JPH06117903A - Liquid level detector - Google Patents

Abstract

PURPOSE:To obtain a liquid level measuring device capable of detecting a liquid level without mixing waste refuse with a liquid and capable of being used even when a tank receiving a liquid is a pressure tank. CONSTITUTION:Detection rods 20, 30 are provided in a tank 12 having a semiconductor treatment soln. 10 received therein and temp. sensors 22, 32 fitted with heaters are provided to the lower end parts of the detection rods 20, 30 and temp. sensors 24, 34 are provided to the detection rods above the sensors 22, 32. The tamp. sensors 22, 32 fitted with heaters are heated by supplying a current to the heaters of the temp. sensors 22, 32 fitted with heaters so that the detected temps. due to the temp. sensors 22, 32 fitted with heaters are largely different at the times of the contact and non-contact of the lower end parts of the detection rods 20, 30 with the semiconductor treatment soln. 10 and the detected temps. are compared with the detected temps. due to the temp. sensors 24, 34 to judge whether the liquid level of the semiconductor treatment soln. 10 is higher or lower than the lower end parts of the detection rods 20,30.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level detecting device for detecting the liquid level of a liquid contained in a tank.

[0002]

2. Description of the Related Art Conventionally, when the amount of a semiconductor processing liquid such as a resist liquid used in a semiconductor manufacturing process is detected, for example, as shown in FIG. A nozzle 70 for blowing out high-pressure nitrogen from a height position, a pipe 74 for supplying high-pressure nitrogen to the nozzle 70 through one gas chamber 72a of the diaphragm 72, and a high-pressure nitrogen gas for the other side of the diaphragm 72. Piping 76 that releases to the atmosphere through the chamber 72b
A plurality of liquid level detecting devices 80 are used, which are constituted by a micro switch 78 which is turned on when the partition 72c of the diaphragm 72 is displaced by the pressure difference between the gas chambers 72a and 72b of the diaphragm 72.

That is, this type of liquid level detecting device 80
When the liquid surface approaches the tip of the nozzle 70, the exhaust pressure at the tip of the nozzle 70 increases and the pressure in the nozzle side gas chamber 72a of the diaphragm 72 increases, so that the partition wall 72c is displaced upward in the drawing. Then, the contact point of the micro switch 78 is pushed up, the micro switch is turned on, and it becomes possible to detect that the liquid surface is at the height position of the tip of the nozzle 70. In FIG. 5, reference numeral 64 indicates the semiconductor processing liquid 60 from the tank 62.
Is a pump for pumping the liquid to and supplying it to a semiconductor processing process such as a resist process using the semiconductor processing liquid 60.

[0004]

However, in such a gas level liquid level detecting device, there is a movable part such as a diaphragm or a pressure pump for generating a high pressure gas such as high pressure nitrogen. Cause minute dust to be generated, and the dust is mixed into high-pressure gas such as high-pressure nitrogen blown from the nozzle toward the liquid surface, and the semiconductor processing liquid such as resist liquid is contaminated. Was sometimes.

Further, in such a gas level liquid level detection device, since the liquid level is detected from the change in the injection pressure of the high pressure gas from the nozzle, it is pressurized to a high pressure in order to prevent vaporization of the liquid. There is also a problem that the liquid level cannot be detected in the pressurized tank.

Furthermore, in such a gas level liquid level detecting device, the diaphragm becomes hard after being stopped for a long time, and when the diaphragm is restarted after that, the movement of the diaphragm is restored. There is also a problem that the liquid level cannot be detected normally.

As a liquid level detecting device other than the gas injection system, for example, a liquid level is optically detected using a prism by utilizing the difference in light reflectance between the atmosphere and the liquid. There is also an optical type that measures the liquid level by measuring the electrostatic capacity of the tank.However, in the optical type, the prism that comes into contact with the liquid surface changes color due to the liquid and malfunctions. In addition, there is a case where the capacitance type does not have accuracy enough for practical use, and neither of them has been put into practical use.

The present invention has been made in view of these problems. As described above, the liquid level can be detected without mixing dust in the liquid such as the semiconductor processing liquid, and the tank for storing the liquid is pressurized. An object of the present invention is to provide a liquid level measuring device that can be used even in a tank.

[0009]

A liquid level detecting device according to claim 1, which has been made to achieve the above object, comprises:
In a tank for storing a liquid, a long detection rod arranged in a direction orthogonal to the liquid surface of the liquid, and a pair of lower end portion of the detection rod and a position above the lower end portion, respectively. Based on the temperature sensor and the detection signals from the pair of temperature sensors,
A determination circuit for determining whether or not the lower end of the detection rod comes into contact with the liquid and is cooled by heat conduction of the liquid.

