EP2644900B1 - Pump system for evacuating of gas from a plurality of chambers and method for controlling the pump system - Google Patents

Description

The invention relates to a pump system for evacuating gas from a plurality of chambers and a method for controlling the pump system.

An overall system consists in practice of one or more vacuum chambers (recipient). These chambers can be used individually, but also at least partially be connected to each other. In this case, if there is a pressure difference between two chambers, the conductance of an opening in the common wall between two process chambers or the conductance of the connecting pipeline significantly determines the gas flow between them. One or more chambers can continue to be exposed to gas loads, these can both by connections to the outside of the chamber ("atmosphere"), by an on-handed gas load from an upstream chamber, by otherwise generated, usually process-related gas streams, also by the admission of inert or process gases which are usually noble gases such as helium, caused by desorption of introduced into the chamber workpieces, specimens and / or the chamber components and / or by active in the process resulting reaction products.

In order to maintain the process within each chamber, they must be evacuated by vacuum pumping systems connected to an intended vacuum pressure and the pressure then kept as constant as possible. These individual vacuum pump systems each consist either of a single pump or of a series and / or parallel connection of several pumps. Depending on the amount of gas accumulating several chambers can be evacuated by individual pumps simultaneously or even several pumps are evacuated by a common backing pump. Between the chambers and pumps, both series, parallel circuits or any combinations thereof can be designed as compounds.

From the prior art ( WO 2011/121322 A2 It is well known that pumps can suitably assist each other by connecting them at different pressure levels within another pump.

Most processes in multi-chamber systems require a high gas load at low pressure, so large backpumps must be used to maintain the desired vacuum pressure. Low pressure means that there should be high pumping speed. At the same time, other chambers of such a system can be kept at very low cost vacuum pressure and a small pump is sufficient. The more gas load a pump has to cope with, the higher is its energy requirement and the associated cooling demand due to gas friction and electrical and mechanical losses.

Due to the given environmental and boundary conditions, for example, limited space, allowed heat output, noise or vibration development, it may be advantageous to use several small pumps instead of a large one. Furthermore, it is advantageous to distribute the loads as evenly as possible in order to ensure a higher efficiency of the pumps.

For real applications, the gas loads and vacuum pressures from chamber to chamber are very different and an adaptation according to the above options is difficult while maintaining the desired process data and only possible with weighing of interests. One type of solution describes the prior art ( WO 2011/121322 A2 ), but this requires special pumps with appropriately selected intermediate connections.

The prior art ( JP 2010-167338 A ) includes a pump system, in which turbopumps and the turbopump upstream pre-pumps are provided. This to the stand The technology belonging system can be further improved in terms of cost.

Furthermore belongs to the state of the art ( US 4,919,599 A ) a pump system in which also several backing pumps and several turbomolecular pumps are provided. Also, this pump system can be further improved in terms of cost.

The prior art ( US 2010/0206407 A1 ) also includes a lock system for a vacuum system in which also fine vacuum pumps and backing pumps are provided. With the large number of pumps used in this pump system, a further improvement can also be achieved in terms of economy.

The technical problem underlying the invention is to make optimum use of as many pumps as possible from an economic and technical point of view, and to obtain gas loads as evenly as possible without repercussions distributed to the process on a plurality of as simple as possible and similar or the same pump.

This technical problem is solved by a pump system having the features according to claim 1 and by a method having the features according to claim 9.

The pump system according to the invention for evacuating gas from a plurality of chambers with at least four vacuum pumps, wherein at least two backing pumps and at least two turbomolecular pumps are provided, wherein the chambers are interconnected and have a different vacuum pressure, wherein a first chamber is associated with a first turbomolecular pump and a second turbomolecular pump is associated with a second chamber, wherein the first turbomolecular pump is supported by a first backing pump and the second turbomolecular pump is supported by a second forepumping and wherein at least one cross-sectional constriction is provided for controlling a gas flow in at least one connecting line between the at least two forepumps , is characterized by the fact that all turbomolecular pumps are of identical design, and that at least one point in the at least one chamber and / or in the at least one wiring harness and / or r is provided at the provided connections of the pump, a device for measuring the current vacuum pressure or the gas flow.

