JP4882558B2 - Turbo molecular pump - Google Patents

Description

  The present invention relates to a turbo molecular pump that exhausts a gas that is easily condensed and deposited.

  Turbomolecular pumps are used as exhaust devices for semiconductor manufacturing equipment. When a turbo molecular pump is used in a CVD film forming apparatus or an etching apparatus, depending on the type of gas to be exhausted, some of the gas tends to condense inside the pump and adhere as a product. And the adhesion of this product becomes more remarkable as the pump temperature is lower.

  When such a product accumulates on the rotor or the stator, there is a disadvantage that the balance of the rotor that rotates at a high speed is deteriorated, or the gap between the rotor and the stator is narrowed so that the rotor is easily contacted. Therefore, in order to prevent the accumulation of products on the pump body, a turbo molecular pump is known in which a heating device is provided in the pump body to keep the temperature of the pump body at a high temperature (for example, Patent Documents). 1).

  By the way, in a state where there is a gas load, the rotor temperature rises due to frictional heat with the gas and motor heat generation. On the other hand, if the temperature is excessively increased, a decrease in rotor life becomes a problem due to creep deformation. Therefore, in order to prevent product accumulation, the higher the pump temperature, the better. However, considering the effect on the creep deformation described above, it is assumed that the gas load is applied at the maximum rotational speed (rated rotational speed). The heating target temperature is set as high as possible.

Japanese Patent Laid-Open No. 8-100787

  However, when the rotor rotation is stopped or the rotation speed is lower than the rated value, there is a problem that the internal temperature of the pump tends to be low because the frictional heat and motor heat generation are small, and the product tends to accumulate. .

According to the first aspect of the present invention, there is provided a turbo molecular pump that performs vacuum exhaust by rotating a rotating body at a high speed by a motor, a heating device that heats a pump body including the rotating body, a cooling device that cools the pump body, and a pump body A temperature sensor that detects the temperature of the pump , a temperature control unit that controls the temperature of the pump body to the target temperature by controlling the heating device and the cooling device based on the temperature detected by the temperature sensor, and no load lower than the steady rotation speed When the rotation speed command is input by the input unit for inputting the rotation speed command, the determination unit for determining the presence or absence of the gas load to the pump body from the current value of the motor, the determination unit A rotation control unit for controlling the rotation speed of the motor to a rotation speed at no load when it is determined that there is no gas load;
A target temperature setting unit that sets the target temperature to a target temperature at no load that is higher than a target temperature at a steady rotational speed when the determination unit determines that there is no gas load. .
The invention according to claim 2 is the turbomolecular pump according to claim 1, wherein when the rotation control unit is controlled to the no-load rotation speed and the determination unit determines that there is a gas load, The rotation control unit controls the rotation speed of the motor to a steady rotation speed, and the target temperature setting unit sets the target temperature to the target temperature at the steady rotation speed .
According to a third aspect of the present invention, there is provided a turbo molecular pump that performs vacuum exhaust by rotating a rotating body at a high speed by a motor, a heating device that heats a pump body provided with the rotating body, a cooling device that cools the pump body, and a pump body A temperature sensor that detects the temperature of the pump, a temperature control unit that controls the temperature of the pump body to the target temperature by controlling the heating device and the cooling device based on the temperature detected by the temperature sensor, and a low-speed rotation lower than the steady-state rotation speed An input unit for inputting a speed command, a target temperature setting unit for setting a target temperature to a target temperature at a low speed higher than a target temperature at a steady rotational speed when a command for a low speed is input to the input unit ; It is provided with.
According to a fourth aspect of the present invention, in the turbomolecular pump according to any one of the first to third aspects, the target temperature setting unit sets the target temperature at a steady rotational speed when the rotating body is stopped. The target temperature during rotation stop is higher than the target temperature .

  According to the present invention, when the rotational speed of the rotating body is lower than the predetermined rotational speed, the target temperature is set to a temperature higher than the predetermined temperature, so that even when the rotational speed is low, product accumulation is prevented. can do.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. 1 and 2 are diagrams showing an embodiment of a turbo molecular pump according to the present invention, FIG. 1 is a block diagram showing a schematic configuration of the entire turbo molecular pump, and FIG. 2 is a pump body 1 of the turbo molecular pump. It is sectional drawing which shows the structure of this in detail.

  As shown in FIG. 1, the turbo molecular pump includes a pump body 1 that evacuates the vacuum chamber and a power supply device 2 that drives and controls the pump body 1. First, the configuration of the pump body 1 will be described with reference to FIG. A rotating body 4 that is rotationally driven by a motor 6 is provided inside a casing 20 provided in the pump body 1. An aluminum alloy is used as the material of the rotating body 4, and the rotor 4 has a plurality of stages of rotor blades 21 and screw groove portions 22. The rotation speed of the rotating body 4 is detected by the rotation sensor 13.

