JP3871328B2 - COATING APPARATUS, LIQUID LEVEL MANAGEMENT METHOD AND MANAGEMENT APPARATUS, RESIST FILM-SUBSTRATE MANUFACTURING METHOD AND PATTERN FORMING METHOD, AND PHOTOMASK MANUFACTURING METHOD - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is, for example, a coating apparatus for coating a coating liquid such as a photoresist on a substrate such as a photomask blank, a method for manufacturing a substrate with a resist film used for manufacturing a photomask, and a pattern formation using the manufacturing method. The present invention relates to a method, a photomask manufacturing method, a liquid level management method, and a liquid level management apparatus.
[0002]
[Prior art]
As a coating apparatus (coater) for coating a coating liquid such as a photoresist on a substrate such as a photomask blank, a CAP coater described in Patent Document 1 has been known in recent years.
[0003]
In this CAP coater, a nozzle having a capillary gap is submerged in a liquid tank in which a coating solution is stored, and up to the vicinity of the coating surface of the substrate held by the suction disk in a posture in which the coating surface faces downward. A coating film is formed on the coated surface by raising the nozzle extending in the width direction of the substrate, contacting the coating solution through the capillary gap, and then scanning the nozzle over the coated surface. This CAP coater has the advantage that the coating thickness can be set accurately because the coating thickness can be reliably adjusted by the distance between the coated surface and the nozzle tip. Since this CAP coater can form a uniform coating film over a large area, a large-sized photomask or the like used for manufacturing a liquid crystal display device or a liquid crystal display device (for example, a rectangular substrate having a side length of 300 mm or more) In recent years, a gray tone having a semi-transparent region for exposure light composed of a fine pattern for manufacturing a thin film transistor, which is suitable for resist application in the manufacture of a substrate having a remarkable tendency to increase the size of the substrate, and which has a tendency to make the pattern finer. It can be suitably used for resist coating for the production of a mask, another photomask having a high-density pattern, or the like.
[0004]
In this CAP coater, unless the liquid level of the coating liquid stored in the liquid tank is kept constant, there is a problem that the reproducibility of the film thickness when applied is deteriorated, and the liquid level level is strictly controlled. Is indispensable.
[0005]
In the conventional CAP coater, a transparent communication pipe through which the liquid in the liquid tank is guided is provided outside the liquid tank, and an optical liquid level sensor is attached to the outer periphery of the communication pipe. The liquid level of the coating liquid in the liquid tank is monitored by detecting the liquid level. When the liquid level sensor detects that the liquid level has fallen below the reference position and outputs a first detection signal (eg, ON → OFF), the liquid tank is responsive to the first detection signal. When the liquid level sensor detects that the liquid level that has risen due to the replenishment exceeds the reference position and outputs a second detection signal (eg, OFF → ON), the second level is applied. In response to this detection signal, the replenishment of the coating liquid to the liquid tank is stopped, whereby the coating process is performed while managing the liquid level in the liquid tank at the reference position.
[0006]
By the way, this type of liquid level sensor is characterized in that there is a difference between the position where the first detection signal (ON → OFF) is output and the position where the second detection signal (OFF → ON) is output. Have. That is, the position where the liquid level decreases and becomes “ON → OFF” is not exactly the same as the position where the liquid level increases and becomes “OFF → ON”. Has hysteresis. And because of its characteristics, the conventional CAP coater performs replenishment of the liquid after the first detection signal that informs the decrease in the liquid amount is output, and replenishment when the second detection signal is output. By performing the control of stopping, the liquid level of the coating liquid in the liquid tank can be managed uniformly.
[0007]
This will be described in detail with reference to FIG. In the figure, reference numeral 1 denotes a communication pipe connected to a liquid tank (not shown). The liquid level in the communication pipe 1 is equal to the liquid level in the liquid tank. Reference numeral 2 denotes an optical liquid level sensor 2 mounted on the outer periphery of the communication pipe 1. The liquid level sensor 2 is provided with a light projecting unit that emits light toward the inside of the communication pipe 1 and a light receiving unit (both not shown) that receives reflected light, and projects at a certain level. Light is emitted from the light section. When there is no liquid at the level where the light strikes, the difference between the refractive index of the communication tube 1 and the refractive index of the air inside is large, so that the light emitted from the light projecting portion is reflected on the inner surface of the communication tube 1 Then, the liquid level sensor 2 outputs a first detection signal (eg, an OFF signal). In addition, when there is a liquid in the communication tube 1, the difference between the refractive index of the communication tube 1 and the refractive index of the liquid in the communication tube 1 is small, so that the light emitted from the light projecting portion is almost emitted into the liquid. Then, the liquid level sensor outputs a second detection signal (eg, ON signal) without returning to the light receiving unit. Therefore, it can be determined from the signal output from the liquid level sensor 2 whether or not the liquid level in the communication pipe 1 has reached the reference position.
