JP3563152B2 - Vacuum pump - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a vacuum pump, and more particularly to a dry vacuum pump for exhausting a gas which is liquefied or solidified at a normal temperature, a normal pressure or a state close to the normal temperature, which is generated in a semiconductor manufacturing process such as low pressure CVD and dry etching.
[0002]
[Prior art]
In recent years, dry vacuum pumps that do not use oils for sealing and lubrication have been used in semiconductor manufacturing equipment and the like in order to create a clean vacuum, and in particular, multi-stage vacuum pumps made of cast iron or stainless steel have been widely used. Have been. Figure 3 is a block diagram of a multi-stage vacuum pump 100 of this cast iron, a vacuum pump unit 110,112,114,116,118,120 six stages are connected in series by the flow path L _1. Portions between the flow path L ₁ of the vacuum pump unit 116 and 118, the portion between the 118 and 120 are cooler 134 and 136 interposed for cooling the gas passing through the flow path L ₁ since the gas is prevented from become extremely high temperature by the heat of compression, so as to cool by the cooling water flowing through the flow path l _1.
[0003]
By the way, in the semiconductor manufacturing process, low-pressure CVD for dry etching of aluminum using a chlorine-based gas or film formation of silicon nitride (Si ₃ N ₄ ) using dichlorosilane (SiH ₂ Cl ₂ ) and ammonia (NH ₃ ) as source gases. In such a case, an aluminum chloride (AlCl ₃ ) gas or an ammonium chloride (NH ₄ Cl) gas generated by the reaction solidifies (sublimates) at normal temperature, normal pressure or a state close to it, so that this gas is a vacuum pump near normal temperature. It is known that there is an inconvenience of being cooled to a solidification temperature or lower by being taken in, becoming a solid-state reaction product, and adhering and accumulating on each part of the flow path.
[0004]
Generally, a substance takes one of a gas phase, a liquid phase, and a solid phase depending on its temperature and pressure. FIG. 2 is a diagram showing a saturated vapor pressure curve S of a substance which solidifies at normal temperature, normal pressure, or in a state close to normal temperature, similar to AlCl ₃ and NH ₄ Cl, and is lower than the saturated vapor pressure curve S (right side). , The substance is in a gaseous state, and exhibits a liquid state or a solid state above (left side) the saturation vapor pressure curve S. From this figure, it can be seen that the substance indicated by the saturated vapor pressure curve S is in a liquid state or a solid state at the point A, that is, at normal temperature (for example, 25 ° C.) and normal pressure (for example, 1 × 10 ⁵ Pa). I understand.
[0005]
Here, it is considered that the substance in the state of the point X is evacuated by the vacuum pump 100. The temperature near the suction port of the first-stage vacuum pump unit 110 in FIG. 3 is at room temperature, and the gas in the state at the point X in FIG. 2 contacts the wall of the suction port and is cooled to the state at the point B to be liquefied or Start to solidify. The temperature of the gas with the compressed passes through the vacuum pump unit 112, 114, 116 proceeds the flow path L ₁ is increased, but the vacuum pump unit 112, 114, 116 including the flow path L ₁ is made of cast iron Their temperature rises because heat is not easily dissipated. The high-temperature gas is cooled by the cooler 134 on the downstream side of the fourth-stage vacuum pump unit 116. Since the cooling water at room temperature flows through the cooler 134, the gas in contact with the cooling surface is in the state of point E in FIG. 2 and is cooled or solidified and adheres to the cooling surface of the cooler 134.
[0006]
The gas that has not been liquefied or solidified is further compressed by the vacuum pump unit 118 to a high temperature and cooled by the cooler 136. Since the cooling water at room temperature is also flowing through the cooler 136, the gas in contact with the cooling surface is in a state of a point F in FIG. 2 and is liquefied or solidified and adheres to the cooling surface of the cooler 136. Then, the gas exhausted from the vacuum pump unit 120 is in the state of point D in FIG. 2 (temperature: 100 ° C., pressure: 1 × 10 ⁵ Pa) and is discharged into the normal pressure atmosphere.
