JPS60114319A - Powder trap - Google Patents

Abstract

PURPOSE:To remove fine powder which can not be collected with an existing powder trap with small resistance by rotating a hollow drum contg. a dust adhesive body and provided with air-permeable pores on the circumferential surface so that the drum may be immersed in an oil layer. CONSTITUTION:A gas entraining fine powder flows into a hermetic chamber 3 through a gas inlet 1, strikes against the circumferential surface 5 of a hollow drum 7, and flows into the drum through gas-permeable pores 6. The fine powder which enters the drum 7 is adhered to an oil film on the surface of a solid powder adhesive body 8, immersed into an oil layer 4 by the rotation of the drum 7, and washed. The greater part of the inflowing gas and the powder is brought into contact with said adhesive body 8. Since each of said adhesive bodies 8 moves individually and at random, the powder comes in close contact with the oiled surfaces. In addition, since the adhesive bodies 8 come into contact with each other and rub each other, the deposited powder can be washed off into the oil. The inflowing gas is passed through a wire gauze or a baffle 12, and sucked by an oil rotary pump 15 through a gas outlet 2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a powder trap suitable for use in a vacuum pumping system.

The vacuum evacuation systems used in recent semiconductor manufacturing processes often contain fine particles of several micrometers or less, and since these fine particles cannot be collected by conventional powder traps, the evacuation system is It reaches the oil rotary pump and clogs it,
This causes accidents that result in the driver being unable to drive. In general, vacuum evacuation systems in semiconductor manufacturing businesses are often equipped with a mechanical booster pump at the front stage and an oil rotary pump at the rear stage, but since the inside of the mechanical booster pump is dry, it may fail due to clogging with fine particles. is less than that of an oil rotary pump, but since an oil rotary pump has oil inside, it is easily clogged with powder, so a powder trap is provided in the exhaust system ahead of the oil rotary pump.

Here, a conventional powder trap will be explained.

Figure 1 shows an oil filtration device e equipped with an oil filter element d using an oil feed pump C to transfer the oil tank b of an oil rotary pump a.
A part of the powder that enters from the intake port f is discharged from the pump exhaust valve into the oil tank b along with the oil, so it can pass through the element d, but the powder that enters the pump a is Since the surfaces of the inner surface of the cylinder g and the rotor h1 rotor blades are wet with oil, some powder may adhere there and clog in small gaps, air supply ports, or the oil circulation path in the oil rotary pump. However, there is a drawback that eventually a lack of lubrication occurs and operation becomes impossible. Figure 2 shows a filter element J installed in front of a vacuum pump 1 consisting of a mechanical booster pump or an oil rotary pump.Normally, the powder that can be captured by this filter element is limited to about 10 microns, which is important in semiconductor manufacturing processes. If the element j is formed to be less than a few microns in size in order to capture the fine powder of several microns generated in the process, a large resistance will be generated in a vacuum, so an element j with a very large passing area must be used as the element j. Further, if fine powder adheres to the element j, the passage resistance increases, so that the effective evacuation speed of the vacuum pump decreases, and the pressure of the semiconductor manufacturing process to be evacuated increases. Generally O
In semiconductor manufacturing processes such as VD'p etching, it is necessary to maintain a constant vacuum pressure while flowing a constant amount of gas.
As mentioned above, an increase in pressure is undesirable because it causes defective products.

Furthermore, it is known that an oil trap l is provided in front of the vacuum pump as shown in Figure 3, and gas collides with the oil layer m to cause powder to adhere to the oil surface and precipitate.
Although it is effective for heavy powder of micron size or larger, it has the disadvantage that after the fine powder covers the oil surface, it flies into the pump along with the gas.

Furthermore, cyclone type traps are also known, but although they are effective against heavy powders such as metal powders, they are almost ineffective against fine powders.

The purpose of this invention is to remove the fine particles that cannot be captured by conventional powder traps with minimal resistance.In addition to providing an oil layer in a sealed chamber equipped with an intake port and an exhaust port, ventilation holes are formed in the circumference. A hollow drum is rotatably provided so that its circumferential surface is sequentially immersed in an oil layer, and a cylindrical or other solid powder adhering body is accommodated in the hollow drum.

