicity. As the developer, for example, a tetramethylammonium hydroxide (TMAH) developer having a concentration of 2.0 to 6.0% can be used. First, a portion of the resist film that has been exposed to irradiation with ultraviolet rays is dissolved in the developer. Thereafter, the organic film 311 containing polyamic acid as a main component is isotropically etched using a resist film as a mask with a basic developer. Although the polyimide resin film 311 below the resist film 310 is generally protected by the resist film and remains, the polyimide resin film below the end 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. An example of the resist film solvent is NMP (N-methyl-2-pyrrolidone).

  Thereafter, as the seventh step, the organic film is dehydrated and condensed and 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 changed to a polyimide resin film. With the imidization, the polyimide resin film contracts inward, and the surface of the polyimide resin film 312 is rounded (FIG. 6C).

  In this manner, 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 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 portion of the insulating film.

The second region 322 is somewhat rounded due to thermal contraction 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 °.

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

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

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

  For example, a resist film is patterned on the insulating film, and after the insulating film is isotropically etched, the resist film is removed. After that, when the insulating film is etched by RIE (Reactive Ion Etching), a reactive gas is likely to hit the portion where the side surface of the insulating film is in contact with the upper surface, 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.

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

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

  Next, the resist film is exposed and developed. The resist film 327 is formed so as to overlap with 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 process. For example, when etching is performed by generating plasma, it is known that the etching proceeds isotropically if the etching pressure is increased (practical dry etching technology REALIZE INC. P. 40). The insulating film below the end portion of the resist film is etched away by etching, so that the insulating film 326 having a curved side surface remains (FIG. 19B).

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

  Next, the insulating film is etched by RIE (Reactive Ion Etching). Plasma with an ionization degree of 0.1 to 1% is formed at a pressure of 0.1 to 1 Torr. In the etching using the RIE method, the reactive gas and the insulating film chemically react 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 (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 the method for manufacturing the cross-sectional shape of FIG. 1A or FIG.

  A manufacturing method when a photosensitive organic material is used as the insulating film is illustrated in FIG. By exposing the photosensitive material and etching with a developer, the cross-sectional shape can be smoothed. As the organic material, a photosensitive polyimide resin film or a photosensitive acrylic film can be used. The photosensitive organic material is preferably a positive type.

  For example, a photosensitive polyimide resin film 316 is applied with 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, thereby photosensitive polyimide. The solvent contained in the resin film is removed. After that, the photosensitive polyimide resin film is exposed by irradiating ultraviolet rays 313 through a photomask in which a chromium film 315 is formed on the quartz glass 314 (FIG. 7A).

  In the present invention, the ultraviolet rays that have passed through the photomask are intentionally diffracted during exposure. In ordinary exposure equipment, the light that has passed through the 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 photomask pattern is accurately transferred onto the film. However, in the present invention, when exposing the photosensitive polyimide resin film, the substrate is intentionally disposed 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 irradiated onto the photosensitive polyimide resin film. Light (ultraviolet rays 313) irradiated to the photosensitive resin enters the inside of the chromium film 315 formed on the photomask by diffraction.

  When exposing the photosensitive polyimide resin film, 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 reflecting the intensity distribution of diffracted light at the time of exposure. By adjusting the exposure and development conditions, the surface of the insulating film can be made gentle. After the development, the insulating film 317 is baked and thermally cured. (FIG. 7B). In addition, when exposing the photosensitive resin film, the diffracted light is incident on the surface of the photosensitive resin in a portion shielded by the photomask, so that not only the cross-sectional shape of FIG. A cross-sectional shape of 1 (B) can also be produced.

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

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

  In addition, the shape of the cross section of the bump manufactured according to the above-described embodiment can be easily confirmed by cutting the substrate on which the bump is formed and observing the cross section with a scanning electron microscope (SEM). it can.

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

  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 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, but the present invention can be applied to either of them.

  FIG. 8 shows a state where an n-channel TFT 452 and a p-channel TFT 453 are formed in the driver circuit portion 450, and a switching TFT 454 and a 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 with an insulating film formed thereon may be used. Further, a plastic substrate having heat resistance that can withstand the processing temperature of this embodiment may be used.

  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 or a polyimide resin film.

  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 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, or the like is formed using these TFTs.

