Slit coater having pre-applying unit and coating method using the same

A slit coater having a pre-applying unit and a coating method using the same that minimizes the amount of washing solution used and improves the washing effectiveness of a roller by separating the coating solution attached to a pre-applying roller from the washing solution using a coating solution separating apparatus. The slit coater includes: a table on which an object to be processed is mounted; a slit nozzle applying coating solution onto a surface of the object; a pre-applying unit to which the slit nozzle pre-applies the coating solution; and a coating solution separating unit that separates the coating solution spread when the coating solution is pre-applied to the slit nozzle and discharges the separated coating solution.

PRIORITY CLAIM

This application claims priority to Korean patent application No. 118358/2004, filed Dec. 31, 2004 the disclosure of which is incorporated by reference herein.

TECHNICAL FIELD

The present invention relates, generally, to a slit coater and, more particularly, to a slit coater and a coating method using the same for applying coating solution such as a photosensitive solution, a developer solution, and a color filter onto an object to be processed such as a semiconductor wafer, a glass substrate or a plastic substrate of a flat panel display (FPD) device.

BACKGROUND

When a flat panel display device or a semiconductor device is fabricated, a process for depositing a thin film, a photolithography process for exposing a region selected in the thin film and an etching process for removing the thin film of the selected region are performed several times. Particularly, the photolithography process includes a coating process for forming a photosensitive film of a photosensitive solution such as photoresist on a substrate or a wafer, and an exposing and developing process for patterning the photosensitive film by using a mask with a predetermined pattern.

In general, a spray coating method, a roll coating method, a spin coating method or the like is used in the coating process for forming a photosensitive film on a substrate and a wafer.

Because the spray coating method and the roll coating method are not suitable to achieve high precision in the uniformity of a coating film and the adjustment of a thickness of the film, the spin coating method is used for high-precision pattern formation.

A spin coater used in the spin coating method will now be described in detail with reference to accompanying drawings.

FIG. 1is a sectional view which illustrates a structure of a general spin coater.

As shown, the spin coater includes a spin chuck5that is connected to a rotating shaft6. A cover7that surrounds the spin chuck5and can be opened and closed. A nozzle4is placed above the spin chuck5and moves into the cover7when the cover7is opened.

An object10to be processed and be coated with a photosensitive film is mounted on the spin chuck5, and a drain valve (not shown) for discharging photosensitive solution such as photoresist to the outside is installed at a lower portion of the cover7.

In order to form a coating film on the predetermined object10, first, the nozzle4of the spin coater having the aforementioned structure is lowered and sprays photosensitive solution onto a surface of the object10, which has been placed on the spin chuck5.

When the photosensitive solution is sprayed onto the object10, the cover7is hermetically closed, a motor (M) is rotated, and the rotating shaft6connected thereto is rotated, thereby rotating the spin chuck5with the object10a certain number of times.

When the spin chuck5is rotated, the photosensitive solution on the surface of the object10is spread out by a centrifugal force, thereby applying the photosensitive solution over an entire surface of the object10.

After the photosensitive solution is applied over the entire surface of the object10, the applied photosensitive solution is hardened. Then, a predetermined pattern is formed on the surface of the object10through exposure and development using a photo mask or the like.

Although the spin coating method using the spin coater is suitable to coat a small object, such as a wafer with a photosensitive film, it is not suitable to coat a large and heavy substrate, such as a flat panel display device having a glass substrate for a liquid crystal display panel with a photosensitive film.

This is because it gets harder to rotate a substrate at a high speed as the substrate gets larger and heavier. Further, damage to the substrate can occur and much energy is consumed when the substrate is rotated at a high speed.

Also, the spin coating method is disadvantageous in that a considerable amount of photosensitive solution is wasted in comparison with the amount of photosensitive solution used in the photolithography process. In particular, a large amount of photosensitive solution is dispersed outside the spin chuck at the time of high-speed rotation, and is wasted. Substantially, the amount of wasted solution is much larger than the amount of solution used for the coating, and the dispersed photosensitive solution may form particles that contaminate the photoresist following thin film forming processes. The particles can also cause environmental pollution.

