JP7792385B2 - Vacuum pumps and vacuum pump components - Google Patents

Description

The present invention relates to vacuum pumps, such as turbomolecular pumps, and vacuum pump components.

Turbomolecular pumps are commonly known as a type of vacuum pump. They are used, for example, for exhausting gases in semiconductor and flat panel manufacturing equipment. In turbomolecular pumps, a motor inside the pump body is energized to rotate rotors, expelling the gas molecules (gas molecules) of the gas (process gas) drawn into the pump body, thereby exhausting the gas. Some turbomolecular pumps are equipped with heaters and cooling tubes to properly manage the temperature inside the pump.

In vacuum pumps such as turbomolecular pumps, reaction products generated during the manufacturing process of semiconductors and other products can accumulate inside the vacuum pump. As a countermeasure, a technology has been devised in which a plasma generator is installed in the vacuum pump and the inside is plasma cleaned.

In the invention disclosed in Patent Document 1, a plasma introduction port (radical supply port 201a) is provided in the casing (outer cylinder 127) of a vacuum pump, to which a plasma generator (radical supply means 201) is connected. Radicals introduced into the casing flow circumferentially through an annular passage (annular groove) formed between the inner wall of the casing and the outer wall of the exhaust mechanism. The radicals are then introduced into the exhaust mechanism through a communication port provided in a spacer (fixed blade spacer 125) that holds the fixed blade (fixed blade 123). This communication port is positioned facing the space created by widening the gap between the rotor (rotor 102) and the fixed blade in the direction of the rotation axis. Therefore, the larger the communication port (diameter or opening area), the wider the gap between the rotor and the fixed blade, resulting in a decrease in pump performance. Therefore, in order to introduce a sufficient amount of radicals into the casing while preventing a decline in pump performance, it is necessary to minimize the size of the communication port, prevent the gap between the rotor and fixed blades from becoming excessive, and provide multiple communication ports around the casing to ensure the opening area of the communication ports.

Japanese Patent Application Laid-Open No. 2022-017864

Because the pressure inside the vacuum pump is low, the inside of the vacuum pump is often in a state of molecular flow, with radicals flying around randomly. In such cases, the probability of radicals flowing from the communication port into the exhaust mechanism can be calculated using the ratio of the cross-sectional area of the communication port to the surface area of the annular passage.

For example, if the communication port has a perfect circle shape with a diameter of 12 mm (cross-sectional area (opening area) of 113 ^mm2 (≒π× ¹²² /4)), and the annular passage has a diameter of 300 mm and a width (for example, in Patent Document 1, the length in the axial direction of the rotor shaft 113, etc.) of 20 mm (surface area of 37,699 ^mm2 (=300×π×20×2)), the cross-sectional area ratio of the communication port (which can be thought of as the probability that radicals will flow from the communication port into the exhaust mechanism) is 0.3% of the surface area of the annular passage. In this case, the probability that radicals flowing through the annular passage will flow into the communication port in one go (on the first rotation after entering the annular passage) can also be thought of as 0.3%.

Furthermore, radicals that do not enter the communication port circulate around the annular passage. For example, as mentioned above, if the ratio of the cross-sectional area of the communication port to the surface area of the annular passage is 0.3%, then theoretically, the radicals can be thought of as circling 333 times before finally entering the communication port. As they circulate, the radicals collide with the inner wall of the annular passage.

When simply introducing gas, repeated wall collisions do not change the gas's properties, so a structure such as that disclosed in Patent Document 1 is acceptable. Furthermore, in order to reduce the piping resistance of the annular passage, it is advantageous to increase the cross-sectional area of the annular passage, and as the cross-sectional area of the annular passage increases, the surface area of the annular passage is often increased as well. However, when introducing plasma, the activity of the plasma gradually decreases as the radicals repeatedly collide with the wall. In other words, if the communication port is excessively small compared to the surface area of the annular passage, radicals will repeatedly collide with the wall in the annular passage, resulting in a significant loss of activity and a reduced cleaning effect.

The object of the present invention is to provide a vacuum pump and vacuum pump components that can effectively utilize radicals.

(1) In order to achieve the above object, the vacuum pump according to the present invention comprises:
an exhaust mechanism including a rotatable rotor and a stator combined with the rotor;
a casing that houses the exhaust mechanism,
a radical exhaust promotion structure is provided that spatially connects a radical introduction port disposed in the casing and a communication port disposed in the exhaust mechanism ;
The radical discharge promoting structure guides the radicals from the radical introduction port to the corresponding communication port without dispersing the radicals beyond the communication port.
It is characterized by:
(2) In order to achieve the above object, another vacuum pump according to the present invention comprises:
an exhaust mechanism including a rotatable rotor and a stator combined with the rotor;
a casing that houses the exhaust mechanism,
a radical exhaust promotion structure is provided that spatially connects a radical introduction port disposed in the casing and a communication port disposed in the exhaust mechanism;
the radical exhaust promotion structure is configured by a groove provided in at least one of the casing and the exhaust mechanism,
The groove is closed at a position where the radical introduction port is spatially connected to the communication port.
It is characterized by:
(3) In order to achieve the above object, the vacuum pump component according to the present invention comprises:
an exhaust mechanism including a rotatable rotor and a stator combined with the rotor;
a casing that houses the exhaust mechanism,
a radical exhaust promotion structure is provided that spatially connects a radical introduction port disposed in the casing and a communication port disposed in the exhaust mechanism ;
The radical discharge promoting structure guides the radicals from the radical introduction port to the corresponding communication port without dispersing the radicals beyond the communication port.
It is characterized by:

The above invention provides a vacuum pump and vacuum pump components that can effectively utilize radicals.

1 is an explanatory diagram schematically illustrating the configuration of a turbomolecular pump (100) according to a first embodiment of the present invention. FIG. 2 is a circuit diagram of an amplifier circuit. 10 is a time chart showing control when a current command value is larger than a detection value. 10 is a time chart showing control when a current command value is smaller than a detection value. FIG. 1A is an explanatory diagram showing a longitudinal section of a turbomolecular pump (100) according to a first embodiment, and FIG. 1B is an explanatory diagram showing a cross section of a connection between an inlet pipe (216) and an outer cylinder (127). FIG. 2 is an explanatory diagram showing the positional relationship of multiple inlet pipes (216). 5(a) is an enlarged view showing a connection portion between an inlet pipe (216) and an outer cylinder (127) of a turbomolecular pump (100) according to the first embodiment, (b) is an enlarged view showing a communication port (254) and its surroundings in FIG. 5(a), and (c) is an enlarged view of FIG. 5(b). (a1) is an explanatory diagram showing a tapered pipe shape having a radical discharge promotion structure, (a2) is an explanatory diagram showing a curved pipe shape having a radical discharge promotion structure, (b1) is an explanatory diagram showing a stepped pipe shape of a conventional structure, and (b2) is an explanatory diagram showing a branched pipe shape of a conventional structure. 1A is an explanatory diagram showing a longitudinal section of a turbomolecular pump (400) according to a second embodiment, and FIG. 1B is an explanatory diagram showing a cross section of a connection between an inlet pipe (216) and an outer cylinder (127). FIG. 10 is an explanatory diagram showing a longitudinal section of a turbomolecular pump (500) according to a third embodiment. 1A is an explanatory diagram showing a longitudinal section of a turbomolecular pump (600) according to a conventional example, and FIG. 1B is an explanatory diagram showing a cross section of the connection between an inlet pipe (216) and an outer cylinder (127).