Next, a liquid level detecting device according to a second aspect of the present invention includes a long detection rod arranged in a tank for containing a liquid in a direction orthogonal to the liquid surface of the liquid, and the detection rod. A temperature sensor provided at the lower end of the rod and provided with a heater for heating,
Based on the temperature sensor provided at any position including the lower end of the detection rod, based on the detection signal from the temperature sensor,
A determination circuit for determining whether or not the lower end of the detection rod comes into contact with the liquid and is cooled by heat conduction of the liquid.

Next, in the liquid level detecting device according to the third aspect, in the liquid level detecting device according to the second aspect, a temperature sensor having a heater is provided on the ceramic substrate according to the temperature. Is formed by forming a resistance pattern whose resistance value changes, and further forming a heat generation pattern that generates heat by energization between the resistance patterns.

A liquid level measuring device according to a fourth aspect is the liquid level detecting device according to any one of the first to third aspects, wherein the detection rod is made of a material having corrosion resistance against liquid. A long tubular member, and a sealing member made of a material also having corrosion resistance, which seals the lower end of the tubular member to prevent liquid from entering the inside of the tubular member. It is characterized in that it is arranged inside the tubular member sealed by the sealing member.

Furthermore, in the liquid level detecting device according to a fifth aspect of the present invention, in the liquid level detecting device according to the fourth aspect, the temperature sensor disposed at the lower end of the detection rod is used as a seal member. It is characterized by being joined.

[0014]

In the liquid level detecting device according to claim 1 configured as described above, the determination circuit has a pair of temperature sensors in which the determination circuit is arranged at the lower end of the detection rod and at a position above the lower end. The liquid level is detected by determining whether or not the lower end portion of the detection rod comes into contact with the liquid and is cooled by heat conduction of the liquid based on the detection signal from.

That is, the temperature of the liquid is usually lower than that of the outside air due to evaporation of the liquid or the like, and when the lower end portion of the detection rod comes into contact with the liquid, the temperature of the lower end portion becomes lower than the outside air due to heat conduction of the liquid. In the liquid level detecting device according to claim 1, the lowering of the temperature of the lower end is determined based on detection signals from a temperature sensor provided at the lower end of the detection rod and a temperature sensor provided above the lower end. By doing so, it is determined whether or not the liquid level is lower than the position of the lower end portion of the detection rod.

Therefore, according to the liquid level detecting device of the first aspect, the liquid level can be detected without mixing dust in the liquid, and the tank for storing the liquid is a pressurized tank. Can be used. Next, in the liquid level detecting device according to claim 2, a temperature sensor having a heater for heating is provided at the lower end of the detection rod, and the temperature sensor is provided at any position including the lower end of the detection rod. Based on the detection signals from these temperature sensors, a determination circuit is provided to determine whether or not the lower end of the detection rod is in contact with the liquid and is cooled by heat conduction of the liquid, and the liquid level is detected. Is being done.

That is, since the temperature sensor with the heater is heated by the heater, the temperature detected by the heater is higher than that of the temperature sensor not equipped with the other heater. In addition, the temperature detected by the temperature sensor with the heater drops significantly when the lower end of the detection rod changes from the state where it does not contact the liquid to the state where it contacts the liquid, because the heating temperature by the heater radiates heat through the liquid. To do. Therefore, in the liquid level detecting device according to the second aspect, the temperature change is judged on the basis of the detection signal from the temperature sensor having no heater, whereby the lower end of the detection rod comes into contact with the liquid. It is trying to detect whether or not there is.

Therefore, according to the liquid level detecting device of the second aspect, as in the device of the first aspect, the liquid level can be detected without mixing dust in the liquid and the liquid is stored. It can be used even if the tank used is a pressurized tank. In the liquid level detecting device according to the second aspect, the temperature sensor not provided with the heater may be provided at the lower end portion of the detection rod similarly to the temperature sensor with a heater, or from the lower end portion of the detection rod. It may be provided at an upper position.

This is because even if the temperature sensor not equipped with the heater is provided at the lower end of the detection rod as in the case of the temperature sensor with a heater, the temperature detected by the lower end of the detection rod coming into contact with the liquid is detected. This is because the change is extremely smaller than that of the temperature sensor with a heater, and the change in the temperature detected by the temperature sensor with a heater can be accurately determined based on the detection signal from this temperature sensor.

