Liquid level measurement method and liquid level measurement device
The liquid level measuring device uses a vibrator's decay time to accurately measure liquid levels continuously, addressing the limitations of discrete measurements and volume reduction in existing technologies, suitable for corrosive environments and miniaturized equipment.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- TOKYO ELECTRON LTD
- Filing Date
- 2023-01-12
- Publication Date
- 2026-06-23
Smart Images
Figure 0007878840000018 
Figure 0007878840000019 
Figure 0007878840000020
Abstract
Description
Technical Field
[0001] The present disclosure relates to a liquid level measurement method and a liquid level measurement device.
Background Art
[0002] Patent Document 1 proposes a detector that determines whether the level of a powder or liquid has reached a predetermined level by detecting the difference in the amplitude of an electrical signal generated when the powder or liquid in a container presses on a vibrator in the container and when it does not.
[0003] Patent Document 2 proposes a liquid level gauge that measures the liquid level using a vibrator. The liquid level gauge has a detection part exposed from the housing of an I-shaped sounding piece that utilizes the lateral vibration of a rod. When the powder contacts and restrains the detection part, the vibration attenuates and stops, and when the powder is removed, the vibration resumes. Therefore, the level of what restrains the vibration of the I-shaped sounding piece is detected.
[0004] Patent Document 3 proposes a liquid level gauge that has a vibrator partially inserted through the liquid surface into the stored liquid and whose natural vibration frequency changes according to the liquid level of the liquid, and a vibration mechanism that imparts vibration to the vibrator. The liquid level gauge includes a frequency detection means for detecting the natural vibration frequency of the vibrator accompanying the imparting of vibration, and a means for calculating and displaying the liquid level based on the output of the frequency detection means.
Prior Art Documents
Patent Documents
[0005]
Patent Document 1
Patent Document 2
Patent Document 3
Summary of the Invention
Problems to be Solved by the Invention
[0006] This disclosure provides a liquid level measuring method and a liquid level measuring device that can accurately measure the liquid level inside a container. [Means for solving the problem]
[0007] According to one aspect of the present disclosure, a liquid level measuring device is used to measure a liquid level, the device having a vibrator immersed in a liquid in a container, the vibrator having a rectangular surface perpendicular to the direction of vibration, the method comprising: exciting the vibrator with an exciter; timing the time it takes for the amplitude of vibration generated in the vibrator to decay to a predetermined level when the excitation of the vibrator is stopped; and calculating the liquid level corresponding to the time it takes to decay to the predetermined level based on correlation information between the decay time and the liquid level of the liquid. Furthermore, the step of calculating the liquid level involves, when the decay time is T and the liquid level of the liquid is l, calculating the liquid level corresponding to the time it takes to decay to the level based on the correlation information shown in the following equation (a):
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[0008] One aspect of this method is that the liquid level inside the container can be measured with high accuracy. [Brief explanation of the drawing]
[0009] [Figure 1] A diagram showing an example of a container to which a liquid level measuring device according to one embodiment is fixed. [Figure 2] A flowchart showing an example of a liquid level measurement method according to one embodiment. [Figure 3] A figure showing an example of the amplitude of vibration generated in a vibrator of a liquid level measuring device according to one embodiment. [Figure 4] A figure showing an analysis model according to one embodiment. [Figure 5] A diagram showing an example of a vaporizer and film-forming apparatus according to one embodiment. [Modes for carrying out the invention]
[0010] Hereinafter, embodiments for implementing the present disclosure will be described with reference to the drawings. In each drawing, the same reference numerals are assigned to the same components, and redundant descriptions may be omitted.
[0011] In this specification, in directions such as parallel, right angle, orthogonal, horizontal, vertical, up and down, left and right, etc., a deviation that does not impair the effects of the embodiments is allowed. The shape of the corners is not limited to a right angle and may be arcuate and rounded. For parallel, right angle, orthogonal, horizontal, vertical, circle, coincidence, substantially parallel, substantially right angle, substantially orthogonal, substantially horizontal, substantially vertical, substantially circle, substantially coincidence may be included.
