JPH07265826A - Method and device for cleaning vacuum vessel - Google Patents

Abstract

PURPOSE:To clean a vacuum tunnel to be used for a magnetically levitated conveyor, etc., without disassembling it by using this device. CONSTITUTION:The inner wall of a vacuum vessel 1 deposited with a contaminant 2 is irradiated with ion or electron 5 to charge the contaminant 2, a current is applied through the inner wall of the vessel 1 to exert a repulsion on the charged contaminant 2 which is thereby released from the inner wall, and the contaminant 2 released from the inner wall is discharged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tunnel cleaning method and a cleaning apparatus, and more particularly to a method and apparatus for cleaning a vacuum tunnel such as a magnetic levitation transfer apparatus.

[0002]

2. Description of the Related Art In recent years, as the degree of integration of semiconductors has increased, even the existence of particles of 0.1 μm or less has become a problem, and a vacuum space in which particles do not exist has been receiving attention. In a vacuum, there is little or no air flow,
The particles adhering to the wall of the vacuum container are hardly peeled off or the particles on the floor surface are hardly blown up. Therefore,
Since there is a possibility that a class 0 space can be created in a vacuum, in recent years, not only the semiconductor manufacturing process, but also the transfer system for transporting a wafer to a process device and the storage of the wafer have tended to be performed in a vacuum. In this case, when the wafer is transferred in a vacuum, the wafer is placed in a narrow and long vacuum tunnel on a transfer table (cart) for transfer, and is transferred in a non-contact state inside the tunnel while being floated by magnetic force or the like.

However, even in a vacuum tunnel that was initially clean, the resist applied to the front surface of the wafer and the resist adhering to the back surface of the wafer may peel off and fall as they are used for a long time. Particles, particles flowing in from the process equipment, particles generated by dust generation due to opening and closing of the valve, and the like adhere to the walls of the vacuum tunnel and are gradually contaminated. Contaminant particles have a large particle size, and as the number of pollutant particles increases, the van der Waals force, which is an adhesive force, and the gravity, that is, the own weight of the particles, are unbalanced, and the particles are separated from the wall and fall. In this case, there is no air flow in the vacuum, or there is very little air flow, so the particles fall vertically. And
The falling particles attach to and contaminate the wafer being transferred, if it happens to be underneath.

For this reason, the vacuum tunnel must be regularly cleaned. If it is a process device,
Disassembly cleaning is possible. However, once a vacuum tunnel such as a magnetic levitation transfer device for transferring a wafer is disassembled, it is very troublesome to reassemble it and to adjust the axis and clearance.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the prior arts described above, and cleans a vacuum tunnel used in a magnetic levitation transfer device or the like without requiring disassembly or the like. It is an object to provide a method and a device.

[0006]

According to the method of cleaning a vacuum container of the present invention, the inner wall of the vacuum container on which contaminants are adhered is irradiated with ions or electrons to charge the contaminants to the inner wall of the vacuum container. A repulsive force is applied to the charged pollutants by applying an electric current to separate the pollutants from the inner wall, and the pollutants separated from the inner wall are discharged.

The vacuum container cleaning apparatus according to the present invention comprises means for irradiating ions or electrons on the inner wall of the vacuum container to which contaminants are attached to charge the contaminants, and a current for exerting a repulsive force on the charged substances. And a means for discharging and removing the contaminants peeled off from the inner wall of the vacuum container.

[0008]

In the cleaning method of the present invention, the contaminant attached to the inner wall of the vacuum container is charged by irradiating it with ions or electrons, and a current having a negative polarity is applied to the inner wall of the vacuum container to repel the contaminant. To peel off from the inner wall,
It is discharged and removed. Therefore, the vacuum tunnel used in the magnetic levitation transfer device is very troublesome to reassemble after once disassembling, such as adjusting the axis and clearance, but without disassembling such a narrow and long vacuum container, The inner wall can be cleaned and cleaned.
Further, in the case of cleaning the vacuum container, once wet cleaning is performed, water molecules adhere to the inner wall of the container, resulting in a decrease in vacuum degree. In order to desorb these water molecules, it is usually necessary to heat the vacuum container to a temperature of 100 ° C. or higher and perform baking for a long time.
Baking of a vacuum tunnel requires a lot of time and labor because the heating method and temperature control are difficult. According to this cleaning method, since it is a dry cleaning that does not use a liquid, a high degree of cleanliness can be obtained without generating a residue or the like and without requiring time and labor. Furthermore, since the present cleaning method consists of irradiating the inner wall of the container with ions or electrons and supplying an electric current to the inner wall of the container, the vacuum state is maintained without breaking the vacuum in the container. It can be washed as it is.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 4 shows the vacuum tunnel 1 and the cleaning apparatus of the invention associated therewith. The vacuum tunnel 1 is, for example, a thin and long vacuum container having a cross section of several tens of centimeters in which a semiconductor wafer is mounted on a transfer carriage and transferred in a vacuum atmosphere in a semiconductor manufacturing factory. In the vacuum tunnel 1 of the present embodiment, a load lock chamber 30 is provided at one end of the vacuum tunnel 1 via a valve V _5, and a washing vehicle 3 is provided. The washing car 3 is equipped with an irradiation device 4 for irradiating a negatively charged ion shower or electrons. Further, a load lock chamber 31 is provided at the other end via a valve V ₆ and a washing vehicle 3A is provided. The washing car is equipped with an electrode plate 10 having a positive (+) polarity. The electric wire 31 supplies electric power for traveling the washing cars 3 and 3A and electric power for the irradiation device or the electrode plate from the power source through the hermetically sealed flange 35. The vacuum tunnel 1 is connected to vacuum pumps 6 and 7 via a valve V ₁ and is evacuated. The vacuum tunnel 1 is connected to a leak pipe via a valve V ₂ . Further, a current supply means such as a power supply 8 and a switch 9 for supplying a negative current to the inner wall of the vacuum tunnel is provided.

