JPH1164071A - Container for special material gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously, accurately, and easily monitor the fluctuation of the surface of a liquid in a container, while a special material gas is maintained at high purity by transmitting a ultrashort wave pulse towards the surface of the surface of the liquid from a sensor head attached to the top of the container and receiving the reflected pulse from the surface of the liquid. SOLUTION: An opening/closing valves 5 and 6 are respectively attached to the gas inlet 2 and outlet 3 of the main body 1 of a container for a special material gas provided in the upper section of the main body. At the same time, a sensor head 4 is fixed airtightly to the top of the main body 1 by welding it directly or via a tube fitting and the main body 1 is filled up with a liquid special material gas 11 by pouring the gas 11 into the container through the inlet 2, after adjusting the pressure in the main body 1 to a reduced pressure or vacuum. When the gas 11 is supplied to a semiconductor process by vaporizing the gas 11, the gas 11 is vaporized by bubbling by introducing an inert gas to the container via the inlet 2 and the vaporized gas is supplied to the semiconductor process through the outlet 3. When the gas 11 is supplied, the time until the reflected wave of an ultrasonic wave emitted from the sensor head 4 returns to the sensor head 4 from the surface of the liquid is detected and transmitted to an amplifier unit via a signal line 8 and the distance to the surface of the liquid from the front end of the sensor head 4 is calculated and displayed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a container for a liquid special material gas, and more particularly to a container for a liquid special material gas having a high purity used in a silicon and compound semiconductor manufacturing process, an optical fiber manufacturing process and the like. The present invention relates to a container for a special material gas that can be continuously grasped while maintaining a state.

[0002]

2. Description of the Related Art With the development of the semiconductor industry, the types and usages of special material gases, which are raw material gases, are increasing. In particular, as new raw materials, tetraethoxysilane, triethoxyborane, trimethylphosphoric acid, triethoxyarsine, silicon tetrachloride, trichlorosilane, phosphorus oxychloride,
Special material gases that are liquid at room temperature, such as arsenic trichloride, trimethylgallium, triethylgallium, and trimethylaluminum, are also increasing. With the increase in the degree of integration of semiconductor devices, these special material gases have been required to be in a state of high purity with very little moisture, metal impurities, and particles.

The liquid special material gas is usually filled in a relatively small and highly airtight metal container, and when used, is vaporized by decompression, evaporation by heating, bubbling with a base gas, or the like. And supplied to semiconductor manufacturing processes and the like. Liquid special material gases are usually filled in metal containers, but many are highly toxic and those that ignite when exposed to air, and are expensive. When the special material gas is filled or when the liquid special material gas is used, it is necessary to know the amount of the liquid special material gas in the container.

[0004] As a method of determining the amount of a liquid special material gas in a container, a method of measuring a change in weight of the entire container has conventionally been generally used. In addition, a method using an electrostatic capacitance type liquid level meter (Japanese Patent Laid-Open No. 6-239384), a method using a float type magnetic sensor, an ultrasonic transmitter and a receiver are attached to face the container side, and an ultrasonic A method of measuring the time from when a signal is transmitted until the reflected wave returns, and measuring the presence or absence of the filling by the difference between the time when the liquid is filled and when the liquid is empty, a light reflection detection type sensor , A method using X-rays, and the like have been attempted.

[0005]

However, the method of measuring the change in weight of the entire container has a large error, and furthermore, since the container is connected to a supply facility by piping, it is necessary to measure the weight after removing the container once. In addition to the low efficiency, there were safety problems such as gas leakage. In addition, the method using a capacitance-type liquid level gauge is susceptible to corrosion depending on the special material gas filled because the detection probe contacts the special material gas, and particles are generated because a porous material such as Teflon is used for the insulating material. There is a disadvantage that it is easy to do.

On the other hand, a method using a float type magnetic sensor and a method for measuring the presence / absence of a filler by mounting an ultrasonic transmitter and a receiver facing the side of the container are described below. This is detection, and is limited to use as a level switch, and has disadvantages in that it is not possible to continuously know a change in liquid level, and that particles are easily generated because the sensor is in contact with the filler. In addition, the method using a float-type magnetic sensor has disadvantages such as low airtightness, the possibility of particles being generated from the sliding part, and the fact that the special material gas adheres to the sliding part and hinders operation. is there.

