Vacuum pump and vacuum exhaust device

Abstract

Provided is a vacuum pump capable of improving cleaning performance. The vacuum pump is provided with a heater (11), purge gas introduction ports (12, 13), a purge gas valve (14), and an exhaust valve (16). As an operation mode, there is a cleaning operation mode capable of sublimating deposits in a turbomolecular pump (100). In the cleaning operation mode, at least one of the heater (11), the purge gas valve (14), or the exhaust valve (16) is controlled so that at least a portion of the inside of the turbomolecular pump (100) is above the sublimation temperature of the deposits in the turbomolecular pump (100) and is pressurized to a pressure region that becomes a molecular flow or a viscous flow.

Description

Technical Field

[0001] The present invention relates to a vacuum pump and a vacuum exhaust device having, for example, a turbomolecular pump. Background Technology

[0002] Generally, turbomolecular pumps are known as a type of vacuum pump. In this turbomolecular pump, rotating blades are rotated by energizing a motor inside the pump body, which flings gas molecules (process gas) drawn into the pump body, thereby expelling the gas. Furthermore, some turbomolecular pumps are equipped with heaters and cooling pipes to properly manage the temperature inside the pump (Patent Document 1). Moreover, the applicant has proposed a vacuum pump system that allows the turbomolecular pump to switch between a normal operating mode and a cleaning operating mode (Japanese Patent Application No. 2019-165839).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2011-80407 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] However, in the vacuum pump system proposed by the applicant (Japanese Patent Application No. 2019-165839), the temperature of the vacuum pump is controlled to be higher during cleaning operation than during normal operation. However, depending on the state of the deposits, there are cases where the cleaning performance is not fully utilized.

[0008] The purpose of this invention is to provide a vacuum pump and vacuum exhaust device that can improve cleaning performance.

[0009] Methods used to solve problems

[0010] (1) In order to achieve the above objective, the present invention relates to a vacuum pump equipped with a heating mechanism, a gas introduction mechanism and a pressure control mechanism, characterized in that, as an operating mode, it has a cleaning mode that enables the sublimation of deposits inside the vacuum pump; in the aforementioned cleaning mode, at least one of the aforementioned heating mechanism, the aforementioned gas introduction mechanism or the aforementioned pressure control mechanism is controlled; at least a portion of the interior of the aforementioned vacuum pump is raised to a pressure region above the sublimation temperature of the aforementioned deposits inside the aforementioned vacuum pump and pressurized to become an intermediate flow or a viscous flow.

[0011] (2) In addition, in order to achieve the above objective, another invention is a vacuum pump as described in (1), characterized in that at least a portion of the interior of the aforementioned vacuum pump is controlled to alternately repeat a first set pressure that will become an intermediate flow or viscous flow and a second set pressure that will become a molecular flow.

[0012] (3) In addition, in order to achieve the above objective, another invention is a vacuum pump as described in (1) or (2), characterized in that, in the aforementioned cleaning mode, the rotational speed of the aforementioned vacuum pump is set to be lower than that in normal operation.

[0013] (4) In addition, in order to achieve the above-mentioned objective, another invention is a vacuum pump described in any one of (1) to (3), characterized in that, in the aforementioned cleaning mode, the partial pressure of the gas generated by the sublimation of the aforementioned deposit is controlled to be less than half of the sublimation pressure of the aforementioned deposit.

[0014] (5) In addition, in order to achieve the above objective, another invention is a vacuum pump as described in any one of (1) to (4), characterized in that, in the aforementioned cleaning mode, at least a portion of the aforementioned vacuum pump is pressurized to 2 [Torr] or more.

[0015] (6) In addition, in order to achieve the above objective, another invention is a vacuum pump as described in (5), characterized in that, in the aforementioned cleaning mode, at least a portion of the aforementioned vacuum pump is pressurized to below 10 [Torr].

[0016] (7) In addition, in order to achieve the above-mentioned objective, another invention is a vacuum pump as described in any one of (1) to (6), characterized in that the gas supplied from the aforementioned gas introduction mechanism to the aforementioned vacuum pump includes at least one of nitrogen, helium and hydrogen.

[0017] (8) In addition, in order to achieve the above-mentioned objective, another invention relates to a vacuum exhaust device comprising a vacuum pump, a heating mechanism, a gas introduction mechanism and a pressure control mechanism, characterized in that, as an operating mode, it has a cleaning mode capable of sublimating the deposits in the aforementioned vacuum pump; in the aforementioned cleaning mode, at least one of the aforementioned heating mechanism, the aforementioned gas introduction mechanism or the aforementioned pressure control mechanism is controlled; at least a portion of the interior of the aforementioned vacuum pump is raised to a pressure region above the sublimation temperature of the aforementioned deposits in the aforementioned vacuum pump and pressurized to become an intermediate flow or a viscous flow.

[0018] Invention Effects

[0019] According to the above invention, a vacuum pump and a vacuum exhaust device that can improve cleaning performance can be provided. Attached Figure Description

[0020] Figure 1This is a structural diagram illustrating a vacuum pump according to one embodiment of the present invention.

[0021] Figure 2 This is a circuit diagram of an amplifier circuit.

[0022] Figure 3 This is a time graph representing the control when the current command value is greater than the detected value.

[0023] Figure 4 This is a time graph representing the control when the current command value is smaller than the detected value.

[0024] Figure 5 This is a block diagram that schematically illustrates the structure for controlling a vacuum pump according to one embodiment of the present invention.

[0025] Figure 6 It is an explanatory diagram that uses sublimation curves to roughly represent the relationship between the normal action mode and the cleaning action mode.

[0026] Figure 7 It is a graph that roughly represents the changes in pressure during cleaning action patterns.

[0027] Figure 8 It is a graph showing the relationship between gas pressure and thermal conductivity.

[0028] Figure 9 It is an explanatory diagram that schematically represents the state of the accumulation of material falling onto the parts. Detailed Implementation

[0029] Hereinafter, the vacuum pump 10 according to an embodiment of the present invention will be described with reference to the accompanying drawings. Figure 1 This refers to a vacuum pump 10 according to an embodiment of the present invention. The vacuum pump 10 includes a turbomolecular pump 100 (pump device), a pump control device (hereinafter simply referred to as "control device") 200 for controlling the operation of the turbomolecular pump 100, and a heater 11 as a heating mechanism.

[0030] Furthermore, the vacuum pump 10 includes purge gas inlet ports 12 and 13 and a purge gas valve 14 (valve) for opening and closing the flow path of the purge gas. In this embodiment, the purge gas inlet ports 12 and 13 and the purge gas valve 14 are all part of the gas inlet mechanism.

[0031] Furthermore, the vacuum pump 10 includes an exhaust port 15 for discharging gas from the pump and an exhaust valve 16 (pressure control mechanism) disposed downstream of the turbomolecular pump 100. Moreover, in this embodiment, both the exhaust port 15 and the exhaust valve 16 constitute part of the gas exhaust mechanism. Here, in Figure 1In the diagram, the purge gas valve 14 is marked "V1" and the exhaust valve 16 is marked "V2" to distinguish the two valves 14 and 16.

[0032] Here, the term "vacuum pump," according to the understanding of the invention, can refer to the range from the purge gas valve 14 and exhaust valve 16 to the turbomolecular pump 100 (pump device) (including the heater 11). Alternatively, the term "vacuum pump" can refer to a vacuum pump device like the turbomolecular pump 100, or as a broader concept encompassing various vacuum pump devices other than turbomolecular pumps. Furthermore, the purge gas valve 14 and exhaust valve 16, relative to the turbomolecular pump 100, can be detachably fixed with bolts, or fixed by means of welding or other means to prevent easy separation.

[0033] Figure 1 The turbomolecular pump 100 shown is connected, for example, to the vacuum chamber (not shown) of an object device such as a semiconductor manufacturing apparatus. Further details will be described later, but the heater 11 heats the turbomolecular pump 100 from the outside, and the purge gas inlet ports 12 and 13 introduce purge gas (also called protective gas, clean gas, etc.) into the interior of the turbomolecular pump 100.

