Resist for forming pattern and method for forming pattern using the same

A method for forming a pattern includes forming an etching object layer on a substrate, applying a resist on an etching object layer, the resist including a photo-initiator, and a liquid pre-polymer including a vinyl functional group and a hydrophilic functional group, shaping the resist using a mold plate having an imprint formed therein, and hardening the resist to form a resist pattern while the mold plate shaping the resist corresponding to the imprint.

The present invention claims the benefit of Korean Patent Application No. 45699/2004 filed in Korea on Jun. 18, 2004, which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a resist for forming a pattern and a method for forming a pattern using the same, and more particularly, to a method for forming a pattern by an in-plane printing method and a resist for the in-plane printing method.

2. Discussion of the Related Art

In general, a flat panel display device, such as a liquid crystal display (LCD) device, displays images using an active device at each pixel. For example, the active device includes a thin film transistor. Such a display device has a plurality of active devices arranged in a matrix and is driven by an active matrix driving method.

FIG. 1is a plane view illustrating a structure of a liquid crystal display device according to the related art. InFIG. 1, a LCD device includes a plurality of gate lines4and data lines6intersecting each other, thereby defining a plurality of pixels1arranged in a matrix. The gate lines4receives a scan signal applied from a gate driving circuit (not shown), and the data lines6receives an image signal from a data driving circuit (not shown).

In addition, the LCD device also includes a thin film transistor (TFT) as an active device in each of the pixels1. The TFT includes a gate electrode3connected to a respective one of the gate lines4, a semiconductor layer8formed on the gate electrode3, and a source/drain electrode5formed on the semiconductor layer8. The semiconductor layer8becomes activated when the scan signal is applied to the gate electrode3from the respective gate line4. In addition, when the semiconductor layer8is activated, the image signal is applied to the source/drain electrode5from a respective one of the data lines6.

A pixel electrode10is formed at a display region of each of the pixels1electrically connected to the source/drain electrode5. The pixel electrode10generates an electric field with another electrode, e.g., a common electrode (not shown), to align liquid crystal molecules (not shown) in accordance with the image signal applied through the source/drain electrode5when the semiconductor layer8is activated. As a result, the alignment of the liquid crystal molecules is controlled, such that the light transmittance thereof is controlled to display images.

FIG. 2is a cross-sectional view illustrating a structure of a thin film transistor of the liquid crystal display device illustrated inFIG. 1. As shown inFIG. 2, the TFT is formed on a substrate20. The substrate20is formed of a transparent insulating material, such as glass. In particular, the gate electrode3is formed on the substrate20, a gate insulating layer22formed on the entire surface of the substrate20covering the gate electrode3is formed, the semiconductor layer8formed on the gate insulating layer22, the source/drain electrode5formed on the semiconductor layer8, and a passivation layer25formed on the source/drain electrode5for protecting the device.

In general, in an active matrix type LCD device, each pixel has a size of about several tens of μm. Accordingly, the active device, such as the TFT, arranged in the pixel has to be formed to have a minute size of about several μm. Further, as the demand for a display device of a high image quality, such as an HDTV, increases, more pixels have to be arranged on a screen of the same area. Accordingly, an active device pattern arranged in each pixel including a gate line pattern and a data line pattern has to be also formed to have an even smaller size.

In accordance with the related art, a TFT, a pattern, or a line are formed by a photolithography process using an exposing device. However, the photolithography process includes a series of processes, such as a photoresist deposition, an alignment process, an exposure process, a developing process, an etching process, a stripping process, and the like. Thus, the photolithography process is timing consuming.

In addition, photo-masks and exposure equipment used in the photolithography process are expensive. Especially, as the photolithographic process repeats several times to form patterns of the liquid crystal display device, fabrication cost increases and productivity decreases.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a resist for forming a pattern and a method for forming a pattern using the same that substantially obviate one or more of the problems due to limitations and disadvantages of the related art.

An object of the present invention is to provide a method for forming a pattern using an in-plane printing method without photo-masks and exposure equipment.