Next, in the liquid level detecting device according to the third aspect, a temperature sensor with a heater arranged at the lower end portion of the detection rod is mounted on the ceramic substrate, and the resistance value changes according to the temperature. Is formed, and a heating pattern that generates heat when energized is formed between the resistance patterns.

Therefore, the temperature change at the lower end of the detection rod can be detected as a resistance value change, the circuit structure for temperature detection can be simplified, and the temperature pattern can be supplied by energizing the temperature sensor. The resistance pattern can be heated reliably and efficiently.

Further, in the liquid level measuring device according to the fourth aspect, the detection rod is composed of a tubular member and a seal member for sealing the lower end portion thereof, and a pair of temperature sensors are provided.
It is arranged to be arranged inside a tubular member sealed by a seal member. Therefore, it is not necessary to provide a special member for protecting the temperature sensor and its signal line from the liquid, and the configuration can be simplified.

Furthermore, in the liquid level detecting device according to the fifth aspect, the temperature sensor arranged at the lower end of the detecting rod is joined to the seal member. Therefore, compared to the case where the temperature sensor is simply provided inside the detection rod, the temperature sensor can improve the detection sensitivity of the temperature of the lower end portion of the detection rod. It is possible to accurately detect the temperature change caused by the temperature change.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 1 shows a tank 12 containing a semiconductor processing liquid 10.
It is explanatory drawing showing the state which attached the liquid level detection apparatus of a present Example to FIG.

As shown in FIG. 1, in the tank 12, a mounting member 14 fixed to a wall surface near the opening of the tank 12 is used.
Two detection rods 20 and 30 are attached. One of these two detection rods 20 and 30 has a liquid level of the semiconductor processing liquid 10 in the tank 12 which is supplied by a pump 16 which supplies the semiconductor processing liquid 10 to a predetermined semiconductor processing step. The lower end portion is formed long so as not to come into contact with the semiconductor processing liquid 10 when it comes close to the lower limit that can be pumped out, and the other detection rod 30 has a liquid level of the semiconductor processing liquid 10 in the tank 12. The lower end portion is formed to be short so as to come into contact with the semiconductor processing liquid 10 when approaching the predetermined upper limit value.

Further, at the lower end portions of the detection rods 20 and 30,
Heater-equipped temperature sensors 22 and 32 are provided respectively, and temperature sensors 24 and 34 are provided near the attachment members 14 of the respective detection rods 20 and 30. And the detection rod 2
The temperature sensors 22 and 24 provided at 0 are connected to the detection circuit 28 via the signal line 26, and the temperature sensors 32 and 34 provided at the detection rod 30 are provided at the detection circuit 38 via the signal line 36. It is connected to the.

The detection circuits 28 and 38 are used for the tank 12
The semiconductor processing liquid 10 is provided in the controller 40 that controls the supply of the semiconductor processing liquid 10 into the inside, and when the liquid level of the semiconductor processing liquid 10 in the tank 12 falls below the lower limit value on the controller 40 side, the semiconductor processing liquid not shown When the supply pump is started to drive and the liquid level of the semiconductor processing liquid 10 in the tank 12 reaches a predetermined upper limit value, the pump is stopped to drive the semiconductor processing liquid 10 in the tank 12. The quantity is used to control the quantity that can be pumped by the pump 16.

Next, as shown in FIG. 2A, the temperature sensors 22 and 32 with heaters provided at the lower ends of the respective detection rods 20 and 30 are formed on the surface of the ceramic substrate 41 by vacuum deposition of platinum or nickel. And a resistance pattern PRS whose resistance value changes according to temperature, a heat generation pattern PRH that generates heat by energization, and electrode patterns PT1 to PT4 connected to both ends of each of these resistance patterns PRS and PRH. There is. The resistance pattern PRS is shown in FIG.
As shown in FIG. 2B, it is formed by alternately connecting thin linear patterns of about 10 μm, and the heat generation pattern PRH has its resistance pattern P as shown in FIG. 2A.
It is formed so as to bite between the resistance patterns PRS at two locations where RS is divided into three.

The mounting member 1 for each of the detection rods 20 and 30 is also provided.
Similar to the temperature sensors with heaters 22, 32, the temperature sensors 24, 34 provided in the vicinity of 4 have a resistance pattern in which the resistance value changes depending on the temperature on the surface of the ceramic substrate 41 by vacuum deposition of platinum or nickel. It is manufactured by forming PRS and electrode patterns PT1 and PT2 connected to both ends thereof. That is, the temperature sensors 24, 34
Is the ceramic substrate 4 of the temperature sensors 22 and 32 with heaters.
It is manufactured by removing the heat generation pattern PRH and the electrode patterns PT3 and PT4 connected to both ends of the heat generation pattern PRH from above.