[0012] [First] As an example of a technique for measuring the liquid level (liquid level) of a liquid stored in a tank (container) used in a vaporizer or the like, there is a float switch. Also, as an example of a technique for measuring the liquid level using vibration, there is a level switch that gives vibration to a vibrator by an actuator and then detects whether the vibrator is in contact with a liquid or powder based on the presence or absence of vibration decay when the excitation is stopped.
[0013] Since the float switch floats a float having a certain volume in the liquid to generate buoyancy, the amount of liquid that can be accommodated in the tank becomes small. Also, since the liquid level is measured by the on / off of the switch due to the up and down movement of the float, only information such as whether a specific liquid level is exceeded or not can be detected for each float. By increasing the number of floats, multiple liquid levels can be detected, but the amount of liquid that can be accommodated in the tank further decreases accordingly. Also, the measurement of the liquid surface becomes discrete points.
[0014] Since the level switch measures one liquid level based on the presence or absence of contact of a liquid or powder with one vibrator, a plurality of vibrators are required to measure a plurality of liquid levels.
[0015] In contrast, this embodiment provides a liquid level measuring device that can measure the liquid level linearly (continuously) over the length of the transducer while avoiding a reduction in the amount of liquid that can be contained in the tank. This makes it possible to measure the liquid level in the container 110 with greater accuracy.
[0016] [Liquid level measuring device] Referring to Figure 1, a liquid level measuring device 100 according to one embodiment will be described. Figure 1 is a diagram showing an example of a container 110 to which the liquid level measuring device 100 according to one embodiment is fixed.
[0017] A liquid is stored inside container 110. Container 110 is made of a material resistant to corrosive liquids, such as stainless steel. For example, container 110 is a tank for a vaporizer or the like.
[0018] The liquid level measuring device 100 includes a vibrator 101 immersed in the liquid in the container 110, an exciter 102, a vibration sensor 103, and a control device 150. The vibrator 101 is a plate-shaped member, possessing a certain degree of hardness and flexibility, and vibrating in the vibration direction D. The vibrator 101 has a thin thickness in the vibration direction D, and the surface perpendicular to the vibration direction D forms a rectangle. The vibrator 101 is made of a material resistant to corrosive liquids, such as stainless steel, and may be made of the same material as the container 110, for example. The vibrator 101 is not limited to a plate shape and may be rod-shaped, but it is preferable to have a thickness and shape that allows for easy vibration.
[0019] The vibrator 102 is attached to the upper end of the transducer 101 and vibrates the transducer 101. The initial vibration of the transducer 101 may be close to its natural frequency, but is not limited to this. Furthermore, the amplitude of the vibration generated in the transducer 101 by the vibration of the vibrator 102 is controlled to a range in which the transducer 101 does not come into contact with the container 110 and the liquid level inside the container 110 does not change significantly.
[0020] The vibration sensor 103 is attached near the upper end of the vibrator 101. The vibration sensor 103 measures the amplitude of vibrations generated in the vibrator 101 due to excitation. The vibration sensor 103 is an example of a measuring unit that measures the amplitude of a vibrating vibrator 101.
[0021] The liquid level measuring device 100 is fixed to the container 110. For example, the vibrator 101 is inserted into the container 110 through a hole (not shown) made in the lid 110a of the container 110, and is positioned so that a portion of it is submerged in the liquid inside the container 110. The exciter 102 is positioned outside the lid 110a, thereby fixing the vibrator 101 to the lid 110a at its upper end.
[0022] The vibration sensor 103 is positioned directly below the lid 110a and is used to detect the movement (vibration) of the vibrator 101 inside the container 110. The vibration sensor 103 is configured to be protected from corrosion by the liquid. The vibrator 102 may also be placed inside the container 110, provided that it is configured to be protected from corrosion by the liquid.
[0023] The control device 150 processes computer-executable instructions that cause various steps of the liquid level measurement method described later in this disclosure to be performed. In one embodiment, the control device 150 may include a processing unit, a storage unit, and a communication interface (not shown). The control device 150 is implemented, for example, by a computer, processor, and controller, and is an arithmetic unit that calculates the liquid level in the container 110. The processing unit may be configured to perform various control operations by reading a program from the storage unit and executing the read program. This program may be stored in the storage unit in advance, or it may be obtained via a medium when needed. The obtained program is stored in the storage unit and read from the storage unit and executed by the processing unit. The medium may be various storage media readable by a computer, or it may be a communication line connected to a communication interface. The processing unit may be a CPU (Central Processing Unit). The storage unit may include RAM (Random Access Memory), ROM (Read Only Memory), HDD (Hard Disk Drive), SSD (Solid State Drive), or a combination thereof. The communication interface may communicate with the liquid level measuring device 100 via a communication line such as a LAN (Local Area Network). The communication interface may also communicate with the liquid level measuring device 100 wirelessly or via a wired connection.
