Turbomolecular vacuum pump and associated cleaning method

Abstract

Turbomolecular vacuum pump (1) intended to be fluidically connected to a process chamber (101) of an equipment (100), the vacuum pump (1) comprising a control unit (30) configured to control a heating device (21) and a cooling device (22) of the vacuum pump (1) and to communicate with a control unit (104) of the equipment (100) to initiate a cleaning step (201) on command of the equipment (100), said cleaning step (201) comprising a heating phase (202) in which the control unit (30) controls the heating device to increase the internal temperature of the vacuum pump (1) during a heating duration (Tc) and a cooling phase (203) following the heating phase (202), and in which the control unit (30) controls the cooling device to lower said temperature during a cooling duration (Tr). Abstract figure: figure 1

Description

Title of the invention: Turbomolecular vacuum pump and associated cleaning method Technical field of the invention

[0001] The present invention relates to a turbomolecular vacuum pump and a method of cleaning said vacuum pump. Technical background

[0002] Generating a high vacuum in an enclosure requires the use of turbomolecular vacuum pumps composed of a stator in which a rotor is driven in rapid rotation, for example rotation at more than thirty thousand revolutions per minute.

[0003] In certain processes in which turbomolecular vacuum pumps are used, such as semiconductor, LED or photovoltaic manufacturing processes, a deposition layer may form in the vacuum pump.

[0004] It is known to heat the stator by an external heating belt to prevent condensation of reaction products in pumps. However, new generations of processes produce more and more condensable by-products. In some cases, conventional heating is no longer sufficient to prevent the formation of by-products and it is not possible to further increase the temperature of the stator without risking mechanically weakening the aluminum rotor. Deposits can then appear on the stator, the rotor being little exposed because its rotation prevents the adhesion of deposits. If no preventive maintenance is carried out, the deposit can thicken and contact can be created between the rotor and the stator, leading to an immediate crash of the pump due to the high rotation speed of the rotor and its kinetic energy.Such destruction of the vacuum pump in a semiconductor manufacturing plant can lead, in addition to the complete destruction of the pump, to the destruction of the batch of wafers being manufactured and an immobilization of the manufacturing equipment for several days. The financial losses can be considerable.

[0005] In order to limit the risks of deposits accumulating in these critical clearances, one solution may be to continuously heat the stator of the vacuum pump to temperatures above 150°C. However, it is then necessary to limit the flow of pumped gases so as not to overheat the rotor and risk lowering its mechanical strength. Thus, the increase in temperature implies limiting the maximum flow of pumped gas because the greater the flow of gas to be pumped, the more the vacuum pump heats up.

[0006] These constraints on the operating temperature and on the maximum gas flow are however contradictory with the production expectations. We are in fact seeking to increase the heating temperature as much as possible to limit the formation of deposits and thus increase the service life of the pumps. At the same time, we seek to increase the pumped gas flows as much as possible to increase production rates, and in particular heavy gas flows, such as argon, which however have the disadvantage of causing even greater heating of the rotor due to the very reduced convection heat exchanges.

[0007] Furthermore, heating the vacuum pump continuously to 150°C may, for certain processes, not be sufficient to effectively evaporate and remove all deposits. Summary of the invention

[0008] One of the aims of the present invention is to propose a turbomolecular vacuum pump which at least partially resolves a drawback of the state of the art.

[0009] For this purpose, the subject of the invention is a turbomolecular vacuum pump intended to be fluidically connected to a process chamber of an equipment, the vacuum pump comprising a stator and a rotor configured to rotate in the stator, characterized in that the vacuum pump further comprises a control unit configured to control a heating device and a cooling device of the vacuum pump and to communicate with a control unit of the equipment to initiate a cleaning step on command of the equipment, for example in the absence of introduction of gas into the process chamber or when the introduced gas flows are low, said cleaning step comprising: - a heating phase in which the control unit controls the heating device to increase the internal temperature of the vacuum pump for a heating duration, and - a cooling phase, for example following the heating phase, and in which the control unit controls the cooling device to lower said temperature during a cooling period.

[0010] The internal temperature is that of internal surfaces of the vacuum pump stator, in the gas flow path.

[0011] There may be no introduction of gas into the process chamber or introduction of low flows outside the process phases, for example during waiting phases or during maintenance phases.

[0012] Thus, particularly in the process phase, the vacuum pump can be heated to limit the formation of deposits of condensable species at moderate operating temperatures which do not overheat the vacuum pump. There is then no risk of mechanical damage to the rotor and the pumping performance is optimal. On the other hand, during the cleaning step, it is possible to significantly increase the internal temperature of the vacuum pump on the one hand, because this heating is punctual and on the other hand, because the pumped gas flow is zero or low and therefore does not contribute to heating the rotor. This increase in heating makes it possible to reach high temperatures of the internal surfaces of the vacuum pump, which allows most of the deposits to evaporate in a few minutes. The subsequent cooling by the cooling device then makes it possible to quickly lower the internal temperature within an acceptable time in production in order to shorten the period of unavailability of the process chamber.

