Vacuum exhaust device and vacuum pump used for the vacuum exhaust device

Abstract

The present invention provides a vacuum exhaust device capable of controlling the pressure in an exhaust chamber with high precision and high speed, and a vacuum pump therefor. The device comprises: a vacuum pump (1) having a rotor that exhausts the interior of an exhaust chamber (4) by rotating, and a housing having an air intake port; a valve (2) disposed between the air intake port of the vacuum pump (1) and the exhaust port of the exhaust chamber; and a control device (3) that controls the pressure inside the exhaust chamber (4) to be consistent with a target value. In the control device (3), the opening of the valve (2) is adjusted when the absolute value of the difference between the pressure inside the exhaust chamber (4) and the target value is greater than a predetermined value, and the rotation speed of the rotor of the vacuum pump (1) is adjusted when the absolute value of the difference between the pressure inside the exhaust chamber (4) and the target value is less than a predetermined value.

Description

Technical Field

[0001] The present invention relates to a vacuum exhaust device for controlling the pressure in an exhausted chamber and a vacuum pump used therefor. Background Art

[0002] In manufacturing equipment for semiconductors, liquid crystals, solar cells, LEDs (Light Emitting Diodes), etc. (hereinafter referred to as "semiconductors, etc."), process gases are flowed into a vacuum chamber, which serves as an evacuated chamber, to form thin films and perform etching processes on the workpiece, such as a wafer, placed in the vacuum chamber.

[0003] At this time, for example, Patent Document 1 discloses a technology that changes the opening of a valve connected to the exhaust port of the vacuum chamber and the rotation speed of the rotor of a turbomolecular pump connected to the downstream side of the valve, thereby evacuating the vacuum chamber and controlling the pressure in the vacuum chamber to a desired pressure.

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 2014-148703. Summary of the Invention

[0005] Problems to be solved by the invention

[0006] However, in the above-mentioned vacuum exhaust technology, when the valve opening is changed, the pressure in the vacuum chamber changes significantly relative to the change in opening. In addition, when the rotational speed of the turbomolecular pump rotor is changed, the pressure in the vacuum chamber changes only slightly relative to the change in rotational speed. Therefore, there is a problem that it is difficult to accurately control the pressure in the vacuum chamber to a desired pressure.

[0007] 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 exhaust device and a vacuum pump therefor that can control the pressure in an exhaust chamber with high precision and high speed.

[0008] Means for solving problems

[0009] In order to achieve the above-mentioned object, the vacuum exhaust device according to the first embodiment of the present invention is:

[0010] have:

[0011] The vacuum pump comprises a rotor that exhausts the interior of the exhaust chamber by rotating, and a housing having an air intake port.

[0012] The valve is arranged between the suction port of the vacuum pump and the exhaust port of the exhaust chamber.

[0013] The control device controls the pressure inside the exhaust chamber to be consistent with the target value,

[0014] The vacuum exhaust device is characterized in that:

[0015] The control device adjusts the opening of the valve when the absolute value of the difference between the target value and the pressure is greater than a predetermined value, and adjusts the rotation speed of the rotor when the absolute value of the difference is less than the predetermined value, thereby controlling the pressure.

[0016] In the above-mentioned vacuum exhaust device,

[0017] The control device may also perform control so that the rotation speed of the rotor is constant when the absolute value of the difference is greater than the predetermined value, and the opening of the valve is constant when the absolute value of the difference is less than the predetermined value.

[0018] In the above-mentioned vacuum exhaust device,

[0019] The control device may increase the transfer function G represented by the following equation (1) when the absolute value of the difference is greater than the predetermined value. V When the absolute value of the difference is less than the predetermined value, the transfer function G represented by the following formula (2) is increased. M The gain,

[0020] G V =O V / δ P ・・・(1)

[0021] G M =Ω M / δ P ・・・(2)

[0022] In the above formula (1), O V is the Laplace transform of the valve opening with an initial value of 0. In the above equation (2), Ω M is the Laplace transform of the aforementioned rotor's rotational speed with an initial value of 0. In the above equations (1) and (2), δ P is the Laplace transform of the aforementioned difference with an initial value of 0.

[0023] In the above-mentioned vacuum exhaust device,

[0024] The control device may also reduce the transfer function G when the absolute value of the difference is greater than the predetermined value. M When the absolute value of the difference is less than the predetermined value, the transfer function G is reduced. V gain.

[0025] In the above-mentioned vacuum exhaust device,

[0026] The vacuum pump may also include a magnetic bearing for suspending and supporting the rotor.

[0027] The control device is configured to change the opening of the valve and control the rotation speed of the rotor so that the pressure becomes consistent with the target value again when the pressure becomes consistent with the target value, when the rotation speed of the rotor becomes consistent with the natural frequency of the displacement of the rotor, or when the absolute value of the difference between the rotation speed and the natural frequency is less than a predetermined value.

[0028] In the above-mentioned vacuum exhaust device,

[0029] The predetermined value may be changed during the rotation of the rotor in accordance with at least one of an opening of the valve and a type and an amount of gas introduced into the evacuated chamber and evacuated by the vacuum pump.

