KR20010054411A - Semi-transmitiv reflection type tft-lcd sevice - Google Patents

Abstract

PURPOSE: A semi-transflective TFT-LCD is provided to prevent a corrosion on an interface between a transparent electrode and a reflective plate by preventing that an interface of a reflection electrode is contacted with an interface of a transparent electrode. CONSTITUTION: A reflection electrode(20) is formed between a liquid crystal layer and a first substrate, and functions as a pixel electrode of the reflection mode. A transmission window is formed on the reflection electrode(20), and functions as a light transmission area of the transmission mode. TFT includes a gate electrode(4), a gate insulating layer(6), a semiconductor layer(8) and a source/drain electrode(10,12), and functions as a switching element of LCD. On the gate insulating layer(6), a transparent electrode is formed on the same layer as the source/drain electrode(10,12), one end of the transparent electrode is overlapped with one end of the drain electrode(12). An insulating layer(18) covers the TFT and the transparent electrode, and has a contact hole allowing the reflection electrode to be connected to the drain electrode.

Description

Transflective Thin Film Transistor Liquid Crystal Display {SEMI-TRANSMITIV REFLECTION TYPE TFT-LCD SEVICE}

The present invention relates to a thin film transistor-liquid crystal display device (TFT-LCD) for implementing a display by transmitting and reflecting incident light.

Among the liquid crystal display devices, in particular, the reflective liquid crystal display device which reflects incident light to be displayed is attracting much attention because not only a backlight is required, but also its design can be thin and its weight can be reduced. And a semi-transmissive reflection type liquid crystal display device capable of reflecting and displaying an image is attracting more attention.

In such a transflective liquid crystal display, transparent electrodes such as indium tin oxide (ITO) and indium zinc oxide (IZO) and reflector plates such as aluminum (Al) are simultaneously formed in the same pixel to connect each other continuously. do. In this structure, since the transparent electrode and the aluminum of the reflecting plate are in continuous contact with each other, the transparent electrode and the reflecting plate react with each other by an electrolyte material such as a metal etchant and cleaning liquid used in the subsequent etching / cleaning process. Corrosive, aka battery effect. This corrosion leads to the formation of an insulating material at the interface between the transparent electrode and the reflecting plate, which in turn causes a problem that the contact resistance at that interface becomes large.

Accordingly, an object of the present invention is to provide a semi-transmissive reflective TFT-LCD device for preventing corrosion from occurring at an interface between a transparent electrode and a reflecting plate.

Another object of the present invention is to provide a semi-transmissive reflective TFT-LCD device which simplifies the manufacturing process by the structure in which a transparent electrode layer is formed on the same layer as the source / drain electrode layer.

1A to 1F are cross-sectional views showing processes for manufacturing a lower substrate (active matrix substrate) of a semi-transmissive reflective TFT-LCD device according to an embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

2: transparent insulation board

4: gate electrode

6: gate insulating film

8: semiconductor layer

10: source electrode

12: drain electrode

14: thin film transistor (TFT)

16: transparent electrode

18: insulating film

19: contact hall

20: reflective electrode

22: transmission window

A transflective thin film transistor liquid crystal display device according to the present invention includes a first substrate functioning as an active matrix substrate, a second substrate facing the first substrate, and a liquid crystal layer sandwiched between these substrates, wherein Images can be displayed in modes and transmission modes. The liquid crystal display device has a reflective electrode formed between the liquid crystal layer and the first substrate and serving as a pixel electrode of the reflective mode, and formed on the reflective electrode and having light transmission in the transmissive mode. At least one transmission window serving as an area, a gate electrode formed on the first substrate, a gate insulating layer, a semiconductor layer serving as a channel, and a source / drain electrode, and serving as a switching element of the liquid crystal display device. A thin film transistor and a transparent electrode formed on the same layer as the source / drain electrode on the gate insulating layer 6, one end of which is overlapped with one end of the drain electrode, and the thin film transistor and the transparent electrode; An insulating film having a contact hole for causing the reflective electrode to be electrically connected to a portion of the drain electrode; The. With this structure, since the transparent electrode is formed on the same layer as the source / drain electrode layer, the contact hole can be formed in a single step, and the manufacturing process can be simplified. In addition, since the reflective electrode and the transparent electrode are isolated from each other by the insulating film, their interfaces can be prevented from being corroded by the electrolytic materials used in subsequent etching or cleaning processes.