[0013] The cooling phase may immediately follow the heating phase. According to another example, the cleaning step may include an intermediate high-temperature waiting phase, interposed between the heating phase and the cooling phase, during which the control unit cuts off the power supply to the heating device to maintain a high internal temperature for a little longer without active heating or cooling. According to yet another example, the cooling phase may begin before the end of the heating phase in order to minimize the cleaning time. The overlap time of the heating and cooling phases is for example less than 1 / 10th of the cleaning time.

[0014] The turbomolecular vacuum pump may further comprise one or more of the features described below, taken alone or in combination.

[0015] The equipment control unit may be configured to communicate to the control unit a cleaning duration allocated to the cleaning step, the control unit being configured to determine the heating duration and the cooling duration of the cleaning step, compatible with the allocated cleaning duration.

[0016] The vacuum pump may be configured to be continuously heated to a predetermined setpoint greater than 60°C and less than 100°C, such as 70°C, outside of the cleaning step.

[0017] During the heating phase of the cleaning step, the heating device can be controlled so that the internal temperature of the vacuum pump exceeds 100°C, such as 150°C, such as 200°C, or even 250°C. The evaporation temperature of the main deposits being of the order of 150°C, an increase in the internal temperature of the vacuum pump to more than 150°C makes it possible to evaporate most of the deposits.

[0018] At the end of the cooling phase of the cleaning step, the internal temperature can be returned to plus or minus 5% of the operating temperature before the heating phase or can be brought back below a temperature threshold of 100°C.

[0019] The cleaning step is for example less than forty minutes, for example between fifteen and thirty minutes.

[0020] Two successive cleaning steps may be separated from each other by at least twenty-four hours, such as at least one week, or such as at least one month.

[0021] The control unit may be configured to control a slowdown in the nominal rotation speed of the rotor during the heating phase and to control an acceleration in the rotation speed of the rotor during the cooling phase, in particular to return to the nominal rotation speed at the end of the cooling phase, for example to return to + / -5% of the nominal rotation speed. The minimum rotation speed reached at the end of the heating phase is for example less than 20% of the nominal rotation speed.

[0022] Slowing down the rotation speed during the heating phase makes it possible to prioritize the use of the electrical energy available for heating. Slowing down the rotation speed also makes it possible to limit the mechanical stress exerted on the rotor during the heating phase, i.e. during the hottest phase of the cleaning step. This reduces the risks of mechanical breakage of the rotor which could be due to an excessively high temperature.

[0023] According to an exemplary embodiment, the vacuum pump comprises a rotor temperature sensor and the control unit is configured to control the rotation speed of the rotor as a function of the temperature measured by the temperature sensor during the heating phase, in particular so that the internal mechanical stress of the rotor remains below a maximum stress associated with the measured temperature.

[0024] The heating device comprises, for example, on the one hand, an electrical circuit comprising a resistive element in thermal contact with the stator and / or a resistive element without thermal contact with the stator but capable of evacuating heat by infrared radiation, called a radiative element, the resistive or radiative element being inserted in the path of pumped gases, and on the other hand, a switch electrically connected to the electrical circuit and controllable by the control unit to authorize or cut off the electrical supply to the resistive or radiative elements.

[0025] The cooling device comprises, for example, on the one hand, a fluid circuit in thermal contact with the stator configured to be traversed by a cooling fluid and, on the other hand, a valve controllable by the control unit to authorize or cut off the circulation of the cooling fluid in the fluid circuit.

[0026] Because the stator, and in particular a stator casing, can reach high temperatures near the fluid circuit of the cooling device, it can be provided that the fluid circuit is configured to withstand a pressure greater than 1 bar (1.105 Pa), such as greater than 3 bars (3.105 Pa) in order to keep the cooling fluid in liquid form during the heating phase.

[0027] The vacuum pump may comprise a permanent cooling fluid circuit in which a cooling fluid is intended to circulate permanently, the permanent cooling fluid circuit being arranged in a base of the stator.

[0028] The cooling fluid intended to circulate in the fluid circuit and, where appropriate, in the permanent cooling fluid circuit, is for example a liquid, such as water, for example at room temperature.

[0029] The vacuum pump may comprise a thermal insulator interposed between the base and a stator casing capable of being heated by the heating device.

[0030] The controllable valve is for example a three-way valve inserted between the permanent cooling fluid circuit and the fluid circuit, the controllable valve being able to either fluidically connect the permanent cooling fluid circuit in series with the fluid circuit, or short-circuit the fluid circuit.