BRIEF SUMMARY

To achieve these and other advantages and in accordance with the present invention, as embodied and broadly described herein, there is provided a slit coater comprising: a table on which an object to be processed is mounted; a slit nozzle configured to apply a coating solution onto a surface of the object; a pre-applying unit in which the slit nozzle pre-applies the coating solution; and a coating solution separating unit configured to separate the pre-applied coating solution and to discharge the pre-applied coating solution.

To achieve these and other advantages and in accordance with the present invention, as embodied and broadly described herein there is provided a method for fabricating an LCD substrate using a slit coat. The method includes providing a table on which an object to be processed is mounted and providing a slit nozzle configured to apply a coating solution onto a surface of an LCD substrate. A pre-applying unit is provided that includes a washing container filled with washing solution, a rotating roller disposed in the washing container and configured to receive pre-applied coating solution from the slit nozzle, and first, second, and third washing solution spray nozzles each configured to spray washing solution to one side, the opposite side, and a lower surface, respectively, of the rotating roller. A coating solution separating unit is provided in the pre-applying unit, wherein one end portion of the coating solution separating unit is adjacent to a surface of the rotating roller and configured to separate the coating solution on the surface of the rotating roller from the washing solution and to discharge the separated coating solution. A washing solution supply unit is provided that is configured to supply the washing solution to the pre-applying unit. The slit coater applies the coating solution to the LCD substrate.

In accordance with another aspect of the invention, a method for fabricating an LCD device includes loading a substrate on a table of a slit coater, wherein the slit coater includes a slit nozzle and moving the slit nozzle to a pre-applying unit and pre-applying coating solution. The method further includes separating and discharging the pre-applied coating solution. The slit nozzle is moved to the substrate, and the substrate is coated with the coating solution using the slit nozzle.

DETAILED DESCRIPTION

In general, as mentioned above, a photolithography process is required in the field of semiconductor manufacture and the field of flat panel display device in order to pattern a thin film performing a specific function, for example, an insulation film, a metal thin film, a semiconductor thin film or the like, into a desired form. Here, photosensitive solution such as photoresist, which chemically reacts to light, is used in the photolithography process.

A photosensitive film having a uniform thickness should be formed on a substrate on which a thin film has been formed, so that a defect does not occur during the process. For example, if the photosensitive film has a thickness greater than a designated thickness, a portion of the thin film which should be etched is not etched, and if the photosensitive film has a thickness smaller than the designated thickness, the thin film is excessively etched.

Also, the uniform application of the photosensitive solution has become one of the most important issues as the substrate becomes larger due to an increase in size of the liquid crystal display panel of a liquid crystal display (LCD) device.

In accordance with the invention, a nozzle method in which a certain amount of photosensitive solution is applied by using a slit nozzle is employed in place of a spinner. A coating apparatus employing such a nozzle method is referred to as a spinless coater because a spinner is not used. Alternatively, the term “slit coater” is used because photosensitive solution is applied through a slit. The slit coater supplies the photosensitive solution through a nozzle having a slit shape with a length longer than its width, and applies the photosensitive solution onto a surface of a substrate in a plane form, which makes the slit coater suitable to apply the photosensitive solution to a large LCD device.

FIGS. 2A and 2Bare exemplary views which illustrate a basic concept of a slit coater and the application of the photosensitive solution by the slit coater.

As shown, in accordance with an embodiment of the invention, the slit coater is provided with a slit nozzle22having a narrow and long slit. Photosensitive solution30is supplied through the slit nozzle22, thereby applying the photosensitive solution30on a surface of a substrate100in a plane form.

The slit coater is an apparatus that applies a certain amount of photosensitive solution30onto the substrate100or the like through a bar-shaped long slit nozzle22. The slit coater applies a uniform amount of photosensitive solution30through a fine slit nozzle22, moving from one side of the substrate100toward its other side at a constant speed, thereby forming a uniform photosensitive film on the surface of the substrate100.

Also, because the slit coater can apply the photosensitive solution30only to a desired surface of the substrate100, the coating solution can be used without being wasted as compared to the aforementioned spin coater. In addition, because the slit coater can apply the coating solution in a plane form with a long width, it is suitable for a large substrate or a quadrangular substrate.

For reference element40indicates a table on which the substrate100is mounted, and the arrow indicates a direction in which the photosensitive solution30is applied along a direction that the slit nozzle22moves.