[0024] The control device 150 transmits a control signal to the vibrator 102 to start vibration. The control device 150 acquires the amplitude of the vibrating vibrator 101 measured by the vibration sensor 103. When the amplitude measured by the vibration sensor 103 stabilizes, the control device 150 transmits a control signal to the vibrator 102 to stop vibration.
[0025] The vibration sensor 103 measures the amplitude of vibration generated in the vibrator 101 when the vibrator 102 stops vibrating. The control device 150 takes time for the amplitude of the vibrator 101 to decay from the first level, with the amplitude measured by the vibration sensor 103 when the vibration stops being defined as the first level, to a predetermined second level. For example, the control device 150 may take time for the amplitude of the vibrator 101 at the first level measured by the vibration sensor 103 when the vibration stops to decay to a second level, which is 1 / 2 to 1 / 10 of the amplitude of the first level. However, the second level does not have to be less than the first level.
[0026] As shown in Figure 1, the resistance to the motion of the oscillator 101 changes depending on the area S perpendicular to the vibration direction D of the oscillator 101 immersed in the liquid. For example, the larger the area S of the oscillator 101 immersed in the liquid, the greater the resistance value when the oscillator 101 vibrates, and the shorter the damping time. Therefore, a correlation exists where a higher liquid level increases the depth (area S) to which the oscillator 101 is immersed in the liquid, the greater the resistance value received from the liquid, and the shorter the damping time of the amplitude of vibration generated in the oscillator 101. For this reason, if the viscosity of the liquid to be measured and the restoring force of the oscillator 101 are constant, the control device 150 can calculate the liquid level from the damping time of the amplitude of the vibrating oscillator 101 based on the correlation information between damping time and liquid level, since the damping time changes only with respect to the liquid level.
[0027] The correlation between decay time and liquid level may be shown by a correlation equation between decay time and liquid level derived using the analysis model described later. This correlation equation may be stored in a memory unit. The correlation between decay time and liquid level may be shown by measuring the relationship between decay time and liquid level multiple times and pre-storing the measurement results in a memory unit within the control device 150 or a memory unit connected to the control device 150. The relationship between decay time and liquid level may be measured for each type of liquid, and the measurement results for each type of liquid may be pre-storing in a memory unit within the control device 150 or the like.
[0028] The control device 150 may calculate the liquid level from the measured decay time based on a correlation formula. Alternatively, the control device 150 may calculate the liquid level from the measured decay time based on correlation information between decay time and liquid level by referring to a memory unit.
[0029] If correlation information between decay time and liquid level for each type of liquid is stored in the memory unit based on measured values of decay time and liquid level for each type of liquid, the control device 150 may then retrieve the correlation information corresponding to the type of liquid in the container 110 from the stored correlation information. Based on the retrieved correlation information, the control device 150 may then calculate the liquid level corresponding to the decay time.
[0030] [Liquid level measurement method] Next, a liquid level measurement method according to one embodiment will be described with reference to Figures 2 and 3. Figure 2 is a flowchart showing an example of a liquid level measurement method according to one embodiment. Figure 3 is a diagram showing an example of the amplitude of vibration generated in the vibrator 101 of the liquid level measuring device 100 according to one embodiment.
[0031] When the liquid level measurement method shown in Figure 2 is started, in step S1, the control device 150 vibrates the vibrator 101 with the vibrator 102. The control device 150 starts the vibration by the vibrator 102, for example, by controlling an actuator such as a motor that operates the vibrator 102.
