Vacuum evacuation device

Abstract

[Problem] To provide a vacuum evacuation device having excellent characteristics related to cleaning of deposits. [Solution] The vacuum evacuation device comprises: a pressure vessel 100B; a rotor lower-cylinder part 103b rotatably held in the pressure vessel 100B; and a screw stator 131 disposed to face the rotor lower-cylinder part 103b in the pressure vessel 100B with an outer discharge gap part 264 interposed therebetween. A voltage can be applied to the screw stator 131. Projected parts 131b that are continuous at a prescribed angle in the circumferential direction are disposed at at least a part of the surface where the screw stator 131 and the rotor lower-cylinder part 103b face each other, thereby a drag pump part is constituted. The projected parts 131b are each formed into a tapered shape narrowing to the tip side thereof.

Description

Vacuum exhaust device

[0001] The present invention relates to a vacuum exhaust device using a vacuum pump such as a turbomolecular pump.

[0002] Turbomolecular pumps are commonly known as a type of vacuum pump. These turbomolecular pumps are used, for example, for exhausting gases in manufacturing equipment for semiconductors, flat panels, and the like. Turbomolecular pumps exhaust gases by rotating rotors when a motor inside the pump body is energized, thereby expelling gas molecules (gas molecules) from the gas (process gas) drawn into the pump body. Some turbomolecular pumps are equipped with heaters and cooling tubes to appropriately control the temperature inside the pump.

[0003] In vacuum pumps used for exhausting gas from manufacturing equipment for semiconductors, flat panels, etc., reaction products generated during the manufacturing process of semiconductors and flat panels can accumulate inside the vacuum pump. As a countermeasure, a technology has been devised in which a plasma generator is installed in the vacuum pump and the inside of the pump is plasma cleaned.

[0004] In the invention disclosed in Patent Document 1, 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 to the plasma introduction port. 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. The radicals are then introduced into the exhaust mechanism through a communication port provided in a spacer (fixed blade spacer 125) that holds the stator blade (fixed blade 123). This communication port is provided facing a space created by widening the gap between the rotor blade (rotor blade 102) and the stator blade in the rotational axis direction. Therefore, the larger the communication port (the diameter or opening area of ​​the communication port), the wider the gap between the rotor blade and the stator blade, resulting in a decrease in pump performance. For this reason, the size of the communication port has been kept to a minimum, and multiple communication ports and plasma generators (radical supply means 201) have been provided circumferentially.

[0005] Japanese Patent Application Laid-Open No. 2022-017864

[0006] The radicals used in plasma cleaning are substances forcibly dissociated by applying high energy within the plasma generator. Because of this, radicals have a short lifespan, and it is sometimes impossible to supply radicals to areas far from the plasma generator. Furthermore, in order to supply radicals uniformly throughout the pump at a uniform concentration, multiple plasma generators must be arranged in the circumferential direction. Furthermore, while radicals can be utilized among the active species that make up the plasma, ions cannot, which can sometimes result in insufficient cleaning speed.

[0007] When multiple plasma generators are arranged in the circumferential direction, (1) the cost increases due to the multiple plasma generators, and (2) the number of piping for supplying raw material gas (also called "fuel gas") and cooling water, and the number of wiring for supplying power are required for the number of plasma generators, which can complicate the design and installation and restrict the placement location.

[0008] SUMMARY OF THE INVENTION An object of the present invention is to provide a vacuum exhaust system that has excellent characteristics in terms of cleaning deposits.

[0009] In order to achieve the above object, the present invention provides a vacuum exhaust device comprising: a pressure vessel; a rotor portion rotatably held within the pressure vessel; and a first stator portion disposed within the pressure vessel opposite the rotor portion across a discharge gap portion, wherein a voltage can be applied to the first stator portion.

[0010] According to the above invention, it is possible to provide a vacuum exhaust device that has excellent characteristics in terms of cleaning deposits.

[0011] 1 is an explanatory diagram schematically showing the configuration of a vacuum exhaust device according to a first embodiment of the present invention; FIG. 2 is a circuit diagram of an amplifier circuit; FIG. 3 is a time chart showing control when a current command value is greater than a detection value; and FIG. 4 is a time chart showing control when a current command value is smaller than a detection value. (a) is an enlarged view of a portion surrounded by frame A in FIG. 1 , and (b) is an enlarged view of a portion surrounded by frame B in (a). (b) is an enlarged view of a portion surrounded by frame B in (a). (c) is an explanatory diagram schematically showing the configuration of a vacuum exhaust device according to a third embodiment; (a) is an enlarged view of a portion surrounded by frame A in FIG. 8 , and (b) is an enlarged view of a portion surrounded by frame B in (a). (a) is an explanatory diagram showing a longitudinal section of a turbomolecular pump according to a conventional example, and (b) is an explanatory diagram showing a cross section of a connection portion between an inlet pipe (216) and an outer cylinder (127).

[0012] <Basic Configuration of Vacuum Exhaust Apparatus 100A According to First Embodiment> Fig. 1 shows a vacuum exhaust apparatus 100A according to a first embodiment of the present invention. The vacuum exhaust apparatus 100A includes a vacuum pump (here, a turbomolecular pump 100). This turbomolecular pump 100 is adapted to be connected to a vacuum chamber (not shown) of a target device such as a semiconductor manufacturing device.

[0013] A longitudinal cross-sectional view of this turbomolecular pump 100 is shown in Fig. 1. In Fig. 1, the turbomolecular pump 100 has an intake port 101 formed at the upper end of a cylindrical outer tube 127. Inside the outer tube 127 is a rotor 103 having a plurality of rotors 102 (102a, 102b, 102c, ...) which are turbine blades for sucking in and exhausting gas, formed radially and in multiple stages around its periphery. A rotor shaft 113 is attached to the center of this rotor 103, and this rotor shaft 113 is levitated and supported in the air and its position is controlled by, for example, a five-axis controlled magnetic bearing.

[0014] The upper radial electromagnets 104 are arranged in pairs on the X-axis and the Y-axis. Four upper radial sensors 107 are provided adjacent to the upper radial electromagnets 104 and corresponding to each upper radial electromagnet 104. The upper radial sensors 107 are, for example, inductance sensors or eddy current sensors having conductive windings, and detect the position of the rotor shaft 113 based on changes in the inductance of the conductive windings, which change depending on the position of the rotor shaft 113. The upper radial sensors 107 are configured to detect the radial displacement of the rotor shaft 113, i.e., the rotating body 103 fixed thereto, and send the detected displacement 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 a position signal detected by the upper radial sensor 107, and an amplifier circuit 150 (described later) shown in Figure 2 controls the excitation of the upper radial electromagnet 104 based on this excitation control command signal, thereby adjusting the upper radial position of the rotor shaft 113.

