Manufacturing method of color filter on TFT array and manufacturing method of LCD panel

A method of fabricating a color filter over a TFT array and a method of fabricating a liquid crystal display panel comprising the same are disclosed. First, a substrate having a TFT array thereon is provided. Next, a black matrix is formed over the TFT array for defining a plurality of sub-pixel regions. Next, a plurality of contact holes is formed in the black matrix. Next, an ink-jet process is performed to form a color filter pattern in each sub-pixel region respectively. Thereafter, an overcoat layer is formed over the sub-pixel regions, and then a plurality of openings is formed in the overcoat layer to expose the contact holes in the black matrix. Thereafter, pixel electrodes are formed over the overcoat layer electrically connected to the TFT array through the openings and the contact holes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a method of fabricating a color filter. More particularly, the present invention relates to a method of fabricating a color filter on a thin film transistor (TFT) array.

2. Description of Related Art

As multi-media technology advances, a variety of semiconductor devices or displays have been rapidly developed. Displays, for example, TFT liquid crystal displays, because of its advantages of high resolution, high space-effectiveness, low power consumption and non-radiation, have become the main trend in this industry.

A TFT liquid crystal display comprises a TFT array substrate, a color filter substrate, and a liquid crystal layer. According to one conventional method, the TFT array substrate and the color filter substrate are manufactured separately, and then a TFT liquid crystal display panel with the liquid crystal layer formed there-between. According to another conventional method, first, a color filter is directly formed on a TFT array substrate for reducing the problems in reduction of aperture ratio and misalignment between the TFT array substrate and the color filter substrate.

FIG. 1A to 1Fillustrate a process of fabricating a color filter on a TFT array substrate. First, a substrate100having a TFT array110thereon is provided, wherein the TFT array110comprises a plurality of gates112, a gate-insulating layer114, a plurality of semi-conductive layer116and a plurality of sources/drains118a/118b.

Next, referring toFIG. 1B, a passivation layer190is formed over the TFT array110, and a plurality of openings170ais formed in the passivation layer190to expose the drains118b.

Next, referring toFIG. 1C, red filter patterns150aare formed on the passivation190. According to an embodiment of the present invention, a red photoresist layer is formed over the passivation layer190by spin coating, and subsequently, the red photoresist layer is then exposed and then etched in a conventional photolithography process, and finally baked to form a red filter pattern150aand openings170bexposing the openings170aand thereby exposing the drains118b.

Next, referring toFIG. 1D, similarly, the above process may be repeated to form green filtering pattern150band blue filter pattern150c. Furthermore, a black matrix120may be formed between the color filters patterns150a,150b, and150c.

Next, as shown inFIG. 1E, an overcoat layer160is formed over the black matrix120and the color filtering patterns150a,150b, and150c. And a plurality of contact holes140is formed in the overcoat layer160to expose the drains118b.

Next, as shown inFIG. 1F, a plurality of pixel electrodes180is formed over the overcoat layer160and electrically connected to the drains118bof the TFT array110through the contact holes140respectively.

As described in the above conventional method, red, green, and blue filter patterns are formed separately by coating, photolithography process including exposure and etching, and baking. Therefore, the conventional process not only requires many additional process steps but is also a complicated process in which the risk of reduction in the yields is high. Furthermore, the masking step used for defining the color filter patterns would substantially increase the manufacturing cost. In addition, the difficulty in coating the color photoresist could more obvious and amplified as the size of the TFT substrate is enlarged.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a method of fabricating a color filter over a TFT array, in which ink-jet technology is applied to form the color filter patterns and thereby simplifying the fabrication process the color filter.

The present invention is also directed to a method of fabricating a liquid crystal display panel, in which ink-jet technology is applied to form the color filter patterns on the TFT array of the liquid crystal display panel. The fabrication process of the liquid crystal display can be substantially simplified.

According to an embodiment of the present invention, first, a substrate having a TFT array thereon is provided. Next, a black matrix is formed over the TFT array for defining a plurality of sub-pixel regions, and a plurality of contact holes is formed in the black matrix. Next, an ink-jet process is performed to form a color filter pattern in each sub-pixel region. Next, an overcoat layer is formed over the sub-pixel regions, and a plurality of openings is formed in the overcoat layer to expose the contact holes in the black matrix. Thereafter, a plurality of pixel electrodes is formed over the overcoat layer, wherein the pixel electrodes are electrically connected to the TFT array through the openings and the contact holes.

A method of fabricating a liquid crystal display panel according to an embodiment of the present invention is described as follows. First, a first substrate having a TFT array thereon is provided. Next, a black matrix is formed over the TFT array for defining a plurality of sub-pixel regions, and a plurality of contact holes are formed in the black matrix. Next, an ink-jet process is performed to form a color filter pattern in each sub-pixel region. Next, an overcoat layer is formed over the sub-pixel regions, and a plurality of openings is formed in the overcoat layer to expose the contact holes in the black matrix. Thereafter, a plurality of pixel electrodes is formed over the overcoat layer, wherein the pixel electrodes are electrically connected to the TFT array through the openings and the contact holes. Next, a liquid crystal layer is formed over the pixel electrodes and a second substrate is disposed over the liquid crystal layer so that the liquid crystal layer is formed between the first substrate and the second substrate.

