JP2016223636A - Dry method for inner surface of container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique of effectively removing water droplet (moisture) adhering to the inner wall of a container.SOLUTION: A method for drying the inner wall of a container includes a suction/exhaustion step of suctioning/exhausting gas in the container, and a dried gas supply step of supplying dried gas to the container. In the method, the suction/exhaustion and the dried gas supply are performed simultaneously, the time for which the suction/exhaustion and the dried gas supply are continuously performed simultaneously is 20 minutes or more, a supply amount of dried gas is 0.1 L/min or more, and pressure in the container at the time when the suction/exhaust and the dried gas supply are performed simultaneously is 0.1-15 kPa.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a drying technique.

  Conventionally, as a method for drying the container (removing water adhering to the inner wall of the container), a method of heating the container and exhausting the gas in the container using a vacuum pump has been used.

  Even with this drying method, there was no problem with ordinary substances.

  However, when a substance such as a high-purity compound is filled in a container in which the drying method has been performed, various problems have been expected. For example, a compound having high reactivity with water cannot be filled in a container with insufficient moisture removal. Even compounds with low reactivity are problematic when high purity is required.

  For this reason, the conventional water removal technology was not satisfactory.

  Incidentally, there has been proposed a drying apparatus comprising a vacuum vessel, an inert gas supply means for supplying a heated inert gas to the vacuum vessel, and a vacuum pump for evacuating the vacuum vessel (Japanese Patent Laid-Open No. 6-69180). It was. The vacuum container includes an inert gas inlet and an inert gas outlet. The drying apparatus has been developed as a drying apparatus for semiconductor devices.

  The details of the drying apparatus are as follows. The drying device includes a vacuum container, a vacuum pump, and an inert gas heating supply unit. The vacuum container has a mesh-like floor. Water droplets adhering to (containing) the product (substance to be dried) set in the vacuum container pass through the mesh structure and drop off. The floor is tapered toward the center. Thereby, the water droplet which fell from the floor part falls smoothly. An exhaust pipe is connected to the tip of the tapered portion. Water droplets are discharged through the exhaust pipe. A drain valve is provided below the exhaust pipe. The vacuum pump is connected to the vacuum vessel by a main vacuum line branched from the exhaust pipe and a preliminary evacuation line. The gas in the vacuum vessel is exhausted by a vacuum pump. At this time, the degree of vacuum in the vacuum vessel is detected and controlled by a vacuum sensor. The line is provided with a valve.

  The drying apparatus operates as follows. The vacuum vessel is opened. A wet product (undried silicon wafer) is placed on the mesh floor. After this, the vacuum vessel is closed. Leave for a few minutes. Thereby, draining is carried out. After draining, the drain valve is closed. Thereafter, heated inert gas is supplied into the vacuum vessel. At the same time, the pre-evacuation (or main evacuation) valve is opened, and the pressure in the container is maintained at 100 to 5 torr. That is, an inert gas is supplied so as to achieve the pressure. This state is left for 1 to 5 minutes. Thereafter, the valve is closed. The inert gas is allowed to flow as it is. Therefore, the pressure in the vacuum vessel returns to atmospheric pressure. The process (operation) was repeated several times. In this way, the silicon wafer was dried.

JP-A-6-69180

  If the drying apparatus of the above-mentioned patent document is used, it is said that the silicon wafer placed in the vacuum vessel is dried. It is considered that water droplets (water) adhering to the silicon wafer have been removed.

  By the way, the drying apparatus of the said patent document dries the silicon wafer arrange | positioned in the said drying apparatus (inside a vacuum vessel). The silicon wafer is disposed in a container. Drying is removal of water droplets adhering to the silicon wafer. The silicon wafer is present in the container. Therefore, the drying of the silicon wafer is considered to be the drying of the inner wall of the container at the same time.

  In this regard, a supplementary test was conducted by the present inventors. That is, the technique described in the example of the patent document has been implemented.