[0032] Next, in step S3, the control device 150 acquires the amplitude of vibration generated in the vibrator 101, as measured by the vibration sensor 103, and determines whether the vibration of the vibrator 101 has stabilized. For example, the control device 150 may determine that the vibration of the vibrator 101 has stabilized when the fluctuation in the amplitude of vibration generated in the vibrator 101 falls within a preset tolerance value. The control device 150 may also determine that the vibration of the vibrator 101 has stabilized when the amplitude of vibration generated in the vibrator 101 reaches a preset value.
[0033] In step S3, the control device 150 repeats steps S1 and S3 until it determines that the vibration of the vibrator 101 has stabilized, thereby waiting until the vibration of the vibrator 101 stabilizes.
[0034] When the control device 150 determines that the vibration of the vibrator 101 has stabilized, it proceeds to step S5, where it stops the actuator and stops the excitation of the vibrator 101 by the exciter 102. The control device 150 stops the excitation of the vibrator 101 by the exciter 102 when, for example, the amplitude of the vibration generated in the vibrator 101 due to the excitation of the vibrator 101 has stabilized at a first level. The vibration sensor 103 measures the amplitude of the vibrating vibrator 101 when the excitation of the vibrator 101 has stopped. The control device 150 acquires the amplitude of the vibrator 101 measured by the vibration sensor 103 when the excitation of the vibrator 101 has stopped.
[0035] In Figure 3, an example of the amplitude of vibration generated in the oscillator 101, the horizontal axis represents time, and the vertical axis represents the amplitude of vibration generated in the oscillator. Since the vibration of the oscillator 101 stabilized at amplitude A before time t0, the excitation of the oscillator 101 by the exciter 102 was stopped at time t0. Amplitude A is an example of the amplitude of the first level.
[0036] Returning to Figure 2, in step S7, the control device 150 measures the decay time T at which the amplitude of the oscillator 101 decreases to 1 / n of the amplitude at which the excitation of the oscillator 101 is stopped. In Figure 3, the amplitude decreases to 1 / n during the time T from time t0 to time t1.
[0037] 1 / n represents the amplitude of a second level which is smaller than the amplitude of the first level. 1 / n may be set, for example, to 1 / 4 of the amplitude of the first level. In this way, the control device 150 measures the time it takes for the amplitude of vibration generated in the oscillator 101 to decay from the first level to the second level when the excitation of the oscillator 101 is stopped.
[0038] Next, in step S9, the control device 150 calculates the liquid level corresponding to the measured decay time based on correlation information (e.g., correlation formula) between decay time and liquid level.
[0039] Next, in step S11, the control device 150 determines whether the calculated liquid level is below a preset threshold. If the control device 150 determines that the calculated liquid level is below a preset threshold, it replenishes the container 110 with liquid and terminates the process. If the control device 150 determines that the calculated liquid level is greater than a preset threshold, it terminates the process without replenishing the liquid.
[0040] According to the liquid level measurement method of this embodiment, by keeping the amplitude of the oscillator 101 constant (for example, amplitude A in Figure 3), the time it takes for the vibration to decay to a certain amplitude (for example, amplitude A / n in Figure 3) can be considered a value determined solely by the drag force that the oscillator 101 receives from the liquid. The larger the area of the oscillator 101 immersed in the liquid, the greater the damping force and the shorter the decay time. Therefore, the liquid level can be calculated from the decay time corresponding to the damping force.
[0041] Furthermore, according to the liquid level measurement method of this embodiment, compared to the float of the float switch used in the container 110, it is possible to measure the liquid level linearly or with fine increments equal to the length of the longitudinal direction (direction perpendicular to the liquid surface) of the transducer 101.
[0042] Furthermore, compared to the float of a float switch, the volume occupied by the liquid level measuring device 100 is significantly reduced, which increases the amount of liquid that can be contained in the container 110. The material of the transducer 101 can be freely changed. Therefore, it is preferable to use the same material for the transducer 101, exciter 102, and vibration sensor 103 as the container 110, which is corrosion-resistant even with corrosive liquids. This makes it possible to measure the liquid level even if the gas vaporized from the liquid comes into contact with the transducer 101, exciter 102, and vibration sensor 103. As shown in Figure 1, when the container 110 in which the liquid level measuring device 100 is installed is used in equipment such as a vaporizer, the equipment can be miniaturized.
