Vacuum pump

Abstract

A vacuum pump of the present application is provided with a housing (11), a stator (17) disposed on the inner side of the housing (11), a cylindrical rotor (18) having a shaft (20) rotatably supported with respect to the stator (17) and rotatably built in the housing (11) together with the shaft (20), characterized in that, in the housing (11), an electrode portion (36A) that is a part of a radical generating device (10C) that generates radicals is disposed.

Description

Technical Field

[0001] This invention relates to vacuum pumps, and more particularly to vacuum pumps capable of eliminating deposits and the like formed by gas solidification within the vacuum pump. Background Technology

[0002] In recent years, in the process of forming semiconductor devices from wafers that serve as substrates, a method has been adopted to fabricate semiconductor devices by processing the wafers in a processing chamber of a semiconductor manufacturing apparatus that maintains a high vacuum. In the semiconductor manufacturing apparatus that processes the wafers in a vacuum chamber, a vacuum pump equipped with a turbomolecular pump section and a grooved pump section is used to maintain a high vacuum level (for example, see Patent Document 1).

[0003] The turbomolecular pump section has a thin, rotatable metal rotor blade inside the casing and a stator blade fixed at the casing. The rotor blade is rotated at a high speed, for example, several hundred meters per second, compressing the process gas entering from the intake side and expelling it from the exhaust side.

[0004] However, process gas molecules entering from the vacuum pump's intake side collide with stator blades as they travel towards the exhaust port due to the movement of the rotating blades, resulting in adsorption and accumulation on the stator blades and the inner surface of the casing. This accumulation on the stator blades and the inner surface of the casing obstructs the path of gas molecules towards the exhaust port. Consequently, problems arise such as a decrease in the turbomolecular pump's exhaust capacity, abnormal processing pressure, and decreased production efficiency due to interruptions in the processing of accumulated deposits.

[0005] In addition, there is a problem of deposits peeling off from the stator wings and inner surface of the cover flowing back into the processing chamber of the semiconductor manufacturing device and contaminating the wafers.

[0006] As a countermeasure, a vacuum pump with a free radical supply device installed at the suction port of the vacuum pump has also been proposed. The aforementioned free radical supply device generates free radicals that will peel off and decompose deposits that have been adsorbed and accumulated on the stator blades, inner surface of the cover, etc. (for example, see Patent Document 2).

[0007] The technology known in Patent Document 2 is to provide a free radical supply section near the intake port of the vacuum pump, and to supply free radicals by spraying them from the nozzle of the free radical supply section toward the inner center.

[0008] Patent document 1: Japanese Patent Application Publication No. 2019-82120.

[0009] Patent Document 2: Japanese Patent Application Publication No. 2008-248825.

[0010] The invention described in Patent Document 2 employs a structure in which free radicals from a free radical supply unit are ejected from a nozzle located near the intake port and supplied towards the inner center. Furthermore, the free radicals supplied from the free radical supply unit flow together with the process gas inside the shroud towards the exhaust port, where they decompose adsorbed deposits on the stator blades, the inner surface of the shroud, etc., and are discharged from the exhaust port along with the process gas. These free radicals exert high energy on the feed gas, acting as unstable substances that forcibly separate molecular bonds, and therefore recombine and lose their activity within a relatively short time. Therefore, even when supplied from the vacuum pump's intake port, the free radicals recombine and lose their activity before reaching the vicinity of the vacuum pump's exhaust port due to collisions with each other, with the stator blades, and the shroud.

[0011] On the other hand, process gases mainly accumulate near the exhaust port of the vacuum pump, so there is a problem that even if free radicals are supplied to the vicinity of the intake port, they cannot be effectively cleaned.

[0012] Furthermore, when a radical supply section is located near the vacuum pump's intake port, the structure that supplies radicals by ejecting them from the nozzle towards the center of the supply section prevents the radicals from flowing uniformly throughout the process gas path. That is, radicals are adequately supplied near the nozzle outlet, resulting in effective cleaning, but the supply is insufficient at the point away from the nozzle outlet, hindering cleaning. Therefore, even when guided circumferentially by a manifold, the radicals recombine within the manifold, reducing cleaning effectiveness. Consequently, to clean the entire vacuum pump, multiple nozzles in the radical supply section need to be arranged side-by-side circumferentially, which also incurs costs. Summary of the Invention

[0013] Therefore, a technical problem arises that needs to be solved in order to provide a vacuum pump that can effectively remove deposits by means of free radical decomposition, and the present invention aims to solve this problem.

[0014] The present invention was proposed to achieve the above-mentioned objective. The invention described in technical solution 1 provides a vacuum pump, which includes a cover, a stator, and a rotor. The stator is disposed inside the cover, and the rotor has a shaft that is rotatably supported relative to the stator and is rotatably housed in the cover together with the shaft. The rotor is cylindrical. The vacuum pump is characterized in that at least one pair of electrodes for generating free radicals are disposed inside the cover.

[0015] According to this structure, at least a pair of electrodes of a free radical generating device are disposed inside the casing. The pair of electrodes generate free radicals inside the casing that decompose the deposits accumulated inside the casing. Furthermore, when the free radicals generated inside the casing come into contact with the deposits, the molecular chains on the surface of the deposits are broken, and the deposits decompose into low-molecular-weight gases. In addition, the low-molecular-weight gases are transferred to the exhaust port of a vacuum pump and effectively discharged to the outside from the exhaust port of the vacuum pump.

