Apparatus and method for monitoring deposits of reaction by-products in the exhaust path of a turbo molecular vacuum pump

Abstract

An apparatus and method for monitoring the deposition of reaction by-products is provided. [Solution] An apparatus (200) for monitoring the deposition of reaction by-products in an exhaust path (7) of a vacuum pump (1; 100) comprises a thermal flow meter (20) including a first temperature probe arranged at an upstream position in the gas flow direction in the exhaust path (7), a second temperature probe arranged at a downstream position, a heating element arranged between the two temperature probes, and an insulating substrate that insulates the temperature probes and the heating element from each other, and a processing unit (22) configured to perform measurements by the thermal flow meter (20) and determine the presence of deposition of reaction by-products in the exhaust path (7) as a function of the difference between the flow rate measured by the thermal flow meter (20) and an estimate of the gas flow rate pumped by the vacuum pump (1; 100).

Description

Technical Field

[0001] The present invention relates to an apparatus and a method for monitoring deposits of reaction by-products in an exhaust passage of a vacuum pump. The present invention also relates to a vacuum pump provided with the monitoring apparatus.

Background Art

[0002] In vacuum applications, particularly in the semiconductor industry or thin film deposition processes, vacuum pumps convey various types of gases and evaporative substances that may deposit on the inner surface of the vacuum pump due to changes in pressure or temperature conditions, or changes in the nature of chemical reactions.

[0003] These deposits of reaction by-products are solids, polymers, or even dust. These deposits tend to accumulate particularly in the high-pressure zones or low-temperature zones of the vacuum pump. They can reduce the dimensions of the gas passage portion, thereby potentially degrading pump performance. This reduction in the dimensions of the gas passage portion can also cause a further increase in pressure, which, due to the cascade effect, may cause more deposits of reaction by-products.

[0004] Therefore, it is necessary to frequently schedule regular maintenance to clean the vacuum pump. However, such frequent maintenance is not compatible with the requirements of the production speed. As a result, there is a need to monitor the formation of deposits in the vacuum pump in order to maximize the maintenance interval. However, one of the difficulties is that the interior of the vacuum pump cannot be observed without stopping the vacuum pump to disassemble all or part of it. Furthermore, depending on the application, exposing the interior of the vacuum pump to the outside air can be dangerous.

Summary of the Invention

Problems to be Solved by the Invention

[0005] Many known sensor technologies can monitor these deposits and the growth of deposits within the vacuum pump. In the case of a turbo molecular vacuum pump, one of the known methods is to measure the current of the motor or the position of the magnetically levitated rotor to determine the possibility of the presence of reaction by-products. Changes in the motor current or the position of the magnetically levitated rotor can provide information regarding the presence of deposits. However, this method may not be accurate enough. In particular, generally the increase in current is very slow and the increase is detected only a few seconds or just an instant before destruction, so intervention may not be in time.

[0006] Therefore, one of the objects of the present invention is to propose an apparatus and method for monitoring deposits of reaction by-products that at least partially solve one of the above-mentioned drawbacks.

Means for Solving the Problems

[0007] For this purpose, one main subject of the present invention is an apparatus for monitoring deposits of reaction by-products in the exhaust passage of a vacuum pump, the apparatus includes a thermal flow meter and a processing unit, the thermal flow meter, includes a first temperature probe disposed at an upstream position in the gas flow direction in the exhaust passage, a second temperature probe disposed at a downstream position, a heating element interposed between the two temperature probes, and an insulating substrate for insulating each of the temperature probes from the heating element, the processing unit, is configured to perform measurements by the thermal flow meter and determine the presence of deposits of the reaction by-products in the exhaust passage as a function of the difference between the flow rate measured by the thermal flow meter and an estimated value of the gas flow rate pumped by the vacuum pump.

[0008] The monitoring apparatus of the present invention enables detection of the presence of deposits in the exhaust passage of a vacuum pump more accurately and at the earliest possible time.

[0009] The monitoring device can further include one or more of the features described below, either alone or in combination. The thermal flowmeter can be a MEMS component. The monitoring device can further include a pressure sensor configured to determine the pressure in the exhaust path of the vacuum pump, and the processing unit is configured to estimate the pumped gas flow rate based on information regarding the power parameters of the motor and the measurement values from the pressure sensor. And it is possible to obtain an estimated value of the pumped gas flow rate only based on the information obtained from the vacuum pump, that is, without accessing information regarding the amount and properties of the gas introduced upstream of the vacuum pump.

