LIQUID LEVEL INDICATOR AND LIQUID RAW MATERIAL VAPORIZATION FEEDER

Abstract

[Problem] To provide a liquid level indicator and a liquid raw material vaporization feeder, in which the time to detect a switch from the liquid phase to the gas phase has reduced flow rate dependence, and also the detection time can be shortened.

[Means for Resolution] The present invention includes a chamber 2 that stores a liquid raw material, at least one protection tube 3 housing a resistance temperature detector for detecting the liquid level L1 in the chamber 2, and a flow controller 4 that controls the flow rate of the gas flowing out from the chamber 2 and feeds the same. The protection tube 3 is horizontally inserted into a sidewall 2a of the chamber 2 and fixed thereto.

Claims

1. A liquid level indicator for use in a chamber that stores a liquid, comprising a liquid level detection member and a temperature measurement member, the liquid level detection member being configured to include a protection tube housing a resistance temperature detector and be horizontally disposed in the chamber.

2. The liquid level indicator according to claim 1, wherein the protection tube of the liquid level detection member is horizontally inserted into a sidewall of the chamber and fixed thereto.

3. The liquid level indicator according to claim 1, wherein the temperature measurement member includes a protection tube housing a resistance temperature detector and is horizontally disposed in the chamber.

4. The liquid level indicator according to claim 1, wherein the temperature measurement member includes a protection tube housing a thermocouple, a thermistor, or an infrared thermometer.

5. The liquid level indicator according to claim 3, wherein the temperature measurement member and the liquid level detection member are disposed at the same horizontal level.

6. The liquid level indicator according to claim 1, configured such that a current having a larger current value than a current for temperature measurement is passed through the resistance temperature detector of the liquid level detection member to measure a detection temperature, and the detection temperature measured by the liquid level detection member is compared with a temperature measured by the temperature measurement member, thereby detecting whether the liquid level detection member is present in a liquid phase portion or in a gas phase portion.

7. The liquid level indicator according to claim 3, configured such that a first current for temperature measurement is passed through the resistance temperature detector of the temperature measurement member, while a second current larger than the first current is passed through the resistance temperature detector of the liquid level detection member, and resistance values of the respective resistance temperature detectors are compared, thereby detecting whether the liquid level detection member is present in a liquid phase portion or in a gas phase portion.

8. The liquid level indicator according to claim 7, wherein the temperature measurement member is disposed below a predetermined minimum liquid level, and the liquid level detection member is disposed at the minimum liquid level or a predetermined maximum liquid level.

9. A liquid level indicator comprising: a protection tube horizontally disposed in a chamber that stores a liquid raw material and housing a resistance temperature detector, the liquid level indicator being configured such that a current having a first current value for temperature measurement and a current having a second current value larger than the first current value are alternately passed through the resistance temperature detector, and resistance values of the resistance temperature detector with respect to the respective current values are compared, thereby detecting whether the protection tube is present in a liquid phase portion or in a gas phase portion.

10. A liquid level indicator comprising: a protection tube horizontally disposed in a chamber that stores a liquid and housing a resistance temperature detector, the liquid level indicator being configured such that a current having a predetermined current value larger than that of a current for temperature measurement is passed through the resistance temperature detector, and, based on changes in resistance between when the protection tube is in a liquid phase portion and when it is in a gas phase portion, whether the protection tube is in a liquid phase portion or in a gas phase portion is detected.

11. The liquid level indicator according to claim 1, wherein the protection tube has been subjected to a passivation treatment.

12. A liquid raw material vaporization feeder comprising: a chamber that stores and vaporizes a liquid raw material; a liquid level detection member disposed in the chamber; a temperature measurement member that measures the temperature in the chamber; and a flow controller that controls the flow rate of the raw material gas vaporized in the chamber, the liquid level detection member being configured to include a protection tube housing a resistance temperature detector and be horizontally disposed in the chamber.

13. The liquid raw material vaporization feeder according to claim 12, wherein the protection tube is horizontally inserted into a sidewall of the chamber and fixed thereto, the protection tube includes a flange for fixing to the sidewall of the chamber, and the liquid raw material vaporization feeder includes: a metal gasket interposed between the flange and the outer surface of the sidewall of the chamber and surrounding a perimeter of the protection tube; recesses for a gasket, each formed in each of the flange and the outer surface of the sidewall of the chamber for receiving the metal gasket; and annular projections for pressing a gasket, formed in each recess for a gasket.

