KR100660531B1 - TFT LCD of merged reflection- transmission type - Google Patents

Abstract

The present invention relates to a reflective transparent thin film transistor liquid crystal display device.

A reflective transparent thin film transistor liquid crystal display comprising a pixel electrode formed by superimposing an indium oxide-based transparent electrode layer and an aluminum-containing reflective electrode layer having a light-transmitting window, wherein the liquid crystal display device comprises a drain electrode of the thin film transistor and a contact connecting the pixel electrode. The reflective electrode layer and the transparent electrode layer constituting the pixel electrode may be electrically connected to the drain electrode exposed through the contact window, respectively.

According to the present invention, an oxide film is formed at an interface between an aluminum-containing reflective metal layer and an indium metal oxide-based transparent electrode layer forming a pixel electrode in a reflective transparent thin film transistor liquid crystal display device, thereby increasing contact resistance, thereby increasing the potential for liquid crystal array in the reflective metal layer. Can solve the problem that is not correctly applied.

Reflective composite LCD. ITO, IZO, Aluminum, Contact

Description

TFT LCD of merged reflection-transmission type

Fig. 1 is a side cross-sectional view of each pixel of a TFT side substrate in one example of a reflection-transmission composite TFT LCD.

2 to 8 are side cross-sectional views illustrating a process of forming a thin film transistor according to an exemplary embodiment of the present invention.

9 and 10 are side cross-sectional views of a pixel portion showing a modified example of the process shown in Figs.

11 to 12 are side cross-sectional views of a pixel portion showing still another example of the process of forming the pixel electrode of the present invention.

Fig. 13 is a side sectional view of a pixel portion showing still another embodiment of the present invention.

FIG. 14 is a plan view of the embodiment of the present invention shown in FIG.

※ Explanation of symbols for main parts of drawing

1: pixel electrode 7: reflection area

9: transmission region 10: substrate

11: gate electrode 13: gate insulating film

14: ohmic contact layer 15: amorphous silicon layer

16: drain electrode 17: protective film

18: transparent electrode 19: separation insulating film

20: reflective electrode layer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflective transparent thin film transistor liquid crystal display device, and more particularly, to a reflective transparent composite thin film transistor liquid crystal display device in which a reflective film and a transmissive film constituting a pixel electrode can secure drain and contact of a thin film transistor. will be.

The importance of information display devices is very important in the development of the information society, and among the information display devices, LCD is the most rapidly developing field at present. In particular, TFT LCD, which uses thin film transistors to control the pixels, has the advantages of LCD, which is light weight, thin, and low power consumption, and is positioned as a high-quality information display device that can meet the demands of high resolution, fast operation speed, and colorization. It's widening.

Hereinafter, a process of forming a bottom gate amorphous silicon type TFT LCD in which a gate is first formed on a glass substrate and an active region of a transistor device is formed using amorphous silicon will be described.

According to the prior art, first, a single film or multiple films of aluminum or chromium are laminated on a glass substrate, and a gate electrode and a gate line are formed using photolithography and an etching process (1st mask). A gate pad is formed at the end of the gate line. Next, an amorphous silicon film for forming a gate insulating film, a channel and a source drain region is stacked over the gate pattern. Usually, an ohmic contact layer is formed on the amorphous silicon to lower the resistance in contact with the source drain electrode. The layer is doped with impurities such as phosphorous in the amorphous silicon to electrically connect the semiconductor layer with the electrode metal layer. Will increase your strength.

The pattern is continuously formed on the three-layer film thus formed by photolithography and etching using a photomask corresponding to the active region (2nd mask). Then, a metal layer for forming a source drain electrode is stacked thereon, and a source, a drain electrode, and a data line are formed through a mask technique (3rd mask).

In some cases, the three-layer film is laminated, and a metal layer for forming the source and drain electrodes is stacked before the pattern is formed, and then the top of the ohmic contact layer and the amorphous silicon layer is removed while patterning the source and drain electrodes to form a channel. In this case, the 2nd mask and the 3rd mask process may be replaced (the 4 mask process).

