JP2005024940A - Liquid crystal display device and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device with high reliability without making a manufacturing process complex, and a method of manufacturing the same. <P>SOLUTION: The liquid crystal display device has an interlayer insulating film 5 covering a semiconductor film 2 in a thin film transistor, a source drain electrode 6 placed on the interlayer insulating film and conductively connecting to a source drain region of the thin film transistor, a passivation film 7 having an opening part on the center of an upper surface of the source drain electrode and covering the source drain electrode and the interlayer insulating film, an organic resin film 9 having an opening part which includes the opening part of the passivation film seen from a two-dimensional direction and covering the passivation film and a reflection electrode 12 covering the source drain electrode, the passivation film and the organic resin film. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device and a manufacturing method thereof, and more specifically to a liquid crystal display device including a reflective electrode for each pixel and a manufacturing method thereof.
[0002]
[Prior art]
The liquid crystal itself does not emit light, and exhibits a display function by controlling external light transmitted through the liquid crystal. There are roughly the following two apparatuses as mechanisms for transmitting liquid crystal to external light and developing a display function. (A1) A backlight is disposed behind the liquid crystal when viewed from the observer, and a transmissive liquid crystal display device that transmits the liquid crystal to the light emitted from the backlight; and (a2) the light is transmitted from the front to the liquid crystal; There is a reflective liquid crystal display device in which light is reflected by a reflector disposed behind the liquid crystal and the liquid crystal is transmitted from the rear. There is also a (a3) reflection / transmission type liquid crystal display device combining a transmission type and a reflection type.
[0003]
In recent years, demand for low power consumption has increased, and instead of a transmissive liquid crystal display device that requires a backlight for display, a reflective liquid crystal display device or a reflective / transmissive liquid crystal display that combines transmission and reflection is used. The development of equipment is being actively conducted. In these reflective liquid crystal display devices and reflective / transmissive liquid crystal display layers, a reflective electrode is provided in an electrode portion for applying a voltage to liquid crystal. For this reflective electrode, to obtain a bright display by increasing the reflectivity, to improve the adhesion with the underlying insulating film, and to facilitate processing without complicating the process, Many proposals have been made (for example, see Patent Documents 1-5).
[0004]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2000-0472201
[Patent Document 2]
Japanese Patent Laid-Open No. 2001-194677
[Patent Document 3]
Japanese Patent Laid-Open No. 11-242240
[Patent Document 4]
Japanese Patent Laid-Open No. 11-218751
[Patent Document 5]
Japanese Patent Laid-Open No. 60-123877
[Problems to be solved by the invention]
In such a reflective liquid crystal display device and a reflective / transmissive liquid crystal display device, it is necessary to separate a source / drain electrode (hereinafter referred to as a drain electrode) and a reflective electrode. For this reason, after forming a passivation film made of an inorganic insulating film such as a silicon nitride film, a contact hole (opening) for establishing electrical conduction between the drain electrode and the reflective electrode is formed in the passivation film. . Thereafter, an organic resin film having a contact hole (opening) at the same position as the contact hole is formed in order to form unevenness for scattering incident light and then to establish electrical continuity between the drain electrode and the reflective electrode. It is formed by photolithography. Further, a reflective electrode formed as described above and covering the inside of the contact hole and in contact with the drain electrode is formed on the organic resin film. For the reflective electrode, an Al film or an Al alloy film having a high reflectance is used.
[0010]
In the manufacturing method as described above, the contact hole needs to be formed at the same position in both the passivation film and the organic resin film. For this reason, if attention is paid only to the formation of the contact hole, the photolithography process is performed twice with the same mask. This complicates the manufacturing process.
[0011]
The present invention has been made to solve such a problem, and an object of the present invention is to provide a highly reliable liquid crystal display device and a manufacturing method thereof without complicating the manufacturing process.
[0012]
[Means for Solving the Problems]
The liquid crystal display device of the present invention includes a thin film transistor (TFT) located on an insulating substrate and a liquid crystal located on the thin film transistor and to which a voltage is applied by the thin film transistor. This liquid crystal display device is located on an interlayer insulating film covering a semiconductor film in a thin film transistor, and has a source / drain electrode conducting to the source / drain region of the thin film transistor, and a first opening in a portion corresponding to the source / drain electrode. An inorganic insulating film that covers the source / drain electrodes and the interlayer insulating film, and an organic resin film that has a second opening that includes the first opening in plan view, and covers the inorganic insulating film. , Covering the inside of the first opening and the second opening, in contact with the source / drain electrode at the bottom of the first opening, and including the inorganic insulating film and the second opening at the bottom of the second opening A reflective electrode is provided to cover a part of the organic resin film.