[0043] In Figure 1, the liquid level measuring device 100 is fixed to the lid 110a, and the vibrator 101 hangs down from the lid 110a, extending to near the bottom of the container 110 without touching the bottom surface of the container 110. Fixing the liquid level measuring device 100 to the lid 110a in this way makes it easier to keep the vibration sensor 103 away from the liquid surface and to protect the vibration sensor 103. In addition, since the amplitude of vibration when the vibrator 101 is excited is largest near the bottom surface of the container 110, the vibration damping effect is also large, and the accuracy of liquid level measurement by the liquid level measuring device 100 can be improved.
[0044] However, the liquid level measuring device 100 is not limited to being fixed to the top of the container 110. The liquid level measuring device 100 may also have a transducer 101 extending from the bottom of the container 110 to near the bottom surface of the lid 110a, while avoiding leakage of liquid from the container 110. In this case, the tip of the transducer 101 is located at the top of the container 110, the vibration sensor 103 is attached to the tip of the transducer 101, and the vibrator 102 is placed at the bottom. Therefore, it becomes possible to measure the liquid level over a wider range in the height direction, from near the bottom surface of the container 110 to near the bottom surface of the lid 110a. In addition, in this case, the installation of the liquid level measuring device 100 becomes easier.
[0045] [Analysis Model] The damping force (drag) on the motion of the oscillator 101 changes depending on the area of the oscillator 101 immersed in the liquid in the container 110. The area of the oscillator 101 immersed in the liquid is rectangular. Therefore, as mentioned above, as the liquid level rises, the depth (area) of the oscillator 101 immersed increases, the damping force (drag) from the liquid increases, and the damping time of the oscillator 101 decreases. For this reason, if the viscosity of the liquid to be measured and the restoring force of the oscillator are constant, the damping time changes only with respect to the liquid level, and it is possible to calculate the liquid level from the damping time.
[0046] This section explains the derivation of a linear equation (correlation equation) for calculating the liquid level from the decay time performed in the analytical model. Figure 4 shows an analytical model according to one embodiment. The analytical model used to derive the linear equation is a model in which the oscillator 101 is immersed in liquid and rotates (vibrates) as shown in Figure 4(b), as shown in Figure 4(a). L represents the length from the fixed point 101a to which the oscillator 101 is fixed to the tip of the oscillator 101, and l represents the length of time the oscillator 101 is immersed in the liquid. Since the tip of the oscillator 101 is not in contact with the bottom surface of the container 110, the actual liquid level in the container 110 is the liquid level l calculated in this specification plus the distance from the tip of the oscillator 101 to the bottom surface of the container 110.
[0047] In the analysis model, the oscillator 101 rotates (vibrates) around the fixed point 101a as a fulcrum. Let θ be the angle between the oscillator 101 and the axis perpendicular to the liquid surface. Note that θ represents the degree of vibration caused by the oscillator 101 and is smaller than the angle shown in Figure 4(b). The restoring force on the object causing the vibration (exciter 102 in Figure 1) in the analysis model is illustrated and visualized as a spring 105 in Figure 4(b).
[0048] The conditions in the analysis model shown in Figure 4 are assumed to be as follows: Let I be the moment of inertia of the rotational motion (vibration) of the oscillator 101, and let -kθ be the restoring force. The restoring force is the force that attempts to restore the oscillator 101 when θ changes, and in Figure 4(b), it is visualized as a spring 105 that does not actually exist.
[0049] Assuming that the moment due to the drag force is equal to the viscous resistance (a value determined by the viscosity and velocity of the liquid),
[0050]
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[0051] (Derivation of amplitude) The equation of motion for oscillator 101 in the above analysis model can be expressed by equation (1).
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[0058] (Derivation of decay time) We calculate the time T (see Figure 3) required for the amplitude a(t) to decay from A to A / n. That is, when the amplitude a(0) at time t0 is A, and the amplitude a(T) at time t1 is A / n, then a(0) is equal to na(T). In this case, the following equation holds from equation (3).
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[0061] At this time, the moment around the support point due to the normal force acting on the part of the oscillator 101 at a distance x from the fixed point 101a can be expressed by the following equation.
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[0064]
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[0065]
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[0066] In the above analysis model, viscous resistance was assumed, and the drag force per unit length of the oscillator 101 was calculated. However, the drag force acting on an object moving in a liquid is generally velocity-squared resistance. In the case of velocity-squared resistance, the equation of motion is given by the following equation.
