KR20030057966A - Liquid Crystal Display Device and Fabricating Method Thereof - Google Patents

Abstract

PURPOSE: A liquid crystal display device and a method for fabricating the same are provided to overlap signal lines with pixel electrodes for forming the pixel electrodes to side surfaces of protrusion parts of the signal lines by forming the protrusion part to a protecting film, thereby reducing the overlapping area between the signal lines and the pixel electrodes and reducing the parasitic capacitance. CONSTITUTION: A liquid crystal display device includes gate lines(32) formed on a substrate for supplying scanning signals, data lines(34) intersecting the gate lines and supplying data signals, gate electrodes(36) connected to the gate lines, source electrodes connected to the data lines, drain electrodes(40) facing the source electrodes, an organic protecting film(48) with protrusions(A,B) on areas corresponding to the gate and data lines, and pixel electrodes(52) extended to a part of the protruded areas of the organic protecting film to be formed on the protecting film.

Description

Liquid crystal display device and its manufacturing method {Liquid Crystal Display Device and Fabricating Method Thereof}

The present invention relates to a liquid crystal display device and a method for manufacturing the same, and more particularly, to a liquid crystal display device and a method for manufacturing the same that can reduce parasitic capacitance.

In general, a liquid crystal display (LCD) displays an image by adjusting the light transmittance of the liquid crystal using an electric field. To this end, the liquid crystal display device includes a liquid crystal panel in which liquid crystal cells are arranged in a matrix, and a driving circuit for driving the liquid crystal panel. The liquid crystal panel includes pixel electrodes for applying an electric field to each of the liquid crystal cells and a reference electrode, that is, a common electrode. In general, the pixel electrode is formed for each liquid crystal cell on the lower substrate, while the common electrode is integrally formed on the front surface of the upper substrate. Each of the pixel electrodes is connected to a thin film transistor (TFT) used as a switching element. The liquid crystal cell is driven along with the common electrode in accordance with the data signal supplied through the TFT.

In order to protect this TFT, a protective layer is formed between the pixel electrode and the TFT. The protective layer is formed of an inorganic insulating material such as SiNx or SiOx. Since the inorganic dielectric material has a high dielectric constant, pixel electrodes and data lines disposed between the inorganic insulating materials had to be kept at regular intervals, for example, 3 to 5 μm, in order to minimize the coupling effect of the parasitic capacitor. As a result, the size of the pixel electrode which determines the aperture ratio of the liquid crystal cell is reduced by that much, which inevitably leads to a low aperture ratio. In order to solve this problem, recently, an organic insulating material having a relatively low dielectric constant such as benzocyclobutene (BCB) is used as a protective layer. Since the organic insulating film has a low dielectric constant of about 2.7, the pixel electrode and the data line can be overlapped, thereby increasing the size of the pixel electrode and improving the aperture ratio.

1 and 2, a lower substrate 1 of a liquid crystal display device using an organic insulating material as a protective layer may include a TFT (T) positioned at an intersection of the data line 4 and the gate line 2; The pixel electrode 22 connected to the drain electrode 10 of TFT (T) is provided.

The TFT T is a gate electrode 6 connected to the gate line 2, a source electrode 8 connected to the data line 4, and a drain electrode connected to the pixel electrode 22 through the contact hole 20. It consists of 10. In addition, the TFT (T) further includes semiconductor layers 14 and 16 for forming a channel between the source electrode 8 and the drain electrode 10 by the gate voltage supplied to the gate electrode 6. The TFT T selectively supplies the data signal from the data line 4 to the pixel electrode 22 in response to the gate signal from the gate line 2.

The pixel electrode 22 is formed in a cell region divided by the data line 4 and the gate line 2 and is made of a transparent conductive material having high light transmittance. The pixel electrode 22 generates a potential difference from a common electrode (not shown) formed on the upper substrate (not shown) by the data signal supplied through the contact hole 20. Due to this potential difference, the liquid crystal located between the lower substrate 1 and the upper substrate (not shown) is rotated by the dielectric anisotropy. Accordingly, the light supplied from the light source via the pixel electrode 22 is transmitted to the upper substrate.

3A to 3E are views illustrating a method of manufacturing the lower substrate of the liquid crystal display shown in FIG. 2.