[0031] Alternatively, the controllable valve is a two-way valve, such as an ON / OFF valve, which can be controlled in closing to cut off the circulation of the cooling fluid or in opening to allow the circulation of the cooling fluid in the fluid circuit. In this case and if the vacuum pump comprises a permanent cooling fluid circuit, the two fluid circuits can be independent of each other or be arranged in parallel with each other, that is to say with the same inlet and the same outlet, the two-way controllable valve being arranged on the branch of the fluid circuit.

[0032] The control unit may also be configured to control a flow controller or a controllable valve of an ancillary purge device in order to inject a purge gas into the path of the pumped gases during the cleaning step.

[0033] Helical grooves may be provided in the stator opposite a Holweck skirt of the rotor.

[0034] The invention also relates to a method for cleaning a turbomolecular vacuum pump connected to a process chamber of an equipment, characterized in that a step of cleaning said vacuum pump is launched on command of the equipment, said cleaning step comprising a heating phase in which the heating device is controlled to increase the internal temperature of the vacuum pump for a heating duration and a cooling phase, for example following the heating phase, in which the cooling device is controlled to lower said temperature for a cooling duration.

[0035] The cleaning method may further comprise one or more of the features described below, taken alone or in combination.

[0036] The heating time and the cooling time of the cleaning step can be determined, compatible with an allocated cleaning time communicated by the equipment.

[0037] Apart from the cleaning step, the vacuum pump can be continuously heated to a predetermined setpoint above 60°C and below 100°C, such as 70°C.

[0038] During the heating phase, the internal temperature of the vacuum pump may exceed 100°C, such as 150°C, such as 200°C, or even 250°C.

[0039] At the end of the cooling phase, the internal temperature can be returned to plus or minus 5% of the operating temperature before the heating phase or can be brought back below a temperature threshold of 100°C.

[0040] The cleaning step is for example less than forty minutes, for example between fifteen and thirty minutes.

[0041] Two successive cleaning steps may be separated from each other by at least twenty-four hours, such as at least one week, or such as at least one month.

[0042] A slowdown of the nominal rotational speed of the rotor can be controlled during the heating phase. An acceleration of the rotational speed of the rotor can be controlled during the cooling phase. Brief description of the figures

[0043] Other advantages and characteristics will appear on reading the following description of a particular embodiment of the invention, but in no way limiting, as well as the appended drawings in which:

[0044] [Fig-1] [Fig.l] is a schematic view of manufacturing equipment connected to a turbomolecular vacuum pump, itself connected to a primary pump.

[0045] [Fig.2] [Fig.2] shows an axial sectional view of the turbocharged vacuum pump lecular of [Fig.l].

[0046] [Fig.3] [Fig.3] shows a functional diagram of elements of [Fig.l].

[0047] [Fig.4] [Fig.4] shows a graph of the internal temperature (°C) of the pump empty as a function of time.

[0048] [Fig.5] [Fig.5] is an enlarged view of a cleaning step of the graph of [Fig.4]. This figure also shows the control curves of the heating device (triangles) and the cooling device (circles) as a function of time.

[0049] In these figures, identical elements have the same reference numbers. Detailed description

[0050] The following embodiments are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment, or that the features apply only to a single embodiment. Single features of different embodiments may also be combined or interchanged to provide other embodiments.

[0051] “Upstream” means an element which is placed before another in relation to the direction of circulation of the pumped gases FL. Conversely, “downstream” means a element placed after another with respect to the direction of circulation of the pumped gases Fl.

[0052] A manufacturing plant, in particular for semiconductor elements or photovoltaic panels or flat screens, comprises manufacturing equipment 100 each comprising one or more process chambers 101 intended to receive one or more substrates 102 intended for the manufacturing of said elements.

[0053] [Fig.2] illustrates an example of a turbomolecular vacuum pump 1 intended to be fluidically connected to a process chamber 101 of such equipment 100.

[0054] The vacuum pump 1 comprises a stator 2 and a rotor 3 configured to rotate in the stator 2 at a high nominal rotation speed, for example a rotation at more than thirty thousand revolutions per minute.

[0055] The gases enter through a suction port 4 of the vacuum pump 1 and are discharged to a discharge port 5 ([Fig.l]) of the vacuum pump 1 intended to be connected for example to a primary pump 103. An annular inlet flange 6 of a casing 7 of the stator 2 surrounds for example the suction port 4 to fluidically connect the vacuum pump 1 to the process chamber 101 whose pressure is to be lowered. In operation, the gases are entrained in the direction of circulation of the pumped gases F1 going from the suction port 4 to the discharge port 5.

