KR20090124757A - Level measuring device for chemical tank - Google Patents

Abstract

A level measuring device for a chemical liquid tank is provided. Level measuring apparatus for a chemical liquid tank according to an embodiment of the present invention, the tube tube is connected in parallel with the chemical liquid tank for storing the chemical liquid, a portion of the chemical liquid is introduced in accordance with the level of the chemical liquid stored in the chemical liquid tank, and the tube tube A pair of level detectors and level detectors, which are continuously installed side by side in the longitudinal direction of the tube tube, measure the level of the chemical liquid introduced into the tube tube to measure the level of the chemical liquid inside the chemical tank. And a level indicator for displaying the level of the chemical liquid inside the chemical liquid tank measured from the level.

Description

Level measuring apparatus for chemical tank

The present invention relates to a level measuring device for a chemical liquid tank, and more particularly, to a level measuring device for a non-contact chemical liquid tank that is simple in structure and capable of accurate level measurement.

Recently, liquid crystal display (LCD) devices, plasma display panel (PDP) devices, and the like have been rapidly replacing conventional CRTs as display devices for displaying images. These use substrates commonly referred to as flat panel displays (FPDs).

In order to manufacture a flat panel display, many processes such as a substrate fabrication process, a cell fabrication process, and a module fabrication process must be performed. In particular, in the substrate fabrication process, in order to form various patterns on the substrate, photolithography techniques are generally applied, starting with a cleaning process.

Photolithography technology includes the steps of applying a photoresist, a photoresist, to a film formed on a substrate, drying the photoresist to volatilize a solvent of the photoresist, and relatively low temperature. Soft baking the photoresist, exposing the photoresist film according to a pattern formed on the photomask after covering the photoresist with a photo mask, and developing the exposed photoresist film. And hard baking the developed photoresist at a relatively high temperature, and patterning the film quality exposed between the photoresist films.

Various liquid chemicals or pure water (DI water) are frequently used in the manufacturing process of such a flat panel display device. Various liquid chemicals include, for example, acidic solutions such as hydrofluoric acid, sulfuric acid, nitric acid, phosphoric acid, and the like, alkaline solutions containing potassium hydroxide, sodium hydroxide, ammonium, and the like, and chemicals used in cleaning liquids.

Accordingly, the substrate processing apparatus is provided with a chemical liquid supply device for supplying and circulating various liquid chemicals or DI water (hereinafter referred to as chemical liquid). The chemical liquid supply device has a structure in which a chemical liquid is supplied to a substrate processing unit from a chemical liquid tank storing a chemical liquid using a pump or the like, and the used chemical liquid is recovered to the chemical liquid tank again. The chemical liquid tank is mostly located at the bottom of the facility frame of the substrate processing apparatus.

In general, various types of sensors may be used to measure the level of chemicals stored in the chemical tank. The method of measuring the level of water using the sensor may be performed according to the contact with the measurement object. It can be divided into measuring method and non-contact measuring method.

For example, a level sensor can be used as a contact measurement method. In this case, a specific chemical liquid having a high toxicity or a high corrosiveness may be corroded and the impurities may be absorbed into the chemical liquid. Purity is lowered, and harmful components of the chemical liquid are exposed, which may cause stability problems.

Therefore, in the case of certain toxic or corrosive chemicals, a non-contact measuring method capable of measuring the level of the liquid level without contact with the chemicals should be used. As a non-contact measuring method, for example, a capacitive sensor may be used, and a plurality of capacitive sensors are usually installed at appropriate positions on a tube tube connecting upper and lower portions of a chemical tank to detect the presence or absence of a chemical liquid for each position. Level tree method can be used. In this way, however, it is difficult to accurately measure the level of the chemical liquid inside the chemical tank.

In addition, as a non-contact measuring method, a load cell method may be used. In the load cell method, the weight of the chemical liquid tank is measured by using an electronic scale including a load cell, which is a weighing element, and then this value is converted to calculate the flow rate in the chemical liquid tank. However, in the case of the load cell system, the piping configuration at the bottom of the chemical tank becomes complicated.

Accordingly, there is a need for a non-contact level measurement device having a simple structure and capable of accurate level measurement.