[0010] The power parameter of the motor of the vacuum pump can be current. The processing unit can be configured to estimate the pumped gas flow rate in communication with the process chamber evacuated by the vacuum pump. And the value of the pumped gas flow rate can be accurately estimated based on the information transmitted to the processing unit by the process chamber.

[0011] Another subject of the present invention is A vacuum pump including a stator including an inlet orifice and an outlet orifice, and at least one rotor disposed within the stator and configured to drive the gas pumped between the inlet orifice and the outlet orifice, wherein the vacuum pump further includes the monitoring device, and the thermal flowmeter is disposed inside the vacuum pump. This monitoring device enables more accurate detection of the presence of deposits in the exhaust path of a vacuum pump at the earliest possible time, and enables more appropriate management of maintenance scheduling. The monitoring can be performed on-site, i.e., without disassembling the vacuum pump. The measuring device is non-invasive. There is no pressure loss or seal loss. Since there are no moving parts, the possibility of malfunction is limited. The thermal flowmeter is arranged, for example, in the exhaust duct. The vacuum pump is, for example, a turbomolecular vacuum pump. According to another embodiment of the present invention, the vacuum pump is a roughing vacuum pump comprising a pair of rotors configured to rotate synchronously in opposite directions in at least one pumping stage to drive the gas pumped between the inlet orifice and the outlet orifice.

[0012] A further subject of the present invention is a method for monitoring deposits of reaction by-products in the exhaust path of a vacuum pump by means of the monitoring device, wherein the measurement is carried out by a thermal flowmeter, and the presence of deposits of reaction by-products in the exhaust path is determined as a function of the difference between the flow rate measured by this thermal flowmeter and the estimated value of the gas flow rate pumped by the vacuum pump.

[0013] Power is supplied to the heating element of the thermal flowmeter to perform measurements at intervals of 10 hours or more as daily measurements. The measurement time by the thermal flowmeter can be less than a few minutes, such as less than 2 minutes and even less than 1 minute. The highest deposition rate observed in semiconductor manufacturing processes such as turbomolecular vacuum pumps, especially etching devices, is generally less than 1 mm per week, i.e., about 5 μm per hour. Therefore, observing the appearance of the deposits is sufficient with a relatively low measurement frequency. By limiting the measurement period to a few seconds per day, it is possible to prevent the deposition of condensable species at the point of the thermal flowmeter due to the heat input from the thermal heating element, and to prevent the results from being tampered with by the measurements performed by the thermal flowmeter. In fact, the deposits decrease at high temperatures and may even be absent. The thickness of the deposit can be evaluated as a function of the deviation value of the measurement value from the thermal flowmeter.

[0014] The method of monitoring the deposit can include a preliminary calibration step in which at least one measurement value from the thermal flowmeter obtained for a predetermined gas flow rate in the vacuum pump is recorded. The various data that can be collected in this preliminary calibration step, in particular, the values of the pumped gas flow rate, the pumped gas species, the nature of the deposit, and as a function of the thickness of the deposit, can more appropriately interpret the values measured by the thermal flowmeter.

[0015] These measurements can be performed for the values of the gas flow rate and properties defined in the recipe executed in the process chamber connected to the vacuum pump, particularly for the characteristic steps of these recipes. For example, if the monitoring method is a measurement performed on a specific date and the gas flow rate and the nature of the gas being pumped at that time are known, the preliminary calibration step can record the measurement values of the gas flow rate and the nature of the gas at a specific operating time point obtained by the thermal flowmeter. Other objects, features, and advantages of the present invention will become apparent from the following description of the detailed embodiments given with reference to the accompanying drawings.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Best Mode for Carrying Out the Invention

[0017] In each figure, the same elements are given the same reference numerals. For ease of understanding, the drawings are simplified. The following embodiments are examples. The description refers to one or more embodiments, but this does not necessarily mean that each reference relates to the same embodiment or that the features apply only to a single embodiment. It is also possible to provide other embodiments by combining or exchanging simple features of different embodiments. "Upstream" means an element arranged in front of another element with respect to the gas flow direction. On the other hand, "downstream" means an element arranged behind with respect to the circulation direction of the pumped gas.