In the method using a light reflection detection type sensor, particles do not easily occur because the sensor does not come into contact with the filling material, but there is a risk of erroneous detection because light is easily reflected irregularly in the container. Further, the method using X-rays is extremely expensive and lacks safety, so that there is a disadvantage that the place of use is limited.

For these reasons, there is a need for a special material gas container which can continuously, accurately and easily monitor a change in the liquid level in the container while maintaining the high purity of the special material gas. Was.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve these problems, and as a result, the use of an ultrasonic liquid level meter that measures by using reflection on the surface of a special material gas has been proposed. The inventors have found that the object can be solved, and have completed the present invention. That is, a first invention of the present invention is a container for storing, transporting, and supplying a liquid special material gas, which is a metal container having one or more gas inlets and outlets with an open / close valve. The time from transmission to reception by transmitting an ultrasonic pulse downward from the sensor head attached to the upper part of the container toward the liquid surface in the container and receiving the reflected pulse reflected on the liquid surface A special material gas container comprising an ultrasonic liquid level meter for measuring the liquid level from the sensor head, wherein the sensor head and the container are air-tightly fixed.

Further, the container of the present invention is for filling a special material gas, and it is necessary to know the exact amount of the liquid special material gas. Therefore, in the second invention of the present invention, in addition to the above-described container, a pipe joint is provided at an upper portion of the container in order to receive a highly accurate reflected pulse and accurately measure a liquid level. An ultrasonic level gauge for receiving an ultrasonic wave from a sensor head attached to the container and measuring a liquid level, wherein the sensor head, a pipe joint and the container are air-tightly fixed; It is.

The pipe joint according to the present invention eliminates as much as possible the reflection pulses other than the shortest distance among the reflection pulses reflected on the liquid surface, thereby enabling more accurate measurement. Some are included in the pipe joint referred to in the present invention regardless of shape and size. In addition, containers for liquid special material gas are often small in volume, and if the distance between the sensor head and the liquid surface is too short, measurement becomes impossible, so installing a pipe joint can improve such disadvantages. It is.

In the present invention, the liquid special material gas means a liquid having a vapor pressure of 3 kg / cm ² or less at 37 ° C., which is used in a silicon and compound semiconductor production process, an optical fiber production process and the like. Examples of these include tetraethoxysilane, trimethoxyphosphoric acid, triethoxyphosphoric acid, trimethoxydiborane, triethoxydiborane, triethoxyarsine, silicon tetrachloride, trichlorosilane, trimethylgallium, triethylgallium, trimethylaluminum, triethylaluminum, Titanium chloride, monomethylhydrazine, dimethylhydrazine, tertiary butyl hydrazine, tertiary butyl arsine, tertiary butyl phosphine, tetrahydrofuran, methanol, ethanol, butyl acetate, acetylacetone and the like.

The container for a special material gas of the present invention is a container for a liquid special material gas used in a silicon and compound semiconductor manufacturing process, an optical fiber manufacturing process and the like, and is used for storage, transfer, supply to a manufacturing process, and the like. used.

[0014] The container of the present invention has a content of usually 100 m.
It is made of a relatively small metal of about 1 to 20,000 ml. The shape of the container can take various shapes, but is usually cylindrical. The container is provided with one or more gas inlet / outlets equipped with an open / close valve such as a diaphragm valve, depending on the use form, purpose of use, etc. of the special material gas to be filled.

The material of the container is not particularly limited as long as the material has the type and the strength and the corrosion resistance suitable for the special material gas, storage conditions, and carbon steel, which is generally used as a container for the special material gas, Manganese steel, chromium steel, molybdenum steel, stainless steel and the like can be used.
However, since trace amounts of impurity gas or particles adsorbed on the inner wall of the container and the like may be mixed into the special material gas, it is preferable that the inner surface of the container is subjected to electrolytic polishing or an oxide film forming treatment. Stainless steel, such as SUS316 and SUS316L, whose inner surface is electropolished is particularly preferable.

Further, the special material gas container of the present invention may be handled under vacuum, reduced pressure, or pressurized conditions when it is filled with a liquid special material gas or supplied to a semiconductor manufacturing process. Since the container is sometimes used after being heated, it is preferable that the container can withstand vacuum and an internal pressure of about 25 kg / cm ² .