According to an embodiment of the present invention, the second substrate, for example, comprises a glass substrate and a common electrode film is formed over the glass substrate.

According to an embodiment of the present invention, the second substrate, for example, comprises a glass substrate, and a plurality of common electrodes may be formed over the overcoat layer after the process of forming the pixel electrodes over the overcoat layer.

According to an embodiment of the present invention, a passivation layer may be formed over the TFT array before forming the black matrix.

According to an embodiment of the present invention, the black matrix may be formed, for example, by forming a material layer over the substrate and then patterning the material layer. The method of forming the material layer may be spin coating, slit/spin coating, or spin-less coating. In addition, the material layer may be black resin.

According to an embodiment of the present invention, the ink-jet process described above may include, for example, printing a color filter pattern in each sub-pixel region and baking the color filter pattern.

According to an embodiment of the present invention, the material of the overcoat layer may be an organic photosensitive resin selected from the group consisting of Benzocyclobutene, Acrylic, Polyimide, Styrene, and combinations thereof.

In the present embodiment of the present invention, color filter patterns of different colors can be simultaneously formed by the ink-jet process including ink-jetting and baking. Accordingly, the method of the present invention is substantially simpler and superior compared to the conventional method of forming the red, green, and blue filter patterns described above. In addition, the coating problems associated with the increase in the size of the TFT substrate during coating of the color photoresist can be effectively eliminated. Furthermore, because the masking process is not required for forming the filter patterns, therefore the overall fabrication cost can be effectively reduced. Accordingly, the fabrication process of the present invention being simpler due elimination of masking process used in the conventional method, therefore the problems due to coating and misalignment can be effectively eliminated and thus not only the manufacturing cost is reduced but also process yield can be effectively promoted.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, the method of fabricating the color filter over the TFT array substrate, according to an embodiment of the present invention, will be described with reference toFIG. 2A to 2EandFIG. 3A to 3B. First, referring toFIG. 2A, a substrate100having a TFT array110thereon is provided. As shown inFIG. 2A, the TFT array110comprises a plurality of gates112, a gate-insulating layer114covering the gates112is covered with the gate-insulating layer114, semi-conductive layers116comprising, for example, channels and ohmic contact layers thereon, formed over the gate-insulating layer114; and source/drain regions118a/118bover the semi-conductive layers116.

Next, as shown inFIGS. 2B and 3A, a patterned black matrix220is formed over the TFT array110for defining a plurality of sub-pixel regions and a plurality of contact holes240are formed in the black matrix220to expose a portion of the drains118bof the TFT array110. According to an embodiment, the patterned black matrix220, for example, can be formed by first forming a material layer on the substrate100first, and then patterning the material layer. The material layer may be formed over the substrate100by performing spin coating, slit/spin coating, or spin-less coating. The material layer may be patterned by utilizing the conventional photolithography process including exposure and etching, and baking. According to an embodiment of the present invention, the material layer comprises, for example, black resin.

Next, referring toFIGS. 2C,2D, and3B, an ink-jet process is performed to form a color filter pattern252comprising red, blue and green color in each sub-pixel region230respectively. It should be noted that the color filter pattern252comprising red, blue and green colors is formed in substantially one process step by injecting respective color ink250into the sub-pixel regions230via nozzles50respectively. Subsequently, color filter pattern252is baked as shown inFIG. 2D. According to the present embodiment, because the color filter pattern252comprising red, green and blue colors is formed substantially by a single process including injection and baking steps for forming red, blue and green filters, therefore the fabrication process of forming the color filter pattern is substantially more simpler compared to the conventional process described above.

Thereafter, as shown inFIG. 2D, an overcoat layer260is formed over the sub-pixel regions230, and then a plurality of openings270is formed in the overcoat layer260to expose the contact holes240in the black matrix220. According to an embodiment of the present invention, a spin coating method may be utilized to form the overcoat layer260, wherein a overcoat material may be spin coated over the color filter pattern252and the black matrix220and then the overcoat material layer is baked to form the overcoat layer260. According to an embodiment of the present invention, a conventional photolithography process including exposure and etching steps may be utilized for patterning the overcoat layer260to form the openings270. The overcoat layer260comprises, for example but not limited to, an organic photosensitive resin selected from the group consisting of Benzocyclobutene, Acrylic, Polyimide, Styrene, and combinations thereof.

