JP7427437B2 - Vacuum evacuation equipment and vacuum pump used therein - Google Patents

Description

The present invention relates to a vacuum evacuation device that controls the pressure inside a chamber to be evacuated, and a vacuum pump used therein.

In manufacturing equipment for semiconductors, liquid crystals, solar cells, LEDs (Light Emitting Diodes), etc. (hereinafter referred to as "semiconductors, etc."), process gas is flowed into a vacuum chamber, which is an evacuated chamber, and the device is placed inside the vacuum chamber. A thin film is formed on the placed object to be processed, such as a wafer, or an etching process is performed.

At this time, the inside of the vacuum chamber is evacuated by changing the opening degree of the valve connected to the exhaust port of the vacuum chamber and the rotation speed of the rotor of the turbo molecular pump, which is a vacuum pump connected downstream of this valve. For example, Patent Document 1 discloses a technique for controlling the pressure in a vacuum chamber to a desired pressure.

Japanese Patent Application Publication No. 2014-148703

However, with the above-mentioned evacuation technology, when changing the opening degree of the valve, the pressure inside the vacuum chamber changes relatively largely due to the change in the opening degree, and the rotational speed of the rotor of the turbomolecular pump When changing the rotation speed, the problem is that it is difficult to accurately control the pressure in the vacuum chamber to the desired pressure because the pressure in the vacuum chamber changes relatively little in response to changes in rotational speed. was there.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a vacuum evacuation device and a vacuum pump used therein that can accurately and quickly control the pressure inside a chamber to be evacuated. .

In order to achieve the above object, a vacuum evacuation device according to a first aspect of the present invention includes:
A vacuum pump including a rotor that rotates to evacuate the inside of a chamber to be evacuated, and a casing having an intake port;
a valve disposed between the intake port of the vacuum pump and the exhaust port of the evacuated chamber;
A vacuum evacuation device comprising: a control device that controls the internal pressure of the evacuation chamber to match a target value;
When the absolute value of the difference between the target value and the pressure is larger than a predetermined value, the control device controls the rotational speed of the rotor to be constant and adjusts the opening degree of the valve , so that the absolute value of the difference is greater than a predetermined value. When the value is smaller than the predetermined value, the pressure is controlled by controlling the opening degree of the valve to be constant and adjusting the rotational speed of the rotor .

In order to achieve the above object, a vacuum evacuation device according to a second aspect of the present invention includes:
A vacuum pump including a rotor that rotates to evacuate the inside of a chamber to be evacuated, and a casing having an intake port;
a valve disposed between the intake port of the vacuum pump and the exhaust port of the evacuated chamber;
A vacuum evacuation device comprising: a control device that controls the internal pressure of the evacuation chamber to match a target value;
When the absolute value of the difference between the target value and the pressure is larger than a predetermined value , the control device adjusts the opening degree of the valve by increasing a gain of a transfer function G _V expressed by the following formula (1). However , when the absolute value of the difference is smaller than the predetermined value, the pressure is controlled by increasing the gain of the transfer function G _M expressed by the following equation (2) and adjusting the rotational speed of the rotor. It is characterized by
G _V = O _V / δ _P ... (1)
G _M =Ω _M /δ _P ...(2)
However, in the above equation (1), O _V is the Laplace transform with the initial value of the opening degree of the valve being 0, and in the above equation (2), Ω _M is the initial value of the rotation speed of the rotor. In the above equations (1) and (2), δ _P is a Laplace transform where the initial value of the difference is set to 0.

In the above vacuum evacuation device,
The control device reduces the gain of the transfer function G M when the absolute value of the difference is larger than the predetermined value, and reduces the gain of the transfer function G _V when the absolute value of the difference is smaller than _the predetermined value. It may be made smaller.

In the above vacuum evacuation device,
The vacuum pump includes a magnetic bearing that floats and supports the rotor,
When the pressure matches the target value, the rotational speed of the rotor matches the natural frequency of the displacement of the rotor, or the absolute value of the difference between the rotational speed and the natural frequency is less than a predetermined value, the opening degree of the valve may be changed and the rotational speed of the rotor may be controlled again so that the pressure matches the target value.

In the above vacuum evacuation device,
The predetermined value is changed during rotation of the rotor depending on at least one of the opening degree of the valve and the type and amount of gas introduced into the evacuated chamber and evacuated by the vacuum pump. It is also possible to do so.

In order to achieve the above object, a vacuum pump according to a third aspect of the present invention includes:
valve and
A vacuum pump used in a vacuum evacuation device, comprising a control device that controls the internal pressure of an evacuated chamber to match a target value,
comprising a rotor that rotates to exhaust the inside of the chamber to be exhausted, and a casing having an intake port for disposing the valve between the exhaust port and the exhaust port of the chamber to be exhausted,
When the absolute value of the difference between the target value and the pressure is larger than a predetermined value, the control device controls the rotational speed of the rotor to be constant and adjusts the opening degree of the valve , so that the absolute value of the difference is greater than a predetermined value. When the value is smaller than the predetermined value, the pressure is controlled by controlling the opening degree of the valve to be constant and adjusting the rotational speed of the rotor .

