JP3167102B2 - Turbo molecular pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbo-molecular pump which generates heat during an exhaust operation. The present invention relates to a turbo-molecular pump capable of preventing a reaction product due to a process gas from attaching to a region where the pressure increases.

[0002]

2. Description of the Related Art FIG. 5 shows a conventional turbo-molecular pump, in which a cylindrical casing 1, a base 2 for supporting the casing 1, and a motor provided in the casing 1 and fixed to the base 2 are provided. A housing 3, a shaft 6 supported via bearings 4, 5 as bearings mounted in the motor housing 3, and the motor housing 3 housed in an inner periphery 7 a fixed to the shaft 6 so as to be integrally rotatable. A rotor 7, a turbine 8 serving as a pump mechanism formed between an outer periphery 7 b of the rotor 7 and an inner periphery 1 a of the casing 1, and an oil tank 9 attached to the bottom of the base 2. Become. And intake port 1
The gas sucked in from 0 is compressed by the turbine 8 and the exhaust port 1
1 can be forcibly exhausted.

[0003]

However, in the conventional turbo-molecular pump as described above, when exhausting the process gas, the reaction products cannot be prevented from adhering and accumulating in the pump, resulting in severe clearance. Such a reaction product adheres to and accumulates on the rotor designed and incorporated in the system, causing many inconveniences such as solid contact, breakage, and failure, as well as maintenance and operating efficiency reduction accompanying the repair. Similarly, adhesion and deposition of reaction products on the outer surface of the motor housing often have inconveniences such as maintenance.

More specifically, in the turbo molecular pump, a cooling fitting 12 in which a water cooling pipe 12a is embedded by solder or the like for cooling the bearings 4 and 5 is disposed in close contact with the base 2 and the oil tank 9. . As a result, the base 2 is directly cooled to cool the lower bearing 5, and the oil in the oil tank 9 is cooled. The oil is sucked up by the nozzle 6 a and supplied to the lower bearing 5 and the upper bearing 4 along the shaft 6. To cool down.

[0005] However, as shown in the figure, the base 2 is brought into metallic contact with the spacer 1b forming the inner periphery 1a of the casing 1 and the motor housing 3, and these are usually made of an aluminum alloy having good thermal conductivity. Because
Most of the cold heat transmitted to the base 2 is also transmitted to these portions, and thereafter, is also transmitted to the rotor lower end 7a to the rotor outer periphery 7b by radiation, that is, it is easy to store cold in the hitting point illustrated area A. Often kept at relatively low temperatures. However, when this pump is applied to a semiconductor manufacturing apparatus for performing, for example, aluminum dry etching of a semiconductor device, a small amount of chlorine-based process gas (CC
l ₄ , BCl ₃ , Cl _2, etc.) in the processing chamber while carrying out the process, so that a reaction product (aluminum chloride: AlCl ₃₎ generated when aluminum is etched.
) Flows into the pump together with unreacted process gas. As shown in the vapor pressure curve of FIG. 6, such AlCl ₃ or the like has a property that it becomes a gas phase at a certain temperature or higher depending on the pressure and becomes a solid phase at a temperature lower than that temperature. since it is often drops below solidus temperature such as AlCl ₃ in this AlCl ₃ or the like is cooled while passing through the area a, will adhere to the area a becomes solid as shown in FIG. 5 . At a practical level, it is not uncommon for the deposit to reach 3 to 4 mm within a certain period of use.

[0006] Therefore, the turbo molecular pump requires
If it is used to exhaust Cl ₃ or a process gas that causes similar phenomena, more frequent disassembly / cleaning work is required as compared with the normal case, and a great inconvenience is imposed on maintenance and operation efficiency. . In addition, especially between the outer circumference 7b of the rotor and the inner circumference 1a of the casing, since they are severely maintained at a very small interval of about 1 mm, they are liable to come into solid contact with the deposited reaction product, and damage or breakage of the pump itself is prevented. I will invite you.

[0007] Such a disadvantage is not limited to the one employing a bearing. Even if a magnetic bearing is employed, for example, the heat generation factor is small and the temperature in the region A is fixed to the reaction product during pump operation. This is a common problem for those below the phase temperature. Also, in turbo molecular pumps that use magnetic bearings, if heat generation factors such as frictional heat between the gas and the blades and motor heat generation due to an increase in the gas load are large, the same applies to the ball bearing method from the viewpoint of bearing protection. A cooling means is provided, which causes a problem of adhesion of reaction products.

The present invention has been made in view of the above problems, and effectively prevents the reaction products from adhering to the position of the region A and prevents the bearing from being heated. Therefore, the object of the present invention is to improve the reliability, durability, maintainability, and the like of the turbo-molecular pump.

[0009]

Means for Solving the Problems To solve the above problems, a turbo molecular pump according to the present invention, which has a general configuration, includes a region A, that is, an inner periphery and an outer periphery including a lower end of a rotor. A sensor for measuring the temperature of the area over the facing surface, a cooling means for cooling the bearing, and based on a detection value from the sensor, the temperature is equal to or higher than the solidification temperature of the substance in the exhaust gas and the bearing is protected. Control means for controlling the cooling means so as to be maintained at a temperature.