[0034] Furthermore, as will be discussed in detail later, but exhaust valve 16 was... Figure 5 The controller 23 (valve control mechanism) of the control circuit section 22 shown controls and adjusts the flow rate of the gas flowing inside the turbomolecular pump 100. The structure of these devices and the cleaning operations using these devices will be described below.

[0035] exist Figure 1 The image shows a longitudinal sectional view of the aforementioned turbomolecular pump 100. Figure 1 In this turbomolecular pump 100, an intake port 101 is formed at the upper end of a cylindrical outer cylinder 127. Furthermore, a rotating body 103 is located inside the outer cylinder 127. This rotating body 103 has multiple rotating blades 102 (102a, 102b, 102c…) arranged radially and in multiple layers around its periphery, serving as turbine blades for drawing and expelling gas. A rotor shaft 113 is mounted at the center of this rotating body 103. This rotor shaft 113 is suspended in the air and its position is controlled, for example, by a 5-axis controlled magnetic bearing. The rotating body 103 is generally made of a metal such as aluminum or an aluminum alloy.

[0036] Four upper radial electromagnets 104 are arranged in pairs along the X and Y axes. Four upper radial sensors 107 are located close to and corresponding to each upper radial electromagnet 104. The upper radial sensors 107 use, for example, inductive sensors with conductive windings or eddy current sensors, to detect the position of the rotor shaft 113 based on changes in the inductance of the conductive windings that correspond to the position of the rotor shaft 113. The upper radial sensors 107 are configured to detect radial displacement of the rotor shaft 113, i.e., the rotating body 103 fixed thereto, and transmit this information to the control device 200.

[0037] In this control device 200, for example, a compensation circuit with PID regulation function generates an excitation control command signal for the upper radial electromagnet 104 based on the position signal detected by the upper radial sensor 107. Figure 2 The amplifier circuit 150 shown (described later) performs excitation control on the upper radial electromagnet 104 based on the excitation control command signal, thereby adjusting the upper radial position of the rotor shaft 113.

[0038] Furthermore, the rotor shaft 113 is formed of a high-permeability material (iron, stainless steel, etc.) and is attracted by the magnetic force of the upper radial electromagnet 104. This adjustment is performed independently in the X-axis and Y-axis directions respectively. In addition, the lower radial electromagnet 105 and the lower radial sensor 108 are configured in the same way as the upper radial electromagnet 104 and the upper radial sensor 107, adjusting the lower radial position of the rotor shaft 113 in the same way as the upper radial position.

[0039] Furthermore, axial electromagnets 106A and 106B are arranged to sandwich a circular metal disk 111 mounted on the lower part of the rotor shaft 113. The metal disk 111 is made of a high magnetic permeability material such as iron. An axial sensor 109 is provided to detect the axial displacement of the rotor shaft 113, and is configured to send its axial position signal to the control device 200.

[0040] Furthermore, in the control device 200, for example, a compensation circuit with PID regulation function generates excitation control command signals for axial electromagnets 106A and 106B based on the axial position signal detected by the axial sensor 109. The amplifier circuit 150 performs excitation control on axial electromagnets 106A and 106B based on these excitation control command signals. As a result, axial electromagnet 106A attracts metal disk 111 upward by magnetic force, and axial electromagnet 106B attracts metal disk 111 downward, thereby adjusting the axial position of rotor shaft 113.

[0041] Thus, the control device 200 appropriately adjusts the magnetic force applied to the metal disk 111 by the axial electromagnets 106A and 106B, causing the rotor shaft 113 to be magnetically levitated in the axial direction and held in space without contact. Furthermore, the amplifier circuit 150 that controls the excitation of these upper radial electromagnets 104, lower radial electromagnets 105, and axial electromagnets 106A and 106B will be described later.

[0042] On the other hand, the motor 121 has a plurality of magnetic poles arranged circumferentially around the rotor shaft 113. Each magnetic pole is controlled by the control device 200 to drive the rotor shaft 113 to rotate via an electromagnetic force acting between the rotor shaft 113 and the control device 200. Furthermore, the motor 121 is equipped with a rotational speed sensor (not shown), such as a Hall element, a resolver, or an encoder, and the rotational speed of the rotor shaft 113 is detected based on the detection signal from the rotational speed sensor.

[0043] Furthermore, for example, a phase sensor (not shown) is installed near the lower radial sensor 108 to detect the phase of rotation of the rotor shaft 113. In the control device 200, the detection signals from this phase sensor and the rotational speed sensor are used together to detect the position of the magnetic poles.

[0044] Multiple fixed blades 123 (123a, 123b, 123c...) are arranged with slight gaps between them and the rotating blades 102 (102a, 102b, 102c...). The rotating blades 102 (102a, 102b, 102c...) move the exhaust gas molecules downward by collision, and are therefore formed at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113. The fixed blades 123 (123a, 123b, 123c...) are made of metals such as aluminum, iron, stainless steel, copper, or alloys containing these metals as components.

[0045] Furthermore, the fixed blade 123 is also formed at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113, and is arranged facing inward toward the outer cylinder 127, staggered from the layers of the rotating blade 102. Moreover, the outer peripheral end of the fixed blade 123 is supported in a state of being inserted between multiple stacked fixed blade spacers 125 (125a, 125b, 125c...).

[0046] The fixed blade spacer 125 is an annular component, made of metals such as aluminum, iron, stainless steel, copper, or alloys containing these metals. An outer cylinder 127 is fixed to the outer periphery of the fixed blade spacer 125 with a slight gap. A base portion 129 is disposed at the bottom of the outer cylinder 127. An exhaust port 133 is formed in the base portion 129, communicating with the outside. Exhaust gas entering the intake port 101 from the chamber (vacuum chamber) side and being transferred to the base portion 129 is conveyed to the exhaust port 133.

[0047] Furthermore, according to the application of the turbomolecular pump 100, a threaded spacer 131 is provided between the lower part of the fixed blade spacer 125 and the base part 129. The threaded spacer 131 is a cylindrical component made of metals such as aluminum, copper, stainless steel, iron, or alloys composed of these metals, and has multiple helical threaded grooves 131a engraved on its inner circumferential surface. The helical direction of the threaded grooves 131a is the direction in which the molecules of the exhaust gas are moved towards the exhaust port 133 when they move in the rotational direction of the rotating body 103. At the lowest part of the rotating body 103, which is connected to the rotating blades 102 (102a, 102b, 102c...), a cylindrical part 102d hangs down. The outer circumferential surface of the cylindrical part 102d is cylindrical and extends toward the inner circumferential surface of the threaded spacer 131, approaching the inner circumferential surface of the threaded spacer 131 with a predetermined gap. The exhaust gas, which is moved to the threaded groove 131a by the rotating blade 102 and the fixed blade 123, is guided by the threaded groove 131a and conveyed to the base portion 129.

[0048] The base portion 129 is a disc-shaped component that forms the base of the turbomolecular pump 100, and is generally made of metals such as iron, aluminum, or stainless steel. The base portion 129 physically holds the turbomolecular pump 100 and also functions as a heat conduction path, so it is preferable to use metals such as iron, aluminum, or copper that have rigidity and high thermal conductivity.

[0049] In this structure, if the rotating blade 102 is driven to rotate together with the rotor shaft 113 by the motor 121, exhaust gas is drawn from the chamber through the intake port 101 by the action of the rotating blade 102 and the fixed blade 123. The rotational speed of the rotating blade 102 is typically 20,000 rpm to 90,000 rpm, and the circumferential speed at the tip of the rotating blade 102 reaches 200 m / s to 400 m / s. The exhaust gas drawn in from the intake port 101 is transferred to the base portion 129 between the rotating blade 102 and the fixed blade 123. At this time, the temperature of the rotating blade 102 rises due to frictional heat generated when the exhaust gas contacts the rotating blade 102, heat conduction generated by the motor 121, etc., but this heat is transferred to the fixed blade 123 side by radiation or conduction by gas molecules of the exhaust gas.

[0050] The fixed blade spacers 125 are joined together on the outer periphery to transfer the heat received by the fixed blade 123 from the rotating blade 102, the frictional heat generated when the exhaust gas comes into contact with the fixed blade 123, and so on to the outside.