The ultrasonic liquid level gauge used in the present invention transmits an ultrasonic pulse toward the lower part of the container and receives the reflected pulse reflected on the liquid surface, so that the time from transmission to reception is obtained. Is used to measure the liquid level.
When the frequency is low, the measurable range is wide when the frequency is low, but the desired measurement accuracy is not obtained.On the other hand, when the frequency is high, the measurement accuracy is high, but the measurement is not possible. Since the range becomes narrower, usually 20 kHz to 1
MHz, preferably 100 to 700 kHz, more preferably 250 to 500 kHz.

An ultrasonic level gauge generally comprises a sensor head comprising a transmitting section and a receiving section of an ultrasonic pulse, and an amplifier unit comprising an arithmetic section and a display section. Is connected.

The sensor head of the ultrasonic liquid level gauge is mounted on the upper part of the metal container at a position not in contact with the liquid in the container so that the ultrasonic pulse is transmitted vertically toward the liquid surface. The sensor head of the ultrasonic level gauge is air-tightly fixed by a method of directly welding to the upper part of the container or a method of attaching it via a pipe joint welded to the upper part of the container.

In the case of mounting by a pipe joint, the distance from the bottom of the pipe joint to the sensor head is desirably 0.1 to 3 times the liquid depth when the liquid level is highest. When the container and the pipe joint are cylindrical, the inner diameter of the pipe joint is preferably about 1/2 to 1/20 of the inner diameter of the container. If the vessel and the pipe joint are not cylindrical, the average internal cross-sectional area of the pipe joint is one less than the average internal cross-sectional area of the vessel.
About / 4 to 1/400 is desirable.

As the pipe joint used in the present invention, a pipe joint for high pressure or vacuum used for a gas supply pipe in a semiconductor manufacturing process, for example, VCR type (Cageon), Swagelok type (Swagelok), M
Joints such as CG type (Toyoko Chemical Co., Ltd.) and ICF flange (Nidec Anelva Co., Ltd.) can be used. These can be airtightly attached to a container by fixing one of the joint parts to a metal container by welding or the like, fitting the sensor head inside the other one and fixing the joint, and joining the two joint parts together.

Next, the container for a special material gas of the present invention will be illustrated and specifically described with reference to the drawings, but the present invention is not limited to such an example. FIG. 1 is a perspective view of a container for special material gas when a liquid special material gas is vaporized and supplied by bubbling, FIG. 2 is a plan view of the container, and FIG. 3 is AA ′ of the container in FIG. It is a line sectional view. In FIGS. 1 to 3, a gas inlet 2 and a gas outlet 3 are provided at an upper portion of a container body 1, and openable valves 5 and 6 are attached to the gas inlet 2 and the gas outlet 3, respectively. A sensor head 4 is hermetically fixed to the upper part of the container body 1 by a pipe joint 7. Further, the sensor head 4 is connected to a signal line 8.
Are connected to the amplifier unit 9 to constitute the container for special material gas of the present invention.

When using the container for special material gas, the container is filled with the liquid special material gas 11 from the gas inlet 2 while the container is evacuated or evacuated. Next, when this is vaporized and supplied to semiconductor processes, etc.,
An inert gas such as nitrogen is introduced from a gas inlet 2, and the special material gas is vaporized by bubbling, and supplied to a semiconductor process or the like through a gas outlet 3. At this time, the ultrasonic wave emitted from the lower part of the sensor head is detected by the time until it is reflected on the liquid surface and returns,
The signal is transmitted to the amplifier unit 9 via the signal line 8, where the distance information is calculated and the distance from the tip of the sensor head to the liquid surface is displayed on the display unit 10.

[0024]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Example 1 (Production of container for special material gas) Inner diameter 90 mm, height 10
5 mm, 5 mm thick electropolished SUS316L, gas inlet 2 and outlet 3 on top, inner diameter 30 mm
A cylindrical container provided with a pipe joint mounting hole was prepared.
Diaphragm valves were attached to the upper portions of the gas inlet 2 and outlet 3 using joints. Next, one end of a pipe joint (Swagelok tube joint, manufactured by Swagelok Co., Ltd.) was inserted into the pipe joint mounting hole, and fixed by welding. On the other hand, the sensor head 4 of the ultrasonic liquid level gauge (Ultrasonic displacement sensor UD-310, manufactured by KEYENCE CORPORATION) was welded to the other end of the pipe joint (Swagelok tube joint, manufactured by Swagelok). Further, the sensor head 4 and the amplifier unit were connected by a signal line. In addition, in order to confirm the accuracy of the liquid level measurement by the ultrasonic liquid level meter, the cylindrical container is provided with a sight glass window 12 made of quartz glass, which is not usually attached, on the side of the container, and a special material shown in FIG. A gas container was prepared.