[0008]
For example, it is assumed that the liquid level sensor 2 is outputting an ON signal with the liquid level exceeding the reference position. When the liquid level is lowered from this state, the signal of the liquid level sensor 2 is switched from “ON → OFF” at a certain position as shown in FIG. Therefore, it is possible to detect that the liquid level has fallen below the reference position by this signal switching. Therefore, replenishment of the liquid into the liquid tank is started based on the signal. Then, the liquid level in the communication pipe 1 rises, and the signal of the liquid level sensor 2 is switched from “OFF → ON” at a certain position as shown in FIG. Therefore, it is possible to detect that the liquid level has exceeded the reference position by switching the signal, and the replenishment of the liquid is stopped based on the signal. By doing so, the liquid level can always be kept at the reference position.
[0009]
[Patent Document 1]
JP 2001-62370 A
[Problems to be solved by the invention]
By the way, in the CAP coater described above, the amount of coating liquid used for coating processing on a single substrate in which coating is performed once, that is, the nozzle scans the substrate coating surface at once, is extremely small. For this reason, it may be difficult to reliably detect one decrease within the range of the sensitivity of the liquid level sensor 2. For example, as shown in FIG. 5C, when the liquid level drop due to one coating process is a, the liquid level sensor 2 has only sensitivity for detecting the liquid level drop at the B level. Therefore, the actual drop in the liquid level cannot be detected. Therefore, for example, the liquid level sensor 2 detects a decrease in the liquid level only when the liquid level is lowered by the next coating process, that is, when the liquid level is lowered by 2a in total. Then, the liquid is replenished at that time, and the replenishment is stopped when the reference is reached.
[0011]
As described above, since the amount of the coating liquid consumed in one process is extremely small, as a result, a replenishment operation for making the liquid level constant is performed only after a plurality of coating processes. Absent. Therefore, the first coating process and the second coating process are performed under different conditions of the liquid level, resulting in a problem that the reproducibility of the coating film thickness is deteriorated.
[0012]
In consideration of the above circumstances, the present invention enables a coating apparatus and a resist that can always perform the coating process at the same liquid level, thereby improving the reproducibility of the film thickness. It is an object of the present invention to provide a method for manufacturing a substrate with a film, a pattern forming method, a method for manufacturing a photomask, a liquid level management method and a management device for a coating apparatus.
[0013]
[Means for Solving the Problems]
As means for solving the above-mentioned problem, the first means is:
In a coating apparatus that performs coating by scanning the nozzle on the coated surface while supplying the coating liquid stored in the liquid tank in contact with the coated surface through a nozzle by capillary action,
The liquid level that replenishes the coating liquid to the liquid tank so that the liquid level of the coating liquid stored in the liquid tank becomes the same liquid level at the start of each coating every time one coating process is completed. A coating apparatus comprising a level management device.
[0014]
As a second means, the liquid level management device outputs a first detection signal when the liquid level of the coating liquid stored in the liquid tank falls below a reference position, and exceeds the reference position. A liquid level sensor that outputs a second detection signal, and each time one coating process is completed, by removing at least part of the coating liquid in the liquid tank, the liquid level in the liquid tank Liquid level lowering control means for forcibly lowering the level to a level at which the liquid level sensor outputs the first detection signal;
From the state where the liquid level is lowered by the liquid level lowering control means, the liquid tank is replenished with the coating liquid to raise the liquid level in the liquid tank, and the liquid level sensor is the second. And a liquid level rise control means for stopping the replenishment of the coating liquid when the detection signal is output. The coating apparatus according to the first means.
[0015]
The third means is a method for manufacturing a substrate with a resist film, which includes a resist coating step of coating a resist on a substrate or a thin film formed on the substrate,
The resist coating step is performed by scanning the nozzle on the coated surface while supplying the coating liquid stored in the liquid tank in contact with the coated surface through the nozzle by capillary action, The liquid level in which the liquid level of the coating liquid stored in the liquid tank is replenished to the liquid tank so that the liquid level of the coating liquid stored in the liquid tank becomes the same level at the start of each time coating is completed. A method of manufacturing a substrate with a resist film, wherein a resist is applied while managing a liquid level in the liquid tank at the start of application by a level management method.