  For example, the gas in the metal container was exhausted by a vacuum pump. Along with this exhaust, dry nitrogen gas was supplied (supply amount: 1.5 L / min, moisture concentration of about 5 ppb). This evacuation / supply was performed for the time described in the examples of the patent document, that is, for 5 minutes.

  After this (after 5 minutes), the valve A was closed and the exhaust by the vacuum pump was stopped. However, the supply of dry nitrogen gas was continued. That is, dry nitrogen gas was continuously supplied. After 12 minutes (12 minutes after stopping the vacuum pump), the pressure in the metal container became 1 atm. When the pressure in the metal container reached 1 atm, the valve A was opened again, and evacuation by the vacuum pump was resumed. Also in this exhaust process, dry nitrogen gas is supplied as described above. This evacuation and supply was performed for 5 minutes.

  Thereafter, the exhaust by the vacuum pump was stopped by closing the valve A again. However, the supply of dry nitrogen gas was continued. After stopping the vacuum pump, dry nitrogen gas was continuously supplied. After 12 minutes, the pressure in the metal container became 1 atm. When the pressure in the metal container reached 1 atm, the valve A was opened again and evacuation by the vacuum pump was resumed. Also in this exhaust process, dry nitrogen gas is supplied as described above. This evacuation and supply was performed for 5 minutes.

  Thereafter, the exhaust by the vacuum pump was stopped again by closing the valve A again. However, the supply of dry nitrogen gas was continued. After stopping the vacuum pump, dry nitrogen gas was continuously supplied. After 12 minutes, the pressure in the metal container became 1 atm. When the pressure in the metal container reached 1 atm, the valve A was opened again and exhausting was resumed. In this exhaust process, unlike the above, the supply of dry nitrogen gas was stopped. This evacuation was performed for 5 minutes.

  Thereafter, the moisture concentration in the metal container was measured. The water concentration in the metal container was about 160 ppb.

  This value (160 ppb) is the moisture concentration (225 ppb in the metal container when the metal container is heated while the gas in the metal container is continuously exhausted using a turbo molecular pump for 16 hours. ), It was good.

  However, this level of drying (160 ppb) was not satisfactory.

  Therefore, this invention is providing the technique from which the water droplet (water | moisture content) adhering to the container inner wall is removed effectively in a short time.

The present invention
A method for drying the inner wall of a container,
A suction exhaust process in which the gas in the container is sucked and exhausted, and a dry gas supply process in which a dry gas is supplied into the container,
The suction exhaust and the dry gas supply are performed simultaneously,
The time that the suction exhaust and the dry gas supply are performed simultaneously and continuously is 20 minutes or more,
The dry gas supply amount is 0.1 L / min or more,
A drying method is proposed in which the pressure in the container is 0.1 to 15 kPa.

  The present invention proposes the drying method, characterized in that the suction exhaust is not substantially stopped within the time in which the suction exhaust and the dry gas supply are performed continuously at the same time. To do.

  The present invention proposes a drying method, characterized in that the container has an internal volume of 5 to 1500 L.

  The present invention proposes a drying method, wherein the container is made of metal.

  The present invention proposes a drying method, further comprising a heating step in which the container is heated.

  According to the present invention, the moisture adsorbed on the inner wall of the container was effectively removed in a short time. For example, the moisture concentration could be dried to 100 ppb or less.

Schematic of an apparatus in which the drying method of the present invention is carried out

  The present invention is a drying method. In particular, it is a method for drying the inner wall of the container. The container is, for example, a cylinder. Or it is piping. The volume of the container is, for example, 5 to 1500 L. The drying method includes a suction exhaust process in which the gas in the container is sucked and exhausted, and a dry gas supply process in which the dry gas is supplied into the container. The suction exhaust and the dry gas supply are performed simultaneously. The time during which the suction exhaust and the dry gas supply are continuously performed simultaneously is 20 minutes or more. The dry gas supply amount is 0.1 L / min or more. The dry gas preferably has a moisture concentration of 100 ppb or less.

