JP4375766B2 - Deaeration device and deaeration method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a degassing apparatus and a degassing method for performing degassing using a tubular membrane that allows a dissolved gas in a liquid to be treated to permeate, and in particular, degassing from a liquid chemical used in a semiconductor manufacturing process. Useful for deaeration process.
[0002]
[Prior art]
Conventionally, in the manufacture of semiconductors such as large-scale integrated circuits, plasma vapor deposition (PECVD) has been used as a thin film formation process. In this method, a gaseous or liquid chemical (precursor) is supplied to the gas dispersion head of the deposition station in the reactor to react with the silicon base layer, but when the chemical is supplied in a liquid state, Before entering the reactor, it is gasified through a vaporizer.
[0003]
In modern PECVD systems, the liquid chemical delivery system needs to meet two important criteria. One is to supply liquid chemicals at a given flow rate at a uniform and stable pressure, and the other is free of particles and gases so that liquid chemicals can be accurately metered into liquids. . In a system using a pump as a supply source, there is a problem of impurities and a problem that it is difficult to control the pressure and flow rate uniformly, so there is a method of supplying liquid chemicals stored in a container by gas pressurization. , Mainly adopted.
[0004]
However, in the above method, the dissolved gas exists in the liquid, so that the dissolved gas is easily generated in the liquid as bubbles, and the presence of the bubbles changes the thermal conductivity of the liquid. For this reason, the liquid mass flow controller malfunctions, and the liquid cannot be supplied accurately and stably. As a result, there are problems such as non-uniform thickness and quality of the thin film deposited by PECVD.
[0005]
In view of this, as an apparatus for removing such dissolved gas, Japanese Patent Application Laid-Open No. 6-220640 discloses that a liquid to be treated (supply liquid) is circulated in a tubular membrane (tube) from which dissolved gas can be separated. There has been proposed a deaeration device that removes dissolved gas by depressurizing the outer space of the membrane.
[0006]
As shown in FIG. 4, a membrane module is configured by arranging a large number of hollow fiber membranes 22 in a horizontally installed housing 23, and a liquid to be treated is supplied to an internal space 21 in the housing 23. There is known a deaeration device that removes dissolved gas by reducing the inner space of the hollow fiber membrane 22 from the decompression port 27 communicating with the hollow fiber membrane 22 while supplying from the discharge port 25 and discharging from the discharge port 25. . If necessary, a sweep gas is supplied from the inlet 26.
[0007]
[Problems to be solved by the invention]
However, in the former degassing apparatus, once bubbles are generated due to changes in the environment such as pressure and temperature, there is no sufficient contact time (opportunity) with the tubular membrane wall surface to allow bubbles to permeate. In some cases, there is a disadvantage that bubbles are discharged to the outside.
[0008]
In the latter deaeration device, once air bubbles are generated, the air bubbles stay in the vicinity of the upper wall surface in the housing (portion 21a in FIG. 4). There is a possibility that bubbles may be discharged together with the treatment liquid.
[0009]
And the problem of the bubble discharge | emission in the above deaeration processes is a subject common not only to the deaeration at the time of chemical | medical solution supply of a semiconductor manufacturing process but other deaeration processes.
[0010]
Accordingly, an object of the present invention is to provide a deaeration device and a deaeration method in which generated bubbles are difficult to be discharged together with the processing liquid.
[0011]
[Means for Solving the Problems]
The above object can be achieved by the present invention as described below.
That is, in the degassing apparatus of the present invention, the tubular membrane that allows the dissolved gas in the liquid to be treated to pass through is inserted into the tubular body, and the flow path of the liquid to be treated is formed outside the tubular membrane, while the tubular membrane A bubble blocking portion that prevents the generated bubbles from flowing downstream by disposing the inner space of the tube in a reduced pressure state and disposing at least a part of the tubular body so that the downstream side is positioned below the upstream side. This is a deaeration device provided. Here, the tubular body is not limited to a circular tubular body, but refers to a relatively long one having an annular cross section.
[0012]
In the above, it is preferable that a gas reservoir is provided at the upper end of the bubble blocking portion, and that the tubular membrane is disposed inside the gas reservoir.
[0013]
Moreover, it is preferable that a heating means is provided on at least a part of the outer periphery of the tubular body.
[0014]
On the other hand, the degassing method of the present invention is a degassing method in which degassing is performed from a liquid chemical used in a semiconductor manufacturing process using any of the above-described degassing apparatuses.