As the slit coater in accordance with the present invention has a pre-applying unit for the pre-applying operation performed before or after the coating solution is applied to an object to be processed such as a glass substrate, a spreading condition is constantly maintained to obtain the best spreading condition. This will now be described with reference to accompanying drawings.

FIG. 3is a schematic front view which is a slit coater having a pre-applying unit in accordance with the embodiment of the present invention.

As shown, the slit coater in accordance with the present embodiment includes a table140on which a substrate100is mounted, a slit nozzle unit120applying a coating solution, such as a photosensitive solution, onto the substrate100, and a driving unit150installed at both ends of the slit nozzle unit120and configured to move the slit nozzle120at a constant speed.

The driving unit150includes a pair of Z-axial driving apparatuses151installed at both ends of the slit nozzle unit120and moving the slit nozzle unit120up and down, and a pair of Y-axial driving apparatuses152moving the slit nozzle unit120back and forth across the table140at a constant speed to uniformly apply the photosensitive solution to a surface of the substrate100.

Here, each Y-axial driving apparatus152may includes a motor (not shown), and a transfer unit (not shown) such as a transfer rail and a guide rail. A non-contact type linear motor can be used as the motor.

An object100such as a glass substrate is mounted onto the table140, and a plurality of pins141for lifting up the substrate100from the table140are installed inside the table140. The pins140are supported by a plate142placed under the table140so as to mount of lift the substrate100onto or from the table140by the vertical movement of the plate142.

The slit nozzle unit120includes a nozzle122located above the substrate100and crossing the substrate100and has the shape of a slit with a length corresponding to a width of the substrate100, and a head121to which the slit nozzle122is mounted.

Although not shown in detail in the drawing, the slit nozzle122includes a nozzle body, an inlet and an outlet, wherein the nozzle body has a receiving space for storing a photosensitive solution therein. The inlet is formed at the nozzle body and the outlet is formed at a surface of the nozzle body, which faces the substrate100. The outlet has the shape of slit with a length longer than its width.

The slit nozzle122applies the photosensitive solution, moving from one side toward the other side of the substrate100by the Y-axial driving apparatuses152, thereby uniformly applying the photosensitive solution on the surface of the substrate100. Also, the photosensitive solution may be applied to the substrate by sliding the substrate100relative to the slit nozzle122which remains in a fixed position.

Although not shown in the drawing, a bubble outlet for removing bubbles within the slit nozzle122can be included at an upper end of the head121of the slit nozzle unit120.

When coating solution is consecutively applied on surfaces of a plurality of substrates by using the slit coater, the concentration of the coating solution within the slit nozzle122is increased during a waiting period between applying processes. If the applying process is performed on the next substrate100in such a state, application defects, such as generating a vertical line on a coating film applied by the highly-concentrated coating solution, or cracks may occur.

Thus, the slit coater in accordance with the present invention additionally includes a pre-applying unit160for the pre-applying, so that the highly-concentrated coating solution within the slit nozzle122is discharged and discarded before or after the application process. Therefore, the defective application can be prevented. This will now be described in detail with reference to accompanying drawings. In the drawing, the case where the pre-applying unit160is installed at a front portion of the table140is taken as an example, but the present invention is not limited thereby and the pre-applying unit160of the present invention may be installed at a rear portion or a side surface of the table140.

FIG. 4is a schematic sectional view of the pre-applying unit160in accordance with an embodiment of the present invention, which is viewed from the side of the pre-applying unit ofFIG. 3.

As shown, the pre-applying unit160in accordance with the present embodiment includes a washing container168filled with a washing solution, a rotating roller165disposed horizontally with respect to the washing container168, wherein a lower portion of the rotating roller165is immersed in the washing solution within the washing container and its upper portion is exposed to approach the slit nozzle122, and washing solution spray nozzles166A˜166C spraying the washing solution toward the surface of the rotating roller165.

Both ends of the cylindrical rotating roller165are rotatably installed at both side walls facing each other and formed vertically on a bottom of the washing container. Although not shown in the drawing, a pulley is mounted at one end of a shaft of the rotating roller165, and the pulley and a rotating shaft of a motor are coupled together by a belt, so that a driving force of the motor is transferred to the rotating roller165through the belt.