Next, as shown inFIG. 2E, a plurality of pixel electrodes280are formed over the overcoat layer260for electrically connecting to the drains118bof the TFT array110through the openings270(as shown inFIG. 2D) and contact holes240(as shown inFIG. 2D). The pixel electrodes280comprise, for example but not limited to, transparent conductive films made of Indium Tin Oxide (ITO). According to an embodiment of the present invention, the pixel electrodes may be formed over the overcoat layer260via, for example, conventional sputtering and photolithography processes. In the present embodiment, due to the advantages of lower dielectric constant, higher heat-resistance, and thinness/flatness of the overcoat layer260(organic photosensitive resin), the pixel electrodes280can be easily formed above scan lines or data lines and provide a higher aperture ratio.

FIG. 4illustrates a schematic drawing of a color filter over a TFT array according to another embodiment of the present invention. Referring toFIG. 4, before forming the black matrix220, a passivation layer290may be formed over the TFT array110, and then a plurality of contact holes240may be formed in the passivation layer290to expose the drains118bof the TFT array110. The material of the passivation layer290, for example, is silicon nitride (SiNx). Hereinafter, the fabrication process of the passivation layer290is described. First, a silicon nitride layer is formed over the TFT array110, and then a patterned photoresist layer is formed over the silicon nitride layer. Next, the silicon nitride layer is etched to form the contact holes240in the passivation layer290using the patterned photoresist layer as an etching mask. Next, the patterned photoresist layer is removed.

Hereinafter, the method of fabricating a liquid crystal display panel according to an embodiment of the present invention will described with reference toFIGS. 5A and 5B. Referring toFIG. 5A, a black matrix220is formed over a substrate100having a TFT array110thereon for defining a plurality of sub-pixel regions230, and then a plurality of contact holes240in the black matrix220by performing a process similar to the process described above with reference toFIG. 2A to 2E, and therefore detail description thereof is not repeated. Next, an ink-jet process is performed for forming a color filter pattern252in each sub-pixel region230respectively. Next, an overcoat layer260is formed over the sub-pixel regions230, and then a plurality of openings270are formed in the overcoat layer260to expose the contact holes240in the black matrix220. Next, a plurality of pixel electrodes280is formed over the overcoat layer260, wherein the pixel electrodes280are electrically connected to the drains118bof the TFT array110through the openings270and the contact holes240.

Furthermore, according to another embodiment of the present invention, the passivation290(as shown inFIG. 4) is formed over the TFT array110before forming the black matrix220.

Referring toFIG. 5B, a liquid crystal layer400is formed over the pixel electrodes and then a substrate300ais disposed over the liquid crystal layer400so that the liquid crystal layer400is formed between the substrate100and substrate300a. According to an embodiment of the present invention, the substrate300a, for example, comprises a glass substrate310and a common electrode film320thereon. The common electrode320may be a transparent conductive film, for example, made of Indium Tin Oxide (ITO). In addition, the liquid crystal layer400may be formed by, for example, One Drop Fill (ODF) technology. In the process of ODF technology, first, a sealant may be formed over the substrate100for surrounding a space, wherein the sealant can be a UV (ultraviolet) cured sealant. Next, the liquid crystal is dropped into the space surrounded by the sealant. Next, the substrate100and the substrate300aare aligned and assembled together under vacuum, and then the sealant is cured by UV light.

FIG. 6illustrates a schematic drawing of a liquid crystal display panel according to another embodiment of the present invention. Referring toFIG. 6, an In-Plane Switching (IPS) mode liquid crystal display panel is provided, wherein the substrate300b, for example, is a glass substrate. Furthermore, besides forming the pixel electrodes280, a plurality of common electrodes295are also formed on the overcoat layer260. It should be noted that the pixel electrodes280and the common electrodes295may be fabricated by using the process similar to those described above, and therefore detailed description thereof is not repeated.

In summary, according to the present embodiment of the present invention, an ink-jet process may be utilized to form the color filter pattern comprising red, blue and green colors for forming the red, blue and green color filters over the TFT array. Therefore, it is possible to form the red, blue and green filter patterns in a single ink-jet process including simple injection and baking process steps. Accordingly, the fabrication process of the present invention is superior compared to the conventional process where the red, green, and blue filter patterns are separately formed via complex processing steps including coating, exposure, etching and baking steps. Furthermore, because the problems associated with the coating photoresist and misalignment of mask can be effectively eliminated, therefore the process yield can be effectively promoted. In addition, the problem associated with coating color photoresist over the large size TFT substrate for forming color filters can be also be effectively eliminated. Furthermore, because the fabrication process greatly reduces the process steps of fabricating the color filters and also greatly simplifies the process compared to the conventional process, therefore the overall fabrication cost can be effectively reduced.

In summary, compared to the conventional process, the fabrication process of the present invention is capable of effectively reducing the process steps for fabricating the color filter over the TFT array by utilizing the ink-jet process where the red, blue and green color filter patterns are formed by a single process including simple injection and baking process steps, therefore the process time and fabrication cost can be effectively reduced. Furthermore, the misalignment between the TFT array substrate and the color filter substrate can also be effectively avoided. In addition, one masking process can be eliminated by replacing the passivation with the color filter patterns, the black matrix, and the overcoat layer, therefore the cost incurring from the masking process and the material used in the passivation can be effectively eliminated.