<Basic Configuration of the Turbomolecular Pump 100 According to the First Embodiment>
1 shows a turbomolecular pump 100 as a vacuum pump according to a first embodiment of the present invention. This turbomolecular pump 100 is adapted to be connected to a vacuum chamber (not shown) of a target device such as a semiconductor manufacturing device.

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

The upper radial electromagnets 104 consist of four electromagnets arranged in pairs on the X and Y axes. Four upper radial sensors 107 are provided adjacent to and corresponding to each of the upper radial electromagnets 104. The upper radial sensors 107 are, for example, inductance sensors or eddy current sensors with conductive windings, and detect the position of the rotor shaft 113 based on changes in the inductance of the conductive windings, which change depending on the position of the rotor shaft 113. The upper radial sensors 107 are configured to detect the radial displacement of the rotor shaft 113, i.e., the rotating body 103 fixed to it, and send the detected displacement to the control device 200.

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

The rotor shaft 113 is made of a highly magnetically permeable 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. The lower radial electromagnet 105 and lower radial sensor 108 are positioned in the same way as the upper radial electromagnet 104 and upper radial sensor 107, and adjust the lower radial position of the rotor shaft 113 in the same way as the upper radial position.

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

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

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

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

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

Multiple fixed blades 123 (123a, 123b, 123c...) are arranged at small gaps (predetermined intervals) from the rotating blades 102 (102a, 102b, 102c...). Each rotating blade 102 (102a, 102b, 102c...) is inclined at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113 in order to transport exhaust gas molecules downward through collisions.

The fixed blades 123 are also formed at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113, and are arranged in a staggered manner with the rotor blades 102 toward the inside of the outer cylinder 127. The outer peripheral ends of the fixed blades 123 are supported by being inserted between multiple stacked fixed blade spacers 125 (125a, 125b, 125c, etc.).

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

Furthermore, depending on the application of the turbomolecular pump 100, a threaded spacer 131 is disposed between the lower part of the fixed vane spacer 125 and the base portion 129. The threaded spacer 131 is a cylindrical member made of a metal such as aluminum, copper, stainless steel, iron, or an alloy containing these metals, and has multiple spiral thread grooves 131a engraved on its inner circumferential surface. The spiral direction of the thread grooves 131a is the direction in which exhaust gas molecules are transported toward the exhaust port 133 when they move in the rotation direction of the rotor 103. A rotor lower cylindrical portion 103b hangs down from the lower part of the rotor main body 103a, on which the rotor vanes 102 (102a, 102b, 102c, etc.) of the rotor 103 are formed. The outer peripheral surface of the rotor's lower cylindrical portion 103b is cylindrical and protrudes toward the inner peripheral surface of the threaded spacer 131, with a specified gap separating them. Exhaust gas transported to the thread groove 131a by the rotor 102 and fixed blades 123 is guided along the thread groove 131a and sent to the base portion 129. In this way, the threaded spacer 131 and the opposing rotor's lower cylindrical portion 103b constitute a Holweck-type exhaust mechanism 204. The Holweck-type exhaust mechanism 204 imparts directionality to the exhaust gas by rotating the rotor's lower cylindrical portion 103b relative to the threaded spacer 131, improving the exhaust characteristics of the turbomolecular pump 100.

The base portion 129 is a disk-shaped member that forms the base of the turbomolecular pump 100 and is generally made of a metal such as iron, aluminum, or stainless steel. The base portion 129 not only physically holds the turbomolecular pump 100 but also functions as a heat conduction path, so it is desirable to use a metal that is rigid and has high thermal conductivity, such as iron, aluminum, or copper.

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

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

In the above description, the threaded spacer 131 is disposed on the outer periphery of the lower cylindrical portion 103b of the rotor 103, and the thread groove 131a is engraved on the inner circumferential surface of the threaded spacer 131. However, the opposite may also be true, where a thread groove is engraved on the outer circumferential surface of the lower cylindrical portion 103b of the rotor, and a spacer with a cylindrical inner circumferential surface is disposed around it.

Depending on the application of the turbomolecular pump 100, the electrical components may be surrounded by a stator column 122 to prevent gas drawn in from the intake port 101 from entering the electrical components, which are composed of the upper radial electromagnet 104, upper radial sensor 107, motor 121, lower radial electromagnet 105, lower radial sensor 108, axial electromagnets 106A and 106B, and axial sensor 109, and the interior of this stator column 122 may be maintained at a predetermined pressure with purge gas.

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

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

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

For example, when _SiCl4 is used as the process gas in an Al etching apparatus, the vapor pressure curve shows that at low vacuum (760 torr to ^10-2 torr) and low temperature (approximately 20°C), a solid product (e.g., _AlCl3 ) precipitates and adheres to and accumulates inside the turbomolecular pump 100. As a result, if precipitates of the process gas accumulate inside the turbomolecular pump 100, these deposits narrow the pump flow path, causing a decrease in the performance of the turbomolecular pump 100. The above-mentioned product is prone to solidification and adhesion in high-pressure areas near the exhaust port 133 and near the threaded spacer 131.

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

Next, we will explain 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 in the turbomolecular pump 100 configured as described above. A circuit diagram of this amplifier circuit is shown in Figure 2.

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

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

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

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

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

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

In addition, when the rotating body 103 passes through a resonance point during acceleration of its rotational speed, or when a disturbance occurs during constant-speed operation, it is necessary to control the position of the rotating body 103 at high speed and with strong force. For this reason, a high voltage of, for example, about 50 V is used for the power supply 171 so that the current flowing through the electromagnet winding 151 can be suddenly increased (or decreased). In addition, a capacitor (not shown) is usually connected between the positive pole 171a and negative pole 171b of the power supply 171 to stabilize the power supply 171.