In order to achieve the above object, a vacuum pump according to a fourth aspect of the present invention includes:
valve and
A vacuum pump used in a vacuum evacuation device, comprising a control device that controls the internal pressure of an evacuated chamber to match a target value,
comprising a rotor that rotates to exhaust the inside of the chamber to be exhausted, and a casing having an intake port for disposing the valve between the exhaust port and the exhaust port of the chamber to be exhausted,
When the absolute value of the difference between the target value and the pressure is larger than a predetermined value , the control device increases the gain of the transfer function G _V expressed by the following formula (1) to adjust the opening degree of the valve. , when the absolute value of the difference is smaller than the predetermined value, the pressure is controlled by increasing the gain of the transfer function G _M expressed by the following equation (2) and adjusting the rotational speed of the rotor. It is characterized by
G _V = O _V / δ _P ... (1)
G _M =Ω _M /δ _P ...(2)
However, in the above equation (1), O _V is the Laplace transform with the initial value of the opening degree of the valve being 0, and in the above equation (2), Ω _M is the initial value of the rotation speed of the rotor. In the above equations (1) and (2), δ _P is a Laplace transform where the initial value of the difference is set to 0.

In the above vacuum pump,
The control device reduces the gain of the transfer function G M when the absolute value of the difference is larger than the predetermined value, and reduces the gain of the transfer function G _V when the absolute value of the difference is smaller than _the predetermined value. It may be made smaller.

In the above vacuum pump,
comprising a magnetic bearing that levitates and supports the rotor;
When the pressure matches the target value, the rotational speed of the rotor matches the natural frequency of the displacement of the rotor, or the absolute value of the difference between the rotational speed and the natural frequency is less than a predetermined value, the opening degree of the valve may be changed and the rotational speed of the rotor may be controlled again so that the pressure matches the target value.

In the above vacuum pump,
The predetermined value is changed during rotation of the rotor depending on at least one of the opening degree of the valve and the type and amount of gas introduced into the evacuated chamber and evacuated by the vacuum pump. It is also possible to do so.

According to the present invention, it is possible to provide a vacuum evacuation device and a vacuum pump used therein that can control the pressure inside a chamber to be evacuated with high precision and at high speed.

1 is a schematic configuration diagram of a vacuum device having a vacuum evacuation device according to an embodiment of the present invention. FIG. 2 is a longitudinal cross-sectional view showing the configuration of a vacuum pump included in the evacuation device according to the embodiment of the present invention. It is a graph showing the relationship between the position of the rotation axis and the position sensor detection value. It is a graph showing the relationship between the current value flowing through the electromagnet and the magnetic attraction force exerted on the rotating shaft by the electromagnet of the magnetic bearing. It is a graph showing the relationship between the rotational frequency of the rotating shaft and the natural frequency of the rotor. 1 is a schematic plan view showing the configuration of a valve included in a vacuum evacuation device according to an embodiment of the present invention. FIG. 2 is a block diagram showing a control system of a control device included in the evacuation device according to the embodiment of the present invention. (A) is a graph showing the relationship between the absolute value of the difference between the pressure target value and the pressure measurement value and the gain of the valve opening degree, and (B) is a graph showing the relationship between the absolute value of the difference between the pressure target value and the pressure measurement value. It is a graph showing the relationship between the value and the gain of the rotational speed of the rotor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A vacuum evacuation device according to an embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the vacuum evacuation device 10 is a device included in a vacuum device D used for performing thin film formation processing, etching processing, etc. in semiconductor manufacturing equipment. The evacuation device 10 evacuates the internal pressure of an evacuated chamber (vacuum chamber) 4 in which a workpiece is placed to a desired pressure.

The evacuation device 10 includes a vacuum pump 1 for discharging the process gas introduced into the chamber 4 to be evacuated, an exhaust port (not shown) of the chamber 4 to be evacuated, and an inlet port 11a of the vacuum pump 1 (FIG. 2). and a control device 3 that controls the internal pressure of the evacuated chamber 4 to match a target value.

The vacuum pump 1 is a turbo molecular pump, and as shown in FIG. 2, it includes an outer cylinder part 11, a base part 12 to which the outer cylinder part 11 is fixed, and a casing 13 constituted by the outer cylinder part 11 and the base part 12. The rotor 20 is rotatably housed within the rotor 20. The upper side of the outer cylindrical portion 11 in FIG. 2 is opened to constitute a gas intake port 11a, and a gas exhaust port 12a is formed on the side surface of the base portion 12. A flange portion 11b is formed on the intake port 11a side of the outer cylinder portion 11, and the lower end surface of the valve body 2a (FIG. 6) of the valve 2 is fixed to this flange portion 11b.