[0056] As best seen in [Fig.2], the rotor 3 comprises at least two stages of blades 9 and the stator 2 comprises at least one stage of fins 10. The stages of blades 9 and fins 10 follow one another axially along the axis of rotation II of the rotor 3. The rotor 3 comprises, for example, more than four stages of blades 9, such as, for example, between four and twelve stages of blades 9.

[0057] Each stage of blades 9 of the rotor 3 comprises inclined blades which extend in a substantially radial direction from a hub 11 of the rotor 3 fixed to a drive shaft 12 of the vacuum pump 1, for example by screwing. The blades are distributed regularly around the periphery of the hub 11.

[0058] Each stage of fins 10 of the stator 2 comprises a crown secured to the casing 7 and from which extend, in a substantially radial direction, inclined fins, distributed regularly around the inner periphery of the crown. The fins of a stage of fins 10 of the stator 2 engage between the blades of two successive stages of blades 9 of the rotor 3. The blades 9 of the rotor 3 and the fins 10 of the stator 2 are inclined to guide the pumped gas molecules in the direction of circulation of the pumped gases FL

[0059] The rotor 3 is configured to be driven in rotation in the stator 2 by an internal motor 17 of the vacuum pump 1. The motor 17 is for example arranged in a bell 18 of the stator 2, itself arranged under an internal bowl 19 of the rotor 3, the drive shaft 12 of the rotor 3 passing through the bell 18 of the stator 2.

[0060] The rotor 3 is guided laterally and axially by magnetic bearings 20 or mechanical bearings supporting the drive shaft 12 of the rotor 3, located in the stator 2.

[0061] According to an exemplary embodiment, helical grooves 14 are provided in the stator 2, in a part of the stator 2 called the Holweck stator or high-pressure stator 8, opposite a Holweck skirt 13 of the rotor 3, in a Holweck (or molecular) stage 16, downstream of the turbomolecular pumping stage 15.

[0062] The helical grooves 14 are arranged one above the other. There are for example between three and ten helical grooves 14, such as six. The high-pressure stator 8 is received in the casing 7 of the stator 2, the casing 7 connecting the outlet of the high-pressure stator 8 with the discharge orifice 5. The high-pressure stator 8 is intended to increase the compression ratio of the vacuum pump 1 for so-called intermediate pressures. The helical grooves 14 make it possible to compress and guide the pumped gases towards the discharge orifice 5.

[0063] In operation, the gases enter through the suction port 4 of the vacuum pump 1, first pass through the turbomolecular stage 15, then the Holweck stage 16, and are discharged towards the discharge port 5.

[0064] The vacuum pump 1 further comprises a heating device 21 for the stator 2, a cooling device 22 for the stator 2 and a control unit 30 configured to control the heating device 21 and the cooling device 22 ([Fig.3]).

[0065] The heating device 21 comprises, for example, on the one hand, an electrical circuit 29 comprising a resistive element 23 in thermal contact with the stator 2 and / or a resistive element without thermal contact with the stator 2 but capable of evacuating heat by infrared radiation, called a radiative element, the resistive or radiative element being inserted in the path of pumped gases and, on the other hand, a switch 28 electrically connected to the electrical circuit 29 and controllable by the control unit 30 to authorize or cut off the electrical supply to the resistive 23 or radiative elements (figures 2 and 3).

[0066] The resistive element 23 is for example an internal heating belt, in thermal contact with the high pressure stator 8, for example arranged on the external periphery of the high pressure stator 8, interposed between the high pressure stator 8 and the casing 7 of the stator 2 ([Fig.2]). A sealed passage 31 makes it possible for example to electrically connect conductors of the vacuum electrical circuit 29 to an external cable connected to the control unit 30.

[0067] The cooling device 22 comprises, for example, on the one hand, a fluid circuit 24 in thermal contact with the stator 2 configured to be traversed by a cooling fluid and, on the other hand, a valve 25 controllable by the control unit 30 to authorize or cut off the circulation of the cooling fluid in the fluid circuit 24 ([Fig. 2] and 3).

[0068] The fluid circuit 24 is for example arranged in the casing 7 of the stator 2. It surrounds for example the first stages of fins 10 in the turbomolecular stage 15 and / or the high pressure stator 8 in the Holweck stage 16.

[0069] The stator 2, and in particular here the casing 7, is therefore capable of being heated by the heating device 21 and capable of being cooled by the cooling device 22.

[0070] The vacuum pump 1 may also comprise a permanent cooling fluid circuit 26 in which the cooling fluid is intended to circulate permanently (figures 2 and 3).