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

Furthermore, when one of transistors 161 and 162 is turned on and the other is turned off, a so-called flywheel current is maintained. By passing a flywheel current through amplifier circuit 150 in this manner, hysteresis loss in amplifier circuit 150 is reduced, and power consumption of the entire circuit can be kept low. Furthermore, by controlling transistors 161 and 162 in this manner, high-frequency noise such as harmonics generated in turbomolecular pump 100 can be reduced. Furthermore, by measuring this flywheel current with current detection circuit 181, the electromagnet current iL flowing through electromagnet winding 151 can be detected.

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

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

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

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

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

The internal structure of the main body casing of the turbomolecular pump 100 (here, the combination of the outer cylinder 127 and base portion 129) can be divided into a rotation mechanism portion 136 that rotates the rotor shaft 113, etc. using the motor 121, and an exhaust mechanism portion 137 that is rotationally driven by the rotation mechanism portion 136. Furthermore, the exhaust mechanism portion 137 can be divided into a turbomolecular pump mechanism portion 138 composed of the rotor blades 102, fixed blades 123, etc., and a threaded pump mechanism portion (Hollweck-type exhaust mechanism portion 204) composed of the rotor lower cylindrical portion 103b, threaded spacer 131, etc.

The aforementioned purge gas (protective gas) is used to protect the bearing parts and rotor blades 102, etc., to prevent corrosion caused by exhaust gas (process gas), and to cool the rotor blades 102. This purge gas can be supplied using conventional methods.

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

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

In Figure 1, which shows the structure of the turbomolecular pump 100 and the rotor 103, hatching indicating cross sections of components has been omitted to avoid cluttering the drawing.

<Configuration of radical flow path>
As described above, products may accumulate inside the turbomolecular pump 100. In the first embodiment, the products are washed away using a plasma generating device 210 as shown in Figures 1 and 5(a).

The plasma generator 210 is equipped with electrodes (not shown) and other components inside the cylinder 212. The plasma generator 210 applies a high voltage to the atoms of the source gas introduced into the cylinder 212 from the outside, generating radicals. Gases such as NF3 (nitrogen trifluoride) and CF4 (tetrafluoromethane) are used as the source gas.

The plasma generator 210 is connected to the outer cylinder 127 of the turbomolecular pump 100 via a valve device 214 and an inlet pipe 216. While the plasma generator 210, valve device 214, and inlet pipe 216 are shown separated from one another in FIGS. 1 and 5(a), they are hermetically connected via flanges. Note that at least some of the connections between the plasma generator 210, valve device 214, and inlet pipe 216 may be made using components such as clamps (not shown).

The introduction pipe 216 is airtightly connected to the outer cylinder 127. Multiple radical introduction ports 218 (described below) are provided on the side of the outer cylinder 127. In the first embodiment, the radical introduction ports 218 are circular holes that penetrate the outer cylinder 127. The tubular portion of the introduction pipe 216 is also circular. The inner surface of the introduction pipe 216 is tapered, and the inner diameter of the introduction pipe 216 gradually decreases from the plasma generator 210 side (the valve device 214 side) to the outer cylinder 127 side. Furthermore, the internal space of the introduction pipe 216 and the radical introduction ports 218 are spatially connected.

In the outer cylinder 127, the radical introduction ports 218 and the introduction pipes 216 are arranged at 120° intervals in the circumferential direction, as shown schematically in FIG. 6. FIG. 6 shows a cross section (horizontal cross section, horizontal cross section) of the turbomolecular pump 100 cut radially (in the radial direction of the outer cylinder 127) at the position of the introduction pipe 216 connected to the radical introduction port 218. While the plasma generator 210 and valve device 214 are not shown in FIG. 6, a set of the plasma generator 210, valve device 214, and introduction pipe 216 is provided for each radical introduction port 218. In other words, in the first embodiment, three sets of the plasma generator 210, valve device 214, and introduction pipe 216 are provided. The cross sections in FIGS. 1 and 5(a), etc., are taken along line A-A in FIG. 6.

As shown in Figures 5(a) and 7(a), the inlet pipe 216 and the outer cylinder 127 are connected by abutting one flange portion 216a of the inlet pipe 216 against a seating surface 127a formed on the outer cylinder 127. Figure 7(a) shows an enlarged view of the radical inlet port 218 and its surroundings in Figure 5(a). The flange portion 216a of the inlet pipe 216 is located midway along the axial direction of the inlet pipe 216. An O-ring 220 provides an airtight seal between the flange portion 216a of the inlet pipe 216 and the seating surface 127a of the outer cylinder 127. The other flange portion 216b of the inlet pipe 216 is airtightly connected to the valve device 214.

As shown in Figures 5(b) and 7(c), one axial end 222 of the inlet pipe 216 (the end on the outer cylinder 127 side) enters the radical inlet port 218 of the outer cylinder 127 and protrudes inside the outer cylinder 127. Figure 5(b) shows a cross section (planar cross section) of the connection between the inlet pipe 216 and the outer cylinder 127 in Figure 5(a) when viewed from the top (the side of the intake port 101) in Figure 5(a). Figure 7(c) shows an enlarged view of Figure 5(b).

As shown in FIG. 5(a), inside the outer tube 127, an annular passage (annular groove 232) is formed around the entire circumference on the outer surface of the threaded spacer 131. As shown in FIG. 7(a), the annular groove 232 is a stepped space and has a wide opening 232a and a narrow opening 232b. The wide opening 232a is located on the outer periphery of the annular groove 232. The narrow opening 232b is located on the inner periphery of the annular groove 232 and opens to the bottom surface of the wide opening 232a (the bottom surface located on the inner periphery of the annular groove 232). The annular groove 232 faces the inner periphery of the outer tube 127 and is defined by the threaded spacer 131 and the outer tube 127.

As shown in Figures 5(a) and 7(a) and (b), an annular groove 232 is formed along the inner circumferential surface of the outer cylinder 127, and one end 222 of the inlet pipe 216 protrudes into the annular groove 232. Figure 7(b) shows an enlarged view of the annular groove 232 and its surroundings on the left side of Figure 5(a).

As shown in Figures 5 to 7, a manifold (branched tubular part 242) that constitutes the radical exhaust promotion structure is disposed in the annular groove portion 232. As shown in Figures 5(b) and 7(c), the branched tubular part 242 is formed in a tubular shape having one inlet end portion 246, two branched outlet end portions 248a, 248b, and a main pipe portion 250 that connects the inlet end portion 246 and the outlet end portions 248a, 248b.

The inlet end 246 of the branch tubular part 242 is partially curved in an arc and is connected to one end 222 of the inlet pipe 216. The two outlet ends 248a, 248b of the branch tubular part 242 are also curved in an arc and extend from the wide opening 232a of the annular groove 232 into the narrow opening 232b. The main pipe section 250 is formed in an arc that curves along the annular groove 232. In addition, the branched portion of the two main pipe sections 250 is formed with a sharp protrusion 252 that protrudes toward the center of the radical introduction port 218.