1 to 3 show a vacuum tunnel cleaning method according to an embodiment of the present invention. Contamination gradually progresses as the vacuum tunnel 1 is used for a long time, and contaminants 2 such as organic substances adhere to the inner wall of the vacuum tunnel 1.
When it is detected that the inner wall of the vacuum tunnel is contaminated by using the vacuum tunnel for a certain period of time, the load lock chamber 30 is first evacuated, the valve V ₅ is opened, and the cleaning vehicle 3 is removed from the load lock chamber 30. Traveling inside the vacuum tunnel 1 to start cleaning. The washing car 3 is equipped with an irradiation device 4 capable of generating negative ion showers or electrons, and runs while uniformly showering the ion showers or electrons on the inner wall of the vacuum tunnel 1. As the ion or electron irradiation device 4, a thermoelectron electron gun as shown in FIG. 1 or a combination of an ultraviolet lamp and an electron emitting material as shown in FIG. 5 is used. In FIG. 1, reference numeral 5 indicates a negative charge, which is an electron or a negative ion, which is attached to the contaminant 2 and the contaminant 2 is negatively charged.

FIG. 5 shows the principle of an electron irradiation device using an electron emitting material and ultraviolet rays. This device uses an ultraviolet lamp 40
Is a device that utilizes the photoelectric effect of irradiating the electron emission material 41 with the electromagnetic wave energy to excite the electron emission material 41 to generate electrons. The ultraviolet lamp 40 as an electromagnetic wave energy source at this time is a high pressure mercury lamp, a low pressure mercury lamp,
There are various types such as xenon lamp, deuterium lamp, excimer laser, etc. Any lamp can be used, but cost /
For performance reasons, it is best to use a low-pressure mercury lamp covered with quartz glass. As the electron emitting material 41,
Although there are various metals, non-metals, metal oxides, ceramics, etc., a gold (Au) thin film whose surface state is relatively small even when exposed to the atmosphere is preferable. Further, as another ion shower source, a method using a radioactive substance such as americum (241Am) or krypton (85Kr) can be considered. However, these radioactive substances are dangerous to handle and troublesome to manage, and are not practical in view of environmental problems.

FIG. 2 shows a state in which the cleaning vehicle 3 travels in the vacuum tunnel 1 and irradiates the inner wall throughout, so that the negative charges 5 are attached to the respective contaminants 2 and are charged. Next, a negative current is applied to the charged pollutant 2 from the current supply means 8 and 9 to the inner wall of the vacuum tunnel 1.
Then, a repulsive force acts between the inner wall of the vacuum tunnel 1 and the charged pollutant 2, and if the magnitude of the repulsive force exceeds the van der Waals force, which is the adhesive force of the pollutant 2 to the inner wall, the pollutant 5 peels from the inner wall.

FIG. 6 is an explanatory view of the repulsive force acting on the charged contaminants attached to the inner wall of the vacuum tunnel. here,
This repulsive force is estimated by a model of 0.3 μm contaminant particles. The repulsive force is expressed by equation (1) in the figure and is 0.3μ
Since the equilibrium charge index charged to the particle of m is 1.3, it is calculated as one. At this time, the current flowing through the inner wall of the vacuum tunnel is set to 10 ⁻⁹ amperes. The number of electrons existing on the inner wall of the vacuum tunnel and contributing to the repulsive force is 1.8.
Assuming × 10 ⁺³ (the number of electrons gathered in 40 nm square is calculated), the peeling force due to the repulsive force is 0.262 dyn.
Van der Waals force of 0.3 μm at 2.90 × 10 ⁻³ d
Greater than yn and separated from the inner wall. However, although the case of 0.3 μm particles is described here, 0.3 μm
Since larger particles have a larger number of charges, the repulsive force is larger than the van der Waals force and the particles are separated. However,
Even if such work is performed, it is difficult to remove pollutants of 0.1 μm or less that are difficult to be charged, but particles of 0.1 μm or less are difficult to be peeled off. It is considered that there is little chance of adhering to and contaminating a semiconductor wafer, glass substrate, or the like that is being transported inside.