The present invention has been devised to improve the above problems, and the technical problem to be achieved by the present invention is to provide a level sensing unit of the capacitive method by measuring the level of the chemical liquid level is simple, stable and accurate water level measurement It is possible to provide a level measuring device for a non-contact chemical liquid tank.

Technical problem of the present invention is not limited to those mentioned above, another technical problem that is not mentioned will be clearly understood by those skilled in the art from the following description.

In order to achieve the above object, the level measuring device for a chemical liquid tank according to an embodiment of the present invention, connected in parallel with the chemical liquid tank for storing the chemical liquid, according to the level of the chemical liquid stored inside the chemical liquid tank of A tube tube into which a part flows in, and is continuously installed side by side in the longitudinal direction of the tube tube on the outer surface of the tube tube, the water level level of the chemical liquid inside the chemical tank by measuring the water level level of the chemical liquid introduced into the tube tube And a level display unit configured to display a level level of the chemical liquid inside the chemical liquid tank measured by the level sensor.

In order to achieve the above object, the level measuring device for a chemical liquid tank according to another embodiment of the present invention, the side surface of the chemical liquid tank for storing the chemical liquid continuously installed side by side in the longitudinal direction of the chemical liquid tank, the chemical liquid tank inside And a pair of level detectors for measuring the water level of the chemical liquid, and a level indicator for displaying the level of the chemical liquid measured from the level sensor.

According to the level measuring device for the chemical liquid tank of the present invention as described above has one or more of the following effects.

Firstly, the capacitive level sensor installed in the longitudinal direction of the tube tube can be used to obtain detailed measurement data according to the level of the chemical liquid. have.

Second, there is an advantage that a pair is installed so as to face the level sensing unit around the tube tube to increase the accuracy of the level detection of the chemical liquid.

Third, since the level of the chemical liquid can be measured in a non-contact manner from the outside of the chemical liquid tank, it is not in direct contact with the chemical liquid can increase the durability and stability of the level measuring device, and can facilitate maintenance of the level measuring device.

Fourth, there is an advantage that can simplify the configuration around the chemical tank to increase space utilization and reduce costs.

The effects of the present invention are not limited to the above-mentioned effects, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various different forms, and only the embodiments make the disclosure of the present invention complete, and the general knowledge in the art to which the present invention belongs. It is provided to fully inform the person having the scope of the invention, which is defined only by the scope of the claims. Like reference numerals refer to like elements throughout.

Thus, in some embodiments, well known process steps, well known structures and well known techniques are not described in detail in order to avoid obscuring the present invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In this specification, the singular also includes the plural unless specifically stated otherwise in the phrase. As used herein, including and / or comprising includes the presence or addition of one or more other components, steps, operations and / or elements other than the components, steps, operations and / or elements mentioned. Use in the sense that does not exclude. And “and / or” includes each and all combinations of one or more of the items mentioned.

In addition, the embodiments described herein will be described with reference to cross-sectional and / or schematic views, which are ideal illustrations of the invention. Accordingly, shapes of the exemplary views may be modified by manufacturing techniques and / or tolerances. Accordingly, the embodiments of the present invention are not limited to the specific forms shown, but also include variations in forms generated by the manufacturing process. In addition, each component in each drawing shown in the present invention may be shown to be somewhat enlarged or reduced in view of the convenience of description. Like reference numerals refer to like elements throughout.

Hereinafter, the present invention will be described with reference to the drawings for explaining a level measuring device for a chemical liquid tank according to embodiments of the present invention.

1 is a view schematically showing a structure of a general substrate processing apparatus.

Referring to FIG. 1, the substrate processing apparatus 1 may largely include a substrate processing unit 10, a chemical liquid tank 20, and a chemical liquid supply pump 30. Here, the substrate processing apparatus 1 may mean various kinds of apparatuses for treating the substrate G by using various chemical liquids (including pure water) such as a photosensitive liquid coating apparatus and a cleaning apparatus.

