Vacuum exhaust system

Abstract

To provide a vacuum exhaust device excellent in characteristics related to cleaning of deposits.SOLUTION: This device is provided with a pressure vessel side 100B, a rotor lower cylindrical part side 100B rotatably held in the pressure vessel side 103b, and a screw stator 131 arranged opposite to the rotor lower cylindrical part side 100B through an outside discharge gap part 264 in the pressure vessel side 103b, and a voltage can be applied to the screw stator 131. A projection part 103b continuing at a prescribed angle in the circumferential direction is arranged in at least a part of an opposed surface of the rotary body lower part cylindrical part 131b and the screw stator 131, and constitutes a drag pump part. An 131b of the projection part is formed in a tapered shape narrowing toward the tip side.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a vacuum evacuation device using a vacuum pump such as a turbo molecular pump, for example.

Background Art

[0002] Generally, a turbo molecular pump is known as a kind of vacuum pump. This turbo molecular pump is used, for example, for evacuation in manufacturing apparatuses such as semiconductor and flat panel manufacturing apparatuses. In a turbo molecular pump, by energizing a motor in the pump body, a rotating blade is rotated, and gas (process gas) is exhausted by bouncing off gas molecules (gas molecules) of the gas sucked into the pump body. Further, such a turbo molecular pump includes a type provided with a heater and a cooling pipe in order to appropriately control the temperature inside the pump.

[0003] In a vacuum pump used for evacuation of manufacturing apparatuses such as semiconductors and flat panels, reaction products generated in the manufacturing process of semiconductors and flat panels may accumulate inside the vacuum pump. As a countermeasure, a technique has been devised in which a plasma generation device is installed in the vacuum pump and the inside is plasma-cleaned.

[0004] In the invention disclosed in Patent Document 1 (listed below), a plasma introduction port (radical supply port 201a) is provided in the casing (outer cylinder 127) of a vacuum pump, and a plasma generator (radical supply means 201) is connected thereto. Radicals introduced into the casing flow circumferentially through an annular passage (annular groove) formed between the inner wall of the casing and the outer wall of the exhaust mechanism. Subsequently, radicals are introduced into the exhaust mechanism through a communication port provided in the spacer (fixed blade spacer 125) that holds the fixed blade (fixed blade 123). Since this communication port is provided so as to face (facing) the space secured by widening the distance between the rotating blade (rotating blade 102) and the fixed blade in the direction of the rotation axis, the larger the communication port (diameter and opening area), the wider the distance between the rotating blade and the fixed blade becomes, and the lower the pump performance. For this reason, the size of the communication port has been kept to the minimum necessary, and multiple communication ports and plasma generators (radical supply means 201) have been provided in the circumferential direction. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-017864 [Overview of the project] [Problems that the invention aims to solve]

[0006] The radicals used in plasma cleaning are substances forcibly dissociated by applying high energy within a plasma generator. Therefore, the radicals have a short lifespan, and it was sometimes impossible to supply them to areas far from the plasma generator. Furthermore, in order to supply radicals uniformly at a similar concentration throughout the entire pump, it was necessary to arrange multiple plasma generators circumferentially. Additionally, while radicals among the reactive species that make up the plasma could be utilized, ions could not, sometimes resulting in insufficient cleaning speed.

[0007] When multiple plasma generators are arranged in a circular direction, (1) the cost is higher due to the multiple plasma generators. Also, (2) piping for supplying raw material gas (also called "fuel gas") and cooling water, and wiring for supplying power are required for each plasma generator, which can make the design and installation complex and restrict the placement location.

[0008] The object of the present invention is to provide a vacuum exhaust device with excellent properties for cleaning sediments. [Means for solving the problem]

[0009] To achieve the above objective, the vacuum exhaust system according to the present invention pressure vessel and A rotor portion is rotatably held within the pressure vessel, A first stator section is disposed within the pressure vessel, facing the rotor section via a discharge gap section, A vacuum evacuation device equipped with, Voltage can be applied to the first stator section. It is characterized by the following: [Effects of the Invention]

[0010] According to the above invention, it is possible to provide a vacuum exhaust device with excellent characteristics related to the cleaning of sediment. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram illustrating the configuration of a vacuum exhaust device according to the first embodiment of the present invention. [Figure 2] This is a circuit diagram of an amplifier. [Figure 3] This is a time chart showing the control when the current command value is greater than the detected value. [Figure 4] This is a timing chart showing the control when the current command value is smaller than the detected value. [Figure 5](a) is an enlarged view of the portion surrounded by frame A in FIG. 1, and (b) is an enlarged view of the portion surrounded by frame B in (a). [Figure 6] It is an explanatory diagram schematically showing the configuration of a vacuum evacuation device according to a second embodiment. [Figure 7] (a) is an enlarged view of the portion surrounded by frame A in FIG. 6, and (b) is an enlarged view of the portion surrounded by frame B in (a). [Figure 8] It is an explanatory diagram schematically showing the configuration of a vacuum evacuation device according to a third embodiment. [Figure 9] (a) is an enlarged view of the portion surrounded by frame A in FIG. 8, and (b) is an enlarged view of the portion surrounded by frame B in (a). [Figure 10] (a) is an explanatory diagram showing a longitudinal section of a turbo molecular pump according to a conventional example, and (b) is an explanatory diagram showing a cross section of the connection portion between the introduction pipe (216) and the outer cylinder (127).

Embodiments for Carrying Out the Invention

[0012] <Basic Configuration of Vacuum Evacuation Device 100A According to the First Embodiment> FIG. 1 shows a vacuum evacuation device 100A according to the first embodiment of the present invention. The vacuum evacuation device 100A includes a vacuum pump (here, a turbo molecular pump 100). This turbo molecular pump 100 is connected to a vacuum chamber (not shown) of a target device such as a semiconductor manufacturing device, for example.

[0013] A longitudinal sectional view of this turbo molecular pump 100 is shown in FIG. 1. In FIG. 1, in the turbo molecular pump 100, an intake port 101 is formed at the upper end of a cylindrical outer cylinder 127. And inside the outer cylinder 127, a rotating body 103 is provided with a plurality of rotating blades 102 (102a, 102b, 102c ···), which are turbine blades for sucking and exhausting gas, formed radially and in multiple stages on the circumference. A rotor shaft 113 is attached to the center of this rotating body 103, and this rotor shaft 113 is levitated and position-controlled in the air by, for example, a magnetic bearing with 5-axis control.

[0014] The upper radial electromagnet 104 has four electromagnets arranged in pairs with respect to the X-axis and the Y-axis. Four upper radial sensors 107 are provided in proximity to the upper radial electromagnet 104 and corresponding to each of the upper radial electromagnets 104. The upper radial sensor 107 uses, for example, an inductance sensor having a conductive winding or an eddy current sensor, etc., and detects the position of the rotor shaft 113 based on the change in the inductance of this conductive winding that changes according to the position of the rotor shaft 113. This upper radial sensor 107 is configured to detect the radial displacement of the rotor shaft 113, that is, the rotating body 103 fixed thereto, and send it to the control device 200.

[0015] In this control device 200, for example, a compensation circuit having a PID adjustment function generates an excitation control command signal for the upper radial electromagnet 104 based on the position signal detected by the upper radial sensor 107, and the amplifier circuit 150 (described later in FIG. 2) controls the excitation of the upper radial electromagnet 104 based on this excitation control command signal, thereby adjusting the radial position above the rotor shaft 113.

[0016] And this rotor shaft 113 is formed of a high magnetic permeability material (such as iron, stainless steel, etc.), and is attracted by the magnetic force of the upper radial electromagnet 104. Such adjustment is performed independently in the X-axis direction and the Y-axis direction respectively. Also, the lower radial electromagnet 105 and the lower radial sensor 108 are arranged in the same manner as the upper radial electromagnet 104 and the upper radial sensor 107, and the radial position below the rotor shaft 113 is adjusted in the same manner as the radial position above.

[0017] Furthermore, the axial electromagnets 106A, 106B are arranged sandwiching a disc-shaped metal disk (also referred to as an "armature disk") 111 provided at the lower part of the rotor shaft 113 from above and below. The metal disk 111 is made of a high magnetic permeability material such as iron. An axial sensor 109 is provided to detect the axial displacement of the rotor shaft 113, and its axial position signal is configured to be sent to the control device 200.