[0051] Furthermore, in the above description, it was assumed that the threaded spacer 131 was disposed on the outer periphery of the cylindrical portion 102d of the rotating body 103, and that a threaded groove 131a was engraved on the inner peripheral surface of the threaded spacer 131. However, there are also cases where, conversely, a threaded groove is engraved on the outer peripheral surface of the cylindrical portion 102d, and a spacer with a cylindrical inner peripheral surface is disposed around it.

[0052] Furthermore, according to the application of the turbomolecular pump 100, the electrical assembly is surrounded by a stator column 122, and the stator column 122 is kept at a specified pressure by a purge gas to prevent the gas drawn from the intake port 101 from intruding into the electrical assembly. The electrical assembly consists of an upper radial electromagnet 104, an upper radial sensor 107, a motor 121, a lower radial electromagnet 105, a lower radial sensor 108, axial electromagnets 106A and 106B, an axial sensor 109, etc.

[0053] In this case, piping (purge gas inlet ports 12 and 13) is provided on the outer cylinder 127 and the base portion 129, through which purge gas is introduced. The introduced purge gas is sent to the exhaust port 133 through the gaps between the protective bearing 120 and the rotor shaft 113, between the rotor and stator of the motor 121, and between the stator column 122 and the inner circumferential cylindrical portion of the rotating blade 102.

[0054] Here, the turbomolecular pump 100 requires model identification and control based on individually adjusted inherent parameters (e.g., characteristics corresponding to the model). To store these control parameters, the turbomolecular pump 100 includes an electronic circuit section 141 within its main body. The electronic circuit section 141 comprises a semiconductor memory such as an EEP-ROM, electronic components such as semiconductor elements for accessing it, and a mounting substrate 143 for mounting them. This electronic circuit section 141 is housed below, for example, a rotational speed sensor (not shown) near the center of the base section 129 constituting the lower part of the turbomolecular pump 100, and is sealed by an airtight bottom cover 145.

[0055] However, in the semiconductor manufacturing process, some process gases introduced into the chamber have the property of becoming solid if their pressure becomes higher than a specified value or their temperature becomes lower than a specified value. Inside the turbomolecular pump 100, the pressure of the exhaust gas is lowest at the intake port 101 and highest at the exhaust port 133. During the process gas's journey from the intake port 101 to the exhaust port 133, if its pressure becomes higher than a specified value or its temperature becomes lower than a specified value, the process gas becomes solid and accumulates inside the turbomolecular pump 100.

[0056] For example, when SiCl4 is used as a process gas in an Al etching apparatus, the vapor pressure profile shows that under low vacuum (760 [Torr] ~ 10... －2 At [Trr] and low temperatures (approximately 20 [°C]), solid products (e.g., AlCl3) precipitate and accumulate inside the turbomolecular pump 100. Therefore, if process gas precipitates accumulate inside the turbomolecular pump 100, this accumulation narrows the pump flow path, causing a decrease in the performance of the turbomolecular pump 100. Furthermore, the aforementioned products are prone to solidification and adhesion in the high-pressure areas near the exhaust port 133 and the threaded spacer 131.

[0057] Therefore, to solve this problem, conventionally, a heater and annular water-cooling pipe 149 are wound around the outer periphery of the base portion 129, and a temperature sensor (e.g., a thermistor, described later) is embedded in the base portion 129. Based on the signal from this temperature sensor, heating by the heater and cooling by the water-cooling pipe 149 are controlled (hereinafter referred to as TMS; TMS; Temperature Management System) to maintain the temperature of the base portion 129 at a certain high temperature (set temperature). In this embodiment, the aforementioned heater 11 is used as the heater, and the TMS is performed for temperature control during normal operation.

[0058] Next, regarding the turbomolecular pump 100 configured in this way, 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. Figure 2 The diagram below shows the circuit diagram of amplifier circuit 150.

[0059] exist Figure 2In this configuration, one end of the electromagnet winding 151, which constitutes the upper radial electromagnet 104, is connected to the positive terminal 171a of the power supply 171 via transistor 161, and the other end is connected to the negative terminal 171b of the power supply 171 via current detection circuit 181 and transistor 162. Furthermore, transistors 161 and 162 are so-called power MOSFETs, which have a structure in which a diode is connected between their source and drain.

[0060] At this time, the cathode terminal 161a of transistor 161 is connected to the positive terminal 171a, and the anode terminal 161b is connected to one end of electromagnet winding 151. Furthermore, the cathode terminal 162a of transistor 162 is connected to current detection circuit 181, and the anode terminal 162b is connected to negative terminal 171b.

[0061] On the other hand, the cathode terminal 165a of the diode 165 used for current regeneration is connected to one end of the electromagnet winding 151, and its anode terminal 165b is connected to the negative terminal 171b. Similarly, the cathode terminal 166a of the diode 166 used for current regeneration is connected to the positive terminal 171a, and its anode terminal 166b is connected to the other end of the electromagnet winding 151 via the current detection circuit 181. Furthermore, the current detection circuit 181 is, for example, composed of a Hall effect current sensor and a resistive element.

[0062] The amplifier circuit 150 configured as described above corresponds to one electromagnet. Therefore, with 5-axis magnetic bearing control and a total of 10 electromagnets 104, 105, 106A, and 106B, each electromagnet is configured with the same amplifier circuit 150, and the 10 amplifier circuits 150 are connected in parallel to the power supply 171.

[0063] Furthermore, the amplifier control circuit 191 is, for example, composed of a digital signal processor (DSP) unit (not shown) of the control device 200, which switches the transistors 161 and 162 on / off.

[0064] The amplifier control circuit 191 compares the current value detected by the current detection circuit 181 (the signal reflecting this current value is called the current detection signal 191c) with a predetermined current command value. Then, based on the comparison result, it determines the size of the pulse width (pulse width times Tp1, Tp2) generated within one control cycle Ts, which is the PWM control cycle. As a result, gate drive signals 191a, 191b with this pulse width are output from the amplifier control circuit 191 to the gate terminals of transistors 161, 162.

[0065] Furthermore, when the rotating body 103 accelerates through a resonance point or experiences interference during constant-speed operation, position control of the rotating body 103 under high speed and strong force is required. Therefore, a high voltage of approximately 50V is used as the power supply 171 to enable a rapid increase (or decrease) in the current flowing in the electromagnet winding 151. Additionally, a capacitor (not shown) is typically connected between the positive terminal 171a and the negative terminal 171b of the power supply 171 for stabilization.

[0066] In this structure, if both transistors 161 and 162 are turned on, the current flowing in the electromagnet winding 151 (hereinafter referred to as electromagnet current iL) increases; if both are turned off, the electromagnet current iL decreases.

[0067] Furthermore, by setting one of transistors 161 and 162 to conduct and the other to cut off, a so-called flywheel current is maintained. Moreover, by allowing this flywheel current to flow through the amplifier circuit 150, hysteresis losses in the amplifier circuit 150 can be reduced, thus lowering the overall power consumption of the circuit. Furthermore, by controlling transistors 161 and 162 in this way, high-frequency noise such as high-order harmonics generated in the turbomolecular pump 100 can be reduced. Furthermore, by measuring this flywheel current using the current detection circuit 181, the electromagnet current iL flowing in the electromagnet winding 151 can be detected.

[0068] That is, when the detected current value is smaller than the current command value, such as Figure 3 As shown, during the control period Ts (e.g., 100 μs), both transistors 161 and 162 are turned on only once for a duration equivalent to the pulse width time Tp1. Therefore, during this period, the electromagnet current iL increases toward the current value iLmax (not shown) that can flow from the positive terminal 171a to the negative terminal 171b via transistors 161 and 162.

[0069] On the other hand, if the detected current value is larger than the current command value, such as Figure 4 As shown, transistors 161 and 162 are turned off only once during the control cycle Ts for a duration equivalent to the pulse width time Tp2. Therefore, the electromagnet current iL during this period decreases toward the current value iLmin (not shown) that can be regenerated from the negative terminal 171b to the positive terminal 171a via diodes 165 and 166.

[0070] Furthermore, in both cases, one of transistors 161 and 162 is turned on after the pulse width times Tp1 and Tp2 have elapsed. Therefore, a continuous current is maintained in the amplifier circuit 150 during this period.