[0016] The rotor shaft 113 is made of a material with high magnetic permeability (iron, stainless steel, etc.) and is attracted by the magnetic force of the upper radial electromagnets 104. Such adjustment is performed independently in the X-axis direction and the Y-axis direction. In addition, the lower radial electromagnets 105 and the lower radial sensors 108 are arranged in the same manner as the upper radial electromagnets 104 and the upper radial sensors 107, and adjust the radial position of the lower side of the rotor shaft 113 in the same manner as the radial position of the upper side.

[0017] Furthermore, axial electromagnets 106A and 106B are arranged above and below a circular metal disk (also called an "armature disk") 111 provided at the bottom of rotor shaft 113. Metal disk 111 is made of a highly magnetic permeable material such as iron. An axial sensor 109 is provided to detect the axial displacement of rotor shaft 113, and an axial position signal from the axial sensor 109 is sent to control device 200.

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

[0019] In this way, the control device 200 appropriately adjusts the magnetic forces that the axial electromagnets 106A and 106B exert on the metal disk 111, magnetically levitating the rotor shaft 113 in the axial direction and holding it in space without contact. The amplifier circuit 150 that controls the excitation of the upper radial electromagnet 104, the lower radial electromagnet 105, and the axial electromagnets 106A and 106B will be described later.

[0020] Meanwhile, motor 121 has a plurality of magnetic poles arranged circumferentially so as to surround rotor shaft 113. Each magnetic pole is controlled by control device 200 so as to rotate rotor shaft 113 via electromagnetic force acting between the magnetic pole and rotor shaft 113. Motor 121 also incorporates a rotational speed sensor (not shown), such as a Hall element, resolver, or encoder, and the rotational speed of rotor shaft 113 is detected by the detection signal of this rotational speed sensor.

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

[0022] A plurality of fixed blades 123 (123a, 123b, 123c...) are arranged at small gaps (predetermined intervals) from the rotating blades 102 (102a, 102b, 102c...). Each of the rotating blades 102 (102a, 102b, 102c...) is inclined 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 blades 123 are formed at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113, and are arranged in a staggered manner with the stages of the rotor blades 102 toward the inside of the outer cylinder 127. The outer peripheral ends of the fixed blades 123 are supported by being inserted between a plurality of stacked fixed blade spacers 125 (125a, 125b, 125c, ...).

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

[0025] Furthermore, depending on the application of the turbomolecular pump 100, a screw stator 131 is disposed 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 any of these metals, and has multiple spiral thread grooves 131a engraved on its inner circumferential surface. The spiral direction of the thread grooves 131a corresponds to the direction in which exhaust gas molecules are transported toward the exhaust port 133 when they move in the rotation direction of the rotor 103. A rotor lower cylindrical portion 103b hangs down from the rotor main body 103a on which the rotor blades 102 (102a, 102b, 102c, ...) of the rotor 103 are formed. The outer circumferential surface of this rotor lower cylindrical portion 103b is cylindrical and protrudes toward the inner circumferential surface of the screw stator 131, and is adjacent to the inner circumferential surface of the screw stator 131 with a predetermined gap between them. The exhaust gas transferred to the thread grooves 131a by the rotor 102 and the fixed blades 123 is guided by the thread grooves 131a and sent to the base portion 129. In this way, the screw stator 131 and the rotor lower cylindrical portion 103b facing it constitute a Holweck type exhaust mechanism portion 204. The Holweck type exhaust mechanism portion 204 gives directionality to the exhaust gas by the rotation of the rotor lower cylindrical portion 103b relative to the screw stator 131, thereby improving the exhaust characteristics of the turbomolecular pump 100.

[0026] The base portion 129 is a disk-shaped member that forms 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 screw stator 131, the base portion 129, and the rotor lower cylindrical portion 103b form the plasma generating portion 210, and the specific configuration of the plasma generating portion 210 will be described later.

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

[0028] The stator spacers 125 are joined together at their outer peripheries and transmit to the outside heat received by the stator 123 from the rotor 102 and frictional heat generated when exhaust gas comes into contact with the stator 123 .

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

[0030] Depending on the application of the turbomolecular pump 100, the electrical equipment section may be covered by a stator column 122 to prevent the gas sucked in from the intake port 101 from entering the electrical equipment section, which is composed of the upper radial electromagnet 104, the upper radial sensor 107, the motor 121, the lower radial electromagnet 105, the lower radial sensor 108, the axial electromagnets 106A and 106B, the axial sensor 109, etc., and the interior of this stator column 122 may be kept at a predetermined pressure by purge gas.

[0031] In this case, a purge gas port 132 is provided in the base portion 129, and purge gas is introduced through this piping. The introduced purge gas is sent to an exhaust port 133 through gaps 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 portion of the rotor blades 102 (lower cylindrical portion 103b of the rotor) and the stator column 122 or the base portion 129.

[0032] Here, the turbomolecular pump 100 requires control based on specific parameters (e.g., various characteristics corresponding to the model) that are individually adjusted and specific to the model. To store these control parameters, the turbomolecular pump 100 is provided with an electronic circuit unit 141 within its body. The electronic circuit unit 141 is composed of a semiconductor memory such as an EEPROM, electronic components such as semiconductor devices for accessing the memory, and a substrate 143 for mounting these components. The electronic circuit unit 141 is housed below a rotational speed sensor (not shown) near the center of a base unit 129 that constitutes the lower part of the turbomolecular pump 100, and is closed by an airtight bottom lid 145.

[0033] In the semiconductor manufacturing process, some process gases introduced into a chamber have the property of solidifying when their pressure exceeds a predetermined value or their temperature falls below a predetermined value. Inside the turbomolecular pump 100, the pressure of the exhaust gas is lowest at the inlet 101 and highest at the outlet 133. If the pressure of the process gas exceeds a predetermined value or the temperature falls below a predetermined value while the process gas is being transferred from the inlet 101 to the outlet 133, the process gas solidifies and adheres to and accumulates inside the turbomolecular pump 100.

[0034] For example, when SiCl4 is used as the process gas in an Al etching apparatus, the vapor pressure curve shows that at low vacuum (760 torr to 10-2 torr) and low temperature (approximately 20°C), a solid product (e.g., AlCl3) precipitates and adheres to and accumulates inside the turbomolecular pump 100. As a result, when precipitates of the process gas accumulate inside the turbomolecular pump 100, these deposits narrow the pump flow path, causing a decrease in the performance of the turbomolecular pump 100. The above-mentioned product is prone to solidification and adhesion in high-pressure areas near the exhaust port 133 and the screw stator 131.