The rotating roller165may be formed of metal such as stainless steel, aluminum, titanium, or the like.

As described above, washing solution such as a highly-volatile organic solvent is filled in the washing container168of the pre-applying unit160, and the lower portion of the rotating roller165is immersed in the washing solution.

Also, first and second washing solution spray nozzles166A and166B for spraying the washing solution toward the surface of the rotating roller165are installed at both side walls of the pre-applying unit160. A third washing solution spray nozzle166C is installed within the washing container168under the rotating roller165.

Referring toFIG. 5, the slit nozzle122which pre-applies a certain amount of photosensitive solution to the pre-applying unit160includes a first nozzle body123A, a second nozzle body123B, an inlet125and an outlet126.

The slit nozzle122has a structure in which two nozzle bodies123A and123B are coupled, and a receiving space124for temporarily storing a certain amount of photosensitive solution is formed between the first nozzle body123A and the second nozzle body123B in order to uniformly spray the photosensitive solution pressurized by a pumping unit.

In the illustrated embodiment, the inlet125is formed at an upper portion of the second nozzle body123B and supplies the photosensitive solution to the receiving space124, and the outlet126has a slit shape having a length longer than its width and is formed at a lower portion of the nozzle bodies123A and123B facing the substrate, thereby applying the photosensitive solution to the surface of the substrate100in a plane form.

A gap between the first nozzle body123A and the second nozzle body123B is determined and maintained by a very thin shim127of stainless steel.

Before or after the application process, the pre-applying unit160of the present embodiment can prevent the aforementioned defective application. Referring back toFIG. 4, in one method, the outlet126of the slit nozzle122approaches a surface of the rotating roller165, applies the highly-concentrated photosensitive solution130′ to the pre-applying unit160, and thusly allows the photosensitive solution with certain concentration to remain in the slit nozzle122.

In order to always maintain the best spreading condition, before or after the photosensitive solution is applied onto the glass substrate100, the highly-concentrated photosensitive solution130′ is applied through the outlet126of the slit nozzle122in a state that a uniform interval between the outlet126and the rotating roller165is maintained.

In the illustrated embodiment, the photosensitive solution130′ applied onto the surface of the rotating roller165is diluted by washing solution sprayed from the first washing solution spray nozzle166A, and then is discharged to a photosensitive solution drain (1stdrain) through a photosensitive solution separating unit170formed at a lower end of the left side of the washing container168. One end portion of the photosensitive solution separating unit170is adjacent to the surface of the rotating roller165so as to separate the spread photosensitive solution130′ from the washing solution and discharge the photosensitive solution.

Although the case where the photosensitive solution separating unit170is installed at the lower end of the left side of the washing container168is taken as an example in the drawing, the present invention is not limited thereby, and its installation position is determined by a direction in which the rotating roller165rotates. Specifically, if the rotating roller165rotates counterclockwise, the photosensitive solution separating unit170is installed at the left side as shown inFIG. 4and, if the rotating roller165rotates clockwise, the photosensitive solution separating unit170may be installed at the right side. Also, the photosensitive solution separating unit170may be installed at an upper side or a lower side to separate the photosensitive solution130′ from the washing solution.

Because a certain amount of washing solution always stays in the washing container168of the pre-applying unit160, a part of the rotating roller165is immersed in the washing solution, so that some photosensitive solution130′ which has not been removed by the photosensitive solution separating unit170can be washed.

The third washing solution spray nozzle166C installed at a lower portion of the washing container168and the second washing solution spray nozzle166B installed at a right side of the pre-applying unit160are for diluting and removing some remaining photosensitive solution130′. A first photosensitive solution removing unit167A and a second photosensitive solution removing unit167B installed under and above the second washing solution spray nozzle166B, respectively, are for removing the remaining photosensitive solution130′ and the lastly-sprayed washing solution.

Although the case where the first photosensitive solution removing unit167A is installed at the right side wall of the washing container168is taken as an example in the drawing, the present invention is not limited thereby and the first photosensitive solution removing unit167A may be installed at the right side wall of the pre-applying unit160like the second photosensitive solution removing unit167B. A drain (2nddrain) for discharging extra washing solution within the washing container168is installed between a side wall of the pre-applying unit160and the washing container168where the first photosensitive solution removing unit167A is installed.

