JPH11285666A - Liquid material coating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform uniform coating by atomizing a liquid material and electrostatically adsorbing the particles on a substrate to which static electricity is imparted. SOLUTION: A liquid material 7 such as a resist stored in a liquid material vessel 9 is atomized by using a piezoelectric vibrator 11. An atomizing means except the piezoelectric vibrator 11 can be used. A gate valve 13 is provided on the upper part of the liquid material vessel 9 and the atomized liquid material 7 is supplied to a coating treating vessel 3 by opening the gate valve 13. An ionizer 15 is arranged between the gate valve 13 and a large sized glass substrate 1 to electrify the atomized liquid material 7 into a reverse polarity to an electrostatic chuck 5. On the other hand, a DC power source 17 is connected to the electrostatic chuck 5 to impress a high voltage. As a result, the atomized liquid material 7 impressed into the reverse polarity is electrostatically adsorbed to the surface of the large sized substrate 1. As a result, the uniform coating is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for applying a liquid material. More specifically, the present invention relates to a method for applying a liquid material that does not cause unevenness in the coating thickness.

[0002]

2. Description of the Related Art A spin coat method, a wire coat method, a roller coat method and the like are used for applying a resist or SOG to a large substrate represented by a liquid crystal substrate.

FIG. 2 is a schematic diagram showing the state of implementation of the spin coating method. As shown, a large glass substrate 1
And carried by the vacuum chuck 23. A liquid material such as a resist is dropped from the supply pipe 25 into the substrate at a predetermined flow rate. Thereafter, the chuck is rotated at a predetermined rotation speed (for example,
(2000 to 6000 rpm) for a predetermined time, and the resist is uniformly spread by centrifugal force. In this method, when the coating film thickness must be maintained within ± 5%, ± 20%
A rotation accuracy of 50 rpm is required. When the shaft 5 of the vacuum chuck 3 is directly connected to a motor (not shown) and rotated (direct drive method), the rotation accuracy can be controlled as desired, but an abnormal load on the shaft 5 is directly applied to the rotary motor. There is a drawback that becomes a load of.

On the other hand, in the case of a mechanism for transmitting the rotation of the motor by a belt or an O-ring (belt drive method), an abnormal load on the motor can be reduced, but there is a disadvantage that it is difficult to obtain a desired rotation accuracy. In the case of the spin coating method, a relatively uniform coating film thickness can be obtained when the substrate is circular, but when the substrate is rectangular, the coating film thickness unevenness occurs at the corner of the substrate and cannot be applied to production. .

It is also known that when a substrate is large, the substrate is easily damaged by centrifugal force in the spin coating method. In addition, during the rotation, the resist scattered from above the substrate may bounce around the coating device and adhere again to the substrate. In order to prevent this, a bounce-prevention wall must be provided around the substrate, and the structure of this prevention wall requires careful attention.

FIG. 3 is a schematic diagram showing the state of implementation of the wire coating method or the roller coating method. As shown in the figure, the large glass substrate 1 is loaded and held by the vacuum chuck 33. A liquid material such as a resist is dropped from the supply pipe 35 into the substrate at a predetermined flow rate. After that, the resist is made uniform by a wire or roller 35 positioned in front of the liquid material supply pipe. In the case of this method, unevenness in the coating film thickness occurs, and it has not yet reached a practical level.

Therefore, at present, there is no applicator applicable to production. In addition, as the size of the substrate increases, the amount of resist dropped increases, and most of the resist is discharged during flattening. Therefore, there is a concern that the running cost may increase due to a decrease in yield.

[0008]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for applying a liquid material which can uniformly apply a liquid material to a substrate surface.

[0009]

The object of the present invention is to atomize a liquid material, electrostatically apply particles of the liquid material to the substrate surface by static electricity applied to the substrate, and uniformly apply the liquid material to the substrate surface. Is solved by

[0010]

According to the method of the present invention, a liquid material such as a resist is atomized by a vacuum or a vibrator, etc.
The liquid particles can be electrostatically attracted to the surface of the substrate and applied by a high voltage applied to the chuck of the substrate. Since the electrostatic attraction force is generated relatively uniformly, the coating thickness unevenness is small,
Since the loss (amount of wear) of the resist and the like is small, the method is excellent in running cost.

FIG. 1 is a schematic sectional view of an example of a coating apparatus used to carry out the liquid material coating method of the present invention. The large glass substrate 1 is carried into the coating tank 3, and the substrate is held by the electrostatic chuck 5. A liquid material 7 such as a resist is stored in a liquid material tank 9, and the liquid material 7 is atomized by using a vibrator 11. Atomizing means (for example, vacuum) other than the vibrator can of course be used. Such atomizing means are well known to those skilled in the art. A vacuum and a vibrator can be used together. The gate valve 13 provided on the upper part of the liquid material tank 9 is opened, and the mist of the liquid material is supplied into the coating tank 3. Gate valve 13 and large glass substrate 1
The fog is charged to the polarity opposite to that of the electrostatic chuck 5 by the ionizer 15 located between the fog and the ionizer. Any known and commonly used ionizer can be used in the present invention. Such ionizers are well-known to those skilled in the art.