[0016] Furthermore, by placing at least one pair of electrodes of the free radical generator inside the enclosure at a location where process gases are prone to accumulate, the accumulation can be effectively decomposed and discharged to the outside.

[0017] The invention described in technical solution 2 provides a vacuum pump, which, in the structure described in technical solution 1, further includes a power source for applying a high-frequency voltage to the aforementioned electrodes.

[0018] According to this structure, at least one pair of electrodes is disposed in the passage through which the process gas passes within the enclosure. If a high-frequency voltage is applied between these electrodes from a power source, free radicals can be effectively generated in the passage through which the process gas passes within the enclosure. Furthermore, the power source can also be disposed on either the outer or inner side of the enclosure.

[0019] The invention described in technical solution 3 provides a vacuum pump in which, in the structure described in technical solution 1 or 2, the aforementioned electrodes are configured such that a plurality of cylindrical plates are arranged concentrically and at approximately equal intervals with the axis center of the aforementioned shaft.

[0020] According to this structure, if the plates of the electrodes for generating free radicals in the free radical generator are cylindrical, and multiple cylindrical plates are formed by varying their diameters, and these cylindrical plates are arranged concentrically and at approximately equal intervals with the axis center of the shaft, and configured to cross the entire passage through which the process gas passes within the enclosure, then the electrodes of the free radical generator can be arranged approximately evenly throughout the entire passage through which the process gas passes within the enclosure. As a result, free radicals are generated approximately evenly throughout the entire passage through which the process gas passes within the enclosure, making overall contact with the deposits accumulated within the enclosure, thus enabling effective cleaning. Furthermore, by making the multiple electrodes of the free radical generator cylindrical and arranging them to cross the entire passage through which the process gas passes within the enclosure, the space occupied by the free radical generator within the enclosure can be reduced and made more compact, thereby enabling miniaturization of the vacuum pump.

[0021] The invention described in technical solution 4 provides a vacuum pump, which, in the structure described in any one of technical solutions 1 to 3, includes a turbomolecular pump section. The turbomolecular pump section is configured to provide a plurality of rotating blades protruding from the outer periphery of the rotor and to provide stator blades. The stator blades are axially separated from the rotating blades, protruding from the inner periphery of the cover and arranged to face the rotating blades.

[0022] According to this structure, a vacuum pump equipped with a turbine molecular section is obtained that can effectively decompose and discharge the accumulation of process gases generated inside the shroud.

[0023] The invention described in technical solution 5 provides a vacuum pump, which, in the structure described in any one of technical solutions 1 to 4, further includes a threaded groove pump section, wherein the threaded groove pump section is configured such that a spiral or vortex-shaped threaded groove is provided on at least one of the outer peripheral portion of the rotor and the inner peripheral portion of the stator.

[0024] According to this structure, a vacuum pump having a threaded groove pump section or having both a threaded groove pump section and a turbine section can be obtained, which can effectively decompose and discharge the accumulation of process gases generated inside the shroud.

[0025] The invention described in technical solution 6 provides a vacuum pump, which, in the structure described in any one of technical solutions 1 to 3, includes a turbomolecular pump section and a grooved pump section. The turbomolecular pump section is configured to have a plurality of rotating blades protruding from the outer periphery of the rotor and stator blades. The stator blades are axially separated from the rotating blades and protrude from the inner periphery of the cover, and are arranged to face the rotating blades. The grooved pump section is configured to have helical or vortex-shaped grooves provided on at least one of the outer periphery of the rotor and the inner periphery of the stator. The electrode is provided at the boundary between the turbomolecular pump section and the grooved pump section.

[0026] According to this structure, the electrodes of the free radical generator are set at the boundary between the turbomolecular pump section and the aforementioned grooved pump section. As a result, the process gas deposits that accumulate around the boundary between the turbomolecular pump section and the grooved pump section can be effectively decomposed and discharged to the outside, thereby achieving cleaning.

[0027] The invention described in technical solution 7 provides a vacuum pump in which, in the structure described in any one of technical solutions 1 to 6, the aforementioned electrode is positioned closer to the suction port side than the aforementioned rotor.

[0028] According to this structure, by arranging the electrodes of the free radical generator on the side closer to the intake port than the rotor, a larger space can be provided for arranging the electrodes of the free radical generator, allowing for the placement of more electrodes for free radical generation. This enables the generation of more free radicals, thereby effectively decomposing the accumulated material and discharging it to the outside, thus achieving cleaning.

[0029] The invention described in technical solution 8 provides a vacuum pump in which, in the structure described in any one of technical solutions 1 to 7, the aforementioned electrode is disposed at the axial middle position of the aforementioned rotor.

[0030] According to this structure, by placing the electrodes of the free radical generator at the axial center of the rotor, the process gas entering from the intake port can effectively remove the deposits accumulated around the axial center position inside the casing. Free radicals are unstable substances that are forcibly pulled apart by applying high energy to the feed gas molecules. Therefore, they have the disadvantage of recombining and losing activity within a relatively short time. On the other hand, the process gas mainly accumulates near the exhaust port inside the casing. Therefore, even if free radicals are supplied to the vicinity of the intake port, cleaning may not be effective. However, in this structure, by placing the electrodes, which are part of the free radical generator, at the axial center of the stator, the process gas deposits accumulated near the exhaust port can be effectively decomposed and discharged to the outside, thereby achieving cleaning.