[0016]
As a fourth means, the liquid level management device outputs a first detection signal when the liquid level of the coating liquid stored in the liquid tank falls below a reference position, and exceeds the reference position. When a liquid level sensor that outputs a second detection signal is used, each time one coating process is completed, at least part of the coating liquid in the liquid tank is withdrawn, whereby the liquid level in the liquid tank is The liquid level sensor is forcibly lowered to a level at which the first detection signal is output, and from this state, the liquid tank is replenished with a coating liquid to raise the liquid level in the liquid tank. The method for producing a substrate with a resist film according to a third means, wherein the replenishment of the coating liquid is stopped when the surface sensor outputs the second detection signal.
[0017]
The fifth means is a resist film forming step of forming a resist film by applying a resist coating process to the substrate or a thin film formed on the substrate, and exposing a desired pattern to the resist film formed in the resist film forming step. And a resist pattern forming process for forming a resist pattern by performing a developing process, and a resist pattern formed in this resist pattern forming process is used as a mask to perform an etching process, and a desired pattern is formed on the substrate or a thin film formed on the substrate. And a pattern forming step for forming
In the pattern forming method, the resist film forming step is performed by using the method for manufacturing a substrate with a resist film described in the fourth means.
[0018]
The sixth means is a resist film forming step of forming a resist film by applying a resist coating process to the light shielding film formed on the substrate, and exposing and developing a desired pattern on the resist film formed in the resist film forming step. A resist pattern forming process for forming a resist pattern by performing a process, and an etching process is performed using the resist pattern formed in the resist pattern forming process as a mask to form a desired pattern on the light-shielding film formed on the substrate A pattern forming process,
A method for producing a photomask, wherein the resist film forming step is performed using the method for producing a substrate with a resist film described in the fourth means.
[0019]
The seventh means outputs the first detection signal when the liquid level falls below the reference position and the second detection when the liquid level exceeds the reference position. In a coating device that performs a coating process while monitoring a liquid level sensor that outputs a signal and managing the liquid level in the liquid tank at a constant level,
Every time one coating process is completed, at least a part of the coating liquid in the liquid tank is removed to forcibly reduce the liquid level in the liquid tank to a level at which the liquid level sensor outputs the first detection signal. From this state, the coating liquid is replenished in the liquid tank to increase the liquid level in the liquid tank. When the liquid level sensor outputs the second detection signal, the coating liquid is replenished. The liquid level control method for a coating apparatus is characterized by stopping and maintaining the liquid level at a reference position.
[0020]
The eighth means outputs the first detection signal when the liquid level falls below the reference position and the second detection when the liquid level exceeds the reference position. In a coating device that performs a coating process while monitoring a liquid level sensor that outputs a signal and managing the liquid level in the liquid tank at a constant level,
Every time one coating process is completed, at least a part of the coating liquid in the liquid tank is removed to forcibly reduce the liquid level in the liquid tank to a level at which the liquid level sensor outputs the first detection signal. The liquid level lowering control means for lowering and the liquid level lowering by the liquid level lowering control means, the liquid level in the liquid tank is increased by replenishing the coating liquid in the liquid tank. And a liquid level rise control means for stopping the replenishment of the coating liquid when the liquid level sensor outputs a second detection signal.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory diagram of basic elements for carrying out the liquid level management method of the embodiment, FIG. 2 is an explanatory diagram of the management method of the embodiment, and FIG. 3 is a specific example of a coating apparatus including the management device of the embodiment. FIG. 4 is a side sectional view showing the configuration, and is a view seen from the direction of arrow IV in FIG.
[0022]
FIG. 1 shows the relationship among the liquid tank, the communication pipe, and the liquid level sensor. A communication pipe 1 through which the coating liquid in the liquid tank 3 is guided is provided outside the liquid tank 3 for storing the coating liquid, and an optical liquid level sensor 2 is attached to the outer periphery of the communication pipe 1. The liquid level sensor 2 has a light projecting unit that emits light toward the inside of the communication tube 1 and a light receiving unit (both not shown) that receives reflected light, and has the same role as described in the conventional example. Fulfill. That is, a first detection signal (eg, an OFF signal) is output when the liquid level falls below the reference position, and a second detection signal (eg, an ON signal) is output when the liquid level exceeds the reference position. The liquid tank 3 is provided with a liquid supply means 4 that supplies the coating liquid into the liquid tank 3 and a liquid discharge means 5 that discharges the coating liquid to the outside of the liquid tank 1. It has been.