[0071] Turbomolecular pump 100 with such basic structure Figure 1 The upper side (the side with the intake port 101) becomes the intake section connected to the target equipment side, and the lower side (the side where the exhaust port 133 is provided on the base 129 in a manner protruding to the right in the figure) becomes the exhaust section connected to an auxiliary pump (a back pump formed by a dry pump for roughing) or the like, which is not shown in the figure. Furthermore, the turbomolecular pump 100, in addition to... Figure 1 In addition to the vertical position shown, it can also be used in an inverted, horizontal, or tilted position.

[0072] Furthermore, in the turbomolecular pump 100, the aforementioned outer cylinder 127 and base portion 129 are combined to form a housing (hereinafter referred to as the "main body housing" etc.). In addition, the turbomolecular pump 100 is electrically (and structurally) connected to a box-shaped electrical housing (not shown), and the aforementioned control device 200 is installed in the electrical housing.

[0073] The internal structure of the main body shell (the combination of the outer cylinder 127 and the base portion 129) of the turbomolecular pump 100 can be divided into a rotating mechanism portion that rotates the rotor shaft 113, etc., by means of a motor 121, and an exhaust mechanism portion that is driven by the rotating mechanism portion. Furthermore, the exhaust mechanism portion can be considered as a turbomolecular pump mechanism portion composed of rotating blades 102, fixed blades 123, etc., and a slot exhaust mechanism portion composed of a cylindrical portion 102d, threaded spacers 131, etc.

[0074] Furthermore, the aforementioned purging gas is used to protect the bearing components, rotating blades 102, etc., to prevent corrosion caused by exhaust gas (process gas), and to cool the rotating blades 102. The supply of this purging gas can be carried out using conventional methods.

[0075] As a general method related to the supply of purge gas, an example can be given of supplying purge gas to a pipeline connected to the purge gas inlet ports 12 and 13 via a purge gas storage tank (such as a nitrogen (N2) storage tank) or a purge gas valve 14. Figure 1 This technique is used in the vacuum pump 10 shown.

[0076] The purge gas flowing through the bearing section, etc., together with other gases in the main body shell (the combination of the outer cylinder 127 and the base section 129), is discharged outward through the exhaust port 133. If there are gases other than the purge gas in the main body shell, the purge gas is discharged outward through the exhaust port 133 along with the other gases.

[0077] The aforementioned protective bearing 120 is also referred to as a "touch down (T / D) bearing" or a "backup bearing". With the help of these protective bearings 120, even in the event of electrical system failure or atmospheric intrusion, the position and orientation of the rotor shaft 113 will not change significantly, thus preventing damage to the rotating blades 102 and their peripheral parts.

[0078] In addition, in the figures showing the structure of the turbomolecular pump 100 ( Figure 1 In the diagram, the section lines representing the cross-section of a part are omitted to avoid complicating the drawing.

[0079] Next, the aforementioned heater 11, exhaust valve 16, and other devices, as well as the control of each device, will be described. In this embodiment, a surface heater (surface heater) is used as the heater 11. The heater 11 is disposed on the outer periphery of the outer cylinder 127 in the turbomolecular pump 100 and is in contact with the surface of the outer cylinder 127. The number of heaters 11 can be one or more.

[0080] The heater 11 has an external dimension that spans the slot exhaust mechanism section composed of the aforementioned threaded spacer 131 and the turbomolecular pump mechanism section composed of the rotating blade 102 and the fixed blade 123. Moreover, the heater 11 is positioned in the portion facing most of the threaded spacer 131, sandwiching the outer cylinder 127.

[0081] The heater 11 is controlled by electricity to change the heat output. Furthermore, the heater 11 transfers the generated heat via the outer cylinder 127 to the threaded spacer 131 and other components, causing the temperature of the components within the turbomolecular pump 100 to rise. In this embodiment, the heater 11 is controlled by... Figure 5 The controller 23 of the control circuit section 22, which is shown in a simplified form, is activated.

[0082] The control circuit section 22 is installed in the aforementioned control device 200 and forms part of the control device 200. Furthermore, the purge gas valve 14 and the exhaust valve 16 are also controlled by the controller 23 of the control circuit section 22. That is, the control circuit section 22 and its controller 23 are installed in the control device 200 and function as a heater control mechanism, a purge gas valve control mechanism, and an exhaust valve control mechanism.

[0083] Here, the purge gas valve control mechanism and the exhaust valve control mechanism can also be collectively referred to as "valve control mechanism". Alternatively, the controller 23, the control circuit section 22, and the control device 200 can be collectively or separately referred to as "purge gas valve control mechanism", "exhaust valve control mechanism" and "valve control mechanism".

[0084] The control circuit section 22 includes a storage section 24 composed of ROM, RAM, etc. This storage section 24 may also be partially or entirely built into the controller 23.

[0085] The controller 23 has a CPU (central processing unit) and is capable of controlling each device that is the object of control, according to the control program stored in the storage unit 24 and with reference to various control data also stored in the storage unit 24. Furthermore, the controller 23 receives signals from the temperature sensor 21, pressure sensor 25, and speed sensor 27, etc.

[0086] Furthermore, the controller 23 monitors signals from various sensors while controlling the temperature of the heater 11, controlling the purge gas valve 14 (on / off control), and controlling the exhaust valve 16 (opening degree control). In addition, the controller 23 also controls various devices such as the aforementioned motor 121 and magnetic bearings (reference numerals omitted).

[0087] More specifically, controller 23 controls the temperature of heater 11 to rise to a specified temperature and maintain that temperature. Furthermore, controller 23 controls exhaust valve 16 to raise or lower the pressure of the gas inside turbomolecular pump 100. Additionally, controller 23 activates purge gas valve 14 as needed to control the introduction of purge gas into purge gas at purge gas inlet ports 12 and 13.

[0088] In this embodiment, the purge gas valve 14 is designed to be opened / closed by the controller 23. However, it is not limited to this. For example, it can also be designed to control the opening degree of the purge gas valve 14 by the controller 23, thereby changing the flow rate of the purge gas supplied to the turbomolecular pump 100 according to the opening degree of the purge gas valve 14.

[0089] In addition, the controller 23 receives an operation signal for the operation mode switching switch 26. This operation mode switching switch 26 is operated by the operator when switching between the normal operation mode (normal operating mode) and the cleaning operation mode (cleaning mode). Various types of general switching devices can be used as the operation mode switching switch 26.

[0090] The details of the normal operating mode described above will be presented later, but this refers to the normal operating mode (operating state) used to maintain the target equipment (here, a semiconductor manufacturing apparatus) connected to the turbomolecular pump 100 at a specified vacuum level or to transfer the gas (here, the process gas of the semiconductor manufacturing apparatus) to the target equipment. In contrast, the cleaning operating mode is a non-normal operating mode that performs cleaning operations to remove byproducts (deposits) that have precipitated into the turbomolecular pump 100 during operation in the normal operating mode.

[0091] Regarding these operating modes, the aforementioned storage unit 24 stores temperature information and rotation speed information corresponding to the operating mode. Regarding the normal operating mode, the storage unit 24 stores first temperature information and first rotation speed information. The first temperature information refers to a temperature predetermined to ensure a suitable temperature environment for the gas flow path. Furthermore, the first rotation speed information refers to a first rotation speed predetermined to suit the gas transport.

[0092] Regarding the cleaning operation mode, the storage unit 24 stores second temperature information and second rotation speed information. The second temperature information represents a second temperature suitable for sublimating and regasifying the deposit. This second temperature is a value higher than the first temperature associated with the normal operation mode. Furthermore, the second rotation speed information represents a second rotation speed lower than the first rotation speed associated with the normal operation mode.

[0093] Next, the operation of the turbomolecular pump 100 in the normal operating mode and the cleaning operating mode will be described in more detail. First, in the normal operating mode, the turbomolecular pump 100 receives a rotation start signal as a command signal from the controller 23, causing the motor 121 to rotate. As the motor 121 rotates, the rotating blades 102 rotate, initiating the discharge and compression of gas.