  Preferably, the suction exhaust is not substantially stopped within the time in which the suction exhaust and the dry gas supply are performed simultaneously and continuously.

  The pressure in the container when the suction exhaust and the dry gas supply are simultaneously performed is preferably 0.1 to 15 kPa.

  In the suction exhaust process and the dry gas supply process, the container is preferably heated. That is, when the heating process was performed, the moisture removal effect was high. The heating temperature is, for example, 80 ° C.

  Hereinafter, more specific embodiments will be mentioned. However, the present invention is not limited only to the following embodiments. Various modifications and application examples are also included in the present invention as long as the features of the present invention are not greatly impaired.

[Example 1]
FIG. 1 is a schematic view of an apparatus in which the drying method of the present invention is carried out.

  In FIG. 1, 1 is a metal (for example, stainless steel) container (cylinder). The internal volume is 19L. 2 is a gas injection pipe. 3 is a gas discharge pipe. The gas injection pipe 2 and the gas discharge pipe 3 are attached to the container 1. A dry gas (for example, dry nitrogen gas having a moisture concentration of about 5 ppb) is injected into the container 1 through the gas injection pipe 2. The gas in the container 1 is discharged to the outside through a gas discharge pipe 3 by a vacuum pump. 4 is a valve provided in the flow path.

  The apparatus was operated as follows.

  First, the inside of the metal container 1 was maintained in a vacuum state by a vacuum pump.

  Next, dry nitrogen gas was supplied into the metal container 1 through the pipe 2. The suction exhaust and the dry nitrogen gas supply are performed simultaneously. Of course, it does not matter if either one starts earlier. However, at the time when a certain amount of time has passed since the switch was turned on (in the stable operation state), both the suction exhaust and the dry nitrogen gas supply are continued. The continuation time (continuous continuation time) was 50 minutes. The dry nitrogen gas supply amount was 1.5 L / min. The internal pressure in the metal container 1 was 5 kPa, although some fluctuation was observed. The metal container 1 was arrange | positioned in the heating furnace, and was hold | maintained at 80 degreeC.

  The water concentration in the metal container 1 after the above 50 minutes was measured. The result was 95 ppb. This value was much improved as compared with the case of conforming to the method of the patent document.

[Example 2]
It carried out according to Example 1. However, in this example, the drying time (continuous continuation time between suction exhaust and dry nitrogen gas supply) was 5 hours. The measured water concentration in the metal container 1 after 5 hours was 40 ppb.

[Example 3]
It carried out according to Example 1. However, in this example, the drying time (continuous continuation time of suction exhaust and dry nitrogen gas supply) was 16 hours. The measured water concentration in the metal container 1 after the elapse of 16 hours was 30 ppb.

The following can be understood from the method of this example and the method of the comparative example (the method described in the example of Patent Document 1).
(1) Compared with the method described in Patent Document 1, the method described in the present example has a higher effect of removing moisture attached (bonded) to the inner wall of the metal container in each stage.
(2) Removal of water adhering (bonding) to the inner wall of the metal container is performed in a short time.

Claims (5)

A method for drying the inner wall of a container,
A suction exhaust process in which the gas in the container is sucked and exhausted, and a dry gas supply process in which a dry gas is supplied into the container,
The suction exhaust and the dry gas supply are performed simultaneously,
The time that the suction exhaust and the dry gas supply are performed simultaneously and continuously is 20 minutes or more,
The dry gas supply amount is 0.1 L / min or more,
The drying method characterized in that the pressure in the container when the suction exhaust and the dry gas supply are simultaneously performed is 0.1 to 15 kPa. 2. The drying method according to claim 1, wherein the suction exhaust is not substantially stopped within a time in which the suction exhaust and the dry gas supply are continuously performed simultaneously. The drying method according to claim 1, wherein the container has an internal volume of 5 to 1500 L. The drying method according to claim 1, wherein the container is made of metal. The drying method according to claim 1, further comprising a heating step in which the container is heated.

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