On the other hand, the detection rods 20 and 30 are, as shown in FIG. 3A, a glass tube 43 and a press-fitting member made of an elastic material such as rubber which is press-fitted into the glass tube 43 to seal the lower end portion thereof. Seal 45 and glass seal 4 covering the periphery thereof
7 and each of the temperature sensors 22 and 2 described above.
4, 32 and 34 are provided in the sealed glass tube 43.

The temperature sensors 22 and 32 with heaters provided at the lower ends of the detection rods 20 and 30 are the press-fit seals 4
5 is provided so as to protrude from the hole formed at the center of
The surface thereof is directly covered with the glass seal 47. Therefore, when the lower ends of the detection rods 20 and 30 come into contact with the semiconductor processing liquid 10, the resistance values of the heater-equipped temperature sensors 22 and 32 change rapidly depending on the temperature.

The detection rods 20 and 30 are formed by the glass tube 43 and the lower end portions thereof are covered with the glass seal 47 because the detection rods 20 and 30 themselves are strong acid in the semiconductor processing liquid 10. This is for preventing contact and corrosion and for protecting the temperature sensors 22 and 32 with heaters and their signal lines from the semiconductor processing liquid 10.

As described above, the semiconductor processing liquid 10 such as the detection rods 20 and 30 themselves and the temperature sensors 22 and 32 with heaters is used.
In order to prevent the corrosion due to the above, besides glass, Teflon having a corrosion resistance against a strong acid may be used. That is, for example, as shown in FIG. 3B, a Teflon film 49 may be attached to the lower end of the glass tube 43 and fixed to the lower end of the glass tube 43 with a fixing member 51 made of Teflon. Prevent the corrosion of the detection rods 20 and 30 themselves,
The temperature sensors 22 and 32 with heaters and their signal lines can be protected from the semiconductor processing liquid 10. In this case,
It is desirable that the temperature sensors 22 and 32 with heaters be fixed to the Teflon film 49 in order to ensure temperature detection accuracy.

Next, in the detection circuits 28 and 38, as shown in FIG. 4, the DC power source B is connected to the heater element RH formed of the heating pattern PRH of the temperature sensors 22 and 32 with heaters.
A constant current circuit 55 is provided which causes a constant current to flow through the heater element RH to heat the heater element RH.

In the detection circuits 28 and 38, the resistor R1 is connected to the sensor element RS1 formed of the resistance pattern PRS of the temperature sensors 22 and 32 with heaters, and the sensor formed of the resistance pattern PRS of the temperature sensors 24 and 34. Element R
A resistor R2 is connected to S2, and both ends thereof are connected to each other to form a bridge circuit, and a power supply voltage Vcc is applied to both ends of the bridge circuit, and the sensor element R
Connection point voltage V1 between S1 and resistor R1 and sensor element R
The voltage V2 at the connection point between S2 and the resistor R2 is compared with the comparator C.
By comparing with P1, the comparator C can be used only when the lower end of the detection rod is in contact with the semiconductor processing liquid 10.
A high-level determination signal is output from P1 and the switching transistor TR1 becomes conductive, and due to this conduction, a current flows through the light emitting diode D1 via the resistor R3,
A determination circuit 57 configured to cause the light emitting diode D1 to emit light is provided. Further, the determination circuit 57 includes
An output terminal for outputting the detection signal VS indicating the conduction state of the switching transistor TR1 to the control circuit in the controller 40 is also provided.

That is, in the liquid level detecting device of the present embodiment, the heater elements RH of the heater-equipped temperature sensors 22 and 32 provided at the lower ends of the detection rods 20 and 30 are energized, and the heater-equipped temperature sensors 22 and 32 are energized. By heating the sensor element RS1 of FIG.
The resistance value of the sensor element RS1 when not in contact with 0 is set to be larger than the resistance value of the sensor element RS2 of the temperature sensors 24 and 34, and the detection rods 20 and 3 are connected.
When the lower end portion of 0 contacts the semiconductor processing liquid 10, the lower end portion is cooled by heat conduction of the semiconductor processing liquid 10, so that the resistance value of the sensor element RS1 becomes equal to the sensor element RS2.
The resistance level of the semiconductor processing liquid 10 is greatly decreased to the vicinity of the resistance value and the liquid crystal level of the semiconductor processing liquid 10 is detected to be higher than the lower end portions of the detection rods 20 and 30. Has been