First, the gate line 2 and the gate electrode 6 are formed by coating and patterning a metal film on the lower substrate 1 as shown in FIG. 3A. The gate insulating film 12 is formed by depositing the entire surface on the lower substrate 1 so as to cover the gate line 2 and the gate electrode 6. By sequentially depositing and patterning the first and second semiconductor materials on the gate insulating layer 12, the active layer 14 and the ohmic contact layer 16 are formed as shown in FIG. 3B. Subsequently, a metal film is coated on the gate insulating film 12 and then patterned to form the data line 4, the source electrode 8, and the drain electrode 10, as shown in FIG. 3C. To form the ohmic contact layer 16 is etched so that the active layer 14 is exposed. The contact hole 20 is formed so that the drain electrode 10 is exposed as shown in FIG. 3D by depositing and patterning the surface of the organic protective film 18 on the gate insulating film 12 by spin coating. do. Next, a transparent conductive material is applied and patterned on the organic protective film 18 to form a pixel electrode 22 electrically connected to the drain electrode 10 as shown in FIG. 3E.

The conventional pixel electrode 22 is disposed to overlap the gate line 2 and the data line 8 on the passivation layer 18 formed of an organic insulating film having a low dielectric constant to increase the aperture ratio. In order to prevent light leakage, the pixel electrode 22 may have different overlapping regions between the gate line 2 and the data line 4 depending on the material of the passivation layer 18 and the rubbing direction.

In detail, first, when the protective film 18 is formed of BCB, the rubbing direction of the lower plate is 315 °, the rubbing direction of the upper plate is 135 °, and the liquid crystal is -90 ° twisted nematic. The first data overlap region b1 overlapping the pixel electrodes 22 is about 2 to 4 μm, and the second data overlap region b2 is about 0 to 2 μm. The first gate overlapping region a1 overlapping the gate line 2 and the pixel electrode 22 is 4 μm.

When the protective film 18 is formed of BCB, and the rubbing direction of the lower plate is 225 °, the rubbing direction of the upper plate is 45 °, and the liquid crystal is + 90 ° twisted nematic, the data line 4 and the pixel electrode 22 overlap each other. The first data overlap region b1 is about 0 to 2 μm, and the second data overlap region b2 is about 2 to 4 μm. The first gate overlap region a1 overlapping the gate line 2 and the pixel electrode 22 is about 3.5 μm or more.

When the passivation layer 18 is formed of photo acryl, the first and second data overlapping regions b1.b2 overlapping the data line 4 and the pixel electrode 22 may be BCB. The first gate overlap region a1 overlapping the gate line 2 and the pixel electrode 22 is about 3 to 3.5 µm, and the second gate overlap region a2 is about 4.5 to 5 micrometers.

As such, the overlapping region of the data line 4 or the gate line 2 and the pixel electrode 22 affects the parasitic capacitor as shown in Equation (1).

Here, "C" parasitic capacitance, "ε" is the dielectric constant of the organic protective film 18, "ε ₀ " is 8.85 × 10 ^-14 F / Cm, "A" is the pixel electrode 22 and the data line (4) or the overlapping region of the pixel electrode 22 and the gate line 2, " d " represents the thickness of the organic protective film 18, respectively.

As described above, if the thickness and the dielectric constant of the organic passivation layer 18 are constant, the parasitic capacitance C is a region where the pixel electrode 22 and the data line 4 or the pixel electrode 22 and the gate line 2 overlap. Will be affected. In other words, when the overlap region is large, the parasitic capacitance C is increased, and the capacitance C on the gate line 2 or the data line 4 is increased. The parasitic capacitance C having such a large value increases the delay value of the signal supplied to the gate line 2 or the data line 4, thereby preventing the liquid crystal pixel from sufficiently charging the video signal within the limited charging time. . As a result, the image is distorted, such as a desired color signal cannot be expressed.

Accordingly, an object of the present invention is to provide a liquid crystal display device and a method for manufacturing the same, which can reduce parasitic capacitance.

1 is a cross-sectional view showing a conventional liquid crystal display device.

FIG. 2 is a plan view illustrating a lower substrate of the liquid crystal display shown in FIG. 1.

3A to 3E are cross-sectional views illustrating a method of manufacturing a lower substrate of a liquid crystal display device taken along a line "A-A '" in FIG.

4 is a cross-sectional view showing a liquid crystal display device according to the present invention.

5A and 5B show the shape of a protective layer formed on a signal line;

FIG. 6 is a view showing a displacement region shown on the protective layer shown in FIG. 5B. FIG.

7A and 7B illustrate light transmittance according to the form of a protective layer.

8A to 8G are cross-sectional views illustrating a method of manufacturing a lower substrate of the liquid crystal display shown in FIG. 4.