[0031] The invention described in technical solution 9 provides a vacuum pump, which, in the structure described in any one of technical solutions 1 to 8, has a flushing gas supply port provided in the aforementioned shroud at a position upstream of the aforementioned electrode.

[0032] According to this structure, if flushing gases such as O2 (oxygen) and NF3 (nitrogen trifluoride) flow from the flushing gas supply port located upstream of the electrode of the radical generator, O (oxygen) radicals and F (fluorine) radicals are generated. These generated O and F radicals can decompose the process gas deposits into low-molecular-weight gases, which are then discharged to the outside through the exhaust port. This further reduces the amount of deposits accumulating inside the enclosure.

[0033] The invention described in technical solution 10 provides a vacuum pump, which, in the structure described in any one of technical solutions 1 to 9, has a control unit that can switch the rotor to rated rotation or low-speed rotation at a speed lower than the rated speed.

[0034] According to this structure, when flushing gases such as O2 and NF3 are supplied to generate O radicals and F radicals, there is a possibility of backflow of flushing gases. However, if the rotor is rotated at a low speed, it is possible to prevent the gasified flushing gases such as O radicals and F radicals from backflowing to the device side such as the sealed cavity connected to the intake side, and to prevent the device connected to the intake side from being corroded by the flushing gases.

[0035] Invention Effects

[0036] According to the present invention, deposits accumulated inside the shroud can be effectively discharged to the outside from the exhaust port of the vacuum pump by decomposing them into low molecular weight gases using free radicals. Furthermore, if at least the electrodes of the free radical generator are located at the site of deposits that easily generate process gases inside the shroud, the deposits can be decomposed and discharged more effectively, thus reducing the amount of deposits accumulating inside the shroud. This extends the pump's maintenance interval. Consequently, the frequency of removing the vacuum pump from the vacuum chamber for repair can be reduced, leading to increased productivity in semiconductor, flat panel, and other manufacturing equipment. Attached Figure Description

[0037] Figure 1 This is a schematic longitudinal sectional side view of a vacuum pump according to an embodiment of the present invention.

[0038] Figure 2 This diagram shows an example of the electrode structure of a free radical generator installed inside the casing of the aforementioned vacuum pump. Figure 2 (a) is a top view of the electrode structure. Figure 2 (b) is Figure 2 (a) is a cross-sectional view along line AA.

[0039] Figure 3 Is as Figure 1 The other variations of the vacuum pump shown in the figure are schematic longitudinal sectional side views of the vacuum pump.

[0040] Figure 4 Is as Figure 1 The above-described vacuum pump is shown in a schematic longitudinal sectional side view, representing another variation of the vacuum pump. Detailed Implementation

[0041] In order to achieve the objective of providing a vacuum pump capable of effectively removing deposits by means of free radical decomposition, the present invention is achieved by the following structure: the vacuum pump includes a shroud, a stator, and a rotor; the stator is disposed inside the shroud; the rotor has a shaft that is rotatably supported relative to the stator and is rotatably housed within the shroud together with the shaft; the rotor is cylindrical; and the vacuum pump is characterized in that at least one pair of free radical generating electrodes are disposed inside the shroud. Example

[0042] Hereinafter, an embodiment of the present invention will be described in detail based on the accompanying drawings. Furthermore, in the following embodiments, when the quantity, value, amount, range, etc., of the constituent elements are mentioned, they are not limited to that specific quantity, except where specifically stated or clearly limited in principle to a particular quantity; they may be more than or less than that specific quantity.

[0043] Furthermore, when referring to the shape and positional relationship of constituent elements, etc., except for cases that are specifically stated or are obviously not so in principle, it includes shapes that are substantially similar to or analogous to that shape.

[0044] Furthermore, the accompanying drawings may exaggerate features by enlarging them for easier understanding, and the size ratios of the constituent elements are not necessarily the same as actual dimensions. Additionally, in sectional views, some section lines of the constituent elements may be omitted for easier understanding of their cross-sectional structure.

[0045] Furthermore, in the following description, expressions indicating directions such as up / down and left / right are not absolute and should be interpreted as appropriate when describing the posture of various parts of the vacuum pump of the present invention, but changing accordingly when the posture changes. Additionally, the same reference numerals are used to denote the same elements throughout the description of the embodiments.

[0046] Figure 1 This is a schematic longitudinal sectional side view showing a vacuum pump 10 as an embodiment of the present invention. In the following description, Figure 1 The up and down directions are used to describe the up and down of the vacuum pump.

[0047] Figure 1 The vacuum pump 10 shown is a composite pump (also called a "turbomolecular pump") comprising a turbomolecular pump section 10A, a grooved pump section 10B, and a free radical generator 10C as a gas exhaust mechanism. The vacuum pump 10 is used, for example, as a gas exhaust mechanism for process chambers in semiconductor manufacturing apparatuses, flat panel display manufacturing apparatuses, solar panel manufacturing apparatuses, and other sealed chambers. Furthermore, the overall operation is based on the process operation determined by the control unit 10D.

