Sensor

Abstract

A sensor used in a gasifier is configured from one or more sensor elements, a first flow path for conveying a fluid from the outside of the sensor to the position of the sensor element, and a second flow path for returning the fluid conveyed by the first flow path to the position of the sensor element to the outside of the sensor. A fluid that is not a gas obtained by vaporizing a precursor by the vaporizer is used as the fluid. As a result, a sensor that can be continuously used over a long period of time at a temperature exceeding the maximum use temperature of the sensor elements constituting the sensor is provided. A portion of an inert gas for purging the interior of the housing of the gasifier may be used as the fluid. In addition, a protective tube, one end of which is closed and the other end of which is open, may be provided, and the sensor element is disposed in the protective tube. In this case, the sensor element is disposed in at least one of the first flow path and the second flow path. It is preferable that at least one of the members constituting the first flow path and the members constituting the second flow path is made of a material having a lower thermal conductivity than the thermal conductivity of the members constituting the protective tube.

Description

Technical Field

[0001] The present invention relates to sensors for use at high temperatures. Background Art

[0002] In the manufacturing process of semiconductor devices such as integrated circuits, various types of semiconductor material gases (hereinafter referred to as "material gases") are used depending on the purpose of the process. Among the material gases, a material gas in which a precursor is stored in a liquid or solid state is converted into a material gas in a gaseous state using a vaporizer, and then the material gas is supplied to a semiconductor manufacturing device via a pipe. As a means of generating a material gas from a precursor in a vaporizer, for example, a method of generating vapor by heating a precursor stored in a tank can be cited.

[0003] In addition, with the advancement of integrated circuit manufacturing technology, the chances of using new material gases that have lower equilibrium vapor pressures than conventional material gases and are therefore less likely to vaporize have increased (see, for example, Patent Document 1). When using such new material gases, there is a risk that if the temperature of the material gas decreases during the process of supplying the material gas from the vaporizer to the semiconductor manufacturing device, the material gas condenses or sublimates and returns to the state of a liquid or solid precursor, or the precursor attached to the inner wall of the material gas flow path dries and solidifies, and then peels off from the inner wall to become particles. Therefore, in order to prevent condensation and solidification of the material gas in the flow path, attempts have been made to set a heater around the material gas flow path to heat the flow path.

[0004] As described above, recently, there is a tendency that the temperature of the precursor and / or material gas in the vaporizer becomes higher and higher.

[0005] On the other hand, a vaporizer is usually equipped with a valve for starting or stopping the supply of the generated material gas, a flow control device for controlling the flow rate of the material gas, and various sensors for detecting the amount of the precursor and the properties of the material gas (such as temperature and pressure, etc.). For example, in a liquid level sensor for detecting the amount of a precursor in a liquid state, a sensor element such as a Hall IC or a reed switch is used to enable the liquid level of the precursor to be detected. Not limited to Hall ICs and reed switches, many sensor elements have an upper limit value of the operating temperature that can be used for a long time while maintaining normal operation, that is, the maximum operating temperature.

[0006] For example, a semiconductor element having a pn junction formed by bonding a p-type semiconductor and an n-type semiconductor has a property that the conductivity changes greatly depending on the surrounding environment, and therefore is widely used as a sensor. A sensor using a semiconductor element is called a semiconductor sensor. Among semiconductor sensors, there are various sensors such as temperature sensors, light sensors, magnetic field sensors, pressure sensors, and acceleration sensors, but they are not limited to these sensors.

[0007] Patent document 2 applied by the present applicant discloses the invention of a liquid level sensor for detecting the liquid level. The liquid level sensor comprises: a sleeve arranged in a vertical direction; a float configured to move along the sleeve as the liquid level changes; a resistor array; and a plurality of grounding units, which are composed of a Hall IC as a semiconductor sensor. The Hall IC functions as a magnetic field sensor, detects the magnetic field generated by the magnet provided by the float, and grounds the resistor array at the position where the float is located. In this structure, the electrical signal generated in the resistor array changes according to the change of the liquid level, so the liquid level can be detected by extracting the electrical signal.

[0008] The temperature of the pn junction of a semiconductor element is called the "junction temperature". If the junction temperature exceeds a certain limit temperature, many electron-hole pairs will be generated, and the semiconductor element will no longer be able to operate normally. This limit temperature is called the "maximum junction temperature". The maximum junction temperature of a typical semiconductor element is about 170°C when temporarily heated. However, in order to ensure the long-term reliability of the semiconductor sensor, it is recommended to maintain the temperature of the pn junction (junction temperature) at a temperature not exceeding a specified temperature (for example, 100°C) that is sufficiently lower than the maximum junction temperature. When the semiconductor sensor is used continuously for a long time in an environment where the junction temperature exceeds such a specified temperature, it is necessary to replace the semiconductor sensor with an unused semiconductor sensor at a shorter period in order to prevent the occurrence of malfunctions.

[0009] In addition, the multiple grounding units of the liquid level sensor may be composed of a reed switch instead of a Hall IC as a semiconductor sensor as described above. As known to those skilled in the art, a reed switch is composed of two magnetic reeds whose free ends are held at a predetermined interval inside a glass tube or the like. Furthermore, if a magnetic field is applied from the outside, the reeds are magnetized, and the free ends of each other attract each other and contact, closing the circuit. If the magnetic field disappears, the free ends of each other separate due to the elasticity of the reeds, opening the circuit.

[0010] Thus, for example, if the temperature of the reed switch reaches a temperature exceeding the Curie temperature of the material constituting the reed, the magnetism of the reed changes, and the reed switch may no longer operate normally. In addition, at certain temperatures, the elastic modulus of the material constituting the reed changes, and the reed switch may no longer operate normally.

[0011] Thus, not only semiconductor sensors, but also many sensor elements including reed switches have an upper limit value of the operating temperature that can be used for a long time while maintaining normal operation, that is, the maximum operating temperature. Therefore, in order to continue to use the sensor for a long time without replacing the sensor, it is preferable to maintain the operating temperature of the sensor in a manner that does not exceed the maximum operating temperature of the sensor element.

[0012] Prior art literature

[0013] Patent Literature

[0014] Patent Document 1: Japanese Patent Application Publication No. 2009-74108

[0015] Patent Document 2: International Publication No. 2022 / 004739 Summary of the invention

[0016] Problem that the invention aims to solve

[0017] As described above, in order to continuously use the sensor for a long period of time without replacing the sensor, it is preferable to maintain the operating temperature of the sensor in a manner not exceeding the maximum operating temperature of the sensor element. However, in some uses of the sensor, there is a need to continuously use the sensor at a higher temperature exceeding the maximum operating temperature. As an example, a liquid level sensor having the above-mentioned Hall IC or reed switch is sometimes provided in a tank of a vaporizer. As described above, a vaporizer is a device used for the purpose of supplying material gas to a semiconductor manufacturing device or the like. A liquid material that is a precursor to become a source of the material gas is stored in the tank of the vaporizer, and the liquid level of the liquid material is measured by a liquid level sensor.