Another object of the present invention is to provide a resist for the in-plane printing method.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a resist for forming a pattern includes a photo-initiator, and a liquid pre-polymer including a vinyl functional group and a hydrophilic functional group.

In another aspect, a resist for forming a pattern includes a photo-initiator, a liquid hydrophilic pre-polymer forming a linear polymer by photoreaction, and a photo acid generator for activating a physical cross-linking reaction of the linear polymer.

In yet another aspect, a method for forming a pattern includes forming an etching object layer on a substrate, applying a resist on an etching object layer, the resist including a photo-initiator, and a liquid pre-polymer including a vinyl functional group and a hydrophilic functional group, shaping the resist using a mold plate having an imprint formed therein, and hardening the resist to form a resist pattern while the mold plate shaping the resist corresponding to the imprint.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 3A to 3Fare cross-sectional views illustrating a method for forming a pattern using an in-plane printing method according to an embodiment of the present invention. As shown inFIG. 3A, a substrate100includes an etching object layer101to be selectively etched to form a desired pattern on the substrate100. The etching object layer101may be a metal layer for forming, for example, an electrode of a TFT, a gate line, a data line or a pixel electrode, or a semiconductor layer for forming an active layer. In addition, the etching object layer101may be an insulating layer, such as SiOx or SiNx.

A resist103is applied over the etching object layer101. In particular, the resist103may be applied over the entire surface of the etching object layer101. The resist103includes a photo-initiator, and a liquid pre-polymer including a vinyl functional group and a hydrophilic functional group. For example, the liquid pre-polymer may have a structure shown in Chemical Formula 1.

A C0-C4alkyl group such as, hydrogen (H), fluorocarbon (CF) and a methyl group (CH3), an ethyl group (C2H5), a propyl group (C3H7) and a butyl group (C4H9) may substitute for the R1, R2and R3. Hydrophilicity may substitute for one of locations of the R4to R8. For example, the hydrophilicity may be one of OH, COOHCH3, COOC2H5, COOC3H7, COOC4H9, SOOHCH3, SOOC2H5, SOOC3H7and SOOC4H9.

When the R1, R2and R3are H, OH may substitute for R6. For example, the liquid pre-polymer may become para-hydroxystyrene having a structure shown in Chemical Formula 2.

As shown inFIG. 3B, a mold plate105is provided above the substrate100. The mold plate105includes a plurality of concave grooves107corresponding to a pattern desired to be formed on the substrate100. Although only concave grooves107are shown to be in the mold plate105, the mold plate105may have various imprints formed therein to correspond to the desired pattern.

The mold plate105may be fabricated with polydimethylsiloxane (PDMS), polyurethane, cross-linked novolac resin, or the like which has relatively high elasticity. In particular, a PDMS material having the hydrophobic property contrary to the resist103may be preferably used. Especially when the mold plate105has the hydrophobic property and the resist103has the hydrophilic property, a repulsive force is generated between the mold plate105and the resist103, thereby facilitating the formation of a resist pattern as discussed in more details below.

After the mold plate105is aligned with the resist103, pressure is applied, such that a contact surface of the mold plate105becomes in contact with the etching object layer101. In particular, a capillary force is generated between the mold plate105and the substrate100by the pressure, and a repulsive force is generated between the mold plate105and the resist103due to the contrary properties of the mold plate105and the resist103. As a result, the resist103moves inside the grooves107of the mold plate105as shown by the arrows inFIG. 3B, and the mold plate105holds the resist103into a desired shape.

As shown inFIG. 3C, while the resist103is inside of the grooves107, the resist103is hardened to form a resist pattern103a. For example, UV is irradiated using an UV source (not shown) to harden the resist103by photoreaction. The resist pattern103amay be a linear polymer pattern.

Here, when the resist103includes the liquid pre-polymer having para-hydroxystyrene, the liquid pre-polymer generates a linear polymer of a structure shown in [Chemical Formula 4] by light.