The two outlet ends 248a, 248b of the branch tubular part 242 are connected to a communication port 254 (shown on the left side of Figure 5(a) and in Figure 7(b)) provided in the threaded spacer 131. The communication port 254 opens into the bottom surface of the narrow opening 232b in the threaded spacer 131 and passes through the threaded spacer 131. The communication port 254 opens facing the thread groove 131a, spatially connecting the thread groove 131a with the interior of the branch tubular part 242.

Two communication ports 254 are formed for each branch tubular part 242. In the first embodiment, a total of six (= 2 x 3) communication ports 254 are provided around the entire circumference of the annular groove portion 232. Furthermore, the communication ports 254 are arranged symmetrically in pairs, every 120 degrees, around the circumference of the annular groove portion 232. Furthermore, with regard to the arrangement of the two symmetric communication ports 254, the phase of the threaded spacer 131 in the circumferential direction (the same as the phase shift of the outer cylinder 127 in the circumferential direction) is different from the phase shift of the corresponding radical introduction port 218 in the circumferential direction of the outer cylinder 127.

In the first embodiment, the diameters of the openings at the outlet ends 248a and 248b of the branch tubular part 242 are the same. Furthermore, the diameter (inner diameter) of the opening (e.g., a circular opening) at the introduction end 246 is larger than the diameter (inner diameter) of the opening (e.g., a circular opening) at each of the outlet ends 248a and 248b. This is not limited to this, and the diameter (inner diameter) of the opening at the introduction end 246 and the diameter (inner diameter) of the opening at each of the outlet ends 248a and 248b may be the same. Furthermore, the diameter (inner diameter) of the opening at the introduction end 246 may be smaller than the diameter (inner diameter) of the opening at each of the outlet ends 248a and 248b. Furthermore, the diameters (inner diameters) of the openings at the outlet ends 248a and 248b may be different from each other.

The inlet end 246 of the branch tubular part 242 is connected to one end 222 of the inlet pipe 216 by press-fitting (e.g., press-fitting the branch tubular part 242 into the inlet pipe 216). The two outlet ends 248a, 248b of the branch tubular part 242 are also connected to the threaded spacer 131, in which the communication port 254 is formed, by press-fitting (e.g., press-fitting the branch tubular part 242 into the threaded spacer 131). In this way, the branch tubular part 242 connects the radical introduction port 218 located in the outer tube 127 to the communication port 254 located in the threaded spacer 131. Note that the branch tubular part 242 can also be connected to the inlet pipe 216 or the threaded spacer 131 by methods other than press-fitting (e.g., welding). However, using a connection method that involves material deformation, such as press-fitting, allows for easier disassembly of the parts than using a connection method that involves material melting, such as welding.

Radicals generated by the plasma generator 210 pass through the open valve device 214 and the inlet pipe 216 and are introduced into the outlet branch tubular part 242 without dispersing into the annular groove 232. The radicals introduced into the branch tubular part 242 are diverted along the shape of the branch tubular part 242 and are discharged into the thread groove 131a via the outlet ends 248a, 248b and the corresponding communication ports 254. The radicals discharged into the thread groove 131a primarily clean components such as the thread groove pump mechanism (Hollweck-type exhaust mechanism 204) and the exhaust port 133. By providing the communication port 254 midway along the thread groove 131a and introducing the radicals while the impeller 102 is rotating, the radicals can be effectively directed downstream, where reaction products are accumulating, without flowing into the turbomolecular pump mechanism 138.

<Radical exhaust promotion structure>
As described above, the branch tubular part 242 has a radical exhaust promotion structure, and thus guides the radicals supplied to the turbomolecular pump 100 directly from the radical introduction port 218 to the communication port 254 without dispersing them within the annular groove 232. The branch tubular part 242 is contained (accommodated) within the annular groove 232, and the area of the inner wall (inner surface) of the branch tubular part 242 is smaller than the area of the inner wall (inner surface) of the annular groove 232.

The wall surfaces with which radicals can collide are limited to the inner wall (inner surface) of the branched tubular part 242. The radicals reach the communication port 254 without dispersing within the annular groove 232 or colliding with the wall surface (inner surface) of the annular groove 232. As a result, radicals can be prevented from colliding with the inner wall (inner surface) of the annular groove 232 and becoming inactivated. Furthermore, radicals that do not enter the communication port 254 can be prevented from circling the annular groove 232 multiple times. These factors make it possible to effectively utilize radicals.

The radical exhaust promotion structure described above will be explained below in comparison with the conventional technology shown in Figures 11(a) and 11(b). Note that in Figures 11(a) and 11(b), parts similar to those of the first embodiment shown in Figures 1, 5(a), and 5(b), etc., are designated by the same reference numerals. Figure 11(a) shows a conventional turbomolecular pump 600. This conventional turbomolecular pump 600 does not have the branched tubular part 242 shown in Figures 1, 5(a), and 5(b), etc. Figure 11(b) shows a cross section (horizontal cross section, planar cross section) of the connection between the inlet pipe 216 and the outer cylinder 127 in Figure 11(a) when viewed from the top (the side of the intake port 101) in Figure 5(a).

In the annular groove portion 632 of the prior art shown in Figures 11(a) and (b), the larger the width of the radical flow path (here, the length in the axial direction of the rotor shaft 113, etc.) and the larger the cross-sectional area that can be calculated using parameters such as that width, the lower the piping resistance and the easier it is to introduce radicals into the outer cylinder 127. Furthermore, in the case of the communication port 254, the smaller the cross-sectional area (opening area) is relative to the surface area of the annular groove portion 632, the more difficult it is for radicals to flow in, resulting in a greater number of collisions and revolutions of radicals.

Furthermore, because the communication port 254 opens at the bottom of the thread groove 131a, the diameter and cross-sectional area of the communication port 254 cannot be larger than the width of the thread groove 131a. Therefore, as the diameter and cross-sectional area of the communication port 254 increase, the width of the thread groove 131a must also increase. Furthermore, excessively increasing the width of the thread groove 131a affects the compression of the exhaust gas, reducing the performance of the turbomolecular pump 100. Therefore, there is an appropriate balance between the sizes of the annular groove 632 and the communication port 254, and the width of the annular groove 632 and the communication port 254 cannot be increased to the extent that this balance is disrupted. The same applies to the first embodiment shown in Figures 1 and 5(a), (b), etc., in that the larger the diameter and cross-sectional area of the communication port 254, the larger the width of the thread groove 131a must be.