[0030] In order to achieve the above-mentioned object, the vacuum pump according to the second embodiment of the present invention is:

[0031] Used in a vacuum exhaust device comprising a valve and a control device for controlling the pressure inside the exhaust chamber to be consistent with a target value.

[0032] The vacuum pump is characterized in that

[0033] The invention comprises a rotor for exhausting the interior of the exhaust chamber by rotating, a housing having an air intake port, and the valve is arranged between the air intake port and the exhaust port of the exhaust chamber.

[0034] The control device adjusts the opening of the valve when the absolute value of the difference between the target value and the pressure is greater than a predetermined value, and adjusts the rotation speed of the rotor when the absolute value of the difference is less than the predetermined value, thereby controlling the pressure.

[0035] In the above vacuum pump,

[0036] The control device may also perform control so that the rotation speed of the rotor is constant when the absolute value of the difference is greater than the predetermined value, and the opening of the valve is constant when the absolute value of the difference is less than the predetermined value.

[0037] In the above vacuum pump,

[0038] The control device may increase the transfer function G represented by the following equation (1) when the absolute value of the difference is greater than the predetermined value. V When the absolute value of the difference is less than the predetermined value, the transfer function G represented by the following formula (2) is increased. M The gain,

[0039] G V =O V / δP ・・・(1)

[0040] G M =Ω M / δ P ・・・(2)

[0041] In the above formula (1), O V is the Laplace transform of the valve opening with an initial value of 0. In the above equation (2), Ω M is the Laplace transform of the aforementioned rotor's rotational speed with an initial value of 0. In the above equations (1) and (2), δ P is the Laplace transform of the aforementioned difference with an initial value of 0.

[0042] In the above vacuum pump,

[0043] The control device may also reduce the transfer function G when the absolute value of the difference is greater than the predetermined value. M When the absolute value of the difference is less than the predetermined value, the transfer function G is reduced. V gain.

[0044] In the above vacuum pump,

[0045] It can also be equipped with a magnetic bearing for suspending and supporting the rotor.

[0046] The control device is configured to change the opening of the valve and control the rotation speed of the rotor so that the pressure becomes consistent with the target value again when the pressure becomes consistent with the target value, when the rotation speed of the rotor becomes consistent with the natural frequency of the displacement of the rotor, or when the absolute value of the difference between the rotation speed and the natural frequency is less than a predetermined value.

[0047] In the vacuum pump, the predetermined value may be changed during rotation of the rotor in accordance with at least one of an opening of the valve and a type and amount of gas introduced into the evacuated chamber and exhausted by the vacuum pump.

[0048] Effects of the Invention

[0049] According to the present invention, it is possible to provide a vacuum exhaust device capable of controlling the pressure in an exhaust chamber with high precision and high speed, and a vacuum pump used therefor. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a schematic structural diagram of a vacuum device including a vacuum exhaust device according to an embodiment of the present invention.

[0051] Figure 2It is a longitudinal sectional view showing the structure of a vacuum pump included in the vacuum exhaust device according to the embodiment of the present invention.

[0052] Figure 3 This is a graph showing the relationship between the position of the rotating shaft and the detection value of the position sensor.

[0053] Figure 4 This is a graph showing the relationship between the current value flowing in the electromagnet and the magnetic attraction force exerted on the rotating shaft by the electromagnet of the magnetic bearing.

[0054] Figure 5 This is a graph showing the relationship between the rotation frequency of the rotating shaft and the natural frequency of the rotor.

[0055] Figure 6 It is a schematic plan view showing the structure of a valve included in the vacuum exhaust device according to the embodiment of the present invention.

[0056] Figure 7 This is a block diagram showing a control system of a control device included in the vacuum exhaust apparatus according to the embodiment of the present invention.

[0057] Figure 8 (A) is a graph showing the relationship between the absolute value of the difference between the target pressure value and the measured pressure value and the gain of the valve opening; (B) is a graph showing the relationship between the absolute value of the difference between the target pressure value and the measured pressure value and the gain of the rotor rotation speed.

[0058] Description of Reference Numerals

[0059] 10 Vacuum exhaust device

[0060] 1 vacuum pump

[0061] 1a Rotation speed detector

[0062] 11a Inlet

[0063] 13 shell

[0064] 32 Pump motor

[0065] 33 Radial magnetic bearing

[0066] 34-axis magnetic bearings

[0067] 20 rotors

[0068] 2 valves

[0069] 2c valve body

[0070] 2d valve motor

[0071] 2e opening

[0072] 2f opening detector

[0073] 3 Control device

[0074] 4 Exhaust chamber

[0075] 5 pressure gauge

[0076] D Vacuum device. DETAILED DESCRIPTION

[0077] The vacuum exhaust device according to the embodiment of the present invention will be described with reference to the following drawings. Figure 1 As shown, it is a device included in a vacuum apparatus D used for thin film formation, etching, etc. in a semiconductor manufacturing apparatus. The vacuum exhaust apparatus 10 evacuates the pressure inside an exhaust chamber (vacuum chamber) 4 where a workpiece is placed to a desired pressure.