[0067]
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[0068] [Substrate processing equipment] The liquid level measuring device 100 described above can be attached to and used in various devices. Next, an example of using the liquid level measuring device 100 attached to a vaporizer 180 will be described with reference to Figure 5. Figure 5 is a diagram showing an example of a vaporizer 180 and a film deposition apparatus 200 according to one embodiment. The film deposition apparatus 200 shown in Figure 5 is an example of a substrate processing apparatus.
[0069] The film deposition apparatus 200 includes a chamber 201, an exhaust device 202, a shower head 206, and a stage 207. In this embodiment, the film deposition apparatus 200 is, for example, a CVD (Chemical Vapor Deposition) apparatus.
[0070] A showerhead 206 is provided at the top of the chamber 201. Gas is supplied to the chamber 201 via the showerhead 206. A raw material supply source 203 containing liquid film-forming raw materials is connected to the showerhead 206 via piping 204.
[0071] The film-forming raw material supplied from the raw material source 203 is stored in the container 110 of the vaporizer 180 interposed in the piping 204. In the vaporizer 180, the liquid film-forming raw material is heated (not shown) in the container 110 and vaporized. The raw material gas vaporized by the vaporizer 180 is introduced to the showerhead 206 via the piping 204.
[0072] Numerous discharge holes (not shown) are formed on the underside of the shower head 206. The shower head 206 discharges the raw material gas introduced via the piping 204 into the chamber 201 in a shower-like manner. The exhaust device 202 exhausts the gas from the chamber 201. The chamber 201 is controlled by the exhaust device 202 to maintain a vacuum atmosphere at a predetermined pressure. The exhaust device 202 is controlled by the control device 150.
[0073] A stage 207 on which the substrate W is placed is provided inside the chamber 201. The substrate W is supported by the stage 207. The stage 207 is provided with a heater (not shown) for adjusting the temperature of the substrate W. The control device 150 controls the temperature of the substrate W by controlling the heater so that the upper surface of the substrate W is at a temperature suitable for film deposition of the raw material gas.
[0074] Using such a film deposition apparatus 200, film deposition can be performed on the surface of the substrate W using a raw material gas. In addition, the film deposition apparatus 200 supplies a reaction gas along with the raw material gas to form a desired film on the substrate W.
[0075] A liquid level measuring device 100 is attached to the container 110 of the vaporizer 180. The liquid level measuring device 100 measures the liquid level of the raw material inside the container 110. For example, when the liquid level falls below a threshold, liquid film-forming raw material can be automatically replenished into the container 110.
[0076] However, the method of using the liquid level measuring device 100 is not limited to this. For example, the liquid level measuring device 100 can be used in a liquid supply device. For raw materials with low vapor pressure that cannot be completely vaporized by heating the container itself, a pipe such as a straw is inserted into the container of the liquid supply device and N2 gas or Ar gas is supplied to the space inside the container. This applies pressure to the upper space inside the container, pushing out the liquid inside the container. The pushed-out liquid is supplied to a pipe with a heating element such as a heater, and can be vaporized by heating. The liquid level measuring device 100 measures the liquid level of the liquid supply device. When the liquid level falls below a threshold, liquid can be automatically replenished into the container 110.
[0077] As described above, the liquid level measurement method and liquid level measurement device 100 of this embodiment can measure the liquid level in a container linearly (continuously) with high accuracy.
[0078] The liquid level measuring method and liquid level measuring apparatus according to the embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The embodiments can be modified and improved in various ways without departing from the scope and spirit of the appended claims. The matters described in the above embodiments can be otherwise configured and combined in a non-consistent manner.