The rotor 20 includes a rotor main body 20a, a rotating shaft 30, and a washer 70. The rotating shaft 30 is rotatably supported within the casing 13 to rotate the rotor 20. A plurality of blade-shaped rotary wings 21 inclined at a predetermined angle are integrally formed on the upper outer peripheral surface of the rotor main body 20a in FIG. The rotary blades 21 are provided radially with respect to the axis of the rotating shaft 30 of the rotor 20 and are provided in multiple stages in the axial direction of the rotating shaft 30 of the rotor 20 . Fixed blades 40 are provided between the rotary blades 21 of each stage, and the rotary blades 21 and the fixed blades 40 are arranged alternately in the axial direction of the rotating shaft 30 of the rotor 20. The fixed blades 40 are also formed in a plurality of blade shapes inclined at a predetermined angle. The fixed blades 40 are disposed radially and in multiple stages between the rotary blades 21 by having their outer peripheral ends sandwiched between a plurality of ring-shaped fixed blade spacers 50 stacked in stages within the outer cylinder portion 11. .

A threaded spacer 60 is provided between the fixed wing spacer 50 disposed on the most downstream side and the base portion 12. The threaded spacer 60 is formed in a cylindrical shape, and a spiral thread groove 60a is formed on the inner peripheral surface. A cylindrical portion 22 centered on the axis of the rotating shaft 30 is formed on the lower side (downstream side where gas is transferred) of the rotor body 20a in FIG. The screw groove 60a is disposed so as to be close to and opposite to the inner circumferential surface on which the thread groove 60a is formed. A space defined by the outer peripheral surface of the cylindrical portion 22 and the thread groove 60a of the threaded spacer 60 communicates with the exhaust port 12a.

The washer 70 is formed into a disk shape centered on the axis of the rotating shaft 30. The rotor body 20a and the washer 70 are fixed to the rotation shaft 30 by screwing the bolt 71 onto the rotation shaft 30 with the rotor body 20a and washer 70 interposed therebetween.

In the vacuum pump 1, when the rotor 20 is rotated at high speed, the rotor blades 21 hit the molecules of the gas sucked in from the intake port 11a toward the downstream side, and the hit gas molecules are fixed to alternately arranged It collides with the blade 40 and heads downward, is further struck by the rotary blade 21 of the next stage, heads downstream, repeats this operation sequentially until it reaches the lowest stage of the rotary blade 21 and fixed blade 40, and is sent to the threaded spacer 60. The gas is sent to the exhaust port 12a while being guided by the thread groove 60a, and the gas is exhausted from the exhaust port 12a. At this time, by adjusting the rotational speed of the rotor 20, the pressure inside the gas exhaust chamber 4 can be adjusted to a desired pressure. Note that, as shown in FIG. 1, the vacuum pump 1 includes a rotation speed detector 1a for detecting the rotation speed of the rotor 20. The rotational speed detection value of the rotor 20 detected by the rotational speed detector 1 a is output to the control device 3 .

Protective bearings 31 are arranged near the upper and lower sides of the rotating shaft 30 in FIG. 2 (upstream and downstream sides through which gas flows). The protective bearing 31 prevents the vacuum pump 1 from being damaged by contacting and supporting the rotary shaft 30 when a radial magnetic bearing 33 and an axial magnetic bearing 34, which will be described later, become uncontrollable in an abnormal situation.

The rotating shaft 30 is rotationally driven by a DC brushless pump motor 32. Two radial magnetic bearings 33 support the rotating shaft 30 in the radial direction, and an axial magnetic bearing 34 supports the rotating shaft 30 in the axial direction. The two radial magnetic bearings 33 are arranged with the pump motor 32 interposed therebetween. The rotating shaft 30 is supported in a floating manner by these radial magnetic bearings 33 and axial magnetic bearings 34.

The two radial magnetic bearings 33 each have four electromagnets 33a that apply a magnetic attraction force to the rotating shaft 30. Two of them are arranged on each of the two coordinate axes with the rotation axis 30 in between. Furthermore, the two radial magnetic bearings 33 each have four inductance type or eddy current type position sensors 33b that detect the radial position of the rotating shaft 30. The four position sensors 33b are arranged two each on two mutually orthogonal coordinate axes that are perpendicular to the axis of the rotation shaft 30 and parallel to the above-mentioned coordinate axes, with the rotation shaft 30 in between.

The rotating shaft 30 is provided with a magnetic disk (hereinafter referred to as an "armature disk") 80 centered on the axis of the rotating shaft 30. The axial magnetic bearing 34 has two electromagnets 34a that apply a magnetic attraction force to the armature disk 80. The two electromagnets 34a are arranged with the armature disk 80 in between. Further, the axial magnetic bearing 34 has an inductance type or eddy current type position sensor 34b that detects the axial position of the rotating shaft 30. The inductance type or eddy current type position sensor 33b of the radial magnetic bearing 33 and the inductance type or eddy current type position sensor 34b of the axial magnetic bearing 34 have a structure similar to that of an electromagnet, and have a conductor coil. The wound core is arranged facing the rotating shaft 30.

A stator 90 is erected on the base portion 12 to protect the radial magnetic bearing 33, the axial magnetic bearing 34, the pump motor 32, etc. from the sucked gas.