[0071] The permanent cooling fluid circuit 26 is for example arranged in a base 27 of the stator 2, under the casing 7. It surrounds for example the bell 18 projecting from the base 27 to cool the elements that it contains such as in particular the bearings 20 and the motor 17 and extends into the base 27 to cool other electrical or electronic components contained in the base 27 in order to allow their operation.

[0072] The cooling fluid intended to circulate in the fluid circuit 24 and, where appropriate, in the permanent cooling fluid circuit 26, is for example a liquid, such as water, for example at room temperature.

[0073] According to an exemplary embodiment, provision is made to thermally insulate the casing 7 of the stator 2 capable of being heated by the heating device 21, from the base 27 of the stator 2 in which the permanent cooling fluid circuit 26 is arranged. For this, the vacuum pump 1 comprises a thermal insulator 32 interposed between the casing 7 and the base 27. The thermal insulator 32 is for example made of stainless steel or fiberglass.

[0074] The vacuum pump 1 may further comprise a permanent purge injection device (not shown) configured to be connected to a source of purge gas in order to introduce a purge gas into a cavity of the stator 2 receiving one end of the shaft 12 rotating the rotor 3. The injected gas rises along the shaft 12 passing through the bearings 20, the motor 17 and leaves the bell 18 of the stator 2 to circulate between the bell 18 and the internal bowl 19 to the discharge orifice 5. The flow of purge gas makes it possible to cool the motor 17 and makes it possible to sweep the pivoting elements of the turbomolecular vacuum pump 1, in particular the bearings 20, the electrical connections and the welds. The sweeping of these elements by the purge gas makes it possible to protect them from potentially aggressive pumped gases. The purge gas is preferably air or nitrogen, but can also be another neutral gas such as helium or argon.

[0075] The control unit 30, such as an electronic card, comprises one or more controllers or microcontrollers or processors and a memory, for executing sequences of program instructions making it possible to implement a method of cleaning 200 of the turbomolecular vacuum pump 1. The control unit 30 is for example arranged in the base 27 of the stator 2 cooled by the permanent cooling fluid circuit 26.

[0076] The control unit 30 is configured to communicate with a control unit 104 of the equipment 100 to launch a cleaning step 201 on command from the control unit 104, for example in the absence of introduction of gas into the process chamber 101 or when the introduced gas flows are low.

[0077] The control unit 104 comprises one or more controllers or microcontrollers or processors having for example knowledge or control of the state of the process chamber 101, in particular if the latter is in process phase 104 for which manufacturing processes using process gases take place in the process chamber 101 or in maintenance phase in particular of the equipment 100 or of the process chamber 101 or in waiting phase (“stand-by” or “idle” in English) for example between two process phases 204 or other.

[0078] There may be no introduction of gas into the process chamber 101 or introduction of weak flows outside the process phases 204, for example during waiting phases or during maintenance phases ([Fig.4]).

[0079] The cleaning step 201 controlled by the control unit 104 of the equipment 100 comprises a heating phase 202 in which the control unit 30 controls the heating device 21 to increase the internal temperature of the vacuum pump 1 for a heating duration Te and a cooling phase 203, for example following the heating phase 202, and in which the control unit 30 controls the cooling device 22 to lower said temperature for a cooling duration Tr ([Fig.5]).

[0080] This internal temperature is that of the internal surfaces of the stator 2 of the vacuum pump 1, in the gas flow path, in the turbomolecular stage 15 and / or in the Holweck stage 16.

[0081] Outside of the cleaning steps 201, in particular during the process phases 204 where process gases are introduced into the process chamber 101, the internal temperature of the vacuum pump 1 can be continuously heated to a predetermined setpoint greater than 60°C and less than 100°C, such as for example 70°C, i.e. to a lower temperature than during the cleaning steps 201.

[0082] For this, according to a first example, the control unit 30 actively controls the heating device 21 by controlling the electrical power supply of the resistive or radiative elements of the heating device 21, for example as a function of signals from a temperature sensor of the stator 2.

[0083] A curve A (triangles) is shown in [Fig.5] for illustrative purposes, the moments when the control unit 30 starts the electrical supply to the elements resistive or radiative of the heating device 21 during the process phases 204. The continuous heating temperature below 100°C is acceptable by the vacuum pump 1 without risks for the rotor 3 and this whatever the pumped gas flows, therefore without loss of performance.

[0084] According to another exemplary embodiment, the turbomolecular vacuum pump 1 comprises an additional heating device for the stator 2, such as a heating resistive belt, the electrical supply of which is controlled by the control unit 30 to control the internal temperature around the predetermined setpoint in continuous heating.

[0085] When the control unit 104 of the equipment 100 launches a cleaning step 201, the heating device 21 can be controlled during the heating phase 202 so that the internal temperature exceeds 100°C, such as 150°C, such as 200°C, or even 250°C. This temperature is for example greater than twice the internal temperature in continuous heating of the process phases 204.