  On the other hand, a plurality of stages of stator blades 23 are alternately disposed with respect to the plurality of stages of rotor blades 21 disposed in the axial direction, and the thread groove portion 22 is tubular with a slight gap in the radial direction. A member 24 is disposed. The rotor blades 21 and the stator blades 23 are composed of turbine blades. Each stator blade 23 is maintained at a predetermined interval by a spacer 25, and the upper end of the uppermost spacer 25 is in contact with a protruding portion provided inside the upper end of the casing 20. By fixing the casing 20 to the base 28, the stator blades 23 and the spacers 25 that are alternately stacked in the axial direction are sandwiched between the upper end portion of the casing 20 and the base 28.

  When the rotating body 4 is rotated at a high speed by the motor 6, exhaust action is generated by the rotor blades 21 and the stator blades 23, and by the thread groove portions 22 and the cylindrical member 24. As a result, the gas on the intake port side is exhausted as indicated by an arrow G1, and is exhausted outside the pump by an auxiliary pump (not shown) connected to the exhaust port 26. The exhaust action by the rotor blades 21 and the stator blades 23 is effective on the high vacuum side, and the exhaust action by the screw groove 22 and the cylindrical member 24 is effective on the low vacuum side. Adhesion occurs more significantly on the low vacuum side.

  In the case of the turbo molecular pump shown in FIG. 2, a heater 29 is provided on the base 28 of the pump body, and when exhausting a gas to which products easily adhere, the heater 29 is used to raise the pump temperature. Suppresses adhesion of objects. At that time, cooling by the cooling device 30 and heating by the heater 29 are controlled to control the pump temperature. The cooling device 30 performs cooling with cooling water, and controls the cooling effect by adjusting the flow rate with an electromagnetic valve or the like. A temperature sensor 31 detects the temperature of the base 28, and the temperature detected by the temperature sensor 31 is used as the pump temperature.

  The turbo molecular pump shown in FIG. 2 is a five-axis control type magnetic bearing turbo molecular pump, and the rotating body 4 is supported in a non-contact manner by electromagnets 51 and 52 constituting a radial magnetic bearing and an electromagnet 53 constituting an axial magnetic bearing. The The floating position of the rotating body 4 is detected by radial displacement sensors 71 and 72 and an axial displacement sensor 73. 27 is an emergency mechanical bearing, and the rotating body 4 is supported by the mechanical bearing 27 when the magnetic bearing is not operating.

  In the block diagram shown in FIG. 1, regarding the pump body 1, only the components necessary for the following explanation are shown from the components shown in FIG. 2. The power supply device 2 includes a motor control unit 5, a temperature control unit 7, a temperature setting unit 8, a main control unit 9, and an operation unit 10. In addition, although the power supply device 2 is also provided with the structure regarding magnetic bearing control, illustration was abbreviate | omitted.

  By using the operation unit 10 connected to the main control unit 9, commands, parameters, and the like necessary for pump control can be input to the main control unit 9 by manual input by an operator. A command can also be input from the outside via an external input terminal (not shown) provided in the power supply device 2. The motor control unit 5 is drive-controlled based on a signal from the rotation sensor 13 so as to have a predetermined rotation speed. The predetermined rotational speed includes a rated rotational speed ω0 described later, a user-set maximum rotational speed ω1, ω2, an idling rotational speed ω3, and the like.

  The target temperature setting unit 8 inputs the target temperature for the pump temperature control to the temperature control unit 7 based on the rotation speed information from the rotation sensor 13, the rotation speed setting value and the target temperature setting value from the main control unit 9. To do. Based on the pump temperature information from the temperature sensor 31, the target temperature input from the target temperature setting unit 8, and the temperature control mode from the main control unit 9, the temperature control unit 7 uses the heating and cooling device 30 with the heater 29. Control cooling.

<< Explanation of pump temperature control >>
The turbo molecular pump of the present embodiment has two control modes for controlling the pump temperature. The first temperature control mode is a temperature control mode that is applied when exhausting a gas that may be attached or deposited. The second temperature control mode is a temperature control mode that is applied in a state in which no gas load is applied in a situation where the gas is exhausted due to adhesion or deposition. Note that when exhausting gas with little concern about adhesion or deposition, the temperature control mode may be turned off. The temperature control mode is switched or turned on / off by the main control unit 9 based on an input command.