Looking at the substrate processing unit 10 as a center, the substrate processing unit 10 includes a spray nozzle 11 for injecting a chemical liquid toward the substrate G, a substrate transfer unit 12 and a spray for transporting the substrate G in one direction. It may be composed of a treatment tank 13 for collecting the collected chemical liquid. The substrate processing unit 10 includes a photoresist coating process, an exposure process, a developing process, an etching process, a stripping process, and a cleaning process in the manufacturing process of the flat panel display device. It may mean a space that proceeds. Therefore, in the substrate processing unit 10, various processes for the substrate G may be performed using various chemical liquids supplied from the chemical liquid supply device. At this time, the type, flow rate, etc. of the chemical liquid supplied to the substrate processing unit 10 may be adjusted through the chemical liquid supply device. Here, the chemical liquid supply device means a configuration including a treatment tank 13, a chemical liquid tank 20, a chemical liquid supply pump 30, and a plurality of pipes 41, 42, and 43 in FIG. 1.

The injection nozzle 11 may be in the form of a spray nozzle in which a plurality of nozzles are arranged at regular intervals to inject the chemical liquid, respectively, as shown in FIG. 1, or may be in the form of a slit nozzle that discharges the chemical liquid through a long discharge port. .

The substrate transfer unit 12 includes a plurality of transfer shafts disposed at regular intervals perpendicular to the transfer direction of the substrate G, and a plurality of rollers for supporting and transferring the substrate G to each transfer shaft. Can be configured. The substrate transfer unit 12 may transfer the rotational force of a driving device such as a motor to each transfer shaft through a power transmission member such as a pulley and a belt connected to an end of each transfer shaft to transfer the substrate G. have.

The treatment tank 13 is installed in the lower part of the substrate G and collects the chemical liquid after the process for the substrate G is collected. Piping can be connected. That is, the chemical liquid injected in the substrate processing unit 10 may be received and recovered into the chemical liquid tank 20. On the other hand, the structure of the substrate processing unit 10 is not limited to this, it can be changed by those skilled in the art.

The chemical liquid tank 20 has a substantially cylindrical or rectangular parallelepiped shape and provides a space for storing the chemical liquid used in the substrate processing unit 10, and supplies the chemical liquid to the injection nozzle 11 of the substrate processing unit 10 and the substrate processing unit 10. The chemical liquid can be recovered from the treatment tank 13). The chemical tank 20 may be connected to a pipe (not shown) for supplying a new chemical liquid and a pipe (not shown) for discharging the reused chemical liquid.

On the other hand, the chemical liquid tank 20 may be provided with a level measuring device for measuring the level of the chemical liquid stored in the chemical liquid tank 20. This will be described later in detail with reference to FIGS. 2 to 4.

The chemical liquid supply pump 30 may supply the chemical liquid stored in the chemical liquid tank 20 to the slit nozzle 11 of the substrate processing unit 10. That is, the chemical liquid supply pump 30 may supply the chemical liquid from the chemical liquid tank 20 to the substrate processing unit 10. As the chemical liquid supply pump 30, various kinds of pumps, such as a rotary pump and a centrifugal pump, may be used.

At this time, the chemical liquid supply pump 30 may pressurize the pressure of the chemical liquid supplied to the substrate processing unit 10 to the required process pressure according to the type and characteristic of the process performed in the substrate processing unit 10.

In addition, the number and configuration of the chemical liquid supply pump 30 can be changed according to the size of the chemical liquid tank 20, the flow rate of the chemical liquid supplied to the substrate processing unit 10, and the like.

Meanwhile, the chemical liquid tank 20 may be provided with a temperature control device (not shown) such as a heating unit for heating the chemical liquid so that the chemical liquid stored therein is maintained at an appropriate temperature that can be used in the substrate processing unit 10. . At this time, the temperature of the chemical liquid used in the substrate processing unit 10 may vary depending on the type and characteristics of the process. In addition, the chemical tank 20 may also be provided with various control devices for adjusting the pressure, concentration, level of the chemical liquid.

Meanwhile, the substrate processing apparatus 1 according to the exemplary embodiment of the present invention supplies the chemical liquid from the chemical liquid tank 20 to the substrate processing unit 10, and supplies the chemical liquid from the substrate processing unit 10 to the chemical liquid tank 20 again. A plurality of pipes 41, 42, 43 may be included as a path for the recovery. That is, as shown in FIG. 1, the substrate processing apparatus 1 includes a first pipe 41, a chemical liquid supply pump 30, and a substrate processing unit 10 that connect the chemical liquid tank 20 and the chemical liquid supply pump 30. The second pipe 42 to connect the injection nozzle of the) and the third pipe 43 to connect the processing tank 13 and the chemical tank 20 of the substrate processing unit 10 may be included. The configuration of such a pipe is not limited to this, and can be changed by those skilled in the art.