The vacuum pump 1 supplies electric power to the radial magnetic bearing 33, the axial magnetic bearing 34, and the pump motor 32, and connects a pump controller (not shown) that transmits and receives signals to and from the position sensors 33b and 34b via a cable or integrally. We are prepared. The pump controller supplies a high frequency alternating voltage with a predetermined amplitude to the conductor coils of the position sensors 33b, 34b of the radial magnetic bearing 33 and the axial magnetic bearing 34. The inductance of the wire coils wound around the cores of the position sensors 33b and 34b changes depending on the distance between the core and the rotating shaft 30, and the amplitude of the voltage applied to the wire coils changes depending on the change in inductance. changes, and the pump controller detects the position of the rotating shaft 30 by detecting the changed amplitude value. As shown in FIG. 3, this amplitude value (position sensor detection value E _O ) has nonlinearity that increases or decreases in a curved manner with respect to changes in the position of the rotating shaft 30. The pump controller is configured such that the sum E _O1 +E _O2 (difference depending on how the positive and negative signs are determined) of the amplitude values of the two position sensors 33b facing each other across the rotation axis 30 on each of the aforementioned coordinate axes is the sum of the amplitude values of the rotation axis 30. Since it has pseudo-linearity with respect to changes in position, by calculating this sum (difference) and using that value as the detection signal of the position sensor 33b, it is possible to apply linear control theory, and the corresponding The position of the rotating shaft 30 is controlled based on theory. The pump controller aligns the position of the rotating shaft 30 with the target position through feedback control that adjusts the current value flowing through the electromagnet 33a based on the sum (difference) of the detection signals of the two position sensors 33b on each coordinate axis. There is.

The magnetic attraction force f that each electromagnet 33a of the radial magnetic bearing 33 acts on the rotating shaft 30 also exhibits nonlinearity that increases or decreases in a curved manner with respect to changes in the current flowing through the electromagnet 33a, as shown in FIG. have. Therefore, when adjusting the current value, for the two electromagnets 33a facing each other across the rotation axis 30 on each coordinate axis, the rotation axis 30 deviates from the target position, and the electromagnet 33a whose distance from the rotation axis 30 is larger is adjusted. , a current having a current value (I ₀ +i ₁ ) obtained by adding a current value i ₁ to a predetermined DC current value (hereinafter referred to as "bias current value") I ₀ is passed, and the This is done by passing a current having a current value (I _{0 −i 1} ), which is obtained by subtracting the current value i ₁ from the bias current value I 0 , through the electromagnet 33a. In this way, by setting the sum f _hx1 + (-f _hx2 ) of the magnetic attraction forces exerted by the two electromagnets 33a as the magnetic attraction force acting on the rotating shaft 30, the magnetic attraction force can be adjusted against changes in the current value. It is made to have pseudo-linearity, making it possible to apply the above-mentioned linear control theory.

The configuration of the axial magnetic bearing 34 is basically the same as that of the radial magnetic bearing 33, but in order to reduce the required space, an armature disk 80 is sandwiched in the axial direction of the rotating shaft 30. Alternatively, instead of arranging two position sensors, only one position sensor 34b is arranged and the other position sensor is replaced by a coil having a predetermined inductance arranged on a circuit board inside the controller. good. In this case, the inductance of the coil provided on the circuit board is a predetermined value, and the amplitude value of the alternating voltage is a predetermined value, so the change in the position of the rotating shaft 30 due to the sum (difference) of the two position sensors Although the accuracy of linearization for the linearization decreases, it is useful if the vacuum pump 1 can be operated normally.

Incidentally, the rotor 20 is suspended and supported in the air by these radial magnetic bearings 33 and axial magnetic bearings 34, but the supporting force is a force component proportional to a change in the position of the rotor 20, that is, an elastic force. Since the rotor 20 has a component corresponding to , the rotor 20 has a natural frequency corresponding to its mass or moment of inertia. The rotor 20 floating in the air has three degrees of freedom in each axial direction of a three-dimensional orthogonal coordinate system in which one coordinate axis (hereinafter referred to as the "z-axis") coincides with the axis of the rotating shaft 30, and three degrees of freedom around each axis. It has a total of 6 degrees of freedom, including 3 degrees of freedom, of which 5 degrees of freedom, excluding 1 degree of freedom around the z-axis, whose rotation angle is controlled by the pump motor 32, are the radial magnetic bearing 33, the shaft Since it receives the supporting force of the directional magnetic bearing 34, it has a natural frequency corresponding to the supporting force of the radial magnetic bearing 33 and the axial magnetic bearing 34. In particular, in the two degrees of freedom around two axes (hereinafter referred to as "x-axis" and "y-axis" respectively) that are orthogonal to the z-axis and mutually orthogonal, the equation of motion of the rotor 20 is the motion around the x-axis. As shown in the following equation (3) representing the equation and the following equation (4) representing the equation of motion around the y-axis, each has a term proportional to the rotational speed around each axis (hereinafter referred to as "interference term"). . Furthermore, the magnitude of this interference term is proportional to the rotational speed of the rotating shaft 30 rotated by the pump motor 32.