  In the pixel portion 451, the data wiring 414 is connected to the source side of the switching TFT 454, and the drain side wiring 415 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 drain side electrode 416 is connected to the cathode of the EL element. FIG. 9A shows a top view of such a pixel, and uses the same reference numerals as those in FIG. 8 for convenience. Further, in FIG. 9A, a cross section corresponding to the 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 manufactured using 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.

  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 diffraction when exposing the photosensitive polyimide resin film is positively utilized to make the surface of the photosensitive resin film a gentle curved surface. Diffraction occurs 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, a vapor deposition method is used. When a high molecular material is used, a spin coating method, a printing method, an ink jet method, or the like is used.

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

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

  There are four main types of color display, a method of 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. A method that combines a blue or blue-green light emitting EL element and a phosphor (fluorescent color conversion layer: CCM), a method that uses a transparent electrode for the cathode (counter electrode), and stacks the EL elements corresponding to RGB. There is.

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

  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 embodiment has a structure in which a light-emitting layer and a hole injection layer made of PEDOT (polythiophene) or PAni (polyaniline) are provided.

  On the EL film 423, a cathode 424 of an EL element is provided. As the cathode 424, a material containing magnesium (Mg), lithium (Li), or calcium (Ca) having a low work function is used. An electrode made of MgAg (a material in which Mg and Ag are mixed at Mg: Ag = 20: 1) is preferably used. Other examples include MgAgAl electrodes, LiAl electrodes, and LiFAl electrodes.

  The cathode 424 is preferably formed continuously after the EL film 423 is formed without being released to the atmosphere. This is because the interface state between the cathode 424 and the EL film 423 greatly affects the light emission efficiency of the EL element. Note that in this specification, a light-emitting element formed using an anode (pixel electrode), an EL film, and a cathode is referred to as an EL element.

  A stacked body including the EL film 423 and the cathode 424 needs to be formed individually for each pixel. However, since the EL film 423 is extremely weak against moisture, a normal photolithography technique cannot be used. In addition, the cathode 424 manufactured using an alkali metal is easily oxidized. Accordingly, it is preferable to use a physical mask material such as a metal mask and selectively form the film by a vapor phase method such as a vacuum deposition method, a sputtering method, or a plasma CVD method. As a method for selectively forming the EL film, an ink jet method, a screen printing method, or the like can be used. However, since the cathode cannot be continuously formed at present, the above method is preferable.

  Further, a protective electrode for protecting from external moisture or the like may be stacked 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 a direction indicated by an arrow in FIG. 8 (this is called 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 when no light is emitted without using a polarizing plate. The protective electrode can also be expected to have a heat dissipation effect that alleviates the heat generation of the EL film. It is also effective to form the protective electrode continuously after the EL film 423 and the cathode 424 are formed without being released 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 and an EL film 1103 made of an insulating film are formed. Further, LiFAl and MgAg are formed as the cathode 1104 with a thickness of 10 to 50 nm so as to have optical transparency. Further, a transparent conductive film 1105 is formed on the cathode for the purpose of lowering the wiring resistance. Thereby, in FIG. 17, light can be emitted in the direction indicated by the arrow. At this time, since the cathode has light transmittance, glare of the display screen when no light is emitted can be suppressed.

  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 exhibits a high operation speed, deterioration such as hot carrier injection is likely to occur. Therefore, it is highly reliable to form TFTs with different structures (switching TFTs with sufficiently low off-state current and TFTs for current control strong against hot carrier injection) having different structures depending on functions in the pixels, and This is very effective in manufacturing a display device capable of displaying a good image (high operation performance).

  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 wiring and the data wiring, and a switching TFT 454, a current control TFT 455, and an EL element 456 are provided in the pixel.

  The switching TFT 454 has a gate electrode 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 power supply line 417 is connected to the source side of the current control TFT, and the EL element 456 is connected to the drain side of the current control TFT.

  Reference numeral 457 denotes a current control TFT of an adjacent pixel. 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 for 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 varies depending on the configuration of the EL element, but here, light is emitted upward and display is performed. In the structure illustrated in FIG. 12, an element substrate 601 over which a driver circuit portion 604, a driver circuit portion 605, and a pixel portion 603 are formed using TFTs and a sealing substrate 602 are attached to each other with a sealant 610. An input terminal 608 is provided at the end of the element substrate 601, and an FPC (Flexible Print Circuit) is connected to this portion. 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 drive circuit unit. Further, 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 necessary.