[0094] If the rotational speed of the rotating blade 102 reaches the aforementioned first rotational speed, then the adjustment of the rotational speed of the rotating blade 102 is complete. When the rotational speed adjustment is complete, the rotational speed of the rotating blade 102 is determined by a speed sensor located at a predetermined position within the main housing (the combination of the outer cylinder 127 and the base portion 129). Figure 5 The speed sensor 27 is used for detection. The detection result of the speed sensor 27 is then input to the controller 23, which determines that the speed of the rotating blade 102 has reached the first speed and controls the motor 121 to maintain the speed at a constant level.

[0095] In parallel with this speed control, heating temperature adjustment is performed. During this heating temperature adjustment, the heater 11 is energized and its temperature rises, gradually heating the area surrounding the heater 11. Furthermore, if the temperature detected by the temperature sensor 21 reaches the aforementioned first temperature, the controller 23 determines that the temperature adjustment is complete and controls the heater 11 to maintain the temperature at a constant level.

[0096] If the controller 23 determines that both the rotational speed and temperature have reached their respective target values ​​(first rotational speed and first temperature), it notifies the display unit 28 that the turbomolecular pump 100 has switched to normal operation (steady-state operation). Furthermore, in this normal operation mode, the heater 11 raises the temperature of the gas flow path to a certain level and maintains it, preventing the precipitation of deposits within the range possible by means of the first temperature.

[0097] Furthermore, the first temperature is determined to prevent excessive thermal expansion and deformation of the various heated components (internal components), and is an allowable temperature that allows the pump to operate without malfunctions under steady-state conditions. Moreover, the first temperature is determined taking into account the material and strength of the various internal components, as well as the flow rate of the gas flowing into the turbomolecular pump 100 from the vacuum chamber of the upstream equipment.

[0098] Furthermore, since aluminum alloy is used as the material for the main internal components such as the outer cylinder 127, base 129, fixed blade 123, threaded spacer 131 and rotating body 103, as mentioned above, and given that the gas flow rate is empirically well specified, the first temperature, which is the temperature during steady-state operation, can be set to, for example, 100°C.

[0099] However, this first temperature is merely an allowable temperature to ensure the pump operates without malfunctions, so deposits may still precipitate. For example, if the deposit is ammonium fluoride, its sublimation temperature is 150°C, so even if the temperature is maintained at 100°C, deposits will still precipitate. Therefore, in this embodiment, the precipitated deposits can be removed by performing vaporization (re-vaporization) in the cleaning operation mode as described below.

[0100] In the cleaning operation mode, to remove the deposits, the heater 11 is controlled to raise the temperature of its periphery to a second temperature higher than the first temperature associated with the normal operation mode. This second temperature is the temperature at which the deposits generated in the normal operation mode can be re-vaporized. In this embodiment, the second temperature, which is the temperature during the cleaning operation, is set to 200°C. By performing this regeneration through vaporization (re-vaporization), the deposits generated during operation in the normal operation mode can be removed. Here, the term "processed gas" can be used in a comprehensive manner, including the gas generated by the re-vaporization of the precipitated byproducts and the gas from the target equipment (here, the semiconductor manufacturing apparatus).

[0101] Furthermore, in the cleaning operation mode, the motor 121 is controlled to rotate at a second speed. This second speed is approximately 50% of the first speed. By driving the motor 121 at a second speed, which is sufficiently lower than the first speed, the compression heat and frictional heat generated during gas discharge can be reduced compared to driving the motor 121 at the first speed. In addition, the load such as the centrifugal force acting on the rotating blade 102 can be reduced, so the allowable temperature can be increased compared to the normal operation mode. On the other hand, thanks to the molecular transport force of the rotating blade 102, the regenerated gas does not flow back toward the stationary blade 123, which is cooler because it has not been heated by the heater 11, but is discharged from the exhaust port 133 to the outside of the main body shell (the combination of the outer cylinder 127 and the base portion 129). Moreover, the discharge of the regasified deposit is completed within a certain period of time from the start of the rotating blade 102. The "certain period of time" mentioned here is determined by conditions such as the composition of the deposit.

[0102] In this way, the rotating blade 102 is also used in the cleaning operation mode, conveying gas while rotating at a lower speed than in the normal operation mode, efficiently and smoothly discharging the vaporized deposits (gas produced by the sublimation of the deposits), thereby preventing pressure rise caused by the retention of vaporized deposits. Therefore, by simultaneously performing vaporization at the second temperature and discharging gas at the second rotation speed, the vaporization of the deposits is promoted compared to performing vaporization only at the second temperature. Furthermore, regarding the vaporization of the deposits, the sublimation curve f(…) in the state diagram representing the relationship between the solid phase, liquid phase, and gas phase can be used to illustrate the process. Figure 6 It is represented by ) . Moreover, although the deposit can be vaporized in the gas phase region (gas side) of the sublimation curve f, it is preferable to set the temperature to be higher than the sublimation temperature in order to supply the heat required for vaporization.

[0103] Furthermore, the transition from the normal operating mode to the cleaning operating mode can be performed, for example, by the operator operating the aforementioned operating mode switching switch 26 and controller 23 to switch modes during the normal operating mode.

[0104] Conversely, regarding the transition from the cleaning operation mode to the normal operation mode, for example, the operator can also control the mode switching by operating the aforementioned operation mode switching switch 26 and controller 23 during the cleaning operation mode.

[0105] Preferably, during the aforementioned "certain time" required for the discharge of the regenerated gas, the operation mode switching switch 26 is not activated, and the operation to switch back to the normal operation mode is not accepted. Furthermore, it is possible for the controller 23 to determine whether the aforementioned "certain time" has elapsed, and if so, to accept the operation of the operation mode switching switch 26. Additionally, it is also possible to automatically switch to the normal operation mode even without the operation of the operation mode switching switch 26 if the aforementioned "certain time" has elapsed.

[0106] Furthermore, it is possible to consider, in addition to the exhaust gas generated during cleaning by the rotation of the rotating blade 102, the regenerated gas can also be discharged by means of an exhaust pump separately provided with the turbomolecular pump 100. Such exhaust gas generated during cleaning by utilizing another exhaust pump can be referred to as "exhaust assistance".

[0107] When performing this exhaust assistance, a rear pump (not shown) located downstream of the turbomolecular pump 100 can be used as an auxiliary pump. That is, in exhaust systems in which the turbomolecular pump 100 is installed, there are generally cases where a rear pump (not shown) is located downstream of the turbomolecular pump 100. Furthermore, with the aid of this rear pump, exhaust is performed at a lower vacuum than that of the turbomolecular pump 100 in the pre-stage (pre-processing stage) of the exhaust. Therefore, it is possible to consider using the rear pump for exhaust in the cleaning operation mode.

[0108] Furthermore, when the aforementioned rear pump is used for exhaust assistance, it can be operated in the clean operation mode. Once a predetermined vacuum level is achieved, the motor 121 of the turbomolecular pump 100 is rotated (started rotating) to perform exhaust operation at a second rotational speed. By performing exhaust assistance via the rear pump in this manner, the regenerated gas can be discharged more efficiently.

[0109] Next, the pressure control (pressure control during cleaning operation) in the aforementioned cleaning operation mode will be explained. In this embodiment, the operation period in the cleaning operation mode is divided into a period for the heat transfer process and a period for the sublimation process. The period for the heat transfer process is the period that promotes heat transfer to the deposit. Furthermore, the period for the sublimation process is the period that promotes the sublimation of the deposit.

[0110] During the heat transfer process, such as Figure 7 As shown, the pressure (the pressure in the turbomolecular pump 100) is set to a relatively high first set pressure P1, and during the sublimation process, the pressure is set to a relatively low second set pressure P2. Furthermore, in the cleaning operation mode, the heat transfer process and the sublimation process are alternately and repeatedly performed to clean the interior of the turbomolecular pump 100. This is based on the following idea.

[0111] As described above, in the cleaning operation mode, when the turbomolecular pump 100 is not operating in its normal operation mode (during standby time), a process is performed to heat the components constituting the flow path of the exhaust gas and to vaporize and remove the deposits generated during normal operation mode. By performing such a cleaning operation, deposits can be removed during the vacuum pump's standby time.