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

[0036] Next, an amplifier circuit 150 that controls excitation of the upper radial electromagnets 104, the lower radial electromagnets 105, and the axial electromagnets 106A and 106B in the turbomolecular pump 100 will be described. A circuit diagram of this amplifier circuit is shown in FIG.

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

[0038] At this time, the transistor 161 has a diode cathode terminal 161a connected to the positive electrode 171a and an anode terminal 161b connected to one end of the electromagnet winding 151. The transistor 162 has a diode cathode terminal 162a connected to the current detection circuit 181 and an anode terminal 162b connected to the negative electrode 171b.

[0039] Meanwhile, the current regenerating diode 165 has its cathode terminal 165a connected to one end of the electromagnet winding 151 and its anode terminal 165b connected to the negative electrode 171b. Similarly, the current regenerating diode 166 has its cathode terminal 166a connected to the positive electrode 171a and its anode terminal 166b connected to the other end of the electromagnet winding 151 via a current detecting circuit 181. The current detecting circuit 181 is configured, for example, by 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 controlled in five axes and there are a total of ten electromagnets 104, 105, 106A, and 106B, a similar amplifier circuit 150 is configured for each electromagnet, and the ten 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 section (hereinafter referred to as a DSP section) not shown in the figure of the control device 200, and this amplifier control circuit 191 is configured to switch the transistors 161 and 162 on / off.

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

[0043] It is necessary to control the position of the rotor 103 at high speed and with strong force when, for example, the rotor 103 passes through a resonance point during acceleration of its rotational speed or when a disturbance occurs during constant-speed operation. For this reason, a high voltage of, for example, about 50 V 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 (not shown) is usually connected between the positive electrode 171a and the negative electrode 171b of the power supply 171 to stabilize the power supply 171.

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

[0045] Furthermore, when one of the transistors 161 and 162 is turned on and the other is turned 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, and the power consumption of the entire circuit can be kept low. Furthermore, by controlling the transistors 161 and 162 in this manner, high-frequency noise such as harmonics generated in the turbomolecular pump 100 can be reduced. Furthermore, 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] That is, when the detected current value is smaller than the current command value, both transistors 161 and 162 are turned on for a time period corresponding to a pulse width time Tp1 only once during a control cycle Ts (e.g., 100 μs), as shown in Fig. 3. Therefore, the electromagnet current iL during this period increases toward a current value iLmax (not shown) that can flow from the positive electrode 171a to the negative electrode 171b via the 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 for a time period corresponding to pulse width time Tp2 only once during the control cycle Ts, as shown in Fig. 4. Therefore, the electromagnet current iL during this period decreases toward a current value iLmin (not shown) that can be regenerated from the negative electrode 171b to the positive electrode 171a via diodes 165 and 166.

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

[0049] 1 (the side of the intake port 101) serves as an intake section connected to the target device, and the lower side (the side on which the exhaust port 15 constituting the exhaust port 133 is provided on the base portion 129 so as to protrude to the right in the figure) serves as an exhaust section connected to an auxiliary pump (back pump) or the like (not shown). The turbomolecular pump 100 can be used in an inverted, horizontal, or inclined position in addition to the vertical position shown in Figure 1.

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

[0051] The internal configuration of the main body casing of the turbomolecular pump 100 (here, a combination of the outer cylinder 127 and the base portion 129) can be divided into a rotation mechanism portion 136 that rotates the rotor shaft 113 and the like using the motor 121, and an exhaust mechanism portion 137 that is rotationally driven by the rotation mechanism portion 136. The exhaust mechanism portion 137 can also be divided into a turbomolecular pump mechanism portion 138 that is composed of the rotor blades 102, the fixed blades 123, and the like, and a thread groove pump mechanism portion (Hollweck type exhaust mechanism portion 204) that is composed of the rotor lower cylindrical portion 103b, the screw stator 131, and the like.

[0052] The aforementioned purge gas (protective gas) is used to protect the bearing parts, the rotor blades 102, etc., to prevent corrosion caused by the exhaust gas (process gas), and to cool the rotor blades 102. This purge gas can be supplied by a general method.

[0053] For example, the aforementioned purge gas port 132 extending linearly in the radial direction is provided at a predetermined position (such as a position 90 degrees or 120 degrees away from the exhaust port 133) of the base portion 129. Then, purge gas is 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 rate regulator (valve device).

[0054] The aforementioned protective bearings 120 are also called "touchdown (T / D) bearings," "backup bearings," etc. These protective bearings 120 prevent the position and attitude of the rotor shaft 113 from changing significantly, even in the unlikely event of a problem with the electrical system or atmospheric inrush, thereby preventing damage to the rotor blades 102 and their surrounding areas.

[0055] In FIG. 1 showing the structure of the turbo molecular pump 100 and the rotor 103, hatching showing cross sections of components is omitted to avoid cluttering the drawing.

[0056] <Configuration of Plasma Generating Unit 210> As described above, products may accumulate inside the turbomolecular pump 100. In this embodiment, the products are cleaned using a plasma generating unit 210 as shown in Figures 1 and 5(a) and (b).

[0057] Here, Fig. 5(a) is an enlarged view of the portion enclosed by frame A in Fig. 1, and also shows it schematically together with a plasma power supply unit 250 (described later). Fig. 5(b) is an enlarged view of the portion enclosed by frame B in Fig. 5(a). Note that hatching indicating cross sections of components has been omitted in Figs. 5(a) and 5(b) to avoid cluttering the drawings.

[0058] The plasma generating unit 210 is disposed inside the pressure vessel 100B (FIGS. 1 and 5(a)). The pressure vessel 100B corresponds to a case (also referred to as a "casing" or "main casing"). As described above, the pressure vessel 100B is configured by airtightly combining the outer cylinder 127 and the base 129.

[0059] The plasma generating unit 210 disposed inside the pressure vessel 100B is configured using the screw stator 131, the base portion 129, and the rotor lower cylindrical portion 103b. The plasma generating unit 210 further includes an inner stator 212.

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

[0061] As shown in cross section in Figures 5(a) and 5(b), a plurality of spiral thread grooves 131a are engraved on the inner peripheral surface of the screw stator 131. The thread grooves 131a are partitioned by protrusions 131b that protrude radially inward of the screw stator 131. The protrusions 131b are formed continuously within a predetermined angle (phase) range. The Holweck-type exhaust mechanism 204 constitutes a drag pump.