[0013]
In the above liquid crystal display device, an opening (contact hole) can be provided in a passivation film which is an inorganic insulating film using an organic resin film as a mask, and the number of masks can be reduced and the manufacturing process can be simplified. Become. In the above structure, since the opening is larger in the organic insulating film than the opening in the inorganic insulating film, the opening has a step. As will be described in detail later, this structure proves that a highly reliable liquid crystal display device has been formed while omitting one mask formation step. Note that “above” in “on the insulating substrate” or “on the thin film transistor” means the front of the liquid crystal display device, in other words, the viewer side.
[0014]
The manufacturing method of a liquid crystal display device of the present invention manufactures a liquid crystal display device having a thin film transistor positioned on an insulating substrate and a liquid crystal positioned on the thin film transistor and applied with a voltage from a source / drain electrode of the thin film transistor. Is the method. The manufacturing method includes a step of applying an inorganic insulating film covering the source / drain electrode and an organic resin film covering the inorganic insulating film, and the organic resin film is formed on the source / drain electrode using a photoengraving method. And patterning the organic resin film so as to have an opening (corresponding to the second opening of the liquid crystal display device of the present invention). Further, the inorganic insulating film is patterned using the patterned organic resin film having the first opening as a mask, and the second opening (the first opening of the liquid crystal display device of the present invention described above) is formed on the source / drain electrode. And a step of performing oxygen plasma treatment after patterning the inorganic insulating film.
[0015]
According to the above manufacturing method, the passivation film, which is an inorganic insulating film, can be patterned using the organic resin film as a mask, the number of masks can be reduced, and the manufacturing process can be simplified.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
FIG. 1 shows a cross-sectional structure of a thin film transistor (TFT) having a reflective electrode in Embodiment 1 of the present invention. A silicon film 2 is formed on an insulating substrate 1 such as glass or resin, and an interlayer insulating film 5 is disposed thereon. In the interlayer insulating film 5, a gate electrode 3 is provided with an insulating film interposed between the silicon film 2. Source / drain electrodes 4 and 6 that are electrically connected to one of the source / drain regions in the silicon film 2 are formed.
[0017]
The source / drain electrodes 4 and 6 are formed by filling the contact holes with a metal film for the source / drain electrodes by sputtering after forming the contact holes. The lower portion 4 of the source / drain electrode is in contact with the source / drain region, and the upper portion 6 of the source / drain electrode is formed so as to protrude from the upper surface of the interlayer insulating film 5. An inorganic insulating film having an opening 8 in a region corresponding to the source / drain electrode, for example, a passivation film 7 made of a silicon nitride film covers the remaining portion of the source / drain electrode and the interlayer insulating film 5. The side wall bottom 14 of the opening of the passivation film 7 is located at a point entering the inside from the edge of the source / drain electrode.
[0018]
An organic resin film 9 having an opening 11 at a position corresponding to the source / drain electrode is disposed in contact with the passivation film 7. The side wall of the opening 11 of the organic resin film 9 is tapered such that the hole diameter decreases toward the bottom, and the bottom 13 of the side wall recedes from the side wall bottom 14 of the opening 8 of the passivation film 7. Yes. That is, the opening 11 provided in the organic resin film 9 has a size including the opening 8 provided in the passivation film 7 and is larger than the opening 8 provided in the passivation film 7. A reflective electrode 12 is provided so as to contact the source / drain electrode exposed at the bottom of the opening 11. The reflective electrode is formed of Al or an Al alloy. The liquid crystal is applied with a voltage from the source / drain electrode 6 through the reflective electrode 12 through an alignment film (not shown).
[0019]
Next, a method for manufacturing the liquid crystal display device will be described. The TFT is formed on the insulating substrate by a normal manufacturing method. Next, the TFTs formed up to the drain electrode made of a Cr film or Mo film are arranged in a matrix. A silicon nitride film is formed as a passivation film 7 to a thickness of about 100 nm by plasma CVD so as to cover the surface of the matrix substrate in which TFTs are arranged in a matrix. Next, an organic resin film is applied. Next, an organic resin interlayer film 9 having irregularities for scattering contact holes and incident light on the surface 9a is formed by exposing and developing by photolithography. Next, the surface of the organic resin film is cured by heat treatment at 200 ° C.
[0020]
Next, using the organic resin film in the above state as a mask, for example, dry etching treatment using CF ₄ / O ₂ gas is performed to process the silicon nitride film 7, and the source / drain electrodes 6 of the thin film transistor and the display electrode Contact holes 8 and 11 are formed for electrical connection with 12. Thereafter, carbon plasma and fluoride deposited during dry etching are removed by performing oxygen plasma processing subsequent to the dry etching processing.