[0018] Then, in the control device 200, for example, a compensation circuit having a PID adjustment function generates excitation control command signals for the axial electromagnets 106A and 106B based on the axial position signal detected by the axial sensor 109, and the amplifier circuit 150 excites the axial electromagnets 106A and 106B based on these excitation control command signals, so that the axial electromagnet 106A attracts the metal disk 111 upward with magnetic force, and the axial electromagnet 106B attracts the metal disk 111 downward, thereby adjusting the axial position of the rotor shaft 113.

[0019] Thus, the control device 200 appropriately adjusts the magnetic force exerted by the axial electromagnets 106A and 106B on the metal disk 111, causing the rotor shaft 113 to levitate axially and be held in contact with space. The amplifier circuit 150 that excites and controls the upper radial electromagnet 104, the lower radial electromagnet 105, and the axial electromagnets 106A and 106B will be described later.

[0020] On the other hand, the motor 121 is equipped with multiple magnetic poles arranged circumferentially around the rotor shaft 113. Each magnetic pole is controlled by the control device 200 to rotate the rotor shaft 113 via the electromagnetic force acting between it and the rotor shaft 113. The motor 121 also incorporates a rotational speed sensor, such as a Hall element, resolver, or encoder (not shown), and the rotational speed of the rotor shaft 113 is detected by the detection signal from this rotational speed sensor.

[0021] Furthermore, for example, a phase sensor (not shown) is attached near the lower radial sensor 108 to detect the phase of rotation of the rotor shaft 113. The control device 200 uses both the detection signals from this phase sensor and the rotational speed sensor to detect the position of the magnetic pole.

[0022] Multiple fixed blades 123 (123a, 123b, 123c...) are arranged with a small gap (a predetermined interval) between them and the rotating blades 102 (102a, 102b, 102c...). Each of the rotating blades 102 (102a, 102b, 102c...) is formed at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113 in order to transport exhaust gas molecules downward by collision.

[0023] Similarly, the fixed wing 123 is formed at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113, and is arranged alternately with the stages of the rotor blade 102 toward the inside of the outer cylinder 127. The outer edge of the fixed wing 123 is supported by being fitted between a plurality of stacked fixed wing spacers 125 (125a, 125b, 125c, etc.).

[0024] The fixed-wing spacer 125 is a ring-shaped member and is made of a metal such as aluminum, iron, stainless steel, or copper, or an alloy containing these metals as components. An outer cylinder 127 is fixed to the outer circumference of the fixed-wing spacer 125 with a small gap in between. A base portion 129 is provided at the bottom of the outer cylinder 127. An exhaust port 133 is formed in the base portion 129 and communicates with the outside. Exhaust gas that enters the intake port 101 from the chamber (vacuum chamber) side and is transferred to the base portion 129 is sent to the exhaust port 133.

[0025] Furthermore, depending on the application of the turbomolecular pump 100, a screw stator 131 is provided inside the base portion 129. The screw stator 131 is a cylindrical member made of a metal such as aluminum, copper, stainless steel, iron, or an alloy containing these metals, and has multiple helical screw grooves 131a engraved on its inner circumferential surface. The direction of the helix of the screw grooves 131a is such that when exhaust gas molecules move in the direction of rotation of the rotating body 103, these molecules are transported toward the exhaust port 133. A lower cylindrical portion 103b of the rotating body hangs down from the lower part of the rotating body body 103a on which the rotating blades 102 (102a, 102b, 102c...) of the rotating body 103 are formed. The outer circumferential surface of this lower cylindrical portion 103b is cylindrical and protrudes toward the inner circumferential surface of the screw stator 131, and is in close proximity to the inner circumferential surface of the screw stator 131 with a predetermined gap between them. The exhaust gas, which has been transferred to the screw groove 131a by the rotating blades 102 and fixed blades 123, is guided along the screw groove 131a and sent to the base section 129. In this way, the screw stator 131 and the lower cylindrical section 103b of the rotating body opposite it constitute the Holbeck-type exhaust mechanism 204. The Holbeck-type exhaust mechanism 204 improves the exhaust characteristics of the turbomolecular pump 100 by giving direction to the exhaust gas through the rotation of the lower cylindrical section 103b of the rotating body relative to the screw stator 131.

[0026] The base portion 129 is a disc-shaped member that constitutes the base of the turbomolecular pump 100, and is generally made of a metal such as iron, aluminum, or stainless steel. The base portion 129 not only physically holds the turbomolecular pump 100 but also functions as a heat conduction path, so it is desirable to use a metal that is rigid and has high thermal conductivity, such as iron, aluminum, or copper. In this embodiment, the aforementioned screw stator 131, base portion 129, and lower cylindrical portion 103b of the rotating body constitute the plasma generation unit 210, but the specific configuration of the plasma generation unit 210 will be described later.

[0027] In the configuration of the turbomolecular pump 100, when the rotor blades 102 are rotated together with the rotor shaft 113 by the motor 121, exhaust gas is drawn in from the chamber through the intake port 101 by the action of the rotor blades 102 and the fixed blades 123. The exhaust gas drawn in from the intake port 101 passes between the rotor blades 102 and the fixed blades 123 and is transferred to the base section 129. At this time, the temperature of the rotor blades 102 rises due to frictional heat generated when the exhaust gas comes into contact with the rotor blades 102 and heat conduction generated by the motor 121, but this heat is transferred to the fixed blades 123 side by radiation or conduction by gas molecules of the exhaust gas.

[0028] The fixed-wing spacers 125 are joined to each other at their outer circumference, and they transmit heat received by the fixed wing 123 from the rotor blade 102, as well as frictional heat generated when exhaust gases come into contact with the fixed wing 123, to the outside.

[0029] In the above description, the screw stator 131 is arranged on the outer circumference of the lower cylindrical portion 103b of the rotating body 103, and screw grooves 131a are engraved on the inner surface of the screw stator 131. However, conversely, there are also cases where screw grooves are engraved on the outer circumference of the lower cylindrical portion 103b of the rotating body, and a spacer having a cylindrical inner surface is arranged around it.

[0030] Furthermore, depending on the application of the turbomolecular pump 100, the electrical components, which consist of an upper radial electromagnet 104, an upper radial sensor 107, a motor 121, a lower radial electromagnet 105, a lower radial sensor 108, axial electromagnets 106A, 106B, and an axial sensor 109, may be covered by a stator column 122 to prevent the gas drawn in from the intake port 101 from entering the electrical components, and the inside of this stator column 122 may be maintained at a predetermined pressure with purge gas.

[0031] In this case, a purge gas port 132 is provided in the base section 129, and purge gas is introduced through this piping. The introduced purge gas is sent to the exhaust port 133 through the gap 134 between the protective bearing 120 and the rotor shaft 113, between the rotor and stator of the motor 121, and between the inner cylindrical part of the rotor blade 102 (lower cylindrical part 103b of the rotating body) and the stator column 122 or base section 129.

[0032] Here, the turbomolecular pump 100 requires model identification and control based on individually adjusted unique parameters (e.g., characteristics corresponding to the model). To store these control parameters, the turbomolecular pump 100 is equipped with an electronic circuit section 141 within its body. The electronic circuit section 141 consists of electronic components such as semiconductor memory such as EEP-ROM and semiconductor elements for accessing it, and a substrate 143 for mounting them. This electronic circuit section 141 is housed, for example, below a rotational speed sensor (not shown) near the center of the base section 129 that constitutes the lower part of the turbomolecular pump 100, and is closed by an airtight bottom cover 145.

[0033] Incidentally, in the semiconductor manufacturing process, some process gases introduced into the chamber have the property of becoming solid when their pressure exceeds a predetermined value or their temperature falls below a predetermined value. Inside the turbomolecular pump 100, the exhaust gas pressure is lowest at the intake port 101 and highest at the exhaust port 133. If the process gas pressure exceeds a predetermined value or its temperature falls below a predetermined value while it is being transferred from the intake port 101 to the exhaust port 133, the process gas becomes solid and adheres to and accumulates inside the turbomolecular pump 100.

[0034] For example, if SiCl4 is used as the process gas in an Al etching apparatus, the low vacuum (760 [torr] ~ 10 -2The vapor pressure curve shows that when the pressure is low (torr) and the temperature is low (approximately 20°C), solid products (e.g., AlCl3) precipitate and adhere to the inside of the turbomolecular pump 100. As a result, when process gas precipitates accumulate inside the turbomolecular pump 100, these deposits narrow the pump flow path, causing a decrease in the performance of the turbomolecular pump 100. Furthermore, the aforementioned products were prone to solidifying and adhering in areas of high pressure, such as near the exhaust port 133 and near the screw stator 131.