[0018] In the case where a method of heating the liquid material stored in a tank is adopted as a method of vaporizing the material gas, generally, the liquid level sensor in contact with the liquid material in the tank will also be heated to the same temperature as the liquid material. Among the liquid materials, there are liquid materials that cannot obtain the vapor pressure required for the supply of the material gas unless heated to a temperature exceeding the maximum operating temperature of the sensor element. However, as described above, from the perspective of ensuring the long-term reliability of the sensor, it is necessary to maintain the operating temperature of the sensor in a manner that does not exceed the maximum operating temperature of the sensor element. For example, in a vaporizer having a liquid level sensor composed of a semiconductor element having a pn junction, from the perspective of ensuring long-term reliability, there is the following problem: the liquid material cannot be heated and vaporized at a temperature exceeding a specified temperature (e.g., 100°C) that is sufficiently lower than the maximum junction temperature.

[0019] The present invention has been made in view of the above-mentioned problems, and one object of the present invention is to provide a sensor that can be used continuously for a long period of time at a temperature exceeding the maximum operating temperature of a sensor element constituting the sensor.

[0020] Solutions for solving problems

[0021] The present invention provides a sensor used in a vaporizer, wherein the sensor comprises: one or more sensor elements; a first flow path for conveying a fluid from the outside of the sensor to the position of the sensor element; and a second flow path for returning the fluid conveyed by the first flow path to the position of the sensor element to the outside of the sensor. In addition, the fluid is not a gas obtained by vaporizing a precursor using a vaporizer.

[0022] In this structure, the sensor element is cooled by the fluid circulating in the first flow path and the second flow path. Thus, even if the temperature outside the sensor rises to a temperature exceeding the maximum operating temperature of the sensor element, the temperature of the sensor element can be kept lower than the temperature outside the sensor.

[0023] In a preferred embodiment, the sensor of the present invention further includes a protective tube having one end closed and the other end open, and the sensor element is arranged in the protective tube. In this case, at least one of the components constituting the first flow path and the components constituting the second flow path can be formed using a material having a thermal conductivity lower than that of the components constituting the protective tube. In this structure, heat is not easily transferred from the outside to the inside of the protective tube, so the temperature rise of the sensor element can be more reliably suppressed. In addition, the sensor of the present invention can be configured as a liquid level sensor used in a vaporizer.

[0024] Effects of the Invention

[0025] As described above, in the present invention, the sensor element is cooled by the fluid circulating in the first flow path and the second flow path. Thus, even if the temperature outside the sensor rises to a temperature exceeding the maximum operating temperature of the sensor element, the temperature of the sensor element can be kept lower than the temperature outside the sensor. Therefore, the temperature of the sensor equipped with the sensor element, which is used continuously for a long time, can be set to a higher temperature than before. Thus, the operating temperature of the vaporizer using the liquid level sensor equipped with the sensor element can be set to a temperature higher than the maximum operating temperature of the sensor element. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram showing an example of the structure of the sensor of the present invention in the first embodiment of the present invention.

[0027] Figure 2 It is a schematic diagram illustrating the structure of a sensor according to a preferred first embodiment of the present invention.

[0028] Figure 3 It is a schematic diagram illustrating the structure of a sensor according to a second embodiment of the present invention.

[0029] Figure 4 It is a partial cross-sectional view showing an example of the liquid level sensor of the present invention.

[0030] Figure 5 It is an assembly diagram showing an example of the liquid level sensor of the present invention.

[0031] Figure 6 This is a front view showing an example of the main part of the liquid level sensor of the present invention.

[0032] Figure 7 This is a partial cross-sectional view showing an example of a liquid level sensor according to the prior art. DETAILED DESCRIPTION

[0033] The following description and drawings illustrate examples of specific embodiments of the present invention, but the specific embodiments of the present invention are not limited to the embodiments shown in the following description and drawings.

[0034] <First embodiment>

[0035] In the first embodiment, the present invention is an invention of a sensor used in a vaporizer, wherein the sensor comprises: one or more sensor elements; a first flow path, which is a flow path for transporting a fluid from the outside of the sensor to the position of the sensor element; and a second flow path, which is a flow path for returning the fluid transported by the first flow path to the position of the sensor element to the outside of the sensor, and the sensor uses a fluid that is not a gas obtained by vaporizing a precursor using the vaporizer as the above-mentioned fluid.

[0036] The sensor element of the sensor of the present invention is, for example, an element for detecting the amount of precursor of the material gas stored in a tank or the like disposed inside the vaporizer or the properties of the material gas (e.g., temperature and pressure, etc.). As mentioned above, many sensor elements have an upper limit value of the operating temperature that can be used for a long time while maintaining normal operation, i.e., the maximum operating temperature. Therefore, in order to continue to use the sensor for a long time at a temperature higher than the maximum operating temperature of the sensor element without replacing the sensor, it is necessary to maintain the operating temperature of the sensor element in a manner that does not exceed the maximum operating temperature.

[0037] As a specific example of the sensor element as described above, for example, semiconductor elements headed by Hall IC and reed switches can be cited. The semiconductor element possessed by the sensor of the present invention is a semiconductor element with a pn junction. As mentioned above, the semiconductor element with a pn junction has the property that the conductivity changes greatly depending on the surrounding environment, so it can function as a sensor. As the semiconductor element of the present invention, for example, a light sensor, a magnetic field sensor, a pressure sensor, and an acceleration sensor can be used, but the semiconductor element of the present invention is not limited to these sensors.

[0038] In addition, the semiconductor element included in the sensor of the present invention is not limited to a semiconductor element in which only the portion that functions as a sensor is composed of a semiconductor having a pn junction. For example, although the sensor element itself is not a semiconductor, an amplifier or other peripheral circuits attached to the sensor may be an element composed of a semiconductor, or both the sensor portion and the peripheral circuit portion may be an element composed of a semiconductor.

[0039] Furthermore, the number of sensor elements provided by the sensor of the present invention may be one, two, or more. When the sensor of the present invention has two or more sensor elements, all sensor elements may be of the same type, or different types of sensor elements may be mixed.

[0040] Figure 1 Schematic diagram showing an example of the structure of the sensor of the present invention in the first embodiment. Figure 1As illustrated, in the sensor 2s of the present invention, as described above, there are: a first flow path 3, which is a flow path for transporting fluid from the outside of the sensor 2s to the position of the sensor element 2; and a second flow path 4, which is a flow path for returning the fluid transported by the first flow path 3 to the position of the sensor element 2 to the outside of the sensor 2s. The first flow path 3 and the second flow path 4 only need to be composed of continuous spaces respectively, and the shapes of these spaces are not limited. The shape of the space constituting the first flow path 3 and the second flow path 4 is preferably a shape with small fluid resistance and not easy to hinder the flow of the fluid. The first flow path 3 and the second flow path 4 can be directly connected to each other at the position of the sensor element 2, or they can be connected as shown in the figure. Figure 1 As shown in the example, they are indirectly connected via a transition portion that is neither the first flow path 3 nor the second flow path 4. The first flow path 3 and the second flow path 4 may each be a single system, or each may be branched in the middle to be divided into a plurality of systems, or may be merged again afterwards.