[0021]
In this way, the organic resin film 9 has an opening larger than the opening of the silicon nitride film 7, and an organic resin film / silicon nitride film step is formed in which the organic resin film recedes from the silicon nitride film. At this step, the edge 13 of the organic resin film is located on the silicon nitride film 7.
[0022]
Next, an Al film of about 100 nm is formed in the contact hole and on the organic resin film 9 by sputtering. Thereafter, the reflective electrode 12 is formed by forming a photoresist pattern by photolithography and using this as a mask to etch the Al film with a phosphoric acid / nitric acid chemical solution. In this way, the reflective liquid crystal display device according to the present invention is completed.
[0023]
In the liquid crystal display device of this embodiment, at least a contact hole portion that electrically connects the thin film transistor electrode and the reflective electrode is formed by a single photolithography process by processing the passivation film using the organic resin film as a mask. . For this reason, a mask process can be reduced and productivity can be improved.
[0024]
A reflective / transmissive liquid crystal display device can be obtained by providing a transparent region in the reflective electrode and forming and processing a conductive transparent film such as ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide) on the substrate. You can also.
[0025]
Usually, a contact hole for a passivation film is formed using a resist mask. However, in the liquid crystal display device completed as described above, the number of masks can be reduced and the manufacturing process can be simplified by using the organic resin film as an etching mask for the passivation film. As a result, the edge of the opening of the organic resin film recedes so as to be positioned on the inorganic insulating film constituting the passivation film, and has an upwardly expanding taper. There is no negative effect due to the step between the passivation film and the organic insulating film in the opening and the taper of the upward spread in the organic resin film.
[0026]
(Embodiment 2)
FIG. 2 is a diagram showing a cross-sectional structure of a thin film transistor having a reflective electrode according to Embodiment 2 of the present invention. The present embodiment is characterized in that the reflective electrode has a two-layer structure. The surface layer is formed of Al or an Al alloy film, and a refractory metal is used for the back electrode layer opposite to the liquid crystal. Here, the front side is the front side of the liquid crystal display device, that is, the viewer side, and the back side means the back side. The structure of other parts is the same as that of the liquid crystal display device of the first embodiment. The manufacturing method is the same as the manufacturing method of the liquid crystal display device of FIG. 1 until the opening for making contact with the source / drain electrode is provided in the passivation film 7 and the organic resin film 9.
[0027]
After the openings 8 and 11 are provided, next, molybdenum (Mo) is deposited as a back-side electrode layer 22 to a thickness of about 25 nm in the contact holes and on the organic resin film by sputtering. Further, an Al film is deposited on the surface side electrode layer 23 by about 100 nm by the sputtering method. After that, a photoresist pattern is formed on the electrode layer by photolithography, and this is used as a mask to continuously etch the laminated film of the Mo film and the Al film with a phosphoric acid / nitric acid chemical solution. A reflective electrode is formed. Through the above processing steps, the reflective liquid crystal display device according to the present embodiment is completed.
[0028]
The thin film transistor electrode and the reflective electrode are electrically connected by forming the reflective electrode on the back surface of the Al film or Al alloy film with a refractory metal film that is hardly affected by degassing from the organic resin film. Even when the contact hole is formed by one photolithography process, it is possible to suppress the occurrence of disconnection of the reflective electrode at the step portion of the interface of the organic resin film in the contact hole portion.
[0029]
A reflective / transmissive liquid crystal display device can be obtained by providing a transparent region in the reflective electrode and forming a conductive transparent film such as ITO or IZO on the substrate and processing it.
[0030]
In the liquid crystal display device completed as described above, the step of the reflective electrode at the opening edge of the organic resin film at the opening that is likely to occur due to the influence of oxygen plasma treatment on the surface of the organic resin film There was no decrease in reflectivity.
[0031]
Here, although the refractory metal Mo film is used as the back electrode of the reflective electrode, a refractory metal such as a Ti film or a Cr film may be used. By using these refractory metals, it becomes difficult to be affected by degassing from the organic resin film, and the occurrence of disconnection at the opening edge of the organic resin film can be completely suppressed.
[0032]
Moreover, although the film thickness of the back electrode film of the reflective electrode is 25 nm here, it may be 5 to 50 nm. If it is thinner than 5 nm, the effect of preventing breakage is reduced, and if it exceeds 50 nm, the surface of the Al film on the observation side is rough due to the influence of the surface roughness of the back electrode film. Absent. FIG. 3 is a diagram illustrating the influence of the thickness of the back electrode layer on the reflectance. In this figure, the total thickness of the reflective electrode is constant at 100 nm.