Hereinafter, with reference to FIGS. 2 and 3, the structure and operation of the level measuring device for the chemical liquid tank will be described.

2 is a view schematically showing the structure of the level measuring device for the chemical liquid tank according to an embodiment of the present invention, Figure 3 is a cross-sectional view showing the installation state of the tube tube and the level sensing unit in the level measuring device for the chemical liquid tank of FIG. to be.

As shown in FIG. 2, the chemical liquid S used in the process by mixing various types of treatment liquids, for example, the first treatment liquid and the second treatment liquid may be stored in the chemical liquid tank 20. In this case, the first liquid storage unit 21 storing the first processing liquid and the second storage unit 23 storing the second processing liquid may be connected to the chemical liquid tank 20. In addition, the chemical liquid tank 20 may be connected to the pipe 41 for supplying the chemical liquid to the substrate processing unit 10. Meanwhile, the flow rate of the first processing liquid, the second processing liquid or the chemical liquid is adjusted to the pipe connected to the first storage part 21 and the second storage part 23 and the pipe 41 connected to the substrate processing part 10. Various valves 22, 24, 25, and 44 may be connected.

The level measuring device may be connected to the side of the chemical liquid tank 20. As shown in FIG. 2, the level measuring device for the chemical liquid tank according to the exemplary embodiment of the present invention may include a tube tube 110, a level detector 120, and a level display unit 130.

The tube tube 110 may also be connected in parallel with the chemical liquid tank 20 storing the chemical liquid, and a portion of the chemical liquid may be introduced according to the level of the chemical liquid stored in the chemical liquid tank 20. That is, the tube tube 110 is bypassed to the upper and lower portions of the chemical liquid tank 20 so that the level of the chemical liquid S inside the chemical liquid tank 20 can be easily measured from the outside of the chemical liquid tank 20. Connected to draw a portion of the chemical liquid from the chemical tank 20. Therefore, since the tube tube 110 is installed outside the chemical liquid tank 20 to measure the level of the chemical liquid, the chemical liquid S inside the chemical liquid tank 20 is not affected at all. At this time, the level of the chemical liquid (S1) in the tube tube 110 may change in conjunction with the level of the chemical liquid (S) in the chemical liquid tank 20, the chemical liquid (S1) of the inside of the tube tube (110) The relationship between the level and the level of the chemical liquid S in the chemical liquid tank 20 (or the relationship between the flow rate of the chemical liquid S1 in the tube tube 110 and the flow rate of the chemical liquid S in the chemical liquid tank 20) May be determined according to the shape and size of the chemical tank 20, the shape of the tube tube 110, and the like. The relationship between the level of the chemical liquid S1 in the tube tube 110 and the level of the chemical liquid S in the chemical liquid tank 20 may be set in advance. Tube tube 110 may have an approximately cylindrical long tubular shape, but is not limited thereto.

Meanwhile, the material of the tube tube 110 may be a transparent glass material or a synthetic resin material. Preferably, PFA (PerFluoroAlkoxy), which is a kind of Teflon fluorine resin resistant to corrosion, may be used. At this time, if the transparent PFA tube tube 110 is used, the level of the chemical liquid can be easily visually checked even outside the chemical tank 20.

The level detector 120 measures the level of the chemical liquid S inside the chemical tank 20 by measuring the level of the chemical liquid S1 introduced into the tube tube 110, and the tube tube 110. It may be installed side by side in the longitudinal direction of the tube tube 110 on the outer side of the). That is, as shown in Figure 3, the level detecting unit 120 is installed in a form surrounding the outer surface of the tube tube 110 so as to face each other with the tube tube 110 installed in the chemical tank 20 in between. Can be. Preferably, the pair of level detectors 120a and 120b may be symmetrically installed around the tube tube 110. The level detector 120 may be attached to the outer surface of the tube tube 110 in the form of a tape. By providing a pair of level detectors 120a and 120b, the accuracy of level measurement can be increased.