[0041] The first flow path 3 is a flow path that transports the fluid from the outside of the sensor 2s to the position of the sensor element 2. However, the first flow path 3 itself does not necessarily need to reach the position of the sensor element 2 from the outside of the sensor 2s. For example, in the case where there is another flow path that guides the fluid to be transported to the position of the sensor element 2 from the outside to the inside of the sensor 2s, the fluid can be transported from the outside of the sensor 2s to the position of the sensor element 2 via the other flow path and the first flow path 3. In addition, even if the end of the first flow path 3 on the sensor element 2 side does not reach the position of the sensor element 2, it is sufficient as long as the flow of the fluid released from the first flow path 3 reaches the sensor element 2 to produce a cooling effect.

[0042] On the other hand, the second flow path 4 is a flow path that returns the fluid delivered to the position of the sensor element 2 by the first flow path 3 to the outside of the sensor 2s. However, the second flow path 4 itself does not necessarily need to reach the outside of the sensor 2s from the position of the sensor element 2. For example, in the case where there is another flow path that guides the fluid delivered to the position of the sensor element 2 from the inside to the outside of the sensor 2s, the fluid delivered to the position of the sensor element 2 by the first flow path 3 can also be returned to the outside of the sensor 2s via the flow path and the second flow path 4. In addition, even if the end of the second flow path 4 on the sensor element 2 side does not reach the position of the sensor element 2, it is sufficient as long as the flow of the fluid delivered to the position of the sensor element 2 by the first flow path 3 and heated by cooling the sensor element 2 leaves the position of the sensor element 2 and is guided to the outside of the sensor 2s via the second flow path 4.

[0043] Under the action of the above-mentioned first flow path 3 and second flow path 4, the fluid as the heat medium takes away heat from the sensor element 2 and releases the heat to the outside of the sensor 2s. In addition, for the first flow path 3 and the second flow path 4 of the present invention, either or both of them may be composed of independent tubular members, or the first flow path 3 and the second flow path 4 may be integrally composed of a single member.

[0044] When the sensor 2s of the present invention is operated to sense, Figure 1 As shown by the hollow arrow, fluid is supplied to the first flow path 3, and at the same time, Figure 1 As shown by the black arrow in the figure, the fluid is discharged or recovered from the second flow path 4. As described above, the fluid used when using the sensor 2s of the present invention is a fluid that is not a gas obtained by gasifying a precursor using a vaporizer to which the sensor 2s of the present invention is applied. As such a fluid, any fluid can be used as long as it has the effect of cooling the sensor element 2, and all fluids commonly used as refrigerants can be used. The fluid used to implement the present invention is preferably a stable substance that has a large heat capacity, is easy to handle, and is not prone to chemical reactions with the walls of the first flow path 3 and the second flow path 4. Specifically, as a fluid used to implement the present invention, an inert gas such as water, air or nitrogen is preferred. In order to obtain the cooling effect of the sensor element 2 of the present invention, the temperature of the fluid supplied to the sensor 2s needs to be a temperature lower than the temperature around the sensor element 2.

[0045] In the sensor 2s of the present invention having the above-mentioned structure, the sensor element 2 is in contact with the fluid transported by the first flow path 3 to the position of the sensor element 2. A portion of the heat transferred from the periphery of the sensor element 2 to the sensor element 2 is taken away from the position of the sensor element 2 to the outside by the flow of the fluid. In addition, usually, the sensor element 2 consumes very little power and generates less heat. Therefore, the temperature of the sensor element 2 is roughly consistent with the surrounding temperature, that is, the temperature of the fluid. As a result, even if the temperature around the sensor 2s is a temperature exceeding the maximum operating temperature of the sensor element 2, the temperature of the sensor element 2 can be maintained at a temperature lower than the temperature around the sensor 2s. Thus, it is possible to prevent malfunctions and / or the promotion of aging degradation associated with the temperature rise of the sensor element from happening. Therefore, according to the present invention, it is possible to provide a sensor 2s that can be used continuously for a long time at a temperature exceeding the maximum operating temperature of the sensor element 2 constituting the sensor 2s.

[0046] In addition, Figure 1 In the example shown, a sensor 2s having a sensor element 2 is arranged inside a tank 6 storing a precursor of a material gas supplied from a vaporizer (not shown). However, the arrangement of the sensor 2s in the vaporizer is not limited to Figure 1In the example shown, the sensor 2s can be arranged at an appropriate position such as the surface or the inside of a component of the vaporizer, depending on the physical quantity to be detected by the sensor 2s.

[0047] In addition, in the technical field, for example, a vaporizer for supplying a combustible material gas is known, in which the vaporizer is housed inside a housing for the purpose of explosion-proofing, and the inside of the housing is purged by flowing an inert gas into the housing. If the inert gas used for purging can also be used for cooling the sensor element in such a vaporizer, it is possible to suppress the complication of the structure of the vaporizer and / or the increase in manufacturing cost, which is therefore preferred.

[0048] Therefore, in a preferred first embodiment, the sensor of the present invention is based on the above-mentioned sensor, wherein at least the component equipped with the sensor among the components constituting the vaporizer is housed inside the shell, the vaporizer is configured to purge the interior of the shell by allowing an inert gas to flow into the interior of the shell, and the sensor is configured so that at least a portion of the inert gas flows in the first flow path and the second flow path as the above-mentioned fluid.

[0049] As specific examples of the inert gas used as the fluid for cooling the sensor element in this embodiment, for example, argon gas and nitrogen gas can be cited, but nitrogen gas is preferred from the viewpoint of reducing the operating cost. In addition, in this embodiment, the vaporizer is already equipped with a mechanism for supplying the inert gas from the outside of the housing to the inside and discharging the inert gas from the inside of the housing to the outside. Therefore, by supplying the inert gas for purging to the first flow path from the supply flow path of the inert gas for purging and discharging the inert gas from the second flow path via the discharge flow path of the inert gas for purging, it is possible to easily construct a flow path for the fluid for cooling the sensor element.

[0050] Figure 2 Schematic diagram illustrating the structure of a sensor according to a preferred first embodiment of the present invention. Figure 2 In the example shown in (a), the sensor 2s is arranged inside the tank 6 constituting the vaporizer not shown, and the tank 6 is accommodated inside the housing 10. In addition, the first flow path 3 branches from the supply flow path 11 for supplying the inert gas for purge to the inside of the housing 10, and the second flow path 4 merges with the exhaust flow path 12 for exhausting the inert gas for purge. Thus, a part of the inert gas can flow in the first flow path 3 and the second flow path 4 as a fluid for cooling the sensor element 2.

[0051] On the other hand, Figure 2 In the example shown in (b), the sensor 2s is arranged inside the tank 6 and the tank 6 is accommodated inside the housing 10. Figure 2The example shown in (a) is the same. However, in Figure 2 In the example shown in (b), the supply flow path 11 for supplying the inert gas for purge to the inside of the housing 10 is directly connected to the first flow path 3, and all the inert gas is supplied to the first flow path 3. In addition, the fluid that has passed the position of the sensor 2 is discharged from the second flow path 4 to the inside of the housing 10, and after passing through the space inside the housing 10, it is discharged from the discharge flow path 12 for discharging the inert gas for purge to the outside of the housing 10. Thus, all the inert gas can flow in the first flow path 3 and the second flow path 4 as a fluid for cooling the sensor element 2.