Under these circumstances, the turbomolecular pump 100 according to the first embodiment (see, for example, Figures 1, 5(a), 5(b)) includes a branched tubular component 242, which constitutes a radical exhaust promotion structure, between the radical introduction port 218 connected to the plasma generator 210 and the communication port 254. Radicals are sent from the radical introduction port 218 to the communication port 254 via the branched tubular component 242. The area of the inner wall (inner surface) of the branched tubular component 242 is smaller than the area of the inner wall (inner surface) of the annular groove 232. Therefore, compared to conventional technology in which radicals collide with the inner wall of the annular groove 232, the area of the portion where radicals can collide can be reduced, preventing the radicals from being deactivated before flowing into the communication port 254. This enables the radicals to be utilized effectively.

Next, using Figure 8, we will present several examples of radical exhaust promotion structures and compare them with conventional structures. Figures 8(a1) and (a2) schematically show different types of radical exhaust promotion structures. Figures 8(b1) and (b2) also show schematic examples of conventional flow paths. The example in Figure 8(a1) uses a tapered pipe shape, and the example in Figure 8(b1) uses a stepped pipe shape. The example in Figure 8(a2) uses a curved pipe shape, and the example in Figure 8(b2) uses a branched pipe shape.

Of these, in the stepped pipe shape of Figure 8 (b1), which shows a conventional example, the cross-sectional area changes abruptly between the large-diameter portion 302, which has the inlet, and the small-diameter portion 304, which has the outlet. Radicals 306 traveling from the large-diameter portion 302 to the small-diameter portion 304 may collide with the wall at the step 308 between the large-diameter portion 302 and the small-diameter portion 304 and be reflected in the opposite direction. Furthermore, in order for these radicals 306 to enter the small-diameter portion 304, they must undergo one or more collisions within the large-diameter portion 302. Therefore, by the time these radicals 306 are able to enter the small-diameter portion 304, they have lost a significant degree of activity.

Here, arrows B1 and B2 in Figure (b1) indicate the direction in which radicals 306 should flow. Arrow C in Figure (b1) indicates the direction in which radicals 306 flow. These points are also true for Figures 8 (a1), (a2), and (b2).

In contrast to the stepped pipe shape described above, the tapered pipe shape of Figure 8 (a1), which shows an example of a radical exhaust promotion structure, has a cross-sectional area that gradually decreases from the inlet side to the outlet side. With this tapered pipe shape, even if radicals 306 are reflected on the inner wall, they are more likely to be reflected back in the flow direction, and the overall flow direction toward the outlet is maintained. Therefore, compared to the stepped pipe shape of Figure 8 (b1), the number of collisions of radicals 306 with the inner wall can be reduced, preventing deactivation of radicals 306 and enabling effective use of radicals.

Next, in the branch pipe shape of the example shown in Figure 8 (b2), which illustrates a conventional example, a branched structure is formed. A branch pipe section 314 with an outlet is connected perpendicularly to a portion of the main pipe section 312 with an inlet. In this branch pipe shape, radicals are generated that do not flow from the main pipe section 312 into the branch pipe section 314 but pass through the branch pipe section 314. If a radical 316 happens to flow into the branch pipe section 314, this radical 316 will head toward the outlet. In this branch pipe shape, the radical 316 may pass through the branch pipe section 314. If the main pipe section 312 is formed in a ring shape, the radical will circulate.

In contrast, in the curved pipe shape of the example shown in Figure 8(a2), which shows an example of a radical discharge promotion structure, the flow path does not branch, and radicals do not pass by without heading toward the outlet. This reduces the number of radical circulations and collisions with the inner wall, allowing radicals to be used effectively.

In the first embodiment shown in Figures 1, 5(a), (b), etc., the diameter of the opening at the inlet end 246 of the branched tubular part 242 is larger than the diameter of the opening at each outlet end 248a, 248b. Therefore, in this respect, the relationship between the inlet end 246 and the individual outlet ends 248a, 248b corresponds to the tapered tube shape of Figure 8(a1). Furthermore, in the first embodiment, the radical flow path does not branch from the annular groove 232 to the communication port 254, but rather connects directly from the radical inlet port 218 to the communication port 254. Therefore, the relationship between the inlet end 246 and the individual outlet ends 248a, 248b also corresponds to the curved tube shape of Figure 8(a2).

Based on this idea, the inventors have decided to refer to structures such as the branched tubular component 242 shown in Figures 1 and 5(a) and (b), as well as structures having tapered or curved pipe shapes such as those shown in Figures 8(a1) and (a2), as "radical exhaust promotion structures." By providing such "radical exhaust promotion structures" in the turbomolecular pump 100, radicals can be effectively utilized. The "radical exhaust promotion structure" can also be referred to as, for example, a "radical deactivation prevention structure," a "radical effective utilization structure," or a "structure for suppressing a sudden decrease in the flow path cross-sectional area." A radical flow path having a "radical exhaust promotion structure" can also be referred to as a "radical flow path portion having a radical exhaust promotion structure."

Increasing the number of communication ports 254 allows for more efficient introduction of radicals into the thread groove 131a. In this case, it is possible to increase the number of plasma generators 210 or the number of branches in the branch tubular part 242 in accordance with the increase in the number of communication ports 254. However, increasing the number of plasma generators 210 increases costs. In the first embodiment, the number of plasma generators 210 is three (three units, three devices, etc.), the number of branches in the branch tubular part 242 is two, and radicals are introduced into the thread groove 131a from six communication ports 254 (six locations). This makes it possible to effectively utilize radicals while keeping costs down.

Also, although not shown in the figures, radicals may be supplied from one plasma generator 210 to only one communication port 254. Furthermore, although also not shown in the figures, if the screw groove 131a has multiple threads, it is possible to provide one communication port 254 for each thread and to provide one plasma generator for each communication port 254.

Furthermore, in the first embodiment, the inlet end 246 and outlet end 248a, 248b of the branch tubular part 242 are formed with at least a portion curved in an arc. However, this is not limited to this. For example, the inlet end 246 and outlet end 248a, 248b may be formed as linearly as possible, and together with the main pipe portion 250, the entire pipe may be formed into a straight pipe. By doing so, the number of times radicals collide with the inner wall can be further reduced overall.

<Surface treatment for radical emission promoting structure>
The degree of deactivation due to radical collision is greater when the material of the collision surface (collision surface) is metal. Examples of metals include aluminum, iron, stainless steel, copper, and alloys containing these metals as components. For this reason, in the first embodiment, a non-metallized surface treatment is applied to the surface of the metal material with which radicals may collide. Examples of non-metallized surface treatments include anodizing and ceramic coating.

Examples of metal parts that may be hit by radicals include at least one of the branched tubular part 242, the threaded spacer 131, and the outer tube 127. Furthermore, examples of areas that may be subjected to the non-metallized surface treatment on the branched tubular part 242 include the entire branched tubular part 242 provided with a radical exhaust promotion structure, the inner wall surface, or a portion of the branched tubular part 242 including the inner wall surface.

