KR20020076934A - Apparatus for thin film transistor liquid crystal display and method for manufacturing the same - Google Patents

Abstract

PURPOSE: A thin film transistor liquid crystal display and a method for manufacturing the same are provided to increase operating current and decrease leakage current by controlling the thickness of first and second silicon films of an active layer, thereby obtaining the optimum characteristics of a thin film transistor. CONSTITUTION: A method for manufacturing a thin film transistor liquid crystal display includes the steps of forming a gate electrode(13a) on a transparent insulating board(11), forming a gate insulating film(15) and an active layer(17) formed of a double film of first and second silicon films(17a,17b) having different resistance, forming source and drain electrodes(21a,21b) by evaporating a metal film for source and drain electrodes and patterning the metal film thereafter, forming a protective film(23) on the transparent insulating board in which the source and drain electrodes are formed and forming a via hole disclosing a predetermined part of the source electrode, and forming a pixel electrode(25) on the protective film to be contacted with the disclosed source electrode.

Description

Thin film transistor liquid crystal display and its manufacturing method {Apparatus for thin film transistor liquid crystal display and method for manufacturing the same}

The present invention relates to a thin film transistor liquid crystal display device and a method of manufacturing the same. More particularly, the active layer for the channel is formed as a double layer to increase the operating current (I _on ) and lower the leakage current (I _off ) to improve the thin film transistor characteristics. A thin film transistor liquid crystal display device and a manufacturing method thereof are provided.

In general, in a liquid crystal display device, an active matrix liquid crystal display device has high-speed response and has a large number of pixels. As a result, the display screen has high quality, large size, color screen, and the like, and is used in portable televisions, notebook computers, automobile navigation systems, and the like.

In such an active matrix liquid crystal display device, a switching element such as a thin film transistor is disposed at a portion where a gate line and a data line cross each other to selectively turn on / off a pixel electrode.

In this regard, a conventional thin film transistor liquid crystal display and a manufacturing method thereof will be described with reference to FIGS. 1A to 1E.

In a conventional thin film transistor and a method of manufacturing the same, first, as shown in FIG. 1A, a metal layer for gate electrode wiring is deposited on a transparent insulating substrate, for example, a glass substrate 1, to a predetermined thickness. Then, a portion of the metal layer is patterned through the first mask process to form the gate electrode 3a and the common electrode 3a.

Subsequently, as shown in FIG. 1B, the gate insulating film 5 is deposited to a predetermined thickness on the glass substrate 1 on which the gate electrode 3a and the common electrode 3a are formed, and then serve as a channel of the thin film transistor. The amorphous active layer 7 and the doped amorphous silicon layer 9 are sequentially deposited. Thereafter, in the second mask process, the amorphous active layer 7 and the doped amorphous silicon layer 9 are patterned to exist in the thin film transistor predetermined region.

Next, as shown in FIG. 1C, a metal film for source / drain electrodes is deposited on the glass substrate 1 on which the gate insulating film 5, the amorphous active layer 7, and the doped amorphous silicon layer 9 are formed. Thereafter, the metal film is patterned by a third mask process so that the metal film exists on both sides of the amorphous active layer 7 to form a source electrode 11a and a drain electrode 11a. At this time, during the patterning process of the source electrode 11a and the drain electrode 11a, the doped amorphous silicon layer 9 is also patterned.

Thereafter, as shown in FIG. 1D, the passivation layer 13 is formed on the glass substrate 1 on which the source electrode 11a and the drain electrode 11a are formed, for example, using silicon nitride. Thereafter, the passivation layer 13 is etched by a fourth mask process so that a portion of the source electrode 11a is exposed to form a via hole 14.

Subsequently, as illustrated in FIG. 1E, an indium tin oxide (ITO) film is deposited on the passivation layer 13 to contact the source electrode 11b exposed through the via hole h, and then a fifth mask process is performed. A predetermined portion of the ITO film is etched to form the pixel electrode 15 to complete the lower array substrate of the thin film transistor liquid crystal display including the thin film transistor.