[0023]
A method of managing the liquid level at a constant level will be described with reference to FIG. Here, illustration of the liquid tank is omitted. In the figure, a dotted line A indicates a level at which the liquid level sensor 2 outputs a first detection signal (eg, an OFF signal) as the liquid level drops, and a dotted line B indicates a level where the liquid level sensor 2 increases as the liquid level increases. 2 indicates a level at which a detection signal (eg, ON signal) is output.
[0024]
In the management method of the present embodiment, when the amount of liquid is reduced as shown in (a) after one coating process, the coating liquid in the liquid tank 3 is removed from the liquid discharging means 5 regardless of the liquid level. As shown in (b), the liquid level in the liquid tank 3 is forced to a level at which the liquid level sensor 2 reliably outputs the first detection signal (ON → OFF) Down. Next, from this state, the liquid supply means 4 is controlled instead of the liquid discharge means 4 to replenish the coating liquid in the liquid tank 3 and increase the liquid level in the liquid tank 3 ( As shown in c), the replenishment of the coating liquid is stopped when the liquid level sensor 2 outputs the second detection signal (OFF → ON). In this way, the liquid level is kept at the reference position by repeating the extraction and replenishment of the coating liquid for each coating process.
[0025]
This sequence operation can be automatically performed by the control means. In that case, the control means controls the liquid discharge means 5 and removes at least a part of the coating liquid in the liquid tank 3 every time one coating process is completed, thereby adjusting the liquid level in the liquid tank 3. The liquid level lowering control means forcibly lowering the liquid level sensor 2 to the level at which the first detection signal is output, and the liquid supply means 4 from the state where the liquid level has been lowered by the liquid level lowering control means. By controlling, the application liquid is replenished in the liquid tank 3, the liquid level in the liquid tank 3 is increased, and the application liquid is replenished when the liquid level sensor 2 outputs the second detection signal. The liquid level rise control means for stopping is included.
[0026]
Next, a coating apparatus incorporating the management apparatus of the embodiment will be described with reference to FIGS. The coating apparatus 20 is, for example, for applying a resist 22 as a coating liquid on a light shielding film of a photomask blank (substrate with a light shielding film) 21 which is a material of a photomask for manufacturing a liquid crystal display device. It is installed in a clean room where a flow is formed. The photomask blank 21 is arranged with the application surface facing downward by being adsorbed by the adsorbing plate 23, and is scanned in a horizontal plane relative to the nozzle 25 of the application device 20.
[0027]
The base plate 26 of the coating apparatus 20 is provided with a support frame 28 that is moved up and down by a first lifting mechanism 27, and a liquid tank 29 for storing a resist is fixed to the support frame 28. The support frame 28 is provided with a support rod 31 that can be moved up and down by the second lifting mechanism 30, and a nozzle 25 having a capillary gap 25 a is fixed to the upper end of the support rod 31. The liquid tank 29 has a box shape having a slit 32 at the upper end surface. The nozzle 25 is accommodated in the liquid tank 29, and the tip of the nozzle 25 is exposed from the slit 32. The resist is guided to the tip of the nozzle 25 through the capillary gap 25a.
[0028]
The support rod 31 that supports the nozzle 25 in the liquid tank 29 is inserted into the liquid tank 29 through a through hole 33 formed in the bottom wall of the liquid tank 29, and a resist from the through hole 33 is inserted in the insertion portion. A bellows-like seal member 34 for preventing the leakage of 22 is provided.
[0029]
As shown in FIG. 4, a resist supply pipe 41 and a resist discharge pipe 42 are connected to the liquid tank 29. The resist supply pipe 41 is connected to an opening 43 formed on the side wall of the liquid tank 29, and the resist discharge pipe 42 is connected to an opening 44 formed on the bottom wall of the liquid tank 29. The resist supply pipe 41 supplies the resist 22 stored in the resist tank 45 to the liquid tank 29 through the filter 47 by the pump 46. The resist discharge pipe 42 naturally discharges the resist 22 in the liquid tank 29 by opening the electromagnetic valve 48 and returns it to the resist tank 45. The drive motor 49 and the solenoid valve 48 of the pump 46 are driven and controlled by the control device 50.