[0018] FIG. 1 shows, for example, an example of an apparatus 101 for manufacturing a flat display screen or a photovoltaic substrate or a semiconductor substrate (wafer). This apparatus 101 includes a process chamber 102 connected to a vacuum line, and this vacuum line includes a roughing vacuum pump 100 and a turbomolecular vacuum pump 1 arranged upstream of this roughing vacuum pump and connected by an exhaust pipe 103. Also, in FIG. 1, it can be seen that the vacuum line is provided with a monitoring device 200 for monitoring the deposition of reaction by-products in the exhaust path 7 of the turbomolecular vacuum pump 1. This monitoring device 200 includes a thermal flowmeter 20 and a processing unit 22.

[0019] The thermal flowmeter 20 can be arranged in the exhaust path 7 of the turbo molecular vacuum pump 1 or on the turbo molecular vacuum pump 1 itself. This will be described later. Alternatively, as shown in FIG. 1, the thermal flowmeter 20 can be arranged in the exhaust pipe 103 connected to the outlet of the turbo molecular vacuum pump 1. Alternatively, it can also be arranged in the exhaust path of the roughing vacuum pump 100, inside the roughing vacuum pump 100, or in a pipe connected to the outlet of the roughing vacuum pump 100. In the first embodiment of FIG. 1, the thermal flowmeter 20 is arranged in the exhaust pipe 103 connected to the outlet orifice 8 of the turbo molecular vacuum pump 1. The thermal flowmeter 20 is used to measure the gas flow rate flowing in a duct or pipe. The principle of the thermal flowmeter 20 is based on the heat propagation by convection through a fluid. As is known per se, the thermal flowmeter 20 is provided with two temperature probes. That is, as shown in FIG. 2, it includes a first temperature probe 23 arranged at an upstream position in the gas flow direction in the exhaust path 7 and a second temperature probe 24 arranged at a downstream position.

[0020] The thermal flowmeter 20 also includes one heating element 25 arranged between the two temperature probes 23, 24 and an insulating substrate 26 that insulates the temperature probes 23, 24 from each other and from the heating element 25. The heating element 25 is, for example, a heating resistor. The temperature probes 23, 24 are, for example, thermistors. The insulating substrate 26, for example, encapsulates the temperature probes 23, 24, electrically and thermally insulates these temperature probes 23, 24 from each other, and protects them from the attack of the gas. The temperature probes 23, 24 are arranged, for example, at an equal distance from the heating element 25. The temperature probes 23, 24 and the heating element 25 can be aligned along a straight line parallel to the axis of the exhaust pipe 103 in which the thermal flowmeter 20 is arranged inside. To perform the measurement by the thermal flowmeter 20, power is supplied to the heating element 25 heated, for example, up to 100°C, and the temperature difference between the temperature probes 23, 24 is measured.

[0021] When no gas is flowing in the exhaust pipe 103, the heat diffused by the heating element 25 is uniformly distributed around the heating element 25 (see Fig. 2). The temperature probes 23 and 24 can measure zero, which is the first temperature difference, when these temperature probes 23 and 24 are equidistant from the heating element 25.

[0022] When a gas flow flows through the exhaust pipe 103, due to heat convection, the temperature measured by the first temperature probe 23 arranged upstream decreases, and the temperature measured by the second temperature probe 24 arranged downstream increases (see Fig. 3). And a temperature difference larger than the temperature difference observable when there is no circulation of the gas flow is observed between the temperature probes 23 and 24. Based on this temperature difference, the measured value of the gas flow rate can be estimated. The thermal flowmeter 20 can be a MEMS (Micro Electro Mechanical Systems) component manufactured from a semiconductor material. In that case, the size of the thermal flowmeter 20 is less than 1 cm.

[0023] The processing unit 22 includes a controller or a microcontroller or a computer or a programmable logic controller and a computer program, and the computer program is configured to implement a method for monitoring the deposits of reaction by-products in the exhaust path of the vacuum pump 1. The processing unit 22 is, for example, a controller of the vacuum pump 1, and can particularly control the rotation speed of the rotor of the vacuum pump 1. The processing unit 22 is configured to perform the measurement by the thermal flowmeter 20 and determine the presence of deposits of reaction by-products in the exhaust path 7 as a function of the difference between the flow rate measured by this thermal flowmeter 20 and the estimated value of the gas flow rate pumped by the vacuum pump 1.