  As shown in FIG. 11, the input terminal is formed by laminating a wiring 705 made of titanium (Ti) and aluminum (Al) and ITO 706 formed as an anode. FIG. 11 shows a cross-sectional view corresponding to the line CC ′ in the input terminal portion. The element substrate 701 and the sealing substrate 702 are bonded to each other with a sealant 703. In the drive circuit portion, the EL film 707 and the cathode 708 are formed on the bump 709, but a contact portion 720 as shown is provided to make the cathode 708 contact the wiring. Also in the contact part 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 surfaces of the bumps have gentle curved surfaces, so that disconnection of the EL film and the cathode can be prevented and the yield of the display device can be increased.

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

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

  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 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, or the like is formed using these TFTs.

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

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

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

  In addition, if the TFT structure 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 inversely staggered TFT using polysilicon has an advantage that it can be manufactured by diverting an amorphous silicon TFT (usually formed by an inversely staggered TFT) production line. 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 lower.

  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, a pixel portion 921 including a pixel 920, a data signal side driver circuit 915 used for driving the pixel portion, and a gate signal side driver circuit 914 are formed by TFTs formed over a substrate. The data signal side driving circuit 915 is an example of digital driving, and includes a shift register 916, 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 (none of which are shown).

  In the case of VGA, the pixel portion 921 has 640 × 480 (horizontal × vertical) pixels, and a switching TFT and a current control TFT are arranged in each pixel as described in FIG. 8 or FIG. ing. As for the operation of the EL element, when the gate wiring is selected, the gate of the switching TFT is opened, the data signal of the source wiring is accumulated in the capacitor, and the gate of the current control TFT is opened. 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.

  The system block diagram shown in FIG. 14 shows the form of a portable information terminal such as a PDA. In the display device shown in Embodiment 1, a pixel portion 921, a gate signal side driver circuit 914, and a data signal side driver circuit 915 are formed.

  The configuration of the external circuit connected to the display device is as follows: a power supply circuit 901 including a stabilized power supply and a high-speed and high-precision operational amplifier; an external interface port 902 including a USB terminal; a CPU 903; a pen input tablet 910 used as input means; The circuit 911, a clock signal oscillator 912, a control circuit 913, and the like.

  The CPU 903 incorporates a video signal processing circuit 904, a tablet interface 905 for inputting signals from the pen input tablet 910, and the like. Further, a VRAM 906, a DRAM 907, a flash memory 908, and a memory card 909 are connected. 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 timing specifications of the data signal side driving circuit 915 and the gate signal side driving circuit 914.

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

  It is desired that a portable information terminal such as a PDA can be used for a long time outdoors or in a train with a rechargeable battery as a power source without being connected to an AC outlet. In addition, such electronic devices are required to be lighter and smaller at the same time with emphasis on ease of carrying. Batteries that occupy most of the weight of electronic devices increase in weight when 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 or setting the standby mode.

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

  In order to display a still image, functions such as the video signal processing circuit 904 and the VRAM 906 of the CPU 903 are stopped, so that power consumption can be reduced. In FIG. 14, the part that performs the operation is indicated by a dotted line. Further, as shown in FIG. 12, the controller 913 may use an IC chip and may be mounted on the element substrate by the COG method, or may be integrally formed inside the display device.

  In this embodiment, an organic compound that emits light by singlet excitons (hereinafter referred to as singlet compound) and an organic compound that emits light by triplet excitons (triplet) (hereinafter referred to as triplet compounds) are used in combination as the EL film. An example will be described. The singlet compound refers to a compound that emits light only through singlet excitation, and the triplet compound refers to a compound that emits light via triplet excitation.

  As the triplet compound, organic compounds described in the following papers can be cited 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, DF O'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.

  In addition to the luminescent material described in the above paper, it is considered possible to use a luminescent material represented by the following molecular formula (specifically, a metal complex or an organic compound).

  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. In addition, the present inventor believes that nickel, cobalt, or palladium is preferable for reducing the manufacturing cost of the light emitting device because it is cheaper than platinum or iridium. In particular, nickel is considered preferable because it is easy to form a complex and has high productivity.