[0035] Therefore, in order to solve this problem, conventionally, a heater (not shown) or an annular water cooling pipe 149 is wrapped around the outer circumference of the base portion 129, and a temperature sensor (e.g., a thermistor) (not shown) is embedded in the base portion 129, and the heating of the heater and the cooling of the water cooling pipe 149 are controlled (hereinafter referred to as TMS; Temperature Management System) based on the signal from this temperature sensor to maintain the temperature of the base portion 129 at a constant high temperature (set temperature). In this embodiment, the screw stator 131 is heated by a heater (not shown) embedded in the screw stator 131, and the base portion 129 is cooled by a water cooling pipe 149 embedded in the bottom cover 145.

[0036] Next, we will describe an amplifier circuit 150 that energizes and controls the upper radial electromagnet 104, the lower radial electromagnet 105, and the axial electromagnets 106A and 106B of the turbomolecular pump 100 configured in this way. The circuit diagram of this amplifier circuit is shown in Figure 2.

[0037] In Figure 2, the electromagnet winding 151, which constitutes the upper radial electromagnet 104, has one end connected to the positive terminal 171a of the power supply 171 via transistor 161, and the other end connected to the negative terminal 171b of the power supply 171 via current detection circuit 181 and transistor 162. Transistors 161 and 162 are so-called power MOSFETs, and have a structure in which a diode is connected between their source and drain.

[0038] In this configuration, transistor 161 has its diode cathode terminal 161a connected to the positive terminal 171a, and its anode terminal 161b connected to one end of the electromagnet winding 151. Transistor 162 has its diode cathode terminal 162a connected to the current detection circuit 181, and its anode terminal 162b connected to the negative terminal 171b.

[0039] On the other hand, the diode 165 for current regeneration has its cathode terminal 165a connected to one end of the electromagnet winding 151, and its anode terminal 165b connected to the negative terminal 171b. Similarly, the diode 166 for current regeneration has its cathode terminal 166a connected to the positive terminal 171a, and its anode terminal 166b connected to the other end of the electromagnet winding 151 via the current detection circuit 181. The current detection circuit 181 is composed of, for example, a Hall sensor type current sensor or an electrical resistance element.

[0040] The amplifier circuit 150 configured as described above corresponds to one electromagnet. Therefore, if the magnetic bearing is 5-axis controlled and there are a total of 10 electromagnets 104, 105, 106A, and 106B, a similar amplifier circuit 150 is configured for each electromagnet, and the 10 amplifier circuits 150 are connected in parallel to the power supply 171.

[0041] Furthermore, the amplifier control circuit 191 is configured, for example, by a digital signal processor (hereinafter referred to as the DSP section) of the control device 200 (not shown), and this amplifier control circuit 191 is configured to switch transistors 161 and 162 on and off.

[0042] The amplifier control circuit 191 compares the current value detected by the current detection circuit 181 (the signal reflecting this current value is called the current detection signal 191c) with a predetermined current command value. Based on this comparison, it determines the magnitude of the pulse width (pulse width time Tp1, Tp2) to be generated within the control cycle Ts, which is one period of PWM control. As a result, gate drive signals 191a and 191b with this pulse width are output from the amplifier control circuit 191 to the gate terminals of transistors 161 and 162.

[0043] Furthermore, when the rotating body 103 passes a resonance point during accelerated rotational speed operation, or when disturbances occur during constant-speed operation, it is necessary to control the position of the rotating body 103 with high speed and strong force. For this reason, a high voltage of, for example, 50V is used as the power supply 171 so that the current flowing through the electromagnet winding 151 can be rapidly increased (or decreased). In addition, a capacitor is usually connected between the positive electrode 171a and the negative electrode 171b of the power supply 171 to stabilize the power supply 171 (not shown).

[0044] In this configuration, when both transistors 161 and 162 are turned on, the current flowing through the electromagnet winding 151 (hereinafter referred to as the electromagnet current iL) increases, and when both are turned off, the electromagnet current iL decreases.

[0045] Furthermore, by turning one of transistors 161 and 162 on and the other off, a so-called flywheel current is maintained. By allowing this flywheel current to flow through the amplifier circuit 150, hysteresis loss in the amplifier circuit 150 can be reduced, and the overall power consumption of the circuit can be kept low. In addition, by controlling transistors 161 and 162 in this way, high-frequency noise such as harmonics generated in the turbomolecular pump 100 can be reduced. Moreover, by measuring this flywheel current with the current detection circuit 181, the electromagnet current iL flowing through the electromagnet winding 151 can be detected.

[0046] In other words, if the detected current value is smaller than the current command value, both transistors 161 and 162 are turned on only once during the control cycle Ts (e.g., 100 μs) for a duration corresponding to the pulse width time Tp1, as shown in Figure 3. Therefore, the electromagnet current iL during this period increases from the positive electrode 171a to the negative electrode 171b, towards the current value iLmax (not shown) that can flow through transistors 161 and 162.

[0047] On the other hand, if the detected current value is greater than the current command value, both transistors 161 and 162 are turned off only once during the control cycle Ts for a duration corresponding to the pulse width time Tp2, as shown in Figure 4. Therefore, during this period, the electromagnet current iL decreases from the negative electrode 171b towards the positive electrode 171a, towards a regenerative current value iLmin (not shown) via diodes 165 and 166.

[0048] In either case, after the pulse width time Tp1 and Tp2 have elapsed, one of transistors 161 or 162 is turned on. Therefore, during this period, the flywheel current is maintained in the amplifier circuit 150.

[0049] The turbomolecular pump 100, having this basic configuration, has an intake section on the upper side (the side with the intake port 101) in Figure 1 that connects to the target equipment, and an exhaust section on the lower side (the side where the exhaust port 15, which constitutes the exhaust port 133, is provided on the base portion 129 so that it protrudes to the right in the figure) that connects to an auxiliary pump (back pump), etc., which is not shown. Furthermore, the turbomolecular pump 100 can be used not only in the vertical position shown in Figure 1, but also in an inverted position, a horizontal position, and an inclined position.

[0050] Furthermore, in the turbomolecular pump 100, the aforementioned outer cylinder 127 and base portion 129 are combined to form a single case. In the following, both the outer cylinder 127 and base portion 129 may be collectively referred to as the "casing" or "main casing." Alternatively, the outer cylinder 127 or the base portion 129 may be referred to as the "casing" alone. The turbomolecular pump 100 is electrically (and structurally) connected to a box-shaped electrical case (not shown), and the aforementioned control device 200 is incorporated into the electrical case.

[0051] The internal structure of the main casing of the turbomolecular pump 100 (here, a combination of the outer cylinder 127 and the base part 129) can be divided into a rotating mechanism part 136 that rotates the rotor shaft 113 etc. by the motor 121, and an exhaust mechanism part 137 that is rotationally driven by the rotating mechanism part 136. Furthermore, the exhaust mechanism part 137 can be considered as being divided into a turbomolecular pump mechanism part 138 composed of rotating blades 102 and fixed blades 123 etc., and a screw groove pump mechanism part (Holbeck type exhaust mechanism part 204) composed of the lower cylindrical part 103b of the rotating body and a screw stator 131 etc.

[0052] Furthermore, the aforementioned purge gas (protective gas) is used to protect the bearing parts and the rotor blades 102, preventing corrosion caused by exhaust gas (process gas) and cooling the rotor blades 102. This purge gas can be supplied using conventional methods.

[0053] For example, the aforementioned purge gas port 132, which extends linearly in the radial direction, is provided at a predetermined location on the base portion 129 (such as at a position 90 or 120 degrees away from the exhaust port 133). Purge gas is then supplied to this purge gas port 132 from the outside of the base portion 129 via a purge gas cylinder (such as an N2 gas cylinder) or a flow regulator (valve device).

[0054] The aforementioned protective bearing 120 is also called a "touchdown (T / D) bearing" or "backup bearing." These protective bearings 120 prevent the rotor shaft 113 from changing position or attitude significantly, and protect the rotor blades 102 and their surrounding parts from damage, even in the event of an electrical system malfunction or atmospheric re-entry.

[0055] Note that in Figure 1, which shows the structure of the turbomolecular pump 100 and the rotating body 103, the hatching indicating the cross-section of the parts has been omitted to avoid making the drawing too complex.