(Example)

Next, the structure of the transflective TFT-LCD device and the manufacturing method thereof according to the preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

The transflective TFT-LCD device according to the present invention comprises a lower substrate (active matrix substrate), an upper substrate (counter substrate) and a liquid crystal layer sandwiched therebetween.

1A to 1F are cross-sectional views showing processes for manufacturing a lower substrate (active matrix substrate) of a semi-transmissive reflective TFT-LCD device according to an embodiment of the present invention.

Referring to Fig. 1A, reference numeral 2 denotes an active matrix substrate which is a lower substrate of a completed TFT-LCD, that is, a transparent insulating substrate such as glass, and reference numeral 4 denotes a gate electrode formed on this substrate 2. The gate electrode 4 is made of a metal film having low resistivity, such as chromium (Cr), aluminum (Al), a double film of chromium and aluminum, and tantalum (Ta). The gate electrode 4 is actually applied to a photo / etch process using a gate forming mask (not shown) after the above-described metal film is actually applied onto the entire substrate of the transparent insulating substrate 2 by sputtering or the like. It is formed by patterning. In this embodiment, the gate electrode 4 is formed to a thickness of 1500 kPa to 3000 kPa (preferably about 2000 kPa).

Next, as shown in FIG. 1B, a silicon nitride film or a silicon oxide film to function as the gate insulating film 6 is formed on the entire substrate of the transparent insulating substrate 2 to a thickness of about 2000 μs by a plasma enhanced CVD method or the like. Is formed on the phase. Next, an amorphous silicon film (a-Si) having a thickness of 2000 kPa to 3000 kPa, and a high concentration n ⁺ amorphous silicon film 8b having a thickness of 700 kPa to 1000 kPa doped with impurities as an ohmic contact layer were obtained. It is sequentially formed on the gate insulating film 6 by the above-described CVD method, and then patterned by a photo / etch process to form a semiconductor layer 8 at a position on the gate electrode 4. The semiconductor layer 8 may also be formed of poly-crystalline silicon (p-Si) or cadmium selenide (CdSe) film.

After the formation of the semiconductor layer 8, brush-cleaning may be performed to remove adhesive dust and the like from the surface of the transparent insulating substrate 2. Subsequently, as illustrated in FIG. 1C, conductive films such as chromium (Cr), APC, titanium (Ti), molybdenum (Mo), and aluminum (Al) films are formed on the entire substrate of the transparent semiconductor substrate 2 by sputtering or the like. Next, the conductive film is patterned by a photo / etch process using a source / drain forming mask to form the source / drain electrodes 10 and 12. This source / drain electrode may also be formed of the same material as that of the transparent conductive film formed by a subsequent process. Although the high concentration n ⁺ amorphous silicon film 8b is not etched in the drawing, as another example, the high concentration n ⁺ amorphous silicon film 8b of the semiconductor layer 8 in the patterning process of the source / drain electrodes. It may also be patterned to expose some surfaces of the amorphous silicon layer 8a. The thin film transistor TFT 14 includes a gate electrode 4, a gate insulating film 6, a semiconductor layer 8, a source electrode 10, and a drain electrode 12. This TFT 14 functions as a switching element of the liquid crystal display device as is well known.

Next, as shown in FIG. 1D, a transparent electrode 16 such as an ITO film or an IZO film is formed on the gate insulating film 6, and one end of the transparent electrode 16 is formed of the drain electrode 12. They overlap each other and are electrically connected to each other. Here, one of two important features of the present invention is that the transparent electrode 16 is formed on the same layer where the source / drain electrodes 10 and 12 are formed. This feature makes it possible to form a contact hole in a single contact hole forming step, thereby simplifying the process.

In another embodiment, the transparent electrode may be formed first before the source / drain electrode is formed. Also in this case, the source / drain electrodes and the transparent electrode are similarly formed in the same layer, and one end is electrically connected to each other.

Subsequently, as shown in FIG. 1E, the entire surface of the insulating substrate 2 is transparent with an insulating film 18 such as an organic insulating layer, a silicon nitride film, and a combination thereof to warm the TFT 14. It is formed and patterned on the phase. As a result, the insulating film 18 has the contact hole 19 in a portion on the drain electrode 12.