A protective film is stacked on the transistor basic electrode structure of the source, gate, and drain formed as described above. The protective film is a kind of insulating film, which is generally made of silicon oxide, but may be made thick of an organic film. After the protective film is laminated, the insulating film is removed over the gate pad or the data line pad and the source electrode to form a contact to prepare a connection with an external electrode or a pixel electrode. The process of partially removing the insulating layer also uses photolithography and an etching process (4th mask).

On this passivation layer, pixel electrodes are also formed by masking. In the case of a reflective liquid crystal display device, aluminum is mainly deposited by sputtering to form a large portion of the pixel through photolithography and etching processes. .

The pixel electrode of the backlight or transmissive LCD is formed of transparent indium tin oxide (ITO), indium zinc oxide (IZO), etc., as light passes through the pixel electrode and enters the eyes of the user (5th mask).

In addition to the basic five-sheet mask process, the manufacturing method of the liquid crystal display device may have various modifications depending on the structure of the transistor according to the number of process masks.

By the way, there is a distinction between the reflective LCD and the transmissive LCD as one of the classification for the LCD. Reflective type displays the image by reflecting external light with the reflecting plate on the inner surface of the panel. Transmissive type installs the backlight, which is an independent light source behind the panel, and adjusts the arrangement of the liquid crystal so that the light of the light source does not pass or pass through the panel. This is how you implement it. In the early liquid crystal display device, the reflection type was used a lot in the equipment which needs to minimize the power consumption such as a clock or a calculator, but the transmissive type is generally used in the notebook LCD which requires high quality image display, especially in the TFT LCD. to be.

According to the current trend, there are many reflection types that can achieve the highest quality image using external light while reducing power consumption even in a place requiring a high quality image on a large screen such as a notebook computer. In spite of the change in ambient light, the reflective transmissive LCD has been introduced through the LCD manufacturer Sharp Corporation.

Introduced reflection-transmission composite thin film transistor LCD is formed by sputtering pixel electrode pattern into transparent electrode layer when forming pixel electrode 1 on insulating film in electrode formation process of conventional TFT-side substrate. A metal film such as chromium, that is, a reflective film layer is formed again by a method such as sputtering, and then a desired reflective film pattern is formed by using a mask process, that is, photolithography and etching. By this method, the external area of the pixel electrode in which the pixel electrode of the reflective film layer or the transparent electrode layer is not left on the insulating film, the transparent area of which only the transparent electrode remains, and the reflective area 9 of the reflective film remaining on the transparent electrode are distinguished. Is formed. The transmission area is usually formed in the concept of a window and can be referred to as a transmission window. Fig. 1 is a side cross-sectional view of each pixel of a TFT side substrate in one example of a reflection-transmission composite TFT LCD.

However, a material problem may occur in the method of manufacturing the reflective transparent thin film transistor liquid crystal display device. In other words, ITO, which is used most frequently because of its relatively high conductivity as a transparent electrode, has excellent reflectivity and conductivity, and when it comes into contact with aluminum, which is used most often as a reflective pixel electrode, or when it encounters an aluminum-containing alloy such as aluminum and neodymium, It is easy to form an insulating oxide film on the surface of the aluminum reflective electrode plate, so that the voltage is not properly applied to the aluminum reflective electrode plate, so that the reflective liquid crystal display device can be a transmissive liquid crystal display device having a low aperture ratio. In addition, when the two conductive layers meet in series, there is a problem in that corrosion occurs due to a reaction like a chemical cell when contacted with an electrolyte material such as an etchant and a cleaning solution.

In order to eliminate this problem of using ITO as a transparent electrode, there is a method using an IZO transparent electrode. However, even in this case, although the degree is smaller than that of ITO, an insulating aluminum oxide film is formed between the aluminum-containing metal layer and the IZO, so that the contact resistance can be increased.