[0086] For this, the control unit 30 controls for example the continuous electrical supply of the resistive or radiative elements, for example at more than 400W for a few minutes (curve A (triangles) in [Fig.4]), by closing the switch 28 of the electrical supply circuit 29 ([Fig.3]), which makes it possible to increase the internal temperature of the vacuum pump to more than 100°C, such as more than 150°C, up to more than 200°C, or even 250°C.

[0087] The evaporation temperature of the main deposits being of the order of 150°C, an increase in the internal temperature of the vacuum pump 1 to more than 150°C makes it possible to evaporate most of the deposits.

[0088] Since, during the heating phase 202 of the cleaning step 201, the electrical supply power available for the vacuum pump 1 is used by the heating device 21 and by the motor 17 of the vacuum pump 1, and since the electrical power consumed during the heating phase 202 can be relatively large, it may be necessary for the motor 17 of the vacuum pump 1 not to be overloaded, i.e. for the flow of pumped gas to be limited.

[0089] Similarly, it may be useful to order a slowdown in the nominal rotation speed of the rotor 3 during the heating phase 202 and to order an acceleration in the rotation speed of the rotor 3 during the cooling phase 203, in particular to return to the nominal rotation speed at the end of the cooling phase, for example to return to + / -5% of the nominal rotation speed. The minimum rotation speed reached at the end of the heating duration Te is for example less than 20% of the nominal rotation speed.

[0090] The slowing down of the rotation speed during the heating phase 202 thus makes it possible to prioritize the use of the electrical energy available for heating. The slowing down of the rotation speed also makes it possible to limit the constraint mechanical force exerted on the rotor 3 during the heating phase 202, that is to say during the hottest phase of the cleaning step 201. This reduces the risks of mechanical breakage of the rotor 3 which could be due to an excessively high temperature.

[0091] According to an exemplary embodiment, the vacuum pump 1 comprises a temperature sensor for the rotor 3 and the control unit 30 is configured to control the rotation speed of the rotor 3 as a function of the temperature measured by the temperature sensor during the heating phase 202, in particular so that the internal mechanical stress of the rotor 3 remains below a maximum stress associated with the measured temperature.

[0092] The cleaning step 201 may include an intermediate high-temperature waiting phase, interposed between the heating phase 202 and the cooling phase 203, during which the control unit 30 cuts the electrical power supply to the heating device 21 to maintain a high internal temperature for a little longer without active heating or cooling, for example and as will be seen later if the allocated cleaning time is sufficiently long.

[0093] Alternatively, the cooling phase 203 may follow the heating phase 202.

[0094] According to yet another example, the cooling phase 203 may begin a little before the end of the heating phase 202 in order to minimize the cleaning time.

[0095] This latter alternative is particularly advantageous if the resistive or radiative elements of the heating device 21 are distant from the fluid circuit 24 of the cooling device 22, for example if the resistive or radiative elements are located on the inside of the high-pressure stator 8 in the circulation path of the pumped gases while the fluid circuit 24 surrounds the outside of the high-pressure stator 8, for example by being arranged in the casing 7. It is then possible to have a temperature difference between the inside and the outside of the high-pressure stator 8. The cooling of the outside of the high-pressure stator 8 can thus begin before the inside has reached its maximum temperature.

[0096] The duration of overlap of the heating 202 and cooling 203 phases remains however short, for example less than 1 / 10th of the cleaning duration.

[0097] Then, during the cooling phase 203, the control unit 30 actively controls the cooling of the internal temperature via the cooling device 22.

[0098] For this, the control unit 30 can cut off the electrical power supply to the heating device 21 and control, for example, the controllable valve 25 of the cooling device 22 so as to circulate a cooling fluid in the fluid circuit 24.

[0099] The controllable valve 25 is for example controlled so that the cooling fluid dissement circulates only in the fluid circuit 24 during the cooling phases 203 of the cleaning steps 201.

[0100] According to an exemplary embodiment, the controllable valve 25 is a three-way valve inserted between the permanent cooling fluid circuit 26 and the fluid circuit 24, the controllable valve 25 being able to either fluidically connect the permanent cooling fluid circuit 26 in series with the fluid circuit 24, or to short-circuit it ([Fig.3]). This ensures control of the flow rate in the permanent cooling fluid circuit 26 and in the fluid circuit 24 in the cooling phase 203. A curve B (circles) is shown in [Fig.5] for illustrative purposes, the moments when the control unit 30 controls the series connection of the fluid circuit 24 with the permanent cooling fluid circuit 26.