[0079] Furthermore, the substrate processing apparatus disclosed herein can be applied to any of the following: a single-wafer processing apparatus that processes substrates one at a time, a batch processing apparatus that processes multiple substrates at once, and a semi-batch processing apparatus. The substrate processing apparatus disclosed herein performs substrate processing such as film deposition and etching. The substrate processing apparatus disclosed herein may be an apparatus that processes substrates using plasma, or an apparatus that processes substrates without using plasma. [Explanation of symbols]
[0080] 100 Liquid level measuring device 101 Oscillator 102 Vibrator 103 Vibration Sensor 110 Container 150 Control device 180 Vaporizer 200 Film deposition equipment
Claims
1. A liquid level measurement method performed using a liquid level measuring device having a vibrator that is immersed in the liquid inside a container, the vibrator having a rectangular surface perpendicular to the direction of vibration, The steps include:
1. Exciting the vibrator with a vibrator, The steps include: measuring the time it takes for the amplitude of vibration generated in the oscillator to decay to a predetermined level when the excitation of the oscillator is stopped; A step of calculating the liquid level corresponding to the time it takes for the liquid to decay to the aforementioned level, based on correlation information between the decay time and the liquid level of the liquid, Includes, The step of calculating the liquid level involves, when the decay time is T and the liquid level is l, calculating the liquid level corresponding to the time it takes to decay to the level based on the correlation information shown in the following formula (a): [Number 13] Note that I is the moment of inertia of the oscillator, L is the distance from the pivot point of the oscillator to the tip of the oscillator, and k c, n, I, and L are constants. Liquid level measurement method.
2. The process includes the step of storing correlation information between the decay time and the liquid level in a storage unit in advance, based on measured values of the decay time and the liquid level of the liquid. The step of calculating the liquid level involves referring to the storage unit and calculating the liquid level corresponding to the time it takes for the liquid to decay to the level based on the correlation information. The liquid level measurement method according to claim 1.
3. The steps include: storing the correlation information for each type of liquid in a storage unit in advance, based on the measured values of the decay time for each type of liquid and the liquid level of the liquid; The step of calculating the liquid level involves calculating the liquid level corresponding to the time it takes for the liquid to decay to the level, based on the correlation information stored in the memory unit, according to the type of liquid in the container. The liquid level measurement method according to claim 2.
4. When the amplitude of the vibration generated in the vibrator by the excitation of the vibrator stabilizes at a first level, the excitation of the vibrator by the vibrator is stopped. The step of timing the decay time involves timing the time it takes for the amplitude of the vibration to decay from a first level to a second level smaller than the first level. A liquid level measurement method according to any one of claims 1 to 3.
5. The second level is 1 / 2 to 1 / 10 of the first level. The liquid level measurement method according to claim 4.
6. If the calculated liquid level is below a preset threshold, the liquid is replenished in the container. A liquid level measurement method according to any one of claims 1 to 3.
7. A vibrator immersed in a liquid inside a container, wherein the vibrator has a rectangular surface perpendicular to the direction of vibration, A vibrator that vibrates the aforementioned vibrator, A measuring unit for measuring the amplitude of the vibrator that vibrates due to excitation, The system includes a control device for calculating the liquid level of the aforementioned liquid, The control device is The steps include:
1. Exciting the vibrator; The steps include: measuring the time it takes for the amplitude of vibration generated in the oscillator to decay to a predetermined level when the excitation of the oscillator is stopped; A step of calculating the liquid level corresponding to the time it takes for the liquid to decay to the aforementioned level, based on correlation information between the decay time and the liquid level of the liquid, Control, The control device is In the step of calculating the liquid level, when the decay time is T and the liquid level of the liquid is l, the liquid level corresponding to the time it takes to decay to the level is calculated based on the correlation information shown in the following formula (a): [Number 13] Note that I is the moment of inertia of the oscillator, L is the distance from the pivot point to the tip of the oscillator, and k, c, n, I, and L are constants. Liquid level measuring device.
8. The control device is The process involves controlling the step of pre-storing correlation information between the decay time and the liquid level in a storage unit based on measured values of the decay time and the liquid level. In the step of calculating the liquid level, the storage unit is referenced to calculate the liquid level corresponding to the time it takes for the liquid to decay to the level based on the correlation information. The liquid level measuring device according to claim 7.
9. The liquid level measuring device is provided in the vaporizer having the container. The liquid level measuring device according to claim 7 or 8.
10. The vaporizer is connected to the substrate processing apparatus via piping, and vaporizes the liquid inside the vaporizer and supplies it to the substrate processing apparatus. The liquid level measuring device according to claim 9.
11. The vibrator is formed of the same material as the container. The liquid level measuring device according to claim 7 or 8.