In order to solve this problem, there is a method of forming a separate contact to electrically connect the drain electrode to the reflective electrode and the transparent electrode of the reflective and transmissive regions. In this case, the reflective electrode and the transparent electrode may form a separate pattern without overlapping. However, since the pixel electrode is wide but the drain electrode is formed in a relatively limited region, the arrangement of the transparent region and the reflective region is difficult to optimize.

In the present invention, in the case of using an indium oxide-based transparent electrode layer and an aluminum-containing metal as the reflective electrode as a pixel electrode in a reflective transparent thin film transistor liquid crystal display device, the two metal layers are overlapped in a planar shape, and in a pattern formation process or a cleaning process. It is an object of the present invention to provide a reflective transparent thin film transistor liquid crystal display device capable of preventing a phenomenon in which an electric potential is not properly formed in a reflective film due to the formation of an insulating material at an interface without corrosion due to the action of a chemical battery.

The reflective transparent thin film transistor liquid crystal display according to the present invention includes a thin film transistor, a protective film, a transparent electrode layer, a separation insulating film and a reflective electrode layer. The passivation layer protects the thin film transistor and has a first contact hole exposing a drain electrode of the thin film transistor. The transparent electrode layer is provided on the passivation layer and is in direct contact with a first portion of the drain electrode exposed through the first contact hole. A second insulating insulating layer disposed on the transparent electrode layer to cover the transparent electrode layer and having a width smaller than that of the first contact hole at a position where the first contact hole is formed to expose a second portion of the drain electrode; Contact holes are formed. The reflective electrode layer is provided on the isolation insulating layer, and directly contacts the second portion of the drain electrode exposed through the second contact hole, and has a light transmitting layer.
In addition, the reflective transparent thin film transistor liquid crystal display according to the present invention includes a thin film transistor, a protective film, a reflective electrode layer and a transparent electrode layer. The protective layer protects the thin film transistor and has a contact hole exposing a drain electrode of the thin film transistor. The reflective electrode layer is provided on the passivation layer and directly contacts the first portion of the drain electrode through the contact hole. Here, an opening is formed in the reflective electrode layer to have a width smaller than that of the contact hole to expose the second portion of the drain electrode, and a transparent window is formed in a predetermined region of the reflective electrode layer to expose the protective film. The transmissive electrode layer is provided on the reflective electrode layer, the second portion of the drain electrode exposed through the opening, and the passivation layer exposed by the light transmission window.
The reflective transparent thin film transistor liquid crystal display device according to the present invention includes a thin film transistor, a protective film, a transparent electrode layer, a separation insulating film and a reflective electrode layer. The passivation layer protects the thin film transistor, and first and second contact holes are formed to expose first and second portions of the drain electrode of the thin film transistor, respectively. The transparent electrode layer is in direct contact with the first portion of the drain electrode of the thin film transistor through the first contact hole. The isolation insulating layer is formed on the transparent electrode layer, and a third contact hole exposing the drain electrode is formed corresponding to a position where the second contact hole is formed. The reflective electrode layer is provided on the isolation insulating layer, and directly contacts the second portion of the drain electrode exposed through the second and third contact holes, and has a light transmitting layer.
The reflective transparent thin film transistor liquid crystal display according to the present invention includes a gate pattern, a channel, a source and a drain electrode, a data line, a protective film, a transparent electrode layer, a separation insulating layer, and a reflective electrode layer. The gate pattern is stacked on a substrate and the substrate, and the channel includes an active pattern and an amorphous silicon layer formed by sequentially stacking a gate insulating layer, an amorphous silicon layer, and an ohmic contact layer on the gate pattern. The source and drain electrodes are formed over the active pattern, and the data line is connected to the source electrode. The passivation layer is formed on the data line, and a first contact hole exposing the drain electrode is formed. The transparent electrode layer is in direct contact with a first portion of the drain electrode exposed through the first contact hole. The isolation insulating layer is formed on the transparent electrode layer to cover the transparent electrode layer, and the separation insulating layer is formed to have a width smaller than the first contact hole at a position where the first contact hole is formed to form a second portion of the drain electrode. A second contact hole for exposing is formed. The reflective electrode layer is provided on the isolation insulating layer, and directly contacts the second portion of the drain electrode exposed through the second contact hole, and has a light transmitting layer.