<Description of Symbols for Main Parts of Drawings>

1,31: Lower substrate 2,32: Gate line

4,34 data line 6,36 gate electrode

8,38 source electrode 10,40 drain electrode

12,42 gate insulating film 14,44 active layer

16,46: ohmic contact gun 18,48: protective film

20,50: contact hole 22,52: pixel electrode

In order to achieve the above object, the liquid crystal display device according to the present invention is formed on a substrate, a gate line to which the scanning signal is supplied, a data line to cross the gate line and a data signal to be supplied, and a gate connected to the gate line. An electrode, a source electrode connected to the data line, a drain electrode formed to face the source electrode, an organic protective film protruding from a region corresponding to the gate line and the data line, and extending to a part of the protruding region of the organic protective film. And a pixel electrode formed on the organic protective film.

The pixel electrode may be formed to extend to the side of the protruding region of the organic passivation layer.

The pixel electrode is formed to overlap both sides of the gate line 2 to 5㎛ each.

The pixel electrode may be formed to overlap both sides of the data line with 0 to 3.5 μm, respectively.

The protruding region of the organic protective layer is about 500 mm thicker than that of the relatively flat organic protective layer.

The length of the protruding region of the organic protective layer formed in the region corresponding to the gate line is about 6 ~ 8.5㎛.

The length of the protruding region of the organic passivation layer formed in the region corresponding to the data line is about 4 to 6.5㎛.

In order to achieve the above object, a method of manufacturing a liquid crystal display device according to the present invention comprises the steps of forming a gate electrode and a gate line on a substrate, forming a gate insulating film on the substrate, and a semiconductor layer on the gate insulating film Forming a data line, forming a data line, a source and a drain electrode on the gate insulating film, forming an organic passivation layer protruding from a region corresponding to the data line and the gate line, and forming a portion of the protruding region of the organic passivation layer. Extending to form a pixel electrode on the organic passivation layer.

The pixel electrode is formed so that both sides of the gate line overlap each other 2 to 5 μm, and both sides of the data line overlap each other 0 to 3.5 μm.

The protruding region of the organic protective layer is about 500 mm thicker than that of the relatively flat organic protective layer.

Other objects and features of the present invention in addition to the above objects will become apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 4 to 8.

4 is a cross-sectional view illustrating a liquid crystal display device according to an exemplary embodiment of the present invention, and particularly, a thin film transistor unit, a gate line unit, and a data line unit.

The thin film transistor unit illustrated in FIG. 4 has a gate electrode 36, an active layer 44 and an ohmic contact layer 46 stacked between the gate electrode 36 and the gate insulating layer 42, and an ohmic contact layer 46. And a source electrode 38 and a drain electrode 40 formed separately from each other.

A protective layer 48 is formed of an organic insulating material on the gate insulating layer 42 to protect the thin film transistor. The pixel electrode 52 is formed on the passivation layer 48 to be in contact with the drain electrode 40 through the contact hole 50 passing through the passivation layer 48.

In the gate line portion, a gate line 32, a gate insulating film 42, and a protective layer 48 are formed thereon. The gate line 32 supplies a gate signal to the gate electrode 32 of the thin film transistor portion.

In the data line portion, a data line 34 positioned on the gate insulating layer 42 and a protective layer 48 are formed thereon. The data line 34 supplies a data signal to the source electrode 38 of the thin film transistor portion.

The organic passivation layer 48 of the gate line part and the data line part may form protrusions A and B which protrude relatively in a region corresponding to the gate line 32 and the data line 34. The ideal protrusions A and B are formed to protrude about 500 mm from the area corresponding to the TFT. The length d of the protrusion B corresponding to the gate line 32 is formed to about 6 ~ 8.5㎛, preferably about 7㎛. The length C of the protrusion A corresponding to the data line 34 is about 4 to 6.5 μm, and preferably about 4 μm. In addition, the width of the data line 34 is preferably about 10 μm, and the length of the gate line 32 is preferably about 15 μm.

The pixel electrode 52 formed on the organic passivation layer 48 having the protrusions A and B has the same area as the conventional one, and at the same time the overlapping area of the pixel electrode 52 and the signal lines 32 and 34 is reduced. Parasitic capacitors are reduced.

In detail, the pixel electrodes 52 and the signal lines 32 and 34 overlapping each other with the insulating layers 42 and 48 interposed therebetween have different potentials so that electric field lines cancel each other.

