Vacuum exhaust system and vacuum pump

Abstract

Provided is a vacuum exhaust system with which reductions in cost and size and / or an increase in the degree of freedom pertaining to piping design can be achieved. A vacuum exhaust system 10 for exhausting a process gas from a plurality of chambers 10-1 to 10-n includes a plurality of turbo molecular pumps 100-1 to 100-n, a collecting pipe 14 to which outlet ports of the plurality of turbo molecular pumps are connected in parallel, one or more dry pumps 16 connected to the collecting pipe 14, and chamber introduction valve devices 30-1 to 30-n for controlling a flow rate of a gas introduced into the plurality of chambers 10-1 to 10-n, wherein an exhaust flow rate threshold T of the process gas is set on the basis of a flow rate that can be exhausted by the plurality of turbo molecular pumps 100-1 to 100-n, and at least one of an introduction timing and the flow rate of the gas is controlled by the chamber introduction valve devices 30-1 to 30-n so as not to exceed the exhaust flow rate threshold T.

Description

[Technical Field]

[0001] The present invention relates to a vacuum exhaust system including a vacuum pump such as a turbo molecular pump, for example, and a vacuum pump used in the vacuum exhaust system.[Background Art]

[0002] A turbo molecular pump is generally known as a type of vacuum pump. In the turbo molecular pump, gas (process gas) that has been sucked into a pump main body is exhausted by applying a current to a motor in the pump main body in order to rotate rotor blades, whereby gas molecules of the gas are flicked away. This type of turbo molecular pump may also include a heater and a cooling pipe in order to manage an internal temperature of the pump appropriately.

[0003] Furthermore, in a vacuum exhaust system relating to a device for manufacturing a semiconductor, a flat panel, or the like (referred to hereinafter as a "semiconductor or the like"), as illustrated in Fig. 1 of PTL 1, cited below, for example, a plurality of turbo molecular pumps (TMPs) may be provided. Here, as disclosed in PTL 1, a type of system in which a single back pump (also known as a BP or a "dry pump") is disposed for the plurality of turbo molecular pumps is known as a central exhaust-type vacuum exhaust system (a central exhaust system).[Citation List][Patent Literature]

[0004] [PTL 1] Japanese Patent Application Publication No. 2015-227618[Summary of Invention][Technical Problem]

[0005] A typical turbo molecular pump is dependent on back pressure (secondary-side pressure) (known as back pressure dependency), and when the back pressure takes a certain value (an allowable back pressure) or more, intake pressure (inlet port pressure) cannot be maintained. Likewise in the central exhaust system described above, the back pressure of the turbo molecular pump has to be held at or below the allowable back pressure.

[0006] However, a maximum flow rate of a gas used in the central exhaust system is assumed by multiplying the number of process chambers (also referred to as "processing chambers", "vacuum chambers", and so on) used to manufacture the semiconductor or the like by a maximum flow rate per process chamber. In other words, when the maximum flow rate per process chamber is set as Qmax and the number of process chambers is set as n, the maximum flow rate of the gas is calculated as Qmax × n. In order to reduce the back pressure of the turbo molecular pump to or below the allowable back pressure, therefore, it is necessary to increase the size (increase an exhaust speed) of the back pump (the dry pump), use piping with low conductance, or employ a turbo molecular pump that exhibits superior back pressure dependency, and as a result, the cost of the exhaust system is likely to increase.

[0007] An object of the present invention is to provide a vacuum exhaust system with which reductions in cost and size and / or an increase in the degree of freedom pertaining to piping design can be achieved, and a vacuum pump used in the vacuum exhaust system.[Solution to Problem]

[0008] (1) To achieve the object described above, a vacuum exhaust system according to the present invention is a vacuum exhaust system for exhausting a processing gas from a plurality of processing chambers, the vacuum exhaust system including: a plurality of first vacuum pumps; a collecting pipe to which outlet ports of the plurality of first vacuum pumps are connected in parallel; one or more second vacuum pumps connected to the collecting pipe; and a gas introduction amount control means for controlling a flow rate of a gas introduced into the plurality of processing chambers, wherein an exhaust flow rate threshold of the processing gas is set on the basis of a flow rate that can be exhausted by the plurality of first vacuum pumps, and at least one of an introduction timing and the flow rate of the gas is controlled by the gas introduction amount control means so as not to exceed the exhaust flow rate threshold. (2) Further, to achieve the object described above, a vacuum pump according to the present invention is used as the first vacuum pumps provided in the vacuum exhaust system. [Advantageous Effects of Invention]

[0009] According to the inventions described above, it is possible to provide a vacuum exhaust system with which reductions in cost and size and / or an increase in the degree of freedom pertaining to the piping design can be achieved, and a vacuum pump used in the vacuum exhaust system.[Brief Description of Drawings]

[0010] [Fig. 1] Fig. 1 is a schematic illustrative view showing configurations of a vacuum pump and a vacuum exhaust system according to a first embodiment of the present invention. [Fig. 2] Fig. 2 is a circuit diagram of an amplifier circuit. [Fig. 3] Fig. 3 is a time chart showing control performed when a current command value is larger than a detection value. [Fig. 4] Fig. 4 is a time chart showing control performed when the current command value is smaller than the detection value. [Fig. 5] Fig. 5(a) is a schematic illustrative view showing a central exhaust-type vacuum exhaust system according to an embodiment, and Fig. 5(b) is a schematic illustrative view showing a distributed exhaust-type vacuum exhaust system as a conventional example. [Fig. 6] Fig. 6 is a graph showing an example of variation in an amount of exhaust in a single turbo molecular pump. [Fig. 7] Fig. 7 is a schematic block diagram showing an exhaust system control unit. [Description of Embodiments]<Turbo molecular pump 100>

[0011] A vacuum exhaust system 10 according to an embodiment of the present invention and a vacuum pump that can be used in the vacuum exhaust system 10 will be described below on the basis of the figures. First, Fig. 1 is a longitudinal sectional view of a turbo molecular pump 100 serving as a vacuum pump according to an embodiment of the present invention.

[0012] In the turbo molecular pump 100 of Fig. 1, an inlet port 101 is formed in an upper end of a cylindrical outer tube 127. A rotating body 103 in which a plurality of rotor blades 102 (102a, 102b, 102c, ...) are formed on a peripheral portion radially and in multiple stages, the rotor blades 102 serving as turbine blades for sucking and exhausting gas, is installed in the outer tube 127. A rotor shaft 113 is mounted in the center of the rotating body 103, and the rotor shaft 113 is supported and positionally controlled so as to levitate in the air by a 5-axis control magnetic bearing, for example.

[0013] Upper-side radial electromagnets 104 are arranged by disposing four electromagnets in pairs respectively on an X axis and a Y axis. Four upper-side radial sensors 107 are provided in proximity to the upper-side radial electromagnets 104 so as to correspond respectively to the upper-side radial electromagnets 104. The upper-side radial sensors 107 employ inductance sensors, eddy current sensors, or the like having a conductive winding, for example, and detect the position of the rotor shaft 113 on the basis of variation in the inductance of the conductive winding, which varies in accordance with the position of the rotor shaft 113. The upper-side radial sensors 107 are configured to detect radial displacement of the rotor shaft 113, or in other words the rotating body 103 fixed thereto, and transmit the detected displacement to a control device 200.

[0014] In the control device 200, a compensation circuit having a PID adjustment function, for example, generates excitation control command signals for the upper-side radial electromagnets 104 on the basis of position signals detected by the upper-side radial sensors 107, whereupon an amplifier circuit 150 shown in Fig. 2 (to be described below) controls excitation of the upper-side radial electromagnets 104 on the basis of the excitation control command signals, thereby adjusting the upper-side radial position of the rotor shaft 113.

[0015] The rotor shaft 113 is formed from a material (iron, stainless steel, or the like) with high magnetic permeability or the like so as to be attracted by the magnetic force of the upper-side radial electromagnets 104. The aforesaid adjustment is performed independently in each of an X axis direction and a Y axis direction. Furthermore, lower-side radial electromagnets 105 and lower-side radial sensors 108 are arranged similarly to the upper-side radial electromagnets 104 and the upper-side radial sensors 107 so that the lower-side radial position of the rotor shaft 113 is adjusted in a similar manner to the upper-side radial position.

[0016] Furthermore, axial electromagnets 106A, 106B are arranged above and below a disc-shaped metal disc (also referred to as an "armature disc") 111 provided in a lower portion of the rotor shaft 113. The metal disc 111 is formed from a material having high magnetic permeability, such as iron. An axial sensor 109 is provided to detect axial displacement of the rotor shaft 113, and an axial position signal therefrom is transmitted to the control device 200.