[0048] The vacuum pump 10 includes a cover 11, which encloses and houses at least a portion of the turbomolecular pump section 10A and the grooved pump section 10B that perform exhaust functions, as well as the free radical generating device 10C that decomposes the deposits accumulated inside the vacuum pump 10 and discharges them.

[0049] The cover 11 arranges the cylindrical pump casing 11A, pump base 11B, and base end cover 11C along its cylindrical axis. The pump casing 11A and pump base 11B are connected by a fastening connection member 12A, and the pump base 11B and base end cover 11C are connected by mounting bolts 12B, thereby forming a bottomed, generally cylindrical shape.

[0050] The upper end side of pump casing 11A ( Figure 1 The upper part (top of the paper) serves as the intake port 13A. Furthermore, a first flushing gas supply port 14A, communicating with the electrode section 36A of the free radical generator 10C, is provided on the circumferential surface of the upper end. A flange 15A is formed at the intake port 13A. The flange 15A of the intake port 13A is connected, for example, to a high-vacuum, sealed cavity (not shown) such as the process chamber of a semiconductor manufacturing apparatus. A bolt hole 37 (not shown) for bolt insertion and an annular groove 38 for mounting and maintaining the airtightness between the flange and the sealed cavity side are formed at this flange 15A.

[0051] On the other hand, the flange 15B of the first flushing gas supply port 14A is connected to a flushing gas supply device (not shown in the figure). Furthermore, flushing gases such as O2 (oxygen) and NF3 (nitrogen trifluoride) are supplied from the flushing gas supply device to the first flushing gas supply port 14A.

[0052] On the other hand, an exhaust port 13B and a second flushing gas supply port 14B are provided at the pump base 11B. A flange 16A is provided at the exhaust port 13B, and a flange 16B is provided at the second flushing gas supply port 14B. Furthermore, the flange 16A of the exhaust port 13B is connected to an auxiliary pump (not shown in the figure). The flange 16B of the second flushing gas supply port 14B is connected to an auxiliary pump other than the auxiliary pump connected to the first flushing gas supply port 14A. For example, inactive gases such as N2 (nitrogen) gas and Ar (argon) gas flow from the second flushing gas supply port 14B. The second flushing gas supply port 14B communicates with the interior of the fixing column 35 (described later), supplying flushing gas to the electrical component housing 35a (the cylindrical interior of the fixing column 35) of the fixing column 35. This serves to protect the electrical components from corrosive gases, which may be contained in process gases discharged from the sealed chamber connected to the vacuum pump 10.

[0053] in addition, Figure 1 In the embodiment shown, the vacuum pump 10 is configured to be arranged vertically, but it is also possible to place the vacuum pump 10 horizontally and install it in the lateral direction of the sealed cavity, or to install the suction port 13A on the lower side in the upper part of the sealed cavity.

[0054] If we describe the structure of the vacuum pump 10 in more detail, the components that perform the exhaust function are generally composed of a stator 17 fixed inside the cover 11 and a rotor 18 that is rotatable relative to the stator 17.

[0055] The rotor 18 consists of a rotating blade 19 and a shaft 20, etc.

[0056] The rotating blade 19 has a cylindrical component 21, which is configured to integrally form a first cylindrical portion 21a disposed on the intake port 13A side (turbomolecular pump section 10A) and a second cylindrical portion 21b disposed on the exhaust port 13B side (threaded groove pump section 10B).

[0057] The first cylindrical section 21a is a generally cylindrical component that constitutes the rotating blade section of the turbomolecular pump section 10A. On the outer peripheral surface of the first cylindrical section 21a, i.e., the outer peripheral surface of the rotor 18, a plurality of rotating blades 22 extending radially outward from the axis parallel to the center of the rotating blade 19 and the shaft 20 are arranged at approximately equal intervals in the rotational direction. Furthermore, each rotating blade 22 is inclined in the same direction at a predetermined angle relative to the horizontal direction. Moreover, in the first cylindrical section 21a, these radially extending plurality of rotating blades 22 are arranged in multiple layers at predetermined intervals in the axial direction.

[0058] Furthermore, a partition wall 23 for engaging with the shaft 20 is formed at the axial center of the first cylindrical portion 21a. At the partition wall 23, a shaft hole 23a for inserting the upper end of the shaft 20 for mounting, and a bolt hole (not shown in the figure) for mounting bolts 24 for fixing the shaft 20 and the rotating blade 19 are formed.

[0059] The second cylindrical part 21b is a component with a cylindrical outer surface, which constitutes the rotating blade part of the threaded groove pump part 10B.

[0060] Shaft 20 is a cylindrical component constituting the shaft of rotor 18. At its upper end, a protruding edge 20a is integrally formed, which is threadedly fixed to the partition wall 23 of the first cylindrical portion 21a via mounting bolt 24. Furthermore, after the upper end of shaft 20 is inserted into shaft hole 23a from the inside (lower side) of the first cylindrical portion 21a until the protruding edge 20a abuts against the lower surface of partition wall 23, mounting bolt 24 is threaded through bolt hole (not shown) from the upper surface side of partition wall 23 and fixed to mounting hole of protruding edge 20a, thereby fixing it integrally with cylindrical component 21.