According to the invention, between parallel-connected pumps, the maximum gas flow in the respective wiring harness is limited by one or more cross-sectional constrictions. Under cross-sectional constriction in the sense of Invention is also understood to mean a device for completely closing a wire strand.

By the invention it is possible to avoid not only greatly different sizes of pumps, but as possible to use two or more identical pumps at different positions in order to keep the number of variants in production, sales, installation and application low and thus for manufacturers and customers to realize a cost saving. This cost saving is achieved, inter alia, that the training effort is low. Qualification expenditure means that the user uses several pumps of the same design and tries out which pumps in combination best solve the required task in the country-specific voltage network or at the country-specific network frequency. This tactic can be used both for pumps in the fore-vacuum range as in the example above, and for pumps that are connected to the chamber directly or via a connecting line.

A cross-sectional constriction can be advantageously carried out as a simple aperture. This represents a component which has a defined cross-sectional constriction over a certain length of the existing strand.

An orifice is in the simplest case provided with a fixed constriction.

Another particularly advantageous embodiment is adjustable within a defined range. This embodiment is called a throttle valve. The adjustment The range can be done either mechanically by hand or electrically, pneumatically or hydraulically via the control drive.

The adjustment of the throttle valve is advantageously based on a previously determined, calibrated scale, but offers no feedback on the actual cross section or gas flow. For this purpose, advantageously, a gas flow measurement can be done either separately or integrated, so that the execution is possible as a closed loop to be able to control a given gas flow. Usually corresponding default values are electrically generated as an analog signal, for example as voltage, current, pulse width modulation or other conventional methods or transmitted as a digital signal via any bus system. Alternatively or additionally, a specification can also be generated via a locally or remotely connected operator panel with a user interface. This device is commonly referred to as a gas flow regulator. The gas flow controller is a commercially available component, which is also referred to as "Mass Flow Controller".

The mentioned cross-sectional constrictions can be carried out in a suitable manner individually or as a combination of identical or different embodiments in parallel and / or in series. The use of one or more valves for separating one or more sub-strands of the constructed network additionally expands the possibilities for adaptation to individual process states.

According to the invention, it is possible, at one or more locations both at one or more chambers and / or at any points within the cable strands or at
provided for the terminals of the pumps to measure the current vacuum pressure and / or the gas flow and to use to control the aforementioned means. The simplest embodiment describes a pressure switch, which gives a signal for opening or closing a sub-string at a predetermined limit pressure in order to avoid overloading a connected pump or influencing the process specifications.

A further advantageous embodiment of the invention provides a higher-level process control. With higher-level process control, it is possible to use the acquired measured values from different locations for process evaluation and influencing, thus optimizing the optimization of the process and the load on the individual pumps.

When using pumps whose pumping capacity is at least partially dependent on their discharge pressure, for example molecular pumps, it is advantageous if they have on their discharge side at least one pumping stage, which deliver constant pumping powers over a large pressure range. These may be Gaede, Siegbahn and / or Holweck levels, for example. The robustness of the pump to pressure fluctuations on the discharge side allows a significant simplification of the further design of the system. This can be worked with a simple throttle instead of a switched or regulated valve.

The solution described leads to advantages in systems, for example so-called LCMS systems, in which one of the low load pumps must pump mainly light gases (low particle masses) in at least one process state, such as helium in the "additional gasload" is initiated as a process gas. The performance of most pumping principles depends on the atomic or molecular weights to be pumped, while light gases with low masses are usually more difficult to pump. The pumping power of such pumps increases greatly when heavier gases are used as trailing medium. In this case, the heavy particles entrain the light in the right direction through the pump, thus reducing the backflow of the light gases. Although the pump has to pump more gas in total, the pumping power for light gases increases significantly. The discharge of the first pump, which delivers via a cross-sectional constriction gas flow with a lower proportion of light gases to the second pump, leading in the case of the second pump, which in the case described a high proportion light gases pumping, to a corresponding drag effect, so that light gases can be pumped much better.