[0017] In the control device 200, the compensation circuit having a PID adjustment function, for example, generates an excitation control command signal for each of the axial electromagnet 106A and the axial electromagnet 106B on the basis of the axial position signal detected by the axial sensor 109, whereupon the amplifier circuit 150 controls excitation of each of the axial electromagnet 106A and the axial electromagnet 106B on the basis of the excitation control command signals. Accordingly, the axial electromagnet 106A attracts the metal disc 111 upward by magnetic force, the axial electromagnet 106B attracts the metal disc 111 downward by magnetic force, and as a result, the axial position of the rotor shaft 113 is adjusted.

[0018] Thus, the control device 200 is configured to appropriately adjust the magnetic force exerted on the metal disc 111 by the axial electromagnets 106A, 106B, whereby the rotor shaft 113 is magnetically levitated in an axial direction so as to be held in space without contact. Note that the amplifier circuit 150 that controls excitation of the upper-side radial electromagnets 104, the lower-side radial electromagnets 105, and the axial electromagnets 106A, 106B will be described below.

[0019] Meanwhile, a motor 121 includes a plurality of magnetic poles arranged peripherally so as to surround the rotor shaft 113. Each magnetic pole is controlled by the control device 200 so as to drive the rotor shaft 113 to rotate through electromagnetic force acting between the magnetic poles and the rotor shaft 113. Further, a rotation speed sensor such as a Hall element, a resolver, or an encoder, for example, not shown in the figures, is incorporated into the motor 121, and from a detection signal from the rotation speed sensor, the rotation speed of the rotor shaft 113 is detected.

[0020] Furthermore, for example, a phase sensor, not shown in the figures, is mounted near the lower-side radial sensors 108 in order to detect the phase of the rotation of the rotor shaft 113. In the control device 200, detection signals from the phase sensor and the rotation speed sensor are used together to detect the positions of the magnetic poles.

[0021] A plurality of stator blades 123 (123a, 123b, 123c, ...) are arranged at slight intervals (predetermined intervals) from the rotor blades 102 (102a, 102b, 102c, ...). The rotor blades 102 (102a, 102b, 102c, ...) are formed at an incline of a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113 in order to respectively collide with molecules of exhaust gas and thereby convey the exhaust gas downward.

[0022] Further, the stator blades 123 are likewise formed at an incline of a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113, and are arranged alternately with the stages of the rotor blades 102 so as to face the inside of the outer tube 127. Outer peripheral ends of the stator blades 123 are supported in a state of being inserted with play between a plurality of stacked stator blade spacers 125 (125a, 125b, 125c, ...).

[0023] The stator blade spacers 125 are ring-shaped members formed from a metal such as aluminum, iron, stainless steel, or copper, or a metal such as an alloy containing these metals as a component, for example. The outer tube 127 is fixed to the outer periphery of the stator blade spacers 125 with a slight gap left therebetween. The base portion 129 is disposed on a bottom portion of the outer tube 127. An outlet port 133 is formed to the base portion 129 and connected to the outside. Exhaust gas that enters the inlet port 101 from the side of a chamber (a vacuum chamber, a processing chamber) so as to be conveyed toward the base portion 129 is sent to the outlet port 133.

[0024] Moreover, in accordance with the application of the turbo molecular pump 100, a screw spacer 131 is arranged between a lower portion of the stator blade spacers 125 and the base portion 129. The screw spacer 131 is a cylindrical member formed from a metal such as aluminum, copper, stainless steel, or iron, or an alloy containing these metals as a component, and has a plurality of spiral-shaped thread grooves 131a engraved in an inner peripheral surface thereof. The direction of the spirals of the thread grooves 131a is the direction in which molecules of the exhaust gas are conveyed toward the outlet port 133 when the molecules move in the rotation direction of the rotating body 103. A rotating body lower portion cylindrical portion 103b is suspended from a lower portion of a rotating body main body 103a of the rotating body 103, in which the rotor blades 102 (102a, 102b, 102c, ...) are formed. An outer peripheral surface of the rotating body lower portion cylindrical portion 103b is cylindrical and protrudes toward the inner peripheral surface of the screw spacer 131 so as to approach the inner peripheral surface of the screw spacer 131 with a predetermined gap left therebetween. The exhaust gas that is conveyed to the thread grooves 131a by the rotor blades 102 and stator blades 123 is sent to the base portion 129 while being guided by the thread grooves 131a. Thus, the screw spacer 131 and the opposing rotating body lower portion cylindrical portion 103b together form a Holweck exhaust mechanism unit 204. In the Holweck exhaust mechanism unit 204, the rotating body lower portion cylindrical portion 103b rotates relative to the screw spacer 131, thereby giving direction to the exhaust gas, and as a result, the exhaust characteristic of the turbo molecular pump 100 is improved.

[0025] The base portion 129 is a disc-shaped member forming a bottom portion of the turbo molecular pump 100, and is typically formed from a metal such as iron, aluminum, or stainless steel. The base portion 129 physically holds the turbo molecular pump 100 and also functions as a heat conduction path, and therefore a metal that is rigid and has high thermal conductivity, such as iron, aluminum, or copper, is preferably used.

[0026] In this configuration, when the rotor blades 102 are driven to rotate together with the rotor shaft 113 by the motor 121, exhaust gas is sucked from the chamber through the inlet port 101 by the actions of the rotor blades 102 and stator blades 123. The exhaust gas sucked through the inlet port 101 passes between the rotor blades 102 and the stator blades 123 so as to be conveyed to the base portion 129. At this time, the temperature of the rotor blades 102 increases due to friction heat generated when the exhaust gas comes into contact with the rotor blades 102, conduction of the heat generated by the motor 121, and so on, and this heat is transmitted to the stator blade 123 side by radiation or by being conducted by the gas molecules of the exhaust gas.

[0027] The stator blade spacers 125 are joined to each other by outer peripheral portions thereof so that the heat received by the stator blades 123 from the rotor blades 102, the friction heat generated when the exhaust gas comes into contact with the stator blades 123, and so on are transmitted to the outside.

[0028] Note that in the above description, the screw spacer 131 is disposed on the outer periphery of the rotating body lower portion cylindrical portion 103d of the rotating body 103, and the thread grooves 131a are engraved in the inner peripheral surface of the screw spacer 131. Conversely, however, the thread grooves may be engraved in the outer peripheral surface of the rotating body lower portion cylindrical portion 103b, and a spacer having a cylindrical inner peripheral surface may be disposed on the periphery thereof.

[0029] Furthermore, depending on the application of the turbo molecular pump 100, the periphery of electrical parts including the upper-side radial electromagnets 104, the upper-side radial sensors 107, the motor 121, the lower-side radial electromagnets 105, the lower-side radial sensors 108, the axial electromagnets 106A, 106B, the axial sensor 109, and so on may be covered by a stator column 122, and the interior of the stator column 122 may be maintained at a predetermined pressure using a purge gas (a protective gas), thereby ensuring that the gas sucked through the inlet port 101 does not infiltrate the electrical parts.

[0030] In this case, a purge gas introduction pipe (also referred to as a "purge gas port") 13 is disposed in the base portion 129, and the purge gas is introduced through this pipe. The introduced purge gas is conveyed to the outlet port 133 through a gap between a protective bearing 120 and the rotor shaft 113, a gap between a rotor and a stator of the motor 121, and gaps between the stator column 122 and inner peripheral-side cylindrical portions of the rotor blades 102 (the rotating body lower portion cylindrical portion 103b) and the base portion 129 .

[0031] Here, the turbo molecular pump 100 requires control based on model specification and individually regulated unique parameters (for example, characteristics corresponding to the model). In order to store these control parameters, the turbo molecular pump 100 includes, in a main body thereof, an electronic circuit portion 141. The electronic circuit portion 141 is constituted by a semiconductor memory such as an EEP-ROM, an electronic component such as a semiconductor element for accessing the semiconductor memory, a substrate 143 on which these components are mounted, and so on. The electronic circuit portion 141 is housed in a lower portion of a rotation speed sensor, not shown in the figures, near the center, for example, of the base portion 129 constituting the lower portion of the turbo molecular pump 100, and is closed by an airtight bottom lid 145.

[0032] Incidentally, in a semiconductor manufacturing process, a process gas introduced into a chamber may have a property whereby the process gas becomes a solid when the pressure thereof increases beyond a predetermined value or the temperature thereof decreases below a predetermined value. In the interior of the turbo molecular pump 100, the pressure of the exhaust gas is lowest in the inlet port 101 and highest in the outlet port 133. When the pressure of the process gas increases beyond a predetermined value or the temperature thereof decreases below a predetermined value as the process gas is conveyed from the inlet port 101 to the outlet port, the process gas takes a solid form, and the solid adheres to and is deposited in the interior of the turbo molecular pump 100.