[0078] The vacuum exhaust device 10 includes a vacuum pump 1 for exhausting the process gas introduced into the exhaust chamber 4, an exhaust port (not shown) provided in the exhaust chamber 4, and an air intake port 11a ( Figure 2 ) and opens and closes the gas flow path; and a control device 3 that controls the pressure inside the exhaust chamber 4 to make it consistent with the target value.

[0079] The vacuum pump 1 is a turbomolecular pump, such as Figure 2 As shown, the outer cylinder 11, the base 12 to which the outer cylinder 11 is fixed, and the rotor 20 rotatably accommodated in the housing 13 composed of the outer cylinder 11 and the base 12. Figure 2 The upper side of the opening is formed to form a gas intake port 11a, and a gas exhaust port 12a is formed on the side of the base portion 12. A flange portion 11b is formed on the side of the intake port 11a of the outer tube portion 11, and the valve body 2a of the valve 2 is fixed to the flange portion 11b. Figure 6 )'s lower end surface.

[0080] The rotor 20 includes a rotor body 20a, a rotating shaft 30, and a washer 70. The rotating shaft 30 is rotatably supported in the housing 13 to rotate the rotor 20. Figure 2The upper outer peripheral surface of the rotor 20 is integrally formed with a plurality of blade-shaped rotating wings 21 inclined at a predetermined angle. The rotating wings 21 are radially arranged relative to the axis of the rotating shaft 30 of the rotor 20 and are arranged in multiple stages along the axis of the rotating shaft 30 of the rotor 20. Stationary wings 40 are provided between each stage of the rotating wings 21, and the rotating wings 21 and the stationary wings 40 are alternately arranged in the axis of the rotating shaft 30 of the rotor 20. The stationary wings 40 are also formed in multiple blade-like shapes inclined at a predetermined angle. The outer peripheral ends of the stationary wings 40 are sandwiched between a plurality of annular stationary wing spacers 50 stacked within the outer cylinder 11, thereby being radially and multi-staged between the rotating wings 21.

[0081] A threaded washer 60 is provided between the stationary blade washer 50 disposed on the most downstream side and the base portion 12. The threaded washer 60 is formed in a cylindrical shape and has a spiral thread groove 60a formed on the inner circumference. Figure 2 A cylindrical portion 22 is formed on the lower side (downstream side of gas transfer) centered on the axis of the rotating shaft 30. The outer circumferential surface of the cylindrical portion 22 and the inner circumferential surface of the threaded washer 60, which has a thread groove 60a formed therein, are disposed adjacent to and face each other. The space defined by the outer circumferential surface of the cylindrical portion 22 and the thread groove 60a of the threaded washer 60 communicates with the exhaust port 12a.

[0082] The washer 70 is formed in a disk shape centered on the axis of the rotating shaft 30 . The rotor body 20 a and the washer 70 are fixed to the rotating shaft 30 by screwing a bolt 71 onto the rotating shaft 30 via the rotor body 20 a and the washer 70 .

[0083] In the vacuum pump 1, if the rotor 20 is rotated at a high speed, the rotating blades 21 collide with the molecules of the gas sucked from the air inlet 11a in a manner that faces downstream. The collided gas molecules collide with the alternately arranged fixed blades 40 and face downward, and then collide with the rotating blades 21 of the next stage and face downstream, until the lowest stage of the rotating blades 21 and the fixed blades 40. This action is repeated in sequence, and the gas sent into the threaded gasket 60 is guided by the thread groove 60a and sent to the exhaust port 12a, and the gas is discharged from the exhaust port 12a. At this time, by adjusting the rotation speed of the rotor 20, the pressure inside the exhaust chamber 4 of the gas can be adjusted to the desired pressure. In addition, the vacuum pump 1 is as follows Figure 1 As shown, a rotation speed detector 1 a is provided for detecting the rotation speed of the rotor 20 . The rotation speed detection value of the rotor 20 detected by the rotation speed detector 1 a is output to the control device 3 .

[0084] On the rotating shaft 30 Figure 2Protective bearings 31 are located near the upper and lower sides (upstream and downstream of the gas flow) of the vacuum pump 1. In the event of an abnormality, such as when the radial magnetic bearings 33 and axial magnetic bearings 34 described later become uncontrollable, the protective bearings 31 contact and support the rotating shaft 30, thereby preventing damage to the vacuum pump 1.

[0085] The rotating shaft 30 is driven for rotation by a brushless DC pump motor 32. Two radial magnetic bearings 33 support the rotating shaft 30 radially, while an axial magnetic bearing 34 supports the rotating shaft 30 axially. The two radial magnetic bearings 33 are disposed across the pump motor 32. The rotating shaft 30 is suspended and supported by these radial magnetic bearings 33 and axial magnetic bearings 34.

[0086] Each of the two radial magnetic bearings 33 includes four electromagnets 33a that exert a magnetic attraction force on the rotating shaft 30. Two of the four electromagnets 33a are arranged on each of two coordinate axes that are perpendicular to the axis of the rotating shaft 30 and perpendicular to each other, with the rotating shaft 30 interposed between them. Furthermore, each of the two radial magnetic bearings 33 includes four inductive or eddy current position sensors 33b that detect the radial position of the rotating shaft 30. Two of the four position sensors 33b are arranged on each of two mutually perpendicular coordinate axes that are perpendicular to the axis of the rotating shaft 30 and parallel to the aforementioned coordinate axes, with the rotating shaft 30 interposed between them.