[0052] As a result, according to this embodiment, the vaporizer can be used continuously for a long period at a temperature exceeding the maximum use temperature of the sensor element constituting the sensor, and the complication of the structure of the vaporizer and the increase in the manufacturing cost can be suppressed.

[0053] In a preferred first embodiment, the sensor of the present invention further comprises a unit for supplying a fluid to the first flow path. For example, when the fluid is a compressed gas filled in a gas cylinder, the unit for supplying the fluid to the first flow path can be constituted by a pressure reducing valve connected to the gas cylinder and adjusting the pressure of the gas to an appropriate value and a pipe for continuously supplying the gas to the first flow path maintained at a relatively low pressure. Alternatively, when the fluid is a liquid or a relatively low-pressure gas, the unit for supplying the fluid to the first flow path can be constituted by a unit such as a pump for forcibly feeding the fluid to the first flow path.

[0054] After the fluid supplied to the first flow path is transported to the position of the sensor element, it is discharged to the outside from the outlet of the second flow path. The fluid discharged to the outside can be directly discharged into the atmosphere, or it can be recovered using components such as piping and vacuum pumps. The recovered fluid can be directly discarded or reused after cooling.

[0055] In a preferred first embodiment, the semiconductor sensor of the present invention includes a temperature sensor at or near the position of the sensor element. In this configuration, by monitoring the temperature of the sensor element with the temperature sensor, it is possible to monitor whether the temperature of the sensor element does not exceed a target value.

[0056] <Second embodiment>

[0057] In a second embodiment, the present invention is an invention of a sensor, which is based on the sensor of the first embodiment described above, wherein the sensor further includes a protective tube having one end closed and the other end open, and the sensor element is arranged inside the protective tube. In addition, the first flow path is configured to transport the fluid from the position of the other end of the protective tube to the position of the endmost sensor element, which is the sensor element closest to one end of the protective tube among the sensor elements. Moreover, the second flow path is configured to return the fluid transported by the first flow path to the position of the endmost sensor element to the position of the other end. In addition, the sensor element is arranged in at least one of the first flow path and the second flow path.

[0058] Figure 3 It is a schematic diagram illustrating the structure of a sensor according to a second embodiment of the present invention. Figure 3 The protection tube 1 included in the sensor 2s illustrated in (a) is a straight tubular member, and the sensor element 2 is arranged inside the protection tube 1. Figure 3 In the example shown in (a), a plurality of sensor elements 2 are fixed to the surface of the holding member 2h. The protective tube 1 preferably has a sufficient space inside thereof to accommodate the sensor element 2 and other components. The protective tube 1 protects the sensor element 2 by isolating the built-in sensor element 2 from the external environment. One end of the protective tube 1 (at Figure 3 The other end of the protective tube 1 (the lower end in the figure) is closed, thereby preventing the external environment from entering the interior of the protective tube 1. Figure 3 The upper end in the middle is open, and an electrical signal can be exchanged with the sensor element 2 or a fluid for cooling the sensor element 2 can be delivered to the position of the sensor element through the open end.

[0059] The protection tube 1 of the second embodiment is preferably made of stainless steel or other metals or alloys. The thickness of the tube wall of the protection tube 1 should not be too thin to ensure the strength for maintaining the shape of the protection tube 1, and should not be too thick to hinder the collection of information about the external environment. The protection tube 1 preferably has a sufficient length to allow the sensor element 2 to reach the position to be sensed.

[0060] exist Figure 3 In the sensor 2s illustrated in (a), the first flow path 3 is configured to transport the fluid from the position of the open end (the other end) of the protection tube 1 to the position of the endmost sensor element, which is the sensor element 2 closest to the closed end (the one end) of the protection tube 1 among the sensor elements 2. On the other hand, the second flow path 4 is configured to return the fluid transported by the first flow path 3 to the position of the endmost sensor element to the position of the open end (the other end) of the protection tube 1.

[0061] Figure 3 The first flow path 3 illustrated in (a) delivers the fluid from the position of the open end of the protection tube 1 to the position of the endmost sensor element 2 closest to the closed end of the protection tube 1 among the sensor elements 2. Here, the endmost sensor element closest to the closed end of the protection tube 1 refers to the sensor element located farthest from the open end of the protection tube 1. By delivering the fluid to the position of the endmost sensor element using the first flow path 3, all the sensor elements 2 can be cooled. Figure 3 The sensor 2s illustrated in (a) includes a plurality of sensor elements 2. However, when the number of the sensor element 2 is one, it is sufficient for the first flow path 3 to guide the fluid to the position of the one sensor element.

[0062] As described above, the first flow path 3 does not need to reach the position of the sensor element 2, as long as the flow of the fluid discharged from the first flow path 3 reaches the sensor element 2 to produce a cooling effect. In addition, in the second embodiment, the sensor element is arranged in at least one of the first flow path and the second flow path. In the case where the endmost sensor element is arranged in the second flow path 4, the fluid that passes through the first flow path 3 and is transported to a position close to the closed end of the protection tube 1 may then enter the second flow path 4, and the fluid reaches the endmost sensor element inside the second flow path and is cooled. In this way, the situation where the first flow path as a whole and a part of the second flow path cooperate to transport the fluid to the endmost sensor element is also included in the embodiment of the first flow path of the present invention.

[0063] As described above, the second flow path of the present invention is a flow path that returns the fluid transported by the first flow path to the position of the sensor element to the outside of the sensor. The second flow path of the second embodiment returns the fluid transported by the first flow path to the position of the sensor element at the end to the position of the open end of the protection tube. Since one side of the protection tube is closed, it is necessary to return the fluid transported by the first flow path to the position of the sensor element at the end to the outside of the protection tube again. The second flow path functions as a path for returning the fluid to the outside of the protection tube. Under the action of the first flow path and the second flow path, the fluid as a heat medium takes heat from the sensor element and releases heat to the outside of the protection tube.

[0064] As described above, the first flow path and the second flow path of the present invention may be either or both formed by independent tubular members, or the first flow path and the second flow path may be formed integrally by a single member. Alternatively, either the first flow path or the second flow path may be formed by the inner wall of the protective tube.