[0033] For example, when SiCl4 is used as a process gas in an Al etching device, it can be seen from the vapor pressure curve that at low vacuum (760 [torr] to 10-2 [torr]) and low temperature (approximately 20 [°C]), a solid product (AlCl3, for example) is precipitated, and the solid product adheres to and is deposited in the interior of the turbo molecular pump 100. When, as a result, the precipitate of the process gas accumulates in the interior of the turbo molecular pump 100, the deposit narrows the pump flow passage, causing a reduction in the performance of the turbo molecular pump 100. Moreover, the aforesaid product is more likely to coagulate in and adhere to high-pressure parts near the outlet port 133 and the screw spacer 131.

[0034] Hence, to solve this problem, conventionally, a heater, not shown in the figures, or an annular (ring-shaped ) water-cooling pipe 149 is wrapped around the outer periphery of the base portion 129 and so on, a temperature sensor (a thermistor, for example), not shown in the figures, is embedded in the base portion 129, for example, and control (referred to hereinafter as a TMS (Temperature Management System)) is performed to heat the heater or provide cooling through the water-cooling pipe 149 on the basis of a signal from the temperature sensor so as to maintain the temperature of the base portion 129 at a constant high temperature (a set temperature). In the turbo molecular pump 100 of the first embodiment, a large amount of hot air (a high-temperature fluid, a heating fluid) is introduced into the interior of the turbo molecular pump 100 in order to heat and vaporize (clean) the deposits. Vaporization of the deposits using hot air will be described below.

[0035] Next, the amplifier circuit 150 for controlling excitation of the upper-side radial electromagnets 104, the lower-side radial electromagnets 105, and the axial electromagnets 106A, 106B will be described in relation to the turbo molecular pump 100 configured as described above. Fig. 2 is a circuit diagram of the amplifier circuit.

[0036] In Fig. 2, an electromagnet winding 151 constituting the upper-side radial electromagnets 104 and so on is connected at one end to a positive electrode 171a of a power supply 171 via a transistor 161 and connected at the other end to a negative electrode 171b of the power supply 171 via a current detection circuit 181 and a transistor 162. The transistors 161, 162 are so-called power MOSFETs, and are structured such that a diode is connected between the source and the drain thereof.

[0037] At this time, the transistor 161 is configured such that a cathode terminal 161a of the diode thereof is connected to the positive electrode 171a, and an anode terminal 161b is connected to one end of the electromagnet winding 151. Further, the transistor 162 is configured such that a cathode terminal 162a of the diode thereof is connected to the current detection circuit 181, and an anode terminal 162b is connected to the negative electrode 171b.

[0038] Meanwhile, a current regeneration diode 165 is configured such that a cathode terminal 165a thereof is connected to one end of the electromagnet winding 151, and an anode terminal 165b thereof is connected to the negative electrode 171b. Similarly, a current regeneration diode 166 is configured such that a cathode terminal 166a thereof is connected to the positive electrode 171a, and an anode terminal 166b thereof is connected to the other end of the electromagnet winding 151 via the current detection circuit 181. The current detection circuit 181 is constituted by, for example, a Hall sensor-type current sensor or an electrical resistor element.

[0039] The amplifier circuit 150 configured as described above corresponds to one electromagnet. Accordingly, in a case where the magnetic bearing performs 5-axis control and the electromagnets 104, 105, 106A, 106B total ten in number, a similar amplifier circuit 150 is formed for each electromagnet such that ten amplifier circuits 150 are connected in parallel to the power supply 171.

[0040] Furthermore, an amplifier control circuit 191 is constituted by, for example, a digital signal processor unit (referred to hereinafter as a DSP unit), not shown in the figures, of the control device 200, and the amplifier control circuit 191 switches the transistors 161, 162 ON and OFF.

[0041] The amplifier control circuit 191 compares a current value detected by the current detection circuit 181 (a signal reflecting this current value will be referred to as a current detection signal 191c) with a predetermined current command value. The magnitude (pulse width times Tp1, Tp2) of a pulse width generated in a control cycle Ts serving as one period of PWM control is then determined on the basis of the comparison result. As a result, gate drive signals 191a, 191b having this pulse width are output from the amplifier control circuit 191 to the gate terminals of the transistors 161, 162.

[0042] Note that when the rotation speed of the rotating body 103 passes through the resonance point during an acceleration operation, when a disturbance occurs during a constant speed operation, and so on, it is necessary to control the position of the rotating body 103 at high speed and with great force. Therefore, a high voltage of approximately 50 V, for example, is used as the power supply 171 so that the current flowing through the electromagnet winding 151 can be rapidly increased (or reduced). Further, a capacitor is normally connected between the positive electrode 171a and the negative electrode 171b of the power supply 171 in order to stabilize the power supply 171 (not shown).

[0043] In this configuration, when the transistors 161, 162 are both switched ON, the current (referred to hereinafter as an electromagnet current iL) flowing through the electromagnet winding 151 increases, and when the transistors 161, 162 are both switched OFF, the electromagnet current iL decreases.

[0044] Further, when one of the transistors 161, 162 is switched ON and the other is switched OFF, a so-called flywheel current is maintained. By passing a flywheel current through the amplifier circuit 150 in this manner, hysteresis loss in the amplifier circuit 150 can be reduced, making it possible to suppress the power consumption of the circuit as a whole. Moreover, by controlling the transistors 161, 162 in this manner, high frequency noise such as harmonics generated in the turbo molecular pump 100 can be reduced. Furthermore, by measuring the flywheel current using the current detection circuit 181, the electromagnet current iL flowing through the electromagnet winding 151 can be detected.

[0045] More specifically, as shown in Fig. 3, when the detected current value is smaller than the current command value, the transistors 161, 162 are both switched ON for a time corresponding to the pulse width time Tp1 once during the control cycle Ts (100 µs, for example). Accordingly, the electromagnet current iL during this period increases from the positive electrode 171a to the negative electrode 171b in the direction of a current value iLmax (not shown) that can flow through the transistors 161, 162.

[0046] As shown in Fig. 4, meanwhile, when the detected current value is larger than the current command value, the transistors 161, 162 are both switched OFF for a time corresponding to the pulse width time Tp2 once during the control cycle Ts. Accordingly, the electromagnet current iL during this period decreases from the negative electrode 171b to the positive electrode 171a in the direction of a current value iLmin (not shown) that can be regenerated through the diodes 165, 166.

[0047] In both cases, following the elapse of the pulse width times Tp1, Tp2, one of the transistors 161, 162 is switched ON. Accordingly, during this period, a flywheel current is maintained in the amplifier circuit 150.

[0048] Thus, in the turbo molecular pump 100 having this basic configuration, the upper side of Fig. 1 (the side of the inlet port 101) serves as an intake portion connected to the side of a subject device, and the lower side (the side on which the base portion 129 is provided and an exhaust port 15 constituting the outlet port 133 projects rightward in the figure) serves as an exhaust portion connected to an auxiliary pump (a dry pump 16 to be described below, also referred to as a "back pump" or the like) or the like, not shown in the figure. As well as the vertically upright attitude shown in Fig. 1, the turbo molecular pump 100 can also be used in an inverted attitude, a horizontal attitude, or a tilted attitude.

[0049] Furthermore, in the turbo molecular pump 100, the outer tube 127 and the base portion 129, described above, are combined to form a single case (a combination of the two components will also be referred to hereinafter as a "main body casing" or the like). Moreover, the turbo molecular pump 100 is electrically (and structurally) connected to a box-shaped electrical case (not shown), and the control device 200 is incorporated into the electrical case.

[0050] The internal configuration of the main body casing (the combined outer tube 127 and base portion 129) of the turbo molecular pump 100 can be divided into a rotary mechanism unit for rotating the rotor shaft 113 and so on using the motor 121, and an exhaust mechanism unit that is driven to rotate by the rotary mechanism unit. Further, the exhaust mechanism unit can be considered to be divided into a turbo molecular pump mechanism unit constituted by the rotor blades 102, the stator blades 123, and so on, and a thread groove pump mechanism unit (the Holweck exhaust mechanism unit 204) constituted by the rotating body lower portion cylindrical portion 103b, the screw spacer 131, and so on.

[0051] Furthermore, the aforementioned purge gas (a protective gas) is used to protect the bearing part, the rotor blades 102, and so on by preventing corrosion caused by the exhaust gas (the process gas), cooling the rotor blades 102, and so on. The purge gas can be supplied by a typical method.

[0052] For example, a purge gas port 13 extending radially in a straight line is provided in a predetermined site of the base portion 129 (a position substantially 180 degrees away from the outlet port 133, or the like). The purge gas is supplied to the purge gas port 13 from the outside of the base portion 129 through a purge gas cylinder (an N2 gas cylinder or the like), a flow rate controller (a valve device), or the like.