[0030]
A communication pipe 52 for measuring the liquid level in the liquid tank 29 is provided outside the liquid tank 29. The lower end of the communication pipe 52 is connected to an opening 53 formed on the side wall of the liquid tank 29, so that the liquid level of the resist guided into the communication pipe 52 is the liquid level of the resist in the liquid tank 29. To match. A liquid level sensor 55 for measuring whether or not the liquid level is at the reference position is mounted on the outer periphery of the communication pipe 52. The signal of the liquid level sensor 55 is input to the control device 50, and the control device 50 controls the electromagnetic valve 48 and the pump motor 49 based on the signal of the liquid level sensor 55, thereby implementing the management method described above. Then, the liquid level of the resist 22 in the liquid tank 29 is managed to be constant.
[0031]
That is, every time one coating process by the coating apparatus is completed, the control device 50 first opens the electromagnetic valve 48 and discharges the resist 22 in the liquid tank 29 by an appropriate amount. By performing this operation, when the liquid level sensor 55 detects a decrease in the liquid level above a predetermined level (the state shown in FIG. 2B), the control device 50 closes the electromagnetic valve 48 and turns on the pump motor 49. The liquid tank 29 is driven and the resist 22 is replenished. Then, when the liquid level sensor 52 detects that the liquid level that has risen due to the replenishment has reached the reference position (state shown in FIG. 2C), the replenishment of the resist 22 is stopped. By doing in this way, the coating operation can be performed under exactly the same liquid level condition for each process, and the reproducibility of the resist film thickness can be improved.
[0032]
In this coating device 20, the control device 50, the resist supply pipe 41, the pump 46, the motor 49, etc. correspond to the liquid level rise control means, and the control device 50, the resist discharge pipe 42, the electromagnetic valve 48, etc. This corresponds to the surface level lowering control means.
[0033]
Next, a method for manufacturing a photomask using the above-described liquid level management method will be described.
First, a photomask blank in which a light shielding film containing a chromium-based material is formed on a substrate (for example, 390 × 610 mm) is prepared. A resist was applied onto the photomask blank using the coating apparatus described with reference to FIGS. 3 and 4 to form a resist film having a thickness of, for example, 1 μm. When forming this resist film, as described above, every time one coating process (one photomask blank coating process) is completed, the liquid level in the liquid tank is used. The resist solution is replenished so that the surface level is the same as that at the start of resist application to the photomask blank. Thus, although the resist application to the photomask blank was performed a plurality of times, a resist film having an equivalent thickness could always be formed for any photomask blank.
[0034]
A pattern is drawn on the resist film formed on the photomask blank using a laser drawing apparatus, and the resist is developed to form a resist pattern. The light shielding film was etched using the formed resist pattern as a mask, and the remaining resist pattern was peeled off to manufacture a photomask. As a result, a photomask having a good dimensional reproducibility of the light shielding film pattern could be obtained between the photomasks.
[0035]
On the other hand, a resist film using a conventional liquid level management method, that is, a management method in which the liquid level sensor detects that the liquid level of the coating liquid has fallen below the reference position in the coating process of the resist liquid and replenishes the coating liquid. In the first application, the sensor does not detect the change in the liquid level, and the sensor detects the change in the liquid level in the middle of the fifth application. Replenishment was performed. As a result, the film thickness of the resist film formed on each photomask blank varied in the five times of application.
[0036]
【The invention's effect】
As described above, according to the present invention, since the liquid level can be managed with good reproducibility, the reproducibility of the film thickness can also be improved.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of basic elements for carrying out a liquid level management method according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram of a management method according to the embodiment of this invention.
FIG. 3 is a side sectional view showing a specific configuration of a coating apparatus including a management apparatus according to an embodiment of the present invention.