[0033]
In FIG. 3, the thickness of the back side electrode layer of 100 nm indicates a case where the reflective electrode is formed of the back side electrode material Mo single layer. In this configuration, the reflectance is the lowest as described above. Further, when the reflective electrode is composed of an Al single layer without providing the back-side electrode layer, the reflectance is low, particularly in the wavelength range of 400 nm to 500 nm. When the thickness of the back electrode layer is 25 nm, a particularly high reflectance can be obtained in the wavelength range of 350 nm to 450 nm.
[0034]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
[0035]
【The invention's effect】
According to the liquid crystal display device of the present invention, a contact for electrically connecting the electrode of the thin film transistor and the reflective electrode can be formed without complicating the manufacturing process. Further, by using a reflective electrode as a laminated structure and using a refractory metal such as Mo for the back electrode layer, disconnection of the reflective electrode in the contact hole portion can be prevented. Further, by intentionally introducing the surface roughness into the surface of the reflective electrode, it is possible to suppress a decrease in reflectance. Therefore, a liquid crystal display device having bright display characteristics at low cost can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a liquid crystal display device according to Embodiment 1 of the present invention.
FIG. 2 is a cross-sectional view of a liquid crystal display device according to Embodiment 2 of the present invention.
FIG. 3 is a diagram showing a relationship between a laminated structure of reflective electrodes and reflectance.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Insulating substrate, 2 Silicon film, 3 Gate electrode, 4 Source drain electrode lower part, 5 Interlayer insulating film, 6 Source drain electrode upper part, 7 Passivation film (inorganic insulating film), 8 Passivation film opening part, 9 Organic resin film, 9a Organic resin film surface, 11 Organic resin film opening, 12 Aluminum electrode (single layer), 13 Open edge of organic resin film on passivation film, 14 Open edge of passivation film on source / drain electrode, 22 Back side electrode Layer, 23 surface side electrode layer.

Claims (8)

A liquid crystal display device comprising: a thin film transistor positioned on an insulating substrate; and a liquid crystal positioned on the thin film transistor and applied with a voltage by the thin film transistor,
A source / drain electrode located on an interlayer insulating film covering the semiconductor film in the thin film transistor and electrically connected to a source / drain region of the semiconductor film;
An inorganic insulating film having a first opening in a portion corresponding to the source / drain electrode and covering the source / drain electrode and the interlayer insulating film;
An organic resin film having a second opening that includes the first opening in plan view and covering the inorganic insulating film;
Covers the inside of the first opening and the second opening, contacts the source / drain electrode at the bottom of the first opening, and the inorganic insulating film and the first at the bottom of the second opening A liquid crystal display device having a reflective electrode that covers a part of an organic resin film including two openings. The liquid crystal display device according to claim 1, wherein the reflective electrode is formed of a laminated structure of a surface electrode layer positioned on the liquid crystal side and a back electrode layer positioned on the back side. The liquid crystal display device according to claim 1, wherein the reflective electrode is formed of any one of an Al film and an Al alloy film. The liquid crystal display device according to claim 2, wherein the surface electrode layer is formed of one of an Al film and an Al alloy film, and the back electrode layer is formed of a refractory metal layer. The liquid crystal display device according to claim 4, wherein the refractory metal layer is formed of one of a molybdenum film and a molybdenum alloy film. The liquid crystal display device according to claim 2, wherein the thickness of the back electrode layer is in the range of 5 nm to 50 nm. A method of manufacturing a liquid crystal display device comprising: a thin film transistor positioned on an insulating substrate; and a liquid crystal positioned on the thin film transistor and applied with a voltage from a source / drain electrode of the thin film transistor,
Applying an inorganic insulating film covering the source / drain electrode and an organic resin film covering the inorganic insulating film;
Patterning the organic resin film using a photoengraving method so as to have a first opening on the source / drain electrodes;
Patterning the inorganic insulating film using the patterned organic resin film having the first opening as a mask, and providing a second opening on the source / drain electrode;
And a step of performing oxygen plasma treatment after patterning the inorganic insulating film. After performing the oxygen plasma treatment, the method includes a step of forming a reflective electrode in contact with the source / drain electrode, and the reflective electrode includes a surface electrode layer on the liquid crystal side and a back electrode layer on the back side. The method for manufacturing a liquid crystal display device according to claim 7, wherein the back electrode layer is formed of a refractory metal.

Images