[0024] The estimated value of the pumped gas flow rate can be obtained only based on the information available from the vacuum pump 1, that is, without accessing the information regarding the amount and properties of the gas introduced upstream of the vacuum pump 1. Therefore, according to an exemplary embodiment, the monitoring device 200 includes a pressure sensor 21 configured to determine the pressure in the exhaust passage 7 of the vacuum pump 1 (see FIG. 1). The processing unit 22 is further configured to estimate the pumped gas flow rate from information regarding the power parameters of the motor 16 of the vacuum pump 1 and the measured values of the pressure sensor 21. The power parameter of the motor 16 of the vacuum pump 1 is, for example, current. The current consumed by the motor 16 and the pressure in the exhaust passage 7 of the vacuum pump 1 depend on the gas flow rate and the properties of the gas being pumped. By measuring the pressure in the exhaust passage 7 and knowing the current consumed by the motor 16, it is possible to estimate the pumped gas flow rate value for comparison with the value measured by the thermal flow meter 20.

[0025] According to another exemplary embodiment, the processing unit 22 communicates with the process chamber 102 evacuated by the vacuum pump 1 and is configured to estimate the exhaust gas flow rate. The process chamber 102 uses a recipe that defines the duration, properties, flow rate, and pressure of the gas introduced into this chamber. These recipes or elements of these recipes are information that can be transmitted by the process chamber 102 to the processing unit 22, and the processing unit 22 can accurately estimate the pumped gas flow rate value. The information transmitted by the process chamber 102 is a digital signal or a dry contact, etc.

[0026] The change in the difference between the value measured by the thermal flow meter 20 and the estimated value of the pumped gas flow rate enables determination of the presence of the deposit 27 of reaction by-products in the exhaust pipe 103 (see FIG. 4). In fact, when there is no deposit, for example, for the same flow and the same gas properties identified by pressure measurement and the consumed motor current, the temperature difference measured by the two temperature probes 23, 24 is the same. However, when deposits 27 appear on the inner wall of the exhaust pipe 103, particularly on the thermal flowmeter 20, a change is observed in the measured temperature difference. The layer of deposits 27 deposited on the temperature probes 23, 24 reduces the heat transfer to the second temperature probe 24 arranged downstream (see Fig. 4). The temperature measured by the second temperature probe 24 also decreases even in the absence of deposits for the same flow of the same gas (see Fig. 3). Therefore, the flow rate measured by the thermal flowmeter 20 is different when deposits are present for the same flow rate of the same gas.

[0027] The observed difference between the flow rate measured by this thermal flowmeter 20 and the estimated value of the gas flow rate pumped based on the pressure measurement and the value of the consumption current can lead to the conclusion of the presence of deposits 27 of the reaction by-products. The duration of one measurement by the thermal flowmeter 20 may be less than 2 minutes, for example less than 1 minute. The measurement is performed by the thermal flowmeter 20 at time intervals of 10 hours or more, for example, in daily measurements. The highest deposition rate observed in the turbo molecular vacuum pump 1, particularly in semiconductor manufacturing processes such as etching apparatuses, is generally less than 1 mm per week, that is, less than about 5 μm per hour. By limiting the duration of the measurement to a few seconds per day, deposition of condensable species at the point of the thermal flowmeter 20 due to the heat from the heating element 25 is prevented, so that the measurement results obtained by the thermal flowmeter 20 will not be incorrect. In fact, the deposits decrease at high temperatures and may even be absent.

[0028] It is also possible to evaluate the thickness of the deposits 27 as a function of the deviation value of the measured value given by the thermal flowmeter 20. The greater the deviation from the expected value of the temperature difference measured by the thermal flowmeter 20, the thicker the deposits 27.