(First temperature control mode)
First, the first temperature control mode will be described. In the first temperature control mode, as shown in FIG. 3, the target temperature is set according to the rotational speed (rpm) of the pump. FIG. 3 is a diagram for explaining the relationship T (ω) between the target temperature and the rotational speed, where the vertical axis represents the target temperature and the horizontal axis represents the rotational speed. ω0 is a rated rotational speed, and is controlled to the rated rotational speed ω0 in a normal setting. For example, when the gas load is large, the electric power supplied to the motor 6 is increased so that the rotation speed does not decrease, and the rotation speed is controlled to be maintained at ω0.

  T0 is the target temperature when controlled at the rated rotational speed ω0, and T4 is the target temperature when the rotational speed ω is ω = 0. The user can set the target temperature T0 according to the type of gas to be exhausted. The target temperature can be set by the operation unit 10, and the target temperature T 0 input to the main control unit 9 is input from the main control unit 9 to the target temperature setting unit 8. The target temperature setting unit 8 sets a temperature curve T (ω) based on the target temperature T0, and sets T4 = T (0) from the set temperature curve T (ω). Note that the user may directly set the target temperature T4, and in this case, the user set T4 is not T4 = T (0) determined from the temperature curve T (ω). Use with priority.

  The temperature curve T (ω) is set in consideration of the creep deformation of the rotor at the rotational speed ω. That is, the creep deformation depends on the rotor temperature and the centrifugal force applied to the rotor, and the creep deformation decreases as the rotational speed ω decreases. Therefore, the target temperature T can be increased by reducing the rotational speed ω. Basically, the temperature curve T (ω) can be said to represent the relationship between the rotational speed ω and the target temperature when the allowable creep deformation is set to a predetermined amount. The temperature rises.

  The rated rotational speed ω0 defines the maximum rotational speed, and is generally used in this setting, and the target temperature setting unit 8 outputs the target temperature T0. However, the maximum rotation speed can be set by the user within a predetermined range according to the use conditions. Ω1 and ω2 in FIG. 3 represent the upper limit value and the lower limit value. ω1 and ω2 can be input and set using the operation unit 10. In the first temperature control mode, when the maximum rotation speed is set to ω1, for example, the target temperature is set to T1 = T (ω1) lower than T0. Similarly, when the maximum rotation speed is set to ω2, the target temperature is set to T2 = T (ω2).

  In addition, even when an operation state in which the rotation speed is lower than the maximum rotation speed is entered, the temperature is controlled based on the target temperature T (ω) corresponding to the rotation speed ω at that time. Further, even when the pump rotation is stopped (ω = 0), when the set state is the first temperature control mode, the target temperature is set to T4 = T (0).

  When a turbo molecular pump is used in a process in which the product is significantly deposited, a certain amount of product deposition may be unavoidable even if the target temperature at the time of gas load is maintained at T0. In such a case, if the internal temperature of the pump is not sufficiently high, the accumulated product has a high viscosity and a high hardness, and there is a possibility that the rotation cannot be started from the pump stopped state. Therefore, in the first temperature control mode, heating can be performed even in the rotation stop state, and the occurrence of such inconvenience can be prevented by setting the target temperature to a higher temperature T4.

(Second temperature control mode)
The second temperature control mode is basically set by an input operation by the operation unit 10 or an external command when the first temperature control mode is set. For example, when the rated rotational speed ω0 is set as the maximum rotational speed, the motor control unit 5 is controlled so that the rotational speed is always ω0. When the second temperature control mode is set by a user operation or an external signal when no gas load is applied, the rotational speed is lowered to a predetermined value ω3 and the target temperature is higher than before the rotational speed is lowered. Set the value T3 = T (ω).

  This can be said to be a control mode in a so-called idling state that does not require exhaust by a turbo molecular pump. By reducing the rotational speed and increasing the target temperature sufficiently, the effect of preventing product accumulation by raising the pump internal temperature was further improved. Further, when there is no heat generated by the gas load, the internal temperature of the pump tends to be lower, and thus such a temperature drop can be avoided by switching from the first temperature control mode to the second temperature control mode. When the second temperature control mode is canceled, the first temperature control mode before the setting is restored.

  Here, the case where the switching to the second temperature control mode is performed by an input operation by the operation unit 10 or an external command has been described, but the switching may be performed by the following operation. For example, a mode in which a switching operation is performed by an input operation of the operation unit 10 is entered. If this mode is entered, the main controller 9 determines whether or not a gas load is applied from the magnitude of the motor drive current.

  When the gas load is applied, the current value becomes larger than when there is no gas load, and therefore the presence or absence of the gas load can be determined from the motor current value. And if it judges that the gas load is not applied, it will switch to 2nd temperature control mode. If it is determined that a gas load has been applied after switching to the second temperature control mode, the mode is switched to the first temperature control mode. That is, in the mode for performing the switching operation, switching between the first and second temperature control modes is automatically performed.