[0112] Therefore, when the turbomolecular pump 100 is performing normal exhaust (exhaust during normal operation), it is not always necessary to keep the gas flow path at a high temperature, thus reducing the burden on the various components. Moreover, as a result, there is the advantage of being able to increase the permissible flow rate in the turbomolecular pump 100.

[0113] However, the cleaning action involves supplying the heat energy needed to sublimate the deposits from the surface of the heated parts to the deposits. Moreover, the inventors considered the relationship between the state of the deposits and the cleaning effect, noting that depending on the state of the deposits, there are situations where the cleaning performance is not fully utilized and the desired cleaning effect cannot be obtained.

[0114] Specifically, for example, when the deposits adhere to the wall of the part in the form of a thin film, the cleaning function works effectively even when only basic cleaning actions are performed. Furthermore, even when the deposits peel off from the wall of the part, become flakes (flake deposits), or fall into the flow path as powder (powder deposits), heat conduction is not significantly affected when they are piled up without gaps, allowing the cleaning function to be fully utilized.

[0115] However, when the deposits float relative to the wall of the part, or when thin or powdery deposits accumulate while creating spaces between each other, it becomes impossible to effectively supply heat to the deposits. Moreover, in such cases, even if the part is heated, the surface temperature of the deposits does not rise as much, and a sufficient sublimation rate (also known as "cleaning rate" or "sweeping rate") is no longer achieved.

[0116] Furthermore, in the aforementioned patent application (Japanese Patent Application No. 2019-165839), the applicant proposed a scheme that utilizes exhaust assistance from the after-pump during the cleaning operation mode. Moreover, with such exhaust assistance during the cleaning operation mode, the pressure within the turbomolecular pump 100 can be easily reduced. As a result, the regenerated gas can be discharged more efficiently, making it easier for deposits to sublimate.

[0117] However, if the pressure inside the turbomolecular pump 100 drops to a certain level (e.g., around 0.1 Torr) due to exhaust assistance during the cleaning operation mode, the cleaning effect is no longer as good. This phenomenon is considered to be caused by the formation of floating deposits, flaky deposits, and powdery deposits on the surface of the parts. Furthermore, the relationship between the pressure drop and cleaning performance considering these deposits can be explained as follows.

[0118] Generally, the relationship between pressure and thermal conductivity, which is related to the motion state of a gas, is roughly as follows: Figure 8 That's how it's represented. Figure 8 The horizontal axis represents pressure, and the vertical axis represents thermal conductivity. For example... Figure 8 As shown, if the pressure increases when the gas is in the molecular flow region (molecular flow region), the thermal conductivity gradually increases.

[0119] Furthermore, if the pressure increases and the motion state transitions to the intermediate flow region (intermediate flow region), the change in thermal conductivity becomes gradual, and no further change in thermal conductivity can be observed in the viscous flow region (viscous flow region). Moreover, in the molecular flow region, the lower the pressure, the lower the thermal conductivity (heat transfer).

[0120] That is, in order to efficiently transfer heat to the deposit, it is preferable to have the gas flow state in the region near the point where the gas flow state shifts from the intermediate flow region to the viscous flow region (intermediate-viscous flow region). Moreover, by setting the pressure of at least a portion of the gas flow path to the pressure near the point where the gas flow state changes from intermediate flow to viscous flow, it becomes easier to supply heat energy to that portion of the deposit.

[0121] Furthermore, sublimation of the deposits occurs at the surface of the deposits. Therefore, without transferring sufficient heat to the surface of the deposits to raise their surface temperature, a sufficient sublimation rate cannot be achieved.

[0122] also, Figure 9 The state of the peeled sheets, which are stacked as thin sheet-like accumulations, without creating space is schematically represented. Figure 9 In the accompanying drawings, reference numeral 71 indicates a peeling strip, and reference numeral 72 indicates the wall surface of the part after the peeling strip has fallen off. Furthermore, Figure 9 Reference numeral 73 in the figure indicates the space between the stripper 71 and other strippers 71, and between the stripper 71 and the wall surface 72.

[0123] Many peeling sheets 71 are tilted at irregular angles, and in some places they make point contact with each other while accumulating on the wall surface 72. Thus, when the falling peeling sheets 71 accumulate, as... Figure 9As shown, it can be imagined that the contact state between adjacent stripping sheets 71 and between stripping sheets 71 and wall surface 72 is not surface contact but point contact in many places.

[0124] Furthermore, it can be assumed that the amount of heat transferred from the surface (contact surface) of the release tab 71 to the surface (contact surface) in contact with other release tabs 71 and wall surface 72 is smaller than that in the case of surface contact, so the heat transfer to the release tab 71 in point contact is relatively small.

[0125] In the case where a space is created between the stripping sheets 71, if the size (representing length) of the space 73 is assumed to be, for example, 0.1 mm under different pressure conditions, the heat transfer is calculated as follows.

[0126] First, the Knudsen number (Kn) is known as an indicator of whether a flow can be treated as a continuum.

[0127] The Knudsen number (Kn) is represented as follows.

[0128] [Formula 1]

[0129]

[0130] λ: Mean free travel [m]

[0131] L: Represents length [m]

[0132] T: Temperature [K]

[0133] k B Boltzmann constant [J / K]

[0134] P: Pressure [Torr]

[0135] σ: Molecular diameter [m]

[0136] Furthermore, the following relationship exists between the state of motion of a gas and the Knudsen number.

[0137] Molecular flux: Knudsen number (λ / L) > 0.3

[0138] Viscous flow: Knudsen number (λ / L) < 0.01

[0139] (1) When the pressure (P) is 0.1 [Torr]

[0140] The mean free path of N2 gas is λ = 0.5 mm.

[0141] The Knudsen number becomes λ / L = 0.5mm / 0.1mm = 5. Here, L = 0.1mm is the size of the aforementioned space 73.

[0142] At this Knudsen number, since the gas belongs to the region of molecular flow (5 > 0.3), therefore according to Figure 8 The graph shows that the heat transfer (thermal conductivity) is relatively smaller.

[0143] (2) When the pressure (P) is 5.0 [Torr]

[0144] The mean free path of N2 gas is λ = 0.01 mm.

[0145] The Knudsen number is λ / L = 0.01 mm / 0.1 mm = 0.1.

[0146] At this Knudsen number, since the gas belongs to the intermediate flow region (0.3 > 0.1 > 0.01), therefore according to Figure 8 The chart shows that heat transfer can be expected through the gas.

[0147] Based on such heat transfer calculations, in this embodiment, during the cleaning operation mode... Figure 5 The heater 11 and exhaust valve 16 shown are used for control. Furthermore, in cleaning operation mode, the space within the turbomolecular pump 100 is utilized, such as... Figure 7 The pressure is changed alternately and periodically as shown.

[0148] Figure 7 The pressure adjustment shown is performed by controlling the exhaust valve 16 while introducing purge gas from the purge gas inlet ports 12 and 13 into the turbomolecular pump 100. In this way, even if a sufficient pressure rise cannot be achieved by supplying purge gas solely from the purge gas inlet ports 12 and 13, the pressure can be increased more reliably.

[0149] Pressure control can be achieved by monitoring the aforementioned pressure sensor 25. Figure 5 The output of the valve is processed simultaneously. However, it is not limited to this. The relationship between the pressure and the opening degree and opening time of the exhaust valve 16 can be calculated in advance, and the pressure can be estimated based on the opening degree and time of the exhaust valve 16, thereby controlling the pressure.

[0150] Furthermore, if sufficient cleaning can be achieved by controlling the opening / closing of the purge gas valve 14 even without increasing or decreasing the pressure using the exhaust valve 16, the control of the exhaust valve 16 used for the heat transfer process and the sublimation process can be omitted.

[0151] Furthermore, as described above, during the cleaning operation mode, the temperature of the heater 11 is set to a second temperature that is higher than that during the normal operation mode. Furthermore, during the cleaning operation mode, the rotational speed of the motor 121 is set to a second rotational speed that is lower than that during the normal operation mode.

[0152] exist Figure 7In the heat transfer process shown, because the pressure is increased to the first set pressure P1, the gas's motion state shifts from the intermediate flow region to the viscous flow region. Consequently, gas molecules become difficult to disperse, and sublimation becomes less likely to occur. However, thermal conductivity increases, and heat transfer to the deposit proceeds effectively. The period during which this heat transfer process is performed becomes a heat transfer promotion period where heat transfer is highly valued.