[0061] Furthermore, at the axial center of shaft 20, a permanent magnet is fixed to the outer peripheral surface, forming the rotating part of motor section 25. The magnetic poles formed by this permanent magnet on the outer periphery of shaft 20 are N poles on half of the outer peripheral surface and S poles on the remaining half.

[0062] Furthermore, on the upper end side (intake port 13A side) of the shaft 20, a portion of the radial magnetic bearing portion 26 on the rotor 18 side is formed to support the shaft 20 radially relative to the motor portion 25. On the lower end side (exhaust port 13B side), a portion of the radial magnetic bearing portion 27 on the rotor 18 side is also formed to support the shaft 20 radially relative to the motor portion 25. In addition, at the lower end of the shaft 20, a portion of the axial magnetic bearing portion 28 on the rotor 18 side is formed to support the shaft 20 axially (in the thrust direction).

[0063] Furthermore, near the radial magnetic bearing portions 26 and 27, radial displacement sensors 29 and 30 are formed on the rotor 18 side, respectively, which can detect the radial displacement of the shaft 20.

[0064] The rotating parts of these radial magnetic bearing sections 26, 27 and radial displacement sensors 29, 30 are constructed of stacked steel plates with steel plates stacked in the axial direction of the rotor 18. This is to prevent eddy currents from being generated at the shaft 20 due to the magnetic field generated by the windings of the rotor 18-side parts constituting the radial magnetic bearing sections 26, 27 and radial displacement sensors 29, 30.

[0065] Rotor 19 is made of metals such as stainless steel and aluminum alloy.

[0066] A stator 17 is formed on the inner circumferential side of the cover 11. The stator 17 is composed of a stator wing 31 and spacer 34 provided on the intake port 13A side (turbomolecular pump section 10A side), a threaded groove spacer 32 provided on the exhaust port 13B side (threaded groove pump section 10B side), a fixing member for the motor section 25, fixing members for the radial magnetic bearing sections 26 and 27, a fixing member for the axial magnetic bearing section 28, fixing members for the radial displacement sensors 29 and 30, and a fixing post 35.

[0067] The stator airfoil 31 is inclined at a predetermined angle from a plane perpendicular to the axis of the shaft 20, and is composed of stator airfoil blades 33 extending from the inner circumference of the cover 11 towards the shaft 20. Furthermore, at the turbomolecular pump section 10A, the stator airfoil 31 has multiple layers of stator airfoil blades 33 alternating with the rotating airfoil blades 22 of the rotating blade 19 in the axial direction. The stator airfoil blades 33 in each layer are separated from each other by means of cylindrical spacers 34.

[0068] The threaded groove spacer 32 is a cylindrical component with a helical groove 32a formed on its inner circumferential surface. The inner circumferential surface of the threaded groove spacer 32 faces the outer circumferential surface of the second cylindrical portion 21b of the cylindrical component 21 through a predetermined gap. The direction of the helical groove 32a formed at the threaded groove spacer 32 is towards the exhaust port 13B when gas is conveyed within the helical groove 32a in the rotational direction of the rotor 18. The depth of the helical groove 32a becomes shallower as it approaches the exhaust port 13B, and the gas conveyed in the helical groove 32a is compressed as it approaches the exhaust port 13B.

[0069] The stator wings 31 and the threaded groove spacers 32 are made of metals such as stainless steel and aluminum alloy.

[0070] The pump base 11B is a generally short cylindrical component with a centrally located opening 39 extending vertically. On the upper surface of the pump base 11B, a cylindrical retaining post 35 is inserted into the opening 39 at its lower end and engaged, with the upper surface facing the intake port 13A and concentrically mounted with the central axis of the stator 17. The retaining post 35 supports the retaining sides of the motor section 25, radial magnetic bearing sections 26 and 27, and radial displacement sensors 29 and 30. On the lower surface of the pump base 11B, a base end cover 11C is mounted integrally with the pump base 11B using mounting bolts 12B. That is, the base end cover 11C, along with the pump housing 11A and the pump base 11B, forms a cover 11.

[0071] In the motor section 25, a predetermined number of fixed member windings are arranged at equal intervals on the inner circumference side of the fixed member windings, which can generate a rotating magnetic field around the magnetic poles formed on the shaft 20.

[0072] The radial magnetic bearing sections 26 and 27 are composed of windings arranged at 90-degree intervals around the axis of rotation. The radial magnetic bearing sections 26 and 27 attract the shaft 20 by means of the magnetic field generated by these windings, thereby magnetically suspending the shaft 20 in the radial direction.

[0073] An axial magnetic bearing portion 28 is formed at the bottom of the fixing post 35. The axial magnetic bearing portion 28 consists of a circular plate extending from the shaft 20 and windings arranged above and below the circular plate. The magnetic field generated by these windings attracts the circular plate, thereby magnetically suspending the shaft 20 in the axial direction.

[0074] Free radical generator 10C, such as Figure 1 As shown, the boundary between the turbomolecular pump section 10A and the threaded groove pump section 10B is located at the axial midpoint of the rotor 18 disposed inside the cover 11.