[0053] The protective bearing 120 described above is also known as a "touchdown (T / D) bearing", a "backup bearing", or the like. By employing the protective bearing 120, when, for example, a problem in the electrical system or a problem such as atmospheric inrush occurs, the position and attitude of the rotor shaft 113 do not vary greatly, and as a result, the rotor blades 102 and parts on the periphery thereof are not damaged.

[0054] Note that in Fig. 1, which shows the structures of the turbo molecular pump 100 and the rotating body 103, shading indicating cross-sections of the components has been omitted to avoid complicating the drawing.<Vacuum exhaust system 10><<Basic configuration of vacuum exhaust system 10>>

[0055] Fig. 5(a) shows the vacuum exhaust system 10 according to this embodiment of the present invention. The vacuum exhaust system 10 includes a plurality of the turbo molecular pumps 100. Hereinafter, the plurality of (here, n) turbo molecular pumps 100 will be described using reference symbols "100-1" to "100-n" as appropriate. Here, "n" denotes an integer of 2 or more. This applies likewise to the "n" of chambers 12-1 to 12-n, described below.

[0056] A single dry pump 16 is connected to the individual turbo molecular pumps 100-1 to 100-n through a collecting pipe 14. The dry pump 16 functions to maintain the back pressure of the plurality of turbo molecular pumps 100-1 to 100-n and so on. A positive displacement vacuum pump or the like can be used as the dry pump 16. The collecting pipe 14 will be described below.

[0057] The vacuum exhaust system 10 is used to exhaust gas (process gas or the like) from a plurality of chambers (processing chambers) 12-1 to 12-n of a device for manufacturing a semiconductor or the like (a semiconductor, a flat panel, or the like), for example. The turbo molecular pumps 100-1 to 100-n are connected to the individual chambers 12-1 to 12-n.

[0058] For example, although not shown in the figure, a conveyance chamber and a load lock chamber can be provided on the periphery of the chambers 12-1 to 12-n. A roughing vacuum pump is connected to the conveyance chamber and the load lock chamber so that a vacuum is formed in the conveyance chamber and the load lock chamber. The load lock chamber can convey the semiconductor or the like between a vacuum space in the conveyance chamber and an atmospheric pressure region while maintaining a vacuum in the conveyance chamber. A conveyance robot is disposed in the conveyance chamber, and the conveyance robot conveys the semiconductor or the like to one of the chambers 12-1 to 12-n. The process gas or the like is supplied into each of the chambers 12-1 to 12-n.

[0059] In the example of Fig. 5(a), one of the turbo molecular pumps 100-1 to 100-n is connected to each of the individual chambers 12-1 to 12-n. However, a plurality of turbo molecular pumps may be connected to one chamber, for example. Alternatively, one turbo molecular pump may be connected to a plurality of chambers. In these cases, the "n" of the chambers 12-1 to 12-n and the "n" of the turbo molecular pumps 100-1 to 100-n do not match.

[0060] Further, when a plurality of turbo molecular pumps are connected to one chamber, it is possible, for example, to use the plurality of turbo molecular pumps simultaneously, to switch to another turbo molecular pump when one of the turbo molecular pumps breaks down, and so on.

[0061] Moreover, the turbo molecular pump 100 is cited here as an example of a usable turbo molecular pump, and either the turbo molecular pumps 100-1 to 100-n may all be identically configured turbo molecular pumps, or some or all of the turbo molecular pumps 100-1 to 100-n may have different configurations.

[0062] Furthermore, in this embodiment, as will be described below, the vacuum exhaust system 10 also has a function for controlling the introduction of gas into the chambers 12-1 to 12-n. However, the function for controlling the introduction of gas into the chambers 12-1 to 12-n may be provided in another device or system (for example, a process control system or the like). In addition, the vacuum exhaust system 10 and the other device or system may be referred to collectively as the "system", the "overall system", or the like, for example.<<Features of central exhaust type>>

[0063] Fig. 5(a) shows the central exhaust-type vacuum exhaust system 10. A distributed vacuum exhaust system 50 such as that shown in Fig. 5(b) is generally used more often, but the vacuum exhaust system 10 according to this embodiment is a central exhaust type. In comparison with the distributed exhaust-type vacuum exhaust system 50 shown in Fig. 5(b), for example, the central exhaust-type vacuum exhaust system 10 is advantaged in terms of cost, energy consumption, installation space, and so on.

[0064] More specifically, in the distributed exhaust-type vacuum exhaust system 50 shown in Fig. 5(b), dry pumps 16-1 to 16-n are connected respectively to the individual turbo molecular pumps 100-1 to 100-n. Accordingly, the number of dry pumps 16-1 to 16-n is large, leading to a corresponding increase in cost.

[0065] Moreover, a dry pump (the respective dry pumps 16-1 to 16-n or the like) normally consumes a large amount of energy, such as electrical power, and therefore, when the large number of dry pumps 16-1 to 16-n are installed, the energy consumption increases correspondingly. Furthermore, a large installation space is required to install the large number of dry pumps 16-1 to 16-n.

[0066] In contrast to these circumstances, in the central exhaust-type vacuum exhaust system 10 shown in Fig. 5(a), as described above, the single dry pump 16 is connected to the plurality of turbo molecular pumps 100-1 to 100-n through the collecting pipe 14.

[0067] The collecting pipe 14 is a pipe shaped so as to bifurcate into a plurality, and the plurality of bifurcated pipe portions (branch-side pipe portions) are connected to exhaust ports (in the example of Fig. 1, the exhaust port 15) of the turbo molecular pumps 100-1 to 100-n. A pipe portion on the side where the collecting pipe 14 is gathered is connected to an inlet port (not shown) of the dry pump 16.

[0068] Hereinafter, the pipe portions on the side where the collecting pipe 14 bifurcates will be referred to as "branch pipe portions" and denoted by reference symbols 14-1 to 14-n. The pipe portion on the side where the collecting pipe 14 is gathered will be referred to as a "gathered pipe portion" and denoted by a reference numeral 18. Note that the "n" of the branch pipe portions 14-1 to 14-n of the collecting pipe 14 does not have to match the "n" of the turbo molecular pumps 100-1 to 100-n. Further, the collecting pipe 14 may be a combination of a plurality of collecting pipes, a single pipe, and so on.

[0069] Hence, in the central exhaust-type vacuum exhaust system 10, the single dry pump 16 is assigned to the plurality of turbo molecular pumps 100-1 to 100-n so that the number of dry pumps 16 is smaller than in the distributed vacuum exhaust system 50 (Fig. 5(b)). As a result, the costs required for the dry pump 16 can be reduced. The energy consumption and installation space of the dry pump 16 are also small.

[0070] Even with the central exhaust-type vacuum exhaust system 10, however, unless measures (to be described below) such as those of this embodiment, for example, are taken, several problems occur. For example, to ensure that sufficient exhaust can be secured in relation to the plurality of chambers 12-1 to 12-n and turbo molecular pumps 100-1 to 100-n and through the long flow passage (pipe), a larger dry pump 16 (a dry pump with a higher speed or a higher exhaust speed) than the individual dry pumps 16-1 to 16-n of the distributed vacuum exhaust system 50 (Fig. 5(b)) must be used.

[0071] Further, as the turbo molecular pumps 100-1 to 100-n, it is necessary to use pumps that exhibit superior back pressure dependency so as to be able to maintain the intake pressure even when the back pressure is relatively high. Moreover, due to the need to use the collecting pipe 14, the degree of freedom in terms of pipe design is lower than in the distributed vacuum exhaust system 50 (Fig. 5(b)).

[0072] Furthermore, the inventors, when first developing the central exhaust-type vacuum exhaust system 10, implemented a design envisaging a back pressure (a turbo back pressure) in a case where the flow rates of all of the systems are simultaneously at the maximum as the back pressure of the turbo molecular pumps 100-1 to 100-n. As shown on a graph in Fig. 6, however, when the exhaust amount during an actual process was measured in relation to the individual turbo molecular pumps 100-1 to 100-n, it was found to be rare for the exhaust amount to exceed the maximum flow rate (Qmax, 3000 sccm or the like, for example) in one certain turbo molecular pump.

[0073] Here, in Fig. 6, the horizontal axis shows time and the vertical axis shows the exhaust amount for each operation of one certain turbo molecular pump (the flow rate thereof for each operation). In the example of Fig. 6, the exhaust amount increases in steps over time, reaches the maximum value (Qmax in the one certain turbo molecular pump) at an intermediate stage, and then decreases in steps. The time interval showing the maximum value is a part of the entire operation period, and in other time intervals, the operation is performed at a lower exhaust amount than the maximum value (Qmax). Note that the flow rate variation shown as an example in Fig. 6 occurs in the other turbo molecular pumps such that a value obtained by adding together the flow rates at a certain point in time serves as the overall flow rate at that point in time. The content of the flow rate variation normally differs among the plurality of turbo molecular pumps. However, the content of the flow rate variation may be common to some of the plurality of turbo molecular pumps.