[0056] <Configuration of the plasma generation unit 210> As mentioned above, product deposits may accumulate inside the turbomolecular pump 100. In this embodiment, the product is cleaned using a plasma generating unit 210 as shown in Figures 1 and 5(a) and (b).

[0057] Here, Figure 5(a) is a magnified view of the area enclosed by frame A in Figure 1, and schematically shows it together with the plasma power supply unit 250 (described later). Figure 5(b) is a magnified view of the area enclosed by frame B in Figure 5(a), and schematically shows it. Note that in Figures 5(a) and (b), the hatching indicating the cross-section of the components has been omitted to avoid making the drawings cluttered.

[0058] The plasma generation unit 210 is located inside the pressure vessel 100B (Figures 1 and 5(a)). The pressure vessel 100B corresponds to the case (also called the "casing" or "main casing"). As mentioned above, the pressure vessel 100B is constructed by airtightly combining the outer cylinder 127 and the base portion 129.

[0059] The plasma generating unit 210, located inside the pressure vessel 100B, is constructed using the aforementioned screw stator 131, base portion 129, and lower cylindrical portion 103b of the rotating body. Furthermore, the plasma generating unit 210 is equipped with an inner stator 212.

[0060] Of these, the screw stator 131, as mentioned above, together with the lower cylindrical portion 103b of the rotating body, constitutes the Holbeck-type exhaust mechanism 204. The screw stator 131 is a cylindrical member that can be made of various metals.

[0061] Multiple helical screw grooves 131a are engraved on the inner circumferential surface of the screw stator 131, as shown only in cross-section in Figures 5(a) and (b). The screw grooves 131a are demarcated by projections 131b that protrude radially inward from the screw stator 131. The projections 131b are formed continuously within a predetermined angular (phase) range. The Holbeck-type exhaust mechanism 204 constitutes the drag pump section.

[0062] As shown in Figure 5(a), the screw stator 131 is positioned inside the base portion 129 and is fixed to the base portion 129 via bolts 214. Specifically, as shown in Figure 5(a), an annular flange portion 216 is formed on the outer circumferential surface of the screw stator 131 so as to protrude substantially vertically. In addition, an annular flange portion 218 is formed on the inner circumferential surface of the base portion 129 so as to protrude substantially vertically.

[0063] The flange portion 216 of the screw stator 131 is superimposed on the flange portion 218 of the base portion 129 via an insulating member 222 that has electrical insulating properties. An insulating member 220 that has electrical insulating properties is interposed between the flange portion 216 of the screw stator 131 and the head of the bolt 214. The insulating members 220 and 222 can be made of ceramic (or synthetic resin, etc.). In this embodiment, a stainless steel socket head cap screw is used as the bolt 214.

[0064] The bolt 214 is screwed into the base portion 129 with the insulating member 220, the flange portion 216 of the screw stator 131, and the insulating member 222 sandwiched between the head and the base portion 129. This type of coupling structure using the bolt 214 and insulating members 220 and 222 is employed at multiple locations (for example, about 3 to 8 locations) in the circumferential direction of the flange portion 216 of the screw stator 131 at even intervals.

[0065] The insulating member 220 can be a cylindrical (collar-shaped) or annular (washer-shaped) member that is combined with each bolt 214. The insulating member 220 may also be an annular member formed along the entire circumference of the flange portion 216 of the screw stator 131, and may have multiple bolt holes (not shown) in a number and arrangement corresponding to the multiple bolts 214.

[0066] On the other hand, the insulating member 222 between the flange portion 216 of the screw stator 131 and the flange portion 218 of the base portion 129 can be one that is formed in an annular shape along the entire circumference of the flange portion 218 of the base portion 129 and has bolt holes (not shown) corresponding to a plurality of bolts 214.

[0067] In the first embodiment, the insulating member 222 on the base portion 129 side has an L-shaped cross-section on one side in the radial direction. The insulating member 222 provides insulation not only between the two flange portions 216 and 218, but also between the inner circumference of the flange portion 218 of the base portion 129 and the main body portion 224 of the screw stator 131. Note that the insulating member 222 on the base portion 129 side may be a cylindrical (collar-shaped) or annular (washer-shaped) member combined with each bolt 214.

[0068] Next, the aforementioned inner stator 212 will be described. The inner stator 212 is formed in a cylindrical shape with an outer diameter smaller than the inner diameter of the screw stator 131 (and the lower cylindrical portion 103b of the rotating body), and is coaxially arranged inside the screw stator 131 (and the lower cylindrical portion 103b of the rotating body).

[0069] The inner stator 212 is fixed to the base portion 129 via bolts 234. Specifically, an annular flange portion 236 is formed on the inner circumferential surface of the inner stator 212 so as to protrude substantially vertically. The flange portion 236 of the inner stator 212 is superimposed on the flange portion 238 of the stator column 122 via an insulating member 242 that has electrical insulating properties. The flange portion 238 of the stator column 122 is superimposed in direct contact with the base portion 129.

[0070] An insulating member 240 having electrical insulating properties is interposed between the flange portion 236 of the inner stator 212 and the head of the bolt 234. In this embodiment, a stainless steel hex socket head bolt is used as the bolt 234.

[0071] The bolt 234 is screwed into the base portion 129 with an insulating member 240, the flange portion 236 of the inner stator 212, and an insulating member 242 sandwiched between its head and the flange portion 238 of the stator column 122. This type of coupling structure using the bolt 234 and insulating members 240 and 242 is employed at multiple locations (for example, about 3 to 8 locations) in the circumferential direction of the flange portion 238 of the stator column 122 at even intervals.

[0072] The insulating members 240 and 242 can be cylindrical (collar-shaped) or annular (washer-shaped) components combined with individual bolts 234. Alternatively, the insulating members 240 and 242 may be formed in an annular shape along the entire circumference of the flange portion 238 of the stator column 122 and have multiple bolt holes (not shown) in a number and arrangement corresponding to multiple bolts 234.

[0073] In this first embodiment, the inner stator 212 and the threaded stator 131 are two (and two types of) stator parts (stator bodies) that constitute the comprehensive stator section 226. Since the threaded stator 131 is a stator part located outside the inner stator 212, it can also be referred to as, for example, the "outer stator." Furthermore, the "inner stator" can be referred to as the "inner stator section," and the "outer stator" can be referred to as the "outer stator section."

[0074] The inner stator 212, the threaded stator 131, and the base portion 129 are components (vacuum pump components) that do not rotate during the operation of the turbomolecular pump 100. The comprehensive stator portion 226 in the first embodiment includes the inner stator 212, the threaded stator 131, and the base portion 129.

[0075] Furthermore, the lower cylindrical portion 103b of the rotating body is a component (vacuum pump component) that rotates when the turbomolecular pump 100 is in operation, and is included in the rotor portion in the first embodiment. In the first embodiment, the rotating body 103 corresponds to the "rotor portion," and the lower cylindrical portion 103b of the rotating body constitutes a part of the rotating body 103 (rotor portion).

[0076] In the integrated stator section 226, the inner stator 212 and the threaded stator 131 (outer stator) face each other radially, with the lower cylindrical section 103b of the rotating body in between. Furthermore, an inner discharge gap section 262 and an outer discharge gap section 264 are formed between the outer circumferential surface of the inner stator 212 and the inner circumferential surface of the lower cylindrical section 103b of the rotating body, and between the outer circumferential surface of the lower cylindrical section 103b of the rotating body and the threaded stator 131. The inner stator 212 and the threaded stator 131 face each other with the inner discharge gap section 262, the outer discharge gap section 264, and the lower cylindrical section 103b of the rotating body in between.

[0077] Of these, the outer circumferential surface of the inner stator 212 and the inner circumferential surface of the lower cylindrical portion 103b of the rotating body are both formed in a curved shape. Therefore, the inner discharge gap portion 262 between the inner stator 212 and the lower cylindrical portion 103b of the rotating body is formed at a substantially uniform interval with respect to the axial direction of the inner stator 212 (and the lower cylindrical portion 103b of the rotating body).

[0078] Regarding the outer discharge gap portion 264, the outer circumferential surface of the lower cylindrical portion 103b of the rotating body is curved. However, because the inner circumference of the screw stator 131 has irregularities due to the projections 131b and screw grooves 131a, the distance between the screw stator 131 and the lower cylindrical portion 103b of the rotating body varies in some areas and is not uniform.