[0075] The free radical generator 10C includes an electrode section 36A and a power supply 36B. The power supply 36B of the free radical generator 10C applies a high-frequency voltage to the electrodes 36a1, 36a2, 36a3, 36a4, and 36a5 of the electrode section 36A of the free radical generator 10C; in some cases, it is located on the outside of the cover 11. The voltage applied by the power supply 36B causes different positive and negative electrodes to be generated on adjacent electrodes 36a1, 36a2, 36a3, 36a4, and 36a5.

[0076] On the other hand, the electrode section 36A of the free radical generator 10C, as in Figure 2 (a) shows its top view, and furthermore, as in Figure 2 (b) represents the AA line section of (a) in the view. Figure 1 As shown in the AA-line cross-sectional view, the device comprises multiple (five in this embodiment) electrodes 36a1, 36a2, 36a3, 36a4, and 36a5, each made of cylindrical plates. The electrodes 36a1, 36a2, 36a3, 36a4, and 36a5 sequentially change the diameter of each cylinder at approximately equal ratios, and are arranged concentrically and at approximately equal intervals with respect to the axis center of shaft 20. Therefore, the gaps between electrodes 36a1 and 36a2, between electrodes 36a2 and 36a3, between electrodes 36a3 and 36a4, and between electrodes 36a4 and 36a5 are approximately equal. Furthermore, among the electrodes 36a1, 36a2, 36a3, 36a4, and 36a5, the innermost electrode 36a1 is formed to have an inner diameter larger than the outer diameter of the corresponding rotor 19, while the outermost electrode 36a5 is formed to have an outer diameter smaller than the inner diameter of the corresponding pump housing 11A.

[0077] Furthermore, the electrode portion 36A formed in this way is positioned between the rotor 18 and the pump housing 11A, horizontally cutting across the entire passage of the process gas within the shroud 11 at approximately a right angle to the axis center of the shaft 20, and is concentrically arranged with the shaft 20. Therefore, in the vacuum pump 10 of this embodiment, the process gas entering from the suction port 13A and flowing within the shroud 11, and the flushing gas supplied from the first flushing gas supply port 14A, flow through the gaps between the electrodes 36a1, 36a2, 36a3, 36a4, and 36a5 of the electrode portion 36A to the exhaust port 13B.

[0078] Furthermore, in the free radical generating device 10C, when a high-frequency voltage is applied to each electrode 36a1, 36a2, 36a3, 36a4, and 36a5 of the electrode section 36A from the power source 36B, and a flushing gas such as O2 or NF3 is supplied from the first flushing gas supply port 14A, O free radicals and F free radicals are generated as the flushing gas passes between each electrode 36a1, 36a2, 36a3, 36a4, and 36a5. In addition, it functions as follows: when the O and F free radicals flow to the exhaust port 13B, they apply high energy to the deposits accumulated inside the cover 11, forcibly breaking the molecular chains on the surface of the deposits and decomposing them into low-molecular-weight gases. These low-molecular-weight gases are then transported to the exhaust port 13B and discharged from the exhaust port 13B to the outside of the vacuum pump 10.

[0079] The control unit 10D is, for example, composed of a microcomputer, which controls the motor unit 25, radial magnetic bearing units 26 and 27, axial magnetic bearing unit 28, free radical generator 10C, auxiliary pump connected to the first flushing gas supply port 14A, and auxiliary pump connected to the second flushing gas supply port 14B in a predetermined process according to the program loaded into the microcomputer.

[0080] The vacuum pump 10, configured as described above, operates as follows to discharge gas from the vacuum container.

[0081] First, under the control of the control unit 10D, the radial magnetic bearing units 26 and 27 and the axial magnetic bearing unit 28 are started, and the rotor 18 is magnetically levitated as a whole via the shaft 20, so that the rotor 18 is supported in space without contact.

[0082] Next, under the control of the control unit 10D, the motor unit 25 is driven to rotate the shaft 20 in a predetermined direction. That is, the rotor 18 is rotated in a predetermined direction. The rotation speed is, for example, about 30,000 revolutions per minute. In this embodiment, the rotation direction of the rotor 18 is clockwise when viewed from the intake port side, but the vacuum pump 10 can also be configured to rotate counterclockwise.

[0083] When the rotor 18 rotates, the gas is drawn in from the intake port 13A by the action of the rotating blades 22 of the rotating blade 19 and the stator blades 33 of the stator blades 31 of the stator 17, and is compressed more and more as it goes down. The gas compressed by the turbomolecular pump section 10A is also compressed by the threaded groove pump section 10B and is discharged from the exhaust port 13B.

[0084] However, during the compression of the process gas in the vacuum pump 10, the gas solidifies and accumulates inside the cover 11. Therefore, while the control unit 10D intermittently drives the free radical generator 10C to apply a high-frequency voltage to each electrode 36a1, 36a2, 36a3, 36a4, and 36a5 of the electrode unit 36A, it also supplies O2, NF3, and other flushing gases from the first flushing gas supply port 14A, causing the flushing gases to flow toward the exhaust port 13B into the process gas flow path.