As illustrated in FIG. 5A, the pixel electrode 52 which is concave than the conventional flat pixel electrode is formed to be relatively far from the signal lines 32 and 34. Due to the distance between the relatively distant pixel electrode 52 and the signal lines 32 and 34, the amount of electric field lines canceled is relatively small. Accordingly, the free energy is increased, the movement of the liquid crystal is relatively active, and the disclination area is reduced.

On the other hand, the convex pixel electrode 52 has a relatively close distance to the signal lines 32 and 34, as shown in FIG. 5B. The amount of electric field lines is canceled by the distance between the pixel electrode 52 and the signal lines 32 and 34 that are relatively close. As a result, as shown in FIG. 6, a portion having low free energy is widely distributed, so that the movement of the liquid crystal becomes smaller, so that a disclination area is widened, so that the screen is white in the revolving area.

Accordingly, when the pixel electrode is formed flat, the free energy is relatively higher than that of the convex pixel electrode 52, thereby causing the liquid crystal to move. When the pixel electrode 52 is concave, the free energy becomes higher and the liquid crystal moves. It can be seen that the active region is smaller than the flat pixel electrode 52, so that the convex region is reduced.

7A and 7B illustrate transmittance according to the distance between the pixel electrode 52 and the signal lines 32 and 34. In the figure, the horizontal axis represents the distance between the pixel electrode 52 and the signal lines 32 and 34, the vertical axis represents the light transmittance, A is a flat pixel electrode, B is a concave pixel electrode, and C is a convex pixel electrode. Indicates.

Referring to FIG. 7A, in the second overlapping region a2 of the gate electrode 32 and the concave pixel electrode 52, the transmittance is reduced by about 10% compared to the prior art, and thus decreases by about 1 μm. The area a1 has a transmittance of about 2% and decreases by about 0.2 μm. Accordingly, the first overlapping region a1 of the gate line 32 and the pixel electrode 52 is formed to be about 2 to 4 µm and the second overlapping region a2 is about 3 to 5 µm.

Referring to FIG. 7B, the second overlapping region b2 of the data line 34 and the concave pixel electrode 52 has a transmittance of about 4.5%, which is reduced by about 0.5 μm, and the first overlap of the first overlapping region b2 of the pixel electrode 52. The area b1 has almost no change. Accordingly, the first overlapping region b1 of the data line 34 and the pixel electrode 52 is formed to about 0 to 2 μm, and the second overlapping region b2 is about 1.5 to 3.5 μm.

A method of manufacturing a liquid crystal display device having such a concave organic protective film 48 will be described with reference to FIGS. 8A to 8G.

Referring to FIG. 8A, a gate metal layer is deposited on the substrate 31 by a deposition method such as sputtering. Aluminum (Al), copper (Cu), or the like is formed as the gate metal layer. Subsequently, the gate line 32 and the gate electrode 36 are formed by patterning the gate metal layer by a photolithography process including an etching process.

Referring to FIG. 8B, a gate insulating layer 42 is formed on the substrate 31 on which the gate line 32 and the gate electrode 36 are formed. The gate insulating layer 42 is formed of an inorganic insulating material, silicon oxide (SiOx) or silicon nitride (SiNx). On the gate insulating layer 42, the first and second semiconductor layers are continuously deposited by chemical vapor deposition. The first semiconductor layer is formed of amorphous silicon that is not doped with impurities, and the second semiconductor layer is formed of amorphous silicon doped with N or P impurities. Subsequently, the first and second semiconductor layers are patterned by a photolithography method including a dry etching process to form an active layer 44 and an ohmic contact layer 46.

Referring to FIG. 8C, a data metal layer is deposited on the gate insulating layer 42 on which the active layer 44 and the ohmic contact layer 46 are formed by a deposition method such as a CVD method or sputtering. The data metal layer is formed of chromium (Cr) or molybdenum (Mo). Subsequently, the data metal layer is patterned by a photolithography process including a wet etching process to form the data line 34, the source electrode 38, and the drain electrode 40. Next, the ohmic contact layer 46 exposed between the source electrode 38 and the drain electrode 40 is removed by a dry etching process to separate the source electrode 38 and the drain electrode 40. By partially removing the ohmic contact layer 46, the portion of the active layer 44 corresponding to the gate electrode 36 between the source and drain electrodes 38 and 40 becomes a channel.