According to such a configuration, the bearing can be protected from burning or the like by cooling the bearing by the cooling means, and the region A is cooled to a solid phase temperature or lower by the conduction of cold heat from the cooling means. Thus, the reaction product can be prevented from adhering to the region A.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. Parts common to those in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 1 shows an embodiment of a turbo-molecular pump according to the present invention. This is achieved by removing the cooling fitting 12 and the water cooling pipe 12a attached to the base 2 in the configuration of FIG. 5, and instead replacing the heating means 21 attached to the base with the cooling means embedded in the oil tank 9. 22, a temperature sensor 23 for measuring the temperature of the area A, and control means 24 for setting the area A to a predetermined temperature based on a signal from the temperature sensor 23.

The heating means 21 is a heater (for example, a sheath heater) which is in close contact with the bottom of the base 2 while avoiding direct contact with the oil tank 9. When the heater 21 generates heat, the base 2 is first heated and transmitted to the motor housing 3 having good thermal conductivity and the spacer 1b which are in metal contact with the base 2, and further radiated to the rotor 7 by the radiation.
The heat is transferred to the inner circumference 7a and the outer circumference 7b including the lower end 7c of the first area A, and as a result, the entire area A is heated substantially uniformly.

The cooling means 22 includes a cooling plate 22a closely attached to the lower surface of the bottom wall of the oil tank 9, a groove 22b recessed in the cooling plate 22a, and a spiral formed by pouring solder or the like into the groove 22b and burying it. Water cooling pipe 22c,
The pipe 22d connected to the water cooling pipe 22c and the pipe 2
When cooling water of a required flow rate is introduced from the outside through an electromagnetic valve 22e interposed in 2d, the oil filled in the oil tank 9 is cooled, and when this is supplied to the upper and lower bearings 4 and 5 by forced circulation. Provides both lubrication and cooling effects.

The sensor 23 is a temperature measuring resistor inserted from the side at a position directly below the region A within the thickness of the base 2. The temperature measuring resistor 23 can convert the temperature of the area A into an electric signal and take it out.

The control means 24 controls at least one of the electromagnetic valve 22e and the heater 21 based on the detected value a of the temperature measuring resistor 23 so that the value is maintained at a preset target value b. It is configured to output signals c and d. That is, the control means 24 has a comparison output function using a microcomputer, a sequencer or the like as a constituent element.
When the detected value a input from the resistance temperature detector 23 is lower than 60 ° C., the heater 21 is activated, and when the detected value a exceeds 60 ° C., the electromagnetic valve 22e is input.
Is operated to converge the temperature of the region A to 60 ° C. The control at that time is performed by the electromagnetic valve 2
The normal ON / OFF control for 2e, the PID control for the heater 21 in addition to the ON / OFF control for eliminating the overshoot (series compensation control composed of proportional, integral, and differential compensation elements) This is also effective.

According to such a configuration, the region A is maintained at a temperature equal to or higher than the solid phase temperature of the reaction product, and the reaction product is prevented from being solidified and adhering to the region A to be reduced. . At the same time, the thermal effects of the bearings 4 and 5 are prevented by the cooling means 22 and the bearings 4 and 5 are effectively protected from burning and the like. In particular, in this embodiment, since the heater 21 and the cooling means 22 can be controlled by the control means 24, the temperature of the area A can be quickly and appropriately controlled, and the settable temperature range is wide.

In the structure of the present invention described above, the heating means (heater, hot water, etc.) may be provided at least at one position on the outer peripheral surface of the base or the casing or the outer peripheral surface of the rotor housing. Here, the heating means 31 is a sheathed heater 31 disposed along the outer periphery of the motor housing 3. When the sheath heater 31 is ignited and generates heat, first, the outer wall of the motor housing 3 is heated, and this is sequentially transmitted to the base 2 and the spacer 1b having good thermal conductivity, which are brought into metal contact, and from these parts. Further, the inner circumference 7a including the lower end 7c of the rotor 7 by radiation
In addition, the heat is transmitted to the outer periphery 7b, and as a result, the entire area A is uniformly heated.

The cooling means (cooling water, air-cooling fan, etc.) is not particularly limited as long as it can protect the bearing from thermal effects. In the embodiment shown in FIG. It is a water cooling pipe arranged along
By introducing cooling water from outside the figure, the motor housing 3 can be made to flow between the upper end and the lower end. The cold heat is transmitted to the upper bearing 4 via the bearing housing 4a, and is transmitted to the lower bearing 5 via the base 2 and the bearing housing 5a.

With such a configuration, the area A is efficiently heated by the heater 31, so that it is possible to reliably prevent the reaction products and the like from adhering to this area, and the water cooling pipe 32 By directly cooling the bearings 4 and 5, it is possible to effectively reduce not only the heat generated by itself but also the thermal influence from the heater 31. At this time, the motor housing 3
In most cases, gas purging is performed in order to prevent harmful gas in exhaust gas from entering the inside, so that there is no problem even if the motor housing 3 is cooled no matter how much.