4 is a view as seen from the direction of arrow IV in FIG. 3;
FIG. 5 is an explanatory diagram of a conventional liquid level management method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Communication pipe 2 Liquid level sensor 3 Liquid tank 4 Liquid supply means 5 Liquid discharge means 20 Coating apparatus 22 Resist (coating liquid)
25 Nozzle 29 Liquid tank 50 Control device 52 Communication pipe 55 Liquid level sensor

Claims (6)

In a coating apparatus that performs coating by relatively scanning the nozzle on the surface to be coated while supplying the coating liquid stored in the liquid tank in contact with the surface to be coated through a nozzle by capillary action,
The coating apparatus includes a liquid level management device that causes the liquid level of the coating liquid stored in the liquid tank to be the same liquid level at the start of each application,
The liquid level management device outputs a first detection signal when the liquid level of the coating liquid stored in the liquid tank falls below a reference position, and outputs a second detection signal when the liquid level exceeds the reference position. The liquid level in the liquid tank is reduced by removing at least a part of the coating liquid in the liquid tank every time one coating process is completed. Liquid level lowering control means for forcibly lowering to a level at which the sensor outputs the first detection signal;
From the state where the liquid level is lowered by the liquid level lowering control means, the liquid tank is replenished with the coating liquid to raise the liquid level in the liquid tank, and the liquid level sensor is the second. And a liquid level rise control means for stopping the replenishment of the coating liquid when the detection signal is output. A method for manufacturing a substrate with a resist film, comprising a resist coating step of applying a resist onto a substrate or a thin film formed on the substrate,
In the resist coating step, the coating liquid stored in the liquid tank is applied by causing the nozzle to relatively scan on the surface to be coated while supplying the coating liquid in contact with the surface to be coated through a nozzle by capillary action. Do
Liquid level management is performed so that the liquid level of the coating liquid stored in the liquid tank is the same liquid level at the start of each application,
The liquid level management method outputs a first detection signal when the liquid level of the coating liquid stored in the liquid tank falls below a reference position, and outputs a second detection signal when the liquid level exceeds the reference position. The liquid level sensor outputs the liquid level in the liquid tank by removing at least part of the coating liquid in the liquid tank every time one coating process is completed. The detection signal is forcibly lowered to the level at which the detection signal is output, and from this state, the liquid tank is replenished with the coating liquid to raise the liquid level in the liquid tank, and the liquid level sensor is A method of manufacturing a substrate with a resist film, which is a method of stopping replenishment of a coating solution when a detection signal is output. A resist film forming step of forming a resist film by applying a resist coating process to the substrate or a thin film formed on the substrate, and exposing and developing a desired pattern on the resist film formed in the resist film forming step. A resist pattern forming step for forming a resist pattern, and an etching step for performing an etching process using the resist pattern formed in the resist pattern forming step as a mask to form a desired pattern on the substrate or a thin film formed on the substrate; Have
The pattern formation method characterized by performing the said resist film formation process using the manufacturing method of the board | substrate with a resist film of Claim 2 . A resist film forming process for forming a resist film by applying a resist coating process to the light shielding film formed on the substrate, and a resist pattern formed by subjecting the resist film formed in the resist film forming process to exposure and development of a desired pattern And a resist pattern forming step for forming a resist pattern and an etching step for performing a etching process using the resist pattern formed in the resist pattern forming step as a mask to form a desired pattern on the light-shielding film formed on the substrate. ,
A method for producing a photomask, wherein the resist film forming step is performed using the method for producing a substrate with a resist film according to claim 2 . A liquid level that outputs a first detection signal when the liquid level falls below the reference position and outputs a second detection signal when the liquid level exceeds the reference position. In a coating device that performs coating while monitoring with a sensor and managing the liquid level in the liquid tank at a constant level,
Every time one coating process is completed, at least a part of the coating liquid in the liquid tank is removed to forcibly reduce the liquid level in the liquid tank to a level at which the liquid level sensor outputs the first detection signal. From this state, the coating liquid is replenished in the liquid tank to increase the liquid level in the liquid tank. When the liquid level sensor outputs the second detection signal, the coating liquid is replenished. A liquid level management method for a coating apparatus, characterized by stopping and maintaining the liquid level at a reference position. A liquid level that outputs a first detection signal when the liquid level falls below the reference position and outputs a second detection signal when the liquid level exceeds the reference position. In a coating device that performs coating while monitoring with a sensor and managing the liquid level in the liquid tank at a constant level,
Every time one coating process is completed, at least a part of the coating liquid in the liquid tank is removed to forcibly reduce the liquid level in the liquid tank to a level at which the liquid level sensor outputs the first detection signal. The liquid level lowering control means for lowering and the liquid level lowering by the liquid level lowering control means, the liquid level in the liquid tank is increased by replenishing the coating liquid in the liquid tank. And a liquid level rise control means for stopping the replenishment of the coating liquid when the liquid level sensor outputs the second detection signal.

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