[0087] A magnetic disk (hereinafter referred to as the "armature disk") 80 is provided on the rotating shaft 30, centered around the axis of the rotating shaft 30. The axial magnetic bearing 34 includes two electromagnets 34a that exert a magnetic attraction force on the armature disk 80. The two electromagnets 34a are positioned across the armature disk 80. Furthermore, the axial magnetic bearing 34 includes an inductive or eddy current position sensor 34b that detects the axial position of the rotating shaft 30. The inductive or eddy current position sensor 33b of the radial magnetic bearing 33 and the inductive or eddy current position sensor 34b of the axial magnetic bearing 34 have the same structure as the electromagnets, with the core around which the wire coil is wound positioned opposite the rotating shaft 30.

[0088] The stator 90 is erected on the base portion 12 in order to protect the radial magnetic bearing 33 , the axial magnetic bearing 34 , the pump motor 32 , and the like from the attracted gas.

[0089] The vacuum pump 1 has a pump controller (not shown) that supplies power to the radial magnetic bearing 33, the axial magnetic bearing 34, and the pump motor 32 via cables or integrally therewith, and transmits and receives signals from the position sensors 33b and 34b. The pump controller supplies a high-frequency AC voltage of a predetermined amplitude to the wire coils of the position sensors 33b and 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 cores and the rotating shaft 30. In accordance with this change in inductance, the amplitude of the voltage applied to the wire coils changes, and the pump controller detects the position of the rotating shaft 30 by detecting this changed amplitude value. This amplitude value (position sensor detection value E) O )like Figure 3 As shown in FIG. 1 , the pump controller has a nonlinearity that increases or decreases in a curve relative to the position change of the rotating shaft 30. The pump controller is the sum of the amplitude values E of the two position sensors 33b that are opposite to each other across the rotating shaft 30 on each of the aforementioned coordinate axes. O1 +E O2 Because the change in the position of the rotating shaft 30 is quasi-linear (the difference is determined by the sign), calculating the sum (difference) and using this value as the detection signal of the position sensor 33b allows the application of linear control theory, and the position of the rotating shaft 30 can be controlled based on this theory. The pump controller uses feedback control to adjust the current flowing to the electromagnet 33a based on the sum (difference) of the detection signals from the two position sensors 33b on each coordinate axis, thereby aligning the position of the rotating shaft 30 with the target position.

[0090] The magnetic attraction force f exerted by each electromagnet 33a of the radial magnetic bearing 33 on the rotating shaft 30 is as follows: Figure 4 As shown, the current flowing to the electromagnet 33a also exhibits nonlinearity, increasing or decreasing in a curved manner with respect to changes in the current flowing to the electromagnet 33a. Therefore, the current value is adjusted as follows: for the two electromagnets 33a facing each other across the rotation axis 30 on each coordinate axis, a current (I0+i1) obtained by adding a predetermined DC current value (hereinafter referred to as "bias current value") I0 to a current value i1 flows through the electromagnet 33a that is offset from the target position and farther from the rotation axis 30. A current (I0-i1) obtained by subtracting the current value i1 from the bias current value I0 flows through the electromagnet 33a that is farther from the rotation axis 30. This allows the sum of the magnetic attraction forces acting on the two electromagnets 33a to be adjusted to f. hx1 + (-f hx2 ) is the magnetic attraction acting on the rotating shaft 30, so that the magnetic attraction is pseudo-linear with respect to the change of the current value, and the application of the aforementioned linear control theory becomes possible.

[0091] The structure of the axial magnetic bearing 34 is basically the same as that of the radial magnetic bearing 33. However, to reduce required space, rather than placing two position sensors across the armature disk 80 in the axial direction of the rotating shaft 30, only one position sensor 34b can be provided, with the other position sensor being replaced by a coil having a predetermined inductance on a circuit board within the controller. In this case, the inductance of the coil on the circuit board is a predetermined value, and the amplitude of the AC voltage is also a predetermined value. Therefore, the linearization accuracy of the sum (or difference) of the two position sensors relative to the position change of the rotating shaft 30 is reduced. However, this is useful in ensuring normal operation of the vacuum pump 1.

[0092] Furthermore, the rotor 20 is suspended in mid-air by these radial magnetic bearings 33 and axial magnetic bearings 34. However, this support force includes a component proportional to the change in the rotor 20's position, that is, a component equivalent to an elastic force. Therefore, the rotor 20 has a natural frequency corresponding to its mass or moment of inertia. The suspended rotor 20 has six degrees of freedom, including three degrees of freedom in the directions of the three axes of three-dimensional orthogonal coordinates, with one coordinate axis (hereinafter referred to as the "z-axis") aligning with the axis of the rotating shaft 30, and three degrees of freedom about each of these axes. Excluding the one degree of freedom about the z-axis, which controls the rotation angle by the pump motor 32, the remaining five degrees of freedom are supported by the radial and axial magnetic bearings 33 and 34, resulting in a natural frequency corresponding to the support forces of the radial and axial magnetic bearings 33 and 34. In particular, in the two degrees of freedom around two axes that are orthogonal to the z-axis and to each other (hereinafter referred to as the "x-axis" and the "y-axis," respectively), the equations of motion of rotor 20 include terms proportional to the rotational speed around these two axes (hereinafter referred to as "interference terms"), as shown in the following equations (3) representing the equation of motion around the x-axis and (4) representing the equation of motion around the y-axis. Furthermore, the magnitude of these interference terms is proportional to the rotational speed of rotating shaft 30, which is rotated by pump motor 32.