[0153] From the heat transfer step, the pressure is reduced to the second set pressure P2, thereby shifting the gas's motion from the intermediate flow region to the molecular flow region. This facilitates gas molecule diffusion and promotes sublimation. The period during which this sublimation step is performed is known as the sublimation promotion period, which emphasizes sublimation.

[0154] Furthermore, during the cleaning operation, the switching between heat transfer and sublimation processes is continuously executed, repeatedly cycling through heat transfer and sublimation. Therefore, by selectively creating heat transfer-enhancing and sublimation-enhancing periods and repeatedly cycling through these processes, sufficient duration is ensured. Consequently, heat energy is efficiently supplied to the deposits, resulting in higher cleaning effectiveness.

[0155] here, Figure 7 This is a simplified representation of pressure changes, and is not limited to a control method that depicts pressure changes as a rectangular wave. For example, a control method that depicts a gradual change between a first set pressure P1 and a second set pressure P2, such as depicting a trapezoidal wave or a sine wave, can also be used. Furthermore, the times for the heat transfer process and the sublimation process can be different. Moreover, the time required for the heat transfer process (and the time required for the sublimation process) does not need to be the same for each cycle; they can also be different.

[0156] Furthermore, if the cleaning operation mode is predetermined, the period can be divided into two parts, with the heat transfer process performed in the first half and the sublimation process performed in the second half. However, when the heat transfer and sublimation processes are repeated over relatively short periods, it becomes easy to suppress the temperature drop of the deposits. Therefore, it is preferable to adopt a control method that repeatedly performs the heat transfer and sublimation processes over relatively short periods.

[0157] Furthermore, in this embodiment, the flow rate of the purge gas supplied during the cleaning operation mode is set such that the partial pressure of the vaporized deposit (gas generated by the sublimation of the deposit) is less than half of the saturated vapor pressure of the deposit at that temperature (also known as the "sublimation pressure of the deposit"). This is done for the following reasons.

[0158] If purge gas is added, the partial pressure of the gases other than the purge gas decreases, and the partial pressure of the deposit also decreases. Moreover, the lower the partial pressure, the easier it is for the deposit to sublimate. However, whether the deposit actually sublimates well depends on the degree to which the partial pressure of the deposit is relative to its saturated vapor pressure.

[0159] For example, imagine a situation where the total pressure of the gas before the purge gas supply is set to 1 [Torr], and the partial pressure of the deposit is 0.1 [Torr] (=10%). In this situation, assuming that while maintaining the total pressure, the purge gas is supplied at a flow rate that is 90% of the partial pressure of the purge gas, then the proportion of the original gas becomes 10% of the total, and the partial pressure of the deposit drops to 0.01 [Torr], which is 10% of the original partial pressure.

[0160] Furthermore, the degree of sublimation of the deposit is actually controlled by the saturated vapor pressure of the deposit. Therefore, half of the saturated vapor pressure of the deposit is determined as a target reference value, and the amount of purge gas supplied is determined to maintain the partial pressure of the deposit below this reference value. Examples of vaporized deposits (gases produced through the sublimation of the deposit) include titanium tetrafluoride (TiF4) and aluminum chloride (AlCl3).

[0161] Furthermore, in this embodiment, the internal pressure of the turbomolecular pump 100 is increased so that at least a portion of the gas flow path reaches 2 [Torr] or more. Setting the pressure to 2 [Torr] is based on the following: in a vacuum pump 10 with the turbomolecular pump 100 installed as in this embodiment, considering the size of the envisioned deposit, the pressure at which the gas transitions from a molecular flow to an intermediate flow is approximately 2 [Torr]. Moreover, by setting the first set pressure P1 to 2 [Torr] or more with a target of 2 [Torr], efficient heat transfer to the deposit can be achieved. Furthermore, as an upper limit related to the first set pressure P1, for example, 10 [Torr] could be considered.

[0162] In addition to N2, a gas containing at least one of the gases with high thermal conductivity, such as helium (He) and hydrogen (H2), can also be used as the purge gas. Furthermore, a gas mixture of such gases (mixed gas) can be used as the purge gas.

[0163] According to the above description, in the cleaning operation mode, the vacuum pump 10 of this embodiment controls at least one of the heater 11, the gas introduction mechanism (here, the purge gas valve 14), and the pressure control mechanism (here, the exhaust valve 16) so that at least a portion of the interior of the turbomolecular pump 100 is above the sublimation temperature of the deposits inside the vacuum pump (the second temperature) and is pressurized to a pressure region that becomes an intermediate flow or a viscous flow (the region that becomes the first set pressure P1).

[0164] Here, as described above, controlling at least one of the heater 11, the gas inlet mechanism (here, the purge gas valve 14), and the pressure control mechanism (here, the exhaust valve 16) to increase the pressure means that, after the turbomolecular pump 100 is operated in its normal operating mode, the desired pressure can be achieved by controlling only one of the devices, namely the heater 11, the purge gas valve 14, and the exhaust valve 16, without controlling the other devices.

[0165] Furthermore, by controlling the heater 11, the gas introduction mechanism (here, the purge gas valve 14), and the pressure control mechanism (here, the exhaust valve 16), heat transfer via gas can be achieved, which can promote heat transfer from the wall surface 72 of the part to the deposit (here, the sheet-like deposit or the powdery deposit) (the execution of the heat transfer process).

[0166] Furthermore, since at least a portion of the interior of the turbomolecular pump 100 is then brought to a temperature above the sublimation temperature of the deposits in the vacuum pump (the second temperature) and the pressure is reduced to a pressure region that becomes an intermediate flow or molecular flow (the region that becomes the second set pressure P2), the deposits after heat transfer can be sublimated (the sublimation process is performed).

[0167] Furthermore, since the sublimation process is performed following the heat transfer process, the deposits that are adequately supplied with heat energy can always be sublimated. Therefore, the deposits can be effectively cleaned, improving the cleaning performance of the vacuum pump 10. Moreover, the improved cleaning effect allows for the effective removal of deposits in a short time.

[0168] Furthermore, because of these factors, the maintenance time of equipment such as the turbomolecular pump 100 can be shortened. Moreover, the productivity of manufactured products (such as semiconductor manufacturing) produced using equipment that utilizes vacuum venting can be increased.

[0169] Furthermore, during the cleaning operation, if gas is supplied while the turbomolecular pump 100 is running, the gas is adiabatically compressed within the flow path, thereby increasing its temperature. Therefore, not only heat transfer from the wall 72 of the part, but also the direct transfer of the gas's own thermal energy to the deposit can be expected.

[0170] Here, the aforementioned deposits, including floating, flaky, and powdery deposits, can potentially be generated anywhere along the gas flow path. Therefore, at least a portion of the gas flow path needs to meet the temperature and pressure conditions required for the cleaning operation mode described so far.

[0171] Furthermore, various parts and areas can be cited as places where sheet-like or powdery deposits tend to accumulate, but the wall surface 132 of the threaded spacer 131, where the threaded groove 131a is divided into threaded teeth 131b, is a particularly suitable example of a part or area where sheet-like or powdery deposits tend to accumulate. Therefore, placing the heater 11 near the threaded spacer 131 is effective for easily raising the temperature.

[0172] Furthermore, non-adhesive coatings can be applied to areas where deposits are prone to accumulate. Examples of non-adhesive coatings include coatings made of films formed by processing fluoropolymers.

[0173] Furthermore, according to the vacuum pump 10 of this embodiment, at least a portion of the interior of the turbomolecular pump 100 is controlled to alternately repeat a first set pressure P1 that becomes an intermediate or viscous flow and a second set pressure P2 that becomes a molecular flow. Therefore, even after the sublimation process, the pressure around the deposit can be raised again to the point where the gas becomes an intermediate or viscous flow, and the heat energy consumed by the previous sublimation can be quickly replenished. Furthermore, the sublimation of the deposit can then continue to be promoted. Thus, a continuous cleaning effect (washing effect) can be achieved.