[0079] Furthermore, the projection 131b is formed in a tapered shape, with its cross-section becoming narrower towards the tip. The tip of the projection 131b, which is sharper than the base end, approaches and corresponds to the lower cylindrical portion 103b of the rotating body. In the first embodiment, the gap between the tip of the projection 131b and the outer circumferential surface of the lower cylindrical portion 103b of the rotating body is the outer discharge gap portion 264.

[0080] Next, the plasma power supply unit (hereinafter referred to as the "power supply unit") 250 will be described. As shown in Figure 5(a), the power supply unit 250 is composed of a first AC power supply unit 252, a second AC power supply unit 254, and a signal generator 256. As shown in Figure 5(b), the first AC power supply unit 252 is electrically connected to the inner stator 212 and the base unit 129 via a connector 258 and wiring 258a.

[0081] The second AC power supply unit 254 is electrically connected to the screw stator 131 (outer stator) and the base unit 129 via a connector 258 and wiring 258b. The connections of the first AC power supply unit 252 and the second AC power supply unit 254 to the base unit 129 are made such that the pressure vessel 100B is at the reference potential (ground, GND), as shown in Figure 5(a).

[0082] The first AC power supply unit 252 applies the AC voltage necessary to generate a discharge in the inner discharge gap 262 (Figure 5(b)) to the inner stator 212 and base 129. The second AC power supply unit 254 applies the AC voltage necessary to generate a discharge in the outer discharge gap 264 (Figure 5(b)) to the screw stator 131 (outer stator) and base 129. In other words, the inner stator 212 and base 129 are used as discharge electrodes for plasma generation.

[0083] The first AC power supply unit 252 and the second AC power supply unit 254 output voltages that are out of phase with respect to each other. These out-of-phase voltages are output from the signal generator 256 to the pressure vessel 100B via the first AC power supply unit 252 and the second AC power supply unit 254.

[0084] The voltages applied from the first AC power supply unit 252 and the second AC power supply unit 254 to the inner stator 212 and the base unit 129 are set independently. The applied voltages are set by a combination of mechanical and electrical adjustment methods.

[0085] The mechanical adjustment method involves setting the balance between the inner discharge gap 262 and the outer discharge gap 264, as shown in Figure 5(b). The balance is set so that the discharge amounts in the inner discharge gap 262 and the outer discharge gap 264 are as equal as possible (balanced). Mechanical adjustment is performed by setting the distance between the inner discharge gap 262 and the outer discharge gap 264 during the mechanical design stage, or by adjustments during assembly (balancing, adjustments using assembly tolerances, etc.).

[0086] By balancing the discharge amount, charging of the lower cylindrical portion 103b of the rotating body can be avoided. As a result, the current flowing through the lower cylindrical portion 103b of the rotating body approaches zero, and the amount of heat generated is reduced. After mechanically adjusting the inner discharge gap portion 262 and the outer discharge gap portion 264 shown in Figure 5(b), the applied voltage to the inner stator 212 and the base portion 129 is set by an electrical adjustment method using an electrical circuit (including an electronic circuit) in order to further fine-tune the balance of the discharge voltage. The function for such an electrical adjustment method can be provided in the signal generator 256. More specifically, the signal generator 256 can be equipped with circuit constant adjustment devices such as variable capacitors, variable coils, and / or variable resistors corresponding to the first AC power supply unit 252 and the second AC power supply unit 254, respectively.

[0087] The first AC power supply unit 252 and the second AC power supply unit 254 may be incorporated into the signal generator 256. Furthermore, the signal generator 256 may be electrically connected between the first AC power supply unit 252 and the second AC power supply unit 254 and the pressure vessel 100B.

[0088] Furthermore, the power supply to the inner stator 212 and the screw stator 131 (outer stator) and the base portion 129 is performed while the rotating body 103, including the rotor shaft 113, is magnetically levitated by the protective bearing 120 (Figure 1).

[0089] <Functions of the plasma generation unit 210> In a vacuum evacuation system 100A equipped with such a plasma generation unit 210, a raw material gas (also called "fuel gas") for plasma generation is introduced into the pressure vessel 100B. The raw material gas can be introduced, for example, by forming a radially extending raw material gas supply port (raw material gas supply passage, not shown) in the base portion 129 that constitutes the pressure vessel 100B, and introducing the raw material gas from outside the turbomolecular pump 100 into the Holbeck-type exhaust mechanism 204 or into the inside of the lower cylindrical portion 103b of the rotating body. Examples of raw material gases used include NF3 (nitrogen trifluoride) and CF4 (methane tetrafluoride).

[0090] The raw material gas is introduced into the inner discharge gap section 262 and the outer discharge gap section 264. The first AC power supply section 252 and the second AC power supply section 254 apply voltage to the inner stator 212 and the screw stator 131 (outer stator), causing a discharge to occur in the inner discharge gap section 262 and the outer discharge gap section 264, generating a plasma accompanied by ions and radicals (F radicals).

[0091] Since a discharge occurs between the screw stator 131 (outer stator) and the lower cylindrical part 103b of the rotating body, ions attracted to the voltage-applied screw stator 131 collide with the deposits at high speed, cleaning the deposits. In addition, electrically neutral radicals are also used to clean the deposits along with ions. Therefore, not only are radicals utilized, but the plasma containing ions is also effectively utilized, resulting in cleaning with excellent properties.

[0092] Furthermore, projections 131b are provided on the opposing surfaces of the rotor section (rotating body 103) and the stator section (here, the screw stator 131), forming a drag pump section (here, the Holbeck-type exhaust mechanism section 204). Generally, deposits tend to accumulate in drag pump sections such as the Holbeck-type exhaust mechanism section 204. However, in the vacuum exhaust device 100A of the first embodiment, the rotor section (here, the rotating body 103) and the stator section (here, the screw stator 131) constitute discharge electrodes for plasma generation. Therefore, plasma is generated directly in the drag pump section.

[0093] Furthermore, the projection 131b of the screw stator 131 (outer stator) is formed in a tapered shape that narrows towards the tip. As a result, electric charge concentrates in a small area, making discharge more likely. In addition, high-density discharge occurs, and deposits are cleaned by the high-density discharge. The degree of taper in the projection 131b is determined to facilitate good discharge. As mentioned above, even if the projection 131b is formed on the outer circumferential surface side of the lower cylindrical portion 103b of the rotating body, good discharge can be achieved in a similar manner by forming the projection 131b in a tapered shape.

[0094] Furthermore, in order to effectively discharge with the limited power of the power supply unit 250, it is desirable to accurately generate discharge within the range of the drag pump unit (in this case, the Holbeck-type exhaust mechanism unit 204). If discharge can be generated only in the discharge gap section (in this case, the inner discharge gap section 262 and the outer discharge gap section 264), unintended discharge in parts other than the drag pump unit (Holbeck-type exhaust mechanism unit 204) can be prevented.

[0095] In the first embodiment, the plasma generating unit 210 is provided with the aforementioned insulating members 220, 222, 240, and 242. These insulating members 220, 222, 240, and 242 provide electrical insulation between the screw stator 131 and the base portion 129, and between the inner stator 212 and the stator column 122 and the base portion 129. Therefore, the insulating members 220, 222, 240, and 242 function as an electrical insulating section (and a second electrical insulating section). The insulating members 220, 222, 240, and 242 prevent unintended discharge due to charge accumulation in areas other than the plasma generating unit 210. The term "second electrical insulation section" is used to distinguish the location and structure of application, and the second electrical insulation section may exist independently even if the first electrical insulation section is absent.

[0096] Furthermore, in order to limit the discharge to a desired area, it is conceivable to apply an electrical insulation treatment (such as ceramic coating or resin coating) to at least a portion of the area excluding the discharge gap (inner discharge gap 262 and outer discharge gap 264), thereby creating an electrically insulated area through the insulation treatment.

[0097] Specific locations where electrical insulation is provided through insulation treatment include, for example, parts of the screw stator 131 (outer stator) other than the protrusions 131b and screw grooves 131a (such as the non-facing parts 272a to 272c (Figure 5(b)) with respect to the lower cylindrical part 103b of the rotating body). Also, in the inner stator 212, examples include the non-facing parts 274a to 274c (Figure 5(b)) with respect to the lower cylindrical part 103b of the rotating body. Furthermore, examples include the lower end surface 276a of the rotating body 103 (rotor part), the intake side stepped surface 276b, and the adjacent part 276c with respect to the turbomolecular pump mechanism 138.