Furthermore, examples of the target areas for the non-metallizing surface treatment on the threaded spacer 131 include the entire threaded spacer 131, the inner wall surface, or a portion of the threaded spacer 131 including the inner wall surface. Furthermore, examples of the target areas for the non-metallizing surface treatment on the outer tube 127 include the entire outer tube 127, the inner wall surface of the radical introduction port 128, or a portion of the outer tube 127 including the inner wall surface of the radical introduction port 128.

In this way, by applying a non-metallic surface treatment to at least a portion of the metal parts that radicals may collide with, the areas where radicals may collide can be non-metallicized. This further prevents radical deactivation, allowing the radicals to be used more effectively. The inlet pipe 216 may also be similarly subjected to a non-metallic surface treatment.

In the first embodiment, the annular groove 232 is formed in the threaded spacer 131, but this is not limited to this and it may be formed in other parts (vacuum pump components). Examples of other parts include the outer cylinder 127 and the base portion 129. The annular groove 232 may also be formed by combining grooves formed in multiple parts. Examples of multiple parts include combinations of the threaded spacer 131 and the outer cylinder 127, or the threaded spacer 131, the outer cylinder 127, and the base portion 129.

A tubular part (such as the branched tubular part 242) having a radical exhaust-promoting structure can be provided in the annular groove 232 thus formed. The tubular part (such as the branched tubular part 242) can be disposed in any vacuum pump component, or the tubular part (such as the branched tubular part 242) can be provided so as to span multiple vacuum pump components. In other words, a tubular part (such as the annular groove 232) can be disposed in a groove (such as the annular groove 232) provided in at least one of the casing (such as the outer cylinder 127, base 129, or combination of the outer cylinder 127 and base 129 that constitute the casing) and the exhaust mechanism (such as the threaded spacer 131 that constitutes the Holweck-type exhaust mechanism 204).

Second Embodiment
Next, a second embodiment of the vacuum pump of the present invention will be described. Note that parts similar to those in the first embodiment are given the same reference numerals, or the reference numerals are omitted and descriptions thereof will be omitted as appropriate. Fig. 9(a) shows a longitudinal section of a turbomolecular pump 400 according to the second embodiment, and Fig. 9(b) shows a cross section (planar cross section) of the connection portion between the inlet pipe 216 and the outer cylinder 127 in Fig. 9(a) as viewed from the top (the side of the intake port 101) in Fig. 9(a).

In the second embodiment, the radical exhaust promotion structure is formed by an arc-shaped groove 432 in the threaded spacer 131. The arc-shaped groove 432 is an arc-shaped space that extends circumferentially on the outer peripheral surface of the threaded spacer 131. There are three arc-shaped grooves 432, arranged at 120-degree intervals. Figure 9(b) shows only one arc-shaped groove 432. The arc-shaped groove 432 faces the inner peripheral surface of the outer cylinder 127 and is defined by the threaded spacer 131 and the outer cylinder 127.

The arc-shaped groove 432 has an arc-shaped main flow path portion 450 and each end portion 428a, 428b. The main flow path portion 450 is spatially connected to the radical introduction port 218 of the outer cylinder 127 at the center portion 426 in the longitudinal direction (circumferential direction of the threaded spacer 131).

A guide portion 482 is provided on the inner wall of the arc-shaped groove portion 432 in a portion facing the radical introduction port 218. The guide portion 482 is formed by processing a plate-shaped material into a shape with a sharp protrusion 452 in the center, and is fixed to the inner wall of the arc-shaped groove portion 432 via multiple screws 484. The tip of the protrusion 452 faces toward the center of the radical introduction port 218.

The guide portion 482 can be made of a metal. Examples of metals include aluminum, iron, stainless steel, copper, and alloys containing these metals.

Each end 428a, 428b of the arc-shaped groove 432 is at least partially formed in an arc shape and spatially connected to the communication port 454 provided in the threaded spacer 131. As shown in Figure 9(b), each end 428a, 428b of the arc-shaped groove 432 is formed in an arc shape and closes (is closed) at a position where it spatially connects from the radical introduction port 218 to the communication port 454.

The communication openings 454 penetrate the bottom of the arc-shaped groove portion 432 in the threaded spacer 131, spatially connecting the thread groove 131a with the interior of the arc-shaped groove portion 432. Two communication openings 454 are formed for each arc-shaped groove portion 432. In this embodiment, a total of six (= 2 x 3) communication openings 454 are provided around the entire circumference of the threaded spacer 131. The communication openings 454 are arranged symmetrically in pairs, every 120 degrees around the circumference of the threaded spacer 131.

The diameter (inner diameter) of the opening (here, a circular opening) at the communication port 454 is smaller than the diameter (inner diameter) of the opening (here, a circular opening) at the radical introduction port 218. Furthermore, the arc-shaped groove 432 is formed so that the inner wall is smoothly continuous from the main flow path portion 450 to each end portion 428a, 428b and the communication port 454, with as few steps as possible. Furthermore, the main flow path portion 450 and each end portion 428a, 428b are formed so that the size of the flow path (cross-sectional area, flow area) changes as little as possible. In this way, the arc-shaped groove 432 connects the radical introduction port 218 located in the outer cylinder 127 to the communication port 454 located in the threaded spacer 131.

The radicals generated by the plasma generator 210 flow into the arc-shaped groove 432 through the valve device 214, which is controlled to an open state, and the inlet pipe 216. The radicals that flow into the arc-shaped groove 432 are diverted along the shape of the guide section 482 and guided along the length of the arc-shaped groove 432. Furthermore, the radicals flow toward the communication port 454 at each end 428a, 428b of the arc-shaped groove 432, pass through the communication port 454, and are discharged into the thread groove 131a. The radicals discharged into the thread groove 131a primarily clean areas such as the thread groove pump mechanism (Hollweck-type exhaust mechanism 204) and the boundary between the thread groove pump mechanism (Hollweck-type exhaust mechanism 204) and the turbomolecular pump mechanism 138.

In this second embodiment, as in the first embodiment, non-metallizing surface treatment is performed on metal components with which radicals may collide. Examples of non-metallizing surface treatments include anodizing and ceramic coating. Examples of metal components with which radicals may collide include the threaded spacer 131 with the arc-shaped groove 432 formed therein, the guide portion 482 and screw 484 fixed to the threaded spacer 131, and the outer cylinder 127 with the radical introduction port 128 formed therein.

The target areas of the non-metallized surface treatment on the guide portion 482 and the screw 484 include the entire guide portion 482 and the screw 484, as well as portions where radicals may collide. The target areas of the non-metallized surface treatment on the threaded spacer 131 and the outer tube 127 are the same as those in the first embodiment.