[0093]

Number 1

[0094]

[0095] However, in the above equations (3) and (4), J is the moment of inertia of the rotor 20 about the x-axis or y-axis, Jz is the moment of inertia of the rotor 20 about the z-axis, C is the viscous drag coefficient about the x-axis or y-axis, θx is the rotation angle of the rotor 20 about the x-axis, θy is the rotation angle of the rotor 20 about the y-axis, and θz is the rotation angle of the rotor 20 about the z-axis. Furthermore, in the above equation (3), Dx is the disturbance torque acting about the x-axis, and Gx is the spring constant of the torque about the x-axis generated by the support force of the radial magnetic bearing 33. Furthermore, in the above equation (4), Dy is the disturbance torque acting about the y-axis, and Gy is the spring constant of the torque about the y-axis generated by the support force of the radial magnetic bearing 33. Dx and Dy are generated by the imbalance of the rotor 20, the exhaust load of the vacuum pump 1, and the like. Gx and Gy actually have frequency characteristics corresponding to the control design of the radial magnetic bearing 33. As previously mentioned, the rotor 20 includes the rotor body 20a, the rotating shaft 30, and the washer 70. Therefore, the moment of inertia Jz and the moment of inertia J are, to be precise, the sum of the moments of inertia of the rotor body 20a, the rotating shaft 30, and the washer 70.

[0096] Typically, the formula for determining the natural frequency in each degree of freedom can be derived from the equation of motion for that degree of freedom. However, for the radial magnetic bearing 33's rotation about the x-axis and about the y-axis, the equations of motion for each have interfering terms, making it difficult to derive a formula for determining the natural frequency. Therefore, conventionally, the design of a specific magnetic bearing has relied on trial experiments and computer simulations using methods such as the finite element method to determine the value of the natural frequency of that specific magnetic bearing.

[0097] However, while these methods can determine the natural frequency for each specific magnetic bearing, they cannot qualitatively analyze how the natural frequency changes when the design values are changed. Therefore, after the design of a specific magnetic bearing is fully completed, the natural frequency is determined. If the design is changed for various reasons, the natural frequency must be recalculated again after the design change is completed. This inconvenience requires further changes and redesign, which consumes a significant amount of time in the design of magnetic bearings and turbomolecular pumps.

[0098] In the present invention, the radial magnetic bearing 33 of the vacuum pump 1, which is a turbomolecular pump, is used in a vacuum. By setting the viscous drag coefficient C = 0, equations (5) and (6) are derived from the above equations (3) and (4) to express the two natural frequencies ω1 and ω2 of the rotor 20 around the x-axis and the y-axis, respectively. The two natural frequencies expressed by equations (5) and (6) exist around both the x-axis and the y-axis.

[0099]

Number 2

[0100]

[0101] The natural frequencies ω1 and ω2 of the rotor 20 are as follows: Figure 5 As shown, as the rotating shaft 30 starts to rotate, the rotation frequency As the rotation frequency Ωz increases, the natural frequency ω1 decreases and the natural frequency ω2 increases. As the rotation frequency Ωz increases, the natural frequency ω2 approaches the rotation frequency Ωz, and after coinciding with the rotation frequency Ωz, it moves away from the rotation frequency Ωz.

[0102] If the natural frequencies ω1 and ω2 match or are close to the rotational frequency Ωz of the rotating shaft 30, resonance of the rotor 20 is induced, making it difficult for the radial magnetic bearings 33 and the axial magnetic bearings 34 to support the rotor 20 in a suspended manner. Furthermore, the rotor blades 21 continue to vibrate, and stress fluctuations repeatedly occur, leading to fatigue failure. Therefore, when the pressure inside the evacuated chamber 4 matches the target value, the control device 3 changes the opening of the valve 2, and controls the rotational speed of the rotor 20 so that the pressure inside the evacuated chamber 4 matches the target value, if the rotational speed of the rotor 20 (rotational frequency Ωz) matches the natural frequencies ω1 and ω2 of the displacement, or if the absolute value of the difference between the rotational speed of the rotor 20 and the natural frequencies ω1 and ω2 is less than a predetermined value.

[0103] Valve 2 Figure 6 As shown, the valve 2 comprises a valve body 2a, a valve body 2c fixed to a shaft 2b, a valve motor 2d that rotates the shaft 2b and oscillates the valve body 2c, and an opening 2e opened and closed by the valve body 2c. The valve 2 is disposed between the exhaust port (not shown) of the evacuated chamber 4 and the intake port 11a of the vacuum pump 1. The opening 2e of the valve 2 is arranged to communicate with and connect the exhaust port of the evacuated chamber 4 and the intake port 11a of the vacuum pump 1.