Indium oxide-based transparent electrode in the present invention may be Indium Tin Oxide (ITO) and IZO (Indium Zinc Oxide) which has been studied a lot of recent replacement. The thickness of the aluminum-containing reflective electrode layer and the transparent electrode layer constituting the pixel electrode is relatively small compared to the width of the drain electrode exposed through the contact window, so that the contact is made to the insulating film when patterning the first layer of the two electrode layers constituting the pixel electrode. As a window is formed, a part of the first stacked film is removed in the contact region to form a window, and the remaining electrode layers are stacked on top of each other, and then formed in a required pattern, thereby patterning each layer constituting the pixel electrode without additional exposure and etching processes. A drain and pixel electrode connection structure is formed.

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The stacking order of the reflective electrode layer and the transparent electrode layer constituting the pixel electrode in the reflective transparent thin film transistor liquid crystal display device is preferable to form the transparent electrode layer below and the reflective electrode layer above, in consideration of the reflection efficiency. It doesn't matter. However, in the case of IZO, there is no difference in etching selectivity between aluminum and commonly used etchant. Therefore, it is difficult to form IZO generally in the pixel portion and to form an aluminum reflective metal pattern thereon by etching. The region in which the reflective electrode layer and the transparent electrode layer are formed in the pixel portion region may be formed the same even if the order is changed.

In the present invention, in order to prevent corrosion caused by chemical action during cleaning or patterning etching coming from the direct contact between the ITO transparent electrode layer and the aluminum-containing reflective electrode layer, a thin and fine silicon nitride film or silicon oxide film is formed as a separation insulating film between the two electrode layers. You can also take a method. In this case, the window is formed again in the contact layer region as the window is formed again in the lower electrode layer constituting the pixel electrode in the contact window region so that the upper electrode layer constituting the pixel electrode is directly connected to the drain electrode. In particular, the lower electrode layer and the isolation insulating layer may be sequentially stacked, and a single patterning operation may simultaneously produce a window in the contact window region, and in some cases, a light transmitting window may be patterned together. In addition, since the existence of the isolation insulating film has a negative effect on the efficiency of light during reflection and transmission, it is preferable that the isolation insulating film be removed in a region where the two electrodes of the pixel portion do not overlap. In order to remove the separation insulating film without a separate exposure process, the reflective electrode layer needs to be formed upward to serve as a mask for etching the separation insulating film.

According to an embodiment of the present invention, a region is divided in one contact window, and a portion of the drain electrode exposed to the transparent electrode and the contact window is connected, and in addition, the drain electrode and the reflective electrode layer meet each other, and a plurality of contact windows are formed on the drain electrode. One or more of them may be considered a form in which the drain electrode and the transparent electrode meet each other in the remaining at least one contact window.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

2 to 8 are side cross-sectional views illustrating a process of forming a thin film transistor according to an exemplary embodiment of the present invention. The thin film transistor according to the present embodiment has a gate electrode 11, a gate insulating film 13, an amorphous silicon film 15 and an ohmic contact layer 14 to form an active layer on the substrate 10 in the same order as the conventional five-sheet process. A source and drain electrode 16 is formed. As shown in FIG. 4, the drain electrode 16 is formed relatively wide out of the active region, and as shown in FIG. 5, an insulating protective film 17 is formed on the drain electrode 16. Next, a contact window for connection with the pixel electrode is formed.

