JPH04263426A - Vapor drying device - Google Patents

Abstract

PURPOSE:To reproduce and reuse isopropyl alcohol by selectively providing a film-separating device, which is composed of a water-transmitting film, in the vapor-filled space above the surface of the drying liquid in a vapor- generating section. CONSTITUTION:The vapor of isopropyl alcohol(IPA), which is heated up by a heater block 4 and evaporated, is filled up in the part, which is lower than the vapor surface 7, of a vapor drying section 1. At this point, when the material 5 to be dried up such as an electronic part and the like is retained in the vapor drying section, IPA vapor is conde sed on the surface of the material 5 to be dried up. The highly hydrofilic IPA flows down together with the moisture adhered to the surface of the material 5 to be dried up. The material 5 to be dried is dried up by repeating the aforesaid condensation and flowing down. Also, the moisture contained in the IPA vapor is removed by a film- separating device 8.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drying apparatus suitable for drying precision products such as electronic parts.

0002

2. Description of the Related Art There is a so-called steam drying method as a method for drying an object to be treated after washing with water. The above drying method is performed using a drying liquid made of an organic solvent having a high affinity for water and a low boiling point, such as isopropyl alcohol (hereinafter also referred to as "IPA"). Specifically, for example, this can be carried out using an apparatus whose basic configuration includes a cooling section above and a heatable steam generation tank below. When the material to be dried is placed in the space above the steam generating tank,
IPA vapor evaporated from the heated steam generation tank condenses on the surface of the object to be treated. Since the condensed IPA flows down with the attached moisture, drying of the material to be dried is achieved.

0003

[Problem to be solved by the invention] If IPA that has condensed on the surface of an object to be dried is dropped into a drying liquid tank, the concentration of water dissolved in the IPA in the tank will quickly increase and evaporate. The moisture concentration in the IPA vapor also increases. As a result, drying efficiency will be reduced. Therefore, it is conceivable to discard all of the IPA that has condensed on the surface of the material to be dried, and to create a structure that prevents it from entering the steam generation tank. In this way, it is possible to prevent moisture from directly entering the IPA in the tank.

However, within the apparatus, the IPA vapor that has not condensed on the surface of the object to be dried is refluxed in the upper cooling section, returned to the drying liquid tank, heated again, and repeatedly evaporated. On the other hand, even though the structure is such that it does not directly enter the steam generation tank, a small amount of water evaporates directly from the water droplets attached to the material to be dried, and the water vapor is transferred to the IPA.
It will be refluxed together with steam. Therefore, as the drying process is repeated, the water concentration of the drying liquid in the tank also increases, causing the above-mentioned problems.

It is known that the above problem is particularly important when the object to be dried is a semiconductor wafer. The drying device is described in "Electronic Materials", March 1983 issue, pages 68 to 71, published by Kogyo Kenkyukai Co., Ltd.

[0006] In addition, as a measure to solve the above-mentioned problems, a technique for automatically controlling the water vapor present in the drying liquid vapor in a steam drying apparatus to a low concentration was disclosed in Japanese Patent Laid-Open No. 62-45127.
Disclosed in the issue. This technology is a steam drying device equipped with means for disposing of drying liquid in a steam generation tank and means for supplying new drying liquid, and when the moisture concentration in the drying liquid in the steam generation tank reaches a predetermined value, By discarding all or part of the drying liquid in the tank and replenishing it with new drying liquid,
The moisture concentration in the drying liquid in the steam generation tank can be controlled to a predetermined value or less, and at the same time, the water vapor concentration in the drying liquid vapor evaporated from the steam generation tank can also be controlled to a predetermined concentration or less. It is something that can be achieved.

[0007] Although it is possible to control the water concentration in the drying liquid by this method, the above method requires constant replenishment of new IPA, which increases costs and also makes it difficult to dispose of used IPA. Processing issues also arise.