14. The liquid raw material vaporization feeder according to claim 12, wherein the protection tube is screw-fixed to the chamber.

15. The liquid raw material vaporization feeder according to claim 12, wherein the temperature measurement member includes a protection tube housing a resistance temperature detector or a thermocouple and is horizontally disposed in the chamber, and the liquid level detection member and the temperature measurement member are disposed at the same horizontal level.

16. The liquid raw material vaporization feeder according to claim 12, wherein a vapor barrier plate for blocking vapor rising from the liquid raw material is provided below the protection tube.

17. The liquid raw material vaporization feeder according to claim 16, wherein the vapor barrier plate extends obliquely.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0038] [FIG. 1] A partial cross-sectional side view showing a first embodiment of the liquid raw material vaporization feeder including a liquid level indicator according to the present invention.

[0039] [FIG. 2] A schematic perspective view of the inside of the chamber of FIG. 1.

[0040] [FIG. 3] An expanded plan view of a flange fixed to the protection tube shown in FIG. 1.

[0041] [FIG. 4] A cross-sectional view along the line of FIG. 3.

[0042] [FIG. 5] An enlarged, essential part longitudinal cross-sectional view of the fixing structure for the protection tube shown in FIG. 1.

[0043] [FIG. 6] A graph showing the evaluation test results of Example 1 of the present invention.

[0044] [FIG. 7] A graph showing the evaluation test results of Comparative Example 1.

[0045] [FIG. 8] A graph showing the evaluation test results of Example 2 of the present invention.

[0046] [FIG. 9] A graph showing the evaluation test results of Comparative Examples 1 to 3.

[0047] [FIG. 10] A partial cross-sectional side view showing a second embodiment of the liquid raw material vaporization feeder including a liquid level indicator according to the present invention.

[0048] [FIG. 11] A schematic perspective view of the inside of the chamber shown in FIG. 10.

[0049] [FIG. 12] A partial cross-sectional side view showing a third embodiment of the liquid raw material vaporization feeder including a liquid level indicator according to the present invention.

[0050] [FIG. 13] Longitudinal cross-sectional views of a protection tube and a vapor barrier plate, showing a variation of the third embodiment of FIG. 12.

[0051] [FIG. 14] A schematic perspective view of the inside of the chamber shown in FIG. 12.

[0052] [FIG. 15] A schematic configuration diagram showing a conventional liquid level indicator.

[0053] [FIG. 16] A circuit diagram showing an example of a liquid level detection circuit of a conventional liquid level indicator.

DESCRIPTION OF EMBODIMENTS

[0054] Hereinafter, embodiments of the liquid raw material vaporization feeder including a liquid level indicator according to the present invention will be described with reference to the drawings. Through all the figures and embodiments, the same or similar components are indicated with the same reference numeral.

[0055] FIG. 1 is a cross-section side view showing a first embodiment of the present invention. As shown in FIG. 1, the liquid raw material vaporization feeder 1 including a liquid level indicator according to the present invention includes a vaporization chamber 2 that stores and vaporizes a liquid raw material L, a protection tube 3 having enclosed therein a resistance temperature detector (not shown) for detecting the liquid level L1 in the vaporization chamber 2, and a flow controller 4 that controls the flow rate of the gas vaporized in the vaporization chamber 2 and feeds the same. Two protection tubes 3,3 (see FIG. 2.) are inserted into a sidewall 2a of the vaporization chamber 2 at the same horizontal level and fixed thereto.

[0056] As the resistance temperature detector enclosed in the protection tube 3, it is preferable to use a platinum resistance temperature detector, but other known resistance temperature detectors may also be used. As a liquid level detection circuit using resistance temperature detectors, a circuit having the same principles as the conventional circuit described above may be employed, and thus the detailed description will be omitted. The two protection tubes 3,3 have the same outer diameter, and each tube 3 houses a resistance temperature detector in a distal end portion of its elongated rod portion.

[0057] The protection tubes 3,3 house identical resistance temperature detectors, respectively. One protection tube 3 and the resistance temperature detector housed therein form a temperature measurement member used for ambient temperature measurement, configured such that a current for temperature measurement, that is, a minute constant current that allows for ambient temperature measurement and causes negligible self-heating of the resistance temperature detector, is passed through the resistance temperature detector. The other protection tube 3 and the resistance temperature detector housed therein form a liquid level detection member, configured such that a relatively large constant current (heating current) is passed through the resistance temperature detector so as to maintain its temperature higher than the ambient temperature by self-heating, and, through the above liquid level detection circuit, whether it is in the liquid phase or in the gas phase is determined.