In order to form a pixel electrode, an ITO transparent electrode 18 is stacked and patterned on the entire pixel electrode region as shown in FIG. 6. In the patterning process, the window is formed in a portion of the contact window again, and the drain electrode 16 is exposed. A separation insulating film 19 made of a silicon nitride film is formed thereon as shown in FIG. In the isolation insulating film 19, a window is formed in an area where the drain electrode 16 is exposed in FIG. 6, like the ITO layer. Therefore, as shown in FIG. 8, when the reflective electrode layer 20 made of aluminum is stacked, the drain electrode 16 and the reflective electrode layer 20 are electrically connected to each other through the window formed in FIG. 7. When patterning the reflective electrode layer, a light transmission window for transmitting light is formed. 8 shows an example of the TFT glass of the liquid crystal display of the present invention.

9 to 10 are examples of another process of forming the pixel electrode of the present invention. Here, as illustrated in FIG. 9, the reflective electrode layer 20 is first formed. The pixel electrode is completed by laminating and patterning the IZO transparent electrode 18 as shown in FIG. When the reflective electrode layer is formed, a window is formed in a part of the contact window region during patterning to naturally form a separate contact from the drain electrode when the transparent electrode layer is stacked. Since the IZO material has less side effects at the interface in contact with the aluminum containing layer than the electrode of ITO material, the IZO material may be formed although a separate insulating film is not formed. In FIG. 9, it can be seen that a light transmission window is formed in the patterning of the reflective electrode layer. If the IZO transparent electrode layer is first formed in reverse order and the aluminum-containing reflective electrode layer is laminated and patterned to form the light transmission window, the selection ratio of the two electrode layers to the etchant is not large, so the IZO layer in the light transmission window region may be removed together. Not.

Figures 11 and 12 show variations on the process shown in Figures 2-8. Here, the process of forming the ITO transparent electrode 18 and the isolation insulating film 19 made of silicon nitride film shown in FIGS. 6 and 7 is performed using one exposure mask. Formation of the reflective electrode layer 20 of FIG. 12 is performed as in the example of FIG. In the step of forming the light transmission window, the silicon nitride film of the light transmission window region is also continuously removed by etching, thereby improving light transmittance.

Fig. 13 is a side sectional view showing still another example of the present invention. The drain electrode 16 extends out of the amorphous silicon film 15 forming the active region, and two contact holes are formed in the passivation layer 17 over the drain electrode 16. In the process of forming the pixel electrode, first, the ITO transparent electrode 18 layer is stacked and patterned so as to be connected to the drain electrode 16 in one contact and not in another contact. Next, the isolation insulating film 19 such as a silicon nitride film is laminated and patterned to surround the ITO transparent electrode 18, but contact holes that are not connected to the ITO transparent electrode 18 are not wrapped with the insulating film. Next, the reflective electrode layer 20, such as aluminum, is stacked and patterned to form a transmission window at a portion overlapping with the transparent electrode 18. In this example, the transparent electrode 18 and the reflective electrode layer 20, which form the pixel electrode, are separated by an insulating film, and contact with the drain electrode through the contact hole, respectively.

14 is a plan view of an embodiment of the present invention as shown in FIG. Two contacts are formed on the drain electrode side by side and are connected to the transparent electrode layer and the reflective electrode layer pixel electrode, respectively, and two transparent light emitting windows are formed in the reflective electrode area to expose the transparent electrode layer.

According to the present invention, an oxide film is formed at an interface between an aluminum-containing reflective metal layer and an indium metal oxide-based transparent electrode layer forming a pixel electrode in a reflective transparent thin film transistor liquid crystal display device, thereby increasing contact resistance, thereby increasing the potential for liquid crystal array in the reflective metal layer. Can solve the problem that is not correctly applied.