[0104] The valve 2 is configured such that the valve body 2c is swung by the valve motor 2d and placed at a desired position overlapping with the opening 2e. The opening degree is adjusted by adjusting the opening area of the opening 2e. By adjusting the opening degree of the valve 2, the pressure inside the exhaust chamber 4 can be adjusted to a desired pressure. Figure 1 As shown in FIG. 1 , an opening degree detector 2 f such as an encoder for detecting the opening degree is provided. The opening degree detection value of the valve 2 detected by the opening degree detector 2 f is output to the control device 3 .

[0105] The control device 3 controls the pressure inside the evacuated chamber 4 to a target value by adjusting the opening of the valve 2 and the rotational speed of the rotor 20 of the vacuum pump 1 according to predetermined conditions. The control device 3 includes a control unit (not shown), including a CPU (Central Processing Unit), and a storage unit (RAM (Random Access Memory), ROM (Read Only Memory), and flash memory. The storage unit stores various data, including programs executed by the control unit, fixed data, and detection data. Furthermore, the storage unit functions as the control unit's working memory. The control unit controls the pressure inside the evacuated chamber 4 by executing the programs stored in the storage unit.

[0106] When the opening of valve 2 is changed, the pressure in vented chamber 4 fluctuates significantly relative to the change in opening. For example, if the pressure in vented chamber 4 needs to be increased very slightly, even a very slight decrease in the opening of valve 2 will result in a significant pressure increase. If the pressure needs to be decreased very slightly, even a very slight increase in the opening of valve 2 will result in a significant pressure decrease. Furthermore, due to backlash in the gears that transmit the rotation of valve motor 2d to valve body 2c, elastic slippage, and sliding slippage of the belt, the position of valve body 2c relative to the rotation of valve motor 2d may produce errors, making it impossible to accurately achieve the desired opening. Therefore, when attempting to increase the gain of the change in valve 2 opening relative to pressure changes and reduce the steady-state deviation of pressure relative to the desired pressure for high-precision control, in the worst case, the opening of valve 2 will fluctuate, making it difficult to accurately achieve the desired pressure.

[0107] On the other hand, when the rotational speed of the rotor 20 of the vacuum pump 1 is varied, the pressure within the evacuated chamber 4 changes only slightly relative to the change in rotational speed. Therefore, if a significant change in the pressure within the evacuated chamber 4 is desired, the rotational speed of the rotor 20 must be varied significantly. However, when the vacuum pump 1 is a turbomolecular pump, the rotor 20 must rotate at high speed to achieve the desired evacuation performance. To achieve this, the rotor 20 is made of metals such as high-strength aluminum alloys that are resistant to damage even under high centrifugal forces, resulting in a large moment of inertia. Consequently, it is difficult to vary the rotational speed of the rotor 20 significantly in a short period of time, i.e., at high speed.

[0108] Another option is to use a high-torque motor for the pump motor 32 that drives the rotating rotor 20, and to increase the acceleration and deceleration torque. However, when using a relatively inexpensive brushless DC motor, increasing the torque constant also increases the induced voltage. Consequently, during high-speed rotation, the reverse voltage increases, preventing sufficient current from flowing to generate the acceleration and deceleration torque. Consequently, the rotational speed cannot be varied significantly at high speeds. This inability to vary the rotational speed of the rotor 20 significantly at high speeds hinders the increase in semiconductor production volume, for example, by increasing the time required to process the surface of wafers in semiconductor manufacturing equipment.

[0109] 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 greater than the predetermined value, the opening of the valve 2 is adjusted; when the absolute value of the difference between the pressure inside the exhaust chamber 4 and the target value is less than the predetermined value, the rotation speed of the rotor 20 of the vacuum pump 1 is adjusted to solve the above-mentioned problem.

[0110] Here, a method of controlling the vacuum exhaust by the control device 3 so that the pressure inside the exhaust chamber 4 becomes a desired pressure is described. Figure 1 As shown, a pressure gauge 5 is provided to measure the pressure in the exhaust chamber 4. The pressure measurement value by the pressure gauge 5 is output to the control device 3 and compared with the target pressure value in the control device 3.

[0111] When the absolute value of the difference between the target pressure value and the measured pressure value is greater than a predetermined value, the control device 3 sends a drive signal corresponding to the difference to the valve motor 2d of the valve 2 to adjust the opening of the valve 2. Figure 7 In the control system shown in FIG, let the transfer function G represented by the following equation (1) be V Gain of G V |such as Figure 8 (A) increases. In addition, at this time, the control device 3 can also be used in the opposite way. Figure 7 In the control system shown in FIG, let the transfer function G represented by the following equation (2) be M Gain of G M |such as Figure 8 At this time, the control device 3 may be used to control the rotation speed of the rotor 20 detected by the rotation speed detector 1 a so as to be kept constant.

[0112] G V =O V / δ P ・・・(1)

[0113] G M =Ω M / δ P・・・(2)

[0114] Here, in the above formula (1), O V is the Laplace transform of the initial value of the opening of valve 2 being 0. In the above equation (2), Ω M is the Laplace transform of the rotation speed of the rotor 20 with an initial value of 0. In the above equations (1) and (2), δ P This is a Laplace transform in which the initial value of the difference between the target pressure value and the measured pressure value is 0.