In this way, by applying a demetallizing surface treatment to at least a portion of a metal part that may be hit by radicals, the areas that may be hit by radicals can be demetallized. This further prevents radicals from being deactivated, allowing them to be used more effectively.

As described above, the turbomolecular pump 400 of the second embodiment can introduce radicals directly from the radical introduction port 218 to the communication port 454 without significantly dispersing or circulating them. This makes it possible to achieve the same effects as the first embodiment. Furthermore, because the radical exhaust promotion structure is formed directly in the arc-shaped groove portion 432 of the threaded spacer 131, a component with a complex shape, such as the branched tubular component 242 of the first embodiment, is not required. The radical exhaust promotion structure of the arc-shaped groove portion 432 of the second embodiment also corresponds to the tapered pipe shape of Figure 8(a1) or the curved pipe shape of Figure 8(a2).

In the second embodiment, the arc-shaped groove 432 is formed in the threaded spacer 131, but this is not limited to this and it may be formed in other parts (vacuum pump components). Examples of other parts include the outer cylinder 127 and the base portion 129. The arc-shaped groove 432 may also be formed by combining grooves formed in multiple parts. Examples of multiple parts include combinations of the threaded spacer 131 and the outer cylinder 127, or the threaded spacer 131, the outer cylinder 127, and the base portion 129.

The arc-shaped groove 432 formed in this manner can form a radical exhaust promotion structure. The groove (such as the arc-shaped groove 432) can be formed in any of the vacuum pump components, or the groove (such as the arc-shaped groove 432) can be formed across multiple vacuum pump components. In other words, the radical exhaust promotion structure can be formed by a groove (such as the arc-shaped groove 432) provided in at least one of the casing (such as the outer cylinder 127, base 129, or combination of the outer cylinder 127 and base 129 that form the casing) and the exhaust mechanism (such as the threaded spacer 131 that forms the Holweck-type exhaust mechanism 204).

In addition, in the first and second embodiments, the number of plasma generators 210 is three (three units, three devices, etc.), the number of branches in the branched tubular part 242 and the arc-shaped groove portion 432 is two, and radicals are introduced into the thread groove 131a from six (six locations) communication ports 254, 454, which is greater than the number of plasma generators 210. Regarding the relationship between the number of thread grooves 131a and the number of communication ports 254, 454, ideally, one communication port 254 is provided for each thread groove 131a. In the first and second embodiments, by appropriately setting the number of branches in the branched tubular part 242, a structure is realized that allows radicals to be introduced into each thread groove 131a.

Third Embodiment
Next, a third embodiment of the vacuum pump of the present invention will be described. The same reference numerals are used to designate the same parts as those in the first or second embodiment, or the reference numerals are omitted and the description thereof will be omitted as appropriate. Fig. 10 shows a longitudinal section of a turbomolecular pump 500 according to the second embodiment.

In the first and second embodiments, a Holweck-type exhaust mechanism 204 was provided as the thread groove pump mechanism of the exhaust mechanism 137. However, in the third embodiment, a Sigburn-type exhaust mechanism 504 is provided as the thread groove pump mechanism of the exhaust mechanism 137. The third embodiment combines a turbomolecular pump equipped with a Sigburn-type exhaust mechanism 504 with a radical exhaust promotion structure such as that of the first or second embodiment. Figure 10 shows the Sigburn-type exhaust mechanism 504, and to avoid cluttering the illustration, the radical exhaust promotion structure such as that of the first or second embodiment is omitted.

In the Sigburn exhaust mechanism 504, multiple spiral groove channels 514 separated by ridges 512 are formed in the gap between the rotating disks 506a and 506b mounted on the rotor 103 and the fixed disks 510a and 510b mounted on the spacers 508a and 508b. The Sigburn exhaust mechanism 504 imparts tangential momentum to gas molecules diffused within the spiral groove channels 514 via the rotating disks 506a and 506b, and the spiral groove channels 514 provide preferential directionality in the exhaust direction, thereby exhausting the gas.

The ridges 512 and spiral groove channels 514 are provided on at least one of the rotating disks 506a, 506b and the fixed disks 510a, 510b. A general structure can be used for the Sigburn-type exhaust mechanism 504.

A radical exhaust promotion structure can also be applied to the plasma flow path connected to this Sigburn-type exhaust mechanism 504. In the third embodiment, the inlet pipe 216 enters the radical introduction port 218 provided in the outer cylinder 127. An arc-shaped groove 532 is formed on the outer peripheral surface at the boundary between spacers 508a and 508b. In the third embodiment, the arc-shaped groove 532 has a radical exhaust promotion structure similar to the arc-shaped groove 432 of the second embodiment (Figures 9(a) and (b)). The third embodiment also includes the guide 482 and the like of the second embodiment, but the guide 482 and the like are not shown in Figure 10.

As in the second embodiment, the arc-shaped groove 532 is spatially connected to the radical introduction port 218. Also, as in the second embodiment, communication ports 554 are spatially connected to both ends of the arc-shaped groove 532. The communication ports 554 open, for example in a perfect circle, facing the space between the fixed disks 510a and 510b, and are spatially connected to the spiral groove channels 514 formed on both plate surfaces of one of the fixed disks 510b (the fixed disk 510b located on the exhaust side of the turbomolecular pump 500, out of the fixed disks 510a and 510b). In this way, the arc-shaped groove 532 connects the radical introduction port 218 located in the outer cylinder 127 to the communication port 554 formed between the spacers 508a and 508b.

The radicals generated by the plasma generator 210 flow into the arc-shaped groove 532 through the valve device 214, which is controlled to an open state, and the inlet pipe 216. The radicals that flow into the arc-shaped groove 532 flow along the arc-shaped groove 532 and are discharged into the spiral groove flow path 514 through the communication port 554. The radicals discharged into the spiral groove flow path 514 mainly clean areas such as the thread groove pump mechanism (Sigburn-type exhaust mechanism 504) and the exhaust port 133.

The radical exhaust promotion structure according to the third embodiment may also be formed by providing a piping component (e.g., branched tubular component 242) similar to that of the first embodiment, and connecting the radical introduction port 218 and the communication port 554 using this piping component.

In this third embodiment, as in the first and second embodiments, a non-metallizing surface treatment is performed on metal components that may be hit by radicals. Examples of non-metallizing surface treatments include anodizing and ceramic coating. An example of a metal component that may be hit by radicals is the threaded spacer 131, which has an arc-shaped groove 532 formed therein. The target area of the non-metallizing surface treatment on the threaded spacer 131 is the same as in the first and second embodiments. Furthermore, if a radical exhaust promotion structure similar to that in the first and second embodiments is adopted, it is possible to perform a non-metallizing surface treatment, as in the first and second embodiments.