[0098] Furthermore, it is conceivable that the rotating body 103 may become charged and discharged when voltage is applied to the inner stator 212 or the screw stator 131 (outer stator). Possible discharge locations include the area between the rotor blades 102 and the fixed blades 123, which are close to each other, and the area between the rotor blades 102 and the fixed blade spacer 125.

[0099] More specifically, although symbols are omitted, examples of areas where discharge may occur include at least one of the following: the blade surface, outer end surface, base end surface of the rotor blade 102 or fixed blade 123, the areas between individual rotor blades 102 (102a, 102b, 102c...), and the areas between individual fixed blades 123 (123a, 123b, 123c...). Another example is the area between the outer end surface of the rotor blade 102 and the inner circumferential surface of the fixed blade spacer 125. It is conceivable to provide electrically insulating parts in these areas by insulating treatment (such as ceramic coating or resin coating).

[0100] Furthermore, the rotor shaft 113 of the rotating body 103 is another area where unintended discharges may occur. Without any countermeasures, the charged area can expand from the rotor blades 102 and the rotating body 103a to the rotor shaft 113. Discharges on the rotor shaft 113 are thought to occur between the rotor shaft 113 and various electromagnets (upper radial electromagnet 104, lower radial electromagnet 105 and axial electromagnets 106A, 106B), or between the rotor shaft 113 and various bearings (protective bearing 120 and other bearings).

[0101] Therefore, as shown in the upper part of Figure 1, it is conceivable to interpose insulating members 246 and 248 having electrical insulating properties between the rotating body 103a and the rotor shaft 113. The insulating members 246 and 248 can be made of ceramic (or synthetic resin, etc.).

[0102] In the example shown in Figure 1, the rotor shaft 113 is coaxially inserted into the rotating body 103a and connected to the rotating body 103a via a number of bolts 249 (only two are shown). In the first embodiment, stainless steel socket head cap screws are used as the bolts 249. The bolts 249 are arranged at even intervals, for example, in 3 to 6 locations.

[0103] The bolt 249 is screwed into the rotor shaft 113 with an insulating member 248 sandwiched between its head and the rotating body 103a. The insulating member 248 can be a cylindrical (collar-shaped) or annular (washer-shaped) member that is combined with each bolt 249. Alternatively, the insulating member 248 may be formed in an annular shape along the entire circumference of the rotating body 103a and have multiple bolt holes (not shown) in a number and arrangement corresponding to the multiple bolts 249. In the example in Figure 1, multiple annular (washer-shaped) members (only two are shown) are used as the insulating member 248.

[0104] On the other hand, a stepped cylindrical (collar-shaped) insulating member 246 is used between the rotating body 103a and the rotor shaft 113. The insulating member 246 has a cylindrical portion 246a and a flange portion 246b. The cylindrical portion 246a of the insulating member 246 is interposed between the relatively small diameter portion of the rotor shaft 113 and the rotating body 103a. The flange portion 246b of the insulating member 246 is interposed between the relatively large diameter portion of the rotor shaft 113 and the rotating body 103a.

[0105] These insulating members 246 and 248 function as electrical insulators (and first electrical insulators), preventing the charged area from expanding from the rotor blades 102 to the rotor shaft 113. This prevents discharge between the rotor shaft 113 and the various electromagnets, and between the rotor shaft 113 and the various bearings.

[0106] Furthermore, as mentioned above, the inner stator 212 and the screw stator 131 face each other radially, with the lower cylindrical portion 103b of the rotating body (which constitutes part of the rotor) in between. This makes it easier to bring the inner stator 212 and the screw stator 131 closer together. Polarization is more likely to occur within the lower cylindrical portion 103b of the rotating body, and the current flowing within the lower cylindrical portion 103b of the rotating body becomes more regular. As a result, the current flowing within the lower cylindrical portion 103b of the rotating body can be minimized. In other words, arranging the inner stator 212 and the screw stator 131 to face each other radially is more advantageous for controlling (and managing) the current flowing through the lower cylindrical portion 103b of the rotating body compared to when they are offset axially.

[0107] Furthermore, as a method of offsetting the inner stator 212 and the threaded stator 131 in the axial direction, although not shown in the illustration, a method of aligning them in the axial direction with an insulating member (electrical insulating part) in between is also conceivable. In this case, the two stator parts (inner stator 212 and threaded stator 131) are formed with approximately the same diameter (outer diameter and / or inner diameter). In addition, the two stator parts can be distinguished not as inner and outer, but as, for example, intake side and exhaust side (intake side stator part and exhaust side stator part).

[0108] However, when the two stator sections (inner stator 212 and screw stator 131) are positioned radially opposite each other with the lower cylindrical section 103b of the rotating body (part of the rotor section) in between, it is more advantageous for controlling (and managing) the current flowing through the lower cylindrical section 103b of the rotating body compared to when they are positioned (offset) in the axial direction. For this reason, in the first embodiment, the two stator sections are positioned radially opposite each other with the lower cylindrical section 103b of the rotating body in between, but the two stator sections may be offset in the axial direction if there is no particular problem.

[0109] Furthermore, as mentioned above, the pressure vessel 100B is equipped with a gas supply port (not shown) capable of supplying plasma raw material gas, which provides a high degree of flexibility in the placement of the gas supply port (not shown). It is also easy to position the gas supply port (not shown) close to the drag pump section (in this case, the Holbeck-type exhaust mechanism section 204). The number of gas supply ports (not shown) may be one or multiple. If only one is used, the processing of the components constituting the pressure vessel 100B is simplified.

[0110] If multiple gas supply ports are used, the gas supply ports (not shown) can be arranged at equal intervals (180-degree intervals, 120-degree intervals, 90-degree intervals, 45-degree intervals, 30-degree intervals, etc.) in the circumferential direction of the discharge gap section (inner discharge gap section 262 and outer discharge gap section 264). By using multiple gas supply ports (not shown), it becomes possible to supply the raw material gas without unevenness or bias.

[0111] Furthermore, the two stator sections (inner stator 212 and threaded stator 131) are electrically insulated from the pressure vessel 100B by insulating members 220, 222, 240, and 242. In addition, AC voltages are applied to the two stator sections by the power supply unit 250 in opposite phases. The two stator sections and the pressure vessel 100B are electrically connected such that the pressure vessel 100B is at the reference potential. The voltage applied to the two stator sections is also properly controlled.

[0112] In the first embodiment, the power supply unit 250 applies an AC voltage to the two stator sections (the inner stator 212 and the screw stator 131), but this is not limited to this, and for example, a DC voltage may be applied instead.

[0113] In this case, for example, the first AC power supply unit 252 and the second AC power supply unit 254 are each replaced with a DC power supply unit (not shown). Furthermore, the power supply circuit is configured to apply a negative voltage to the screw stator 131. Then, discharge is considered to occur from the screw stator 131 to the lower cylindrical part 103b of the rotating body, and from the lower cylindrical part 103b of the rotating body to the inner stator 212. Then, the applied voltages (V1, V2) of the DC power supply unit (not shown) are adjusted according to the ease of each discharge, so that the current value between the power supply unit 250 and the pressure vessel 100B becomes zero.

[0114] When an AC voltage is applied, as in the first embodiment, the discharge becomes a relatively stable glow discharge, while when a DC voltage is applied, it becomes a relatively unstable arc discharge. Furthermore, when an AC voltage is applied, it is easier to generate a high-density plasma by utilizing the frequency dependence. Also, when an AC voltage is applied, it is possible to perform a high-density discharge at a lower voltage value compared to when a DC voltage is applied. For this reason, applying an AC voltage is more advantageous than applying a DC voltage. However, it is also possible to apply a DC voltage depending on the required characteristics.

[0115] Furthermore, in the first embodiment, the applied voltage to the two stator sections (the inner stator 212 and the screw stator 131) can be set independently, and can be adjusted so that the discharge amount from the two stator sections to the rotor section (in this case, the lower cylindrical section 103b of the rotating body) is equal. As a result, the voltage is applied to the two stator sections more appropriately.

[0116] Furthermore, the two stator sections (inner stator 212 and screw stator 131) can be divided into two types, for example, an outer stator section and an inner stator section. Alternatively, they can be divided into two types: one stator section to which the voltage of one of two types of power supplies with opposite phases (such as the first AC power supply section 252 and the second AC power supply section 254) is applied, and another stator section to which the voltage of the other is applied. For this reason, "two stator sections" can also be referred to as "two types of stator sections." It is also possible to have multiple stator sections for each type.