[0007]
In this way, the gas reaches the temperature at the point B (normal temperature) near the inlet of the vacuum pump unit 110 and the temperature at the point D (100 ° C.) near the outlet of the vacuum pump unit 120. Since it is cooled at 134 and 136, the vacuum pump 100 can be regarded as forming a temperature gradient as shown by the line segment BD in FIG. The performance of the vacuum pump 100 is degraded by liquefaction or solidification on the wall surface of the suction port of the first-stage vacuum pump unit 110 and the cooling surfaces of the coolers 134 and 136. It is expected to reach.
[0008]
In order to solve such a problem, a vacuum pump as disclosed in Japanese Patent Application Laid-Open No. 1-182852 has been proposed. Figure 4 is a block diagram of the vacuum pump 200, and vacuum pump unit 210,212,214,216,218,220 six stages are connected in series by the flow path L _2, and are each an inert gas For example, partial pressure adjusting mechanisms 222, 224, 226, 228, 230, and 232 for blowing a nitrogen gas to lower the partial pressure of the gas below the saturated vapor pressure curve S in FIG. 2 are provided. Further, the flow path l ₂ of the cooling water of the coolers 234, 236, 238 provided in the part between the vacuum pump units 216 and 218 in the flow path L ₂ , the part between 218 and 220, and the part downstream of 220. In contrast, a cooling water temperature adjustment mechanism 240 for adjusting the temperature of the cooling water is provided, and the temperature of the cooling water is set to a temperature at which gas does not liquefy or solidify on the cooling surfaces of the coolers 234, 236, and 238, that is, In FIG. 2, the heating is adjusted so as to be a temperature at which the gas phase state on the lower side (right side) of the saturated vapor pressure curve S is maintained.
[0009]
[Problems to be solved by the invention]
The addition of the partial pressure adjusting mechanisms 222, 224, 226, 228, 230, 232 and the cooling water temperature adjusting mechanism 240 not only increases the manufacturing cost of the vacuum pump 200 and increases the installation space, but also increases the inert gas. Blowing increases the running cost, and when the cooling water temperature adjustment mechanism 240 causes an adjustment trouble, the cooling water may boil to destroy the equipment.
[0010]
The present invention has been made in view of the above-described problems, and is intended to exhaust a gas that is liquefied or solidified at a normal temperature, a normal pressure or a state close to the normal temperature generated in a semiconductor manufacturing process such as low-pressure CVD or dry etching without liquefying or solidifying. It is an object to provide a vacuum pump which can be used.
[0011]
[Means for solving the problem]
Above purpose, room temperature, a normal pressure or a multistage vacuum pump for exhausting the gas to be liquefied or solidified in a state close to it, the main components including a casing which constitutes the flow path of the gas in the aluminum or aluminum alloy are manufactured, the main component transmits a part of the heat generated in the exhaust side during the operation to the intake side, the major part of the intake side, Oite the gas to the operating pressure of the intake side liquefied or This is achieved by a vacuum pump characterized by being configured to be at or above the temperature at which it solidifies .
[0012]
[Action]
Since the main parts constituting the gas flow path in the vacuum pump are made of aluminum or aluminum alloy having high thermal conductivity, the heat of gas compression is immediately transmitted to all of the main parts of the vacuum pump, and from the main parts. Dissipated outside. Therefore, the temperature of the gas does not rise even in the vicinity of the exhaust port of the vacuum pump where the gas is compressed most and the temperature becomes highest , and the pressure in the vicinity of the intake port is generated by the transmitted and transmitted heat of compression near the intake port of the vacuum pump. Since the temperature is raised to a temperature at which the gas does not liquefy or solidify, the gas is not liquefied or solidified. Thus, the gas is exhausted without liquefaction or solidification.