[0058] The vaporization chamber 2 has a box shape having, on its top, a feed port 2b for a liquid raw material and a discharge port 2c for a vaporized gas, and is made of a metal such as stainless steel. The feed port for a liquid raw material is not limited to the illustrated example. It is also possible that a feed pipe is inserted into the upper wall of the vaporization chamber 2, and the lower end of the feed pipe is extended to an inner lower portion of the vaporization chamber 2, thereby providing a feed port in the inner lower portion of the vaporization chamber 2. Alternatively, the feed port may also be provided in the sidewall of the vaporization chamber 2 or the bottom wall of the vaporization chamber 2.

[0059] The vaporization chamber may be heated by a heater (not shown) attached surrounding the outer surface of the chamber wall. Although not shown, it is also possible that a recess or a hole is formed in the metal wall forming the vaporization chamber 2, and the heater that heats the vaporization chamber 2 is embedded therein.

[0060] Although the vaporization chamber 2 is formed of a single chamber in the illustrated example, it is also possible that a chamber is partitioned into a plurality of chambers with a partitioning wall (not shown), and a hole for passing the vaporized gas is formed in each partitioning wall. In this case, a feed port for feeding a liquid raw material is provided in the partitioned chamber on one end side, and a discharge port for discharging a vaporized gas is provided in the partitioned chamber on the other end side.

[0061] The discharge port 2c is connected to communicate with a gas channel 5. The gas channel 5 is formed of a pipe or a hole formed in the block. In the gas channel 5, a flow controller 4 is interposed. As the flow controller 4 of the illustrated example, a known, so-called pressure-type flow controller may be employed, wherein the gas pressure on at least the upstream side of an orifice plate 6 interposed in the gas channel 5 is detected by a pressure detector 7, and, based on the detected pressure signal, a metal diaphragm valve element interposed in the gas channel 5 is opened/closed by a piezoelectric driving element, thereby controlling the flow rate. That is, when the absolute pressure on the upstream side of the orifice plate 6 becomes about twice or more the absolute pressure on the downstream side of the orifice plate 6 (critical expansion condition), the gas passing through the orifice reaches, but does not exceed, the sonic speed. Accordingly the flow rate is dependent only on the pressure on the orifice upstream side, and the flow rate is proportional to the pressure; this principle is utilized. Although not shown, it is also possible that the pressure on the orifice downstream side is detected, the flow rate is controlled based on the difference in pressure between the upstream side and the downstream side of the orifice.

[0062] In the gas channel 5, a pneumatically driven on/off valve 8 is interposed. Although the on/off valve 8 is interposed in the gas channel 5 between the vaporization chamber 3 and the flow controller 4, it may also be provided in the gas channel on the downstream side of the flow controller 4 or may alternatively be omitted.

[0063] The protection tube 3 is made of a corrosion-resistant metal material, such as stainless steel, and houses a resistance temperature detector in a distal end portion of its elongated sheath portion 3a. A passivation film of stainless steel is relatively thin, and thus it is preferable to further subject the protection tube 3 to a passivation treatment to enhance the corrosion resistance.

[0064] Because the protection tube 3 is horizontally inserted into the vaporization chamber 2, it is necessary to fix the protection tube 3 with a sealing structure that prevents the leakage of the high-temperature liquid raw material from the vaporization chamber 2.

[0065] With reference to FIG. 3 to FIG. 5, the protection tube 3 is fitted into a hole 9a formed in the flange 9 also made of stainless steel and fixed to the fixing flange 9 by welding. The fixing flange 9 includes, in addition to the hole 9a, a plurality of bolt holes 9b and a first recess for a gasket 9c formed around the hole 9a on one side surface of the fixing flange 9. The first recess for a gasket 9c has formed thereon a first annular projection for pressing a gasket 9d.

[0066] The vaporization chamber 2 includes, on one side surface, a bottomed female screw hole 2d that agrees with the bolt hole 9b of the fixing flange 9, a through-hole 2e that passes the protection tube 3, and a second recess for a gasket 2f formed on the perimeter of the through-hole 2e on the outer side surface of the vaporization chamber 2. The second recess for a gasket 2f has formed thereon a second annular projection for a gasket presser 2g.