[0101] Alternatively, the controllable valve 25 is a two-way valve, such as an ON / OFF valve, which can be controlled in closing to cut off the circulation of the cooling fluid or in opening to allow the circulation of the cooling fluid in the fluid circuit 24. In this case and if the vacuum pump 1 comprises a permanent cooling fluid circuit 26, the two fluid circuits can be independent of each other or be arranged in parallel with each other, that is to say with the same inlet and the same outlet, the two-way controllable valve 25 being arranged on the branch of the fluid circuit 24.

[0102] It can be provided that at the end of the cooling phase 203, the internal temperature falls below a temperature threshold of 100°C or returns to more or less 5% of the operating temperature before the heating phase 202.

[0103] The cleaning step 201 is advantageously less than forty minutes, for example between fifteen and thirty minutes.

[0104] The heating 21 and cooling 22 devices may be configured so that the heating duration Te is equal, plus or minus 20%, to the cooling duration Tr. For example, the heating duration Te and the cooling duration Tr last ten minutes each.

[0105] Furthermore, two successive cleaning steps 201 are for example separated from each other by at least twenty-four hours, such as at least one week, or such as at least one month.

[0106] The cleaning time is therefore relatively short and the cleaning steps 201 relatively infrequent so that the process chamber 101 is not unavailable for long.

[0107] According to an exemplary embodiment, the control unit 104 of the equipment 100 is configured to communicate to the control unit 30 a cleaning duration allocated to the cleaning step 201, for example due to the absence of process gas in the process chamber 101. In other words, in addition to controlling the triggering of a cleaning step 201, the control unit 104 communicates when this cleaning step 201 must be completed, for example because a process step 204 will resume in the process chamber 101 ([Fig.4]).

[0108] The control unit 30 can then determine the heating duration Te and the cooling duration Tr of the cleaning step 201, compatible with the allocated cleaning duration.

[0109] In particular, the control unit 30 can determine the heating Te and cooling Tr durations allowing that at the end of the cooling phase 203, the internal temperature of the vacuum pump 1 is less than 100°C or returns to more or less 5% of the operating temperature before the heating phase 202.

[0110] Because the stator 2 can reach high temperatures near the fluid circuit 24 of the cooling device 22, it can be provided that the latter is configured to withstand a pressure greater than 1 bar (1.105 Pa), such as greater than 3 bars (3.105 Pa) allowing the cooling liquid to be kept in the liquid phase during the heating phase 202.

[0111] Furthermore, the control unit 30 can be configured to control a flow controller or a controllable valve of an additional purge device in order to inject a purge gas into the path of the pumped gases during the cleaning step 201, in particular during the cooling phase 203 to facilitate the evacuation of the vaporized deposits (not shown). The purge gas is preferably air or nitrogen, but can also be another neutral gas such as helium or argon. It is for example injected upstream of the suction orifice 4 of the vacuum pump 1, between the process chamber 101 and the vacuum pump 1.

[0112] Thus, in particular in process phase 204, the vacuum pump 1 can be heated to limit the formation of deposits of condensable species at moderate operating temperatures which do not overheat the vacuum pump 1. There is then no risk of mechanical damage to the rotor 3 and the pumping performance is optimal. On the other hand, during the cleaning step 201, it is possible to very significantly increase the internal temperature of the vacuum pump 1 on the one hand, because this heating is punctual and on the other hand, because the flow of pumped gas is zero or low and therefore does not participate in heating the rotor 3. This increase in heating makes it possible to reach high temperatures of the internal surfaces of the vacuum pump 1, which makes it possible to evaporate most of the deposits in a few minutes.The successive cooling by the cooling device 22 then makes it possible to quickly lower the internal temperature within an acceptable time frame in production in order to shorten the period of unavailability of the process chamber 101.

Claims

Claims

1. Turbomolecular vacuum pump (1) intended to be fluidically connected to a process chamber (101) of an equipment (100), the vacuum pump (1) comprising a stator (2) and a rotor (3) configured to rotate in the stator (2) characterized in that the vacuum pump (1) further comprises a control unit (30) configured to control a heating device (21) and a cooling device (22) of the vacuum pump (1) and to communicate with a control unit (104) of the equipment (100) to initiate a cleaning step (201) on command of the equipment (100), said cleaning step (201) comprising: - a heating phase (202) in which the control unit (30) controls the heating device to increase the internal temperature of the vacuum pump (1) for a heating duration (Te), and - a cooling phase (203),wherein the control unit (30) controls the cooling device to lower said temperature during a cooling time (Tr), the control unit (104) of the equipment (100) being configured to communicate to the control unit (30) a cleaning time allocated to the cleaning step (201), the control unit (30) being configured to determine the heating time (Te) and the cooling time (Tr) of the cleaning step (201), compatible with the allocated cleaning time so that at the end of the cooling phase (203) of the cleaning step (201), the internal temperature has returned to plus or minus 5% of the operating temperature before the heating phase (202) or has fallen below a temperature threshold of 100°C.,

2. Vacuum pump (1) according to one of the preceding claims, characterized in that it is configured to be continuously heated to a predetermined setpoint greater than 60°C and less than 100°C, such as for example 70°C, outside the cleaning step (201).