[0029] The monitoring method can include a preliminary calibration step in which at least one measured value from the thermal flowmeter 20 is recorded in the processing unit 22. This measured value is obtained for a predetermined flow rate of the gas pumped by the vacuum pump 1. For example, several measurements from the thermal flowmeter 20 are recorded for different gas flows and / or different gas species pumped by the vacuum pump 1. These measurements can be performed for the values of the gas flow rate and the properties of the gas defined in the recipe executed within the process chamber 102 connected to the vacuum pump 1. These measurements can be performed for the characteristic steps of these recipes. For example, if the monitoring method is a measurement performed on a specific date and the gas flow rate and the properties of the gas being pumped at that time are known, the preliminary calibration step can record the measurement values obtained by the thermal flowmeter 20 for the gas flow rate and the properties of the gas at that specific operating point. These measurements can be performed, for example, for some thicknesses of the deposit 27 in a state where the deposit 27 exists on the inner wall of the exhaust pipe 103, and the thicknesses of these deposits 27 can be evaluated as a function for determining the deviation of the measurement values from the thermal flowmeter 20. These measurements can also be performed, for example, at startup after each maintenance operation, in a state where there is no deposit in the exhaust pipe 103. These measurement values executed during the monitoring method can be compared with their reference values.

[0030] With various data that can be collected during the preliminary calibration step, the values measured by the thermal flowmeter 20 can be interpreted more appropriately. In particular, it can be interpreted appropriately as a function of the pumped gas flow rate, the pumped gas species, the properties of the gas, and the thickness of the deposit. From the above description, it can be understood that the monitoring method and apparatus of this embodiment can detect the presence of deposits in the exhaust path 7 of the vacuum pump 1 more accurately and at the earliest possible time.

[0031] FIG. 5 shows a second exemplary embodiment of the present invention in which the thermal flowmeter 20 is disposed inside the turbo molecular vacuum pump 1. As can be seen more specifically in this figure, the turbomolecular vacuum pump 1 includes a stator 2 and a rotor 3 disposed within this stator 2, and is configured to drive the gas pumped between the inlet orifice 6 and the outlet orifice 8 of the stator 2 in the direction of the gas flow, represented by the arrow in FIG. 5. The vacuum pump 1 includes a turbomolecular stage 4 and a molecular stage 5 located downstream of the turbomolecular stage 4 in the gas flow direction. The gas to be pumped enters from the inlet orifice 6, first passes through the turbomolecular stage 4, then through the molecular stage 5, and then through the exhaust passage 7, and is exhausted from the outlet orifice 8 of the vacuum pump 1. This orifice 8 is connected to a roughing pump.

[0032] In the turbomolecular stage 4, the rotor 3 includes at least two stages of blades 9, and the stator 2 includes at least one stage of fins 10. A plurality of stages of the blades 9 and a plurality of stages of the fins 10 are axially consecutive to each other along the rotation axis I-I of the rotor 3 within the turbomolecular stage 4. The rotor 3 is provided with four or more stages of blades 9, such as four to eight stages (six stages in the example shown in FIG. 1) of blades 9. Each stage of the blades 9 of the rotor 3 includes inclined blades that extend substantially radially from the hub 11 of the rotor 3 fixed to the shaft 12 of the turbomolecular vacuum pump 1. These blades 9 are evenly distributed around the hub 11. Each stage of the fins 10 of the stator 2 includes a crown ring, and fins that extend substantially radially and inclined from this crown ring are provided, and are evenly distributed on the inner circumference of the crown ring. Each fin of each stage of the fins 10 of the stator 2 is engaged between two consecutive stages of the blades 9 of the rotor 3. The blades of the rotor 3 and the fins of the stator 2 are inclined, guiding the gas molecules to be pumped to the molecular stage 5.

[0033] According to an exemplary embodiment, the rotor 3 includes a volute cart 13 within the molecular stage 5, and this volute cart is formed by a smooth cylinder and rotates in the spiral groove on the opposite side of the stator 2. Due to this spiral groove, the pumped gas is compressed and guided to the exhaust passage 7. The rotor 3 is fixed to the shaft 12, and this shaft 12 is rotationally driven at a high rotational speed within the stator 2. For example, it rotates at more than 20,000 revolutions per minute by the motor 16 of the turbo molecular vacuum pump 1. The motor 16 is arranged, for example, under the cover of the stator 2, and the stator 2 itself is arranged under the volute cart 13 of the rotor 3. The rotor 3 is guided in the lateral and axial directions by magnetic bearings or mechanical bearings 18. The vacuum pump 1 can also be provided with backup rolling bearings 19.