(Airtight test) (1) Nitrogen gas was introduced into the container, and the container was sealed under pressure to 5 kg / cm ² and left as it was for 24 hours, but there was no pressure drop. (2) Subsequently, a helium leak test was performed, and as a result, the leak rate was 1.4 × 10 ⁻⁸ torr L / sec.

(Liquid Level Measurement) The liquid level was measured by an ultrasonic liquid level meter using tetraethoxysilane as a liquid special material gas. First, a decompression pump was connected to the gas outlet of the container, and the inside of the container was depressurized by suction, and liquid tetraethoxysilane was charged into the container from the gas inlet. Then
Under an environment of room temperature and 25 ° C., nitrogen gas was introduced from a gas inlet, and bubbling was performed to vaporize tetraethoxysilane, and the gas was sequentially extracted from a gas outlet. At this time,
The distance from the tip of the sensor head to the liquid level in the container was measured by an ultrasonic liquid level meter, and this was used as a measured value. At the same time, the distance from the position corresponding to the tip of the sensor head to the liquid level in the container was measured using a ruler with a viewing window, and this was used as an actual measurement value. Table 1 shows the results.

(Measurement of Particles) A particle counter (manufactured by Rion Co., Ltd.) was connected to the outlet of the gas, and tetraethoxysilane was vaporized in the same manner as in the liquid level measurement, and the particle size present in the vaporized tetraethoxysilane was measured. 0.3μ
When particles of not less than m were measured, 5.7 × 10 ^-2 particles / m
³ or less.

Examples 2 to 4 Using the same special material gas container as used in Example 1, liquid levels were measured for each of butyl acetate, titanium tetrachloride, and monomethylhydrazine. Table 1 shows the results
Shown in Particle measurement was performed on each gas in the same manner as in Example 1. As a result, each gas was found to be 5.7 × 10 ^-2 particles / m ³ or less.

[0029]

[Table 1]

[0030]

According to the present invention, it is possible to continuously and accurately grasp the amount of the liquid special material gas existing in the container while maintaining a high purity state, and to predict the time of container replacement. Therefore, it can be used efficiently without loss of expensive special material gas. Moreover, the inside of the container is not corroded, and has excellent airtightness,
High safety because there is no risk of leakage.

[Brief description of the drawings]

FIG. 1 is a perspective view of a container for a special material gas.

FIG. 2 is a plan view of a container for a special material gas.

FIG. 3 is a sectional view taken along line A-A ′ in FIG. 2;

FIG. 4 is a perspective view of a cylindrical special material gas container with a viewing window used in Examples 1 to 4.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Container main body 2 Gas inlet 3 Gas outlet 4 Sensor head 5, 6 Open / close valve 7 Piping joint 8 Signal line 9 Amplifier unit 10 Display part 11 Liquid special material gas 12 Viewing window

Claims (6)

[Claims] 1. A container for storing, transporting and supplying a liquid special material gas, comprising: a metal container having one or more gas inlets and outlets with an openable valve; Transmits an ultrasonic pulse downward from the sensor head to the liquid surface in the container and receives the reflected pulse reflected from the liquid surface, and measures the liquid level from the time from transmission to reception. A container for special material gas, comprising: an ultrasonic liquid level gauge, wherein the sensor head and the container are fixed in an airtight manner. 2. A container for storing, transporting and supplying a liquid special material gas, comprising a metal container having one or more gas inlets and outlets with an open / close valve, and mounted on the upper part of the container. By transmitting an ultrasonic pulse downward from the sensor head attached to the upper part of the pipe joint and toward the liquid surface in the container, and receiving the reflected pulse reflected on the liquid surface, A container for special material gas comprising an ultrasonic liquid level gauge for measuring a liquid level from the time from transmission to reception until the sensor head, the pipe joint and the container are airtightly fixed. 3. The container for a special material gas according to claim 1, wherein the opening / closing valve is a diaphragm valve. 4. The special material gas container according to claim 2, wherein the pipe joint is a VCR type, a Swagelok type, an MCG type or an ICF flange. 5. The container has a content of 100 to 20,000 m.
The container for special material gas according to claim 1 or 2, which is 1. 6. SUS316 in which the material of the container is electrolytically polished
The container for special material gas according to claim 1 or 2, which is SUS316L.