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

  When a low molecular organic compound is used as the light emitting layer, the lifetime 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 light emission efficiency is inferior to that of other colors, so that the operating voltage must be set high in order to obtain the same light emission luminance as the other colors, and the deterioration progresses accordingly.

  However, since a triplet compound having high luminous efficiency is used as the light emitting layer emitting red light in this embodiment, the operating voltage is adjusted while obtaining the same light emission luminance as the light emitting layer emitting green light and the light emitting layer emitting blue light. It is possible. Therefore, the deterioration of the light emitting layer emitting red light is not accelerated rapidly, and color display can be performed without causing problems such as color misregistration. In addition, it is preferable that the operating voltage can be kept low from the viewpoint that the breakdown voltage margin of the transistor can be set low.

  In this embodiment, an example is shown in which a triplet compound is used as a light emitting layer that emits red light. However, a triplet compound can also be used for a light emitting layer that emits green light or a light emitting layer that emits blue light. .

  In the case of performing 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, a triplet compound can be used for an EL element that emits red light, and the others can be formed using a singlet compound.

  In this way, by properly using the triplet compound and the singlet compound, the operating voltages of the respective EL elements can all be the same (20 V or less, preferably 3 to 20 V). Therefore, since the power source required for the display device can be unified at, for example, 3V or 5V, there is an advantage that the circuit design is facilitated. In addition, the structure of a present Example can be implemented in combination with any structure of Example 1- Example 3.

  A display device formed by implementing the present invention is built in various electric appliances, and a pixel portion is used as an image display portion. 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, and an image reproducing device provided with a recording medium, such as a DVD (Digital Versatile Disc) player and a digital camera. Specific examples of these electronic devices are shown in FIGS.

  FIG. 15A illustrates a mobile phone, which includes a display panel 9001, an operation panel 9002, and a connection portion 9003. The display panel 9001 is provided with a display device 9004, an audio output portion 9005, an antenna 9009, and the like. . The operation panel 9002 is provided with operation keys 9006, a power switch 9007, a voice input unit 9008, and the like. The present invention can be applied to the display device 9004.

  FIG. 15B also illustrates a mobile phone, which includes a main body or a housing 9101, a display device 9102, an audio output portion 9103, an audio input portion 9104, and an antenna 9105. The display device 9102 may incorporate a touch 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, the substrate can be curved after the display device is completed. Taking advantage of such characteristics, it can be incorporated into a housing having a three-dimensional curved surface designed based on ergonomics without a sense of incongruity.

  FIG. 15C illustrates a mobile computer or a portable information terminal, which includes a main body 9201, a camera portion 9202, an image receiving portion 9203, operation switches 9204, and a display device 9205. The present invention can be applied to the display device 9205. For such an electronic device, a 3 inch to 5 inch class display device is used; however, by using the display device of the present invention, the weight of the portable information terminal can be reduced.

FIG. 15D illustrates a portable book which includes a main body 9301, a display device 9303, a storage medium 9304, operation switches 9305, and an antenna 9306, and includes data stored in a minidisc (MD) or DVD, and an antenna. The received data is displayed. The present invention can be used for the display device 9303. A portable book uses a 4-inch to 12-inch class display device, but by using the display device of the present invention, the portable book can be reduced in weight and thickness.

  FIG. 15E illustrates 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 illustrates a personal computer which includes a main body 9601, an image input portion 9602, a display device 9603, 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) in which a program is recorded. The player includes a main body 9701, a display device 9702, a speaker portion 9703, a recording medium 9704, and operation switches 9705. This apparatus uses a DVD (Digital Versatile Disc), CD, or the like as a recording medium, and can perform music appreciation, movie appreciation, games, and the Internet. The present invention can be applied to the display device 9702.

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

  FIG. 16D also illustrates 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 housing having a three-dimensional curved surface designed based on ergonomics without a sense of incongruity.

  Further, in the cellular phone operation shown in FIGS. 15A and 15B, the power consumption can be reduced by increasing the luminance when using the operation keys and decreasing the luminance when the operation switch is used. . Further, the power consumption can be reduced by increasing the brightness of the display device when an incoming call is received and decreasing the brightness during a call. Further, in the case of continuous use, it is possible to reduce power consumption by providing a function of turning off the display by time control unless resetting. Note that these may be manual control.