[0074] On the basis of this knowledge, the inventors came up with the idea of controlling the overall flow rate of the gas flowing into the chambers 12-1 to 12-n connected to the vacuum exhaust system 10. As a result, the inventors were able to design the vacuum exhaust system 10 without pursuing an excessively low back pressure as the back pressure of the turbo molecular pumps 100-1 to 100-n.<<Basic concepts regarding adjustment of the overall flow rate and an exhaust flow rate threshold>>

[0075] Specifically, the vacuum exhaust system 10 can be controlled and operated on the basis of the following concepts (1) to (3), for example, in that order. (1) The start timing of the process (the processing) is adjusted so that the overall flow rate (Q = Q1 + Q2 + Q3 + ... + Qn; the total introduction amount, which is the sum of the amounts of gas introduced into the individual chambers) of the turbo molecular pumps 100-1 to 100-n does not exceed a threshold (an exhaust flow rate threshold). Here, Q1 to Qn are the flow rates (the total flow rate, the overall flow rate, the overall introduction amount, the total introduction amount) of the individual turbo molecular pumps 100-1 to 100-n at a certain point in time.

[0076] Normally, the process follows a time chart (a time chart of the process) prepared in advance. By referring to the time chart, the value that the overall flow rate (the total flow rate at a certain point in time) will take in several seconds, for example, can be learned. Accordingly, the expected overall flow rate up to the time at which the process has been started in each of the chambers 12-1 to 12-n is calculated, and at a timing sufficiently before the timing at which the overall flow rate exceeds the threshold, the process start timing is controlled so as not to exceed the overall flow rate. In so doing, the overall flow rate at that point in time can be kept low, and the timing at which the overall flow rate reaches the threshold can be delayed.

[0077] Note that the threshold can be determined using the maximum overall flow rate at a certain moment over the entire system, as envisaged in the design of the vacuum exhaust system 10, or the like. Alternatively, the threshold can be set aa the maximum flow rate of each chamber × the number of chambers × a coefficient (safety factor < 1) or the average flow rate of each chamber × the number of chambers × a coefficient (safety factor ≥ 1). When the process is to be started in each of the chambers 12-1 to 12-n, the process can be started at a timing at which the expected overall flow rate does not exceed the threshold on the basis of a threshold such as those described above.

[0078] (2) Further, the threshold of the overall flow rate is modified. More specifically, the vacuum performance of a chamber is typically affected by turbo deterioration and foreline deterioration. Here, the "foreline" is the pipe connecting the turbo molecular pumps 100-1 to 100-n to the dry pump 16. In the example of Fig. 5(a), the collecting pipe 14 constitutes the foreline.

[0079] Turbo deterioration occurs due to blockage of the gas flow passage or the like by deposits. Deterioration of the foreline (foreline deterioration) occurs due to pipe blockage by deposits, a reduction in the dry performance (the performance of the dry pump), and so on. Accordingly, the threshold of the overall flow rate is modified in accordance with the degree of these types of deterioration (the deterioration degree).

[0080] Further, in this embodiment, the threshold is lowered as the deterioration advances, but in cases such as when the vacuum performance is restored by so-called maintenance activities such as removing the deposits by cleaning or the like, for example, the threshold can be raised.

[0081] Furthermore, a to e and so on, for example, are used as information for evaluating the deterioration degree. a. An increase in the internal pressure (the intake pressure, the outlet port pressure, the screw inlet pressure, and so on) of the turbo molecular pump (here, the turbo molecular pumps 100-1 to 100-n). b. An increase in the motor current (here, the value of the current flowing through the motor 121). c. An increase in the output of a deposit sensor accompanying the formation of or an increase in deposits. d. The opening of an APC (Automatic Pressure Control) valve disposed in the inlet port (here, the inlet port 101) of the turbo molecular pump (here, the turbo molecular pumps 100-1 to 100-n). e. An increase in the pressure in the foreline pipe.

[0082] (3) A maintenance period is determined from variation over time in the threshold of the overall flow rate, and the maintenance period is used for preventive / predictive maintenance.<<Specific examples of overall flow rate adjustment>>

[0083] Under these concepts, the turbo molecular pumps 100-1 to 100-n, the collecting pipe 14, and the dry pump 16 are provided in the vacuum exhaust system 10 according to this embodiment, as described above. The vacuum exhaust system 10 is also provided with an exhaust system control unit 20. As shown schematically in Fig. 7, the exhaust system control unit 20 is provided with a central processing unit (CPU) 22, a storage unit 24, an input / output unit 26, and so on.

[0084] The exhaust system control unit 20 has various functions for controlling the vacuum exhaust system 10. The functions of the exhaust system control unit 20 include a function for controlling the introduction timing of the gas into the chambers 12-1 to 12-n so that the overall flow rate (Q = Q1 + Q2 + Q3 + ... + Qn; the total overall flow rate) pertaining to the turbo molecular pumps 100-1 to 100-n does not exceed a predetermined threshold (the exhaust flow rate threshold). The functions of the exhaust system control unit 20 may also include a function for controlling the flow rate at which the gas flows into the chambers 12-1 to 12-n.

[0085] Here, Q1 to Qn, as described above, are the flow rates (the total flow rate, the overall flow rate, the overall introduction amount, the total introduction amount) of the individual turbo molecular pumps 100-1 to 100-n at a certain point in time.

[0086] Note that the function for controlling the gas introduction timing and the function for controlling the flow rate may both be included but only one thereof used. Alternatively, the flow rate can be controlled after controlling the gas introduction timing (i.e., both functions can be used together).

[0087] Control of the gas introduction timing can be performed by controlling a valve device (here, chamber introduction valve devices 30-1 to 30-n) provided in a gas inlet of each chamber 12-1 to 12-n or at a prior stage to the gas inlet. In this case, the gas can be introduced by modifying the states of the chamber introduction valve devices 30-1 to 30-n through which the gas is to be introduced, among the chambers 12-1 to 12-n, from a closed state to an open state.

[0088] Further, the exhaust system control unit 20 can control the flow rate at which the gas flows into the chambers 12-1 to 12-n by adjusting the openings of the chamber introduction valve devices.

[0089] As described above, the process is performed in the chambers 12-1 to 12-n in accordance with a time chart (not shown) prepared in advance. Using timing information set on the time chart, the operation timings of the individual chamber introduction valve devices 30-1 to 30-n and information about the gas flow rates of the respective turbo molecular pumps 100-1 to 100-n can be ascertained (determined) in advance.

[0090] In the exhaust system control unit 20, for example, by calculating the overall flow rate (Q1, Q2, Q3, ..., Qn) of the gas introduced into some (or all) of the chambers 12-1 to 12-n over a period from the start of gas introduction into the individual chambers 12-1 to 12-n to a certain timing, a theoretical value of the overall flow rate (Q = Q1 + Q2 + Q3 + ... + Qn) of the gas at that point in time is calculated. The overall flow rate of the gas normally increases over time. Note that here, the gas flow rates of the turbo molecular pumps 100-1 to 100-n are described as being equal to the gas flow rates pertaining to the chambers 12-1 to 12-n.

[0091] The storage unit 24 of the exhaust system control unit 20 stores an exhaust flow rate threshold T determined in advance. At the start of an operation (the start of use) of the vacuum exhaust system 10, for example, no deposits have formed, and therefore the vacuum exhaust system 10 is in a clean state. The exhaust flow rate threshold T in this case takes an initial value of T0. The initial value T0 of the exhaust flow rate threshold T can be set at a value that the overall flow rate Q can reach at a certain point in time.

[0092] The exhaust system control unit 20 determines a timing at which the value of the overall flow rate Q calculated on the basis of the time chart reaches the exhaust flow rate threshold T. At the timing at which the value of the overall flow rate Q reaches the exhaust flow rate threshold T, the exhaust system control unit 20 selects a planned chamber (one or a plurality of the chambers 12-1 to 12-n) in which the gas flow rate is relatively large. Further, the exhaust system control unit 20 modifies control of the opening timing and / or the opening of the chamber introduction valve device 30-1 to 30-n corresponding to the selected chamber from a planned control mode.

[0093] More specifically, the exhaust system control unit 20 delays the opening timing and / or maintains (or reduces) the opening of the target chamber introduction valve device 30-1 to 30-n. Subsequently (several seconds to several tens of seconds later, for example), the exhaust system control unit 20 controls the target chamber introduction valve device 30-1 to 30-n at a planned opening timing and / or opening so as to return gas introduction control to a planned state.

[0094] By delaying the gas introduction timing or the increase timing of the selected chamber in this manner, the exhaust system control unit 20 suppresses an increase in the overall flow rate Q. Thereafter, the exhaust system control unit 20 introduces gas into the selected chamber or increases the amount of introduced gas so that a planned amount of gas is supplied to the selected chamber. Likewise at this time, the exhaust system control unit 20 controls the gas supply so as to ensure that Q ≥ T does not occur.