However, in the above formulas (3) and (4), J is the moment of inertia of the rotor 20 around the x-axis or y-axis, _Jz is the moment of inertia of the rotor 20 around the z-axis, and C is the moment of inertia around the x-axis or y-axis. In the viscous drag coefficient, θ _x is the rotation angle of the rotor 20 about the x-axis, θ _y is the rotation angle of the rotor 20 about the y-axis, and θ _z is the rotation angle of the rotor 20 about the z-axis. In the above formula (3), D _x is a disturbance moment acting around the x-axis, and G _x is a spring constant of the moment around the x-axis generated by the supporting force of the radial magnetic bearing 33. Further, in the above equation (4), D _y is a disturbance moment acting around the y-axis, and G _y is a spring constant of the moment around the y-axis generated by the supporting force of the radial magnetic bearing 33. D _x and D _y occur due to unbalance of the rotor 20, exhaust load on the vacuum pump 1, and the like. G _x and G _y actually have frequency characteristics depending on the control design of the radial magnetic bearing 33. As described above, the rotor 20 includes the rotor main body 20a, the rotating shaft 30, and the washer 70. Therefore, the moment of inertia _Jz and the moment of inertia J are accurately defined as the rotor main body 20a, the rotating shaft 30, and the washer 70. 70 moments of inertia.

Normally, the equation for determining the natural frequency in each degree of freedom can be derived from the equation of motion for each degree of freedom. However, regarding the x-axis and y-axis of the radial magnetic bearing 33, the equations of motion are as follows: As mentioned above, it is difficult to derive a formula for determining the natural frequency due to mutual interference terms. For this purpose, in the past, a specific magnetic bearing was designed and the value of the natural frequency of that specific magnetic bearing was determined by relying on prototype experiments and computer simulations using the finite element method.

However, with these methods, even though it is possible to determine the natural frequency for each specific magnetic bearing, it is not possible to determine qualitatively the natural frequency, such as how the natural frequency changes when the design value is changed. Analysis is not possible. For this purpose, after completing the design of a specific magnetic bearing, calculate the natural frequency, and if the design is changed for various reasons, calculate the natural frequency again after completing the design changes. If there is a problem, the design must be recalculated and the design of the magnetic bearing and turbomolecular pump requires a lot of time.

In the present invention, paying attention to the fact that the radial magnetic bearing 33 of the vacuum pump 1, which is a turbo-molecular pump, is used in a vacuum, the above equations (3) and (4) are calculated by setting the viscous drag coefficient C=0. ), equations (5) and (6) expressing the natural frequencies ω ₁ and ω ₂ of the rotor 20, which exist two around the x-axis and around the y-axis, respectively, were derived. There are two natural frequencies expressed by equations (5) and (6) both around the x-axis and around the y-axis.

As shown in FIG. 5, the natural frequencies ω ₁ and ω ₂ of the rotor 20 are determined by the rotational frequency Ω _z when the rotating shaft 30 starts rotating.
As increases, the natural frequency ω ₁ decreases and the natural frequency ω ₂ increases. As the rotation frequency Ω _z increases, the natural frequency ω ₂ approaches the rotation frequency Ω _z , matches the rotation frequency Ω _z , and then moves away from the rotation frequency Ω _z .

When the natural frequencies ω ₁ and ω ₂ match or have a value close to the rotation frequency Ω _z of the rotating shaft 30, resonance of the rotor 20 is induced, and the radial magnetic bearing 33 and the axial magnetic bearing 34 It becomes difficult to float and support the rotor 20, and the rotor blades 21 continue to vibrate and undergo repeated stress fluctuations, resulting in fatigue failure. For this purpose, the control device 3 determines that when the internal pressure of the evacuated chamber 4 matches the target value, the rotational speed (rotational frequency Ω _z ) of the rotor 20 matches the natural frequencies ω ₁ and ω ₂ of the displacement. or if the absolute value of the difference between the rotational speed of the rotor 20 and the natural frequencies ω ₁ and ω ₂ is less than a predetermined value, the opening degree of the valve 2 is changed and the exhaust chamber 4 is opened again. The rotational speed of the rotor 20 is controlled so that the internal pressure matches the target value.

As shown in FIG. 6, the valve 2 includes a valve body 2a, a valve body 2c fixed to a shaft 2b, a valve motor 2d that rotates the shaft 2b and swings the valve body 2c, and a valve body 2c. It has an opening 2e that can be opened and closed. The valve 2 is provided between the exhaust port (not shown) of the evacuated chamber 4 and the intake port 11a of the vacuum pump 1, and the opening 2e of the valve 2 is provided between the exhaust port of the evacuated chamber 4 and the intake port 11a of the vacuum pump 1. It is disposed so as to communicate with and connect to the port 11a.

The opening degree of the valve 2 is adjusted by swinging the valve body 2c by the valve motor 2d, placing it at a desired position overlapping the opening 2e, and adjusting the opening area of the opening 2e. By adjusting the opening degree of the valve 2, the pressure inside the evacuated chamber 4 can be adjusted to a desired pressure. Note that, as shown in FIG. 1, the valve 2 has an opening degree detector 2f such as an encoder that detects the opening degree. The opening degree detection value of the valve 2 detected by the opening degree detector 2f is output to the control device 3.