[0115] Here, increasing the gain means increasing it by 3 dB or more relative to the gain at a frequency of zero, i.e., the DC gain, and decreasing the gain means decreasing it by 3 dB or more relative to the gain at a frequency of zero, i.e., the DC gain. Alternatively, the average gain in an area smaller than a predetermined value of the absolute value of the difference between the target pressure value and the measured pressure value is increased or decreased relative to the average gain in an area larger than the predetermined value of the absolute value of the difference between the target pressure value and the measured pressure value. Alternatively, the average gain in an area larger than a predetermined value of the absolute value of the difference between the target pressure value and the measured pressure value is increased or decreased relative to the average gain in an area smaller than the predetermined value of the absolute value of the difference between the target pressure value and the measured pressure value.

[0116] On the other hand, when the absolute value of the difference between the target pressure value and the measured pressure value is less than a predetermined value, the control device 3 sends a drive signal corresponding to the value of the difference to the pump motor 32 of the vacuum pump 1 to adjust the rotation speed of the rotor 20. In this case, the control device 3 may increase the gain of the rotation speed of the rotor 20 relative to the absolute value of the difference between the target pressure value and the measured pressure value. M In addition, at this time, the control device 3 may also be used to reduce the gain of the valve 2 opening relative to the absolute value of the difference between the pressure target value and the pressure measurement value. V In addition, at this time, the control device 3 may also be used to control the opening of the valve 2 detected by the opening detector 2f so as to maintain a constant value. This allows the pressure in the exhaust chamber 4 to be controlled with high precision and high speed.

[0117] Next, a method will be described for resolving the aforementioned problem caused by resonance induction of the rotor 20 of the vacuum pump 1 by controlling the internal pressure of the exhaust chamber 4 to a desired pressure using the control device 3. The control device 3 compares the rotational speed of the rotor 20 detected by the rotational speed detector 1a with the natural frequencies ω1 and ω2 of the rotor 20. If the pressure measured by the pressure gauge 5 matches the target pressure value, or if the rotational speed of the rotor 20 matches the natural frequencies ω1 and ω2 and the absolute value of the difference is less than a predetermined value, the control device 3 sends an opening change command signal to the valve motor 2d to change the opening of the valve 2 by a predetermined amount. Furthermore, the control device 3 sends a drive signal corresponding to the difference between the target pressure value and the pressure measured by the pressure gauge 5 to the pump motor 32, thereby adjusting the rotational speed of the rotor 20 and controlling the pressure value to match the target pressure value.

[0118] In this embodiment, the control device 3 is used to adjust the opening of the valve 2 when the absolute value of the difference between the pressure inside the exhaust chamber 4 and the target value is greater than a predetermined value, and to adjust the rotation speed of the rotor 20 of the vacuum pump 1 when the absolute value of the difference between the pressure inside the exhaust chamber 4 and the target value is less than a predetermined value. Therefore, problems caused by changing the opening of the valve 2 and problems caused by changing the rotation speed of the rotor 20 can be avoided, and the pressure in the exhaust chamber 4 can be controlled to the desired pressure with high precision and in a short time, that is, at high speed.

[0119] While the present invention has been described above using embodiments, the present invention is not limited to the above embodiments and is capable of various modifications. For example, the above embodiments describe a valve 2 in which a valve motor 2d is used to swing a valve body 2c to a desired position overlapping an opening 2e, thereby adjusting the opening area of the opening 2e and thereby adjusting the degree of opening. However, the valve structure is not limited to this; any valve capable of opening and closing a gas flow path may be used, and a butterfly-type or wing-type valve, for example, may also be used. Furthermore, a valve in which the valve body 2c is driven by pressurized air generated by a compressor, for example, may be used in place of the valve motor 2d, gears, or belts.

[0120] Furthermore, in the present invention, a method for controlling the pressure in the exhaust chamber 4 is provided for changing the pressure depending on whether the absolute value of the difference between the target pressure value and the measured pressure value is larger or smaller than a predetermined value. The predetermined value can be appropriately determined depending on the type of vacuum device D, such as a semiconductor manufacturing device, an electron microscope, a surface analysis device, or a micromachining device, for which the vacuum exhaust device 10 is used, and the conditions and circumstances under which the vacuum exhaust device 10, the structure and type of the vacuum pump 1, and the valve 2 are used.

[0121] Furthermore, the preset value may be appropriately changed during the rotation of the rotor 20 according to the opening of the valve 2, the type and amount of process gas introduced into the evacuated chamber 4 and exhausted by the vacuum pump 1, and the like. In this case, a plurality of preset values are pre-stored in the storage unit of the control device 3, and the preset value may be appropriately selected or calculated in accordance with these preset values to change the preset value.

Claims

1. A vacuum exhaust device comprising: The vacuum pump comprises a rotor that exhausts the interior of the exhaust chamber by rotating, and a housing having an air intake port. The valve is arranged between the suction port of the vacuum pump and the exhaust port of the exhaust chamber. The control device controls the pressure inside the exhaust chamber to be consistent with the target value, The vacuum exhaust device is characterized in that: The control device is configured to control and adjust the opening of the valve so that the rotation speed of the rotor is constant when the absolute value of the difference between the target value and the pressure is greater than a predetermined value, and to control and adjust the rotation speed of the rotor so that the opening of the valve is constant when the absolute value of the difference is less than the predetermined value, thereby controlling the pressure.