The electrostatic chuck 5 has a direct current (DC) power supply 17.
Is connected. Electrostatic chuck 5 by DC power supply 17
A high voltage is applied to the mist to electrostatically attract the fog to the surface of the large substrate, and the liquid material is uniformly applied. The applied voltage is not particularly limited, but is generally in the range of 1 kV to 10 kV. After the electrostatic adsorption for a predetermined time, the gate valve 13 is closed, the application of high voltage is stopped, and the large coated substrate is carried out of the coating tank 3. The mist of the liquid material that does not contribute to the coating is evacuated via an exhaust pipe 19 provided above the coating tank 3.

After supplying the mist of the liquid material, the exhaust pipe 1
9. Close the air valves 21 and 21 arranged in the middle of 9,
After supplying for a predetermined time, when the gate valve 13 is closed and a high voltage is applied in a state where the mist of the liquid material is filled in the coating tank 3, the consumption amount of the liquid material for application can be reduced.

As the electrostatic chuck 5, an electrostatic chuck with a built-in heater can be used. If this electrostatic chuck with a built-in heater is used, the resist can be baked simultaneously with the application, and the time for forming the resist film can be greatly reduced.

As one example of a coating method of a paint, an electrostatic coating method has been conventionally known. The electrostatic coating method uses ion current generated between high-voltage electrostatic voltage poles to suspend paint particles between the two poles, imparts ionic charges to the paint, and applies the particles to the product by the action of an electrostatic field. A high voltage DC negative voltage is applied to a thin wire frame, and 100
This produces a voltage of kV. When the paint is sprayed in this state, the particles receive negative ions and are adsorbed on the article. Benefits include less than 10% paint loss, no air bubbles on the painted surface, uniformity, less than 5 kW of power, and space saving.

The method for applying a liquid material according to the present invention has the following advantages. (1) Completely closed, so that the coating yield is remarkably high; (2) Since the charged portion of the particles is divided, Excellent in controllability of film thickness. In other words, until the coated particles are filled, the ionizer charges it to the same polarity to suppress adhesion, and charges it to the opposite polarity at the same time as filling, thereby improving the controllability of the film thickness by increasing the accuracy of time management of the adhesion. (3) Since no air is used for atomizing the liquid material, the particle velocity is low, the coating yield is improved, and foreign substances are not easily attached. (4) The electric resistance of the coating material is low. Fine particles can be generated without being affected; (5) The electrostatic chuck itself does not basically consume power (although there is a slight leak current, it requires only about 1.4 watts of power), and The ionizer also consumes very little power at about 30 watts, so the power cost is remarkably low. (6) By dividing the charged portion of the particles, it is unlikely that an ignition accident due to the spark of discharge will occur and the safety is high. Have .

[0017]

As described above, according to the present invention,
A liquid material such as a resist is atomized by a vacuum or a vibrator or the like, and the liquid particles can be electrostatically adsorbed on the substrate surface by a high voltage applied to a chuck of the substrate and applied. Since the electrostatic attraction force is generated relatively uniformly, the coating thickness unevenness is small, and the loss (amount of wear) of the resist and the like is small.
This is an excellent method for running costs.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an example of a coating apparatus used to carry out a liquid material coating method of the present invention.

FIG. 2 is a schematic diagram showing an implementation state of a conventional spin coating method.

FIG. 3 is a schematic view showing an implementation state of a conventional wire coating method or a roller coating method.

[Explanation of symbols]

 Reference Signs List 1 substrate 3 coating treatment tank 5 electrostatic chuck 7 liquid material 9 liquid material tank 11 vibrator 13 gate valve 15 ionizer 17 DC power supply 19 exhaust pipe 21 air valve 23, 33 vacuum chuck 35 wire or roller

Claims (4)

[Claims] 1. A liquid material applying method, wherein a liquid material is atomized, particles of the liquid material are electrostatically attracted to the substrate surface by static electricity applied to the substrate, and the liquid material is uniformly applied to the substrate surface. . 2. The method according to claim 1, wherein the liquid material is atomized using at least one atomizing means selected from the group consisting of a vacuum and a vibrator. 3. The method according to claim 1, wherein the atomized liquid material particles are charged to a polarity opposite to the polarity of the substrate by an ionizer. 4. The method according to claim 1, wherein the liquid material is a resist, SOG or a material for forming a surface protective film.