The first washing solution spray nozzle166A and the second washing solution spray nozzle166B may be installed at the side wall of the pre-applying unit160by using a screw member (not shown) as a medium, and a bubbling nozzle may be used as the third washing solution spray nozzle166C installed at the washing container168.

In one bubbling nozzle washing method, photosensitive solution130′ attached to the rotating roller165is washed away by spouting a certain amount of washing solution as a playing fountain does and washing away the photosensitive solution130′ using a bubble-like washing solution including gas.

In the pre-applying unit160of the present embodiment, one end portion of the photosensitive solution separating unit170is adjacent to the rotating roller165in the pre-applying unit so as to separate the highly-concentrated photosensitive solution130′ having been spread to the surface of the rotating roller165from the washing solution and discharge the separated photosensitive solution130′. Thus, the highly-concentrated photosensitive solution130′ is not mixed with the washing solution, thereby preventing the washing solution from being polluted by the photosensitive solution. As a result, washing effect of the rotating roller165can be improved when the washing solution is reused, and the number of times the washing solution is reused is increased.

FIG. 6is a schematic plan view of a line system including the pre-applying unit in accordance with the embodiment of the present invention.

As shown, the system for the pre-applying unit160includes a first storage tank190A for storing new clean washing solution, a second storage tank190B for storing used washing solution required to be collected and discharged, a plurality of pumps195A˜195C for transferring the washing solution between the storage tanks190A and190B and the pre-applying unit160, and various control apparatuses including a plurality sensors197A and197B and a plurality of valves180A˜180G. The washing solution can be reused depending upon user's choice.

New washing solution stored in the first storage tank190A is supplied to the second washing solution spray nozzle166B of the pre-applying unit160by the operation of a supply pump195A, and a first filter196A for filtering impurities, and a first valve180A installed between the supply pump195A and the second washing solution spray nozzle166B.

In the illustrated embodiment, a first level sensor197A for measuring the amount of residual washing solution is attached to the first storage tank190A, and sends a signal to a control apparatus (not shown) when detecting a shortage of the washing solution. As the control apparatus sends the signal to a seventh valve180G, the first storage tank receives new washing solution from a washing solution supply unit.

The new washing solution filled in the first storage tank190A through the washing solution supply unit is supplied to the second washing solution spray nozzle166B to be used only for the final washing for the rotating roller165.

Some of washing solution sprayed by the second washing solution spraying nozzle166B is introduced to the drain (2nddrain shown inFIG. 4) and is collected in the second storage tank190B through a drain pump195B. The used washing solution within the washing container168is also stored in the second storage tank190B through the drain pump195B.

The washing solution collected in the second storage tank190B by the drain pump195B may be supplied by a transfer pump195C to the third washing solution spray nozzle166C that washes a lower portion of the rotating roller165or may be reused by being supplied to the first washing solution spray nozzle166A formed at an upper end of the left size so as to dilute the photosensitive solution.

The washing solution having been used to dilute the highly-concentrated photosensitive solution through the first washing solution spray nozzle166A is discharged right after the dilution.

In the illustrated embodiment, a third valve180C and a second filter196B for filtering washing solution being supplied to the drain pump195B are installed between the transfer pump195C and the third washing solution spray nozzle166C. A fourth valve180D is installed between the washing container168and the drain pump195B, and a fifth valve180E is installed between 2nddrain and the drain pump195B.

Also, a second valve180B and a sixth valve180F are installed between the second filter196B and the first washing solution spray nozzle166A. The washing solution may be discharged to a washing solution drain (3rddrain) through the sixth valve180F instead of being reused depending upon user's choice.

The pre-applying unit of the present embodiment can greatly improve washing efficiency by performing separated washing according to the usage of the washing solution, as compared to the related art. Also, only the washing solution used to dilute the photosensitive solution of the washing solution used to wash the rotating roller once is discharged, and only new clean washing solution is always used for the final washing, so that the washing effect can be maximized.

Also, because the washing solution used for the lower portion of the rotating roller is also in a state that the photosensitive solution is filtered, the washing solution can be maintained more cleanly.