Pumps that are often operated with frequency inverters directly on the local power supply network, depending on the country-specific grid frequency (typically 50 Hz or 60 Hz) or grid voltage (typically 90V, 110V, 230V) rotate at different speeds and / or with different maximum drive power (for example Limitation of the drive current or the resulting heat input) and thus also change according to their maximum pump power. As a result, chambers evacuated directly from such a pump are pumped to a different pressure level, depending on the power supply network. In order to avoid this, it has hitherto been necessary according to the usual practice to regulate the gas flows by adapting control valves or orifices within or at the chamber so that the desired process pressure is achieved in the existing or predetermined power supply network. Depending on the complexity of the overall system, this is not easy to implement and involves a great deal of effort, since usually several corresponding chambers are affected. The problem can be solved by the inventive installation of at least one cross-sectional constriction at least between the affected first variable speed pump and / or variable drive power and a second pump, which either pumps off an area in which the chamber pressure is irrelevant and / or for at least one directly the pump connected to the chamber, for example one or more molecular pumps (n) generates the admission pressure, which reacts robustly to pressure changes on its discharge side. The simple change or adjustment of said cross-sectional constriction compensates for the difference in pumping capacity of the first pump so that the affected chamber pressure remains constant without intervention in or on the chamber. Such an adjustment can, as already described, also be carried out with an internally or externally connected control unit which determines the process state, for example the vacuum pressure of the chamber concerned and adjusts the cross-sectional constriction to a desired value in the current process state.

A control can also eliminate the problem that the variable pumping power is not due to influences of the power supply network, but due to differences in the operating state of the pump, so it shows different pump powers in warm operating condition or changed environmental conditions, especially ambient and / or cooling water temperature. The pump system according to the invention has two or more chambers, which are at least partially interconnected and which are operated with mostly different vacuum pressures. Gas streams are generated by the admission of gases to be analyzed and often by the admission of further auxiliary gases into other chambers. Optionally, at least one of the additional vacuum pumps may have more than one pump inlet ("split flow", interstage port) connected to at least one other chamber than that at the first inlet of the pump. Advantageously, the Pumps have a high robustness against high discharge pressures, typical is the pressure between molecular and forepump in a range of 1 to 20 mbar (millibars). In order to relieve at least one of the at least two backing pumps, at least one connection is realized with a cross-sectional constriction between the suction connections of the first-mentioned and a second pre-pump, which allows maximally so much gas flow, so that the second pre-pump can always hold at least a certain suction pressure. The first, relieved pre-pump can be chosen smaller, the second is better utilized.

Fig. 1

ein Pumpensystem gemäß dem Stand der Technik;

Fig. 2

ein erstes Ausführungsbeispiel in schematischer Darstellung;

Fig. 3

ein zur Erfindung nicht gehörendes Beispiel in schematischer Darstellung;

Fig. 4

ein geändertes Ausführungsbeispiel in schematischer Darstellung;

Fig. 5

ein geändertes Ausführungsbeispiel in schematischer Darstellung;

Fig. 6

ein geändertes Ausführungsbeispiel in schematischer Darstellung.

Further features and advantages of the invention will become apparent from the accompanying drawings, in which several embodiments of a pump system according to the invention are shown by way of example only. In the drawing show:

Fig. 1

a pump system according to the prior art;

Fig. 2

a first embodiment in a schematic representation;

Fig. 3

an example not belonging to the invention in a schematic representation;

Fig. 4

a modified embodiment in a schematic representation;

Fig. 5

a modified embodiment in a schematic representation;

Fig. 6

a modified embodiment in a schematic representation.