[0065] exist Figure 3In the sensor 2s illustrated in (a), the bottomed cylindrical second flow path 4 having one end closed and the other end open is housed inside the protective tube 1 with its closed end facing the closed end side of the protective tube 1. Furthermore, a plurality of sensor elements 2 fixed to the retaining member 2h and the cylindrical first flow path 3 are housed inside the second flow path 4, and near the bottom of the protective tube 1, the endmost sensor element 2 and the downstream end of the first flow path 3 are close to each other. Therefore, in Figure 3 In the sensor 2s illustrated in (a), the fluid supplied to the upstream end of the first flow path 3 flows out from the downstream end of the first flow path 3 to the bottom of the second flow path 4 as indicated by the hollow arrow. And, the endmost sensor element 2 among the plurality of sensor elements 2 located near the bottom of the second flow path 4 (i.e., near the closed end of the protection tube 1) is first cooled by the fluid. Then, as the fluid flows along the second flow path 4 to the downstream side ( Figure 3 The other sensor elements 2 are also cooled by the contact with the fluid. As shown by the black arrow, the second flow path 4 flows from the downstream end (at the top of the second flow path 4). Figure 3 The fluid is discharged to the outside of the sensor 2s (the upper end in the middle).

[0066] on the other hand, Figure 3 The sensor 2s illustrated in (b) is similar to the above-mentioned sensor in that the second flow path 4 as an independent component is not accommodated in the protection tube 1 and does not include the second flow path 4 as an independent component. Figure 3 The sensor 2s illustrated in (a) has a different structure. Figure 3 In the sensor 2s illustrated in (b), the fluid supplied to the upstream end of the first flow path 3 flows out from the downstream end of the first flow path 3 toward the bottom of the protection tube 1 as indicated by the hollow arrow. And, among the plurality of sensor elements 2, the endmost sensor element 2 located near the bottom of the protection tube 1 (i.e., near the closed end of the protection tube 1) is first cooled by the fluid. Then, as the fluid flows along the space inside the protection tube 1 toward the downstream side ( Figure 3 The other sensor elements 2 are also cooled by the contact with the fluid, as shown by the black arrows, from the open end of the protection tube 1 (at the top of the Figure 3 The fluid is discharged to the outside of the sensor 2s (the upper end in FIG. 1 ). Figure 3 In the example shown in (b), the space inside the protection tube 1 functions as the second flow path 4.

[0067] exist Figure 3In the example shown, all sensor elements are arranged in the second flow path, but as mentioned above, in the sensor of the second embodiment, the sensor elements are arranged in at least one of the first flow path and the second flow path. Here, the sensor elements are arranged in the first flow path or the second flow path, which means that all sensor elements including the sensor elements at the end are present inside the first flow path or the second flow path, and the surface of the sensor element or its shell is in a state of contact with the fluid flowing in the first flow path or the second flow path and taking away heat. In the second embodiment, all sensor elements are arranged in at least one of the first flow path and the second flow path, and there is no sensor element that is not arranged in either the first flow path or the second flow path. In the case where there are more than two sensor elements, all sensor elements may be arranged in only one of the first flow path and the second flow path, or may be dispersedly arranged in both the first flow path and the second flow path.

[0068] In the sensor of the preferred second embodiment, at least one of the components constituting the first flow path and the components constituting the second flow path is composed of a material having a thermal conductivity lower than that of the components constituting the protection tube. As described above, the fluid flowing in the first flow path and the second flow path functions as a heat medium that suppresses the temperature rise of the sensor element. However, since the temperature outside the protection tube is higher than the temperature of the fluid, the fluid is heated by the heat from the outside of the protection tube, and the temperature of the fluid may rise before the fluid is transported to the position of the sensor element. If at least one of the components constituting the first flow path and the second flow path is composed of a material having a thermal conductivity lower than that of the components constituting the protection tube, the heat outside the protection tube is not easily transferred to the fluid, so the temperature rise of the fluid can be hindered and the original cooling function can be exerted.

[0069] In the preferred second embodiment, the constituent material of at least one of the members constituting the first flow path and the second flow path may be any material as long as it has a thermal conductivity lower than that of the member constituting the protection tube. For example, in the case where the protection tube is made of metal or alloy as described above, by constituting at least one of the first flow path and the second flow path with polytetrafluoroethylene or other fluororesin having a thermal conductivity lower than that of the protection tube, the rise in the temperature of the fluid can be suppressed. In at least one of the first flow path and the second flow path, the entire flow path may be made of a material having a thermal conductivity lower than that of the protection tube, or a part of the flow path may be made of a material having a thermal conductivity lower than that of the protection tube. For example, in the case where the flow path is composed of a plurality of members, even if a part of these members has a thermal conductivity higher than that of the member constituting the protection tube, if the thermal conductivity of the other parts is low, the rise in the temperature of the fluid as a whole can be suppressed.

[0070] In the preferred second embodiment, the first flow path and the second flow path themselves may be composed of a material having a low thermal conductivity. Alternatively, the flow path may be a structure in which a plurality of tubes are overlapped in layers, and a material having a low thermal conductivity is used in a portion of these layers. Alternatively, the protective tube may have a double structure consisting of an outer tube and an inner tube, and the gap between the two is a vacuum. The space maintained as a vacuum is one of the embodiments of "a material having a thermal conductivity lower than the thermal conductivity of the components constituting the protective tube" in the present invention. Furthermore, the protective tube may have a double structure consisting of an outer tube and an inner tube, and the constituent material of at least one of the components constituting the first flow path and the second flow path is a material having a thermal conductivity lower than the thermal conductivity of the components constituting the protective tube.

[0071] In a preferred second embodiment, the first flow path of the sensor of the present invention is arranged inside the second flow path. Here, the first flow path being arranged inside the second flow path means that, in the cross section of the protective tube, the components constituting the first flow path exist inside the components constituting the second flow path and are in a position in contact with the fluid flowing in the second flow path. In this structure, the fluid is first transported to the position of the sensor element at the end through the first flow path arranged inside the second flow path, and then returns to the position of the open end of the protective tube through the second flow path. All sensor elements including the sensor element at the end are arranged in at least one of the first flow path and the second flow path, and therefore come into contact with the fluid flowing in these flow paths. In this structure, the outside of the first flow path is surrounded by the fluid flowing in the second flow path, so the heat of the outside of the protective tube is not directly transferred to the fluid flowing in the first flow path. As a result, the temperature rise of the fluid flowing in the first flow path can be suppressed, and thus the effect of the fluid cooling the sensor element can be improved. In addition, as mentioned above, in Figure 3 In the sensor 2s illustrated in (a), the first flow path 3 is arranged inside the second flow path 4. That is, Figure 3 The sensor 2s illustrated in (a) satisfies the requirements for being a sensor of this preferred embodiment.

[0072] <Third Embodiment>

[0073] In a third embodiment, the present invention is an invention of a liquid level sensor, which is used in a vaporizer, wherein the liquid level sensor comprises: a protective tube, one end of which is closed and the other end is open, and the protective tube is arranged in a manner extending in a vertical direction; one or more sensor elements, which are arranged inside the protective tube; a first flow path, which is a flow path configured to transport a fluid from the position of the other end (open end) of the protective tube to the position of the endmost sensor element, and the endmost sensor element is the sensor element closest to the endmost sensor element. A sensor element at the above-mentioned one end (closed end) of the protective tube; a second flow path, which is a flow path configured to return the fluid transported by the first flow path to the position of the sensor element at the endmost end to the position of the above-mentioned other end (open end) of the protective tube; and a float, which has a magnet and is configured to move along the protective tube as the liquid level of a precursor changes, and the precursor becomes a gas by being vaporized by the vaporizer, the sensor element is arranged in at least one of the first flow path and the second flow path, and the fluid is not a fluid obtained by vaporizing the above-mentioned precursor using the vaporizer.