[0117] <Typical advantages of the vacuum exhaust system 100A according to the first embodiment> The vacuum evacuation system 100A described above will be explained below in comparison with the conventional technology shown in Figures 10(a) and (b). In Figures 10(a) and (b), the same reference numerals are used for parts that are the same as those used for the vacuum evacuation system 100A of the first embodiment shown in Figures 1 to 5. Figure 10(a) shows a conventional turbomolecular pump 600 (and vacuum evacuation system 600A).

[0118] In this conventional turbomolecular pump 600, multiple (two in this case) plasma generators 610 are connected to the outer cylinder 127 via a valve device 614 and an introduction pipe 616. This aspect is the same as the invention disclosed in the aforementioned Patent Document 1.

[0119] However, the plasma generator 610 is positioned near the exhaust port 133, where deposits are likely to form, and near the screw stator 131. Furthermore, radicals are introduced into the annular groove 632 and then into the screw groove 131a through the circumferentially arranged communication ports 654. Compared to the invention disclosed in Patent Document 1, this design has advantages such as not requiring a design that partially increases the distance between the rotor blades 102 and the fixed blades 123, and being able to supply radicals from a position closer to the deposits.

[0120] Similar to conventional technologies, in the vacuum evacuation device 100A of the embodiments shown in Figures 1 to 5, the plasma generation unit 210 is located in the drag pump section (Holbeck-type exhaust mechanism section 204), where deposits are prone to form. Furthermore, in the vacuum evacuation device 100A of the first embodiment, the inner stator 212 and the screw stator 131 (outer stator) are used as electrodes for plasma generation. Consequently, the vacuum evacuation device 100A is significantly smaller than the conventional technology shown in Figures 10(a) and (b).

[0121] Furthermore, according to the vacuum evacuation device 100A of the first embodiment, since plasma is generated in the drag pump section (Holbeck-type evacuation mechanism section 204), the plasma can be effectively utilized for cleaning in locations where deposits are likely to form. In addition, a cleaning effect can be obtained by ions, which are active species that make up the plasma. As a result, it is possible to improve the cleaning effect compared to the conventional technology shown in Figures 10(a) and (b).

[0122] Furthermore, according to the vacuum evacuation device 100A of the first embodiment, the plasma generation unit 210 is built into the pressure vessel 100B, and a voltage is applied circumferentially by two electrode sections (inner stator 212 and screw stator 131 (outer stator)). Therefore, the piping and wiring related to the supply of radicals can be consolidated, and the cost of materials and work for wiring and piping can be reduced. In addition, the space required for wiring and piping can be minimized. Moreover, the structure of the plasma generation unit 210 can be simplified, and the plasma generation unit 210 can be miniaturized. As a result, the manufacturing cost of the vacuum evacuation device 100A can be reduced. Furthermore, the degree of flexibility in the installation of the vacuum evacuation device 100A can be increased.

[0123] Furthermore, if the same installation space as before can be secured, the turbomolecular pump 100 can be enlarged (increased capacity), and the plasma generation unit 210 can be enlarged in accordance with the enlargement of the turbomolecular pump 100.

[0124] Furthermore, existing components of the turbomolecular pump 100 (such as the lower cylindrical part 103b of the rotating body, the base part 129, the screw stator 131, and the bolts 214, 234, 249) can be used when forming the plasma generation section 210. This also allows for cost reduction.

[0125] <Basic configuration of the vacuum exhaust system 300A according to the second embodiment> Next, the vacuum exhaust device 300A according to the second embodiment will be described. Note that parts similar to those in the first embodiment are denoted by the same reference numerals, and their descriptions will be omitted as appropriate.

[0126] Figures 6 and 7(a) and 7(b) show a vacuum evacuation device 300A according to the second embodiment. In the vacuum evacuation device 300A, the configuration of the plasma generation unit 310 related to the turbomolecular pump 300 differs from that of the first embodiment. In the plasma generation unit 210 of the first embodiment, two (two types) stator sections were composed of a screw stator 131 (outer stator) and an inner stator 212. In contrast, in the second embodiment, two (two types) stator sections are composed of a screw stator 131 and a base section 129. Here, in the second embodiment, the base section 129 and the screw stator 131 are two (two types) stator sections that constitute the comprehensive stator section 326.

[0127] Furthermore, as shown in Figure 7(b), an outer discharge gap 364 is formed between the projection 131b of the screw stator 131 and the inner circumferential surface of the lower cylindrical portion 303b of the rotating body. In the second embodiment, an inner discharge gap 362 is formed between the lower cylindrical portion 303b of the rotating body and the stator column 322. Also, in the second embodiment, the inner corner (upper corner) of the lower cylindrical portion 303b of the rotating body is thicker than the lower cylindrical portion 103b of the rotating body in the first embodiment. The screw stator 131 and the stator column 322 are radially opposed to each other, with the inner discharge gap 362, the outer discharge gap 364, and the lower cylindrical portion 303b of the rotating body in between.

[0128] Next, the plasma power supply unit (hereinafter referred to as the "power supply unit") 350 is configured to include an AC power supply unit 352, as shown in Figure 7(a). The AC power supply unit 352 is electrically connected to the screw stator 131 and the base unit 129 via connectors 258 and wiring 358a and 358b, as shown in Figure 7(b). The base unit 129 is coupled to the stator column 322 so that it can be energized.

[0129] <Functions of the plasma generation unit 310> In the plasma generation unit 310 according to the second embodiment, plasma is directly generated in the inner discharge gap 362 and outer discharge gap 364 formed in the drag pump unit (here, the Holbeck-type exhaust mechanism unit 204). The functions of the projection 131b and the insulating members 220, 222, 246, and 248 are the same as in the first embodiment.

[0130] Furthermore, similar to the first embodiment, it is possible to provide an electrically insulated section by applying an electrical insulation treatment (such as ceramic coating or resin coating) to at least a portion of the area excluding the inner discharge gap section 362 and the outer discharge gap section 364. The function of the gas supply port (not shown) is also the same as the first embodiment in that it can supply raw material gas to the inner discharge gap section 362 and the outer discharge gap section 364. Also, similar to the first embodiment in that the power supply unit 350 applies an AC voltage.

[0131] <Typical advantages of the vacuum exhaust system 300A according to the second embodiment> This second embodiment also provides a compact vacuum exhaust device 300A with excellent cleaning effect, using a configuration similar to that of the first embodiment. Furthermore, the configuration of the plasma generation unit 310 and the power supply unit 350 can be simplified compared to the first embodiment. It is also possible that the vacuum exhaust device 300A according to the second embodiment is one in which the inner stator 212 of the vacuum exhaust device 300A according to the first embodiment is integrated with the stator column 322.

[0132] <Basic configuration of the vacuum exhaust system 400A according to the third embodiment> Next, the vacuum evacuation device 400A according to the third embodiment will be described. Note that parts similar to those in the first and second embodiments are denoted by the same reference numerals, and their descriptions are omitted as appropriate.

[0133] Figures 8 and 9(a) and 9(b) show a vacuum evacuation system 400A according to the third embodiment. In the vacuum evacuation system 400A, the drag pump section of the plasma generation section 410 related to the turbomolecular pump 400 is configured with a Sigburn type exhaust mechanism section 404, rather than a Holbeck type exhaust mechanism section 204 as in the first and second embodiments.

[0134] In the Sigburn-type exhaust mechanism 404, as shown in Figures 9(a) and (b), multiple spiral groove channels 414, partitioned by peaks 412, are formed in the gap between the rotating discs 406a and 406b provided on the rotating body 403 and the fixed discs 410a and 410b fixed to the base portion 429. The Sigburn-type exhaust mechanism 404 then provides tangential momentum to gas molecules diffused within the spiral groove channels 414 by the rotating discs 406a and 406b, and gives them a predominantly directional position towards the exhaust direction by the spiral groove channels 414, thereby performing exhaust.

[0135] The peaks 412 and spiral groove channels 414 are provided on at least one of the rotating discs 406a, 406b and the fixed discs 410a, 410b. Furthermore, a general structure can be adopted for the Sigburn-type exhaust mechanism 404. In this third embodiment, the fixed discs 410a, 410b are two (two types) stator sections that constitute the comprehensive stator section 426. The fixed discs 410a, 410b are included in the rotating body 403 (rotor section).

[0136] A first discharge gap 462, a second discharge gap 464, and a third discharge gap 466 are formed between the rotating disks 406a and 406b and the fixed disk 410a, and between the rotating disk 406b and the fixed disk 410b. The fixed disks 410a and 410b face each other in the axial direction, with the second discharge gap 464, the rotating disk 406a, and the third discharge gap 466 in between.