Referring to FIG. 8D, an organic insulating material 48a is formed on the gate insulating layer 42 on which the data lines 34, the source and drain electrodes 38 and 40 are formed. As the material of the organic insulating material 48a, an organic insulating material having a low dielectric constant such as an acryl organic compound, Teflon, BCB (benzocyclobutene), cytotope, or perfluorocyclobutane (PFCB) is used.

On this organic insulating material 48a, the photoresist 54 is entirely coated with a uniform thickness. Subsequently, the mask 56 is aligned on the photoresist 54. As the mask 56, a transflective mask or a slit mask for patterning the photoresist 54 to different thicknesses is used. The mask 56 is composed of a transmissive portion 56a for transmitting all the amount of incident light, a blocking portion 56c for blocking all the amount of incident light, and a transflective portion 56b formed of a semi-transmissive material and transmitting a portion of the incident light. .

Referring to FIG. 8E, in the state where the mask 56 is aligned, the photoresist 54 is patterned by an exposure and development process and a wet etching process to form a photoresist pattern 58. The photoresist pattern 58 is left in the remaining area except for the position where the contact hole is to be formed. That is, the photoresist pattern 58 formed in the region corresponding to the data line 34 and the gate line 32 has an approximately initial thickness, and the remaining thickness of the photoresist pattern 58 is 10 to 50% of the initial thickness. Have.

Referring to FIG. 8F, the organic insulating material 48a is patterned using the photoresist pattern 58 as a mask. Accordingly, the contact hole 54 is formed in the region corresponding to the transmissive portion, a concave protective layer region is formed in the region corresponding to the blocking portion, and a relatively flat protective layer region is formed in the transflective portion.

The photoresist residue remaining on the lower substrate 31 is removed by a stripping process using a stripping liquid.

Referring to FIG. 8G, the transparent electrode layer is formed on the protective layer 48 by a deposition method such as sputtering. The material of the transparent electrode layer may be selected from any one of indium tin oxide (ITO), tin oxide (TO), and indium zinc oxide (IZO). Subsequently, the pixel electrode 52 is formed by patterning the transparent electrode layer by a photolithography process including an etching process. Accordingly, the pixel electrode 52 is concave in the region corresponding to the data line 34 and the gate line 32. The pixel electrode 52 is connected to the drain electrode 40 through the contact hole 50 formed on the organic insulating film 48.

As described above, the liquid crystal display device and the method of manufacturing the same according to the present invention form a protective film formed under the pixel electrode corresponding to the signal line to have a protrusion. As a result, the pixel electrode overlaps the signal line and is formed to the side of the protrusion of the signal line, thereby reducing the overlapping area between the signal line and the pixel electrode, thereby reducing parasitic capacitance. Reduced parasitic capacitance results in better image quality.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (10)

A gate line formed on the substrate and supplied with a scanning signal; A data line crossing the gate line and supplied with a data signal; A gate electrode connected to the gate line; A source electrode connected to the data line; A drain electrode formed to face the source electrode; An organic passivation layer protruding from a region corresponding to the gate line and the data line; And a pixel electrode which extends to a part of the protruding region of the organic passivation layer and is formed on the organic passivation layer. The method of claim 1, The pixel electrode is formed to extend to the side of the protruding region of the organic protective film. The method of claim 1, And the pixel electrode is formed to overlap both sides of the gate line at 2 to 5 탆, respectively. The method of claim 1, And the pixel electrode is formed so that both sides of the data line overlap each other at 0 to 3.5 占 퐉. The method of claim 1, And a protruding region of the organic protective layer is about 500 GPa thicker than a region of a relatively flat organic protective layer. The method of claim 1, The length of the protruding region of the organic passivation layer formed on the gate line overlapping with the gate line is about 6 ~ 8.5㎛. The method of claim 1, The length of the protruding region of the organic passivation layer formed on the data line and the overlapping portion is about 4 ~ 6.5㎛. Forming a gate electrode and a gate line on the substrate; Forming a gate insulating film on the substrate; Forming a semiconductor layer on the gate insulating film; Forming a data line, a source and a drain electrode on the gate insulating film; Forming an organic passivation layer protruding from a region corresponding to the data line and the gate line; And forming a pixel electrode on the organic passivation layer to extend to a part of the protruding region of the organic passivation layer. The method of claim 8, The pixel electrode is formed so that both sides of the gate line overlap each other 2 to 5㎛, and both sides of the data line are formed overlapping each other 0 to 3.5㎛. The method of claim 8, The protruding region of the organic protective layer is about 500 GPa thicker than the region of the relatively flat organic protective layer.