[0034] The thermal flowmeter 20 is arranged in the exhaust passage 7 within the vacuum pump 1. That is, the thermal flowmeter is arranged within the volume corresponding to the point where there is no longer gas compression between the end of the volute cart 13, which is the outlet of the rotor 3, and the outlet orifice 8, but where the pressure is the highest within the vacuum pump 1 and the risk of deposition is the highest. The thermal flowmeter 20 is arranged, for example, in the duct 14 of the exhaust passage 7, that is, generally in a pipe having the standard diameter of a vacuum coupling and having an outlet orifice 8. As in the example described above, the processing unit 22 is configured to execute measurements by the thermal flowmeter 20 and determine the presence of deposits of reaction by-products in the exhaust passage 7 of the vacuum pump 1 as a function of the difference between the flow rate measured by the thermal flowmeter 20 and the estimated value of the gas flow rate pumped by the vacuum pump 1.

[0035] As in the example described above, the estimated value of the pumped gas flow rate can be obtained only based on the information available from the vacuum pump 1. That is, there is no need to access information regarding the amount and properties of the gas introduced upstream of the vacuum pump 1. Therefore, according to an exemplary embodiment, the monitoring device 200 includes a pressure sensor 21 configured to determine the pressure in the exhaust passage 7 of the vacuum pump 1. This pressure sensor 21 is also arranged, for example, in the duct 14 of the stator 2.

[0036] The flow rate measured by the thermal flowmeter 20 and, for example, the And the estimated value of the pumped gas flow rate 、 Observed difference based on the pressure measurement and the value of the current consumption is Enable to conclude the presence of the reaction by-product deposit 27. Therefore, the monitoring device 200 enables more accurate detection of the presence of deposits in the exhaust passage 7 of the vacuum pump 1 at the earliest possible time, enabling proper management of maintenance scheduling. The monitoring can be performed in-situ, i.e., without the need to disassemble the vacuum pump 1. The measuring device is non-invasive. The measuring device does not cause pressure loss or seal loss. Since the measuring device has no moving parts, the possibility of malfunction is limited.

[0037] FIG. 6 shows a third exemplary embodiment of the present invention in which the thermal flowmeter 20 is arranged inside the roughing vacuum pump 100. As shown in FIG. 6, the roughing vacuum pump 100 includes a stator 2, and at least one pumping stage, for example, 2 to 10 pumping stages, in this example, 5 pumping stages are provided in this stator. These pumping stages are provided in series between the inlet orifice 6 and the outlet orifice 8 of the pump, and the gas to be pumped circulates through them. The pumping stage communicating with the inlet orifice 6 of the vacuum pump 100 is the first pumping stage or the lowest pressure stage, and the pumping stage communicating with the outlet orifice 8 is the final pumping stage or the highest pressure stage.

[0038] The vacuum pump 1 further includes a pair of rotors 300 that are disposed within the stator 2 and are configured to rotate synchronously in opposite directions within the pumping stage to drive the gas being pumped between the inlet orifice 6 and the outlet orifice 8. These rotors 300 have lobes of the same profile, for example, of the "Roots" type, or the "Claw" type, or having two or more than two lobes, based on the principle of another similar positive displacement vacuum pump.

[0039] During operation, the rotors 300 are rotationally driven by a motor disposed at an end of the vacuum pump 1, for example, on the side of the outlet orifice 8. During rotation, the gas sucked in from the inlet orifice 6 is trapped within the volume formed by the rotors 300 and the stator 2 of the pumping stage, compressed, and driven towards the outlet and then to the next stage. The vacuum pump 100 is a "dry" vacuum pump because during operation, the rotors 300 rotate inside the stator 2 and there is no mechanical contact between them or with the stator 2, but there is a very small clearance that allows no oil to be present in the compression chamber. In this embodiment, the exhaust passage 7 is defined by the volume included between the outlet of the rotor 300 of the final pumping stage and the outlet orifice 8, and that point is the location where there is no longer any gas compression, but the pressure is the highest and the risk of deposition is the highest. The thermal flowmeter 20 is disposed, for example, within the duct of the exhaust passage 7, that is, within a pipe having a standard diameter of a generally vacuum coupling, which connects the outlet of the rotor 300 of the final pumping stage to the outlet orifice 8.