[0067] The protection tube 3 is passed through the annular metal gasket 10 and the through-hole 2e of the vaporization chamber 2, and the male screw 11 passed through the bolt hole 9b of the fixing flange 9 is screwed into the female screw hole 2d of the vaporization chamber 2. As a result, the first annular projection for pressing a gasket 9d and the second annular projection for pressing a gasket 2g dig into both side surfaces of the metal gasket 10, whereby the through-hole 2e of the vaporization chamber 2 is hermetically sealed. The metal gasket 10 may be made of stainless steel.

[0068] Through examples of liquid raw material vaporization feeders including a liquid level indicator according to the present invention and comparative examples of liquid raw material vaporization feeders including a conventional liquid level indicator (see FIG. 15), in which a protection tube housing a platinum resistor is vertically (longitudinally) inserted into the vaporizer, the detectability of a change from the liquid phase to the gas phase was evaluated.

[0069] FIG. 6 shows the results of Example 1, and FIG. 7 shows the result of Comparative Example 1. In both Example 1 and Comparative Example 1, a constant current of 1 mA was passed through one platinum resistance temperature detector, and a constant current of 30 mA was passed through the other platinum resistance temperature detector. As the platinum resistors, those having temperature characteristics of 100Ω at 0° C. and 0.39Ω/° C. (e.g., 103.9Ω at 10° C.) were used. The evaluation conditions of the evaluation test were as follows. Using TEOS as a liquid raw material, the vaporization chamber 2 was set at a temperature of 200° C. and a controlled gas flow rate of 53.17% (6.7 g /min), and the inside of the vaporization chamber was evacuated to a vacuum, followed by feeding the liquid raw material until the protection tubes were submerged. The valve of the flow controller and also the valve interposed in the liquid raw material feed pipe of the vaporization chamber were closed, and, after sealing for minutes, the flow controller was operated to flow the vaporized gas at a specific flow rate.

[0070] In FIG. 6 and FIG. 7, the line T1 is a graph showing changes over time in the temperature of the platinum resistance temperature detector through which 30 mA was passed, and the line T2 is a graph showing changes over time in the temperature of the platinum resistance temperature detector through which 1 mA was passed. The temperature of each platinum resistance temperature detector was computed by calculation from the temperature characteristics of the platinum resistance temperature detector. In FIG. 6 and FIG. 7, the region where ΔT=T1−T2 is large indicates the transition from the gas phase to the liquid phase.

[0071] As shown in FIG. 6 and FIG. 7, in Example 1 shown in FIG. 6, the transition from the gas phase to the liquid phase was detected within 30 seconds, but in Comparative Example 1 of FIG. 7, detection took about 3 minutes. The reason why the detection time in Comparative Example 1 is longer than in Example 1 is likely to be as follows. In Example 1, during the vaporization of the liquid raw material and the resulting transition from the gas phase to the liquid phase, because the protection tubes are horizontally installed, they are submerged over the entire length. In contrast, in the comparative example, with reference to FIG. 15, because the protection tubes are longitudinally installed, they are gradually exposed from the liquid phase. Accordingly, heat dissipation to the liquid decreases, resulting in increased self-heating.

[0072] Next, the same evaluation test as in Example 1 was performed in Example 2, where the controlled flow rate was set lower than in Example 1, and also in Comparative Example 2 and Comparative Example 3, where the controlled flow rate was lower than in Comparative Example 1. The results are shown in FIG. 8 and FIG. 9. FIG. 8 corresponds to Example 2. In Example 2, the controlled flow rate was set at 3.0 g/min. FIG. 9 shows ΔT=T1−T2 of Comparative Examples 1, 2, and 3, where the line C1, line C2, and line C3 show Comparative Example 1, Comparative Example 2, and Comparative Example 3, respectively. The controlled flow rate in Comparative Example 1 was 6.7 g/min, the controlled flow rate in Comparative Example 2 was 3.0 g/min, and the controlled flow rate in Comparative Example 3 was 1.0 g/min.

[0073] Comparing FIG. 8 and FIG. 9, between Example 1 and Example 2, even when the controlled flow rate was changed from 6.7 g/min to 3.0 g/min, no significant difference was observed in the time to detect a change from the liquid phase to the gas phase. However, in Comparative Examples 1 to 3, the time to detect a change from the liquid phase to the gas phase increased with a decrease in the controlled flow rate, and the detection time was about 3 minutes in Comparative Example 1, about 5.5 minutes in Comparative Example 2, and about 9.1 minutes in Comparative Example 3. With respect to the time to detect a change from the liquid phase to the gas phase, such a difference between the examples and the comparative examples is likely to be attributable to the difference in the time taken for the protection tube to change from the submerged state to the exposed state.