[0008]

[Means for Solving the Problems] As a result of intensive studies, the present inventors have solved the above problems by installing a membrane separation device in a space filled with steam above the drying liquid in the steam generation section. That is, the gist of the present invention is a steam drying apparatus for drying a processed object after washing with water, which includes a steam generating section that heats a drying liquid to generate vapor of the drying liquid, and a steam generating section that dries the processed object using the generated steam. and a membrane separation device constituted by a membrane that selectively permeates water in a space filled with steam above the dried liquid level in the steam generating section. Located in steam drying equipment.

The present invention will be explained in detail below. The steam drying apparatus of the present invention mainly includes a steam generation section, a steam drying section, and a membrane separation device located in a space filled with steam above the surface of the drying liquid in the steam generation section. The drying liquid is an organic solvent that has a high affinity with water, and an organic solvent that has an azeotropic point with water is suitable. Examples of such organic solvents include alcohols such as isopropyl alcohol (IPA), ethanol, n-propanol, isobutanol, and isoamyl alcohol, and chlorinated hydrocarbons such as methyl chloride, methylene chloride, and carbon tetrachloride. Among these, IPA is particularly suitable. Although IPA will be explained below as an example of the drying liquid, the present invention is not limited to IPA.

[0010] In the present invention, a membrane separation device constituted by a membrane that selectively permeates water into the IPA vapor above the steam generation section is installed. This results in IP with a high moisture concentration.
A can be recycled and the water concentration in IPA can be controlled.

[0011] In the above-mentioned membrane separator, most of the water contained in IPA is usually removed by the vapor permeation method. As the membrane separation device, any known device may be used without particular limitation as long as it uses a membrane that can selectively permeate water in an IPA-water system. As a separation membrane, the vapor permeability coefficient is 0.1 kg/m2 - Hr or more, preferably 1 kg/m2 - Hr or more, and the separation coefficient is 1
00 or more, preferably 1000 or more is suitably used. In addition, the separation coefficient is

0012

[Math 1]

It is expressed as:

[0014] The operating conditions of the membrane separator are that the temperature on the primary side is 6
0 to 120℃, the degree of vacuum in the permeation vapor chamber of the membrane separator is 0 to 120℃
It is preferable to conduct the heating at a pressure of 100 Torr. In this way, water is removed from IPA by the membrane separator, but a small amount of IPA migrates to the permeation vapor chamber depending on the separation coefficient value, resulting in a loss of IPA. However, using a membrane separator with the above-mentioned permeability coefficient and separation coefficient, 10% hydrated IPA
Even when dehydrating IPA from 500 ppm to 500 ppm, the loss of drying liquid is generally less than 5%, which is much more economical than replacing the entire amount with fresh liquid periodically.

[0015] The amount of water removed by the membrane separation device may be the majority of the water in IPA, but especially when used in a precision cleaning process for semiconductor wafers, the water content is important from the viewpoint of quality. It is desirable to remove water so that the amount is reduced to 1% or less, preferably 500 ppm or less based on IPA.

[0016] Also, to specifically show the equipment and conditions in which the vapor permeation method is adopted, the equipment basically has two chambers, a primary side and a secondary side, separated by a hollow fiber separation membrane. things are commonly used. Furthermore, a so-called hollow fiber module type device in which hollow fiber separation membranes are bundled is suitable as the device. Further, the number of hollow fiber membrane modules to be arranged can be increased within the range permitted by the layout.

[0017] Here, the hollow fiber membrane modules include those in which both ends of a large number of hollow fiber membranes are open and fixed with resin (double-end open module), and those in which one end is sealed and the other end is open and resin is used. A module that is used by adhesively fixing it (one-end sealed module) is known. Such a module bundles at least one end of a large number of hollow fiber membranes, and fixes the bundled ends with an adhesive to prevent the bundle from coming apart.

[0018] For this adhesive, thermosetting resins such as bisphenol type, novolac type, and various epoxy resins are preferably used. Moreover, polyester resin, phenol resin, melamine resin, etc. can also be used.

Preferred examples of hollow fiber membrane materials include polysulfone, polyethersulfone, polyimide,
Examples include polyphenylene acetylene, but any porous support film may be used as long as it is made of a material whose softening point is 40° C. or higher than the steam treatment temperature.