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

[0063] The flange portion 216 of the screw stator 131 is overlapped with the flange portion 218 of the base portion 129 via an insulating member 222 having electrical insulation properties. An insulating member 220 having electrical insulation properties is interposed between the flange portion 216 of the screw stator 131 and the head of the bolt 214. Ceramic (or synthetic resin, etc.) can be used as the material of the insulating members 220, 222. In this embodiment, a stainless steel hexagon socket head bolt 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. Such a coupling structure using the bolt 214 and the insulating members 220 and 222 is employed at multiple locations (e.g., about 3 to 8 locations) around the circumference of the flange portion 216 of the screw stator 131 at equal intervals.

[0065] The insulating member 220 may be cylindrical (collar-shaped) or annular (washer-shaped) and may be fitted to each bolt 214. The insulating member 220 may be annularly formed along the entire circumference of the flange portion 216 of the screw stator 131 and have a plurality of bolt holes (not shown) in number and arrangement corresponding to the plurality of 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 formed in a ring shape along the entire circumference of the flange portion 218 on the base portion 129 and have bolt holes (not shown) corresponding to multiple 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 flange portions 216, 218, but also between the inner periphery 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 cylindrical (collar-shaped) or annular (washer-shaped) and fitted to each bolt 214.

[0068] Next, a description will be given of the aforementioned inner stator 212. 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 rotor lower cylindrical portion 103b), and is disposed coaxially inside the screw stator 131 (and the rotor lower cylindrical portion 103b).

[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 peripheral surface of the inner stator 212 so as to protrude substantially vertically. The flange portion 236 of the inner stator 212 is overlapped with a flange portion 238 of the stator column 122 via an insulating member 242 having electrical insulation properties. The flange portion 238 of the stator column 122 is overlapped with the base portion 129 in a state of direct contact.

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

[0071] Bolt 234 is screwed into base portion 129 with insulating member 240, flange portion 236 of inner stator 212, and insulating member 242 sandwiched between the head and flange portion 238 of stator column 122. Such a coupling structure using bolt 234 and insulating members 240, 242 is employed at multiple locations (e.g., about 3 to 8 locations) circumferentially on flange portion 238 of stator column 122 at equal intervals.

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

[0073] Here, in the first embodiment, the inner stator 212 and the screw stator 131 are two (and two types of) stator parts (stator bodies) that make up the comprehensive stator part 226. The screw stator 131 is a stator part that is arranged outside the inner stator 212, and therefore can also be referred to as, for example, the "outer stator." Furthermore, the "inner stator" can be referred to as the "inner stator part," and the "outer stator" can be referred to as the "outer stator part."

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

[0075] The rotor lower cylindrical portion 103b 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 rotor 103 corresponds to the "rotor portion," and the rotor lower cylindrical portion 103b forms a part of the rotor 103 (rotor portion).

[0076] In the comprehensive stator portion 226, the inner stator 212 and the screw stator 131 (outer stator) face each other in the radial direction with the rotor lower cylindrical portion 103b sandwiched therebetween. Furthermore, an inner discharge gap 262 and an outer discharge gap 264 are formed between the outer peripheral surface of the inner stator 212 and the inner peripheral surface of the rotor lower cylindrical portion 103b, and between the outer peripheral surface of the rotor lower cylindrical portion 103b and the screw stator 131. The inner stator 212 and the screw stator 131 face each other with the inner discharge gap 262, the outer discharge gap 264, and the rotor lower cylindrical portion 103b sandwiched therebetween.

[0077] Of these, the outer peripheral surface of the inner stator 212 and the inner peripheral surface of the rotor lower cylindrical portion 103b are both formed into a curved surface, so that an inner discharge gap 262 between the inner stator 212 and the rotor lower cylindrical portion 103b is formed at a substantially uniform interval in the axial direction of the inner stator 212 (and the rotor lower cylindrical portion 103b).

[0078] Regarding the outer discharge gap 264, the outer peripheral surface of the rotor lower cylindrical part 103b is curved. However, since the inner periphery of the screw stator 131 has unevenness due to the protrusions 131b and the thread grooves 131a, the gap between the screw stator 131 and the rotor lower cylindrical part 103b varies partially and is not uniform.

[0079] Furthermore, the cross section of the protrusion 131b is tapered toward the tip. The tip of the protrusion 131b, which is sharper than the base end, faces closely to the lower rotor cylindrical portion 103b. In the first embodiment, the gap between the tip of the protrusion 131b and the outer peripheral surface of the lower rotor cylindrical portion 103b is the outer discharge gap 264.

[0080] Next, the aforementioned plasma power supply unit (hereinafter referred to as the "power supply unit") 250 will be described. As shown in Fig. 5(a), the power supply unit 250 is configured to include a first AC power supply unit 252, a second AC power supply unit 254, and a signal generator 256. As shown in Fig. 5(b), the first AC power supply unit 252 is electrically connected to the inner stator 212 and the base portion 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 portion 129 via a connector 258 and wiring 258b. The first AC power supply unit 252 and the second AC power supply unit 254 are connected to the base portion 129 so that the pressure vessel 100B has a reference potential (ground, GND), as shown in Fig. 5(a).

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

[0083] The first AC power supply unit 252 and the second AC power supply unit 254 output voltages of opposite phases to each other. The opposite phase voltages are output from a 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 to the inner stator 212 and the base portion 129 from the first AC power supply unit 252 and the second AC power supply unit 254 are set independently of each other. The applied voltages are set by a combination of a mechanical adjustment method and an electrical adjustment method.

[0085] The mechanical adjustment method is setting the balance related to the gap between the inner discharge gap 262 and the outer discharge gap 264 shown in FIG. 5B. The balance is set here so that the discharge amounts in the inner discharge gap 262 and the outer discharge gap 264 are as equal as possible (balanced). The mechanical adjustment method is performed by setting the gap between the inner discharge gap 262 and the outer discharge gap 264 at the mechanical design stage, adjusting the gap during assembly (balancing, adjusting using assembly tolerances), etc.

[0086] By balancing the discharge amounts, charging of the lower rotor cylindrical portion 103b can be avoided. As a result, the current flowing through the lower rotor cylindrical portion 103b approaches zero, reducing the amount of heat generated. After mechanically adjusting the inner discharge gap 262 and the outer discharge gap 264 shown in FIG. 5( b), the voltages applied to the inner stator 212 and the base portion 129 are set by an electrical adjustment method using an electric circuit (including an electronic circuit) to further fine-tune the balance of the discharge voltages. The signal generator 256 can be provided with a function for such an electrical adjustment method. More specifically, the signal generator 256 can be provided 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 to a position between the first AC power supply unit 252 and the second AC power supply unit 254 and the pressure vessel 100B.