[0015]
[Function and effect]
According to the degassing apparatus of the present invention, a tubular membrane that allows the dissolved gas in the liquid to be treated to pass through is inserted into the tubular body, and a flow path for the liquid to be treated is formed outside the tubular membrane, while the tubular membrane In order to make the inner space in a reduced pressure state, the dissolved gas can be removed from the liquid to be treated by allowing the dissolved gas to permeate the tubular membrane due to the pressure difference between the inside and outside of the membrane. At that time, at least a part of the tubular body is disposed so that the downstream side is located below the upstream side, and a bubble blocking portion that prevents the generated bubbles from flowing downstream is provided. Due to the buoyancy of the bubbles, the bubbles can be prevented from flowing downstream. Moreover, in the case where the flow path of the liquid to be processed is formed inside the tubular membrane, if the bubbles are increased to some extent, the bubbles are less likely to rise in the liquid to be processed due to the buoyancy of the bubbles. Since the flow path of the liquid to be treated is formed at the same time, the bubbles can be easily lifted by buoyancy, and the bubbles can be effectively prevented from flowing downstream. As a result, it is possible to provide a deaeration device in which generated bubbles are difficult to be discharged together with the processing liquid.
[0016]
When a gas reservoir is provided at the upper end of the bubble blocking portion and the tubular membrane is disposed inside the gas reservoir, the generated bubbles are likely to move to the upper end side and stay in the gas reservoir. In addition, since the tubular membrane is disposed inside the gas reservoir, the staying gas can be permeated and removed by the pressure difference inside and outside the membrane.
[0017]
When the heating means is provided on at least a part of the outer peripheral portion of the tubular body, the inside of the tubular body can be efficiently heated only by providing the heating means on the outer peripheral portion. The gas permeability of the tubular membrane can be increased and deaeration can be performed efficiently. In addition, when the relationship between the liquid to be treated and dissolved gas is such that the solubility is lower as the temperature is higher, the dissolved gas can be more efficiently removed from the liquid to be treated by positively generating bubbles by heating. Can do.
[0018]
On the other hand, according to the degassing method of the present invention, since any one of the degassing devices described above is used, a degassing method in which generated bubbles are difficult to be discharged together with the processing liquid due to the above-described effects. For this reason, the degassing method of the present invention is a particularly useful technique as a method of degassing liquid chemicals used in semiconductor manufacturing processes, where the presence of dissolved gas is particularly problematic.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a main part of an example of the deaeration device of the present invention. In the present embodiment, an example is shown in which a straight tubular body 2 is arranged in the vertical direction to form a bubble blocking portion FP, a gas reservoir portion 10 is provided at the upper end portion thereof, and the tubular membrane 1 is arranged inside. .
[0020]
As shown in FIG. 1, the degassing apparatus of the present invention inserts a tubular membrane 1 through which a dissolved gas in a liquid to be treated permeates into a tubular body 2, and a flow path of the liquid to be treated outside the tubular membrane 1. 3 is formed.
[0021]
The tubular membrane 1 may be any one that allows permeation of dissolved gas in the liquid to be treated, and is made of a nonporous membrane or a porous membrane that has been used as a separation membrane for deaeration. Tubular or hollow fiber membranes can be used. Specifically, fluororesins such as PTFE, FEP, and PFA, and polyethylene, polypropylene, or polyamide-based separation membranes can be suitably used. In order to improve the contact efficiency between the liquid to be treated and the tubular membrane 1 by turbulent flow in the flow path 3 outside the tubular membrane 1, it is preferable that the outer surface shape has irregularities like a bellows tube.
[0022]
For example, in the case of liquid chemicals used in semiconductor manufacturing processes, the liquid to be treated includes tetraethyl orthosilicate, trimethyl phosphite, trimethyl borate, triethyl phosphite, triethyl borate, tetrakis (Diethyl) amino titanium and the like. Examples of the dissolved gas include helium, nitrogen, neon, argon, carbon dioxide, and oxygen.
[0023]
The tubular body 2 may be made of any material as long as there is no inconvenience such as corrosion by the liquid to be treated. However, in consideration of corrosion resistance and the like, fluororesin and SUS are preferable. In the illustrated example, a circular tube is used, but any cross-sectional shape may be used. In order to improve the contact efficiency between the liquid to be treated and the tubular membrane 1 by turbulent flow in the flow path 3 inside the tubular body 2, it is preferable that the inner surface shape has irregularities like a bellows tube.
[0024]
The tubular membrane 1 is inserted into the tubular body 2, and the flow channel 3 for the liquid to be treated is formed outside the tubular membrane 1, but the area of the cross section of the flow channel is the inner diameter of the tubular body 2 and the tubular membrane 1. It is determined by the outer diameter. In the illustrated example, the inner diameter of the tubular body 2 is preferably about 3 to 30 mm, the outer diameter of the tubular membrane 1 is about 1 to 10 mm, and the ratio (the former / the latter) is preferably about 4 to 1.2.