[0085] Furthermore, when the flushing gas flows, the control unit 10D controls the drive of the motor unit 25, switching the rotation of the motor unit 25 to a low speed lower than the rated rotation, so that the rotor 18 runs at a low speed. While the rotor 18 is rotating at a constant speed, flushing gases such as O2 and NF3 flow from the first flushing gas supply port 14A. When the flushing gas flows from the first flushing gas supply port 14A, as it passes between each electrode 36a1, 36a2, 36a3, 36a4, and 36a5, O radicals and F radicals are generated within the free radical generator 10C. Furthermore, when the generated O radicals and F radicals flow towards the exhaust port 13B, they come into contact with the deposits accumulated inside the cover 11, applying high energy to the deposits and forcibly breaking down the molecular chains on the surface of the deposits into low-molecular-weight gases. These low-molecular-weight gases are then discharged to the outside through the exhaust port 13B. This reduces the amount of material accumulating inside the cover 11.

[0086] Furthermore, the reason for rotating rotor 18 at a low speed when the flushing gas flows is to ensure that the flushing gas flows reliably towards the exhaust port 13B and does not flow back into the vacuum chamber from the intake port 13A, thus preventing corrosion within the vacuum chamber. Therefore, the low-molecular-weight gases decomposed by the flushing gas are discharged from the exhaust port 13B to the outside of the housing 11, reducing the amount of buildup inside the housing 11. This extends the pump's maintenance interval and reduces the frequency of disassembly and overhaul of the vacuum pump.

[0087] Furthermore, during the operation of the vacuum pump 10, inactive gases such as N2 (nitrogen) gas and Ar (argon) gas flow from the second flushing gas supply port 14B into the fixing column 35, protecting the electrical components stored in the electrical component storage section 35a of the fixing column 35 from corrosive gases.

[0088] Furthermore, free radicals are unstable substances that are forcibly pulled apart by applying large amounts of energy to the raw material gas molecules. Therefore, they have the disadvantage of recombining and losing their activity in a relatively short time. On the other hand, inside the hood, the process gas mainly accumulates near the exhaust port 13B. Therefore, even if free radicals are supplied to the vicinity of the intake port 13A, it is not possible to effectively clean the gas. However, in the vacuum pump 10 of this embodiment, the electrode portion 36A of the free radical generator 10C is positioned at the axial middle of the rotor 18, that is, at the boundary between the turbomolecular pump portion 10A and the grooved pump portion 10B. Therefore, the deposits of process gas that are to accumulate downstream of the electrode portion 36A of the free radical generator 10C (towards the exhaust port 13B) can be effectively decomposed and discharged to the outside.

[0089] Furthermore, the multiple electrodes 36a1, 36a2, 36a3, 36a4, and 36a5 of the electrode section 36A of the free radical generator 10C are arranged concentrically in a cylindrical shape, so as to cross the passage through which the process gas and rinsing gas pass within the shroud 11. Therefore, the space occupied by the free radical generator 10C within the shroud 11 can be reduced and made more compact. As a result, the vacuum pump 10 can be miniaturized. In addition, only a pair of electrodes in the electrode section 36A is required. Increasing the number of electrodes increases the amount of free radicals generated, which can further improve the decomposition effect of free radical-induced deposits.

[0090] Furthermore, the above embodiment discloses a configuration where the electrode portion 36A of the free radical generator 10C is positioned at the axial midpoint of the rotor 18, i.e., at the boundary between the turbomolecular pump portion 10A and the grooved pump portion 10B. However, the position of the electrode portion 36A of the free radical generator 10C is not limited to the configuration of the above embodiment; for example, it can be represented as a variation of this embodiment. Figure 3 , Figure 4 The position inside the vacuum pump 10 is indicated in the figure.

[0091] Right now, Figure 3 It means in Figure 1 The image shows a schematic longitudinal sectional side view of a modified example of the vacuum pump 10. Additionally, Figure 3 Chinese annotation and Figure 1 Components with the same reference numerals Figure 1 The components represented in the text are the same components, so repeated descriptions are omitted.

[0092] Figure 3The vacuum pump 10 shown in the figure has the electrode portion 36A of the free radical generator 10C positioned at the axial center of the turbomolecular pump portion 10A. In this modified example of the vacuum pump 10, the electrode portion 36A of the free radical generator 10C is positioned at the axial center of the rotor 18, that is, at the axial center of the turbomolecular pump portion 10A. Therefore, it is possible to effectively decompose the deposits of process gas that are to accumulate downstream of the electrode portion 36A of the free radical generator 10C (towards the exhaust port 13B) and discharge them to the outside in a good manner.

[0093] Figure 4 It means in Figure 1 A schematic longitudinal sectional side view of other variations of the vacuum pump 10 shown in the figure. Additionally, Figure 4 Chinese annotation and Figure 1 Components with the same reference numerals Figure 1 The components represented in the text are the same components, so repeated descriptions are omitted.

[0094] Figure 4 The vacuum pump 10 shown in the diagram places the electrode portion 36A of the free radical generator 10C within the housing 11 at a position axially between the first flushing gas supply port 14A and the rotor 18. In this modified example of the vacuum pump 10, the electrode portion 36A of the free radical generator 10C is placed within the housing 11 of the rotor 18 at a position between the first flushing gas supply port 14A and the rotor 18, thus ensuring a larger space for placing the electrode. Therefore, it can be configured to... Figure 1 , Figure 3 The vacuum pump 10, as shown in the diagram, has more electrodes than the number of electrodes (10 in this modified example), enabling it to generate more free radicals. This allows for more efficient decomposition of the process gas buildup passing through the downstream side (exhaust port 13B side) of the electrode section 36A (compared to the free radical generator 10C), within the turbomolecular pump section 10A and the threaded groove pump section 10B, ensuring proper discharge from the exhaust port 13B to the outside.