The present invention will be explained below with reference to the drawings. Figure 1
FIG. 1 is a schematic diagram showing an example of a steam drying apparatus of the present invention. 1
2 is a steam drying section, and 2 is a steam generating section. IPA3, which is a drying liquid, is stored in the steam generating section 2. A heater block 4 for heating and evaporating IPA is installed under the bottom of the steam generating section 2. A material to be dried 5 is held in the steam drying section 1, and a cooling pipe 6 is installed above it. A membrane separator 8 is installed above the IPA liquid level in the steam generating section 2 . Note that the present invention is not limited to the type shown in FIG. 1 in which the steam drying section is disposed above the steam generation section. If the solvent condensed droplets on the surface of the object to be treated are guided to the steam generation section, it is also applicable to a type in which the steam generation section and the steam drying section are separated.

[0021]

[Operation] Next, the operation of the present invention will be explained with reference to FIG. The area below the steam surface 7 of the steam drying section 1 is filled with IPA steam heated and evaporated by the heater block 4. When the material to be dried 5 is held in the steam drying section, IPA vapor condenses on the surface of the material to be dried 5. The highly hydrophilic IPA flows down together with the moisture adhering to the surface of the material to be dried 5. By repeating this condensation and flowing down, the material to be dried is dried. Moisture contained in IPA vapor is removed by membrane separator 8.
removed by

[0022]

[Examples] The present invention will be explained in detail with reference to Examples below, but the present invention is not limited by the Examples unless it exceeds the gist thereof. Example 1 As a hollow fiber membrane module, a one-end sealed module was used in which polyimide was used as the material for the hollow fiber membrane and the bundle end was fixed using an epoxy resin adhesive. After the silicon wafers for semiconductor substrates were immersed in an ultrapure water bath, they were sent to an IPA steam drying device at 5 minute intervals to perform 20 batches of steam drying treatment. At this time, the amount of moisture adhering to the silicon wafer and the holding jig set was 20 [g/set]. In other words, the amount of moisture brought into the silicon wafer is 240 [g/
Hr]. Here, the amount of IPA and retained liquid in the steam generation section of the IPA steam drying apparatus is 60 [l] = 48 [kg]. The IPA retentate is maintained at a boiling point of 82 [°C], and the primary side of a heat-resistant resin hollow fiber separation membrane is placed in the space filled with steam above the solvent level in the steam generation section, and the secondary side is evacuated. Degree 10T
FIG. 2 shows the results of measuring the moisture concentration in the IPA liquid in the steam generating section when steam drying of the silicon wafer was carried out while adjusting the temperature to 0.0 or more. Here, the IPA poured into the steam generation section before the start of treatment has a water content of 500 [ppm].
] product was used. Incidentally, IPA, which was slightly reduced due to vapor permeation, was automatically replenished with IPA of the same specification as above so that the liquid level in the steam generation section was constant.

[0023]

Effects of the Invention The steam drying device of the present invention provides stable and reliable performance by reusing IPA with a high water concentration by providing a membrane separator and at the same time controlling the water concentration in IPA vapor. High processing conditions can be reasonably achieved. Furthermore, since the treated liquid is used repeatedly without being completely discarded, waste liquid treatment becomes unnecessary and a significant cost reduction can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of a steam drying apparatus of the present invention.

FIG. 2 is a graph showing changes in water content in IPA in Examples.

[Explanation of symbols]

1 Steam drying section 2 Steam generation section 3 Drying liquid (IPA) 4 Heater block 5. Materials to be dried 6 Cooling pipe 7 Evaporation surface 8 Membrane separation equipment

Claims (1)

[Claims] 1. A steam drying device for drying a processed object after washing with water, comprising: a steam generating section that heats a drying liquid to generate vapor of the drying liquid; and a steam drying device that dries the processed object using the generated steam. 1. A steam drying device comprising a membrane separation device comprising a membrane that selectively permeates water in a space filled with steam above the drying liquid level in the steam generating portion.