The present invention is not limited to these embodiments. For example, the heating means 41 shown in FIG. 3 is obtained by winding a sheathed heater around the outer periphery of the casing 1 with respect to the heating means 21 shown in FIG. 1, and in this structure, the casing 1 is brought into metallic contact with the casing 1 by heating. The spacer 1b, the base 2, and the motor housing 3, which have good thermal conductivity, are sequentially heated, and furthermore, the inner circumference 7a and the outer circumference 7b including the lower end 7c of the rotor 7 can be heated by radiation. In this manner, the place where the heating means is to be disposed is not specified, and may be disposed on the base 2 facing the rotor lower end 7c as shown by the imaginary line in FIG.

The turbo molecular pump to which the present invention is applied is not necessarily limited to a bearing having a bearing, but can be applied to other turbo molecular pumps having similar problems. For example, in FIG. 4, the radial magnetic bearings 51,
52, a heater 55 is disposed on the bottom plate of the base 54 to heat the area A, and a water cooling pipe 56 is wound around the inner periphery of the heater 55 to cool the magnetic bearings 51 and 52. Thus, it is possible to prevent the reaction products from adhering to the region A and protect the thermally delicate magnetic bearings 51 and 52. Instead of the water cooling pipe 56, a water jacket 58 for cooling the bottom plate 57 may be provided in the bottom plate 57. It is more desirable that the water inlet 58 and the water outlet of the water jacket 58 be threaded so that an external cooling water pipe can be easily attached. The water cooling pipe 5 embedded in the base 2 in FIG.
Reference numeral 6 denotes an end ring-shaped one. Compared with the former, the former is easier to manufacture than the latter, the connection with an external cooling water pipe is simpler, there is less leakage, and the expansion is easier. It is excellent and can be used as appropriate for the cooling means shown in FIGS.

Further, the present invention uses hot water for the heating means, uses an air-cooling fan for the cooling means, uses other types of sensors such as thermocouples, and employs a screw rotor for the pump mechanism. Various modifications are possible without departing from the spirit. Furthermore, when the heat generated from the bearings or the like is large to some extent, it can be simply configured as shown in FIG. This drawing is common to most parts in FIG. 1, and in this turbo molecular pump, the control means 24 controls only the cooling means 22 based on the detected value a and the target value b. The control means 24 controls ON / OFF of the cooling water introduction state to the cooling means 22 so that the detected value a of the temperature in the area A is maintained at the target value b, so that the bearings 4 and 5 are controlled. , Heat from the motor M due to an increase in the gas load, etc., as a result, the temperature of the region A is appropriately maintained, and the reaction is generated. The attachment of objects can be prevented. It is needless to say that such a function and effect can be equally exerted even in the case of a magnetic bearing type turbo molecular pump having a large heat generation factor.

[0024]

As described above, the turbo molecular pump according to the present invention has a structure as described above. Therefore, it is possible to effectively prevent the reaction products from adhering to the region and protect the proper function of the bearing. The reliability, durability, maintainability, and the like of the molecular pump can be effectively improved. In particular, when the temperature in the region A is controlled to an optimum value, these more remarkable effects can be obtained.

[Brief description of the drawings]

FIG. 1 is an overall sectional view of an embodiment of the present invention.

FIG. 2 is a sectional view showing another embodiment of the present invention.

FIG. 3 is a sectional view showing another embodiment of the present invention.

FIG. 4 is a sectional view showing another embodiment of the present invention.

FIG. 5 is a cross-sectional view illustrating a configuration example of a conventional turbo-molecular pump.

FIG. 6 is a vapor pressure diagram of AlCl ₃ .

FIG. 7 is a sectional view showing another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Casing 1a ... Casing inner periphery 2 ... Base 3 ... Motor housing 4, 5 ... Bearing (bearing) 7 ... Rotor 7a ... Rotor inner periphery 7b ... Rotor outer periphery 7c ... Rotor lower end 21, 31, 41, 55 ... Heating means ( Heaters) 22, 32, 42, 58 Cooling means 51, 52 Magnetic bearing A Area

Continuation of the front page (56) References JP-A-2-70994 (JP, A) JP-A-55-91796 (JP, A) JP-A-64-19198 (JP, A) JP-A-1-148098 (JP, A) , U)

Claims (1)

(57) [Claims] 1. A casing, a base for supporting the casing, a motor housing in the casing fixed to the base, and a shaft supported via a bearing mounted in the motor housing. A turbo molecule comprising: a rotor fixed to the shaft so as to be integrally rotatable and housing the motor housing in the inner periphery; and a pump mechanism configured between the outer periphery of the rotor and the inner periphery of the casing. In the pump, a sensor for detecting a temperature in a region from an inner periphery / outer periphery including a lower end of the rotor to an opposing surface thereof, cooling means capable of cooling the bearing, and a sensor based on a detection value from the sensor. Control means for controlling the cooling means so as to be maintained at a temperature higher than the solidification temperature of the substance in the exhaust gas and at which the bearing is protected. A turbo molecular pump characterized by the above-mentioned.