In the lower array substrate of the thin film transistor liquid crystal display including the thin film transistor, the channel layer through which the current flows, that is, the amorphous active layer 7, determines the characteristics of the thin film transistor liquid crystal display.

Here, the operating current I _{on of the} current flowing through the channel layer determines the amount of charge to the pixel electrode, and the leakage current I _off is closely related to the screen quality, so that the operating current I _on and the leakage current ( the ratio I _on / I _off of I _off) the greater is excellent in contrast ratio (contrast ratio) and the brightness of the screen.

In the conventional thin film transistor liquid crystal display device and its manufacturing method, since the film is amorphous active layer is a single layer once the amorphous active layer is formed, and the operating current (I _on) and the ratio I _on / I _off an amorphous active layer of a leakage current (I _off) It is determined by the physical properties of.

Therefore, the operating current (I _on) and leakage current (I _off) ratio I _on / I _off at the same time, the operating current (I _on) and leakage current (I _off) since it affects the amorphous active properties of the individually controllable There was a problem that can not be done.

Accordingly, the present invention has been made to solve the problems of the prior art, the object of the present invention is to improve the I _on / I _off greatly by increasing the operating current (I _on ) and reducing the leakage current (I _off ) The present invention provides a thin film transistor liquid crystal display device and a method of manufacturing the same, which can obtain thin film transistor characteristics.

1A to 1E are cross-sectional views of respective processes for explaining a thin film transistor liquid crystal display device and a method of manufacturing the same according to the prior art.

2A through 2E are cross-sectional views of respective processes for explaining a thin film transistor liquid crystal display device and a method of manufacturing the same according to the present invention.

<Description of the symbols for the main parts of the drawings>

11; Transparent insulating substrate 13a; Gate electrode

13b; Common electrode 15; Gate insulating film

17; Active layer 17a; First silicon film

17b; Second silicon film 19; Doped amorphous silicon layer

21a; Source electrode 21b; Drain electrode

23; Protective film 25; Pixel electrode

According to an aspect of the present invention, there is provided a thin film transistor liquid crystal display device and a method of manufacturing the same; forming a gate electrode on a transparent insulating substrate; Forming an active layer including a gate insulating layer and a double layer of a first silicon layer and a second silicon layer having different resistances on the transparent insulating substrate on which the gate electrode is formed; Depositing a metal film for a source electrode and a drain electrode on the resultant of the transparent insulating substrate, and then patterning the metal film to form a source electrode and a drain electrode; Forming a protective film on an entire surface of the transparent insulating substrate on which the source electrode and the drain electrode are formed, and then forming a via hole exposing a portion of the source electrode; And forming a pixel electrode in contact with the source electrode exposed through the via hole on the passivation layer.

Hereinafter, a thin film transistor liquid crystal display and a method of manufacturing the same according to the present invention will be described in detail with reference to the accompanying drawings.

2A to 2E are cross-sectional views of respective processes for explaining a thin film transistor liquid crystal display device and a method of manufacturing the same according to the present invention.

In the thin film transistor liquid crystal display device and a method of manufacturing the same according to the present invention, first, as shown in FIG. 2A, a transparent insulating substrate 11, for example, a gate electrode using a metal having excellent electrical conductivity on a glass substrate. A metal layer is deposited to a certain thickness. Then, the metal layer is patterned into a desired shape through a first mask process to form a gate electrode 13a and a common electrode 13b.

Thereafter, as shown in FIG. 2B, the gate insulating layer 15 is deposited to a predetermined thickness on the entire surface of the transparent insulating substrate 11 on which the gate electrode 13a and the common electrode 13b are formed, and then a channel of the thin film transistor. The active layer 17 serving as a role and the doped amorphous silicon layer 19 serving as an ohmic layer are sequentially deposited.

Subsequently, the active layer 17 and the doped amorphous silicon layer 19 are patterned to a desired shape in a second mask process to form a thin film transistor predetermined region including a back channel. At this time, the active layer 17 serving as a channel of the thin film transistor is composed of a first silicon film 17a, which is a crystalline structure on the gate insulating film 15 side, and a second silicon film 17b, which is an amorphous structure on the back channel side. It is formed into a double membrane structure. The double layer structure is formed as follows.