[0074] In this embodiment, the protective tube is disposed in the vertical direction and is arranged in a manner that the length direction is consistent with the direction perpendicular to the liquid surface of the liquid (the precursor of the material gas to be supplied by the vaporizer) whose liquid level is to be known. The float equipped with a magnet moves along the protective tube as the liquid level changes. The sensor element responds to the magnetic field generated by the magnet and performs on-off actions. By detecting it as an electrical signal, the position of the liquid surface where the float is located can be known. As specific examples of such sensor elements, for example, Hall IC and reed switch can be cited. However, the sensor element used in this embodiment is not particularly limited as long as it can know the position of the liquid surface where the float is located by outputting a signal corresponding to the magnetic field generated by the magnet.

[0075] The effect of causing the fluid to flow through the first flow path and the second flow path in this embodiment is the same as that in the first and second embodiments, that is, by maintaining the temperature of all sensor elements including the endmost sensor element at a temperature lower than the temperature outside the protection tube, malfunction and aging degradation associated with the temperature rise of the sensor element are prevented from occurring. The preferred embodiments of the protection tube, the first flow path, the second flow path, etc. in the third embodiment are the same as those in the second embodiment, and therefore description thereof is omitted here.

[0076] The liquid level sensor of the third embodiment can be used as a liquid level sensor of a tank provided in a vaporizer. As described above, in the case where a method of heating a liquid material (precursor) stored in a tank is adopted as a method of vaporizing the material gas in the vaporizer, the liquid level sensor in contact with the liquid material in the tank is usually also heated to the same temperature as the liquid material. Among liquid materials, there are liquid materials that cannot obtain the vapor pressure required for supplying the material gas unless heated to a temperature exceeding the maximum operating temperature of the sensor element (for example, 100°C). If the liquid level sensor of the third embodiment is used, even if the liquid material is heated to a temperature exceeding the maximum operating temperature of the sensor element, the temperature of the sensor element can be maintained at a temperature lower than the temperature of the liquid material, thereby ensuring the long-term reliability of the sensor and increasing the vapor pressure of the material gas.

[0077] The third embodiment described above is limited to the embodiment of the liquid level sensor, but the embodiment of the present invention is not limited to the liquid level sensor. The effect of the present invention can also be obtained by replacing the semiconductor sensor in the first embodiment with an optical sensor, a magnetic field sensor, a pressure sensor, an acceleration sensor, etc. within the scope of the present invention.

[0078] Example

[0079] Hereinafter, a specific embodiment of the present invention will be described with reference to the accompanying drawings, taking a liquid level sensor used in a vaporizer as an example. In addition, the following description is merely an example of a specific embodiment of the present invention, and the present invention is not limited to the scope of the following embodiments.

[0080] Figure 7 This is a partial cross-sectional view showing an example of the structure of a vaporizer of a liquid level sensor having the prior art disclosed in Patent Document 1. The liquid level sensor comprises: a protective tube 1, which is entirely arranged inside a tank 6, one end of the protective tube 1 is closed and the other end is open, and the protective tube 1 is arranged in a manner extending in a vertical direction; two or more Hall ICs (semiconductor elements) 2, which have a pn junction and are arranged inside the protective tube 1; and a float 5, which has a magnet 5a and is configured to move along the protective tube as the liquid level changes. The interior of the tank 6 is filled with a liquid material, and the liquid material is heated by a heater not shown, whereby the liquid material is vaporized to generate a gas. That is, the liquid material is a precursor of the material gas to be supplied by the vaporizer. The temperature of the liquid material is measured by a temperature sensor 7. However, in Figure 7 In the figure, only the port for inserting the top end of the temperature sensor 7 into the inside of the tank 6 is shown. The generated gas accumulates in the space above the liquid surface inside the tank 6. The gas stored in the inside of the tank 6 can be taken out of the tank 6 using a pipe not shown in the figure and used for various purposes.

[0081] The Hall IC (semiconductor element) 2 is configured to ground the connection point of the resistor array composed of a plurality of resistors connected in series. The Hall IC (semiconductor element) 2 operates due to the magnetic field generated by the magnet 5a, so that the resistance value of the resistor array changes. By taking out the electrical signal corresponding to the resistance value, the position of the liquid surface of the liquid material can be detected.

[0082] In having Figure 7 In the vaporizer of the structure, the protection tube 1 is made of stainless steel. Air exists around the Hall IC (semiconductor element) 2 inside the protection tube 1. The liquid material stored in the tank 6 is heated for the purpose of generating gas. If the temperature of the liquid material rises, the temperature of the outer wall of the protection tube 1 in contact with the liquid material rises first, and the heat is transferred to the inner wall of the protection tube 1 by conduction. Next, the heat is transferred from the inner wall of the protection tube 1 toward the Hall IC (semiconductor element) 2 by conduction, air convection, and electromagnetic radiation.

[0083] The closed end of the protection tube 1 is deeply inserted below the liquid surface of the tank 6, and the area around the protection tube 1 is filled with heated liquid material. The cross-sectional area of ​​the protection tube 1 is smaller than the area of ​​the outer peripheral surface, so the heat released to the outside from the Hall IC (semiconductor element) 2 arranged inside the protection tube 1 through the space on the inner diameter side of the protection tube 1 is less than the heat transferred from the outside of the protection tube 1 to the inside. Therefore, when the thermal equilibrium state is reached, the temperature of the Hall IC (semiconductor element) 2 will rise to a temperature roughly equal to the temperature of the liquid material. Therefore, in Figure 7 In the vaporizer of the prior art shown, the temperature of the liquid material cannot be increased to a temperature exceeding the maximum operating temperature (100° C.) of the Hall IC (semiconductor element) 2 in order to avoid damage to the Hall IC (semiconductor element) 2 and / or acceleration of aging.

[0084] Figure 4 is a partial cross-sectional view showing an example of the structure of a vaporizer equipped with a liquid level sensor of the present invention. The basic structure of the liquid level sensor is similar to Figure 7 The same as the prior art gasifier shown. That is, Figure 4The illustrated liquid level sensor comprises: a stainless steel protective tube 1 which is entirely disposed inside a tank 6, one end of the protective tube 1 being closed and the other end being open, and the protective tube 1 being disposed in a manner extending in a vertical direction; two or more Hall ICs (semiconductor elements) 2 which have a pn junction and are disposed inside the protective tube 1; and a float 5 which has a magnet 5a and is configured to move along the protective tube as the liquid level changes. In addition to the above-mentioned structure, the liquid level sensor of the present invention further comprises: a first flow path 3 which transports the fluid from the position of the open end of the protective tube 1 to the position of the most end Hall IC (most end sensor element) 2b in the Hall IC (semiconductor element) 2 which is closest to the closed end of the protective tube 1; and a second flow path 4 which returns the fluid transported by the first flow path 3 to the position of the most end Hall IC (most end semiconductor element) 2b to the position of the open end of the protective tube 1. Figure 4 In, also with Figure 7 Similarly, with respect to the temperature sensor 7 for measuring the temperature of the liquid material, only the port portion is shown.