The control device 3 controls the pressure inside the evacuated chamber 4 to match the target value by adjusting the opening degree of the valve 2 and the rotation speed of the rotor 20 of the vacuum pump 1 under predetermined conditions. The control device 3 includes a control section including a CPU (Central Processing Unit) (not shown), and a storage section including a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, and the like. The storage unit stores various data such as programs executed by the control unit, fixed data, and detected data. Further, the storage section functions as a work memory for the control section. The control unit controls the pressure within the evacuated chamber 4 by executing a program stored in the storage unit.

When changing the opening degree of the valve 2, the pressure within the evacuated chamber 4 changes relatively greatly with respect to the change in the opening degree. For example, when it is necessary to increase the pressure in the exhaust chamber 4 very slightly, even if the opening degree of the valve 2 is reduced slightly, the pressure will increase significantly, and it is necessary to reduce the pressure very slightly. In some cases, even if the opening degree of the valve 2 is increased slightly, the pressure will decrease significantly. In addition, due to backlash of the gear that transmits the rotation of the valve motor 2d to the valve body 2c, elastic slip of the belt, movement slip, etc., there may be an error in the position of the valve body 2c with respect to the rotation of the valve motor 2d. This results in the inability to accurately obtain the desired opening degree. Therefore, if you try to achieve highly accurate control by increasing the gain of the change in the opening degree of the valve 2 with respect to the change in pressure and reducing the steady-state deviation of the pressure with respect to the desired pressure, in the worst case, the gain of the change in the opening degree of the valve 2 The opening degree caused vibration phenomena, making it difficult to achieve the desired pressure accurately.

On the other hand, when changing the rotational speed of the rotor 20 of the vacuum pump 1, the pressure inside the evacuated chamber 4 changes relatively little in response to a change in the rotational speed. When it is necessary to greatly change the rotational speed of the rotor 20, the rotational speed of the rotor 20 must be changed greatly. However, when the vacuum pump 1 is a turbo-molecular pump, the rotor 20 needs to be rotated at high speed in order to achieve the desired exhaust performance, so the rotor 20 cannot be destroyed even if a large centrifugal force is applied. It is made of high-strength metal such as aluminum alloy, and has a large moment of inertia. Therefore, it is difficult to greatly change the rotational speed of the rotor 20 within a short time, that is, at high speed.

It is also possible to use a motor that can generate high torque as the pump motor 32 that rotationally drives the rotor 20 to increase the acceleration/deceleration torque, but when using a DC brushless motor that can be manufactured relatively inexpensively, When the torque constant is increased, the induced voltage constant also increases, so during high-speed rotation, the back electromotive force becomes large, and the current that generates acceleration/deceleration torque cannot flow sufficiently, and as a result, the rotation speed does not increase at high speed. It cannot be changed significantly. The inability to greatly change the rotational speed of the rotor 20 at a high speed requires time for processing the wafer surface of a semiconductor manufacturing device, for example, which has been an obstacle to increasing the amount of semiconductor manufacturing.

Therefore, in the control device 3, when the absolute value of the difference between the pressure inside the exhaust chamber 4 and the target value is larger than a predetermined value, the opening degree of the valve 2 is adjusted, and the pressure inside the exhaust chamber 4 and the target value are adjusted. When the absolute value of the difference is smaller than a predetermined value, the above problem is solved by adjusting the rotational speed of the rotor 20 of the vacuum pump 1.

Here, a method of controlling and evacuating the internal pressure of the chamber 4 to be evacuated to a desired pressure using the control device 3 will be explained. As shown in FIG. 1, the exhaust chamber 4 into which the process gas flows is provided with a pressure gauge 5, and the pressure inside the exhaust chamber 4 is measured by the pressure gauge 5. The pressure measurement value by the pressure gauge 5 is output to the control device 3, where it is compared with a pressure target value.

When the absolute value of the difference between the pressure target value and the pressure measurement value is larger than a predetermined value, the control device 3 transmits a drive signal of a value corresponding to the value of the difference to the valve motor 2d of the valve 2. Adjust the opening. At this time, the control device 3 increases the gain |G _V | of the transfer function G _V expressed by the following equation (1) in the control system shown in FIG. 7 as shown in FIG. 8(A). It's okay. At this time, conversely, in the control system shown in FIG. 7, the control device 3 changes the gain |G _M | of the transfer function G _M expressed by the following equation (2) as shown in FIG. 8(B). It may be possible to make it smaller. Further, at this time, the control device 3 may control the rotational speed of the rotor 20 detected by the rotational speed detector 1a to be kept constant.
G _V = O _V / δ _P ... (1)
G _M =Ω _M /δ _P ...(2)
However, in the above equation (1), O _V is the Laplace transform with the initial value of the opening degree of the valve 2 as 0, and in the above equation (2), Ω _M is the initial value of the rotational speed of the rotor 20. In the above equations (1) and (2), δ _P is a Laplace transform where the initial value of the difference between the pressure target value and the pressure measurement value is set to 0.

Here, increasing the gain means increasing the gain when the frequency is 0, that is, the DC gain, by 3 dB or more, and decreasing the gain means increasing the gain when the frequency is 0, that is, the DC gain. This refers to reducing the gain by 3 dB or more. Alternatively, with respect to the absolute value of the difference between the pressure target value and the pressure measurement value, the average value of the gain in a region where the absolute value is smaller than a predetermined value is made larger or smaller than the average value of the gain in a region where it is larger. Say something. Alternatively, with respect to the absolute value of the difference between the pressure target value and the pressure measurement value, the average value of the gain in a region where the absolute value is larger than a predetermined value is made larger or smaller than the average value of the gain in a region where the absolute value is smaller than the predetermined value. Say something.