[0013]
【Example】
Hereinafter, a vacuum pump according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a main part of a vacuum pump 10 according to an embodiment. That is, the vacuum pump 10 while leading to the outlet 5 from the inlet port 2 and have contact within the cylindrical casing 1, a cylinder 3 _1, 3 _{2, 3} 3, 3 _4, 3 _5, 3 _6, contact connecting these passage 4 _1, 4 _2, 4 _{3, 4} 4, 4 ₅ are provided. An intake side cover 6 is attached to an intake side end surface of the casing 1, and an exhaust side cover 7 is attached to an exhaust side end surface. The casing 1 is not provided with a cooler or a cooling water passage .
[0014]
Each of the cylinders 3 ₁ , 3 ₂ , 3 ₃ , 3 ₄ , 3 ₅ , 3 ₆ has an impeller 8 ₁ , 8 ₂ , 8 ₃ , 8 ₄ fixed to a rotating shaft 9 passing through the axis of the casing 1. , 8 ₅ , and 8 ₆ are combined, and are compressed and exhausted in six stages. One end of the rotating shaft 9 is supported by a bearing 12 fixed to the intake-side cover 6, and a lip seal 13 seals a gas flow path and the atmosphere inside the bearing 12. The other end of the rotating shaft 9 is supported by a bearing 14 similarly fixed to the exhaust side cover 7, and a gas flow path and the atmosphere are sealed by a lip seal 15 on the inner side. Each impeller 8 _1, 8 _2,..., 8 ₆ constitutes the rotor 11 together with the rotating shaft 9, the rotation shaft 9 outside the exhaust side cover 7, via a gear 16 attached to the rotary shaft 9, shown Not driven by a motor. Then, the intake side cover 6, the exhaust-side cover 7, the cylinder 3 _1, 3 _2, ..., 3 ₆ integral with the casing 1, and the main component in contact with a gas such as the rotor 11 is about four times in comparison with cast iron It is made of an aluminum alloy having the above thermal conductivity.
[0015]
The vacuum pump 10 according to the embodiment of the present invention is configured as described above. Next, its operation will be described. In FIG. 2, the gas at the point X is sucked from the suction port 2 at normal temperature of the vacuum pump 10 as shown by an arrow, and a part of the gas contacts the wall of the suction port 2 and is cooled to the state at the point B to liquefy. or is solidified, most compresses the intensified heating according passing through the cylinders 3 _1, 3 _2, 3 _3, 3 _4, 3 _5, 3 _6, most temperature increase in the vicinity of the exhaust port 5 .
[0016]
At this time, since the aluminum alloy has a high thermal conductivity, the compression heat is immediately transmitted to the casing 1 and the rotor 11 and is radiated to the outside from the casing 1 and the exhaust-side cover 7, and the casing 1 and the rotor 11 have a high temperature. It is transmitted from the exhaust port side to a lower inlet side temperature, a temperature adjacent to the casing 1 of the intake port 2 to raise the temperature of the temperature and the impeller 8 ₁ on the intake side cover 6. Accordingly, the gas at the exhaust port 5 is in the state of point D in FIG. 2 (temperature: 100 ° C., pressure: 1 × 10 ⁵ Pa) and is discharged as indicated by the arrow. In addition, the gas at the intake port 2 comes to take the state of the point C in FIG. 2, and the liquefied or solidified substance that first comes into contact with the wall of the intake port 2 is vaporized again.
[0017]
In this way, the gas reaches the temperature at the point C near the intake port 2 and the temperature at the point D (100 ° C.) near the exhaust port 5, so that the vacuum pump 10 of the embodiment is shown by the line segment CD in FIG. It can be considered that a gentle temperature gradient is formed. The points C and D are both sufficiently away from the saturated vapor pressure curve S downward (to the right), and the gas is exhausted by the vacuum pump 10 without being liquefied or solidified. Also, the casing 1 or the cylinder 3 _1, 3 ₂ since the gas is sufficiently cooled in the meantime, ..., there is no need to cool the 3 _6, and the like.
[0018]
Although the embodiments of the present invention have been described above, the present invention is, of course, not limited thereto, and various modifications can be made based on the technical idea of the present invention.