[0085] exist Figure 4 In the embodiment, the first flow path 3 is arranged inside the second flow path 4. Figure 4 In the embodiment, the first flow path 3 is composed of a thin tube having an outer diameter sufficiently smaller than the inner diameter of the protection tube 1, and is arranged so as to extend vertically from the open end of the protection tube 1 toward the closed end. The position of the lower side of the first flow path 3, i.e., the end on the outlet side of the fluid, is located below the position of the endmost Hall IC (endmost sensor element) 2b closest to the closed end of the protection tube 1 among the plurality of Hall ICs (semiconductor elements) 2. The Hall IC (semiconductor element) 2 is not arranged inside the first flow path 3.

[0086] exist Figure 4 In the embodiment, the space inside the protective tube 1 from the top of the lower side of the first flow path 3 to the open end of the protective tube 1 except for the first flow path 3 constitutes the second flow path 4. All the Hall ICs (semiconductor elements) 2 are arranged in the second flow path 4. Figure 4 Omitted, but Figure 4 The liquid level sensor shown includes means for supplying fluid to the first flow path 3 .

[0087] In order to Figure 4 The liquid level sensor of the present invention shown in the figure works by first supplying a fluid from the top end of the upper side of the first flow path 3 using a supply unit not shown in the figure. The supplied fluid passes through the interior of the first flow path 3 and then descends, and then flows out from the top end of the lower side to the interior of the protection tube 1, that is, the second flow path 4. Next, the fluid rises in the second flow path 4 while contacting the array of Hall ICs (semiconductor elements) 2, and is discharged to the outside from the open end of the protection tube 1.

[0088] exist Figure 4 In the liquid level sensor of the present invention shown, as described above, a fluid flows inside the protective tube 1. The fluid flowing inside the protective tube 1 does not stay in one place but always flows, so even if the heat of the liquid material reaches the inner wall of the protective tube 1, there is no heat transfer path for further transferring the heat to the Hall IC (semiconductor element) 2. In addition, the fluid flowing in the first flow path 3 is surrounded by the fluid returning in the second flow path 4, so the temperature of the fluid flowing in the first flow path 3 will not rise due to the heat of the heated liquid material. In addition, due to the movement of the fluid, the system will never reach a thermal equilibrium state. Under these effects, according to Figure 4 The liquid level sensor of the present invention shown above can maintain the temperature of the Hall IC (semiconductor element) 2 at a temperature lower than the temperature of the liquid material.

[0089] Figure 5 Yes Figure 4 Assembly diagram of the vaporizer of the illustrated liquid level sensor. Figure 5 In the figure, a sleeve 4a with an outer diameter of 10.0 mm and an inner diameter of 9.0 mm and a plug 4b with an outer diameter of 9.0 mm that closes the top of the sleeve 4a are shown above a stainless steel protective tube 1 with an inner diameter of 10.8 mm. During assembly, the plug 4b is first inserted into the lower end of the sleeve 4a, and then the sleeve 4a is inserted until its lower end touches the closed end of the protective tube 1. The inner diameter of the sleeve 4a corresponds to the outer diameter of the second flow path 4. Next, a component in which a printed wiring board 2a with a row of Hall ICs (semiconductor elements) 2 and resistors and a thin and long capillary 3a constituting the first flow path 3 are fixed to each other is inserted into the interior of the sleeve 4a of the protective tube 1 and fixed using a fixing fixture.

[0090] Figure 6 4 is a front view illustrating a state where the sleeve 4a, the plug 4b, the printed wiring board 2a, and the capillary tube 3a constituting the first flow path 3 are assembled. Figure 6 In (a), a plug 4b is inserted into the lower end of the sleeve 4a. This is to prevent the fluid supplied to the lower end of the sleeve 4a through the first flow path 3 from entering the gap between the inner diameter of the protective tube 1 and the outer diameter of the sleeve 4a. The capillary 3a constituting the first flow path 3 and the sleeve 4a constituting the second flow path are both made of fluororesin with low thermal conductivity. The plug 4b is made of a sponge made of silicone resin. Figure 6 In (b), the lower end of the printed wiring board 2a is inserted into the sleeve 4a, and the capillary tube 3a constituting the first flow path 3 is also inserted.

[0091] In such Figure 6In the assembled state as shown in (b), the fluid descending in the first flow path 3 is released from the top of the capillary 3a to the inside of the sleeve 4a, and is stopped from descending by the plug 4b, so it rises toward the upper part of the sleeve 4a. Figure 6 As shown in (a), the lower end of the capillary 3a constituting the first flow path 3 is cut obliquely, so even if the top end contacts the plug 4b, the plug 4b will not hinder the release of the fluid. The fluid rising in the sleeve 4a is first transported to the position of the endmost Hall IC (endmost sensor element) 2b, then contacts other Hall ICs 2 one by one, and finally reaches the open end of the protection tube 1 and is released to the outside.

[0092] In this structure, the sleeve 4a constituting the outer wall of the second flow path 4 is made of fluororesin having a low thermal conductivity, so the heat of the inner wall of the protection tube 1 is not easily transferred to the fluid flowing in the second flow path 4. In addition, the capillary 3a of the first flow path 3 arranged inside the second flow path 4 is also made of fluororesin, and the plug 4b closing the top end of the sleeve 4a is made of silicone resin, so the heat of the protection tube 1 is hardly transferred to the fluid flowing in the first flow path 3. Therefore, the temperature of the fluid transported to the endmost Hall IC 2b is substantially the same as the temperature of the fluid supplied to the first flow path 3.

[0093] [Table 1]

[0094] Table 1

[0095]

[0096] Table 1 shows that while Figure 4 The data of the relationship between the flow rate of nitrogen gas and the temperature of each part when the tank 6 of the vaporizer shown is empty and the bottom of the tank 6 is heated by a heater (not shown) and the temperature detected by the temperature sensor 7 provided in the tank is controlled to 110°C while supplying nitrogen gas at room temperature to the first flow path 3. The temperature is measured at two locations: the inner diameter side of the position close to the open end of the protection tube 1 and the position of the Hall IC (semiconductor element) 2 located closest to the open end of the protection tube 1 in the row of the Hall IC (semiconductor element) 2. The temperature measurement is performed when the temperature of each part is stable after the flow rate of nitrogen gas is stabilized for about 10 minutes.

[0097] The left column of Table 1 indicates the existence Figure 5 and Figure 6Temperature data for the sleeve 4a and the plug 4b shown. It can be seen that when the flow rate of nitrogen is zero, the temperature of the protection tube 1 and the temperature of the Hall IC (semiconductor element) 2 are approximately equal, both exceeding 90°C. When nitrogen is flowing, the greater the flow rate, the lower the temperature of each part, and the greater the temperature difference between the two positions. From these results, it can be seen that if the liquid level sensor of the present invention is used, even when the temperature of the tank 6 exceeds 100°C, the temperature of the Hall IC (semiconductor element) 2 can be maintained at a lower temperature than it. In addition, it can be seen that by flowing nitrogen, not only the temperature of the Hall IC (semiconductor element) 2 but also the temperature of the protection tube 1 will drop.