[0074] In the first embodiment described above, two resistance temperature detectors are used, and the current passing through one resistance temperature detector is made larger than the current passing through the other resistance temperature detector, whereby the transition of the liquid level from the liquid phase to the gas phase (or from the gas phase to the liquid phase) is detected. However, it is also possible that only one resistance temperature detector is provided, and large and small currents of predetermined magnitudes (a current for temperature measurement and a heating current) are alternately passed through the resistance temperature detector every predetermined period of time (e.g., every 10 to 15 seconds), whereby the transition of the liquid level from the liquid phase to the gas phase (or from the gas phase to the liquid phase) is detected.

[0075] FIG. 10 is a partial cross-sectional side view showing a second embodiment of the liquid raw material vaporization feeder including a liquid level indicator according to the present invention. In the second embodiment, protection tubes 3 each housing a resistance temperature detector are attached in two levels to the vaporization chamber 2. With reference to FIG. 11, the attachment of the protection tubes 3 each housing a resistance temperature detector is such that two protection tubes 3 (a liquid level detection member and a temperature measurement member) are attached at the same height of the upper level, while two protection tubes 3 (a liquid level detection member and a temperature measurement member) are also attached at the same height of the lower level. By providing a pair of protection tubes in two levels, the maximum liquid level and the minimum liquid level of a liquid raw material in the vaporization chamber 2 can be determined. The protection tube containing a resistance temperature detector forming the upper-level temperature measurement member may also be omitted. In this case, the maximum liquid level can be detected by the lower-level temperature measurement member and the upper-level liquid level detection member.

[0076] FIG. 12 is a partial cross-sectional side view showing a third embodiment of the liquid raw material vaporization feeder including a liquid level indicator according to the present invention. In the third embodiment, a vapor barrier plate 13 for blocking vapor rising from the liquid raw material is provided below the protection tube 3. It is preferable that the vapor barrier plate 12 is arranged to extend obliquely downward or upward (downward in the illustrated example below) from the proximal portion to the distal end portion. The vapor barrier plate 12 may be in the form of a flat plate, or may also be in the form of a plate having an angle cross-section as shown in FIG. 13 and FIG. 14. By providing a vapor barrier plate 12, malfunctioning due to vapor of the liquid raw material can be reduced. The width dimension and length of the vapor barrier plate 12 can be suitably designed, but it is preferable that the width dimension is 1.5 to 2 times the outer diameter of the protection tube 3, and the length dimension is about 1 to 1.3 times the length of the protection tube 3.

[0077] In the above embodiments, examples in which a resistance temperature detector is housed in the protection tube 3 of a temperature measurement member have been described. However, as long as the temperature measurement member can measure the ambient temperature, in place of resistance temperature detectors, other temperature sensors, such as thermocouples, thermistors, and infrared thermometers, may be housed in the protection tubes.

[0078] In addition, in the above embodiments, examples in which the protection tube of a temperature measurement member and the protection tube of a liquid level detection member are disposed at the same horizontal level have been shown. However, the configuration may also be such that the protection tube of a temperature measurement member is disposed below a predetermined minimum liquid level so as to be submerged all the time, and the protection tube of a liquid level detection member is disposed at the minimum liquid level and/or a maximum liquid level.

[0079] In addition, the attachment of protection tubes to the chamber is not limited to the above embodiments. For example, it is possible that a screw hole is formed in the wall of the chamber, while a male screw is formed on the outer periphery of the protection tube, and the protection tube is screwed into and thus fixed to the chamber.

[0080] In addition, in the above embodiments, an example of a hermetically sealed vaporization chamber has been described. However, a chamber having an open top is also usable.

[0081] In addition, the liquid level to be detected is not limited to that of a liquid raw material used in a semiconductor manufacturing device, and the present invention is also applicable to various liquid chemicals and the like.

REFERENCE SIGNS LIST

[0082] 1: Liquid raw material vaporization feeder [0083] 2: Vaporization chamber [0084] 3: Protection tube [0085] 4: Flow controller [0086] L: Liquid raw material [0087] L1: Liquid level [0088] 9: Flange [0089] 10: Metal gasket [0090] 9c, 2f : Recess for gasket [0091] 9d, 2g : Annular projection for pressing gasket [0092] 12: Vapor barrier plate