[0025]
The tubular body 2 is arranged in a substantially vertical direction so that the downstream side is positioned below the upstream side, and substantially the whole of the tubular body 2 constitutes the bubble blocking portion FP, but at least a part of the tubular body 2 is downstream. What is necessary is just to arrange | position so that the side may be located below from the upstream. Such a bubble blocking unit FP can prevent the generated bubbles from flowing downstream.
[0026]
A gas reservoir portion 10 is formed by a tubular body 10a continuous with the tubular body 2 at the upper end portion of the bubble blocking portion FP, and a tubular membrane 1a continuous with the tubular membrane 1 is disposed therein. The upper end of the tubular body 10a is joined to the male side of the resin pipe joint 5, and the tubular membrane 1a is inserted through the male side and sealed by tightening on the female side. The generated bubbles rise and gather in the internal space 10b of the gas reservoir 10, but when the pressure inside the tubular membrane 1a is reduced, the accumulated gas passes through the tubular membrane 1a and is removed.
[0027]
The upper end of the tubular membrane 1a is connected to a decompression pipe 7 via a pipe joint 6 (various fittings), and the decompression pipe 7 is connected to a decompression device (not shown) such as a vacuum pump. The decompression pipe 7 is made of a metal that does not easily pass through gas. By the operation of the decompression device, the inner space 4 of the tubular membrane 1 is decompressed via the decompression pipe 7.
[0028]
The boundary between the tubular body 2 and the tubular body 10a is branched into a T shape, and the supply pipe 8 is integrally branched and connected. On the other hand, the lower end of the tubular body 2 is also branched into a T shape, and the discharge pipe 9 is integrally branched and connected. The liquid to be treated is supplied through the supply pipe 8 and flows downward through the flow path 3 formed outside the tubular membrane 1. Then, the liquid is discharged to the outside through the discharge pipe 9. Degassing is performed by the permeation of dissolved gas. In addition, the bubbles generated in the meantime can move upward and be degassed by the gas reservoir 10, but the bubbles flowing in from the supply pipe 8 can also be degassed by the gas reservoir 10.
[0029]
The tubular membrane 1 and the tubular body 2 are continuous below the branch portion of the discharge pipe 9 and have a seal structure similar to the upper end portion. The lower end of the tubular membrane 1 may be sealed, but a valve may be provided so that a sweep gas can be supplied if necessary. As the sweep gas, nitrogen gas or the like that is difficult to permeate the tubular membrane 1 can be suitably used.
[0030]
In this invention, as shown in FIG. 1, you may provide a heating means in the outer peripheral part of at least one part of the tubular body 2. As shown in FIG. As the heating means, for example, the heating wire 11 may be wound around the outer periphery of the tubular body 2 or an electric heater may be disposed. When the tubular membrane 1 made of FEP is used, at 50 ° C. and 25 ° C., the gas permeability coefficient is 1.8 times helium, 2.7 times oxygen, and 2.1 times nitrogen.
[0031]
Hereinafter, a degassing method for performing degassing from a liquid chemical used in a semiconductor manufacturing process using the degassing apparatus of the present invention will be described. Such a degassing method is used in a liquid supply system as shown in FIG.
[0032]
The liquid supply system includes a supply source 12, a deaeration device DG, and a liquid mass flow controller 17. The liquid 13 is supplied from the supply source 12 by moving the liquid 13 using the pressurized gas 14. The supply source 12 includes a gas inlet 15a connected to a supply source (not shown) for supplying pressurized gas, and a liquid outlet 15b connected to the deaerator DG via a supply pipe 8. Container 15. In this example, the gas 14 is helium and the liquid 13 is tetraethylorthosilicate (TEOS). Other gases and other liquids that do not chemically react with each other can be used in place of helium and TEOS. For example, instead of TEOS, trimethyl phosphite (TMP) and trimethyl borate (TMB) used in the PECVD reactor are supplied by the present invention.
[0033]
Within source 12, a certain amount of helium dissolves in TEOS depending on pressure and temperature. The generation of helium bubbles in the low pressure region on the downstream side interrupts the TEOS flow and causes incorrect liquid metering in the liquid mass flow controller. The degassing device DG removes helium gas dissolved in the liquid TEOS by the above-described device configuration. The decompression pipe 7 of the deaeration device DG is connected to an exhaust pump 16. The discharge pipe 9 of the deaeration device DG is connected to the liquid mass flow controller 17.