[0098] The right column of Table 1 indicates that there is no Figure 5 and Figure 6 The temperature data of the case of the sleeve 4a and the plug 4b shown. When the same nitrogen flow rate is compared, when the sleeve 4a and the plug 4b are not present, the temperature drop of each part becomes less than when the sleeve 4a and the plug 4b are present, and the temperature difference also becomes smaller. It can be seen that when the outer wall of the second flow path 4 is formed by the inner wall of the sleeve 4a with lower thermal conductivity, the effect of cooling the Hall IC2 of the present invention is high compared with the case where the outer wall of the second flow path 4 is formed by the inner wall of the protection tube 1.

[0099] [Table 2]

[0100] Table 2

[0101]

[0102] Table 2 is data showing the relationship between the flow rate of nitrogen gas and the temperature of each part when the temperature of the tank detected by the temperature sensor 7 is controlled to 140°C in the same device configuration as Table 1. The left column of Table 2 shows the presence of Figure 5 and Figure 6 The temperature data in the case of the sleeve 4a and the plug 4b shown in Table 2. It can be seen that even when the temperature of the tank is 140°C, if the flow rate of nitrogen is 3.7slm (standard liters per minute) or more, the temperature of the Hall IC (semiconductor element) 2 can be cooled to less than 100°C. On the other hand, it can be seen that in the case of a structure with a sleeve and no plug shown on the right side of Table 2, the cooling effect achieved by nitrogen is increased compared to the case where the sleeve 4a and the plug 4b are present. It can be considered that the reason is that due to the lack of the plug 4b, a part of the nitrogen supplied to the top of the first flow path 3 enters the gap between the protective tube 1 and the outer wall of the sleeve 4a, and the remaining nitrogen cools the Hall IC (semiconductor element) 2 while rising inside the sleeve 4a, so that the heat transfer from the outside to the inside of the protective tube 1 is more reliably blocked. That is, in this case, the second flow path 4 branches into two systems.

[0103] Furthermore, in the above-described embodiment, as the flow rate of nitrogen supplied to the first flow path increases, the amount of heat released from the inside of the tank 6 through the protective tube 1 to the outside increases, and therefore, in order to maintain the temperature inside the tank 6, it is necessary to increase the output of the heater. However, according to the data in Tables 1 and 2, even when the flow rate of nitrogen is the largest, the temperature of the tank 6 is maintained at the set temperature. It can be seen from this that even when the liquid level sensor of the present invention is applied to a vaporizer of the prior art, there is no need to replace the heater with a heater with a higher heating capacity, and the conventional heater can be used as it is.

[0104] According to the above-described embodiment of the present invention, there is almost no need to change Figure 7 The structure of the liquid level sensor of the prior art shown above can expand the application temperature range of the liquid level sensor to a higher temperature side simply by adding the first flow path, the second flow path, and the fluid supply means.

[0105] Description of Reference Numerals

[0106] 1. Protective tube; 2. Sensor element (Hall IC); 2a. Printed wiring board; 2b. Endmost sensor element (endmost Hall IC); 2h. Holding member; 2s. Sensor; 3. First flow path; 3a. Capillary; 4. Second flow path; 4a. Sleeve; 4b. Plug; 5. Float; 5a. Magnet; 6. Tank; 7. Temperature sensor; 10. Shell; 11. Supply path; 12. Discharge path.

Claims

1. A sensor for use in a gasifier, wherein: The sensor features: One or more sensor elements; a first flow path for conveying a fluid from the outside of the sensor to the position of the sensor element; as well as a second flow path for returning the fluid transported to the position of the sensor element by the first flow path to the outside of the sensor, The fluid is not a gas obtained by gasifying a precursor using the gasifier.

2. The sensor according to claim 1, wherein: Among the components constituting the vaporizer, at least the component on which the sensor is disposed is accommodated in the housing. The vaporizer is configured to purge the interior of the housing by flowing an inert gas into the interior of the housing. The sensor is configured such that at least a portion of the inert gas flows as the fluid in the first flow path and the second flow path.

3. The sensor according to claim 1 or 2, wherein: The sensor also has a protective tube with one end closed and the other end open. The sensor element is arranged inside the protection tube, The first flow path is configured to transport the fluid from the position of the other end of the protection tube to the position of the endmost sensor element, which is the sensor element closest to the one end of the protection tube among the sensor elements. The second flow path is configured to return the fluid transported by the first flow path to the position of the sensor element at the endmost end to the position of the other end. The sensor element is disposed in at least one of the first flow path and the second flow path.

4. The sensor according to claim 3, wherein: At least one of the member constituting the first flow path and the member constituting the second flow path is made of a material having a thermal conductivity lower than a thermal conductivity of a member constituting the protection tube.

5. The sensor according to claim 3, wherein: The first flow path is arranged inside the second flow path.

6. The sensor according to claim 1 or 2, wherein: The sensor element is a semiconductor element having a pn junction.

7. The sensor according to claim 6, wherein: The semiconductor element is a Hall IC.

8. The sensor according to claim 1 or 2, wherein: The sensor element is a reed switch.

9. A liquid level sensor for use in a gasifier, wherein: The liquid level sensor has: a protective tube having one end closed and the other end open, and the protective tube being arranged to extend in a vertical direction; One or more sensor elements, which are arranged inside the protection tube; a first flow path configured to transport the fluid from the position of the other end of the protection tube to the position of an endmost sensor element, the endmost sensor element being the sensor element closest to the one end of the protection tube among the sensor elements; a second flow path configured to return the fluid transported by the first flow path to the position of the endmost sensor element to the position of the other end of the protection tube; and a float having a magnet and configured to move along the protection tube in accordance with a change in a liquid level of a precursor, the precursor being vaporized by the vaporizer to become a gas, The sensor element is disposed in at least one of the first flow path and the second flow path. The fluid is not a fluid obtained by gasifying the precursor using the gasifier.

10. The liquid level sensor according to claim 9, wherein: Among the components constituting the vaporizer, at least the component on which the liquid level sensor is disposed is accommodated in the housing. The vaporizer is configured to purge the interior of the housing by flowing an inert gas into the interior of the housing. The liquid level sensor is configured so that at least a part of the inert gas flows as the fluid in the first flow path and the second flow path.

11. The liquid level sensor according to claim 9 or 10, wherein: At least one of the member constituting the first flow path and the member constituting the second flow path is made of a material having a thermal conductivity lower than a thermal conductivity of a member constituting the protection tube.

12. The liquid level sensor according to claim 9 or 10, wherein: The first flow path is arranged inside the second flow path.

13. The liquid level sensor according to claim 9 or 10, wherein: The sensor element is a Hall IC.

14. The liquid level sensor according to claim 9 or 10, wherein: The sensor element is a reed switch.

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