[0137] The peak portion 412 is formed in a tapered shape that narrows towards the tip. As a result, electric charge concentrates in a small area, making discharge more likely. This is the same as the projection portion 131b in the first and second embodiments.

[0138] As the plasma power supply unit (hereinafter referred to as the "power supply unit") 450 according to the third embodiment, for example, the same as the power supply unit 250 of the first embodiment can be used. As shown in Figure 9(b), the power supply unit 450 is electrically connected to the fixed discs 410a and 410b via connectors 258 and wiring 458a and 458b. Reference numerals 470, 472 and 474 in Figure 9(b) are insulating members. Alternatively, the insulating member 474 may be omitted, and the fixed disc 410b may be connected to the base portion 129 in a manner that allows current to flow. Furthermore, as shown in the plasma power supply unit 350 according to the second embodiment (Figure 7(a)), it is also possible to apply a configuration in which there is only one AC power supply unit 352. In this case, one of the wires can be connected to either fixed disc (fixed disc 410a or fixed disc 410b), and the other wire can be connected to the base portion 429.

[0139] Furthermore, similar to the first and second embodiments, it is possible to provide an electrically insulated section by applying an electrical insulation treatment (such as ceramic coating or resin coating) to at least a portion of the parts excluding the first discharge gap section 462, the second discharge gap section 464, and the third discharge gap section 466. The function of the gas supply port (not shown) is also the same as in the first and second embodiments, in that it can supply raw material gas to the first discharge gap section 462, the second discharge gap section 464, and the third discharge gap section 466.

[0140] Thus, even in a vacuum exhaust system 400A equipped with a Sigburn-type exhaust mechanism 404, it is possible to configure the plasma generation unit 410 using the drag pump unit. Furthermore, the third embodiment also provides a vacuum exhaust system 400A that is smaller and has superior cleaning effect compared to conventional technology (Figures 10(a) and (b)) in which the plasma generator is connected to the outside of the pressure vessel.

[0141] <Inventions that can be extracted from the embodiments> From the embodiments described above, the following inventions can be extracted. (1) Pressure vessel (pressure vessel 100B, etc.) A rotor section (rotating body 103, 403, etc.) is rotatably held within the pressure vessel, A first stator section (screw stator 131, fixed disc 410a, etc.) is disposed in the pressure vessel opposite the rotor section via a discharge gap section (outer discharge gap sections 264, 364, first discharge gap section 462, second discharge gap section 464, etc.), A vacuum evacuation device equipped with, Voltage can be applied to the first stator section. Vacuum exhaust systems characterized by the following (vacuum exhaust systems 100A, 300A, 400A, etc.). (2) At least a portion of the opposing surfaces of the rotor and the first stator are provided with projections (projections 131b, peaks 412, etc.) that are continuous at a predetermined angle in the circumferential direction, forming a drag pump section (Holbeck-type exhaust mechanism section 204, Sigburn-type exhaust mechanism section 404, etc.) The vacuum exhaust device described in (1) above, characterized in that (3) The projection is formed in a tapered shape that narrows towards the tip. The vacuum exhaust device described in (2) above, characterized in that (4) The rotor portion comprises a rotor body portion (rotating body 103a, etc.) and a rotor shaft portion (rotor shaft 113, etc.), A first electrical insulating portion (insulating members 246, 248, etc.) is provided between the rotor body and the rotor shaft. The vacuum exhaust device described in (1) above, characterized in that (5) At least a portion of the portion excluding the portion facing the discharge gap is provided with an electrical insulating portion (insulating members 220, 222, 240, 242, 246, 248, 470, 472, 474, insulated portion, etc.). The vacuum exhaust device described in (1) above, characterized in that (6) A second electrical insulating portion (insulating members 220, 222, 240, 242, 470, 472, 474, insulated portion, etc.) is provided in at least a part of the portion excluding the portion facing the discharge gap. The vacuum exhaust device described in (4) above, characterized in that (7) The pressure vessel is provided with a gas supply port capable of supplying plasma raw material gas. A vacuum exhaust device according to any one of the above items (1) to (4), characterized in that (8) A second stator section (inner stator 212, stator column 122, fixed disc 410a, etc.) is provided that faces the first stator section, sandwiching the rotor section (lower cylindrical sections 103b, 303b of the rotating body 103, rotating discs 406a, 406b of the rotating body 403, etc.). A vacuum exhaust device according to any one of the above items (1) to (6), characterized in that (9) The first stator section and the second stator section are electrically insulated from the pressure vessel, An AC voltage is applied such that the first stator section and the second stator section are in opposite phases. The first stator section, the second stator section, and the pressure vessel are electrically connected such that the pressure vessel is at a reference potential. The vacuum exhaust device described in (8) above, characterized in that (10) The AC voltages applied to the first stator section and the second stator section can be set independently and are configured to be adjustable so that the discharge amounts from the first stator section and the second stator section to the rotor section are equal. The vacuum exhaust device described in (9) above, characterized in that

[0142] <Other> It should be noted that the present invention is not limited to the embodiments described above, and various modifications and combinations of the embodiments are possible without departing from the spirit of the invention. [Explanation of Symbols]

[0143] 100A, 300A, 400A: Vacuum exhaust system 100B: Pressure vessel 100, 300, 400: Turbomolecular pumps 102: Rotary blade 103, 403: Solids of revolution 103a, 303b: Rotating body 103b: Lower cylindrical part of the rotating body 113: Rotor shaft 122, 322: Status Column 123:Fixed wing 125: Fixed-wing spacer 127: Outer cylinder 129, 429: Base section 131: Screw stator 131a: Screw groove 131b:Protrusion 200: Control device 204: Holbeck-type exhaust mechanism 210, 310, 410: Plasma generation unit 212: Inner stator 220, 222, 240, 242, 246, 248, 470, 472, 474: Insulating material 226, 326, 426: Complete stator section 250, 350, 450: Plasma power supply unit 252: 1st AC power supply section 254: 2nd AC power supply section 256: Signal generator 258: Connector 258a, 258b, 358a, 358b, 458a, 458b: Wiring 262, 362: Inner discharge gap section 264, 364: Outer discharge gap section 352: AC power supply section 404: Sigburn-type exhaust mechanism 406a, 406b: Rotating disk 410a, 410b: Fixed disc 412: Mountain section (protrusion) 414: Spiral groove channel 462: First discharge gap section 464: Second discharge gap section 466: Third discharge gap section

Claims

1. pressure vessel and A rotor portion is rotatably held within the pressure vessel, A first stator section is disposed within the pressure vessel, facing the rotor section via a discharge gap section, A vacuum evacuation device equipped with, A voltage can be applied to the first stator section. A vacuum exhaust device characterized by the following features.

2. At least a portion of the opposing surfaces of the rotor portion and the first stator portion are provided with projections that are continuous at a predetermined angle in the circumferential direction, constituting the drag pump portion. The vacuum exhaust device according to feature 1.

3. The aforementioned projection is formed in a tapered shape that narrows towards the tip. The vacuum exhaust device according to feature 2.

4. The rotor portion comprises a rotor body portion and a rotor shaft portion. A first electrical insulating portion is provided between the rotor body and the rotor shaft. The vacuum exhaust device according to feature 1.

5. An electrical insulating portion is provided in at least a part of the portion excluding the portion facing the discharge gap. The vacuum exhaust device according to feature 1.

6. A second electrical insulating portion is provided in at least a part of the portion excluding the portion facing the discharge gap. The vacuum exhaust device according to feature 4.

7. The pressure vessel is provided with a gas supply port capable of supplying plasma raw material gas. A vacuum exhaust device according to any one of claims 1 to 6.

8. A second stator section is provided that faces the first stator section, with the rotor section in between. A vacuum exhaust device according to any one of claims 1 to 6.

9. The first stator section and the second stator section are electrically insulated from the pressure vessel. An AC voltage is applied such that the first stator section and the second stator section are in opposite phase. The first stator section, the second stator section, and the pressure vessel are electrically connected such that the pressure vessel is at a reference potential. The vacuum exhaust device according to feature 8.

10. The AC voltages applied to the first stator section and the second stator section can be set independently, and are configured to be adjustable so that the discharge amount from the first stator section and the second stator section to the rotor section is equal. The vacuum exhaust device according to feature 9.

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