2. A vacuum exhaust device comprising: The vacuum pump comprises a rotor that exhausts the interior of the exhaust chamber by rotating, and a housing having an air intake port. The valve is arranged between the suction port of the vacuum pump and the exhaust port of the exhaust chamber. The control device controls the pressure inside the exhaust chamber to be consistent with the target value, The vacuum exhaust device is characterized in that: The control device increases the transfer function G represented by the following equation (1) when the absolute value of the difference between the target value and the pressure is greater than a predetermined value. V The gain of the valve is adjusted to adjust the opening of the valve. When the absolute value of the difference is smaller than the predetermined value, the transfer function G represented by the following formula (2) is increased. M The gain of the rotor is adjusted to adjust the rotation speed of the rotor, thereby controlling the pressure. G V =O V / d P ···(1) G M =Oh M / d P ···(2) in, In the above formula (1), O V is the Laplace transform of the valve opening with an initial value of 0. In the above equation (2), Ω M is the Laplace transform of the aforementioned rotor's rotational speed with an initial value of 0. In the above equations (1) and (2), δ P is the Laplace transform of the aforementioned difference with an initial value of 0.

3. The vacuum exhaust device according to claim 2, wherein: The control device reduces the transfer function G when the absolute value of the difference is greater than the predetermined value. M When the absolute value of the difference is less than the predetermined value, the transfer function G is reduced. V gain.

4. The vacuum exhaust device according to any one of claims 1 to 3, characterized in that: The vacuum pump is provided with a magnetic bearing for suspending and supporting the rotor. The control device is configured to change the opening of the valve and control the rotation speed of the rotor so that the pressure again matches the target value when the pressure matches the target value, when the rotation speed of the rotor matches the natural frequency of the displacement of the rotor, or when the absolute value of the difference between the rotation speed and the natural frequency is less than a predetermined value.

5. The vacuum exhaust device according to claim 1 or 2, characterized in that: The predetermined value is changed during the rotation of the rotor in accordance with at least one of an opening degree of the valve and a type and an amount of gas introduced into the evacuated chamber and exhausted by the vacuum pump.

6. A vacuum pump for use in a vacuum exhaust device, the vacuum exhaust device comprising a valve and a control device for controlling the pressure inside an exhaust chamber to be matched with a target value. The vacuum pump is characterized in that The invention comprises a rotor for exhausting the interior of the exhaust chamber by rotating, a housing having an air intake port, and the valve is arranged between the air intake port and the exhaust port of the exhaust chamber. The control device is configured to control and adjust the opening of the valve so that the rotation speed of the rotor remains constant when the absolute value of the difference between the target value and the pressure is greater than a predetermined value, and to control and adjust the rotation speed of the rotor so that the opening of the valve remains constant so as to control the pressure when the absolute value of the difference between the target value and the pressure is less than the predetermined value.

7. A vacuum pump for use in a vacuum exhaust device, the vacuum exhaust device comprising a valve and a control device for controlling the pressure inside an exhaust chamber to be matched with a target value. The vacuum pump is characterized in that The invention comprises a rotor for exhausting the interior of the exhaust chamber by rotating, a housing having an air intake port, and the valve is arranged between the air intake port and the exhaust port of the exhaust chamber. The control device increases the transfer function G represented by the following equation (1) when the absolute value of the difference between the target value and the pressure is greater than a predetermined value. V The gain of the valve is adjusted to adjust the opening of the valve. When the absolute value of the difference is smaller than the predetermined value, the transfer function G represented by the following formula (2) is increased. M The gain of the rotor is adjusted to adjust the rotation speed of the rotor, thereby controlling the pressure. G V =O V / d P ···(1) G M =Oh M / d P ···(2) in, In the above formula (1), O V is the Laplace transform of the valve opening with an initial value of 0. In the above equation (2), Ω M is the Laplace transform of the aforementioned rotor's rotational speed with an initial value of 0. In the above equations (1) and (2), δ P is the Laplace transform of the aforementioned difference with an initial value of 0.

8. The vacuum pump according to claim 7, characterized in that The control device reduces the transfer function G when the absolute value of the difference is greater than the predetermined value. M When the absolute value of the difference is less than the predetermined value, the transfer function G is reduced. V gain.

9. The vacuum pump according to any one of claims 6 to 8, characterized in that A magnetic bearing for suspending and supporting the rotor. The control device is configured to change the opening of the valve and control the rotation speed of the rotor so that the pressure again matches the target value when the pressure matches the target value, when the rotation speed of the rotor matches the natural frequency of the displacement of the rotor, or when the absolute value of the difference between the rotation speed and the natural frequency is less than a predetermined value.

10. The vacuum pump according to claim 6 or 7, characterized in that The predetermined value is changed during the rotation of the rotor in accordance with at least one of an opening degree of the valve and a type and an amount of gas introduced into the evacuated chamber and exhausted by the vacuum pump.

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