First, a first silicon layer 17a having a crystalline structure is formed on the gate insulating layer 15. In this case, a regular crystalline structure, rather than an amorphous structure, is advantageous for the deposition material source to have high mobility at the substrate surface. Therefore, the deposition rate is lowered to achieve a crystal structure when the deposition material source is deposited.

Here, as the deposition rate increases, the deposition layer formed accordingly becomes an amorphous structure. On the contrary, as the deposition rate decreases, the deposition layer formed accordingly becomes a crystalline structure. Meanwhile, the deposition rate at which the lower low resistance layer 17a can form a crystalline structure, particularly a microcrystalline structure, is several hundreds kPa or less, preferably several tens of kPa or less, and more preferably 10 kPa or less.

Next, a second silicon film 17b having an amorphous structure is formed on the first silicon film 17a, that is, in the bulk region of the back channel part. The second silicon film 17b is formed by adding a small amount of material as an impurity, and the material added as the impurity should have a property of increasing electrical resistance and not crystallizing the second silicon film 17b. . Such materials include inert gases, oxygen, or nitrogen, which are Group 0 gases on the chemical periodic table including helium or neon. On the other hand, in the above material, at least about 1 weight percent must be added when forming the second silicon film 17b to obtain the effect according to the present invention.

Here, the thickness ratio between the first silicon film 17a and the second silicon film 17b is preferably 2 to 8. Since the channel layer corresponds to a thickness of 100 to 200 μs, the first film 17a is formed to have a thickness of 100 to 200 μs. In addition, the thickness of the second silicon film (17b) is from 800 to 2,000Å thick, that is, reducing the leakage current (I _off) is related to the size of the second silicon film (17b) has a leakage current (I _off) of a thickness In order to achieve this, the thickness of the entire active layer 17 is preferably composed of the second silicon film 17b except for the thickness of 100 to 200 mm 3 of the first silicon film 17a.

Here, the smaller the thickness of the first silicon film 17a increases the effect of the present invention, but if the thickness is less than 100 mA, the magnitude of the operating current I _ON decreases. The thickness should be at least 100 mm.

By the above process, the active layer 17 has a relatively low electrical resistance characteristic and has a relatively high electrical resistance characteristic with the first silicon film 17a of the crystalline structure, preferably the microcrystalline structure, and the impurities. It is formed in a double film structure composed of the added second silicon film 17b having an amorphous structure.

Subsequently, as shown in FIG. 2C, after depositing a metal film for the source electrode and the drain electrode with a predetermined thickness on the resultant of the transparent insulating substrate 11, a third mask is disposed on both sides of the active layer 17. Patterning is performed in a step to form the source electrode 21a and the drain electrode 21b. In this case, the exposed doped amorphous silicon layer 19 is patterned using the source electrode 21a and the drain electrode 21b as a mask to partially expose the active layer 17.

Thereafter, as shown in FIG. 2D, a protective film 23 is formed of, for example, a silicon nitride film on the entire surface of the transparent insulating substrate 11 on which the source electrode 21a and the drain electrode 21b are formed. Thereafter, the passivation layer 23 is etched by a fourth mask process so that a portion of the source electrode 21a is exposed to form a via hole 24.

Subsequently, as illustrated in FIG. 2E, a transparent conductor, for example, an ITO film, is deposited on the passivation layer 23 so as to contact the source electrode 21a exposed through the via hole h. Subsequently, when the pixel electrode 25 is formed by etching a portion of the ITO film through a fifth mask process, the lower array substrate of the thin film transistor liquid crystal display is completed.

Hereinafter, in the thin film transistor liquid crystal display device and a method of manufacturing the same, the operation of increasing the operating current I _ON and lowering the leakage current I _OFF is as follows.