Preferably, the level detecting unit 120 may change the level of the chemical liquid S1 introduced into the tube tube 110 by using a current value that is changed and output according to the water level level of the chemical liquid S1 introduced into the tube tube 110. The level can be measured. This method may use the same principle as the capacitive method of sensing an object using a capacitive sensor. That is, the capacitive method is a non-contact measuring method that outputs a detection signal when the object to be detected is close to the detection surface, and detects the change in the current value (capacitance value) according to the change of the electric field to determine the presence or absence of the detection object. That's the way. Therefore, when the chemical liquid passes through the tube tube 110 installed outside the chemical tank 20, the level detection unit 120 attached to the tube tube 110 outside the level of the chemical liquid (S1) inside the tube tube 110. The level of the chemical liquid can be measured by measuring the current value that changes accordingly. As the material of the level sensing unit 120, a conductor such as SUS thin film, aluminum tape, or carbon may be used.

On the other hand, the current value output from the level sensing unit 120 may be directly proportional to the level of the chemical liquid (S1) inside the tube tube (110). More precisely, the change of the current value output from the level sensor 120 according to the change of the level of the chemical liquid S1 in the tube tube 110 is calculated and the change value is added to the current value in the previous state. While pulling out, the value output from the level detector 120 may be continuously calculated. Therefore, the current value can be output in an analog form that continuously changes in accordance with the change of the level of the chemical liquid S1 in the tube tube 110.

Meanwhile, the correlation between the current value output from the level sensing unit 120 and the level of the chemical liquid S1 inside the tube tube 110 may be set in advance. For example, if the current value output from the level detector 120 has a range of about 4 to 20 mA, the current value when the inside of the chemical tank 20 is completely empty, 4 mA, the chemical liquid The current value when the chemical liquid S in the tank 20 is at the maximum level (that is, when the chemical liquid is at the maximum flow rate) may be initialized to 20 mA. At this time, it is not necessary to initialize when the chemical tank 20 is empty to the minimum value of the current value, and when the chemical liquid S inside the chemical tank 20 is at the minimum level (that is, when the chemical liquid is at the minimum flow rate). It can also be initialized to the minimum value of the current value of. In addition, the range of the current value output from the level detector 120 may also be arbitrarily adjusted.

If the capacitive sensor is densely arranged along the longitudinal direction of the tube tube 110 to measure the level of the chemical liquid inside the tube tube 110, the chemical liquid level change is continuously measured to obtain a precise output. In order to solve this problem, more sensors must be densely arranged, and even when the liquid reaches the space between the sensors, the sensor may not detect properly, resulting in an irregular output value.

However, the level measuring device for the chemical liquid tank according to an embodiment of the present invention, the measurement is subdivided according to the level of the chemical liquid using the capacitive level detection unit 120 installed in the longitudinal direction of the tube tube 110 Since the data can be obtained, it is possible to continuously detect the level change of the chemical liquid S in the chemical liquid tank 20. In addition, a pair (120a, 120b) is installed to face the level detector 120 around the tube tube 110 can increase the accuracy of the chemical level detection. In addition, since the level of the chemical liquid can be measured in a non-contact manner from the outside of the chemical liquid tank 20, it is not in direct contact with the chemical liquid can increase the durability and stability of the level measuring device, and can facilitate maintenance of the level measuring device. have. In addition, according to the size of the chemical tank 20, the tube tube 110 and the level sensing unit 120 to be installed on the side of the chemical tank 20 may be designed so that the configuration around the chemical tank 20 can be simplified. It can increase space utilization and reduce costs.

Meanwhile, as shown in FIG. 3, the level detecting unit 120 may be provided with protective covers 121a and 121b for protecting the level detecting units 120a and 120b from external influences. The protective covers 121a and 121b may be formed of a cover such as acrylic. In FIG. 3, an example in which the protective covers 121a and 121b are provided as a pair is illustrated, but may be integrally formed.

Referring back to FIG. 2, the level display unit 130 may serve to display a level level of the chemical liquid S in the chemical liquid tank 20 measured by the level sensor 120. The level display unit 130 may include a cathode ray tube (CRT), a liquid crystal display (LCD), a light-emitting diode (LED), an organic light-emitting diode (OLED), or Various display devices such as a plasma display panel (PDP) may be used.

Meanwhile, the level measuring device for the chemical liquid tank according to an embodiment of the present invention receives and processes a current value output in analog form continuously changing from the level sensing unit 120, and uses the processed value to display the level display unit ( The controller 130 may include a control unit (not shown) for controlling the display of the level of the chemical liquid. The controller may use a programmable logic controller (PLC) or the like.