  Although not shown here, the present invention can also be applied to a display device incorporated in a navigation system, a refrigerator, a washing machine, a microwave oven, a fixed telephone, a facsimile, and the like. Thus, the application range of the present invention is very wide and can be applied to various products.

Sectional drawing explaining the cross section of the EL element in this invention. Sectional drawing explaining the cross section of the bump in this invention. Sectional drawing explaining the cross section of the bump in this invention. Sectional drawing explaining the manufacturing process of the bump of this invention (embodiment). Sectional drawing explaining the manufacturing process of the bump of this invention (embodiment). Sectional drawing explaining the manufacturing process of the bump of this invention (embodiment). Sectional drawing explaining the manufacturing process of the bump of this invention (embodiment). Sectional drawing explaining the structure of the drive circuit and pixel part of a display apparatus (Example 1). 4A and 4B are a top view and an equivalent circuit diagram illustrating a structure of a pixel portion of a display device (Example 1). FIG. 6 illustrates a configuration of an input terminal portion of a display device (Example 1). FIG. 6 illustrates a configuration of an input terminal portion of a display device (Example 1). 1 is a perspective view showing an external appearance of an EL display device of the present invention (Example 1). FIG. Sectional drawing explaining the structure of the drive circuit and pixel part of a display apparatus (Example 2). FIG. 12 is a system block diagram of an electronic device incorporating a display device (Example 3). FIG. 10 illustrates an example of an electronic device (Example 5). FIG. 10 illustrates an example of an electronic device (Example 5). The figure which shows the radiation | emission direction of the light of an EL element (Example 1). The figure explaining the shape of the bump of a prior art example. Sectional drawing explaining the manufacturing process of the bump of this invention (embodiment). The figure explaining the shape of the bump of this invention.

Claims (25)