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

[0089] <Function of Plasma Generator 210> In the vacuum exhaust apparatus 100A equipped with such a plasma generator 210, a source gas (also referred to as a "fuel gas") for plasma generation is introduced into the pressure vessel 100B. The source gas can be introduced, for example, by forming a source gas supply port (source gas supply passage, not shown) extending radially in the base portion 129 constituting the pressure vessel 100B, and introducing the source gas from outside the turbomolecular pump 100 into the Holweck-type exhaust mechanism 204 or into the inside of the rotor lower cylindrical portion 103b. Gases such as NF3 (nitrogen trifluoride) and CF4 (tetrafluoromethane) are used as the source gas.

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

[0091] Electric discharge occurs between the screw stator 131 (outer stator) and the lower cylindrical portion 103b of the rotor, and ions attracted to the applied voltage screw stator 131 collide with deposits at high speed, cleaning the deposits. Furthermore, electrically neutral radicals are also used together with the ions to clean the deposits. Therefore, not only radicals are utilized, but also plasma containing ions is effectively utilized, providing excellent cleaning properties.

[0092] Furthermore, protrusions 131b are provided on the opposing surfaces of the rotor section (rotating body 103) and the stator section (here, screw stator 131), thereby constituting a drag pump section (here, Holweck-type exhaust mechanism section 204). In general, deposits are likely to occur in drag pump sections such as the Holweck-type exhaust mechanism section 204. However, in the vacuum exhaust device 100A of the first embodiment, the rotor section (here, rotating body 103) and the stator section (here, screw stator 131) constitute discharge electrodes for generating plasma. Therefore, plasma is generated directly in the drag pump section.

[0093] Furthermore, the protrusions 131b of the screw stator 131 (outer stator) are tapered toward the tip. This allows electric charge to concentrate in a small area, making discharge more likely to occur. Furthermore, high-density discharge occurs, which cleans deposits. The degree of taper of the protrusions 131b is determined so as to make it easier for good discharge to occur. As mentioned above, even when the protrusions 131b are formed on the outer peripheral surface of the lower cylindrical portion 103b of the rotor, good discharge can be achieved by forming the protrusions 131b in a tapered shape.

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

[0095] In the first embodiment, the plasma generating unit 210 is provided with the 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 electrical insulating units (and second electrical insulating units). The insulating members 220, 222, 240, and 242 prevent unintended discharge due to charge accumulation in areas other than the plasma generating unit 210. Note that the term "second electrical insulating unit" is used to distinguish between application locations and structures, and the second electrical insulating unit may exist alone even if the first electrical insulating unit is not present.

[0096] Furthermore, in order to limit the location where discharge occurs to an intended range, it is conceivable to provide an electrically insulating portion by performing an electrical insulating treatment (ceramic coating, resin coating, or the like) on at least a part of the portion excluding the discharge gap portions (the inner discharge gap portion 262 and the outer discharge gap portion 264).

[0097] Specific examples of locations where an electrical insulating portion is provided by insulating treatment include areas of the screw stator 131 (outer stator) other than the protrusion 131b and the thread groove 131a (areas 272a to 272c (FIG. 5B) that do not face the rotor lower cylindrical portion 103b). Other examples include areas 274a to 274c (FIG. 5B) that do not face the rotor lower cylindrical portion 103b of the inner stator 212. Other examples include the lower end surface 276a of the rotor 103 (rotor portion), the intake-side step surface 276b, and the portion 276c adjacent to the turbomolecular pump mechanism 138.

[0098] Furthermore, it is conceivable that the rotor 103 may become charged and discharge due to the application of voltage to the inner stator 212 or the screw stator 131 (outer stator). Examples of locations where discharge may occur include a location between the rotor 102 and the stator 123, which are close to each other, and a location between the rotor 102 and the stator spacer 125.

[0099] More specifically, although reference numerals are omitted, examples of areas where discharges can occur include at least one of the blade surfaces, outer end surfaces, and base end surfaces of the rotor 102 and stator 123, areas between the individual rotors 102 (102a, 102b, 102c, etc.), and areas between the individual stator 123 (123a, 123b, 123c, etc.). Another example is the area between the outer end surfaces of the rotor 102 and the inner circumferential surface of the stator spacer 125. It is conceivable to provide these areas with electrical insulation using an insulating treatment (ceramic coating, resin coating, etc.).

[0100] Furthermore, the rotor shaft 113 of the rotor 103 can also be cited as a location where unintended discharges can occur. If no measures are taken, the charged area can expand from the rotor blades 102 and the rotor body 103a to the rotor shaft 113. Discharges at the rotor shaft 113 are thought to occur between the rotor shaft 113 and various electromagnets (upper radial electromagnets 104, lower radial electromagnets 105, and axial electromagnets 106A and 106B) and between the rotor shaft 113 and various bearings (protective bearing 120 and other bearings).

[0101] 1, it is conceivable to interpose insulating members 246, 248 having electrical insulation properties between the rotor main body 103a and the rotor shaft 113. Ceramic (or synthetic resin, etc.) can be used as the material for the insulating members 246, 248.

[0102] 1, the rotor shaft 113 is coaxially inserted into the rotor body 103a and connected to the rotor body 103a via a plurality of bolts 249 (only two are shown). In the first embodiment, stainless steel hexagon socket head bolts are used as the bolts 249. The bolts 249 are arranged at equal intervals in, for example, three to six locations.

[0103] The bolts 249 are screwed onto the rotor shaft 113 with insulating members 248 sandwiched between the heads and the rotor main body 103a. The insulating members 248 may be cylindrical (collar-shaped) or annular (washer-shaped) members combined with the individual bolts 249. Alternatively, the insulating member 248 may be annularly formed along the entire circumference of the rotor main body 103a and have a plurality of bolt holes (not shown) in the number and arrangement corresponding to the plurality of bolts 249. In the example of FIG. 1 , a plurality of annular (washer-shaped) members (only two are shown) are used as the insulating members 248.

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

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

[0106] As described above, the inner stator 212 and the screw stator 131 are radially opposed to each other across the lower rotor cylindrical portion 103b (which constitutes part of the rotor). This makes it easy to bring the inner stator 212 and the screw stator 131 close to each other. This makes it easy for polarization to occur in the lower rotor cylindrical portion 103b, and the current flowing in the lower rotor cylindrical portion 103b becomes regular. As a result, the current flowing in the lower rotor cylindrical portion 103b can be minimized. In other words, having the inner stator 212 and the screw stator 131 radially opposed to each other is more advantageous in terms of controlling (and managing) the current flowing in the lower rotor cylindrical portion 103b than having them shifted (offset) in the axial direction.