FIG. 3 shows the state of discharging charged pollutants. Where the contaminants have separated from the inner wall,
The load lock chamber 31 is evacuated, the valve V ₆ is opened, and the cleaning vehicle 3 A is run in the vacuum tunnel 1. The washing wheel 3A sucks and collects the pollutant 2 negatively charged by the electrode plate 10 having a positive (+) polarity by using electrostatic force. That is, the washing car 3A travels in the vacuum tunnel 1,
The pollutant 2 separated from the inner wall of the tunnel is discharged and removed.
When the cleaning of the above process is completed, the load lock chamber 3
The washing car 3A is stored in 1 and the valve V ₆ in the load lock chamber
Is closed and the inside of the vacuum tunnel 1 is returned to a normal exhaust state to be reused as a cleaned vacuum tunnel.

In the above embodiment, the cleaning is carried out without breaking the vacuum atmosphere. However, once the atmosphere is released, ions or electrons are irradiated to charge the contaminants, and a negative current is applied to the container. The repulsive force may be applied from the inner wall to collect the pollutants by using the positive electrode plate. In this case, it is not necessary to store the washing car equipped with the irradiation device and the collecting electrode in the load lock chamber. The contaminants may be collected by evacuating with a vacuum pump.

In the above description of the embodiments, the cleaning of the inner wall surface of a narrow and long vacuum tunnel used in a magnetic levitation transfer device or the like has been described, but the gist of the present invention is not limited to the vacuum tunnel, and various vacuum treatments are possible. Of course, it can be applied to the cleaning of the vacuum container of the device. When cleaning a vacuum container of a normal shape, instead of running a cleaning car, insert an ion or electron irradiation device into the vacuum container, and insert a collector plate of the positive electrode into the container. The wall can be cleaned. As described above, various modifications can be made without departing from the spirit of the present invention.

[0018]

As described above, according to the method and apparatus for cleaning a vacuum container of the present invention, even a vacuum container such as a narrow and long vacuum tunnel can be vacuumed without being disassembled. It is possible to clean the inner wall surface of the container by performing dry cleaning while maintaining the above condition.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a method for cleaning a vacuum tunnel according to an embodiment of the present invention, showing a state in which a shower of ions or electrons is irradiated on the inner wall surface of a container.

FIG. 2 is an explanatory diagram of a vacuum container cleaning method according to an embodiment of the present invention, showing a state in which a repulsive force is exerted on a charged contaminant by supplying an electric current to the inner wall surface of the container and the contaminant is separated from the inner wall surface.

FIG. 3 is an explanatory view of a vacuum container cleaning method according to an embodiment of the present invention, showing a state in which contaminants are separated from an inner wall surface and collected by a cleaning vehicle having a positive polarity electrode plate.

FIG. 4 is an explanatory diagram of a tunnel cleaning device according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram showing the principle of electron emission by an ultraviolet lamp and an electron emitting material.

FIG. 6 is an explanatory view of the repulsive force acting on the charged contaminant particles attached to the inner wall of the vacuum tunnel.

[Explanation of symbols]

 1 Vacuum Tunnel (Vacuum Container) 2 Pollutant 3, 3A Cleaning Vehicle 4 Ion or Electron Irradiation Device 5 Electron 6,7 Vacuum Pump 8, 9 Current Supply Means

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B65H 5/00 J H01L 21/02 Z 21/68 A (72) Inventor Tsuyoshi Yoshioka Fujisawa City, Kanagawa Prefecture 4-2-1 Motofujisawa Ebara Research Institute Co., Ltd.

Claims (6)

[Claims] 1. A vacuum container inner wall to which a pollutant adheres is irradiated with ions or electrons to charge the pollutant, and a current is applied to the inner wall of the vacuum container to exert a repulsive force on the charged pollutant. A method of cleaning a vacuum container, characterized in that it is peeled off from the inner wall and the contaminants peeled off from the inner wall are discharged. 2. The method for cleaning a vacuum container according to claim 1, wherein the method of irradiating the inner wall of the vacuum container with ions or electrons uses thermionic emission. 3. The method of cleaning a vacuum container according to claim 1, wherein the method of irradiating the inner wall of the vacuum container with ions or electrons is to irradiate the electron-emitting material with ultraviolet rays to emit electrons. . 4. A means for irradiating ions or electrons to the inner wall of a vacuum container to which a contaminant adheres to charge the contaminant, a means for supplying an electric current for exerting a repulsive force to the charged substance to the inner wall of the vacuum container, and the vacuum. A cleaning device for a vacuum container, comprising: means for discharging and removing contaminants peeled from the inner wall of the container. 5. The method of cleaning a vacuum container according to claim 1, wherein the ions or electrons are irradiated onto an inner wall of the vacuum container by a cleaning car that travels in the vacuum container. 6. The cleaning of a vacuum container, wherein the contaminants separated from the inner wall are collected by a positive polarity electrode plate mounted on a cleaning vehicle running in the vacuum container. Method.