In 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, the electrode is selectively formed so as to cover an end portion of the one electrode. Have bumps,
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 a side surface of the lower end portion is in contact with an ellipse or circle having a center above the one electrode, and a side surface of the upper end portion is in contact with an ellipse or circle having a center inside the bump. In 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, the electrode is selectively formed so as to cover an end portion of the one electrode. Have bumps,
The side surface of the bump has a lower end portion in contact with the upper surface of the one electrode, an upper end portion continuous with the flat upper surface of the bump, and a central portion between the lower end portion and the upper end portion, The lower end is in contact with an ellipse or circle having a center above the electrode,
The surface in contact with the central portion has an angle with respect to the upper surface of the one electrode of 35 ° to 70 °,
The display device, wherein the upper end portion is in contact with an ellipse or a circle having a center inside the bump. In 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, the electrode is selectively formed so as to cover an end portion of the one electrode. Have bumps,
The lower end of the bump in contact with the upper surface of the one electrode has a curved side surface in contact with a circle having a center of curvature above the tangent line between the one electrode and the lower end and a first radius of curvature,
The upper end of the bump is continuous with the flat upper surface of the bump,
An upper end portion of the bump has a curved side surface in contact with a circle having a center of curvature below a boundary between the upper end portion and the upper surface and a second radius of curvature. In 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, the electrode is selectively formed so as to cover an end portion of the one electrode. Have bumps,
The lower end of the bump in contact with the upper surface of the one electrode has a curved side surface in contact with a circle having a center of curvature above the tangent line between the one electrode and the lower end and a first radius of curvature,
The surface in contact with the side surface of the central portion of the bump has an angle with respect to the upper surface of the one electrode of 35 ° or more and 70 ° or less,
The upper end of the bump is continuous with the flat upper surface of the bump,
An upper end portion of the bump has a curved side surface in contact with a circle having a center of curvature below a boundary between the upper end portion and the upper surface and a second radius of curvature. In any one of Claims 1 thru | or 4,
From the lower end portion to the upper end portion of the side surface of the bump, the angle of the surface in contact with the side surface of the bump with respect to the upper surface of the one electrode continuously changes, and the angle is in the range of 0 ° to 70 °. A display device characterized by that. In any one of Claims 3 thru | or 5,
The display device, wherein the first curvature radius and the second curvature radius are 0.2 μm or more and 3.0 μm or less. In any one of Claims 4 thru | or 6,
A display device, wherein the bump has a thickness of 1.0 μm to 3.0 μm. In 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, the electrode is selectively formed so as to cover an end portion of the one electrode. Have bumps,
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, and the surface in contact with the side surface of the bump from the lower end portion to the upper end portion is The display device is characterized in that an angle with respect to the upper surface of the one electrode continuously changes, and the angle is in a range of 0 ° to 70 °.   5. The display device according to claim 1, wherein the other electrode is formed so as to overlap with an upper end portion and a lower end portion of the bump. . In claim 2, claim 4, claim 5, claim 6 or claim 7,
The display device, wherein the other electrode is formed so as to overlap an upper end portion, a central portion, and a lower end portion of the bump. In 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, the electrode is selectively formed so as to cover an end portion of the one electrode. Have bumps,
The surface of the bump has a lower end contacting the upper surface of the one electrode, and an upper end.
The lower end of the bump in contact with the upper surface of the one electrode has an elliptical or circular surface having a center on the one electrode,
An upper end portion of the bump has an elliptical or circular surface having a center inside the surface of the bump. In 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,
A bump selectively formed covering an end of the one electrode;
The lower end of the bump in contact with the upper surface of the one electrode has a curved side surface in contact with a circle having a center of curvature above the tangent line between the one electrode and the lower end and a first radius of curvature,
An upper end portion of the bump has a curved surface determined by a center of curvature below the upper end portion and a second radius of curvature. In 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, the electrode is selectively formed so as to cover an end portion of the one electrode. Have bumps,
The lower end of the bump in contact with the upper surface of the one electrode has a curved side surface in contact with a circle having a center of curvature above the tangent line between the one electrode and the lower end and a first radius of curvature,
The surface in contact with the side surface of the central portion of the bump has an angle of 35 ° to 70 ° with respect to the upper surface of the one electrode.
An upper end portion of the bump has a curved surface determined by a center of curvature below the upper end portion and a second radius of curvature. In any one of claims 11 to 13,
The angle of the surface in contact with the surface of the bump to the upper surface of the electrode continuously changes from the lower end portion to the upper end portion of the bump surface, and the angle is in the range of 0 ° to 70 °. Characteristic display device. In any one of Claims 12 to 14,
The display device, wherein the first curvature radius and the second curvature radius are 0.2 μm or more and 3.0 μm or less. In any one of Claims 11 thru | or 15,
A display device, wherein the bump has a thickness of 3.0 μm or less. In claim 11, claim 12, claim 14, claim 15 or claim 16,
The display device, wherein the other electrode is formed so as to overlap a lower end portion and an upper end portion of the bump. In claim 13, claim 14 or claim 16,
The display device, wherein the other electrode is formed so as to overlap an upper end portion, a central portion, and a lower end portion of the bump. In any one of claims 1 to 18,
The display device, wherein the electrode is an anode or a cathode. In any one of claims 1 to 19,
The display device, wherein the EL element has an EL film made of an organic material on the electrode and the bump.   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. 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 the insulating film by etching the insulating film using at least a first reactive gas and a second reactive gas;
A fifth step of removing the resist film;
A sixth step of forming an EL film on the insulating film,
In the fourth step, the first etching step in which the flow rate ratio of the first reactive gas to the second reactive gas increases with time, and the flow rates of the first reactive gas and the second reactive gas. A display device comprising: a second etching step in which the ratio is constant; and a third etching step in which a flow rate ratio of the first reactive gas to the second reactive gas decreases with time. Manufacturing method. In claim 21,
The method for manufacturing a display device, 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 first step of applying an organic film mainly composed of polyamic acid on the electrode;
A second step of heat-treating the organic film at a temperature of 50 ° C. or higher and 150 ° C. or lower;
A third step of forming a resist film on the organic 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 having 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 higher and 350 ° C. or lower to form a polyimide resin film;
And a eighth step of forming an EL film over the polyimide resin film.   25. A method for manufacturing a personal computer, a video camera, a portable information terminal, a digital camera, a digital video disc player, or an electronic game machine, using the method for manufacturing a display device according to any one of claims 22 to 24.

Images