[0107] As a method of axially shifting (offsetting) the inner stator 212 and the threaded stator 131, a method of axially aligning them with an insulating member (electrical insulating part) interposed therebetween (not shown) 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). Furthermore, the two stator parts can be distinguished, for example, as the intake side and the exhaust side (distinguishing between the intake side stator part and the exhaust side stator part), rather than being distinguished as the inside and the outside.

[0108] However, arranging the two stator parts (the inner stator 212 and the screw stator 131) facing each other in the radial direction with the lower rotor cylindrical part 103b (part of the rotor) in between is more advantageous in terms of controlling (and managing) the current flowing through the lower rotor cylindrical part 103b than arranging them (offset) in the axial direction. For this reason, in the first embodiment, the two stator parts face each other in the radial direction with the lower rotor cylindrical part 103b in between, but the two stator parts may be offset in the axial direction if no particular problems arise.

[0109] Furthermore, as described above, the pressure vessel 100B is provided with a gas supply port (not shown) capable of supplying plasma raw material gas, allowing for a high degree of freedom in the placement of the gas supply port (not shown). Furthermore, the gas supply port (not shown) can be easily placed near the drag pump unit (here, the Holweck-type exhaust mechanism unit 204). The number of gas supply ports (not shown) may be either single or multiple. When a single gas supply port is used, it is easy to process the components that make up the pressure vessel 100B.

[0110] When a plurality of gas supply ports (not shown) are provided, the gas supply ports can be arranged at equal intervals (at intervals of 180 degrees, 120 degrees, 90 degrees, 45 degrees, 30 degrees, or the like) in the circumferential direction of the discharge gaps (the inner discharge gap 262 and the outer discharge gap 264). By providing a plurality of gas supply ports (not shown), the source gas can be supplied evenly (without unevenness or bias).

[0111] Furthermore, the two stator sections (inner stator 212 and screw stator 131) are electrically insulated from the pressure vessel 100B by insulating members 220, 222, 240, and 242. Furthermore, AC voltages are applied to the two stator sections by a power supply section 250 so that the voltages are in opposite phases. Furthermore, the two stator sections and the pressure vessel 100B are electrically connected so that the pressure vessel 100B has a reference potential. Voltage is then applied appropriately to the two stator sections.

[0112] In the first embodiment, the power supply unit 250 applies an AC voltage to the two stator units (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.

[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, a power supply circuit is configured to apply a negative voltage to the screw stator 131. Then, it is conceivable that discharge occurs from the screw stator 131 to the lower cylindrical portion 103b of the rotor, and from the lower cylindrical portion 103b to the inner stator 212. Then, it is conceivable that the applied voltages (V1, V2) of the DC power supply units (not shown) are adjusted depending on 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 mode is a relatively stable glow discharge, but when a DC voltage is applied, the discharge mode is a relatively unstable arc discharge. Furthermore, when an AC voltage is applied, high-density plasma is easily generated by utilizing frequency dependency. Furthermore, when an AC voltage is applied, high-density discharge can be generated at a lower voltage value than when a DC voltage is applied. Therefore, application of an AC voltage is more advantageous than application of a DC voltage. However, application of a DC voltage is also possible depending on the desired characteristics.

[0115] Furthermore, in the first embodiment, the voltages applied to the two stator parts (the inner stator 212 and the screw stator 131) can be set independently, and the amounts of discharge from the two stator parts to the rotor part (here, the lower cylindrical part 103b of the rotating body) can be adjusted to be equal. This allows the voltage to be applied more appropriately to the two stator parts.

[0116] The two stator portions (the inner stator 212 and the screw stator 131) can be divided into two types, for example, an outer stator portion and an inner stator portion. Alternatively, they can be divided into two types: a stator portion to which one voltage of two types of power supply portions (such as the first AC power supply portion 252 and the second AC power supply portion 254) having opposite phases is applied, and a stator portion to which the other voltage is applied. Therefore, the "two stator portions" can also be referred to as "two types of stator portions." It is also possible to provide multiple stator portions of each type.

[0117] <Typical Advantages of the Vacuum Exhaust Apparatus 100A According to the First Embodiment> The above-described vacuum exhaust apparatus 100A will be described below in comparison with the conventional technology shown in Figures 10(a) and 10(b). In Figures 10(a) and 10(b), the same components as those in the vacuum exhaust apparatus 100A of the first embodiment shown in Figures 1 to 5 are designated by the same reference numerals. Figure 10(a) shows a turbomolecular pump 600 (and vacuum exhaust apparatus 600A) of the conventional example.

[0118] In this conventional turbomolecular pump 600, a plurality of (here, two) plasma generators 610 are connected to the outer cylinder 127 via valve devices 614 and inlet pipes 616. This is similar to the invention disclosed in the aforementioned Patent Document 1.

[0119] However, the plasma generator 610 is disposed near the exhaust port 133 where deposits are likely to occur, 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. These advantages, compared to the invention disclosed in Patent Document 1, include the elimination of the need for a design that partially widens the gap between the rotor 102 and the stator 123, and the ability to supply radicals from a position closer to the deposits.

[0120] As with the conventional technology, in the vacuum exhaust device 100A of the embodiment shown in Figures 1 to 5, the plasma generation unit 210 is provided in the drag pump unit (Hollweck-type exhaust mechanism unit 204), where deposits are likely to occur. In the vacuum exhaust device 100A of the first embodiment, the inner stator 212 and the screw stator 131 (outer stator) are used as electrodes for generating plasma. Therefore, the vacuum exhaust device 100A is significantly smaller in size than the conventional technology shown in Figures 10(a) and 10(b).

[0121] Furthermore, according to the vacuum exhaust apparatus 100A of the first embodiment, plasma is generated in the drag pump unit (Hollweck-type exhaust mechanism unit 204), so that the plasma can be effectively used to perform cleaning in locations where deposits are likely to occur. Furthermore, a cleaning effect can be obtained by ions, which are active species that constitute the plasma. As a result, the cleaning effect can be improved compared to the prior art shown in FIGS. 10(a) and 10(b).