Fig. 1 shows a belonging to the prior art pump system with two chambers to be evacuated 1, 2. The chamber 1 is associated with a turbomolecular pump 3 and the chamber 2 is a turbomolecular pump 4th

The turbomolecular pump 3 is supported by a backing pump 5. The turbomolecular pump 4 is supported by a backing pump 6.

This belonging to the prior art pump system has the disadvantage that the turbomolecular pump 3 must maintain the predetermined pressure in the chamber 1 and the turbomolecular pump 4, the predetermined pressure in the chamber 2. The pumps 3, 4, 5, 6 must be qualified accordingly. This means that they have to provide the required pump power under the country-specific conditions of the voltage network and the mains frequency.

Q is the gas flow. The chambers 1, 2 are interconnected. At different pressures in the chambers 1, 2, a gas flow Q takes place between the chambers. In the chamber 2, moreover, a gas inlet 7 is provided to supply a process gas to the chamber 2.

Fig. 2 shows the chambers 1, 2, which are evacuated by the turbomolecular pumps 3, 4.

The backing pumps 5, 6 in this case support the turbomolecular pumps 3, 4.

Between the backing pumps 5, 6, a wiring harness 8 is provided. In the wiring harness 8 is shown schematically, a diaphragm 9 is arranged. With this panel 9, the gas flow in the wiring harness 8 can be regulated.

By means of this arrangement according to the invention, it is possible to dimension the pumps 3, 4 equal or to use turbomolecular pumps 3, 4 of the same type. There is also a discharge of the first pump 5, which emits a gas stream with a smaller proportion of light gases to the second pump 6 via the aperture 9. This leads to the second pump 6, which according to Fig. 2 Pumping a high proportion of light gases, resulting in a corresponding drag effect, so that light gases can be pumped much better.

Between the backing pumps 5, 6, in turn, a wiring harness 8 is provided, which is provided with a diaphragm 9.

Fig. 3 shows an example not belonging to the invention with three chambers 1, 2, 10. According to Fig. 3 Again, the two backing pumps 5, 6 are provided and the turbomolecular pump 3 for evacuating the chamber 1. For evacuation of the chambers 2, 10, a split-flow pump 11 is provided which has two inlets 12, 13. Between the backing pumps 5, 6 turn the wiring harness 8 is provided, in which the aperture 9 is arranged.

Fig. 4 shows a further embodiment with the chambers to be evacuated 1, 2, 10, 13, 14, 15. The chambers 2, 10, 13 have additional gas inlets 16, 17, 18 for process gases.

For the evacuation of the chamber 1, the turbomolecular pump 3 is provided, which is supported by the backing pump 5. For evacuation of the chambers 2, 13 and 14, a split flow pump 19 is provided, which is supported by the backing pump 6.

For evacuation of the chamber 15, an additional turbomolecular pump 20 is provided.

Between the backing pumps 5, 6, in turn, a wiring harness 8 is provided, in which a diaphragm 9 is arranged. Again, a relief of the first pump 5 is provided, which emits gas flow over the cross-sectional constriction 9 with a small proportion of light gases to the second pump 6. This results in the second pump 6, which in the present case pumps a high proportion of light gases, to a corresponding drag effect, so that light gases can be pumped much better.

Fig. 5 shows an arrangement with the chambers 1, 2, 10, 13. The chamber 1 is evacuated with the turbomolecular pump 3, the chamber 2 with the turbomolecular pump 4. The turbomolecular pump 3 is supported by the backing pump 5. The turbomolecular pump 4 is supported by the backing pump 6.

Between the backing pumps 5, 6, a wiring harness 8 is provided, in which a diaphragm 9 is arranged.

For evacuation of the chambers 10, 13 a split flow pump 11 is provided, which is supported by a fore-pump 21. Between the backing pump 6 and the backing pump 21, an additional wiring harness 22 is arranged, which has a diaphragm 23.