Explanation of Reference Numerals

[0040] 1 Turbo molecular vacuum pump 2 Stator 3 Rotor 4 Turbo molecular stage 5 Molecular stage 6 Inlet orifice 7 Exhaust passage 8 Outlet orifice 9 blades 10 fins 11 hubs 12 shafts 13 Holvex carts 14 exhaust duct 16 motors 18 magnetic bearings or machines 19 rolling bearings 20 thermal flow meters 21 pressure sensors 22 processing units 23 first temperature probes 24 second temperature probes 25 heating elements 26 insulating substrates 27 deposits 100 roughing vacuum pumps 101 devices 102 process chambers 103 exhaust pipes 200 monitoring devices 300 rotors

Claims

An apparatus (200) for monitoring deposits of reaction by-products in an exhaust passage (7) of a turbo molecular vacuum pump (1), comprising: a thermal flow meter (20), a pressure sensor (21), and a processing unit (22); wherein the thermal flow meter is a MEMS component and is disposed in the exhaust passage (7); the thermal flow meter (20) includes: a first temperature probe (23) disposed at an upstream position in the gas flow direction in the exhaust passage (7), a second temperature probe (24) disposed at a downstream position, a heating element (25) interposed between the two temperature probes (23, 24), and an insulating substrate (26) that electrically and thermally insulates each of the temperature probes (23, 24) from the heating element (25); the first temperature probe, the second temperature probe, and the heating element are aligned along the exhaust passage, and measure the gas flow rate flowing through the exhaust passage based on a temperature difference; the pressure sensor (21) is configured to determine the pressure in the exhaust passage (7) of the turbo molecular vacuum pump (1); the processing unit (22) is configured to: estimate the gas flow rate pumped by the turbo molecular vacuum pump (1) based on information regarding power parameters of a motor (16) of the turbo molecular vacuum pump and measurement values of the pressure sensor (21); determine the presence of deposits of the reaction by-products in the exhaust passage (7) as a function of a difference between a measured value of the gas flow rate flowing through the exhaust passage of the turbo molecular vacuum pump (1) measured by the thermal flow meter (20) and an estimated value of the pumped gas flow rate. A monitoring apparatus characterized by the above.

2. In the monitoring apparatus (200) according to claim 1, the power parameter of the motor (16) of the turbo molecular vacuum pump (1) is current. A monitoring apparatus characterized by the above.

3. In the monitoring apparatus (200) according to claim 1, the insulating substrate encapsulates the first temperature probe and the second temperature probe to electrically and thermally insulate them from each other, and is configured to protect them from attack by gas flowing through the exhaust passage. A monitoring apparatus characterized by the above.

4. a stator (2) including an inlet orifice (6) and an outlet orifice (8); A turbo molecular vacuum pump (1) disposed within the stator (2) and comprising at least one rotor (3) configured to drive a gas pumped between the inlet orifice (6) and the outlet orifice (8). The turbo molecular vacuum pump (1) further comprises the monitoring device (200) according to claim 1, and the thermal flow meter (20) is disposed inside the turbo molecular vacuum pump. A vacuum pump characterized by this.

5. In the turbo molecular vacuum pump (1) according to claim 4, Each fin (10) of the stator (2) of the turbo molecular vacuum pump (1) is engaged between two consecutive stages of blades (9) of the rotor (3), and the rotor includes a Holweck cart (13) within the molecular stage (4). The Holweck cart is formed by a smooth cylinder, rotates in the spiral groove of the stator, and is configured such that the pumped gas is compressed and guided to the exhaust passage (7). A turbo molecular vacuum pump, characterized in that the thermal flow meter (20) and the pressure sensor (21) are disposed within a duct (14) of the exhaust passage (7).

6. A method for monitoring deposits of reaction by-products in the exhaust passage (7) of the turbo molecular vacuum pump (1) by the monitoring device (200) according to claim 1, Measuring the gas flow rate flowing through the exhaust passage by the thermal flow meter (20), and estimating the gas flow rate pumped by the turbo molecular vacuum pump (1) based on information regarding the power parameters of the motor (16) of the turbo molecular vacuum pump and the measured values of the pressure sensor (21). A method for monitoring deposits of reaction by-products, characterized by determining the presence of deposits of reaction by-products in the exhaust passage (7) as a function of the difference between the measured value of the gas flow rate flowing through the exhaust passage and the estimated value of the gas flow rate pumped by the turbo molecular vacuum pump (1).

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