[0095] Here, virtual lines indicated by the reference numerals 32 and 33 in Fig. 5(a) indicate control target ranges of the exhaust system control unit 20. In the example of Fig. 5(a), one control target range 32 of the exhaust system control unit 20 includes the turbo molecular pumps 100-1 to 100-n and the dry pump 16. Further, the other control target range 33 of the exhaust system control unit 20 includes the chamber introduction valve devices 30-1 to 30-n.

[0096] In the example of Fig. 5(a), the exhaust system control unit 20 and the control target ranges 32 and 33 are depicted as being connected by a dot-dash line, thereby schematically indicating that electric (or electronic) signals (information expressed electrically (or electronically)) are transmitted and received between the exhaust system control unit 20 and the devices (including those not shown) in the control target ranges 32 and 33.

[0097] The aforementioned "system" or "overall system" includes the control target ranges 32 and 33 and peripheral devices and systems. For example, only some devices, including the turbo molecular pumps 100-1 to 100-n (or only the turbo molecular pumps 100-1 to 100-n) may be set as the direct control target range of the exhaust system control unit 20 (i.e., the constituent devices of the vacuum exhaust system 10), and other devices may be set as devices controlled by other control systems.

[0098] Note that the exhaust system control unit 20 does not necessarily have to directly control the gas supply to the chambers 12-1 to 12-n (opening / closing of the chamber introduction valve devices 30-1 to 30-n, the openings thereof, and so on). For example, when the overall flow rate Q exceeds the exhaust flow rate threshold T, the exhaust system control unit 20 may output an alarm (a warning, a notification) to the outside of the vacuum exhaust system 10.

[0099] Here, the "alarm" may be an electric (or electronic) signal (information). For example, on the basis of the output alarm, a control unit (a process control unit, not shown) of a process control system, for example, may suppress the gas supply to the chambers 12-1 to 12-n such that the overall flow rate Q does not exceed the exhaust flow rate threshold T.

[0100] Alternatively, the "alarm" can be output to a display device (not shown) such as a liquid crystal display device or a notification device (a warning device) such as a speaker (not shown), for example. In this case, an operator who perceives the content (the display content) displayed on the display device or the sound emitted from the speaker (not shown) can adjust the gas supply to the chambers 12-1 to 12-n or input an instruction into a device for adjusting the gas supply.<<Specific example of adjustment of exhaust flow rate threshold T>>

[0101] Normally, when an operation of the vacuum exhaust system 10 is started and gas is exhausted continuously from the chambers 12-1 to 12-n, deposits form, causing deterioration of the vacuum exhaust system 10 to advance. The exhaust system control unit 20 determines the degree of deterioration of the vacuum exhaust system 10 and adjusts the exhaust flow rate threshold T in accordance with the degree of deterioration.

[0102] When the deterioration has advanced to a predetermined degree, the exhaust system control unit 20 reduces the exhaust flow rate threshold T from the initial value T0 to T1, which is lower than T0. When the deterioration advances further, the exhaust flow rate threshold T is reduced from T1 to T2 (< T1). By adjusting the exhaust flow rate threshold T in this manner, the exhaust flow rate threshold T can be reduced in steps to T2, T3, T4, ... (T2 > T3 > T4 ...) in accordance with the degree of deterioration.<<Example of evaluation index (pressure)>>

[0103] Information (an evaluation index of the deterioration degree) for evaluating the degree of deterioration of the vacuum exhaust system 10 is used to adjust the exhaust flow rate threshold T. Various parameters indicating the state of vacuum exhaust can be used as the evaluation index.

[0104] For example, the internal pressure of the turbo molecular pumps 100-1 to 100-n can be used as the evaluation index. This corresponds to "a.", among the concepts "a." to "e." described above. In this case, at least one pressure, among the intake pressure, the outlet port pressure, the screw inlet pressure, and so on, of the turbo molecular pumps 100-1 to 100-n is detected.

[0105] Although not shown in the figures, in the case of the turbo molecular pump 100 shown in Fig. 1, for example, pressure detection can be performed by disposing a pressure sensor on an inner wall of the inlet port 101 or the exhaust port 15, a wall surface facing the gas inlet (the screw inlet) of the thread groove pump mechanism unit (the Holweck exhaust mechanism unit 204), or the like. Various types of sensors, including general types, can be used as the pressure sensor. Moreover, a pressure other than the intake pressure, the outlet port pressure, and the screw inlet pressure can be detected.

[0106] In the exhaust system control unit 20, the pressure (an actually measured value) is calculated on the basis of an output signal from the pressure sensor. A reference value of the pressure (a pressure reference value) is stored in the exhaust system control unit 20. The pressure reference value can be determined using a pressure value (a design value, a theoretical value) at the point serving as the start of an operation (the start of use) of the turbo molecular pump 100, for example. Alternatively, relationships between a plurality of operating conditions and a plurality of pressure reference values corresponding to the conditions can be stored in advance in the form of a table.

[0107] In the exhaust system control unit 20, the calculated pressure is compared with the pressure at the point serving as the start of an operation (the start of use) of the turbo molecular pump 100. When it is determined that the actual measured value of the pressure (the actual measured pressure value) has increased by at least a predetermined amount (or a predetermined proportion) relative to the pressure reference value, the exhaust system control unit 20 determines that deterioration has advanced beyond an allowable range and reduces the exhaust flow rate threshold T from T0 to T1.

[0108] The newly set exhaust flow rate threshold T1 is used to adjust the overall flow rate Q, as described above. For example, the exhaust system control unit 20 performs control to delay the opening timing of the chamber introduction valve devices 30-1 to 30-n and / or maintain (or reduce) the openings thereof so that the overall flow rate Q determined on the basis of the time chart does not exceed the new exhaust flow rate threshold T1.<<Alternative example of evaluation index (motor current)>>

[0109] An increase in the value of the current (the motor current) flowing through the motor 121 can also be used as the evaluation index of the degree of deterioration. This corresponds to "b.", among the concepts "a." to "e." described above. When deterioration of the vacuum exhaust system 10 advances, the value of the motor current is increased in comparison with a case where deterioration has not advanced so as to obtain the target gas flow rate and rotation speed in the turbo molecular pump 100. Hence, by monitoring the motor current, the degree of deterioration can be determined.

[0110] In this case, a relationship between the degree of deterioration and variation in the motor current is stored in advance in the form of a table so that the exhaust system control unit 20 can determine the degree of deterioration by referring to the table for the detected motor current. When the motor current has reached a predetermined value, the exhaust system control unit 20 determines that the deterioration has advanced by a predetermined degree and reduces the exhaust flow rate threshold T to T1. Note that the electromagnet current iL flowing through the electromagnet winding 151 (Fig. 2), described above, or another current detection result, for example, can be used to determine the motor current.<<Alternative example of evaluation index (amount of deposits)>>

[0111] An increase in the output of the deposit sensor accompanying the formation of or an increase in deposits can also be used as the evaluation index of the degree of deterioration. This corresponds to "c.", among the concepts "a." to "e." described above.

[0112] A location within the turbo molecular pump 100 (Fig. 1) where deposits are likely to form, for example, can be used as the location for disposing the deposit sensor. More specifically, a site in the turbo molecular pump 100 on the downstream side of the exhaust gas (process gas) can be cited. Even more specifically, an inner bottom portion of the base portion 129 and a site facing the Holweck exhaust mechanism unit 204 and the rotating body lower portion cylindrical portion 103b can be cited. Note that the deposit sensor can also be disposed in a site nearer the outlet port 133.<<Alternative example of evaluation index (APC valve openings)>>

[0113] Valve openings (APC valve openings, openings of valve bodies, valve body openings) of APC (Automatic Pressure Control) valve devices 40-1 to 40-n can also be used as the evaluation index of the degree of deterioration. This corresponds to "d.", among the concepts "a." to "e." described above.

[0114] As shown in Fig. 5(a), the APC valve devices 40-1 to 40-n are arranged so as to be connected respectively to the inlet ports (the inlet ports 101) of the turbo molecular pumps 100-1 to 100-n, and the APC valve devices 40-1 to 40-n control the flow rate of the gas flowing into the turbo molecular pumps 100-1 to 100-n.

[0115] When the amount of deposits in one of the turbo molecular pumps 100-1 to 100-n increases such that the gas flow rate decreases, control is performed to automatically increase the opening of the corresponding APC valve device, among the APC valve devices 40-1 to 40-n, so that the flow rate of the gas supplied to the corresponding turbo molecular pump increases, and as a result, the gas flow rate is maintained. It can be determined that the gas flow rate has decreased when an average value of the openings of the plurality of APC valve devices or the opening of a specific (one, for example) APC valve device increases beyond a planned value, or the like.