On the other hand, when the absolute value of the difference between the pressure target value and the pressure measurement value is smaller than the predetermined value, the control device 3 sends a drive signal with a value corresponding to the difference value to the pump motor 32 of the vacuum pump 1. to adjust the rotational speed of the rotor 20. At this time, the control device 3 may increase the gain |G _M | of the rotational speed of the rotor 20 with respect to the absolute value of the difference between the pressure target value and the pressure measurement value. Further, at this time, conversely, the control device 3 may reduce the gain |G _V | of the opening degree of the valve 2 with respect to the absolute value of the difference between the pressure target value and the pressure measurement value. Further, at this time, the control device 3 may control the opening degree of the valve 2 detected by the opening degree detector 2f to be kept constant. These allow the pressure inside the evacuated chamber 4 to be controlled more precisely and at high speed.

Furthermore, the problem caused by the resonance of the rotor 20 of the vacuum pump 1 described above is solved, and the pressure inside the evacuated chamber 4 is evacuated and controlled by the control device 3 to a desired pressure. Explain the method. In the control device 3, the rotation speed of the rotor 20 detected by the rotation speed detector 1a and the natural frequencies ω ₁ and ω ₂ of the rotor 20 are compared, and the pressure measurement value measured by the pressure gauge 5 is determined as the pressure target value. When the rotational speed of the rotor 20 and the natural frequencies ω ₁ and ω ₂ match, or when the absolute value of the difference is less than or equal to a predetermined value, the control device 3 controls the opening degree of the valve 2. An opening degree change command signal is sent to the valve motor 2d to change the opening degree of the valve 2 by a predetermined amount. Then, a drive signal with a value corresponding to the difference between the pressure target value and the pressure measurement value measured by the pressure gauge 5 is sent to the pump motor 32 to adjust the rotational speed of the rotor 20, and the pressure measurement value is is controlled so that it matches the pressure target value.

In this embodiment, the control device 3 adjusts the opening degree of the valve 2 when the absolute value of the difference between the internal pressure of the evacuated chamber 4 and the target value is larger than a predetermined value. When the absolute value of the difference between the internal pressure of valve 4 and the target value is smaller than a predetermined value, the rotational speed of the rotor 20 of the vacuum pump 1 is adjusted, which solves the problem caused by changing the opening degree of the valve 2. , and problems caused by changing the rotational speed of the rotor 20 can be avoided, and the pressure in the evacuated chamber 4 can be brought to the desired pressure with high precision and within a short time, that is, at high speed. It becomes possible to control.

Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above embodiments and can be modified in various ways. For example, in the above embodiment, the opening degree is adjusted by swinging the valve body 2c by the valve motor 2d and placing it at a desired position overlapping the opening 2e, and adjusting the opening area of the opening 2e. Although an example using the valve 2 has been described, the valve mechanism is not limited to this, and any mechanism that opens and closes a gas flow path may be used. For example, it is also possible to use a butterfly type, flap type, etc. valve. . Further, instead of the valve motor 2d, gears, belts, etc., it is also possible to use a valve that drives the valve body 2c using pressurized air generated by a compressor or the like.

Further, in the present invention, the method of controlling the pressure in the evacuated chamber 4 is changed depending on whether the absolute value of the difference between the pressure target value and the pressure measurement value is larger or smaller than a predetermined value, and this predetermined value is For example, what type of vacuum equipment D, such as semiconductor manufacturing equipment, electron microscopes, surface analysis equipment, microfabrication equipment, etc., should the vacuum evacuation device 10 be used in, what conditions and situations should the vacuum evacuation device 10 be used in, and the vacuum pump. 1. It is determined as appropriate depending on the mechanism, type, etc. of the valve 2.
Further, this predetermined value may be changed as appropriate during rotation of the rotor 20 depending on the opening degree of the valve 2 and the type and amount of process gas introduced into the interior of the chamber 4 to be evacuated and evacuated by the vacuum pump 1. It's okay. In this case, a plurality of predetermined values may be stored in advance in the storage section of the control device 3, and the predetermined value may be changed by selecting or calculating the predetermined value as appropriate. good.