[0174] Furthermore, according to the vacuum pump 10 of this embodiment, in the cleaning operation mode, the rotational speed of the turbomolecular pump 100 is set to be lower than that in the normal operation mode. Therefore, the compression heat and frictional heat generated during gas discharge can be reduced compared to the normal operation mode.

[0175] Furthermore, according to the vacuum pump 10 of this embodiment, in the cleaning operation mode, the partial pressure of the gas generated by the sublimation of the deposit is controlled to be less than half of the sublimation pressure (saturated vapor pressure) of the deposit. Therefore, the deposit can be sublimated well.

[0176] Furthermore, according to the vacuum pump 10 of this embodiment, in the cleaning operation mode, at least a portion of the turbomolecular pump 100 is pressurized to 2 [Torr] or higher. Therefore, sublimation can be reliably and effectively performed at pressures near where the gas transitions from a molecular flow to an intermediate flow.

[0177] Furthermore, according to the vacuum pump 10 of this embodiment, in the cleaning operation mode, at least a portion of the turbomolecular pump 100 is pressurized to below 10 [Torr]. Therefore, sufficient heat transfer to the deposit can be achieved during the heat transfer process.

[0178] Furthermore, according to the vacuum pump 10 of this embodiment, the gas supplied to the turbomolecular pump 100 from the purge gas inlet ports 12 and 13 includes at least one of nitrogen, helium, and hydrogen. Therefore, pressure control can be performed using a general-purpose gas.

[0179] Furthermore, according to this embodiment, the vacuum pump 10 supplies purge gas not only through the downstream purge gas inlet port 13 of the turbomolecular pump 100, but also through the upstream purge gas inlet port 12, from the upstream side of the turbomolecular pump mechanism, which consists of rotating blades 102, fixed blades 123, etc. Therefore, it is possible to prevent the vaporized deposits from flowing back towards the turbomolecular pump mechanism and from entering the gap between the rotor shaft 113 and the stator column 122.

[0180] In addition to the aforementioned, CF4 (carbon tetrafluoride) gas can also be used as the purge gas. Furthermore, the purge gas can be introduced, for example, through the intake port 101.

[0181] Furthermore, in this embodiment, it is assumed that the heater 11 (heating mechanism), the purge gas inlet ports 12 and 13 (gas inlet mechanism), and the exhaust valve 16 (pressure control mechanism) are described as additional devices to the turbomolecular pump 100. However, at least one of these devices can be integrated with the turbomolecular pump 100 as a device included by the turbomolecular pump 100 (a device that is sold and distributed in the market as part of the turbomolecular pump 100).

[0182] Furthermore, the vacuum pump 10 according to this embodiment uses a planar heater (planar heater) as the heater 11, which enables uniform temperature distribution and allows for uniform heating and regasification over a wide range. Moreover, it prevents partial residue buildup, resulting in a reduction in the frequency of overhauls. Consequently, in addition to improving the production efficiency of semiconductors and the like, it also reduces the cost of the amount of work required for overhauls.

[0183] Furthermore, the heater is not limited to a surface-type heater; various types of heaters can be used. For example, a box-type heater can also be used. In this case, the heater can be inserted from the outside of the outer cylinder 127 into the threaded spacer 131, a part capable of transferring heat to the threaded spacer 131.

[0184] Furthermore, a sheathed heater can be used as the heater. Moreover, various other general heaters can be used instead of surface heaters, box heaters, and sheathed heaters. Furthermore, examples of general heaters include IH heaters, which are electromagnetic induction heaters. For example, when using an IH heater, the specified temperature can be reached in a relatively short time, further shortening the time required for regasification and cleaning.

[0185] Furthermore, regarding the combination of materials used for the constituent parts of the turbomolecular pump 100, besides making the rotating body 103 out of aluminum alloy, it is also possible to make the rotating body 103 out of stainless steel alloy. Additionally, parts other than the rotating body 103 can also be made of stainless steel alloy. Moreover, for example, aluminum alloy can be used for constituent parts where high thermal conductivity, lightweight, and ease of machining are strongly required, while stainless steel alloy can be used for constituent parts where high rigidity and strength are strongly required. Furthermore, in addition to aluminum alloy and stainless steel alloy, titanium alloy can also be used, for example.

[0186] Furthermore, the present invention is not limited to the above-described embodiments. As long as it is within the scope of the technical concept of the present invention, many variations can be achieved by means of the ordinary creative ability of those skilled in the art.

[0187] Explanation of reference numerals in the attached figures

[0188] 10. Vacuum pump (vacuum exhaust device)

[0189] 11. Heater (Heating Mechanism)

[0190] 12 and 13 are purge gas inlet ports (gas inlet mechanism).

[0191] 14. Purge gas valve (gas introduction mechanism)

[0192] 16. Exhaust valve (pressure control mechanism)

[0193] 23 Controller (Valve Control Mechanism)

[0194] 100 turbomolecular pump (vacuum pump)

[0195] P1 First Set Pressure

[0196] P2 Second Setting Pressure

Claims

1. A vacuum pump, comprising a heating mechanism, a gas introduction mechanism having a purge gas inlet port and a purge gas valve, and a pressure control mechanism, characterized in that, It has a control device that can switch between the normal operating mode of the aforementioned vacuum pump and a cleaning mode that can sublimate the deposits inside the aforementioned vacuum pump as an operating mode. In the aforementioned cleaning mode, the aforementioned control device drives the aforementioned vacuum pump at a lower speed than the aforementioned vacuum pump in the aforementioned normal operating mode. By means of the control of the aforementioned heating mechanism, at least a portion of the interior of the aforementioned vacuum pump is made to be above the sublimation temperature of the aforementioned deposits inside the aforementioned vacuum pump, and by means of the control of the amount of purge gas introduced by the aforementioned gas introduction mechanism and the opening and closing control of the aforementioned pressure control mechanism, at least a portion of the interior of the aforementioned vacuum pump is pressurized to a pressure region that becomes an intermediate flow or viscous flow by means of the aforementioned purge gas.

2. The vacuum pump as described in claim 1, characterized in that, At least a portion of the interior of the aforementioned vacuum pump is controlled to alternately and repeatedly become a first set pressure that will become an intermediate flow or viscous flow and a second set pressure that will become a molecular flow.

3. The vacuum pump as described in claim 1 or 2, characterized in that, In the aforementioned cleaning mode, the speed of the aforementioned vacuum pump is set to be lower than usual.

4. The vacuum pump according to any one of claims 1 to 3, characterized in that, In the aforementioned cleaning mode, the partial pressure of the gas generated by the sublimation of the aforementioned deposits is controlled to be less than half of the sublimation pressure of the aforementioned deposits.

5. The vacuum pump according to any one of claims 1 to 4, characterized in that, In the aforementioned cleaning mode, at least a portion of the aforementioned vacuum pump is pressurized to above 2 Torr.

6. The vacuum pump as described in claim 5, characterized in that, In the aforementioned cleaning mode, at least a portion of the aforementioned vacuum pump is pressurized to below 10 Torr.

7. The vacuum pump according to any one of claims 1 to 6, characterized in that, The gas supplied from the aforementioned gas inlet mechanism to the aforementioned vacuum pump includes at least one of nitrogen, helium, and hydrogen.

8. A vacuum exhaust device, comprising a vacuum pump, a heating mechanism, a gas introduction mechanism with a purge gas inlet port and a purge gas valve, and a pressure control mechanism, characterized in that, It has a control device that can switch between the normal operating mode of the aforementioned vacuum pump and a cleaning mode that can sublimate the deposits inside the aforementioned vacuum pump as an operating mode. In the aforementioned cleaning mode, the aforementioned control device drives the aforementioned vacuum pump at a lower speed than the aforementioned vacuum pump in the aforementioned normal operating mode. By means of the control of the aforementioned heating mechanism, at least a portion of the interior of the aforementioned vacuum pump is made to be above the sublimation temperature of the aforementioned deposits inside the aforementioned vacuum pump, and by means of the control of the amount of purge gas introduced by the aforementioned gas introduction mechanism and the opening and closing control of the aforementioned pressure control mechanism, at least a portion of the interior of the aforementioned vacuum pump is pressurized to a pressure region that becomes an intermediate flow or viscous flow by means of the aforementioned purge gas.

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