Fig. 6 shows a pump assembly for a multi-chamber system with the chambers 1, 2, 10, 13, 14, 15.

The chambers 1, 2, 13, 14, 15 are evacuated by structurally identical turbomolecular pumps 3, 4, 20, 24, 25. The turbomolecular pump 3 is supported by the backing pump 5. The pumps 4, 20, 24, 25 are supported by the backing pump 6. Between the fore pump 5 and the backing pump 6, in turn, the wiring harness 8 is provided, in which the aperture 9 is arranged.

Between the backing pumps 5, 6, a wiring harness 8 is arranged, in which a diaphragm 9 is arranged.

In the chamber 14, a device for measuring the current vacuum pressure is provided.

At the pump 20, a device for measuring the current vacuum pressure is also arranged at a designated port.

In a wiring harness, a further device for measuring the gas flow is provided.

In the wiring harness 8, a device for measuring the gas flow is arranged.

reference numerals

1

chamber

2

chamber

3

Turbo molecular pump

4

Turbo molecular pump

5

backing pump

6

backing pump

7

gas inlet

8th

wiring harness

9

cover

10

chamber

11

Split flow pump

12

inlet

13

inlet

14

chamber

15

chamber

16

gas inlet

17

gas inlet

18

gas inlet

19

Split flow pump

20

Turbo molecular pump

21

backing pump

22

wiring harness

23

cover

24

Turbo molecular pump

25

Turbo molecular pump

Q

gas flow

Claims (9)

1. A pump system for evacuating gas from a plurality of chambers (1, 2, 10, 13, 14, 15) having at least four vacuum pumps (3, 4, 5, 6, 20, 21, 24, 25), wherein at least two backing pumps (5, 6, 21) and at least two turbomolecular pumps (3, 4, 20, 24, 25) are provided, wherein the chambers are connected to one another and have different levels of vacuum pressure, wherein a first turbomolecular pump is associated with a first chamber and a second turbomolecular pump is associated with a second chamber, wherein the first turbomolecular pump is supported by a first backing pump and the second turbomolecular pump is supported by a second backing pump, wherein at least one point of narrowed cross section (9) is provided in at least one connection line (8) between the at least two backing pumps (5, 6, 21) for the purpose of reducing and/or regulating a gas stream,
   and wherein a device for measuring the prevailing vacuum pressure or the gas throughput is provided at at least one point in the at least one chamber (1, 2, 10, 13, 14, 15) and/or in the at least one line portion (8) and/or at ports provided therefor on the pumps (3, 4, 20, 24, 25),
   characterised in that all the turbomolecular pumps (3, 4, 20, 24, 25) take the same structural form.
2. A pump system according to Claim 1, characterised in that the point of narrowed cross section (9) takes the form of a point of adjustably narrowed cross section (9).
3. A pump system according to one of the preceding claims, characterised in that there is provided as the point of narrowed cross section (9) an orifice, a choke valve or a gas flow regulator.
4. A pump system according to one of the preceding claims, characterised in that there is provided as the point of narrowed cross section (9) a regulated or switched valve.
5. A pump system according to one of the preceding claims, characterised in that a plurality of points of narrowed cross section (9) are connected in series and/or in parallel.
6. A pump system according to one of the preceding claims, characterised in that a higher-level process controller is provided for regulating the at least one point of narrowed cross section (9).
7. A pump system according to one of the preceding claims, characterised in that there is provided as the pump (3, 4, 20, 24, 25) a pump that is dependent on its output pressure.
8. A pump system according to one of the preceding claims, characterised in that at least one additional turbomolecular pump (11, 19) has at least two pump inlets.
9. A method for controlling a pump system having the features according to Claim 1, characterised in that a prevailing vacuum pressure or the gas throughput is measured at at least one point in the at least one chamber (1, 2, 10, 13, 14, 15) and/or in the at least one line portion (8) and/or at ports provided therefor on the pumps, and in that this at least one measured value is used for regulating the point of narrowed cross section (9).

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