[0019]
For example, in the present embodiment, the vacuum pump 10 for evacuating by compressing to six stages has been described, but the present invention can also be applied to a multi- stage vacuum pump having less than six stages or seven or more stages.
[0020]
Further, in this embodiment, the vacuum pump having the cylindrical casing 1 is used. However, fins for heat radiation may be provided on the outer surface of the cylinder.
[0021]
Further, in the present embodiment, the main parts constituting the gas flow path of the vacuum pump are made of aluminum alloy, but those made of aluminum having the same thermal conductivity may be used. .
[0022]
Although not provided in this embodiment, the cylinders 3 _1, 3 _2, ..., 3 ₆
There is no problem in providing a mechanism for blowing an inert gas for lowering the partial pressure of the gas into the inside.
[0023]
【The invention's effect】
As described above, in the vacuum pump of the present invention, since the main parts including the casing constituting the gas flow path are made of aluminum or aluminum alloy having a high thermal conductivity , the heat on the exhaust side, which becomes high in temperature, is taken into the intake air. Easily transmitted to the side to increase the temperature on the intake side . Further, since the gas flow path composed of the main parts including the casing does not have a cooler for removing the heat of compression of the gas, heat transfer from the exhaust side to the intake side is not hindered . Therefore , a gas having a property of liquefying or solidifying at normal temperature, normal pressure or in a state close to it, such as aluminum chloride, ammonium chloride, or steam that is not overheated but is close to a saturated vapor pressure curve is exhausted. In this case, since the gaseous phase is maintained from the intake port to the exhaust port, the performance of the vacuum pump is not deteriorated or clogged due to liquefaction or solidification of gas. Also, at the beginning of the operation, even if there is gas that once liquefies or solidifies at the intake port, these are vaporized over time.
[0024]
Furthermore, with compression heat of the gas is dissipated to the outside is transmitted immediately to the main components constituting the flow path of the vacuum pump, heat who are exhausted by Rukoto are sufficiently from the exhaust side to be hot to the cold intake side Since the cooling is performed, a cooler for removing the heat of compression is not required in the flow path . In this respect, the manufacturing cost of the vacuum pump is reduced, and the installation space is given a margin.
[Brief description of the drawings]
FIG. 1 is a sectional view of a main part of a vacuum pump according to an embodiment.
FIG. 2 is a diagram showing a saturated vapor pressure curve of a substance to be exhausted.
FIG. 3 is a block diagram of a vacuum pump according to a first conventional example.
FIG. 4 is a block diagram of a vacuum pump according to a second conventional example.
[Explanation of symbols]
1 Casing 2 Inlet 3 ₁ Cylinder 3 ₂ Cylinder 3 ₃ Cylinder 3 ₄ Cylinder 3 ₅ Cylinder 3 ₆ Cylinder 4 ₁ Communication channel 4 ₂ Communication channel 4 ₃ Communication channel 4 ₄ Communication channel 4 ₅ Communication channel 5 Exhaust Mouth 6 Intake side cover 7 Exhaust side cover 8 ₁ impeller 8 ₂ impeller 8 ₃ impeller 8 ₄ impeller 8 ₅ impeller 8 ₆ impeller 9 Rotating shaft 10 Vacuum pump 11 of embodiment

Claims (3)

Normal temperature, a normal pressure or a multistage vacuum pump for exhausting the gas to be liquefied or solidified in a state close to it, the main components including a casing which constitutes the flow path of the gas are made of aluminum or an aluminum alloy,
The main parts transfer a part of heat generated on the exhaust side during operation to the intake side, so that the main parts on the intake side are at or above the temperature at which the gas liquefies or solidifies at the operating pressure on the intake side. wherein the vacuum pump <br/> that are configured. The vacuum pump according to claim 1, wherein the flow path does not include a cooler for removing heat of compression of the gas. 3. The vacuum pump according to claim 1, wherein the gas is exhausted without using oil for sealing and lubrication.

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