[0034]
The liquid mass flow controller 17 is used to distribute the liquid 13 so as to accurately measure the liquid at a flow rate desired by the user and at a uniform pressure. The liquid mass flow controller 17 may be any controller known to those skilled in the art. The outlet of the liquid mass flow controller 17 is connected to a PECVD reactor 18 and is connected to a vaporizer 19 provided in the PECVD reactor 18. After the liquid 13 is vaporized, the vaporized liquid is sent to a gas dispersion head (not shown). A plurality of liquid mass flow controllers 17 and PECVD reactors 18 are provided as necessary.
[0035]
In the above description, the length of the tubular membrane 1 where deaeration is performed may be determined as follows, for example. The maximum flow rate of the supply flow rate of the liquid 13 is calculated from the scale and number of the PECVD reactors 18, the maximum dissolution amount corresponding to the maximum flow rate is obtained from the solubility of the gas 14 in the liquid 13, and it should be removed per unit time The amount of gas. The length of the tubular membrane 1 is obtained by deaeration with a deaeration apparatus equipped with the tubular membrane 1 having a unit length as a test, and by removing the amount of gas to be removed by the obtained deaeration flow rate per unit time. As a guideline.
[0036]
For example, when TEOS is supplied to about three chambers via the degassing device DG, a maximum flow rate of 500 ml / min is expected, and considering the solubility of helium gas, the inner diameter of the tubular body 2 is 10 mm, the tubular membrane 1 When the outer diameter is 6 mm, sufficient deaeration can be performed with a length of about 1 to 3 m.
[0037]
[Other Embodiments]
Hereinafter, other embodiments of the present invention will be described.
[0038]
(1) In the above-described embodiment, an example has been shown in which a straight tubular body is arranged in the vertical direction to form a bubble blocking portion, a gas reservoir is provided at the upper end portion thereof, and a tubular membrane is arranged inside. In order to easily increase the effective length for deaeration, a tubular body may be arranged as shown in FIG.
[0039]
In this example, the tubular body is arranged in an inverted N shape, and the bubble blocking portion FP is configured by the two tubular bodies 2 arranged in the vertical direction, and degassing can be performed also in the portion of the tubular body 2 arranged therebetween. It is like that. The configuration of the decompression pipe 7, the supply pipe 8, the gas reservoir 10, the discharge pipe 9, and the like is the same as that described above. 10 has the same function.
[0040]
(2) In the above-described embodiment, an example in which the deaeration device is configured mainly using a straight tubular body has been shown. However, in order to increase the effective membrane area (effective length), FIG. As shown, the deaerator may be configured using a tubular body 2 arranged in a spiral. In that case, by disposing the axial center of the helix in the horizontal direction, the bubble blocking portion FP in which the downstream side of the tubular body 2 is positioned below the upstream side can be effectively formed. Further, the vicinity of the upper end of the tubular body 2 arranged in a spiral shape can be used as the gas reservoir 10. Other configurations are the same as described above.
[0041]
(3) In the above-described embodiment, an example in which one tubular membrane is inserted into the tubular body has been described. However, a plurality of relatively small-diameter tubular membranes (such as hollow fiber membranes) may be inserted. In that case, the end of the tubular film may be sealed with a resin or the like. According to such a configuration, the effective membrane area of the tubular membrane is increased, so that the deaeration efficiency can be further increased.
[0042]
(4) The degassing apparatus and degassing method of the present invention are not used only in the PECVD system, but can be used in any degassing process that requires the supply of a liquid that does not contain bubbles or dissolved gas. . For example, it can be used for supplying various reaction raw material liquids, producing high-purity liquids, and producing ultrapure water.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a main part of an example of a deaeration device of the present invention. FIG. 2 is a schematic configuration diagram showing an example of use of the deaeration device of the present invention. FIG. 4 is a cross-sectional view showing a main part of an example of a conventional degassing apparatus.
DESCRIPTION OF SYMBOLS 1 Tubular membrane 2 Tubular body 3 Flow path 4 Inner space 10 Gas reservoir part 11 Heating wire (heating means)
FP bubble block

Claims (4)

While inserting a tubular membrane that allows the dissolved gas in the liquid to be treated to pass through the tubular body and forming a flow path for the liquid to be treated outside the tubular membrane, the inner space of the tubular membrane is in a reduced pressure state, A deaeration device in which at least a part of the tubular body is disposed such that the downstream side is positioned below the upstream side, and a bubble blocking unit is provided to prevent the generated bubbles from flowing downstream. The deaeration apparatus according to claim 1, wherein a gas reservoir is provided at an upper end portion of the bubble blocking portion, and the tubular membrane is disposed inside the gas reservoir. The deaeration device according to claim 1 or 2, wherein a heating means is provided on an outer peripheral portion of at least a part of the tubular body. The deaeration method which deaerates from the liquid chemical used for a semiconductor manufacturing process using the deaeration apparatus in any one of Claims 1-3.

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