The operating current (I _ON ) when a positive voltage is applied to the gate electrode tends to flow along the interface between the channel layer and the gate insulating film in the channel layer region, and conversely, when a negative voltage is applied to the gate electrode. The leakage current I _OFF tends to flow along the surface of the back channel side in the channel layer region.

As described above, since the operating current I _ON is related to the resistance of the channel layer, it is advantageous to make the channel layer crystalline to increase the operating current I _ON . That is, since the crystalline structure has a more regular structure than the amorphous structure, the charge mobility when the current flows is significantly higher than that in the amorphous structure. Therefore, when the channel is on, a high magnitude of the high operating current I _ON can be expected.

In contrast, when the channel is off, the leakage current I _OFF depends on the surface resistance of the back channel side of the channel layer and the bulk resistance of the back channel. Therefore, in the present invention, since the back channel is made of the high resistance second silicon film 17b, the leakage current I _OFF can be significantly lowered.

Thus, by controlling the thickness of the double layer of the active layer 17, it is possible to adjust the operating current (I _on ), leakage current (I _off ) and the ratio (I _on / I _off ).

As described above, the embodiments disclosed herein are not intended to limit the thin film transistor liquid crystal display device and the method of manufacturing the same, and may be variously modified without departing from the scope of the present invention.

As described above, the thin film transistor liquid crystal display device and the manufacturing method thereof according to the present invention have the following effects.

In the present invention, the optimum thin film transistor characteristics can be obtained by increasing the operating current (I _on ) and lowering the leakage current (I _off ) by adjusting the thicknesses of the first silicon film and the second silicon film of the channel active layer. A thin film transistor liquid crystal display device can be manufactured.

Claims (12)

Forming a gate electrode on the transparent insulating substrate; Forming an active layer including a gate insulating layer and a double layer of a first silicon layer and a second silicon layer having different resistances on the transparent insulating substrate on which the gate electrode is formed; Depositing a metal film for a source electrode and a drain electrode on the resultant of the transparent insulating substrate, and then patterning the metal film to form a source electrode and a drain electrode; Forming a protective film on an entire surface of the transparent insulating substrate on which the source electrode and the drain electrode are formed, and then forming a via hole exposing a portion of the source electrode; And And forming a pixel electrode in contact with the source electrode exposed through the via hole on the passivation layer. The method of claim 1, And wherein the first silicon film has a smaller resistance value than the second silicon film. The method of claim 2, And wherein the first silicon film is a microcrystalline silicon film and the second silicon film is an amorphous silicon film. The method of claim 3, wherein The thickness ratio of the microcrystalline silicon film and the amorphous silicon film is 2 to 8, the manufacturing method of the thin film transistor liquid crystal display device. The method of claim 3, wherein And the thickness of the microcrystalline silicon film is 100 to 200 microseconds, and the thickness of the amorphous silicon film is 800 to 2,000 microseconds. The method of claim 1, The amorphous silicon film is a method of manufacturing a thin film transistor liquid crystal display device, characterized in that formed by adding a small amount of oxygen or nitrogen as an impurity. Transparency insulation substrate, A gate insulating film formed on the transparent insulating substrate, An active layer formed on the gate insulating film and exposing a channel portion, the active layer including a double film of a first silicon film and a second silicon film having different resistance values; A source electrode and a drain electrode formed on the active layer, A protective film formed on the source electrode and the drain electrode, and And a pixel electrode formed on the passivation layer and electrically connected to the source electrode. The method of claim 7, wherein And the first silicon film has a smaller resistance value than the second silicon film. The method of claim 8, And the first silicon film is a microcrystalline silicon film, and the second silicon film is an amorphous silicon film. The method of claim 9, And the thickness ratio of the microcrystalline silicon film and the amorphous silicon film is 2 to 8. The method of claim 10, And the microcrystalline silicon film has a thickness of 100 to 200 microseconds, and the amorphous silicon film has a thickness of 800 to 2,000 microseconds. The method of claim 7, wherein The amorphous silicon film is formed by adding a small amount of oxygen or nitrogen as an impurity.