When light is irradiated and when the resist103includes the para-hydroxystyrene, a linear polymer is generated as the photo-initiator leads generation of radical, thereby generating polymerization centering around a vinyl group of the para-hydroxystyrene. In addition, the resist103also may include a photo acid generator. The photo acid generator lengthens a polymer chain, such that a physical cross-linking reaction occurs by activating the physical cross-linking reaction of the linear polymer chain, thereby increasing molecular weight. The photo acid generator includes one of triarylsulfonium salt and organic sulfonic ester. For example, the triarylsulfonium salt includes onium salt, and the organic sulfonic ester includes one of nitrobenzyl sulfonate and imidosulfonate.

The resist103may have the liquid hydrophillic pre-polymer, photo-initiator and photo acid generator which are mixed in the range of about 10 to 15 WT %, 80 to 90 WT % and 2 to 8 WT %, respectively. In particular, the resist103may preferably include 5 WT % of the photo acid generator.

As shown inFIG. 3D, after the resist pattern103ais formed, the mold plate105is separated from the substrate100. Thus, the resist pattern103aremains on portions of the etching object layer101.

As shown inFIG. 3E, the etching object layer101is etched by using the resist pattern103aas a mask. For example, the etching object layer101is etched using a general etching process, e.g., a dry etch or a wet etching, to form a desired pattern101a. The pattern101amay be an metallic structure, e.g., an electrode, a semiconductor structure, e.g., an active layer, or an insulating structure, e.g., a contact hole.

As shown inFIG. 3F, the resist pattern103ais removed from the substrate100after the desired pattern101ais formed. The resist pattern103amay be removed by using a stripping process. For example, a stripper including organic solvents, such as organic amine, N-methylpyrrolidinone, toluene, or xylene, may be used to remove the resist pattern103a.

Accordingly, the method for forming a pattern using an in-plane printing method according to an embodiment of the present invention includes applying a resist on an etching object layer, shaping the resist using a mold plate having at least a groove, and hardening the resist to form a resist pattern while the mold plate holding the shape of the resist. In particular, pressure is applied to contact the mold plate with the etching object layer, thereby shaping the resist. In addition, a repulsive force is generated between the mold plate and the resist to shape the resist. In particular, the resist may have a hydrophilic property and the mold plate may have a hydrophobic property, such that the repulsive force may be generated due the contrary properties of the resist and the mold plate. As a result, the resist conforms to any imprint in the mold plate, e.g., moving inside the groove of the mold plate.

The resist hardens and forms a linear polymer when light is irradiated thereon, thereby forming a resist pattern. Because the mold plate holds the shape of the resist while the resist pattern is formed, more precise and more minute patterns may be formed. Furthermore, the resist also may include a photo acid generator which restraints a reaction if a chain of a linear polymer is too long after the initiation, and simultaneously promotes the reaction if a chain of the linear polymer is too short.

The resist pattern may be a positive photoresist pattern. The photoresist also may be a negative photoresist in which a pattern is left on a region where light is irradiated or a positive photoresist in which a pattern is left on a region where light is not irradiated. A negative photoresist undergoes a chemical cross-linking reaction by light irradiation and forms a branched polymer on the region where light is irradiated. In contrast, a positive resist undergoes a physical crosslinking reaction by light irradiation and forms a linear polymer on the region where light is irradiated. Accordingly, the negative photoresist is not easily removed by the stripper, while the positive photoresist is easily removed by the stripper. Thus, the resist according to an embodiment of the present invention forms a resist pattern having a linear polymer by light irradiation. Such a resist pattern is easily removable by a stripper. For example, a stripper including an organic solvent that is generally available.

The method for forming a pattern using an in-plane printing method according to an embodiment of the present invention simplifies fabrication processes by forming a pattern by the in-plane printing method and form a precise pattern by forming a pattern by using a resist which is easily removed by the generally available stripper. Accordingly, the method for forming a pattern using an in-plane printing method according to an embodiment of the present invention does not use an expensive photo-mask, thereby reducing fabrication costs and improving production efficiency. In addition, the method for forming a pattern using an in-plane printing method according to an embodiment of the present invention may form a device on a semiconductor wafer or an active device on a glass substrate.

It will be apparent to those skilled in the art that various modifications and variations can be made in the resist for forming a pattern and the method for forming a pattern using the same of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.