[0095] Furthermore, various modifications can be made to this invention without departing from its spirit, and this invention obviously relates to such modifications.

[0096] Furthermore, an embodiment in which a spiral groove 32a is provided on the inner circumferential surface of the fixed cylinder (threaded groove spacer 32) has been described. However, a spiral groove can also be provided on the outer circumferential surface of the second cylinder portion 21b of the cylinder member 21, or a spiral groove can be provided on both sides to form the threaded groove pump portion 10B.

[0097] Alternatively, a circular plate protruding from the outer peripheral surface of the cylindrical component 21 and a circular plate protruding from the inner side of the cover 11 can be provided, and a spiral-shaped threaded groove can be provided on the opposing surfaces to form a threaded groove pump section 10B.

[0098] Explanation of reference numerals in the attached figures

[0099] 10: Vacuum pump

[0100] 10A: Turbomolecular Pump Section

[0101] 10B: Threaded Groove Pump Section

[0102] 10C: Free radical generator

[0103] 10D: Control Department

[0104] 11: Cover

[0105] 11A: Pump casing

[0106] 11B: Pump base

[0107] 11C: Base end cap

[0108] 12A: Fastening and connecting components

[0109] 12B: Mounting bolts

[0110] 13: Intake port

[0111] 13A: Intake port

[0112] 13B: Exhaust port

[0113] 14A: First flushing gas supply port

[0114] 14B: Second flushing gas supply port

[0115] 15A: Flange

[0116] 15B: Flange

[0117] 16A: Flange

[0118] 16B: Flange

[0119] 17: Stator

[0120] 18: Rotor

[0121] 19: Rotary Wing

[0122] 20: Axis

[0123] 20a: Convex edge

[0124] 21: Cylindrical component

[0125] 21a: First cylindrical section

[0126] 21b: Second cylindrical section

[0127] 22: Rotary airfoil blade

[0128] 23: Next door

[0129] 23a: Shaft hole

[0130] 24: Installing bolts

[0131] 25: Motor Section

[0132] 26: Radial magnetic bearing section

[0133] 27: Radial magnetic bearing section

[0134] 28: Axial magnetic bearing section

[0135] 29: Radial displacement sensor

[0136] 30: Radial displacement sensor

[0137] 31: Stator Wing

[0138] 32: Threaded groove spacer

[0139] 32a: Spiral groove (threaded groove)

[0140] 33: Stator blades

[0141] 34: Spacer

[0142] 35: Fixing post

[0143] 35a: Electrical Components Storage Section

[0144] 36A: Electrode section

[0145] 36B: Power supply

[0146] 36a1: Electrode

[0147] 36a2: Electrode

[0148] 36a3: Electrode

[0149] 36a4: Electrode

[0150] 36a5: Electrode

[0151] 37: Bolt hole

[0152] 38: Annular groove

[0153] 39: Opening.

Claims

1. A vacuum pump, wherein the vacuum pump comprises a shroud, a stator, and a rotor, The aforementioned stator is disposed inside the aforementioned cover. The aforementioned rotor has a shaft that is rotatably supported relative to the aforementioned stator, and together with the aforementioned shaft, it is rotatably housed within the aforementioned cover. The aforementioned rotor is cylindrical. The aforementioned vacuum pump is characterized by, have: A pair of electrodes, enclosed within the aforementioned cover, are positioned at the boundary between the turbomolecular pump section and the threaded groove pump section. Multiple cylindrical plates are arranged concentrically and at approximately equal intervals with the axial center of the aforementioned shaft, so that the process gas accumulated around the aforementioned boundary between the aforementioned turbomolecular pump section and the aforementioned threaded groove pump section is decomposed and discharged evenly. A power source applies a high-frequency voltage to the aforementioned pair of electrodes to generate free radicals as the flushing gas passes through the aforementioned pair of electrodes.

2. The vacuum pump as described in claim 1, characterized in that, The aforementioned turbomolecular pump is configured to have a plurality of rotating blades protruding from the outer periphery of the aforementioned rotor, and to have stator blades provided, wherein the stator blades are axially separated from the aforementioned rotating blades, protruding from the inner periphery of the aforementioned cover, and are configured to face the aforementioned rotating blades.

3. The vacuum pump as described in claim 1 or 2, characterized in that, The aforementioned threaded pump section is configured such that at least one of the outer periphery of the aforementioned rotor and the inner periphery of the aforementioned stator is provided with a helical or vortex-shaped threaded groove.

4. The vacuum pump as described in claim 1 or 2, characterized in that, The aforementioned electrode is positioned at the axial midpoint of the aforementioned rotor.

5. The vacuum pump as described in claim 1 or 2, characterized in that, A flushing gas supply port for supplying the flushing gas is provided at a position upstream of the aforementioned electrode within the aforementioned enclosure.

6. The vacuum pump as described in claim 1 or 2, characterized in that, It has a control unit that can switch the rotor to rated rotation or low-speed rotation, which is lower than the rated rotation speed.

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