The embodiment described above has the following effects.
(1) The target temperature is set to a predetermined temperature T0 when the rotational speed of the rotating body 4 of the turbo molecular pump is a predetermined rotational speed ω0, and the target temperature is set to the predetermined temperature T0 when the rotational speed of the rotating body 4 is lower than the predetermined rotational speed ω0. Since the setting means (target temperature setting unit 8) for setting a higher temperature is provided, it is possible to prevent the product from being deposited even when the rotational speed is low.
(2) Since the pump temperature is controlled to the target temperature set by the setting means 8 even when the rotation of the rotating body 4 is stopped, the rotating body 4 is fixed to the deposit and cannot be rotated. Can be prevented.
(3) a first operation mode (first temperature control mode) in which the rotating body 4 of the turbo molecular pump is rotated at the first rotational speed ω0 and the pump temperature is controlled to the first target temperature T0; A second operation mode (second operation mode) in which the rotating body 4 is rotated at a second rotational speed ω3 that is smaller than the first rotational speed ω0 by a predetermined amount and the pump temperature is controlled at a second target temperature T3 that is higher than the first target temperature T0 by a predetermined temperature. Switching means (main control unit 9) for switching between the two temperature control modes), for example, by performing such an operation in a state where no gas load is applied, the influence of creep deformation on the rotating body 4 is suppressed. In addition, it is possible to suppress gas condensation and adhesion. Further, the switching of the operation mode may be performed automatically according to the gas load of the turbo molecular pump.

In the correspondence between the embodiment described above and the elements of the claims, the heater 29 constitutes a heating device . The above description is merely an example, and when interpreting the invention, there is no limitation or restriction on the correspondence between the items described in the above embodiment and the items described in the claims. In addition, the present invention is not limited to the above embodiment, and can be applied to, for example, a drag pump that exhausts a gas in which a product is easily deposited.

1 is a block diagram showing an embodiment of a turbo molecular pump according to the present invention. It is sectional drawing which shows the structure of the pump main body 1 of a turbo-molecular pump in detail. It is a figure explaining the relationship T ((omega)) of target temperature and rotational speed.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1: Pump main body, 2: Power supply device, 4: Rotating body, 5: Motor control part, 7: Temperature control part, 8: Target temperature setting part, 9: Main control part, 10: Operation part, 13: Rotation sensor, 29: Heater, 30: Cooling device, 31: Temperature sensor

Claims (4)

In a turbo molecular pump that rotates a rotating body at high speed by a motor and performs vacuum exhaust,
A heating device for heating a pump body including the rotating body ;
A cooling device for cooling the pump body;
A temperature sensor for detecting the temperature of the pump body;
And it controls the heating device and the cooling device based on the detected temperature of the temperature sensor, a temperature control unit for controlling the temperature of the pump body to a target temperature,
An input unit for inputting a no-load rotation speed command lower than the steady rotation speed;
A determination unit for determining the presence or absence of a gas load on the pump body from the current value of the motor;
Rotation control for controlling the rotation speed of the motor to the no-load rotation speed when the determination section determines that there is no gas load when the no-load rotation speed command is input by the input section And
A target temperature setting unit that sets the target temperature to a target temperature at no load that is higher than a target temperature at a steady rotational speed when the determination unit determines that there is no gas load. Turbo molecular pump. The turbo-molecular pump according to claim 1 ,
When it is determined by the determination unit that there is a gas load when being controlled by the rotation control unit to the no-load rotation speed,
The rotation control unit controls the rotation speed of the motor to the steady rotation speed,
The turbo-molecular pump, wherein the target temperature setting unit sets the target temperature to a target temperature at the steady rotation speed . In a turbo molecular pump that rotates a rotating body at high speed by a motor and performs vacuum exhaust,
A heating device for heating a pump body including the rotating body ;
A cooling device for cooling the pump body;
A temperature sensor for detecting the temperature of the pump body;
A temperature control unit for controlling the heating device and the cooling device based on the temperature detected by the temperature sensor to control the temperature of the pump body to a target temperature;
An input unit for inputting a command for a low speed lower than the steady speed;
A target temperature setting unit that sets the target temperature to a low-speed target temperature that is higher than the target temperature at the steady-state rotational speed when a command for the low-speed rotation speed is input to the input unit ; Turbo molecular pump. The turbomolecular pump according to any one of claims 1 to 3 ,
The target temperature setting unit sets the target temperature to a target temperature at the time of rotation stop higher than the target temperature at the steady rotation speed when the rotating body is stopped from rotating. .

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