As described above, in the liquid level detecting device of this embodiment, the liquid level of the semiconductor processing liquid 10 is detected from the temperature change of the lower end portions of the detection rods 20 and 30, so that the conventional gas injection method is used. Unlike the liquid level detection device of the type, a minute dust is not mixed into the semiconductor processing liquid 10, and the defect rate of the semiconductor can be reduced. Also,
Since the liquid level can be detected without being affected by the pressure of the outside air, the liquid level can be accurately detected even if the tank 12 storing the semiconductor processing liquid 10 is a pressurized tank. Is. Furthermore, since the liquid level detecting device of this embodiment does not have a mechanically movable part, the detection accuracy does not change due to a change with time of the movable part, and the reliability of the device can be improved.

[0038]

As described above in detail, in the liquid level detecting device of the present invention, from the temperature change caused when the lower end of the detection rod is in contact with the liquid and when it is not in contact with the liquid. The liquid level is detected. Therefore, unlike the conventional gas injection type device, dust is not mixed in the liquid at the time of detection, and if it is used for detecting the liquid level of the semiconductor processing liquid as in the above-mentioned embodiment, the semiconductor is defective. The rate can be reduced. Further, since the liquid level can be detected without being affected by the change in the pressure of the outside air, it is possible to accurately detect the liquid level even for the liquid stored in the pressurized tank.
Furthermore, in the liquid level detecting device of the present invention, since there is no mechanically movable part, the detection accuracy does not change due to a change with time of the movable part, and the reliability of the device can be improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a state in which a liquid level detecting device of an embodiment is attached to a tank containing a semiconductor processing liquid.

FIG. 2 is an explanatory diagram illustrating a configuration of a temperature sensor with a heater according to an embodiment.

FIG. 3 is a cross-sectional view showing a configuration near a lower end portion of a detection rod according to an embodiment.

FIG. 4 is an electric circuit diagram showing a configuration of a detection circuit according to an embodiment.

FIG. 5 is an explanatory diagram illustrating a configuration of a conventional liquid surface level detection device and a detection method thereof.

[Explanation of symbols]

10 ... Semiconductor processing liquid 12 ... Tank 20, 30 ...
Detection rods 22, 32 ... Temperature sensor with heater (RS1 ... Sensor element, RH ... Heater element) 24, 34 ... Temperature sensor (RS2 ... Sensor element) 2
8, 38 ... Detection circuit 41 ... Ceramic substrate PRS ... Resistance pattern PRH
Heat generation pattern 43 Glass tube 45 Press fit seal 47 Glass seal 49 Teflon film 51 Fixing member 55 Constant current circuit 57 Judgment circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tashiro Arai 5-20-2 Nishigotanda, Shinagawa-ku, Tokyo Nihon Pneumatic Systems Co., Ltd.

Claims (5)

[Claims] 1. A long detection rod disposed in a tank for storing a liquid in a direction orthogonal to a liquid surface of the liquid, and a lower end portion of the detection rod and a position above the lower end portion, respectively. Based on a pair of temperature sensors provided and a detection signal from the pair of temperature sensors, a determination circuit for determining whether or not the lower end portion of the detection rod contacts the liquid and is cooled by heat conduction of the liquid And a liquid level detecting device. 2. A long detection rod arranged in a direction orthogonal to a liquid surface of a liquid in a tank for storing the liquid, and a heater for heating provided at a lower end portion of the detection rod. Temperature sensor, a temperature sensor provided at an arbitrary position including the lower end portion of the detection rod, and the lower end portion of the detection rod comes into contact with the liquid based on the detection signals from the temperature sensors to heat the liquid. A liquid level detection device comprising: a determination circuit for determining whether or not the liquid is cooled by conduction. 3. A temperature sensor equipped with the above heater, on a ceramic substrate, a resistance pattern whose resistance value changes according to temperature is formed, and between the resistance patterns, a heating pattern for generating heat by energization is formed. The liquid level detecting device according to claim 2, wherein the liquid level detecting device is manufactured by 4. The detection rod is made of a long tubular member made of a material having corrosion resistance to liquid, and also made of a material having corrosion resistance, and the lower end portion of the tubular member is sealed so that the liquid inside the tubular member is sealed. A seal member for preventing intrusion, wherein the pair of temperature sensors are arranged inside the tubular member sealed by the seal member. Liquid level detector described. 5. The liquid level detecting device according to claim 4, wherein a temperature sensor disposed at a lower end portion of the detection rod is joined to the seal member.