Claims (13)

Thin film transistors; A passivation layer protecting the thin film transistor and having a first contact hole exposing a drain electrode of the thin film transistor; A transparent electrode layer provided on the passivation layer and directly contacting a first portion of the drain electrode exposed through the first contact hole; A second contact hole formed on the transparent electrode layer to cover the transparent electrode layer, the second contact hole being formed to have a width smaller than the first contact hole at the position where the first contact hole is formed to expose the second portion of the drain electrode; Separation insulating film; And And a reflective electrode layer disposed on the isolation insulating layer and directly contacting the second portion of the drain electrode exposed through the second contact hole, the reflective electrode layer having a light transmitting layer. Display. The method of claim 1, The transparent electrode layer is a transparent transparent composite thin film transistor, characterized in that made of ITO. The method of claim 1, In the region where the first contact hole is formed, an opening is formed in the transparent electrode layer to expose the drain electrode. And the opening is formed to have a width greater than or equal to that of the second contact hole. The method of claim 3, wherein An end portion of the transparent electrode layer defining the opening is covered by the isolation insulating layer so that the reflective electrode layer is not in direct contact with the reflective electrode layer. The method of claim 1, The reflective electrode thin film transistor liquid crystal display device, characterized in that the reflective electrode layer is made of an aluminum alloy. The method of claim 1, And the isolation insulating layer is formed of a silicon nitride film material. Thin film transistors; A passivation layer protecting the thin film transistor and having a contact hole exposing a drain electrode of the thin film transistor; An opening provided on the passivation layer and directly contacting the first portion of the drain electrode through the contact hole, the opening having a width smaller than that of the contact hole to expose the second portion of the drain electrode; A reflective electrode layer having a light transmission window exposing the passivation layer in a region; And And a transmissive electrode layer formed on the reflective electrode layer, the second portion of the drain electrode exposed through the opening, and a passivation layer exposed by the light transmission window. The method of claim 7, wherein The transmission electrode layer is made of IZO material, The reflective electrode layer is a reflective transparent thin film transistor, characterized in that the aluminum electrode is made of aluminum alloy. Thin film transistors; A passivation layer protecting the thin film transistor and having first and second contact holes respectively exposing first and second portions of a drain electrode of the thin film transistor; A transparent electrode layer directly contacting the first portion of the drain electrode of the thin film transistor through the first contact hole; A separation insulating layer formed on the transparent electrode layer and having a third contact hole exposing the drain electrode corresponding to a position where the second contact hole is formed; And And a reflective electrode layer provided on the isolation insulating layer and directly contacting the second portion of the drain electrode exposed through the second and third contact holes and having a light transmitting layer. Thin film transistor liquid crystal display device. 10. The liquid crystal display of claim 9, wherein the transparent electrode layer is partially removed from the region where the second and third contact holes are formed so that an opening is formed in the transparent electrode layer. The method of claim 10, The opening is formed in the transparent electrode layer having a width larger than the second and third contact hole, the reflective transparent thin film transistor liquid crystal display device. The method of claim 10, An end portion of the transparent electrode layer defining the opening is covered by the isolation insulating layer so that the reflective electrode layer is not in direct contact with the reflective electrode layer. A substrate and a gate pattern stacked on the substrate; A channel including an active pattern formed by sequentially stacking a gate insulating film, an amorphous silicon film, and an ohmic contact layer on the gate pattern; Source and drain electrodes formed over the active pattern; A data line connected to the source electrode; A passivation layer formed over the data line and having a first contact hole exposing the drain electrode; A transparent electrode layer in direct contact with a first portion of the drain electrode exposed through the first contact hole; A second contact hole formed on the transparent electrode layer to cover the transparent electrode layer, the second contact hole being formed to have a width smaller than the first contact hole at the position where the first contact hole is formed to expose the second portion of the drain electrode; Separation insulating film; And And a reflective electrode layer disposed on the isolation insulating layer and directly contacting the second portion of the drain electrode exposed through the second contact hole, the reflective electrode layer having a light transmitting layer. Display.

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