10 Vacuum exhaust device 1 Vacuum pump 1a Rotation speed detector 11a Inlet port 13 Casing 32 Pump motor 33 Radial magnetic bearing 34 Axial magnetic bearing 20 Rotor 2 Valve 2c Valve body 2d Valve motor 2e Opening 2f Opening degree detector 3 Control device 4 Evacuated chamber 5 Pressure gauge D Vacuum device

Claims (10)

A vacuum pump including a rotor that rotates to evacuate the inside of a chamber to be evacuated, and a casing having an intake port;
a valve disposed between the intake port of the vacuum pump and the exhaust port of the evacuated chamber;
A vacuum evacuation device comprising: a control device that controls the internal pressure of the evacuation chamber to match a target value;
When the absolute value of the difference between the target value and the pressure is larger than a predetermined value, the control device controls the rotational speed of the rotor to be constant and adjusts the opening degree of the valve , so that the absolute value of the difference is greater than a predetermined value. When the value is smaller than the predetermined value, the pressure is controlled by controlling the opening degree of the valve to be constant and adjusting the rotational speed of the rotor . A vacuum pump including a rotor that rotates to evacuate the inside of a chamber to be evacuated, and a casing having an intake port;
a valve disposed between the intake port of the vacuum pump and the exhaust port of the evacuated chamber;
A vacuum evacuation device comprising: a control device that controls the internal pressure of the evacuation chamber to match a target value;
When the absolute value of the difference between the target value and the pressure is larger than a predetermined value , the control device increases the gain of the transfer function G _V expressed by the following formula (1) to adjust the opening degree of the valve. , when the absolute value of the difference is smaller than the predetermined value, the pressure is controlled by increasing the gain of the transfer function G _M expressed by the following equation (2) and adjusting the rotational speed of the rotor. A vacuum exhaust device featuring :
G _V = O _V / δ _P ... (1)
G _M =Ω _M /δ _P ...(2)
However, in the above equation (1), O _V is the Laplace transform with the initial value of the opening degree of the valve being 0, and in the above equation (2), Ω _M is the initial value of the rotation speed of the rotor. In the above equations (1) and (2), δ _P is a Laplace transform where the initial value of the difference is set to 0. The control device reduces the gain of the transfer function G M when the absolute value of the difference is larger than the predetermined value, and reduces the gain of the transfer function G _V when the absolute value of the difference is smaller than _the predetermined value. The evacuation device according to claim 2 , characterized in that the evacuation device is made small. The vacuum pump includes a magnetic bearing that floats and supports the rotor,
When the pressure matches the target value, the rotational speed of the rotor matches the natural frequency of the displacement of the rotor, or the absolute value of the difference between the rotational speed and the natural frequency is below a predetermined value, the opening degree of the valve is changed and the rotational speed of the rotor is controlled so that the pressure matches the target value again. 3. The vacuum evacuation device according to any one of 3 . The predetermined value is changed during rotation of the rotor depending on at least one of the opening degree of the valve and the type and amount of gas introduced into the evacuated chamber and evacuated by the vacuum pump. The evacuation device according to claim 1 or 2 , characterized in that: valve and
A vacuum pump used in a vacuum evacuation device, comprising a control device that controls the internal pressure of an evacuated chamber to match a target value,
comprising a rotor that rotates to exhaust the inside of the chamber to be exhausted, and a casing having an intake port for disposing the valve between the exhaust port and the exhaust port of the chamber to be exhausted,
When the absolute value of the difference between the target value and the pressure is larger than a predetermined value, the control device controls the rotational speed of the rotor to be constant and adjusts the opening degree of the valve , so that the absolute value of the difference is greater than a predetermined value. When the value is smaller than the predetermined value, the pressure is controlled by controlling the opening degree of the valve to be constant and adjusting the rotational speed of the rotor . valve and
A vacuum pump used in a vacuum evacuation device, comprising a control device that controls the internal pressure of an evacuated chamber to match a target value,
comprising a rotor that rotates to exhaust the inside of the chamber to be exhausted, and a casing having an intake port for disposing the valve between the exhaust port and the exhaust port of the chamber to be exhausted,
When the absolute value of the difference between the target value and the pressure is larger than a predetermined value , the control device increases the gain of the transfer function G _V expressed by the following formula (1) to adjust the opening degree of the valve. , when the absolute value of the difference is smaller than the predetermined value, the pressure is controlled by increasing the gain of the transfer function G _M expressed by the following equation (2) and adjusting the rotational speed of the rotor. A vacuum pump featuring:
G _V = O _V / δ _P ... (1)
G _M =Ω _M /δ _P ...(2)
However, in the above equation (1), O _V is the Laplace transform with the initial value of the opening degree of the valve being 0, and in the above equation (2), Ω _M is the initial value of the rotation speed of the rotor. In the above equations (1) and (2), δ _P is a Laplace transform where the initial value of the difference is set to 0. The control device reduces the gain of the transfer function G M when the absolute value of the difference is larger than the predetermined value, and reduces the gain of the transfer function G _V when the absolute value of the difference is smaller than _the predetermined value. The vacuum pump according to claim 7 , characterized in that the vacuum pump is made small. comprising a magnetic bearing that levitates and supports the rotor;
When the pressure matches the target value, the rotational speed of the rotor matches the natural frequency of the displacement of the rotor, or the absolute value of the difference between the rotational speed and the natural frequency If is below a predetermined value, the opening degree of the valve is changed and the rotational speed of the rotor is controlled so that the pressure matches the target value again . 8. The vacuum pump according to any one of 8 . The predetermined value is changed during rotation of the rotor depending on at least one of the opening degree of the valve and the type and amount of gas introduced into the evacuated chamber and evacuated by the vacuum pump. The vacuum pump according to claim 6 or 7 , characterized in that:

Images