Finally, as shown in Fig. 1F, a reflective electrode 20 made of aluminum (Al), APC, or AlNd or the like is formed on the insulating film 18 including the contact hole 19, and this reflection The electrode 20 is in electrical contact with the drain electrode 12 through the contact hole 19. Subsequently, the reflective electrode 20 is patterned by a photo / etching process using a mask for forming a transmission window, thereby forming a transmission window 22. Although one transmission window is shown in the drawings, it will be apparent to one skilled in the art that at least two transmission windows may be formed in the present invention. The reflective electrode 20 functions as a pixel electrode in the reflection mode. Here, it is another feature of the present invention that the aluminum of the reflective electrode 20 is isolated from the ITO of the transparent electrode 16 by the insulating film 18.

As another example of forming the transmission window 22, as shown in FIG. 2, during the etching process of the reflective electrode 20, the insulating layer of the light transmission region in which the transmission window 22 is formed. All of 18 can be eliminated so that the cell gap in the light transmission region is made larger than the cell gap in the reflection region. In this case, the intensity of the transmitted light in the light transmissive region is increased, so that the overall brightness of the TFT-LCD can be increased. Here, the cell gap refers to a thickness of the liquid crystal layer formed by injecting liquid crystal between upper and lower substrates.

In addition, as shown in FIG. 3, even when the insulating film 18 in the light transmission region where the transmission window 22 is formed is partially removed during the etching process of the reflective electrode 20. The same effect can be expected as when the insulating film 18 is completely removed. However, in this case, as shown in FIG. 3, a process for forming a film 24 of insulating material on the transparent electrode 16 is further required. The lower substrate is manufactured in the same manner as in the above-described embodiment except that the transparent electrode 16 and the insulating film 24 are sequentially formed and then patterned by a photo / etch process. The formation of the insulating film 24 is provided to prevent an oxide film from being formed on the transparent electrode 16 during the etching process of the insulating film 18.

In this way, the reflective electrode 20 and the transparent electrode 16 are separated from each other by the insulating film 18 so that their interfaces can be prevented from being corroded by the electrolytic materials used in subsequent etching or cleaning processes.

According to the present invention described above, the reflective electrode and the transparent electrode are prevented from directly contacting their interfaces by the insulating film, thereby preventing corrosion at the interface.

In addition, according to the present invention, the transparent electrode is formed on the same layer as the source / drain electrode layer, so that the contact hole can be formed in a single step, thereby simplifying the manufacturing process of the liquid crystal display device.

Claims (5)

A semi-transmissive reflective type comprising a first substrate functioning as an active matrix substrate, a second substrate facing the first substrate, and a liquid crystal layer sandwiched between these substrates, and capable of displaying an image in reflection mode and transmission mode. In a thin film transistor liquid crystal display device, A reflection electrode 20 formed between the liquid crystal layer and the first substrate and serving as a pixel electrode in the reflection mode; At least one transmission window formed on the reflective electrode 20 and functioning as a light transmission region in the transmission mode; A gate electrode 4 formed on the first substrate, a gate insulating layer 6, a semiconductor layer 8 functioning as a channel, and source / drain electrodes 10 and 12; A thin film transistor functioning as an element; A transparent electrode formed on the gate insulating layer 6 in the same layer as the source / drain electrodes 10 and 12, and one end of which overlaps one end of the drain electrode 12; And an insulating film (18) covering the thin film transistor and the transparent electrode and having a contact hole to electrically connect the reflective electrode to the drain electrode. The method of claim 1, The insulating film 18 is a transflective thin film transistor liquid crystal display selected from the group consisting of an organic insulating film, a silicon nitride film, and a combination thereof. The method of claim 1, The semiconductor layer 18 is a semi-transmissive reflective thin film transistor liquid crystal display selected from the group consisting of amorphous silicon, polysilicon, cadmium selenide (CdSe) film. The method of claim 1, A transflective thin film transistor liquid crystal display further comprising a film coated with an insulating material on the transparent electrode. The method of claim 1, And at least a portion of the insulating film in the light transmissive region so that a cell gap in the light transmissive region is larger than a cell gap in the reflective region.