[0122] Furthermore, according to the vacuum exhaust device 100A of the first embodiment, the plasma generating unit 210 is built into the pressure vessel 100B, and voltage is applied in the circumferential direction by two electrode units (the inner stator 212 and the screw stator 131 (outer stator)). Therefore, the piping and wiring related to the supply of radicals can be consolidated, and the costs of the materials and work required for the wiring and piping can be reduced. Furthermore, the space required for the wiring and piping can be minimized. Furthermore, the structure of the plasma generating unit 210 can be simplified, and the plasma generating unit 210 can be made smaller. These factors make it possible to reduce the manufacturing costs of the vacuum exhaust device 100A. Furthermore, it becomes possible to increase the degree of freedom in installing the vacuum exhaust device 100A.

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

[0124] Furthermore, existing parts of the turbomolecular pump 100 (such as the rotor lower cylindrical portion 103b, the base portion 129, the screw stator 131, and the bolts 214, 234, and 249) can be used to form the plasma generating portion 210. This also contributes to cost reduction.

[0125] <Basic Configuration of Vacuum Exhaust Apparatus 300A According to Second Embodiment> Next, a description will be given of a vacuum exhaust apparatus 300A according to a second embodiment. Note that the same reference numerals are used to designate the same parts as those in the first embodiment, and descriptions thereof will be omitted as appropriate.

[0126] 6, 7A, and 7B show a vacuum exhaust device 300A according to the second embodiment. In the vacuum exhaust device 300A, the configuration of the plasma generation unit 310 of the turbomolecular pump 300 is different from that of the first embodiment. In the plasma generation unit 210 of the first embodiment, two (two types of) stator units are configured by a screw stator 131 (outer stator) and an inner stator 212. In contrast, in the second embodiment, two (two types of) stator units are configured by a screw stator 131 and a base unit 129. Here, in the second embodiment, the base unit 129 and the screw stator 131 are the two (two types of) stator units that configure the comprehensive stator unit 326.

[0127] 7B, an outer discharge gap 364 is formed between the protrusion 131b of the screw stator 131 and the inner circumferential surface of the rotor lower cylindrical portion 303b. In the second embodiment, an inner discharge gap 362 is formed between the rotor lower cylindrical portion 303b and the stator column 322. In the second embodiment, the inner corner (upper corner) of the rotor lower cylindrical portion 303b is thicker than the rotor lower cylindrical portion 103b of the first embodiment. The screw stator 131 and the stator column 322 face each other in the radial direction, sandwiching the inner discharge gap 362, the outer discharge gap 364, and the rotor lower cylindrical portion 303b therebetween.

[0128] Next, as shown in Fig. 7(a), 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 Fig. 7(b), the AC power supply unit 352 is electrically connected to the screw stator 131 and the base portion 129 via a connector 258 and wiring 358a, 358b. The base portion 129 is coupled to the stator column 322 so that electricity can be applied to the stator column 322.

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

[0130] Also, similar to the first embodiment, it is possible to provide an electrically insulating portion by performing an electrical insulating treatment (ceramic coating, resin coating, etc.) on at least a part of the portion excluding the inner discharge gap 362 and the outer discharge gap 364. The function of the gas supply port (not shown) is also similar to that of the first embodiment in that it can supply source gas to the inner discharge gap 362 and the outer discharge gap 364. Also similar to the first embodiment is that the power supply unit 350 applies an AC voltage.

[0131] <Typical Advantages of the Vacuum Exhaust Device 300A According to the Second Embodiment> According to the second embodiment, a vacuum exhaust device 300A that is compact and has excellent cleaning effects can be provided using a configuration similar to that of the first embodiment. Furthermore, the configurations of the plasma generating unit 310 and the power supply unit 350 can be simplified compared to the first embodiment. It is also possible to say that the vacuum exhaust device 300A according to the second embodiment is a device in which the inner stator 212 of the vacuum exhaust device 300A according to the first embodiment is integrated into the stator column 322.

[0132] <Basic Configuration of Vacuum Exhaust Apparatus 400A According to Third Embodiment> Next, a vacuum exhaust apparatus 400A according to a third embodiment will be described. Note that the same reference numerals are used to designate the same parts as those in the first and second embodiments, and descriptions thereof will be omitted as appropriate.

[0133] 8, 9A, and 9B show a vacuum exhaust apparatus 400A according to the third embodiment. In the vacuum exhaust apparatus 400A, a drag pump unit of a plasma generating unit 410 associated with a turbomolecular pump 400 is configured with a Sigbahn type exhaust mechanism 404, rather than the Holweck type exhaust mechanism 204 used in the first and second embodiments.

[0134] 9(a) and 9(b), in the Sigburn type exhaust mechanism 404, a plurality of spiral groove channels 414 separated by ridges 412 are formed in the gap between rotating disks 406a and 406b provided on the rotor 403 and fixed disks 410a and 410b fixed to the base 429. The Sigburn type exhaust mechanism 404 exhausts gas molecules by imparting tangential momentum to the gas molecules diffused in the spiral groove channels 414 through the rotating disks 406a and 406b, and by imparting preferential directionality in the exhaust direction through the spiral groove channels 414.

[0135] The ridges 412 and the spiral grooves 414 are provided on at least one of the rotating disks 406a and 406b and the fixed disks 410a and 410b. A general structure can be adopted for the Sigburn-type exhaust mechanism 404. In the third embodiment, the fixed disks 410a and 410b are two (two types of) stator portions that make up the comprehensive stator portion 426. The fixed disks 410a and 410b are included in the rotating body 403 (rotor portion).

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

[0137] The peaks 412 are tapered toward the tip, which causes electric charges to concentrate in a small area, making discharge more likely to occur. This is similar to the protrusions 131b in the first and second embodiments.

[0138] The plasma power supply unit (hereinafter referred to as "power supply unit") 450 according to the third embodiment may be similar to the power supply unit 250 according to the first embodiment. As shown in FIG. 9B, the power supply unit 450 is electrically connected to the fixed disks 410a and 410b via a connector 258 and wiring 458a and 458b. Reference numerals 470, 472, and 474 in FIG. 9B denote insulating members. Alternatively, the fixed disk 410b may be electrically connected to the base 129 without using the insulating member 474. It is also possible to employ a single AC power supply unit 352, as in the plasma power supply unit 350 according to the second embodiment (FIG. 7A). In this case, one wiring may be connected to either of the fixed disks (fixed disk 410a or fixed disk 410b) and the other wiring may be connected to the base 429.

[0139] Also, similar to the first and second embodiments, it is possible to provide an electrically insulating portion by performing an electrical insulating treatment (ceramic coating, resin coating, or the like) on at least a part of the portion excluding the first discharge gap 462, the second discharge gap 464, and the third discharge gap 466. The function of the gas supply port (not shown) is also similar to the first and second embodiments in that it can supply source gas to the first discharge gap 462, the second discharge gap 464, and the third discharge gap 466.