3. Vacuum pump (1) according to one of the preceding claims, characterized in that during the heating phase (202) of the cleaning step (201), the heating device (21) is controlled so that the internal temperature of the vacuum pump (1) exceeds 100°C, such as 150°C, such as 200°C, or even 250°C.

4. Vacuum pump (1) according to one of the preceding claims, characterized in that the control unit (30) is configured to to control a slowdown of the nominal rotation speed of the rotor (3) during the heating phase (202) and to control an acceleration of the rotation speed of the rotor (3) during the cooling phase (203).

5. Vacuum pump (1) according to one of the preceding claims, characterized in that the heating device (21) comprises on the one hand, an electrical circuit (29) comprising a resistive element (23) and / or a radiative element, inserted in the path of pumped gases and on the other hand, a switch (28) electrically connected to the electrical circuit (29) and controllable by the control unit (30) to authorize or cut off the electrical supply to the resistive (23) or radiative elements.

6. Vacuum pump (1) according to one of the preceding claims, characterized in that the cooling device (22) comprises on the one hand, a fluid circuit (24) in thermal contact with the stator (2) configured to be traversed by a cooling fluid and on the other hand, a valve (25) controllable by the control unit (30) to authorize or cut off the circulation of the cooling fluid in the fluid circuit (24).

7. Vacuum pump (1) according to one of the preceding claims, characterized in that it comprises a permanent cooling fluid circuit (26) in which a cooling fluid is intended to circulate permanently, the permanent cooling fluid circuit (26) being arranged in a base (27) of the stator (2).

8. Vacuum pump (1) according to the preceding claim, characterized in that it comprises a thermal insulator (32) interposed between the base (27) and a casing (7) of the stator (2) capable of being heated by the heating device (21).

9. Vacuum pump (1) according to claim 6 and according to one of claims 7 or 8, characterized in that the controllable valve (25) is a three-way valve interposed between the permanent cooling fluid circuit (26) and the fluid circuit (24), the controllable valve (25) being able either to fluidically connect the permanent cooling fluid circuit (26) in series with the fluid circuit (24), or to short-circuit the fluid circuit (24).

10. Vacuum pump (1) according to one of the preceding claims, characterized in that the control unit (30) is configured to control a flow controller or a controllable valve of an ancillary purge device in order to inject a purge gas into the gas path. pumped during the cleaning step (201).

11. Vacuum pump (1) according to one of the preceding claims, characterized in that helical grooves (14) are provided in the stator (2) opposite a Holweck skirt (13) of the rotor (3).

12. A method of cleaning (200) a turbomolecular vacuum pump (1) connected to a process chamber (101) of an equipment (100), characterized in that a cleaning step (201) of said vacuum pump (1) is launched on command of the equipment (100), said cleaning step (201) comprising a heating phase (202) in which the heating device (21) is controlled to increase the internal temperature of the vacuum pump (1) for a heating duration (Te) and a cooling phase (203), in which the cooling device (22) is controlled to lower said temperature for a cooling duration (Tr), the heating duration (Te) and the cooling duration (Tr) of the cleaning step (201) are determined, compatible with an allocated cleaning duration communicated by the equipment (100) so that at the end of the cooling phase (203) of the cleaning step (201),the internal temperature has returned to plus or minus 5% of the operating temperature before the heating phase (202) or has fallen below a temperature threshold of 100°C.,

13. Cleaning method (200) according to the preceding claim, characterized in that, apart from the cleaning step (201), the vacuum pump (1) is continuously heated to a predetermined setpoint greater than 60°C and less than 100°C, such as for example 70°C.

14. Cleaning method (200) according to one of claims 12 or 13, characterized in that during the heating phase (202) of the cleaning step (201), the vacuum pump (1) is heated to exceed 100°C, such as 150°C, such as 200°C, or even 250°C.

15. Cleaning method according to one of claims 12 to 14, characterized in that a slowdown of the nominal rotation speed of the rotor (3) is controlled during the heating phase (202) and an acceleration of the rotation speed of the rotor (3) during the cooling phase (203).

16. Cleaning method according to one of claims 12 to 15, characterized in that the cleaning step (201) is less than forty minutes, for example between fifteen and thirty minutes.

17. Cleaning method according to one of claims 12 to 16, characterized in that two successive cleaning steps (201) are separated from each other by at least twenty-four hours, such as at least one week, or such as at least one month.

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