In this way, by applying a demetallizing surface treatment to at least a portion of a metal part that may be hit by radicals, the areas that may be hit by radicals can be demetallized. This further prevents radicals from being deactivated, allowing them to be used more effectively.

The turbomolecular pump 500 of the third embodiment described above allows radicals to be introduced directly from the radical introduction port 218 to the communication port 554 without being significantly dispersed or circulated. Furthermore, even in a turbomolecular pump 500 equipped with a Sigburn-type exhaust mechanism 504, it is possible to achieve the same effects as the second embodiment (or first embodiment).

<Inventions that can be extracted from each embodiment>
The following inventions can be extracted from the above-described embodiments.
(1) An exhaust mechanism (such as a turbomolecular pump mechanism unit 138 and a Holweck-type exhaust mechanism unit 204, or a turbomolecular pump mechanism unit 138 and a Sigburn-type exhaust mechanism unit 504) including a rotatable rotor (such as the rotor 103) and a stator (such as the fixed blades 123) combined with the rotor;
a vacuum pump (turbomolecular pump 100, 400, 500, etc.) including a casing (a combination of an outer cylinder 127 and a base portion 129, the outer cylinder 127, the base portion 129, etc.) that contains the exhaust mechanism,
a radical exhaust promotion structure that connects a radical introduction port (radical introduction port 218, etc.) arranged in the casing and a communication port (communication port 254, 454, 554, etc.) arranged in the exhaust mechanism.
(2) The vacuum pump according to (1) above, wherein the radical exhaust promotion structure is constituted by a tubular part (such as the branched tubular part 242).
(3) The vacuum pump according to (1) above, wherein the radical exhaust promotion structure is formed by a groove (such as an arc-shaped groove 432) provided in at least one of the casing (such as the outer cylinder 127, base 129, or combination of the outer cylinder 127 and base 129 constituting the casing) and the exhaust mechanism (such as the threaded spacer 131 constituting the Holweck-type exhaust mechanism 204).
(4) The vacuum pump according to (3) above, wherein the groove is closed at a position where the radical introduction port is spatially connected to the communication port.
(5) The vacuum pump according to (3) above, wherein the groove is provided with a guide portion (such as guide portion 482) that guides the radicals that have passed through the radical introduction port toward the communication port.
(6) The vacuum pump according to any one of (1) to (5) above, wherein at least a portion of at least one of the radical exhaust promotion structure, the communication port, and the radical introduction port is anodized.
(7) A vacuum pump according to any one of (1) to (5) above, characterized in that at least a portion of at least one of the radical exhaust promotion structure, the communication port, and the radical introduction port is ceramic coated.
(8) an exhaust mechanism (such as the turbomolecular pump mechanism 138 and the Holweck-type exhaust mechanism 204, or the turbomolecular pump mechanism 138 and the Sigburn-type exhaust mechanism 504) including a rotatable rotor (such as the rotor 103) and a stator (such as the fixed blades 123) combined with the rotor;
a casing (a combination of an outer cylinder 127 and a base 129, the outer cylinder 127, the base 129, a combination of the threaded spacer 131 and the outer cylinder 127, etc.) that houses the exhaust mechanism,
a radical introduction port (e.g., radical introduction port 218) disposed in the casing;
A vacuum pump component characterized in that it is provided with a radical exhaust promotion structure that connects to a communication port (communication port 254, 454, 554, etc.) arranged in the exhaust mechanism.
(9) A vacuum pump component according to (8) above, characterized in that it is a tubular component (such as the branched tubular component 242) on which the radical exhaust promotion structure is formed.
(10) A vacuum pump component according to (8) above, characterized in that it is a component constituting at least one of the casing and the exhaust mechanism (such as the outer cylinder 127, the threaded spacer 131, the base portion 129, or a combination of the threaded spacer 131 and the outer cylinder 127).

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

100, 400, 500: turbomolecular pump 102: rotor 103: rotor 127: outer cylinder 129: base 131: threaded spacer 136: rotation mechanism 137: exhaust mechanism 138: turbomolecular pump mechanism 204: Holweck type exhaust mechanism 210: plasma generator 214: valve device 216: introduction pipe 218: radical introduction port 232, 532: annular groove 242: branched tubular part 252: protrusion 254, 454, 554: communication port 432: arc-shaped groove 482: guide 504: Sigbahn type exhaust mechanism

Claims (10)

an exhaust mechanism including a rotatable rotor and a stator combined with the rotor;
a casing that houses the exhaust mechanism,
a radical exhaust promotion structure is provided that spatially connects a radical introduction port disposed in the casing and a communication port disposed in the exhaust mechanism ;
The radical discharge promoting structure guides the radicals from the radical introduction port to the corresponding communication port without dispersing the radicals beyond the communication port.
A vacuum pump characterized by: 2. The vacuum pump according to claim 1, wherein the radical exhaust promoting structure is formed of a tubular part. 2. The vacuum pump according to claim 1, wherein the radical exhaust promotion structure is formed by a groove provided in at least one of the casing and the exhaust mechanism. an exhaust mechanism including a rotatable rotor and a stator combined with the rotor;
a casing that houses the exhaust mechanism,
a radical exhaust promotion structure is provided that spatially connects a radical introduction port disposed in the casing and a communication port disposed in the exhaust mechanism;
the radical exhaust promotion structure is configured by a groove provided in at least one of the casing and the exhaust mechanism,
A vacuum pump characterized in that the groove is closed at a position where the radical introduction port is spatially connected to the communication port. 4. The vacuum pump according to claim 3, wherein the groove is provided with a guide portion that guides the radicals that have passed through the radical introduction port toward the communication port. 6. The vacuum pump according to claim 1, wherein at least a portion of at least one of the radical exhaust promotion structure, the communication port, and the radical introduction port is anodized. 6. The vacuum pump according to claim 1, wherein at least a portion of at least one of the radical exhaust promotion structure, the communication port, and the radical introduction port is ceramic coated. an exhaust mechanism including a rotatable rotor and a stator combined with the rotor;
a casing that houses the exhaust mechanism,
a radical exhaust promotion structure is provided that spatially connects a radical introduction port disposed in the casing and a communication port disposed in the exhaust mechanism ;
The radical discharge promoting structure guides the radicals from the radical introduction port to the corresponding communication port without dispersing the radicals beyond the communication port.
A vacuum pump component characterized by: 9. The vacuum pump component according to claim 8, wherein the radical exhaust promoting structure is a tubular component formed thereon. 9. A vacuum pump component according to claim 8, which is a component constituting at least one of the casing and the exhaust mechanism.