Embodiments of the present invention will be explained with reference to the drawings. In FIG. 4 and FIG. Exhaust port, (4) is iron base (3
) The oil layer (7) formed by the oil injected into the surrounding surface (5)
A hollow drum (8) is a cylindrical or other solid powder adhering body housed in the drum (7), and the hollow drum (7) is, for example, a closed chamber (3). It is placed horizontally in a horizontal cylindrical chamber (3a) below. In this case, an inlet (1) and an outlet (2) are provided in the upper vertical cylindrical chamber (3b), and a conduit (9) is connected to the inlet (1) to connect the circumferential surface (5) of the hollow drum (7). ) is configured such that the exhaust fluid impinges on the exhaust fluid. For example, the hollow drum (7) is equipped with a rotating shaft (tG) in its axial direction as shown in FIG. The circumferential surface (5) was rotated so that it was sequentially immersed in the oil layer (4). (13 is a wire mesh or is a baffle, α4 is a mechanical booster pump connected in front of the air supply port (1), and α9 is an oil rotary pump connected to the exhaust port (2).

To explain its operation, when gas containing fine powder from semiconductor manufacturing equipment flows into the sealed chamber (3) through the intake port (1), it collides with the circumferential surface (5) of the hollow drum (7). It passes through the vent hole (6) and flows into its interior. The peripheral surface (5
) The fine particles that come into contact with the drum (7) adhere to the oil film on its surface and
) When it is immersed in the oil layer (4) below, it becomes heavy and eventually settles. The fine powder that has entered the drum (7) adheres to the oil film on the surface of the solid powder adhesion body (8) and is also transported to the drum (7).
) is immersed in the oil layer (4) and washed. Most of the gas and powder flowing in come into contact with the powder adhering bodies (8) inside the drum (7), but since each adhering body (8) moves indiscriminately, a large amount of oil is absorbed. Since they come into contact with a wet surface and the adherent bodies (8) come into contact with each other and rub against each other, the adhered powder can be washed away into the oil. The inflow gas then passes through a wire mesh or baffle C121 to the exhaust port (2
) to the oil rotary pump (151).The drum (7
1 ventilation hole (6) from Weiyang to 10long or more, and attached body (
Even if the size of 8) is larger than that, fine powder can be sufficiently attached and captured, and the passing resistance thereof is also small. It is also possible to add the oil regeneration filtration device to regenerate the oil layer (4), and the drum (7), the adhesion body (8), etc. are made of a corrosion-resistant material such as ceramic or stainless steel, so that the oil layer (4) is not corrosive. It is also possible to remove fines from the gas. Further, as the oil in the oil layer (4), in addition to petroleum-based oil, dark purple oil or the like may be used to enhance corrosion resistance or nonflammability.

In this way, according to the present invention, the hollow drum containing the powder adhering body and having ventilation holes formed on the circumferential surface is rotated so as to be immersed in the oil layer, so that the fine powder in the gas can be efficiently captured and the passage resistance can be reduced. It is possible to reduce the size of the vacuum pump, prevent the operation of the vacuum evacuation system from being impaired, and make the device smaller.

[Brief explanation of the drawing]

1 to 3 are explanatory diagrams of the conventional example, FIG. 4 is a cut side view of the embodiment of the present invention, and FIG. 5 is a cross-sectional view taken along line V-V,
FIG. 6 is a perspective view of the hollow drum. (1)...Intake port (2)...Exhaust port (3
)...Sealed chamber (4)...Oil layer (5)...
Phase (6)...Vent hole (7)...Hollow drum (8)...Powder adhered body patent applicant 2 people other than Japan Vacuum Technology Co., Ltd. -105=

Claims (1)

[Claims] An oil layer is provided in a sealed chamber with an intake port and an exhaust port, and a hollow drum with ventilation holes formed on its circumferential surface is rotatably provided so that its sides are sequentially immersed in the oil layer. A powder trap that accommodates a powder-adhered body.