[0140] In this way, even in the vacuum exhaust apparatus 400A equipped with the Sigbahn type exhaust mechanism 404, it is possible to utilize a drag pump unit to configure the plasma generation unit 410. Also according to the third embodiment, it is possible to provide a vacuum exhaust apparatus 400A that is smaller in size and has an excellent cleaning effect compared to the conventional technology (FIGS. 10(a) and 10(b)) in which the plasma generation device is connected to the outside of the pressure vessel.

[0141] <Inventions Extractable from the Embodiments> The following inventions can be extracted from the above-described embodiments: (1) A vacuum exhaust device (vacuum exhaust device 100A, 300A, 400A, etc.) comprising: a pressure vessel (such as pressure vessel 100B), a rotor portion (such as rotating body 103, 403) rotatably held within the pressure vessel, and a first stator portion (such as screw stator 131 or fixed disk 410a) disposed within the pressure vessel opposite the rotor portion with a discharge gap portion (such as outer discharge gap portion 264, 364, first discharge gap portion 462, second discharge gap portion 464) interposed therebetween, wherein a voltage can be applied to the first stator portion. (2) The vacuum exhaust device according to (1) above, characterized in that protrusions (protrusions 131b, ridges 412, etc.) continuing at a predetermined angle in the circumferential direction are arranged on at least a part of the opposing surfaces of the rotor section and the first stator section, thereby forming a drag pump section (Hollweck-type exhaust mechanism section 204, Sigbahn-type exhaust mechanism section 404, etc.). (3) The vacuum exhaust device according to (2) above, characterized in that the protrusions are formed in a tapered shape narrowing toward the tip. (4) The vacuum exhaust device according to (1) above, characterized in that the rotor section includes a rotor main body section (rotating body main body 103a, etc.) and a rotor shaft section (rotor shaft 113, etc.), and a first electrical insulating section (insulating member 246, 248, etc.) is provided between the rotor main body section and the rotor shaft section. (5) The vacuum exhaust device according to (1) above, characterized in that an electrical insulating part (insulating members 220, 222, 240, 242, 246, 248, 470, 472, 474, an insulated part, etc.) is provided on at least a part of the part excluding the part facing the discharge gap. (6) The vacuum exhaust device according to (4) above, characterized in that a second electrical insulating part (insulating members 220, 222, 240, 242, 470, 472, 474, an insulated part, etc.) is provided on at least a part of the part excluding the part facing the discharge gap. (7) The vacuum exhaust device according to any one of (1) to (4) above, characterized in that the pressure vessel is provided with a gas supply port capable of supplying a plasma raw material gas.(8) The vacuum exhaust device according to any one of (1) to (6) above, characterized in that a second stator portion (inner stator 212, stator column 122, fixed disk 410a, etc.) is provided facing the first stator portion across the rotor portion (lower cylindrical portion 103b, 303b of rotor 103, rotating disk 406a, 406b of rotor 403, etc.). (9) The vacuum exhaust device according to (8) above, characterized in that the first stator portion and the second stator portion are electrically insulated from the pressure vessel, AC voltages are applied to the first stator portion and the second stator portion so that the first stator portion and the second stator portion are in opposite phase, and the first stator portion, the second stator portion, and the pressure vessel are electrically connected so that the pressure vessel has a reference potential. (10) The vacuum exhaust device described in (9) above, characterized in that the AC voltages applied to the first stator section and the second stator section can be set independently of each other and can be adjusted so that the amounts of discharge from the first stator section and the second stator section to the rotor section are equal.

[0142] <Others> The present invention is not limited to the above-described embodiments, and various modifications and combinations of the embodiments are possible without departing from the gist of the present invention.

[0143] DESCRIPTION OF SYMBOLS 100A, 300A, 400A: Vacuum exhaust device 100B: Pressure vessel 100, 300, 400: Turbo molecular pump 102: Rotor 103, 403: Rotor 103a, 303b: Rotor body 103b: Lower cylindrical portion of rotor 113: Rotor shaft 122, 322: Stator column 123: Fixed blade 125: Fixed blade spacer 127: Outer cylinder 129, 429: Base portion 131: Threaded stator 131a: Thread groove 131b: Projection portion 200: Control device 204: Holweck type exhaust mechanism portion 210, 310, 410: Plasma generating portion 212: Inner stator 220, 222, 240, 242, 246, 248, 470, 472, 474: insulating members 226, 326, 426: comprehensive stator portion 250, 350, 450: plasma power supply portion 252: first AC power supply portion 254: second AC power supply portion 256: signal generator 258: connector 258a, 258b, 358a, 358b, 458a, 458b: wiring 262, 362: inner discharge gap portion 264, 364: outer discharge gap portion 352: AC power supply portion 404: Sigbahn type exhaust mechanism portion 406a, 406b: rotating disk 410a, 410b: fixed disk 412: ridge portion (projection portion) 414 462: First discharge gap portion 464: Second discharge gap portion 466: Third discharge gap portion

Claims

1. A vacuum exhaust device comprising: a pressure vessel; a rotor portion rotatably held within the pressure vessel; and a first stator portion disposed within the pressure vessel opposite the rotor portion across a discharge gap, wherein a voltage can be applied to the first stator portion.

2. The vacuum exhaust device according to claim 1, characterized in that a drag pump section is formed by arranging continuous protrusions at a predetermined angle in the circumferential direction on at least a portion of the opposing surfaces of the rotor section and the first stator section.

3. The vacuum exhaust device according to claim 2, characterized in that the protrusion is formed in a tapered shape narrowing toward the tip.

4. The vacuum exhaust device according to claim 1, characterized in that the rotor section comprises a rotor body section and a rotor shaft section, and a first electrical insulating section is provided between the rotor body section and the rotor shaft section.

5. The vacuum exhaust device according to claim 1, characterized in that an electrical insulating section is provided on at least a part of the section excluding the section facing the discharge gap section.

6. The vacuum exhaust device according to claim 4, wherein a second electrical insulating portion is provided on at least a portion of the device excluding the portion facing the discharge gap.

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

8. The vacuum exhaust device according to any one of claims 1 to 6, characterized in that a second stator section is provided facing the first stator section across the rotor section.

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

10. The vacuum exhaust device according to claim 9, characterized in that the AC voltages applied to the first stator section and the second stator section can be set independently and are adjustable so that the amounts of discharge from the first stator section and the second stator section to the rotor section are equal.

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