Hereinafter, a level measuring device for a chemical liquid tank according to another embodiment of the present invention will be described with reference to FIG. 4. 4 is a view schematically showing the structure of a level measuring device for a chemical liquid tank according to another embodiment of the present invention. For convenience of description, members having the same function as the members shown in the drawings (FIGS. 1 to 3) of the first embodiment are denoted by the same reference numerals, and thus description thereof will be omitted, and the following description will mainly focus on differences.

As shown in FIG. 4, in the case of a level measuring device for a chemical liquid tank according to another embodiment of the present invention, the level detecting unit 140 may be directly attached to an outer surface of the chemical liquid tank 20 for storing the chemical liquid. . Therefore, the level detecting unit 140 may directly measure the level of the chemical liquid S in the chemical liquid tank 20. The level sensing unit 140 may be attached to the outer surface of the chemical tank 20 in the form of a tape.

Preferably, as shown in Figure 4, the level detecting unit 140 is provided with a pair (140a, 140b), continuous on the outer surface of the chemical liquid tank 20 in the longitudinal direction of the chemical liquid tank 20 Can be installed side by side. At this time, the level detection unit 140 of the pair (140a, 140b) may be attached side by side up and down at regular intervals. As such, the level detection unit 140 may be provided with the pairs 140a and 140b in parallel to increase the accuracy of the level measurement. In FIG. 4, an example in which the pair of level detectors 140a and 140b are attached is illustrated, but is not limited thereto.

In the present embodiment, the substrate G is for manufacturing a flat panel display (FPD) and is a rectangular flat plate, and the flat panel display is a liquid crystal display (LCD), a plasma display (PDP), or a vacuum fluoride (VFD). Display), FED (Field Emission Display), or ELD (Electro Luminescence Display). Alternatively, the substrate G may be a wafer used for manufacturing a semiconductor chip.

Those skilled in the art will appreciate that the present invention can be embodied in other specific forms without changing the technical spirit or essential features of the present invention. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive. The scope of the present invention is indicated by the scope of the following claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and the equivalent concept are included in the scope of the present invention. Should be interpreted.

1 is a view schematically showing the structure of a substrate processing apparatus according to an embodiment of the present invention.

2 is a view schematically showing the structure of a level measuring device for a chemical liquid tank according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating an installation state of a tube tube and a level sensing unit in the level measuring device for the chemical liquid tank of FIG. 2.

4 is a view schematically showing the structure of a level measuring device for a chemical liquid tank according to another embodiment of the present invention.

(Explanation of symbols for the main parts of the drawing)

1: substrate processing apparatus G: substrate

10: substrate processing unit 20: chemical liquid tank

30: chemical supply pump 41, 42, 43: piping

100: level measuring device for chemical tank

110: tube tube 120: level detection unit

130: level display

Claims (5)

A tube tube connected in parallel with a chemical liquid tank for storing the chemical liquid, and a portion of the chemical liquid flowed in according to the level of the chemical liquid stored in the chemical liquid tank; Continuously installed side by side in the longitudinal direction of the tube tube on the outer surface of the tube tube, a level detection of measuring the water level level of the chemical liquid inside the chemical tank by measuring the water level level of the chemical liquid introduced into the tube tube part; And And a level display unit displaying a level level of the chemical liquid inside the chemical liquid tank measured by the level detecting unit. The method of claim 1, The level sensing unit is a level measuring device for a chemical liquid tank for measuring the level of the chemical liquid introduced into the tube tube using a current value which is changed according to the water level level of the chemical liquid introduced into the tube tube. The method of claim 2, The level detecting unit is a level measuring device for a chemical tank using a SUS thin film, aluminum tape, or carbon. The method of claim 1, The level detection unit is a level measuring device for a chemical liquid tank is provided with a protective cover for protecting the level detection unit from the external influence. A pair of level sensing units continuously installed side by side in the longitudinal direction of the chemical liquid tank on the outer surface of the chemical liquid tank for storing the chemical liquid, and measuring a level level of the chemical liquid in the chemical liquid tank; And A level measuring device for a chemical liquid tank including a level display for displaying the level of the liquid level measured by the level detection unit.

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