[0116] Thus, the openings of the APC valves vary in accordance with (in response to) variation (a reduction) in the gas flow rates of the turbo molecular pumps 100-1 to 100-n. Therefore, by monitoring the APC valve openings, for example, the exhaust system control unit 20 can determine the degree of deterioration in accordance with the APC valve openings.<<Example of evaluation index (increase in foreline pressure)>>

[0117] An increase in pressure in the foreline pipe can also be used as the evaluation index of the degree of deterioration. This corresponds to "e.", among the concepts "a." to "e." described above. In the example of Fig. 5(a), the branch pipe portions 14-1 to 14-n or the gathered pipe portion 18 of the collecting pipe 14 can be used as the foreline.

[0118] In the example of Fig. 5(a), pressure gauges 44-1 to 44-n and 48 are disposed in the branch pipe portions 14-1 to 14-n and the gathered pipe portion 18. The values of output signals from the pressure gauges 44-1 to 44-n and 48 vary in accordance with the pressure of the gas flowing through the branch pipe portions 14-1 to 14-n and the gathered pipe portion 18. Although not shown in the figures, the output signals of the pressure gauges 44-1 to 44-n and 38 are input into the exhaust system control unit 20. The exhaust system control unit 20 compares the detected pressure with a correct pressure stored in advance, and when the pressure has increased beyond a reference value (a pressure threshold), the exhaust system control unit 20 outputs an alarm (a warning, a notification) to the outside, for example, indicating an abnormality in the vacuum exhaust system 10 and the need for maintenance.<<Maintenance alarm>>

[0119] The exhaust system control unit 20 outputs an alarm to the outside when the amount by which the adjusted exhaust flow rate threshold T has been reduced reaches a predetermined amount. More specifically, the exhaust system control unit 20 determines whether or not the exhaust flow rate threshold T has fallen to or below a predetermined value, and when the exhaust flow rate threshold T has fallen to or below the predetermined value, outputs an alarm (a warning, a notification) to the outside of the vacuum exhaust system 10.

[0120] Here, the "alarm" may be an electric (or electronic) signal (information). For example, a cleaning device (a plasma cleaning device or the like, for example; not shown) may be connected to the turbo molecular pump 100, and on the basis of the output alarm, the normal operation of the turbo molecular pump 100 can be stopped and the cleaning device operated.

[0121] Alternatively, the "alarm" can be output to the aforementioned display device, such as a liquid crystal display device, or notification device (warning device), such as a speaker. In this case, the operator who perceives the display content or the sound can operate the cleaning device connected to the turbo molecular pumps 100-1 to 100-n or remove the turbo molecular pumps 100-1 to 100-n from the vacuum exhaust system 10 and clean the turbo molecular pumps 100-1 to 100-n.<Advantages of invention according to this embodiment>>

[0122] With the vacuum exhaust system 10 according to this embodiment, as described above, at least one of the introduction timing and the flow rate of the gas is controlled by a gas introduction amount control means so that the overall flow rate Q of the turbo molecular pumps 100-1 to 100-n does not exceed the exhaust flow rate threshold T. As a result, the overall flow rate at that point in time can be kept low. Moreover, the timing at which the overall flow rate reaches the threshold can be delayed.

[0123] Hence, there is no need to increase the size of the dry pump 16, use piping with low conductance, or employ a turbo molecular pump exhibiting superior back pressure dependency. As a result, it is possible to provide the vacuum exhaust system 10, with which reductions in the cost and size of the exhaust system and / or an increase in the degree of freedom pertaining to the piping design can be achieved, and a vacuum pump (the turbo molecular pumps 100-1 to 100-n) that can be used in the vacuum exhaust system.

[0124] Furthermore, with the vacuum exhaust system 10 according to this embodiment, the exhaust flow rate threshold T is adjusted on the basis of signals pertaining to the following states. a. An increase in the internal pressure (the intake pressure, the outlet port pressure, the screw inlet, and so on) of the turbo molecular pump (here, the turbo molecular pumps 100-1 to 100-n). b. An increase in the motor current (here, the value of the current flowing through the motor 121). c. An increase in the output of the deposit sensor accompanying the formation of or an increase in deposits. d. The opening of the APC (Automatic Pressure Control) valve disposed in the inlet port (here, the inlet port 101) of the turbo molecular pump (here, the turbo molecular pumps 100-1 to 100-n). e. An increase in the pressure in the foreline pipe.

[0125] Therefore, the exhaust flow rate threshold T can be adjusted on the basis of detection of the degree of deterioration in locations in and around the vacuum exhaust system 10. As a result, the exhaust flow rate threshold T can be set appropriately each time in accordance with the degree of deterioration.

[0126] Note that "a." to "c." above may be said to be items (also referred to as "parameters" or the like) indicating degrees of deterioration in the turbo molecular pumps 100-1 to 100-n, while "d." and "e." may be said to be items indicating degrees of deterioration outside the turbo molecular pumps 100-1 to 100-n.

[0127] Further, "a." to "c." may be said to be items pertaining to detection performed by the vacuum exhaust system 10, while "d." and "e." can be included in items pertaining to detection performed by the vacuum exhaust system 10 or items pertaining to detection performed outside the vacuum exhaust system 10.

[0128] Furthermore, with the vacuum exhaust system 10 according to this embodiment, an alarm is output to the outside when the overall flow rate Q exceeds the exhaust flow rate threshold T (when it is determined that the overall flow rate Q will exceed the exhaust flow rate threshold T thereafter). The "alarm" is a concept including the transmission of an electric (or electronic) signal or information. Accordingly, measures based on the "alarm" can be taken. The measures include various operations and control (including control performed either manually or automatically) for ensuring that the overall flow rate Q does not actually exceed the exhaust flow rate threshold T.

[0129] Moreover, with the vacuum exhaust system 10 according to this embodiment, the exhaust flow rate threshold T is successively adjusted so that the exhaust flow rate threshold T varies over time (varies in time series order). When the amount of reduction (T-T1, T1-T2, T2-T3, ..., T-T2, T-T3, ..., and so on) in the exhaust flow rate threshold T reaches a predetermined amount, an alarm is output to the outside. This "alarm" is also a concept including the transmission of an electric (or electronic) signal or information. Accordingly, measures based on the "alarm" can be taken.

[0130] The measures include maintenance activities for removing the cause of the advance of the deterioration. The measures also include determining a maintenance timing, preventing the deterioration, recognizing signs of deterioration, and so on. Furthermore, by taking these measures, the exhaust flow rate threshold T can be increased (returned to normal, for example) or the like when the vacuum performance recovers or the like.

[0131] Note that a gas introduction amount acquiring means for acquiring the gas introduction amount may be provided. Acquiring the gas introduction amount includes acquiring a signal indicating the gas introduction amount, acquiring a signal (information) indicating variation in the gas introduction amount under fixed conditions, and so on.

[0132] The gas introduction amount acquiring means includes a means (a gas introduction amount sensor) for detecting the amount of gas flowing into or passing through and / or the amount of gas flowing out of the chambers 12-1 to 12-n, and a means for calculating or acquiring information about the overall flow rate (the individual introduction amounts, an overall introduction amount obtained by adding together the individual introduction amounts, or the like) from the information (the detection result) indicating the detected gas flow rate. The exhaust system control unit 20, for example, can be used as the means for calculating or acquiring information about the various introduction amounts.

[0133] Furthermore, the turbo molecular pumps 100-1 to 100-n used in the vacuum exhaust system 10 described above are used to construct the vacuum exhaust system 10.<Inventions that can be extracted from the embodiments>

[0134] (1) A vacuum exhaust system (the vacuum exhaust system 10 or the like) for exhausting a processing gas (the process gas or the like) from a plurality of processing chambers (the chambers 12-1 to 12-n or the like), the vacuum exhaust system including: a plurality of first vacuum pumps (the turbo molecular pumps 100-1 to 100-n or the like); a collecting pipe (the collecting pipe 14 or the like) to which outlet ports (the outlet ports 133 or the like) of the plurality of first vacuum pumps are connected in parallel; one or more second vacuum pumps (the dry pump 16 or the like) connected to the collecting pipe; and a gas introduction amount control means (the exhaust system control unit 20, the chamber introduction valve devices 30-1 to 30-n, or the like) for controlling a flow rate of the gas (the amount or gas per unit time or the like) introduced into the plurality of processing chambers, wherein an exhaust flow rate threshold (T0 pertaining to the exhaust flow rate threshold T, or the like) of the processing gas is set on the basis of a flow rate that can be exhausted by the plurality of first vacuum pumps, and at least one of an introduction timing (the opening timing of a chamber introduction valve device selected from the chamber introduction valve devices 30-1 to 30-n, or the like) and the flow rate (a flow rate corresponding to the opening of the chamber introduction valve device, or the like) of the gas is controlled by the gas introduction amount control means so as not to exceed the exhaust flow rate threshold. (2) The vacuum exhaust system described above in (1), further including: a first vacuum pump state information acquiring means (a pressure sensor, the motor 121, the deposit sensor 34, the APC valve devices 40-1 to 40-n, the pressure gauges 44-1 to 44-n and 48, or the like) for acquiring first vacuum pump state information (a signal indicating the internal pressure of the turbo molecular pumps 100-1 to 100-n, a signal indicating the magnitude of the current of the motor 121, an output signal from the deposit sensor 34, signals indicating the openings of the APC valve devices 40-1 to 40-n, output signals from the pressure gauges 44-1 to 44-n and 48, or the like), which is information indicating states of the plurality of first vacuum pumps, wherein the exhaust flow rate threshold is adjusted (modified in the exhaust system control unit 20, a process control unit, or the like upon reception of the various signals, or the like) in accordance with a signal from the first vacuum pump state information acquiring means. (3) The vacuum exhaust system described above in (2), wherein the first vacuum pump state information includes information indicating a pressure state in an interior of the first vacuum pump. (4) The vacuum exhaust system described above in (1), further including: a pressure adjustment valve (the valve bodies of the APC valve devices 40-1 to 40-n, or the like) disposed on an upstream side of the plurality of first vacuum pumps in order to adjust pressure of the plurality of processing chambers; and a valve signal acquiring means (the APC valve devices 40-1 to 40-n or the like) for acquiring state information (signals indicating the valve openings, information indicating the valve openings, or the like) about the pressure adjustment valve, wherein the exhaust flow rate threshold is adjusted (modified in the exhaust system control unit 20 upon reception of signals from the APC valve devices 40-1 to 40-n, or the like) in accordance with a signal from the valve signal acquiring means. (5) The vacuum exhaust system described above in (1), further including: a second pressure signal acquiring means (the pressure gauges 44-1 to 44-n, or the like) for acquiring pressure information relating to an interior of the collecting pipe, wherein the exhaust flow rate threshold is adjusted (modified in the exhaust system control unit 20 upon reception of signals from the pressure gauges 44-1 to 44-n, or the like) in accordance with a signal from the second pressure signal acquiring means. (6) The vacuum exhaust system described above in any one of (1) to (5), wherein an alarm is output to outside (a signal or information that can be used to issue a warning or a notification relating to adjustment of the exhaust flow rate threshold T is output from the exhaust system control unit 20, or the like) when the exhaust flow rate threshold is exceeded. (7) The vacuum exhaust system described above in any one of (1) to (5), wherein an alarm is output to outside (a signal or information that can be used to issue a warning or a notification relating to maintenance of the system is output from the exhaust system control unit 20, or the like) when an amount of reduction in the adjusted exhaust flow rate threshold reaches a predetermined amount. (8) The vacuum exhaust system described above in any one of (1) to (5), further including: a gas introduction amount acquiring means (a gas introduction amount sensor, a means (the exhaust system control unit 20 or another control unit) for calculating or acquiring information about the overall flow rate from a detection result of the gas flow rate, acquired by the gas introduction amount sensor, or the like) for acquiring an introduction amount of the gas introduced into the plurality of processing chambers, wherein at least one of the introduction timing and the flow rate of the gas is controlled by the gas introduction amount control means so that the introduction amount of the gas, acquired by the gas introduction amount acquiring means, does not exceed the exhaust flow rate threshold. (9) A vacuum pump used in a vacuum exhaust system (the vacuum exhaust system 10 or the like) for exhausting a processing gas (the process gas or the like) from a plurality of processing chambers (the chambers 12-1 to 12-n or the like), the vacuum exhaust system including: a plurality of first vacuum pumps (the turbo molecular pumps 100-1 to 100-n or the like); a collecting pipe (the collecting pipe 14 or the like) to which outlet ports (the outlet ports 133 or the like) of the plurality of first vacuum pumps are connected in parallel; one or more second vacuum pumps (the dry pump 16 or the like) connected to the collecting pipe; and a gas introduction amount control means (the exhaust system control unit 20, the chamber introduction valve devices 30-1 to 30-n, or the like) for controlling a flow rate of a gas (the amount or gas per unit time or the like) introduced into the plurality of processing chambers, wherein an exhaust flow rate threshold (T0 pertaining to the exhaust flow rate threshold T, or the like) of the processing gas is set on the basis of a flow rate that can be exhausted by the plurality of first vacuum pumps, at least one of an introduction timing (the opening timing of a chamber introduction valve device selected from the chamber introduction valve devices 30-1 to 30-n, or the like) and the flow rate (a flow rate corresponding to the opening of the chamber introduction valve device, or the like) of the gas is controlled by the gas introduction amount control means so as not to exceed the exhaust flow rate threshold, and the vacuum pump is used as the first vacuum pumps provided in the vacuum exhaust system. <Miscellaneous>

[0135] Note that the present invention is not limited to the embodiments described above, and the embodiments may be amended or combined in various ways within a scope that does not depart from the spirit of the invention.[Reference Signs List]

[0136] 10 Vacuum exhaust system 12-1 to 12-n Chamber 14 Collecting pipe 14-1 to 14-n Branch pipe portions 15 Exhaust port 16 Dry pump 18 Gathered pipe portion 20 Exhaust system control unit 30-1 to 30-n Chamber introduction valve device 34 Deposit sensor 40-1 to 40-n APC valve device 44-1 to 44-n Pressure gauge 100, 100-1 to 100-n Turbo molecular pump 101 Intake port 121 Motor 133 Outlet port

Claims

1. A vacuum exhaust system for exhausting a processing gas from a plurality of processing chambers, the vacuum exhaust system comprising: a plurality of first vacuum pumps; a collecting pipe to which outlet ports of the plurality of first vacuum pumps are connected in parallel; one or more second vacuum pumps connected to the collecting pipe; and a gas introduction amount control means for controlling a flow rate of a gas introduced into the plurality of processing chambers, wherein an exhaust flow rate threshold of the processing gas is set on the basis of a flow rate that can be exhausted by the plurality of first vacuum pumps, and at least one of an introduction timing and the flow rate of the gas is controlled by the gas introduction amount control means so as not to exceed the exhaust flow rate threshold.

2. The vacuum exhaust system according to claim 1, further comprising: a first vacuum pump state information acquiring means for acquiring first vacuum pump state information, which is information indicating states of the plurality of first vacuum pumps, wherein the exhaust flow rate threshold is adjusted in accordance with the first vacuum pump state information.

3. The vacuum exhaust system according to claim 2, wherein the first vacuum pump state information includes information indicating a pressure state in an interior of the first vacuum pump.

4. The vacuum exhaust system according to claim 1, further comprising: a pressure adjustment valve disposed on an upstream side of the plurality of first vacuum pumps in order to adjust pressure of the plurality of processing chambers; and a valve signal acquiring means for acquiring state information about the pressure adjustment valve, wherein the exhaust flow rate threshold is adjusted in accordance with a signal from the valve signal acquiring means.

5. The vacuum exhaust system according to claim 1, further comprising: a second pressure signal acquiring means for acquiring pressure information relating to an interior of the collecting pipe, wherein the exhaust flow rate threshold is adjusted in accordance with a signal from the second pressure signal acquiring means.

6. The vacuum exhaust system according to any one of claims 1 to 5, wherein an alarm is output to outside when the exhaust flow rate threshold is exceeded.

7. The vacuum exhaust system according to any one of claims 1 to 5, wherein an alarm is output to outside when an amount of reduction in the adjusted exhaust flow rate threshold reaches a predetermined amount.

8. The vacuum exhaust system according to any one of claims 1 to 5, further comprising: a gas introduction amount acquiring means for acquiring an introduction amount of the gas introduced into the plurality of processing chambers, wherein at least one of the introduction timing and the flow rate of the gas is controlled by the gas introduction amount control means so that the introduction amount of the gas, acquired by the gas introduction amount acquiring means, does not exceed the exhaust flow rate threshold.

9. A vacuum pump used in a vacuum exhaust system for exhausting a processing gas from a plurality of processing chambers, the vacuum exhaust system comprising: a plurality of first vacuum pumps; a collecting pipe to which outlet ports of the plurality of first vacuum pumps are connected in parallel; one or more second vacuum pumps connected to the collecting pipe; and a gas introduction amount control means for controlling a flow rate of a gas introduced into the plurality of processing chambers, wherein an exhaust flow rate threshold of the processing gas is set on the basis of a flow rate that can be exhausted by the plurality of first vacuum pumps, at least one of an introduction timing and the flow rate of the gas is controlled by the gas introduction amount control means so as not to exceed the exhaust flow rate threshold, and the vacuum pump is used as the first vacuum pumps provided in the vacuum exhaust system.

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